Effect of media, temperature and culture conditions on the species population and antibiotic resistance of enterococci from broiler chickens.

AIMS: The effect of media type, incubation temperature and enrichment period on the species population and antibiotic susceptibility of enterococci from poultry carcass rinsates was determined. METHODS AND RESULTS: Aliquots of rinsates, incubated in BBL Enterococcosel broth at 37 degrees C, 42 degrees C, or 45 degrees C for 24 and 48 h, were inoculated onto BBL Enterococcosel and M-enterococcus agar. Presumptive positive colonies were identified to species and tested for antibiotic resistance. Significant differences (P < or = 0.05) were observed for media and temperature. More Enterococcus faecalis were isolated from M-enterococcus media and at 37 degrees C while more E. faecium were isolated from Enterococcosel agar and at 45 degrees C. The number of antibiotic-resistant E. faecalis and E. faecium were also affected by media and temperature. CONCLUSIONS: Culture conditions for enterococci affect the observed species and antibiotic resistance patterns and therefore should be carefully considered. SIGNIFICANCE AND IMPACT OF THE STUDY: This study indicates that media and temperature can influence the recovery and selection of enterococcal species and antibiotic susceptibility.

Anomalies in species identification of enterococci from veterinary sources using a commercial biochemical identification system.

AIMS: A commercial biochemical panel ID kit was used to identify presumptive enterococci isolates of veterinary or agricultural origin obtained during different steps of culture. METHODS AND RESULTS: Fifty isolates identified as enterococci using a genus PCR assay were tested for genus and species identification using the BBL Crystal Identification Gram-Positive ID kit (Becton Dickinson, Sparks, MD, USA). Following sub-culture of the isolates three times, 59% agreement with the original panel ID was obtained. After four and six sub-cultures, percentage agreement increased to 61 and 64%, respectively. Nineteen of the 50 cultures were identified as both Enterococcus faecalis and E. faecium. CONCLUSIONS: As a result of the variability between speciation of isolates following re-culture, additional methods for speciation are warranted. SIGNIFICANCE AND IMPACT OF THE STUDY: This study suggests that the identification of the genus and species of non-human enterococcal isolates can vary greatly during successive passages when using this kit.