Toxigenic C. difficile Resides Harmlessly in Infants, Poses Risk to Adults
WASHINGTON, DC – December 3, 2013 – Infants and toddlers frequently carry toxigenic Clostridium difficile, usually with no harm to themselves, but can serve as a reservoir and spread the bacteria to adults in whom it can cause severe disease, according to a study by a team of Swedish researchers published ahead of print in the Journal of Clinical Microbiology.
New Technique Identifies Pathogens in Patient Samples Faster, In Great Detail
WASHINGTON, DC – December 2, 2013 – A team of Danish investigators has shown how to identify pathogens faster, directly from clinical samples. The research, published online ahead of print in the Journal of Clinical Microbiology appears in the journal’s January 2014 issue.
Probiotics Reduce Piglet Pathogens
WASHINGTON, DC – November 17, 2013 – Piglets fed probiotic Enterococcus faecium showed reduced numbers of potentially pathogenic Escherichia coli strains in their intestines, according to a team of German researchers. The research is important, because in 2006 the European Union prohibited the feeding of antibiotics to livestock as growth promoters. Therefore, the research team sought to investigate whether probiotics could substitute for antibiotics, by reducing pathogen populations in the intestines, says first author Carmen Bednorz of Freie Universitat Berlin, Germany. The study was published ahead of print in the journal Applied and Environmental Microbiology.
“We found a clear reduction of E. coli strains possessing typical genes for extra-intestinal pathogenic E. coli (ExPEC),” says Bednorz. The reduction was particularly noticeable in strains that adhere to the intestinal mucosa (and less so in the feces), which was “very interesting,” she says, because “ExPEC typically harbor a lot of adhesion genes that promote colonization of the mucosa.”
Antimicrobials are thought to promote growth in industrially grown livestock because without them, the rationale goes, in such close quarters, a surfeit of pathogens would slow growth. “Our data suggest that the feeding of probiotics could substitute for antimicrobials as growth promoters,” says Bednorz. “This could help to reduce the burden of antimicrobial resistance,” she adds.
In previous studies, the working groups from the Institute of Microbiology and Epizootics at Freie Universitat Berlin found that feeding E. faecium probiotic did not change the general swine intestinal microbiota, but reduced infections by Chlamydia spp. and pathogenic E. coli, according to the report.
In the study, Bednorz and her collaborators compared piglets fed with E. faecium to those in a control group. They collected more than 1,400 samples of E. coli from piglets of different ages, and from different parts of the intestine.
While a number of strains of E. coli are pathogenic, non-pathogenic E. coli “contributes to the maintenance of the microbial gut balance,” according to the report. These were relatively unaffected by the feeding of E. faecium, which “did not influence the overall intestinal E. coli diversity, corroborating previous data,” according to the report. Thus, the researchers conclude, the results suggest that E. faecium inhibits pathogenic E. coli from becoming attached to the intestinal mucosa.
The article can be found online at http://bit.ly/asmtip1113b.
“Applied and Environmental Microbiology is a publication of the American Society for Microbiology (ASM). The ASM is the largest single life science society, composed of over 39,000 scientists and health professionals. Its mission is to advance the microbiological sciences as a vehicle for understanding life processes and to apply and communicate this knowledge for the improvement of health and environmental and economic well-being worldwide.”
New Method to Diagnose Sepsis is Faster, Cheaper
WASHINGTON, DC – November 15, 2013 – A new method could cut hours off the time it takes to diagnose blood infections while also eliminating the need for complicated manual processing and expensive equipment, according to a report to be published in mBio®, the online open-access journal of the American Society for Microbiology, on November 19. The method combines a selective lysis step in which blood cells in the sample are destroyed, a centrifugation step to collect any bacteria or fungi in the sample, and a fluorescence step that analyzes the particular fingerprint of any pathogens present in the sample. Tests show the method correctly identifies the species of bacteria or fungi in 96.5 % of positive blood culture samples, crucial information for doctors to provide the appropriate drugs for their patients.
"The primary benefit of getting a rapid identification is making sure the patient is on the right [antibiotic] therapy and to quickly make any needed adjustments to the initial therapy," says co-author John Walsh of bioMérieux, Inc. in Durham, North Carolina. Patients with bloodstream infections are usually in very serious condition, says Walsh, and faster identification of the organism causing the infection can help get patients on the most effective antibiotics faster and save lives. Proper diagnosis is also important from the perspective of antibiotic stewardship: using more appropriate, targeted antibiotics reduces the risk of contributing to the spread of resistance to broad-spectrum antibiotics.
Walsh says the current standard approach to diagnosing bloodstream infections, Gram staining and overnight sub-culture followed by phenotypic ID tests, have limitations that can prevent timely treatment. Gram staining provides early, low level information about the type of microorganism present, but it sometimes takes hours to deliver a result, and technicians can make mistakes in the process that provide misleading results. Other more specific identification methods are also available for diagnosis, but they can take at least a day or two to produce results and many require expensive equipment.
In the technique developed by Walsh et al., a sample of positive blood culture is treated with lysis buffer to "pop" the blood cells, then transferred to a specialized optical tube. The tube is centrifuged, which drives bacteria or fungi, which are denser than the solution, down through a liquid density cushion to form a pellet at the bottom of the tube.
Then comes the intrinsic fluorescence spectroscopy (IFS): the microbial pellet is irradiated with light ranging from the deep ultraviolet to infrared, which excites certain organic molecules in the microorganisms, including tryptophan, NADH, FAD, porphyrins, and others, and causes them to fluoresce in a characteristic way depending on the identity of the microbe. The exact pattern of fluorescence is compared with a database of 37 of the most common known pathogens to identify the organism present.
"We're using intrinsic fluorescence to identify the microorganisms. It's an innate property of most living organisms. Because it's intrinsic, no reagents are needed for the identification step," which removes many of the opportunities for mistakes and lowers test costs, says Walsh.
Testing in a controlled laboratory study shows the method can correctly identify the species in 96.5% of all test samples, and in the 2.7% of samples for which no species identity was provided, the system was able to correctly identify 67% to the family level, which is often enough information to select an effective therapy. Among over a thousand samples tested, the method never gave an incorrect result as to the family level or the Gram type.
Walsh says the research and development team in Durham is actively working on automating the system with robotics to make it a fully hands-off process. Blood cultures grow in their own time, often producing a positive result at an inconvenient time of the day for clinical labs, he points out, so automation could speed up diagnosis significantly.
"Our vision is to have a system that will automatically identify the blood culture isolate within 15 minutes of the culture being called positive," says Walsh. If a culture is positive at 2 AM, he says, automating this method could make it possible to identify the organism by 2:15 AM and send an electronic report to a patient's physician. They hope be begin testing and evaluating the feasibility of an automated form of the system in a clinical environment within months.
Rapid ID Procedure: An overall schematic of the simple three-step process (lyse-spin-read) is given in Figures 1a-c. Briefly, a 2.0 mL sample of warm (35-37oC) positive broth is removed from the test blood culture bottle and added to 1.0 mL of warm (35-37oC) selective lysis buffer (0.45% w/v Brij-O10 in 0.3M CAPS, pH 11.7), contained in a 15 mL screw capped polypropylene tube. The mixture was vortexed for 5 seconds at maximum speed and then placed in a 35-37oC waterbath for 60 seconds. After an additional 1-2 second vortex, 1.0 mL of the lysate was removed and layered onto a single 5/16 inch diameter polypropylene ball (CIC Ball Co.) floating on the surface of 0.5 mL of a solution of 24% w/v cesium chloride + 0.005% w/v Pluronic F-108 + 10 mM HEPES, pH 7.4 contained within an optical micro-centrifuge tube. The polypropylene ball was used to control the layering process and create an undisturbed interface. The tube was sealed with a screw-cap and centrifuged for 2 minutes at 10,000 rpm at 20-25oC in a microcentrifuge with A-8-11 swing-out rotor.
mBio® is an open access online journal published by the American Society for Microbiology to make microbiology research broadly accessible. The focus of the journal is on rapid publication of cutting-edge research spanning the entire spectrum of microbiology and related fields. It can be found online athttp://mbio.asm.org.
The American Society for Microbiology is the largest single life science society, composed of over 39,000 scientists and health professionals. ASM's mission is to advance the microbiological sciences as a vehicle for understanding life processes and to apply and communicate this knowledge for the improvement of health and environmental and economic well-being worldwide.
New Book Explains Antibiotic Resistance For A Broad AudienceWASHINGTON, DC -- May 13, 2005 -- Media coverage about “superbugs” that defy current treatments has increased the public’s awareness of and fears surrounding the issue of antibiotic resistance. A new book from ASM Press, Revenge of the Microbes: How Bacterial Resistance is Undermining the Antibiotic Miracle, provides an in-depth overview of the subject in a reader-friendly, comprehensible style that will engage everyone from scientists to everyday citizens.