Leah D. Tivoli
Project title: Clostridium perfringens: A Reservoir of Antibiotic Resistance Genes in the Environment?
Completed in: 2007
Clostridium perfringens is one of the most widely spread bacteria found in soil, water, food as well as animal and human feces. C. perfringens has been reported to carry a number of resistance genes, however its ability to serve as a reservoir is not well understood. In this study, the prevalence and distribution of acquired antibiotic resistance genes was examined in C. perfringens isolated from water, soil and sediment between 2003-06, from 11 states [AZ, CA, FL, IN, ID, MD, MO, NC, PA, TX, and WA}. There were 164 C. perfringens identified using Tryptose Cycloserine Agar from primarily water, soil and sediment. These isolates were screened for the carriage of three different tetracycline (tet) genes [tetP(A), tetP(B), tet(M)] and for four different macrolide-lincosamide-streptogramin (MLS) genes [mef(A), erm(B), erm(F), erm(Q)]. Whole cell DNA-DNA hybridization was used to screen these isolates. Of the 164 isolates, 117 isolates (71.3%) carried > 1 antibiotic resistant gene(s), 65 isolates (39.6%) carried > 2 resistant genes, and 47 isolates (28.7%) were negative for all seven antibiotic resistant genes examined. Because many of the genes found in C. perfringens are associated with conjugative elements, conjugation experiments were performed to determine if C. perfringens was capable of gene transfer to bacteria outside the genus. To determine if C. perfringens carried antibiotic resistance genes on conjugative elements ten C. perfringens isolates were selected as donors and Enterococcus faecalis JH2-2 as recipient in mating studies. All donors were able to transfer macrolide resistance to JH2-2 at frequencies varying from 10-8 - 10-9 transconjugants/recipient. Considering data from conjugation experiments and the multitude of genes carried, we suggest C. perfringens could be a reservoir for these genes in the environment and further study is warranted.