[Enterococcus sp. resistance, a growing problem. Epidemiologic study (1987-1993)]

Infectious processes caused by Enterococcus species currently constitute a growing problem due to the rapid appearance of resistances and the scarce existing therapeutic alternatives. The patterns of in vitro resistance to ampicillin, vancomycin and gentamycin were therefore studied in addition to their evolution over time of the isolates of Enterococcus sp. identified in the Salamanca University Hospital from 1987-1993.

Data were obtained from a computerized system of epidemiologic surveillance of infection in in-patients on the basis of microbiologic information. Sensitivity tests were performed by the disc-plate diffusion method of the National Clinical Committee for Laboratory Standards.

Global resistance was 2.1% to vancomycin versus 8.3% to ampicillin with most of the isolates being resistant to gentamycin. The frequency of appearance of resistance increased over time with 19.6% of the strains found to be resistant to ampicillin (p < 0.05; CI 95%, 1987-1988: 12.2-24.3%) in 1993 and from 1991-1992 2.7% were found to be resistant to vancomycin. The strains from patients from the medical area were more resistant to ampicillin (p < 0.05; CI 95%, 0.8-7.4%) and vancomycin (p < 0.05; CI 95%, 0.2-3.9%) than those corresponding to patients from the surgical area. Greater resistance was identified to ampicillin and vancomycin in the isolates from urine and wound exudates. Patients under the age of 1 year were significantly less resistant to ampicillin (p < 0.05; CI 95%, with respect to the group from 21 to 40 years: 1.6-13.9%) and vancomycin with the greatest resistance being found from 41 to 60 years of age. E. faecalis (2.9% resistance) was more resistant to vancomycin and E. faecium was more resistant to ampicillin (27.8% resistant strains) (p < 0.05: CI 95%, 3.2-33.6%).

Over time there has been a rapid increase in the number of enterococci resistant to ampicillin while, to date, vancomycin shows good activity against these bacteria.