Distribution of streptogramin resistance determinants among Enterococcus faecium from a poultry production environment of the USA.

OBJECTIVES: The impact of agricultural use of antimicrobials on the present and future efficacy of therapeutic drugs in human medicine is a growing public concern. Quinupristin/dalfopristin has been approved to treat human disease caused by vancomycin-resistant Enterococcus faecium and is related to virginiamycin, a streptogramin complex that has long been used in USA agriculture poultry production. METHODS: Streptogramin-resistant isolates of E. faecium from poultry production environments on the eastern seaboard were recovered without selection for streptogramin resistance and examined using ribotyping to evaluate clonal bias. Colony PCR screening for the previously described streptogramin resistance determinants erm(A), erm(B), msr(C), vgb(A), vat(D) and vat(E) was performed to determine the prevalence of streptogramin resistance mechanisms from these environments. RESULTS: The collection of E. faecium isolates was unevenly distributed among 28 ribogroups and did not cluster geographically. The most prevalent ribogroups was composed of isolates that possessed diverse antimicrobial resistance profiles. Of the 127 isolates examined, 63% were resistant to quinupristin/dalfopristin. The resistance determinants erm(A) and erm(B) were observed among 6% and 10%, respectively, of streptogramin-resistant isolates. msr(C) was detected in a single isolate that was resistant to macrolide and lincosamide antimicrobials. The streptogramin B hydrolase vgb(A) and the streptogramin A acetyltransferases genes vat(D) and vat(E) were not detected in any of the E. faecium isolates. CONCLUSIONS: These results indicate that there is widespread resistance to streptogramin antimicrobials among E. faecium throughout the poultry production region in this study and that the mechanisms of resistance to streptogramin antimicrobials within this population remain largely uncharacterized.

Multiple-antibiotic resistance of Enterococcus spp. isolated from commercial poultry production environments.

The potential impact of food animals in the production environment on the bacterial population as a result of antimicrobial drug use for growth enhancement continues to be a cause for concern. Enterococci from 82 farms within a poultry production region on the eastern seaboard were isolated to establish a baseline of susceptibility profiles for a number of antimicrobials used in production as well as clinical environments. Of the 541 isolates recovered, Enterococcus faecalis (53%) and E. faecium (31%) were the predominant species, while multiresistant antimicrobial phenotypes were observed among all species. The prevalence of resistance among isolates of E. faecalis was comparatively higher among lincosamide, macrolide, and tetracycline antimicrobials, while isolates of E. faecium were observed to be more frequently resistant to fluoroquinolones and penicillins. Notably, 63% of the E. faecium isolates were resistant to the streptogramin quinupristin-dalfopristin, while high-level gentamicin resistance was observed only among the E. faecalis population, of which 7% of the isolates were resistant. The primary observations are that enterococci can be frequently isolated from the poultry production environment and can be multiresistant to antimicrobials used in human medicine. The high frequency with which resistant enterococci are isolated from this environment suggests that these organisms might be useful as sentinels to monitor the development of resistance resulting from the usage of antimicrobial agents in animal production.

Serial disinfection with heat and chlorine to reduce microorganism populations on poultry transport containers.

A prototype system for the cleaning and decontamination of poultry transport containers was previously developed and evaluated as a means of eliminating foodborne pathogens entering poultry processing plants. While decontamination of the containers once with the use of either hot water (up to 70 degrees C) or sodium hypochlorite (up to 1,000 ppm) resulted in significant reductions in the numbers of coliforms and the elimination of small numbers of Salmonella, complete removal of pathogens was not attained. Therefore, the present study was conducted to determine whether repeated decontamination of the same containers could eliminate coliforms and Salmonella consistently. Individual five-tier containers consisting of galvanized steel frames and fiberglass floors were identified (n = 6) and decontaminated once per day for five consecutive days after being used to haul broilers from farms to the processing plant. Two types of containers were tested in this study: one had previously been used for broiler transportation, and the other had new floors. After each transport, the containers were first precleaned with a cleaning agent using a high-pressure jet (6,094 kPa) to remove debris and to loosen biofilms from surfaces. The containers were then immersed in an aqueous solution of 1,000 ppm of sodium hypochlorite at 70 degrees C for 2 min. Samples obtained from the container surfaces before and after each cleaning and decontamination were analyzed to obtain coliform and Salmonella counts. Coliforms were completely eliminated from both types of containers following one decontamination treatment. Because no Salmonella were detected on the containers, the effect of decontamination in the elimination of Salmonella was not determined. Similar treatments on five successive days also resulted in poultry transport containers that were essentially free of Salmonella and coliforms. This decontamination system involving a combination of heat and sodium hypochlorite can be used as a standard method for cleaning poultry transport containers in the poultry industry. It is recommended that such containers be cleaned after each use to avoid the potential risk of a buildup of significantly higher loads of pathogenic microorganisms and their biofilms.