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United States Department of Agriculture

Agricultural Research Service

Research Project: EPIDEMIOLOGY, ECOLOGY, AND MOLECULAR GENETICS OF ANTIMICROBIAL RESISTANCE IN PATHOGENIC AND COMMENSAL BACTERIA FROM FOOD ANIMALS

Location: Bacterial Epidemiology and Antimicrobial Resistance

Title: Antimicrobial resistance and virulence of Enterococcus faecalis isolated from retail food

Authors
item Mcgowan-Spicer, Lori - UNIV OF RICHMOND
item Cray, Paula
item Frye, Jonathan
item Meinersmann, Richard
item Barrett, John
item Jackson, Charlene

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 15, 2007
Publication Date: April 1, 2008
Citation: Mcgowan-Spicer, L., Cray, P.J., Frye, J.G., Meinersmann, R.J., Barrett, J.B., Jackson, C.R. 2008. Antimicrobial resistance and virulence of Enterococcus faecalis isolated from retail food. Journal of Food Protection. 71(4):760-769.

Interpretive Summary: The use of antimicrobials in the food supply and the potential for transfer of antimicrobial resistant bacteria into the human population is cause for concern. From 2000-2001, vegetables, fruits, and meat were purchased from six grocery store chains in the North Georgia USA area and cultured for the presence of enterococci. From the study, 80 Enterococcus faecalis were isolated and prevalence and association of antimicrobial resistance and virulence factors present in the isolates was investigated. While the highest rates of resistance were observed for lincomycin (73/80, 91%) and bacitracin (57/80, 71%), low rates of resistance (<40%) were found for chloramphenicol, ciprofloxacin, erythromycin, flavomycin, gentamicin, kanamycin, nitrofurantoin, penicillin, and tylosin. Of the virulence factors tested, the majority of isolates were positive for sex pheromone determinants, ccf and cpd (78/80, 98% and 74/80, 93%) and a cell wall adhesin, efaAfs, (77/80; 96%). Positive statistical associations (significance level = 0.05) were found between several virulence genes and bacitracin resistance, erythromycin resistance, lincomycin resistance and tetracycline resistance. Negative correlations were observed among many of the virulence attributes and ciprofloxacin, erythromycin, flavomycin, gentamicin, kanamycin, and tylosin resistance. This research will be useful to policy makers and researchers who can use this information when studying antimicrobial resistant bacteria that may be found on food.

Technical Abstract: Although enterococci are considered opportunistic nosocomial pathogens, their contribution to food-borne illnesses via dissemination through retail food remains undefined. In this study, prevalence and association of antimicrobial resistance and virulence factors of 80 Enterococcus faecalis isolated from retail food items was investigated. While the highest rates of resistance were observed for lincomycin (73/80, 91%) and bacitracin (57/80, 71%), lower rates of resistance (is less than or equal to 40%) were found for chloramphenicol, ciprofloxacin, erythromycin, flavomycin, gentamicin, kanamycin, nitrofurantoin, penicillin, and tylosin. Overall resistance to antimicrobials was low. Of the virulence factors tested, the majority of isolates were positive for ccf (78/80, 98%), efaAfs (77/80; 96%) and cpd (74/80, 93%). Isolates were also common for cob (72/80, 90%) and gelE, (68/80, 85%). Very few isolates contained cylMBA (12/80, 15% for cylM and 9/80, 11% each for cylB and cylA) and efaAfm (2/80, 3%). Positive statistical associations (significance level = 0.05) were found between the agg allele and tetracycline resistance, cylM with erythromycin resistance, and gelE and efaAfs with lincomycin resistance. The cylB and cylA alleles were also positively correlated with bacitracin and tetracycline resistance. Negative correlations were observed among many of the virulence attributes and ciprofloxacin, erythromycin, flavomycin, gentamicin, kanamycin, and tylosin resistance. These data suggest that both positive and negative associations exist between antimicrobial resistance genes and virulence in E. faecalis isolated from foods commonly purchased and consumed from grocery stores.

Last Modified: 9/1/2014
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