Tips from the journals of the American Society for Microbiology

October 15, 2008

Varying Combinations of Antiviral Drugs May Effectively Treat Chronic Hepatitis Virus Infection in Woodchucks and Have Implications for use in Humans

Oral administration of various combined and independent antiviral drug therapies may effectively treat chronic hepatitis B virus (HBV) infection in woodchucks, a well-characterized mammalian model for research with human implications, and provide an alternative strategy for managing drug resistance. The researchers from Cornell University, Ithaca, New York; Gilead Sciences, Durham, North Carolina; and Georgetown University Medical Center, Washington, DC report their findings in the October 2008 issue of the journal Antimicrobial Agents and Chemotherapy.

Chronic infection with HBV is responsible for 1.2 million annual deaths worldwide. Statistics also show that 2 billion people currently or previously suffered from infection while 350 million people are chronic carriers of HBV and are at risk of developing chronic hepatitis, hepatic cirrhosis, and hepatocellular carcinoma. Preventative vaccines are currently offered, however, side effects and drug resistance are limiting the efficacy of available treatment therapies.

In the study researchers evaluated the antiviral effects of orally administered adefovir dipivoxil (ADV) or tenofovir disoproxil fumarate (TDF) alone or in combination with lamivudine (3TC) or emtricitabine (FTC) in woodchucks with chronic hepatitis virus infection. Initial results showed once daily treatment for 48 weeks with ADV plus 3TC or TDF plus FTC greatly reduced viral levels from those pretreatment. Additional treatment with TDF plus 3TC, ADV alone, ADV plus FTC, TDF alone, 3TC alone, and FTC alone showed pronounced declines in viral levels in all groups. Following drug withdrawal most woodchucks displayed renewed hepatitis virus replication, but some did experience sustained effects. Lastly, no toxicity was observed following administration of any of the drugs or drug combinations.

"In conclusion, the oral administration of 3TC, FTC, ADV, and TDF alone and in combination was safe and effective in the woodchuck model of HBV infection," say the researchers.

(S. Menne, S.D. Bulter, A.L. George, I.A. Tochkov, Y. Zhu, S. Xiong, J.L. Gerin, P.J. Cote, B.C. Tennant. 2008. Antiviral effects of lamivudine, emtricitabine, adefovir dipivoxil, and tenofovir disproxil fumarate administered orally alone and in combination to woodchucks with chronic woodchuck hepatitis virus infection. Antimicrobial Agents and Chemotherapy, 52. 10: 3617-3632.)

New Study Claims Acne is Not Associated with Yet-Uncultured Bacteria

In a new study researchers from Aarhus University, Denmark found bacteria in the follicles of acne patients and healthy individuals to be those of previously known species, disputing the theory that acne is caused by some yet-to-be-identified bacteria. They report their findings in the October 2008 issue of the Journal of Clinical Microbiology.

Affecting up to 80% of teenagers as well as some adults, acne not only causes clinical problems but also severe social, psychological and emotional issues. Prominently attributed to the bacterium Propionibacterium acnes due to a large increase in colonization density at puberty, some research suggests that P. acnes may only be responsible for inflammation rather than the true cause of infection.

In the study researchers collected bacteria from the follicles of acne patients and healthy individuals as well as superficial skin samples from acne patients and tested for yet-uncultured species. Only P. acnes was found in the follicles of healthy patients, whereas P. acnes as well as Staphylococcus epidermidis and other species of limited complexity were identified in acne patients. Superficial skin samples showed a more diverse microbial presence of 12 to 16 bacterial species.

"The findings of the study exclude the possibility that acne is associated with yet-uncultured bacteria and shows that healthy skin follicles constitute a remarkably exclusive habitat allowing colonization only by P. acnes," say the researchers.

(M.Bek-Thomsen, H.B. Lomholt, M. Kilian. 2008. Acne is not associated with yet-uncultured bacteria. Journal of Clinical Microbiology, 46. 10: 3355-3360.)

New Method May Rapidly and Effectively Detect Significant Food-Borne Pathogen

Researchers from Sweden and Finland have developed a rapid and specific method that may detect the bacterium Yersinia enterocolitica, a common cause of gastric illness, in food. They report their findings in the October 2008 issue of the journal Applied and Environmental Microbiology.

Y. enterocolitica is the causative agent of yersiniosis, an internal infection resulting in diarrhea, fever, abdominal pain, and vomiting. Predominantly considered a food-borne pathogen, most cases sporadically occur worldwide and the source of infection is often unknown. Pigs are believed to be a main reservoir for Y. enterocolitica with pork being the most likely vehicle of transmission to humans. The ability of Y. enterocolitica to multiply in foods at low temperatures as well as in vacuum-packed containment is cause for major food safety concern and current detection methods available are time consuming and inefficient.

In the study researchers developed and evaluated a TaqMan probe-based real-time PCR method for detecting Y. enterocolitica in food in one to two days. Following overnight synthetic enrichment of samples of milk, minced beef, cold-smoked sausage, fish and carrots with Y. enterocolitica, results of the TaqMan PCR test showed high levels of sensitivity, robustness, precision and efficiency in detecting the bacterium.

"A rapid and specific real-time PCR method for the detection of pathogenic Y. enterocolitica bacteria in food, as presented here, provides a superior alternative to the currently available detection methods and makes it possible to identify the foods at risk for Y. enterocolitica contamination," say the researchers.

(S. Thisted Lambertz, C. Nilsson, S. Hallanvuo, M. Lindblad. 2008. Real-time PCR method for detection of pathogenic Yersinia enterocolitica in food. Applied and Environmental Microbiology, 74. 19: 6060-6067.)

American Society for Microbiology

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