The Center for Adaptation Genetics and Drug Resistance at Tufts University School of Medicine. Stuart B. Levy, M.D., Director


Current and Ongoing Projects:

Microbial Ecology: clinical and commensal environments - Year 20
Principal Investigator: Stuart B. Levy, M.D.
Co-PI: Bonnie Marshall, M.T.


Ecology Program Studies in the area of microbial ecology have involved the introduction of selected bacteria or antibiotics in particular environments: intestinal tract, farm, laboratory, and home.

Early studies showed the effect of the introduction of low levels of antibiotics as growth promoters in chickens on antibiotic resistance among bacteria in animals and people on a farm. Other studies showed spread of resistant bacteria and resistance plasmids among bacteria in man and animals.

Other work has looked at the survival of bacteria under different conditions, as well as the transfer of plasmids within the gastrointestinal tract. Studies have looked at the kinds of resistance determinants in wild animals and fish and the spread of resistant bacteria on the farm environment.

Some of the more epidemiologic studies have looked at the role of antibiotics in the selection of drug resistant strains.

Home Environments and Biocides
The microbiology of the home environment is receiving new attention, particularly in the wake of food-borne diseases and the potential consequences of increasing numbers of household products bearing antibacterial chemicals. The latter include triclosan, triclocarbon and quaternium ammonium compounds. We have demonstrated that triclosan, like other antibiotics, has a target, the enoyl reductase, involved in lipid biosynthesis. Mutations in the gene fabI leads to triclosan resistance. Resistance to this and other biocides can also be linked to multidrug efflux pumps such as AcrAB in E. coli which mediate cross resistance to antibiotics.

With the mounting number of biocide-containing products entering the market for household use, there is heightened concern that they will contribute to the rising problem of antibiotic resistance among bacteria. Studies in this area look at the mechanism of action, mechanism of resistance and epidemiology of biocide/antibiotic resistant organisms in the home. Other studies focus on household practices relating to hygiene so as to better understand the interaction between hygiene, infection and the “hygiene hypothesis,” namely the effect of overzealous hygienic measures on emergence of allergic disorders, such as asthma and dermatitis.

Selected References

  • Levy, S.B., G.B. FitzGerald and A.B. Macone (1976) Changes in intestinal flora of farm personnel after introduction of tetracycline-supplemented feed on a farm. New Eng. J. Med. 295:583-588.

  • Levy, S.B., G.B. FitzGerald, and A.B. Macone (1976) Spread of antibiotic resistance plasmids from chicken to chicken and from chicken to man. Nature 260:40-42.

  • Levy, S.B., B. Marshall, A. Onderdonk and D. Rowse-Eagle (1980) Survival of E. coli host-vector systems in the mammalian intestine. Science 209:391-394.

  • Marshall, B., S. Schluederberg, C. Tachibana and S.B. Levy (1981) Survival and transfer in the human gut of poorly mobilizable (pBR322) and of transferable plasmids from the same carrier E. coli. Gene 14:145-154.

  • Onderdonk, A, B. Marshall, R. Cisneros and S.B. Levy (1981) Competition between congenic Escherichia coli K-12 strains in vivo. Infect. and Immun. 32:74-79.

  • Marshall, B., C. Tachibana and S.B. Levy (1983) Frequency of tetracycline resistance determinant classes among lactose-fermenting coliforms. Antimicrob. Agents Chemother. 24:835-840.

  • Rolland, R., G. Hausfater, B. Marshall and S.B. Levy (1985) Increased frequency of antibiotic resistant gut flora in wild baboons in contact with human refuse. Appl. Environ. Microbiol. 49:791-794.

  • DePaola, A., P.A. Flynn, R.M. McPhearson and S.B. Levy (1988) Phenotypic and genotypic characterization of tetracycline and oxytetracycline resistant Aeromonas from cultured channel catfish (Ictalurus punctatus) and their environments. Appl. Env. Microb. 54:1861-1863.

  • Levy, S.B., B. Marshall, S. Schluederberg, D. Rowse and J. Davis (1988) High frequency of antimicrobial resistance in human fecal flora. Antimicrob. Agents Chemother. 32:1801-1806.

  • Marshall, B.M., P.A. Flynn, D. Kamely and S.B. Levy (1988) Survival of Escherichia coli with and without Col E1::Tn5 after aerosol dispersal in a laboratory and a farm environment. Appl. Env. Microb. 54:1776-1783.

  • Marshall, B.M., D. Petrowski and S.B. Levy (1990) Inter and intraspecies spread of E. coli in a farm environment in the absence of antibiotic usage. Proc. Nat'l Acad. Sci (USA) 87:6609-6613.

  • Summers, A.O., J. Wireman, M.J. Vimy, F.L. Lorscheider, B. Marshall, S.B. Levy, S. Bennett, and L. Billard (1993) Mercury released from dental "silver" fillings provokes an increase in mercury- and antibiotic-resistant bacteria in oral and intestinal floras of primates. Antimicrob. Agents Chemother. 37:825-834.

  • Moken, M.C., L.M. McMurry, and S. B. Levy. (1997) Selection of multiple antibiotic resistant (Mar) mutants of Escherichia coli by using the disinfectant pine oil: roles of themar and acrAB loci. Antimicrob. Agents Chemother. 41:2770-2772.

  • McMurry, L.M., M. Oethinger and S.B. Levy. (1998) Triclosan targets lipid synthesis. Nature 394:531-532.

  • Marshall, B., H. Shin-Kim, D. Perlov and S.B. Levy (2000) Release of bacteria during the purge cycles of steam-jacketed sterilizers. Brit. J. Biomedical Sciences 56:247-252.

  • Walson, J.L., B. Marshall, B.M. Pokhrel, K.K. Kafle and S. B. Levy. (2001) Fecal carriage of antibiotic resistance in Nepal reflects proximity to Kathmandu. J. Inf. Dis. 184: 1163-69

  • Aiello, A.E., B. Marshall, S.B. Levy, P. Della-Latta, E. Larson (2004). The relationship between triclosan and antibiotic susceptibilities among bacteria isolated from hands in the community. Antimicrob. Agents Chemother. 48:2973-2979

  • Aiello, A.E., B. Marshall, S.B. Levy, P. Della-Latta, S.X. Len & E. Larson (2005). Household antibacterial cleaning and hygiene product use: an emerging risk factor for carriage of antibiotic-resistant bacteria on the hands? Emerg. Inf. Dis. 11:1565.

  • Domain, F and S.B. Levy (2009) GyrA interacts with MarR to reduce repression of the marRAB operon in E. coli. J Bacteriol 192: 942-948

  • McMurry, L.M. and S.B. Levy (2010) Evidence that the regulatory protein MarA of Escherichia coli represses rob by steric hindrance. J Bacteriol 192:3977-3982.

Invited Editorials

  • Levy, S.B. (2002) Antimicrobial consumer products: Where’s and What’s the risk? Arch. of Dermatol. 138:1087-1088

  • Levy, S.B. (2005) Antibiotic resistance – The problem intensifies. Adv. Drug Delivery Reviews 57:1446-1450.

Invited Reviews

  • Alekshun, M. & S.B. Levy (2004) Targeting virulence to prevent infection: to kill or not to kill? Drug Discovery Today: Therapeutic Strategies. 1:483-489

  • Alekshun, M. and S.B. Levy (2006). Commensals upon us. Biochem. Pharm. 71:893-900.

  • Alekshun, M.N. and S.B. Levy (2007). Molecular mechanisms of antibacterial resistance. Cell. 128:1037-1050

  • Marshall, B.M., D.J. Ochieng, S.B. Levy. (2009). Commensals: underappreciated reservoirs of antibiotic resistance. Microbe 4:231-238.

Book Chapters

  • Vila, J., D.G. White, P.F. McDermott and S.B. Levy. (2008) “Bacterial Resistance to Antimicrobials” in Travellers’ Diarrhea 2nd ed. (C.D. Ericsson, H.L. Dupont and R. Steffen, eds.) B.C. Decker, Inc. (London) pp 43-57


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