Prevalence of Antibiotic Resistance in Enterococci: A 14 Year Survey

Enterococci are leading causes of nosocomial bacteremia, surgical wound and urinary tract infections. They are ubiquitous bacteria commonly occurring in foods, and in recent years there has been increased attention towards multidrug strains incidence, since they may cause the failure of therapeutic treatments. Therefore, we analyzed the occurrence of Enterococcus species isolated from raw meat (beef, chicken and pork), cheese, and ready-to-eat salads, and the change of the antibiotic resistance in Enterococcus faecium and E. faecalis strains in a 14 year survey. Among the 589 Enterococcus strains, E. faecium and E. faecalis represented the most numerous species in all types of food examined (42.8% and 38.7% respectively). Antibiotic resistance and number of Multi Drug Resistant strains have increased, reaching very high levels from 2002 to 2015. In the last two years, E. faecalis isolates sometimes reached percentages of resistance higher than 40% against tetracycline, vancomycin, linezolid, erythromycin, and ampicillin. Antibiotic resistance in E. faecium was lower than in E. faecalis for almost all antimicrobials tested. The highest percentage of resistance in 2014-2015 was registered for erythromycin (42.5%), followed by tetracycline (30%), ciprofloxacin, and linezolid (both 27.5%). The number of resistant phenotypes also increased during this survey in both species to more than 20 in 2014-2015. Despite the fact that Enterococcus spp. do not represent a problem for immunocompetent individuals, surveillance of antibiotic resistance in this kind of micro-organism continues to be important because, as shown in our results, antibiotic resistance has sharply increased in recent years.