Resumen

MELANIA, Araya; DAVIDOVICH, Gabriela; CHAVES, Carolina  y  ARIAS, María Laura. Identificación de Enterococcus sp. en muestras de leche cruda del Area Metropolitana de Costa Rica y evaluación del patrón de sensibilidad a antibióticos . ALAN [online]. 2005, vol.55, n.2, pp.161-166. ISSN 0004-0622.

Bacteria from the genus Enterococcus sp. were isolated and identified from non-pasteurized milk samples obtained from the Costa Rican Metropolitan Area, in order to evaluate its sensitivity pattern to common use antibiotics. One hundred five milk samples were collected from suppliers of a national dairy industry. The initial isolation was done in EVA (Ethyl violet agar). Isolated colonies were initially characterized phenotypically as Enterococcus sp. using biochemical tests, species’ identification was done using the Api 20 Strep kit. The different Enterococci species were tested for their antibiotic sensitivity using the plate diffusion method; the minimal inhibition concentration (MIC) to vancomycin was determined using E test. 38% of the milk samples were positive for Enterococcus; 48 different strains were isolated, where E. faecalis corresponded to 71%, E. faecium to 19%, E. durans to 4%, E. gallinarum to 4% and E. avium to 2%. The geographical distribution analysis of the species isolated did not show significant statistical differences according to the origin of the samples. All isolates identified showed an important resistance rate to the antibiotics tested. The aminoglycoside family showed the lower resistance rate, the resistance to eritromicin, tetracycline and chloranphenicol was lower than 50% and all strains were sensitive to bacitracin. An 8% resistance rate to vancomycin was determined. No relationship between the resistance rate of samples and the province of origin was found, but it is important to emphasize that the strains resistant to vancomycin came from Cartago, one of the Costa Rican regions with highest milk production.

Palabras clave : Enterococcus sp; antibiotics resistance; non-pasteurized milk.