Tag: Microbiology (Bacteriology and fungi)

For the growing number of people with diminished immune systems – cancer patients, transplant recipients, those with HIV/AIDS – infection by a ubiquitous mold known as Aspergillus fumigatus can be a death sentence. The fungus, which is found in the soil, on plant debris and indoor air, is easily managed by the healthy immune system. But as medical advances contribute to a growing population of people whose immune systems are weakened by disease or treatment, the opportunistic fungus poses a serious risk. Now, however, scientists may have found a master switch, an über gene, that seems to control the mold’s ability to make poison. The new finding was reported April 12 in the journal Public Library of Science Pathogens by a team led by Nancy P. Keller, a biologist from the University of Wisconsin-Madison. “There is a growing problem with medical fungi in the United States,” says Keller, a UW-Madison professor of plant pathology and medical microbiology. “Aspergillus fumigatus is among the most important.”

Like many fungi, Aspergillus fumigatus makes a variety of poisons, presumably to give the microbe a competitive advantage in the environments it inhabits. In humans with suppressed immune systems, the mold can cause a number of diseases with mortality rates of 60 percent or more. “The infection can be treated, but not easily,” Keller explains. “Once an immunocompromised individual gets any fungal disease, it’s pretty hard to treat, and the treatments themselves are often toxic. There is a 60-90 percent mortality rate with invasive aspergillosis.” Thus, knowing how the fungus makes its chemical arsenal is important and opens an avenue to devising novel treatments that can disarm the pathogen before it does its dirty work.

In fungi, there are typically many genes at work making toxins and other chemical metabolites. The genes tend to be clustered in groups on the organism’s genome. In Aspergillus fumigatus, there are as many as 22 such gene groupings. How those posses of genes are triggered and governed, however, has been a mystery. But now Keller’s group has found that a key gene known as LaeA controls at least half of those toxin-producing gene clusters, suggesting there may be a way to modulate the virulence of the deadly microbe. “We now have a very good idea that (the gene) is central to the toxic nature of the fungus,” Keller says. The LaeA gene, she believes, is like a maestro, directing the mold’s toxin-producing genes in an orchestrated chorus that, in the right host, can be fatal. Knowing this, Keller explains, “suggests that if you can find a way to regulate the activity of LeaA you might have a novel target” for new therapies to treat Aspergillus fumigatus infection. “The gene is not expressed all the time, which means there must be a signal that says ‘turn me on.'” Removing the gene from the equation, she says, may cripple the microbe’s ability to infect and sicken people. “The loss of LaeA results in a great decrease in the repertoire of secondary metabolites, which appears to impact the infection process,” making the gene an ideal prospect for new ways to fight infection.

Science Daily
May 1, 2007

Original web page at Science Daily

The first detailed images of an elusive drug target on the outer wall of bacteria may provide scientists with enough new information to aid design of novel antibiotics. The drugs are much needed to treat deadly infections initiated by Staphylococcus aureus and other bacterial pathogens. The research team, led by Natalie Strynadka, a Howard Hughes Medical Institute (HHMI) international research scholar at the University of British Columbia in Vancouver, Canada, published its findings in the journal Science. Penicillin and many newer antibiotics work by blocking a piece of the machinery bacteria use to construct their durable outer walls. Without these tough, protective coatings, bacteria die. The enzymatic machinery (known as PBP2) studied by Strynadka’s group has two main parts: One end assembles long sugar fibers; the other end stitches them together with bits of protein to form a sturdy interlocking mesh shell.

Strynadka’s team has provided a long-awaited look at the portion of the enzyme used in the first step of the biochemical pathway that initiates assembly of the sugar coating. The second step is targeted by penicillin and has been well studied. Although scientists have spent many years identifying bacterial components whose structural features might have weaknesses that can be exploited by antibiotics, progress in turning up bona fide drug targets has been slow. The cell wall enzymes in particular have tantalized scientists, Strynadka said. “The cell wall has all the hallmarks of a great drug target,” she explained. “It is essential to the survival of all bacteria. The enzymes that create the cell wall are unique to bacteria. And it is accessible; you don’t have to get the antibiotics into the cell.”

In their structural studies, the researchers focused on Staphylococcus aureus, a notorious human pathogen. An epidemic strain of the bacteria known as methicillin-resistant Staphylococcus aureus is resistant to several common antibiotics, including penicillin and amoxicillin, and is a great cause for concern among hospital infectious disease staff. Postdoctoral fellow Andrew Lovering, who is first author on the paper, hopes the group’s three-dimensional pictures of the sugar-building enzyme from S. aureus will accelerate the search for an effective weapon against the infamous superbug.

The images produced by Strynadka’s team show the enzyme frozen in place by a powerful antibiotic called moenomycin. Moenomycin has been used for decades in animal feed to promote livestock growth. Bacteria have shown very little evidence of resistance to this antibiotic so far, and scientists think related compounds may be promising candidates for use in humans. “This enzyme is an awesome target for antibiotics,” said Strynadka. “We have a totally new understanding of how the enzyme works and how a very good animal antibiotic inhibits the enzyme.” Although moenomycin is poorly absorbed by the human body, the new understanding of exactly how it interferes with bacterial enzyme function should help scientists design modified versions that are more suitable for use in people.

Understanding the structure of this enzyme should also speed up screening and design of new antibiotics, which are in constant demand as microbes continually evolve new ways to evade the drugs that researchers design to thwart them. The time it takes for bacteria to develop resistance to new antibiotics has been as short as one year for penicillin V and as long as 30 years for vancomycin. Researchers attempting to solve the structure of this enzyme have struggled to recreate its cellular environment in the laboratory. But after much tinkering with different combinations of detergent, ions, and chemical additives, Strynadka’s team was able to crystallize the enzyme so that it would diffract x-rays into a pattern that would ultimately reveal its natural structure. They then were able to repeat the feat to reveal the crystal structure of the enzyme combined with the animal antibiotic.

Their findings help reveal how the enzyme prepares to assemble the bacteria’s sugar-coating by plucking sugars from a fat-sugar package known as lipid II. The antibiotic, which is another kind of sugar-lipid, probably mimics the lipid II molecule by tucking into a fold in the enzyme and taking up the space needed to bind to lipid II, the researchers believe. “We would like to see the enzyme in a complex with its natural substrates as well as with inhibitors,” Lovering said. In the meantime, scientists now have the details of its shape and key contact points between enzyme and antibiotic. The enzyme structure is the first ever solved of a member of a family of enzymes that remove sugars from lipids and attach them to other sugars. This process is used in a wide range of biochemical reactions, including allergic responses and cell signaling in cancer.

Science Daily
March 20, 2007

Original web page at Science Daily

Researchers have unpicked why a particularly nasty form of antibiotic-resistant Staphylococcus aureus, which can strike down otherwise healthy victims outside of the hospital, is quite so vicious. The results, says Gabriela Bowden, an immunologist at Texas A&M University in Houston and an author on the study, could be used to derive new therapies to combat the troublesome bug. The study, published in this week’s Science, shows that a toxin produced by the bacterium, called Panton Valentine leukocidin (PVL), causes a lethal form of pneumonia. It also weakens the immune system and makes S. aureus boost production of proteins thought to make the bacterium stickier, allowing it to adhere more easily to skin and other tissues, boosting its infectivity.

Doctors already knew that patients with this type of pneumonia were typically infected with PVL-producing S. aureus strains. “These strains are much nastier and more aggressive than other strains,” says Mark Enright, an epidemiologist at Imperial College London, UK. But the specific role the toxin plays in making the infection so serious wasn’t known until now. Antibiotic-resistant S. aureus — often called MRSA for ‘methicillin-resistant S. aureus’ — has plagued hospitals for decades, and infection rates have been steadily climbing. According to the US Centers for Disease Control and Prevention, MRSA infections accounted for 22% of the total number of S. aureus infections in 1995. By 2004, the proportion had increased to 63%. Meanwhile, outbreaks of MRSA outside of hospital grounds are also on the rise. In the United States, 12% of clinical MRSA infections in 2003 were community-associated rather than found in hospitals. The two forms of MRSA are very different, says Bowden. Community-associated MRSA, although resistant to methicillin and a few other antibiotics including penicillin, is sensitive to many other antibiotics. Hospital-associated MRSA is resistant to most.

Although easier to tackle with drugs, community-associated MRSA can be more aggressive, felling even healthy young athletes within days of infection. These are the strains that tend to produce VPL. The bacterium can enter the bloodstream through wounds in the skin and cause a condition called ‘necrotizing pneumonia’. This affects only about 2% of S. aureus patients, but when it hits, the consequences are rapid and deadly – 75% of patients with necrotizing pneumonia die, typically within four days. “Your chances of survival are very limited if the disease has gone that far,” says Frank DeLeo, a microbiologist at the US National Institutes of Health’s Rocky Mountain Laboratories in Hamilton, Montana. Studies in cell cultures have previously shown that PVL can weaken the immune system by forming pores in immune-cell membranes, causing the cells to burst. To test the impact of the toxin, Bowden and her colleagues injected mice with purified PVL toxin. At the highest dose, roughly 90% of the mice developed signs of pneumonia and died.

The team also checked to see how much of a difference this toxin makes to an S. aureus infection, by engineering a version of MRSA without the gene for making PVL. They found that mice infected with the PVL-less strain had normal lungs and 100% survival, whereas those infected with PVL-producing bacteria had inflamed lungs and only 20% survival. The PVL toxin also boosted expression of several S. aureus proteins that could promote virulence. One of these is similar to proteins that make bacteria stickier, allowing them to colonize tissues more effectively. Another induced protein, known as protein A, is known to promote inflammation. DeLeo says the study provides an important mouse model for future work, but points out that the work was performed using a lab strain of MRSA rather than a clinical isolate. Those strain differences can be important, he says, so an important next step will be to verify these results in strains of MRSA that have been isolated from the community. Bowden says her colleagues are currently doing just that, and initial results support their findings using the lab strain.

Although several new MRSA treatments are reportedly in the pipeline, the current therapy for community-associated MRSA is antibiotic treatment. But that can’t always rescue a patient suffering from necrotizing pneumonia, cautions Enright. “It all happens so quickly,” he says. “And even if you kill the bacteria, the toxin can still go on to destroy the lung tissue.” Bowden hopes to design therapeutic antibodies that will target and disable the toxin itself, rather than focusing solely on the bacterium.

Nature
February 6, 2007

Original web page at Nature

Using cooler water to wash shell eggs during a second washing can help cool them quicker. This reduces the potential of foodborne pathogen growth both inside the eggs and on the eggshell surface, according to scientists with the Agricultural Research Service (ARS). ARS food technologists Deana Jones and Michael Musgrove in the agency’s Egg Safety and Quality Research Unit at Athens, Ga.–working with Auburn University colleagues A. Brooke Caudill and Patricia A. Curtis–looked at the frequency of Salmonella, Campylobacter, Listeria and other bacteria in eggs commercially washed in cool water. Their findings have been reported in the Journal of Food Safety. ARS is the U.S. Department of Agriculture’s chief scientific research agency.

Currently, processors who choose to produce eggs that qualify for the USDA quality shield are required to wash them in water that is at least 90°F, or 20 degrees warmer than the warmest egg entering the processing line. Furthermore, these eggs are required to be sprayed with a sanitizing rinse at least as warm as the wash-water temperature. To prevent the growth of potential foodborne pathogens associated with eggs, these warm eggs must then be cooled quickly for storage. To ensure the eggs are safe for human consumption, USDA requires that all shell eggs be stored at 45°F or lower after processing. That’s because Salmonella–the organism most often associated with foodborne disease and eggs–and other bacteria don’t grow well at refrigerated temperatures. Getting to the target temperature quickly can make a big difference.

The researchers tested three water-temperature schemes in commercial dual-washer systems: water at 120°F for both washers; water at 120°F for the first wash and 75°F for the second; and both washers at 75°F. They found that using a warm temperature in the first washer, followed by a cool temperature in the second one, could provide the greatest benefit in terms of both reduced egg temperature and acceptable microbial levels. While Salmonella, Campylobacter and Listeria were all detected in shell emulsion and wash-water samples from cool-water washing treatments, none were detected in the egg contents throughout the storage period of eight weeks.

Science Daily Health & Medicine
January 23, 2007

Original web page at Science Daily Health & Medicine

In a study published in Science (24 November, 2006), an international consortium from the Max-Planck Society, Wellcome Trust Institutes in Britain and Vietnam, and the Institut Pasteur in France have elucidated the evolutionary history of Salmonella typhi (Typhi). Typhi is the cause of typhoid fever, a disease that sickens 21 million people and kills 200,000 worldwide every year. The results indicate that asymptomatic carriers played an essential role in the evolution and global transmission of Typhi. The rediscovered importance of the carrier state predicts that treatment of acute disease, including vaccination, will not suffice to eradicate this malady. The results also illuminate patterns leading to antibiotic resistance after the indiscriminate use of antibiotics. Fluoroquinolone treatment in southern Asia over two decades has resulted in the emergence of multiple, independent nalidixic acid-resistant mutants, of which one group, H58, has multiplied dramatically and spread globally. The prevalence of these bacteria hampers medical cure of clinical disease via antibiotics.

Typhoid fever remains a major health problem in the developing world and continues to cause disease in Europe and on the american continent. The evolutionary history and population structure of Typhi were poorly understood, partly because these bacteria show little genetic diversity. Now a team led by Mark Achtman and Philippe Roumagnac from the Max Planck Institute for Infection Biology, Berlin, has applied population genetic experience from prior work with Yersinia pestis, Escherichia coli, Helicobacter pylori and Neisseria meningitidis to provide novel insights into the evolution of this pathogen. The team combined its resources to assemble for the first time a globally representative collection of 105 strains of Typhi and investigated the sequence diversity within 90,000 base pairs per strain. Eighty-eight informative sequence differences were detected, showing that the population structure has evolved over the last 10,000 to 43,000 years. Amazingly, the ancestral strain continues to exist today, as do many of its direct descendents, indicating a neutral population structure, whereas normally selective forces lead to extinction of intermediate genotypes. Furthermore, these bacteria are distributed globally, demonstrating that Typhi has spread inter-continentally on multiple occasions.

The authors propose that the unusual population structure of Typhi reflects long-term carriage by asymptomatic carriers, who reached public notoriety at the beginning of the 20th century with “Mr. N the milker” in England and Typhoid Mary (Mary Mallon) in the U.S.A. These individuals infected 100s of people over the decades while they worked in the food production industry. Healthy carriers may have allowed Typhi to survive in hunter-gatherer populations prior to the Neolithic expansion of city states and facilitated its intercontinental spread. Healthy carriers are also consistent with the observation that individual genotypes of Typhi persist for many decades within each country.

Increasing resistance to antibiotics in recent decades has hampered efforts of clinicians to cure typhoid fever. The indiscriminate use of fluoroquinolones, which is a cost-effective, standard treatment for typhoid fever, has been accompanied by a frightening increase in the numbers of resistant Typhi. Investigations of a large strain collection from southern Asia revealed that many different genotypes independently acquired resistance to nalidixic acid, a quinolone. One of these genotypes, H58, has become predominant throughout southern Asia and has even spread to Africa. In Vietnam, up to 95% of Typhi are now resistant to nalidixic acid and many other antibiotics. Although these cases can still be treated with newer antibiotics, those antibiotics are much more expensive than standard fluoroquinolones, which raises the cost of medical treatment. Furthermore, it is likely that Typhi will develop resistance to these antibiotics as well.

The combination of these investigations raises problems for public health measures. Indiscriminate antibiotic usage results in real-time evolution of bacteria that resist treatment. Furthermore, the healthy carrier state provides a safe reservoir for these bacteria which allows them to evade short-term antibiotic treatment and vaccination, indicating that typhoid fever will remain a major health problem for the foreseeable future.

Science Daily
December 19, 2006

Original web page at Science Daily

Ear infections are among the most common diseases seen in pediatric practice. They have generally been considered bacterial diseases and are therefore usually treated with antibiotics. New research, published in the December 15 issue of Clinical Infectious Diseases and currently available online, provides evidence that viruses are found in a great many ear infection cases and may complicate treatment. The researchers used a variety of laboratory techniques to identify the pathogen that caused ear infections, known clinically as acute otitis media (AOM), in 79 young children. They found bacteria in 92 percent of the cases, viruses in 70 percent, and both bacteria and viruses in 66 percent. According to Aino Ruohola, MD, PhD, from the Turku University Hospital in Finland and lead author of the study, “the major finding of the study is that acute otitis media is a coinfection of bacteria and viruses in the great majority of children. This is actually logical since acute otitis media is virtually always connected to viral respiratory infection.”

Antibiotics, which are effective against the bacteria that cause AOM, have no effect on the viruses found in AOM infections. Therefore, the standard treatment for AOM–antibiotics–can be, at best, partially effective in the majority of cases. “Based on this and previous research,” said Dr. Ruohola, “it is possible that viruses cause a considerable proportion of clinical treatment failures. Thus, in these cases a new antibiotic is not necessarily the best choice although bacteria resistant to common antibiotics are wide-spread.” The good news is that many cases of AOM recover spontaneously without antibiotic treatment, a fact that has led the American Academy of Pediatrics and the American Academy of Family Physicians to recommend withholding antibiotic treatment in mild AOM cases.

In an accompanying editorial, Tasnee Chonmaitree, MD, from the University of Texas Medical Branch, notes that studies of AOM have shown that viruses may impair antibiotic efficacy by several mechanisms. “Further studies,” she writes, “are required to determine the effect of combined bacterial and viral infections of the respiratory tract in adults and children.” She says that if this joint bacterial/viral infection concept also applies to respiratory diseases such as sinusitis and pneumonia, then the expectation of antibiotic efficacy in these diseases needs to be adjusted.

Science Daily
November 21, 2006

Original web page at Science Daily

The mode of transmission of Helicobacter pylori infection is poorly characterized. In northern California, 2,752 household members were tested for H. pylori infection in serum or stool at a baseline visit and 3 months later. Among 1,752 person considered uninfected at baseline, 30 new infections (7 definite, 7 probable, and 16 possible) occurred, for an annual incidence of 7% overall and 21% in children <2 years of age. Exposure to an infected household member with gastroenteritis was associated with a 4.8-fold (95% confidence interval [CI] 1.4–17.1) increased risk for definite or probable new infection, with vomiting a greater risk factor (adjusted odds ratio [AOR] 6.3, CI 1.6–24.5) than diarrhea only (AOR 3.0, p = 0.65). Of probable or definite new infections, 75% were attributable to exposure to an infected person with gastroenteritis. Exposure to an H. pylori–infected person with gastroenteritis, particularly vomiting, markedly increased risk for new infection. Helicobacter pylori infects at least 50% of the world’s population. Infection occurs in early life. Because acute infection invariably passes undetected, however, the precise age of acquisition is unknown. In industrialized countries, infection rates are declining rapidly, but high rates of infection persist among disadvantaged and immigrant populations. The mechanisms of H. pylori transmission are incompletely characterized. Person-to-person transmission is most commonly implicated with fecal/oral, oral/oral, or gastric/oral pathways; each has supportive biologic as well as epidemiologic evidence. Like many common gastrointestinal infections, infection is associated with conditions of crowding and poor hygiene and with intrafamilial clustering. The organism has been recovered most reliably from vomitus and from stools during rapid gastrointestinal transit. These findings raise the hypothesis that gastroenteritis episodes provide the opportunity for H. pylori transmission. Household transmission of gastroenteritis is common in the United States, particularly in homes with small children. If H. pylori is transmitted person to person, one might expect rates of new infection to be elevated after exposure to persons with H. pylori–infected cases of gastroenteritis. To explore whether diarrhea or vomiting contributes to disease transmission, we monitored northern Californian households experiencing gastroenteritis for new H. pylori infections and evaluated the contributions of household H. pylori infection and gastroenteritis to new infection. We were also interested in whether symptoms of new infection could be identified. Emerging Infectious Diseases
November 6, 2006

Original web page at Emerging Infectious Diseases

Humans catch many diseases from animals—so-called zoonotic infections. Often, these occur in limited regions of the world. However, one—leptospirosis—occurs in temperate and tropical climates, and in urban and rural settings, making it the most widespread zoonotic disease. Leptospirosis is caused by Leptospira, a large group of closely related spiral-shaped bacteria that live in both domestic animals (for example, cattle) and wild animals (particularly rats). Millions of humans become infected each year with leptospires through close contact with water, food, or soil contaminated with the urine of infected animals—swimming or wading in contaminated water is particularly hazardous. Some infected people have no symptoms; others develop a flu-like disease that clears up within a few days. However, in 5%–10% of infected people, the disease progresses to a second, sometimes fatal phase. This is usually characterized by jaundice, kidney problems, and an enlarged spleen (it’s then called Weil disease) but can also involve the lungs (pulmonary leptospirosis). Leptospirosis can be successfully treated with antibiotics if treatment is started soon after infection.

In a recent study in the Peruvian Amazon, half of the people visiting urban hospitals and rural health posts with acute fever had antibodies in their blood to Leptospira, suggesting that they had acute leptospirosis. However, only patients living in urban areas developed pulmonary leptospirosis. In this study, the researchers tested the hypothesis that this pattern arose because more virulent types of Leptospira were present at higher levels in urban environmental surface water than in rural water sources. Between June 2003 and March 2004, the researchers isolated strains of Leptospira from patients with acute fever who visited a hospital in the town of Iquitos or clinics in nearby villages. Early in 2004, they also collected a large number of different water samples from an urban slum in Iquitos and from a nearby rural community. They measured the concentrations of Leptospira in these samples by using a molecular technique called real-time PCR (polymerase chain reaction) to detect and quantify a type of RNA found only in disease-causing Leptospira. They also identified which specific Leptospira were present in the water samples and the patient samples by sequencing this RNA. The researchers found that leptospires were present in both urban and rural water samples (particularly in samples from gutters and puddles in the urban slum’s market area) but that their concentration in the positive water samples from the urban sites was 20 times that in the positive samples from the rural sites. Furthermore, the distribution of different Leptospira types isolated from the patients mirrored that of the bacteria in the local environment. So, one particular type of Leptospira interrogans known as icterohaemorrhagiae—the leptospire most commonly associated with severe leptospirosis in the patients—was found more often in the urban water samples than in the rural ones. Finally, the researchers discovered a new group of Leptospira in the rural environment. This group may contain one or several new species of Leptospira but whether any of them causes human disease is unknown.

These results support the researchers’ hypothesis that pulmonary leptospirosis in urban areas of the Peruvian Amazon is associated with high environmental levels of specific disease-causing leptospires. The researchers were able to discover this link only by using molecular techniques—this sort of study is impossible with traditional bacteriological techniques because Leptospira are hard to grow in the laboratory and cannot be isolated efficiently from environmental water sources. Different types can’t be identified using a microscope. The researchers’ findings need to be validated in other settings, but they suggest that environmental interventions such as reducing sources of standing water and clearing away garbage in urban areas might reduce the number of cases of severe leptospirosis. The distribution of different Leptospira types also suggests that whereas rats may be the main disease reservoir in towns, cattle, pigs, and bats may be more important in rural settings in Peru and presumably elsewhere. Overall, this new information, together with the availability of molecular methods for rapid clinical diagnosis and environmental risk assessment, should aid attempts to control leptospirosis around the world.

PLoS Medicine
September 12, 2006

Original web page at PLoS Medicine

In Africa’s ongoing struggle against tuberculosis, a group of scientists and industry representatives are now exploring a plan to introduce copper pipes, doorknobs and work surfaces to the country’s waterways and clinics. The metal’s known antibiotic activity, they say, could provide a simple way to help fight the deadly infection. Past research has shown that copper has strong anti-bacterial properties against worrisome pathogens such as the superbug MRSA. Whereas all cells need a bit of copper to grow, an excess can overwhelm a cell’s mechanism to bind to the metal, effectively killing it from over-exertion. Recent work by scientists from the University of Southampton, UK, showed that MRSA was unable to survive on copper alloy surfaces for longer than 90 minutes. Recent research from a team in South Africa shows that copper also wipes out the bacterium responsible for tuberculosis (TB) — one of Africa’s biggest killers. The researchers, from the University of Stellenbosch, presented their data last month at a meeting of the International Federation of Infection Control (IFIC), held in Stellenbosch from 3-5 July.

Laboratory tests showed that after 48 hours of exposure, pure copper and five of its alloys could inhibit growth in TB bacteria, including strains resistant to usual drugs, with no signs of regrowth over the study period of 15 days. TB is an extremely resilient bug, says Shaheen Mehtar, who headed the research. It often grows back on, say, a stainless-steel surface that has been cleaned with disinfectant, after just a couple of days. “So the copper results are promising,” she says. Such results have spurred ideas to make hospital surfaces from copper alloys, to help keep background levels of infectious bacteria down. A trial is currently being run by Takeshi Sasahara at the Japanese Kitasato University Hospital. Sasahara says that the simple change has resulted in a “consistent and significant reduction” in surface contamination by Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. Whether it is the best way to keep bugs in check, however, is still up for debate, he says.

Ben Marais, a paediatrician at Stellenbosch University, notes that it can take up to 6 hours for copper to kill bacteria, so there remains a window of opportunity when infection can occur. And TB is transmitted by the inhalation of airborne bugs, so self-sanitizing surfaces might not have as big an impact as hoped with that disease. But, he adds, reducing the chance of infection in a country such as South Africa, where an estimated 5.3 million people live with HIV and are particularly vulnerable to opportunistic infections, “may be of great benefit”. Gerhard Offringa, from the South African Water Research Commission, says that full water treatment systems are obviously better than copper alone, as they are designed to address a number of potential problems with the water supply. But he adds that “It’s good to have a back-up system. Rural water-treatment systems are not always correctly monitored. Here copper would be a good additional barrier.”

Representatives from the International Copper Development Association, along with African industry participants, engineers and faculty from the Stellenbosch University, gathered at a workshop in Johannesburg immediately after the IFIC conference to plan how best to use copper to fight disease in Africa. Project manager Grant Mackintosh says they are still at the planning stage, but adds that at least one trial will begin before the end of the year at the Kayamandi township clinic outside Stellenbosch. “Copper is not the answer for everything,” says Mackintosh. “But what we are looking at here is copper’s role in making a significant contribution.”

Nature
August 29, 2006

Original web page at Nature

A new study published this month by a Saint Louis University vaccine researcher scrutinizes what in the future could be an alternative to the presently available anthrax vaccine. This new type of anthrax vaccine produced the immune response doctors were looking for, according to peer-reviewed research published in Vaccine. In its first human testing, the vaccine was given to 100 volunteers at four sites around the United States, said Geoffrey Gorse, M.D., a Saint Louis University researcher who was the main author of the paper. “This type of research, five years after 9/11, continues to be very important to pursue,” Gorse said. “We need a better vaccine to help protect people from anthrax infection, whether the vaccine is given before or soon after exposure to anthrax spores.”

Gorse said the study was able to answer some important questions about this candidate vaccine. “We were able to demonstrate in this study that the investigational anthrax vaccine produced an immune response that justifies further testing in larger studies,” he said. “We’ll be using this data to help design strategies for testing of this vaccine in the future.” Gorse indicated that the investigational vaccine, made by VaxGen Inc., demonstrated a clear relationship between the amount of vaccine administered and the subsequent immune response. The study was designed to evaluate the safety and immunogenicity of escalating doses of the new vaccine. A total of 100 healthy adults were randomized to receive either one of four different vaccine formulations, or AVA, the anthrax vaccine currently licensed for use in the United States. All vaccinations were administered intramuscularly.

Science Daily
August 29, 2006

Original web page at Science Daily

Detecting ß-lactamase–mediated carbapenem resistance among Klebsiella pneumoniae isolates and other Enterobacteriaceae is an emerging problem. The recognition of carbapenem-resistant K. pneumoniae continues to challenge automated susceptibility systems.
Carbapenem resistance among the Enterobacteriaceae is emerging in the United States, particularly on the East Coast. Resistance to the most widely used carbapenems, i.e., imipenem and meropenem, can be mediated by a variety of mechanisms, including ß-lactamases, porin changes, and changes in penicillin-binding proteins. KPC enzymes are among the most common ß-lactamases mediating carbapenem resistance among isolates of Enterobacteriaceae. KPC enzymes are class A ß-lactamases that mediate resistance to extended-spectrum cephalosporins in addition to carbapenems; these ß-lactamases are usually plasmid encoded.

Clinical microbiology laboratories have often found it difficult to achieve accurate susceptibility testing results for carbapenem drugs. Early studies documented false resistance to imipenem due to degradation of the drug; later studies with the VITEK system (bioMérieux, Durham, NC, USA) demonstrated false resistance, specifically with Proteus mirabilis. Several recent proficiency testing studies have shown problems of both false resistance and false susceptibility with imipenem and meropenem among a variety of enteric species. Even quality control measures fail to detect all false resistance problems.

Yigit and colleagues described the KPC-1 ß-lactamase in 2001. The ß-lactamase was identified in an imipenem-resistant isolate of Klebsiella pneumoniae from the United States. Subsequently, 3 additional KPC-type ß-lactamases have been described from Salmonella, K. oxytoca, Enterobacter cloacae, and other K. pneumoniae; these differ in amino acid sequence from each other, typically by 1 or 2 amino acids. Bratu and colleagues reported false-susceptible results for K. pneumoniae isolates with the MicroScan WalkAway system (Dade MicroScan, Inc., West Sacramento, CA, USA), which were attributed in part to low inoculum size. Similar problems with false-susceptible results were noted with the VITEK system. The goal of this study was to conduct a rapid assessment of currently available antimicrobial susceptibility testing methods to determine whether these methods were capable of consistently detecting KPC-mediated carbapenem resistance in fresh clinical isolates of K. pneumoniae.

Emerging Infectious Diseases
August 14, 2006

Original web page at Emerging Infectious Diseases

Direct evidence of bacterial biofilms has been found on the middle ear tissue of children who suffer from chronic ear infections, according to a study published today in the Journal of the American Medical Association (JAMA) by researchers from the Allegheny Singer Research Institute (ASRI) at Allegheny General Hospital in Pittsburgh, the Medical College of Wisconsin and Children’s Hospital of Wisconsin in Milwaukee.

Biofilms are antibiotic resistant colonizations of bacteria that attach to surfaces and form a slime-like barrier that acts as a formidable defense mechanism, protecting the bacteria from eradication. The discovery of biofilms in the setting of chronic otitis media represents a landmark evolution in the medical community’s understanding about a disease that afflicts millions of children world-wide each year and further endorses the emerging biofilm paradigm of chronic infectious disease, said Garth Ehrlich, Ph.D., principal investigator and executive director of the ASRI Center for Genomic Sciences. Over the past ten years, Dr. Ehrlich and J. Christopher Post, M.D., Ph.D., FACS, an Allegheny General Hospital pediatric ear specialist and medical director of the Center for Genomic Sciences, have pioneered the biofilm theory to explain the persistence of chronic ear infections. In 2002, the team published in JAMA (Apr 2002; 287: 1710 – 1715) the first animal evidence of biofilms in the middle ear, setting the stage for the current clinical investigation.

According to co-investigator Joseph E. Kerschner M.D., “Today’s study completely alters the concept about how physicians should approach the treatment of children with otitis media. This historic finding sheds new light on the decreasing efficacy of antibiotics in treating kids with ear infections and has serious implications about the future direction of therapeutic research.” Dr. Kerschner is associate professor of otolaryngology at the Medical College and chief of pediatric otolaryngology at the College and Children’s Hospital of Wisconsin, a major teaching affiliate of the College. “Nearly all of the children in our study who suffered from chronic otitis media tested positive for biofilms in the middle ear, even those who were asymptomatic.

It appears that in many cases recurrent disease stems not from re-infection as was previously thought and which forms the basis for conventional treatment, but from a persistent biofilm,” Ehrlich said. “Given that bacteria living in biofilms are metabolically resistant to antibiotics, this study makes a definitive, scientifically-based statement against the use of these drugs to treat children with chronic ear infections. It simply does not help the child and increases the risk of breeding more resistant strains of bacteria,” he said. Characterized as either an acute or chronic disease, otitis media (OM) is the most common illness for which children visit a physician, receive antibiotics or undergo surgery in the United States. There are two subtypes of chronic OM: recurrent OM (ROM) is diagnosed when children suffer repeated infections over a span of time and during which clinical evidence of the disease resolves between episodes, and chronic OM with effusion is diagnosed when children have persistent fluid in the ears that lasts for months in the absence of any other symptoms except conductive hearing loss.

Though antibiotics have proven to be effective for children with acute OM where biofilms have not yet formed, those with chronic disease typically benefit little from the drugs and more so from myringotomy, a surgical procedure in which small tubes are placed in the eardrum to continuously drain infectious fluid (called effusion). Working with Dr. Kerschner, Drs. Ehrlich and Post obtained middle ear mucosa – or membrane tissue – biopsies from children undergoing myringotomy for OM with effusion (OME) and ROM. The team gathered uninfected mucosa biopsies from children and adults undergoing cochlear implantation as a control.

Using advanced confocal laser scanning microscopy, three dimensional images were obtained of the biopsies and evaluated for biofilm morphology using generic stains and species-specific probes for Haemophilus influenzae, Streptococcus pneumoniae and Moraxella catarrhalis by Luanne Hall Stoodley, Ph.D. and her ASRI colleagues. Effusions, when present, were also evaluated for evidence of pathogen specific nucleic acid sequences (indicating presence of live bacteria). The study found mucosal biofilms in the middle ears of 46/50 children (92%) with OME and ROM. Biofilms were not observed in eight control middle ear mucosa specimens obtained from cochlear implant patients.

“Our findings demonstrate what we have suspected for years, that children with chronic otitis media have biofilms in their middle ears. Healthy children do not. The idea of treating recurrent disease with antibiotics therefore is not supported by the scientific evidence,” Dr. Post said. “Chronic middle ear infection is not the result of a sterile inflammatory process, but an indolent bacterial disease. Understanding that, we can now begin to explore more effective treatments for it.” Dr. Post said future therapies may be medical, technological or biological in nature, including the use of probiotics – an approach in which children are deliberately populated – but not infected – with good bacteria that prevent the formation of biofilms. In an ongoing study at the University of Florida, researchers are inoculating children against cavities using a bacteria that sets up house in their teeth where plaque biofilms usually grow.

“The idea with chronic middle ear infections would be to engineer a bacteria that could occupy the nasopharynx but not cause recurring infection,” Dr. Post said. “Until something new comes along, however, placement of ear tubes to provide children with symptomatic relief will still be necessary and recommended. Antibiotics should also continue to be prescribed for acute otitis media to help prevent potentially serious complications, such as mastoiditis and meningitis,” Dr. Kerschner said.

Science Daily
August 1, 2006

Original web page at Science Daily

A newly discovered receptor in a strain of Escherichia coli can be blocked to avert infection, a finding that might aid in developing better therapies to treat bacterial infections resulting in food poisoning, diarrhea or plague. Dr. Vanessa Sperandio, assistant professor of microbiology, led a research team that included graduate student David T. Hughes in discovering a receptor in a strain of Escherichia coli can be blocked to avert infection, a finding that might aid in developing new therapies to treat bacterial infections resulting in food poisoning, diarrhea or plague. Researchers at UT Southwestern Medical Center are the first to identify the receptor, known as QseC, used by a diarrhea-causing strain of E coli to receive signals from human flora and hormones in the intestine and express virulence genes to initiate infection.

In a study made available online this week and in an upcoming issue of the Proceedings of the National Academy of Sciences, researchers describe how they used phentolamine, an alpha blocker drug used to treat hypertension, to successfully impede signaling to the receptor. Without such signals, bacteria then pass blindly through the digestive tract without infecting cells. “This receptor is found in many pathogens, so we can use this knowledge to design specific antagonists to block bacterial infections,” said Dr. Vanessa Sperandio, senior author of the study and assistant professor of microbiology at UT Southwestern.

Prior research by Dr. Sperandio found that when a person ingests the more virulent enterohemorrhagic E coli, or EHEC — which is usually transmitted through contaminated food such as raw meat — it travels peacefully through the digestive tract until reaching the intestine. There, however, chemicals produced by the friendly gastrointestinal microbial flora and the human hormones epinephrine and norepinephrine alert the bacteria to its location. This cellular cross talk triggers a cascade of genetic activations prompting EHEC to colonize and translocate toxins into cells, altering the makeup of the cells and robbing the body of nutrients. An infected person may develop bloody diarrhea or even hemolytic uremic syndrome, which can cause death in immune-weakened people, the elderly and young children. The new study identifies QseC as the specific receptor by which EHEC senses the signals. When the receptor binds to signaling molecules, the bacterium can infect cells.

Researchers tested the capacity of adrenergic antagonists, drugs such as alpha and beta blockers, to disrupt the receptor’s sensing ability. They found that phentolamine binds to the QseC receptor and occupies the pocket that the receptor would use to recognize the host epinephrine and norepinephrine signals — thus blocking the QseC receptor from sensing the signals and preventing it from being able to express its virulence genes in cells. This knowledge opens the door to further understanding of the signaling processes between microbes and humans and to the development of novel treatments of bacterial infections with antagonists to these signals, Dr. Sperandio said.

New therapies are important because treating some bacterial infections with conventional antibiotics can cause the release of more toxins and may worsen disease outcome. That importance is magnified because of the QseC receptor’s existence in other types of bacteria, including, Shigella, which causes dysentery; Salmonella, which causes food poisoning and gastroenteritis; and Yersinia, which causes bubonic plague. Those are all emerging infectious diseases that afflict thousands of people each year in the United States and worldwide, according to the Centers for Disease Control and Prevention. “Overuse of antibiotics has led bacteria to develop resistance to antibiotics, so a novel type of therapy is needed,” Dr. Sperandio said.

Science Daily
July 18, 2006

Original web page at Science Daily

The bacterium that causes bubonic plague would seem unlikely to help medical scientists, but researchers at UT Southwestern Medical Center have harnessed it to uncover a new regulatory mechanism that inhibits the immune system. Three species of the Yersinia bacteria, known to cause plague and gastroenteritis, contain a small molecule, called a virulence factor, that the researchers have found modifies host enzymes critical to normal functioning. “This type of modification has never been seen in cells and presents a new paradigm for how cells may regulate signaling,” said Dr. Kim Orth, assistant professor of molecular biology and senior author of the study appearing in the May 26 edition of Science.

“Yersinia is a nasty pathogen that uses an arsenal of virulence factors to cause disease,” she said.

When a cell is infected with a bacterial pathogen, it activates a chain of reactions involving enzymes. One enzyme adds a group of atoms containing phosphorus – called a phosphate group – to another enzyme, a process called phosphorylation, which spurs that enzyme to add a phosphate group to yet another enzyme, and so on. These “cascading” events trigger an appropriate immune response. Yersinia, however, has the ability to prevent its host from mounting the response, enabling the bacteria to survive and multiply.

The researchers found that one of the Yersinia outer proteins, called YopJ, cripples these cascades by adding a small molecule called an acetyl group to two key sites on a host enzyme where the phosphate groups are usually added. Because the host’s enzymes are modified by acetyl groups, they can no longer be activated by phosphate groups, and the enzymatic cascade critical for triggering an innate immune response is not activated. The internal signaling that YopJ affects is common to many species, from yeast to mammals. In addition, other pathogens that attack animals and plants use proteins that are similar to YopJ.

The research is not geared toward finding a cure for plague, which affects about a dozen people in the United States a year and is treatable with antibiotics. Instead, the scientists are working to find out how the pathogen disrupts the immune system and to understand the machinery critical for stimulating an immune response. “There are many virulence factors used by bacterial pathogens to co-opt the host signaling molecules,” Dr. Orth said. “These virulence factors affect central signaling machinery, and we want to understand how they are doing it.” Understanding the relationship between the pathogens and the hosts will help researchers uncover critical steps in how host cells normally operate, Dr. Orth said. “The next step is to see whether the addition of acetyl groups to key sites on enzymes during cellular signaling is normal for animal and plant cells, and if so, under what circumstances,” said Dr. Orth.

Science Daily
July 3, 2006

Original web page at Science Daily

Our skin not only serves as a physical barrier against infection but skin cells themselves can mount an immune response to kill invading microbes by producing antimicrobial polypeptides (AMPs). As overt infection in the skin is a rare event, researchers have theorized that AMPs must not only help fight infection, but play a role in preventing infection from developing in the first place. In a study appearing online on June 15 in advance of print publication in the July issue of the Journal of Clinical Investigation, Ole Sorensen and colleagues from Lund University, Sweden, investigated what triggers AMP production in human skin. Interestingly, they found that AMPs were produced in human skin after sterile wounding of the skin surface, illustrating that exposure to invading microbes is not the sole trigger for the immune response in skin.

The authors went on to show that AMP was produced through activation of the epidermal growth factor receptor (EGFR), which is known to play a role in the normal wound-healing process. The authors found that the antibacterial activity of the skin against the potential skin pathogen Staphylococcus aureus was increased by activation of EGFR, and that the concentrations of AMPs in the epidermis of wounded skin exceeded those necessary to suppress or prevent the growth of foreign microbes. The results of this study demonstrate that wounding of the skin alone, without the presence of microbes, is sufficient to activate defense mechanisms in the skin that can prevent microbial growth and related harmful skin infections.

Science Daily
July 3, 2006

Original web page at Science Daily

Not all bacteria are bad. In fact, beneficial microbes could represent the future of medicine, with the potential to treat a variety of diseases in humans and animals from diarrhea and eczema to gum disease and autoimmune disorders, according to a report released by the American Academy of Microbiology, Probiotic Microbes. “Theoretically, beneficial microorganisms could be used to treat a range of clinical conditions that have been linked to pathogens, including gastrointestinal problems like irritable bowel syndrome and inflammatory bowel disease, oral diseases like tooth decay and periodontal disease, and various other infections, including vaginal infections and possibly skin infections. Probiotics could also conceivably be put to use in preventing disease or thwarting autoimmune disorders. A number of these possibilities are being explored in research labs and hospitals around the world,” says Richard Walker of the Food and Drug Administration, a co-chair of the steering committee that produced the report.

Probiotics can help prevent and treat disease through a number of mechanisms. One way is by interacting directly with the disease-causing microbes, making it harder for them to cause disease. An example of this is the ingestion of probiotic bacteria to prevent or treat diarrhea. The organisms help reinforce the natural bacterial barrier that exists on the lining of the digestive tract providing additional protection against pathogenic organisms that can cause diarrhea. “Several probiotics have been shown to shorten the duration of acute watery diarrhea caused by rotavirus in children. Other causes of diarrhea may also be addressed through probiotics,” says Carol Wells of the University of Minnesota, a member of the steering committee.

Another example of microbe-microbe interaction in probiotics is a phenomenon known as “competitive exclusion” in which beneficial microbes directly compete with disease-causing microbes for food and other resources, eventually crowding them out. One potential application of competitive exclusion would be colonizing the mouth with beneficial bacteria to prevent the growth of bacteria that cause cavities and gum disease. Probiotics also help prevent disease by interacting with and strengthening the immune system.”Exposure to commensal organisms is necessary for the appropriate development of both the innate and acquired immune systems. Once established, probiotic organisms interact with these immune defenses, possibly changing the nature of the immune response to other antigens, including commensal and pathogenic organisms,” says Walker.

The report is the outcome of a colloquium convened by the American Academy of Microbiology in November 2005 to discuss the current state of knowledge regarding probiotics. Participants with expertise in microbiology, medicine, periodontics, animal science, immunology, nutrition and other fields met to discuss a variety of issues associated with the field of probiotics. In addition to providing an overview of the current state of and potential for probiotic research, the report also offers specific recommendations to help advance the field. In addition to those listed above, some other potential future applications of probiotics identified in the report include treating antibiotic-resistant infections, encouraging weight gain in newborns and children with AIDS, reducing the incidence of kidney stones, and reducing the recurrence of bladder tumors.

Science Daily
July 3, 2006

Original web page at Science Daily