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Tips from the journals of the American Society for Microbiology

July 20, 2010

Quitting Smoking May Minimize Harmful Bacteria and Replenish Healthy Bacteria

Patients with chronic gum disease who quit smoking in addition to undergoing nonsurgical therapy not only demonstrated a lower abundance of harmful oral pathogens, but also an increase in health-associated bacteria. The researchers from The Ohio State University, Columbus Ohio, and Newcastle University, United Kingdom report their findings in the July 2010 issue of the Journal of Clinical Microbiology.

It is well established that oral bacteria play an important role in the origin of chronic gum disease and that smoking tobacco contributes to a pathogen rich environment. Although prior studies indicate that quitting smoking can alter the oral microbial community, it is unknown if pathogenic colonization can actually be reversed.

In order to determine the effect of quitting smoking on select oral bacteria researchers launched a long-term study, at the beginning of which, plaque samples were collected from 22 initial smokers. Twelve months following nonsurgical periodontal therapy and counseling samples were again taken from all 22 participants, however, 11 were quitters and 11 still smoked. Results showed decreased levels in various bacterial pathogens as well as an increase in health-associated species in those patients who no longer smoked.

"Following nonsurgical periodontal therapy and smoking cessation, the subgingival microbiome is recolonized by a greater number of health-associated species and there are a significantly lower prevalence and abundance of putative periodontal pathogens," say the researchers. "These results indicate a critical role for smoking cessation counseling in periodontal therapy for smokers in order to effectively alter the subgingival microbiome."

(S.L. Delima, R.K. McBride, P.M. Preshaw, P.A. Heasman, P.S. Kumar. 2010. Response of subgingival bacteria to smoking cessation. Journal of Clinical Microbiology, 48. 7: 2344-2349.)




Microbicide Containing Engineered Bacteria May Inhibit HIV-1

Researchers from the U.S. and abroad used bacteria inherent to the human vaginal tract to develop a live, topical microbicide that may induce production of HIV-1 protein inhibitors and ultimately prevent transmission of the virus. They detail their findings in the July 2010 issue of the journal Antimicrobial Agents and Chemotherapy.

HIV-1 has killed more than 25 million people over three decades and there are currently 33 million people living with the virus worldwide. Although health officials are ultimately striving to develop an effective vaccine, topical anti-HIV-1 microbicides are a promising alternate strategy for minimizing transmission. Live microbicides are of particular interest as they utilize bacteria inherent to the human body to induce natural production of anti-HIV-1 agents.

Lactobacillus spp. are ideal candidates for live microbicide development as they are the predominant bacterial species in the female genital tract. In the study researchers engineered a human vaginal isolate of Lactobacillus jensenii capable of generating the anti-HIV-1 proteins RANTES and CIC5 RANTES which oppose the HIV-1 receptor protein, CCR5. Both RANTES variants inhibited HIV-1 infection and demonstrated significant activity against various HIV-1 genetic subtypes.

"Our results provide proof of principle for the efficient secretion of an anti-HIV-1 active CCR5 antagonist by an engineered vaginal commensal bacterium, which represents an important advancement toward realistic, safe, and low-cost prevention of sexual transmission of HIV-1," say the researchers.

(L. Vangelista, M. Secchi, X. Liu, A. Bachi, L. Jia, Q. Xu, P. Lusso. 2010. Engineering of Lactobacillus jensenii to secrete RANTES and a CCR5 antagonist analogue as live HIV-1 blockers. Antimicrobial Agents and Chemotherapy, 54. 7: 2994-3001.)




Salmonella Contaminated Pork May Pose Health Risk for Humans

German researchers have isolated a strain of Salmonella in pork that is closely related to the bacteria commonly found in chickens and linked to human food-borne illness. They report their findings in the July 2010 issue of the journal Applied and Environmental Microbiology.

First emerging overseas in the mid-1990's in pigs, initial studies showed the genetic make-up of Salmonella enterica subsp. enterica serovar Typhimurium (or S. enterica serovar 4,[5],12:i:-) to be very similar to S. enterica serovar Typhimurium, the strain commonly found in chickens. It is a known cause of gastroenteritis and has become increasingly associated with worldwide outbreaks over the last few years.

"Interestingly, the number of S. enterica serovar 4, [5],12:i:- strains isolated from humans and sent on voluntary basis to the National Reference Centre for Salmonella and other Enterics increased from 0.1% in 1999 to 14.0% in 2008," say the researchers.

In the study researchers collected and analyzed strains of S. enterica serovar 4,[5],12:i:-from pigs, pork, and humans over a two-year period in an attempt to better understand its transmission capabilities. Additionally, the strains' genetic relatedness, pathogenicity and antimicrobial resistance were compared to that of S. enterica serovar Typhimurium. Two major clonal lineages were observed among the two strains and 65% of isolates from both lineages were resistant to ampicillin, streptomycin, tetracycline and sulfamethoxazole.

"Overall the study indicates that in Germany S. enterica serovar 4, [5],12:i:- strains isolated from pig, pork, and human are highly related, showing their transmission along the food chain," say the researchers. "Since the pathogenicity gene repertoire is highly similar to that of S. enterica serovar Typhimurium, it is essential that interventions are introduced at the farm level in order to limit human infection."

(E. Hauser, E. Tietze, R. Helmuth, E. Junker, K. Blank, R. Prager, W. Rabsch, B. Appel, A. Fruth, B. Malorny. 2010. Pork contaminated with Salmonella enterica serovar 4, [5], 12:i:-, an emerging health risk for humans. Applied and Environmental Microbiology, 76. 14: 4601-4610.)
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American Society for Microbiology

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