[Hospital infection caused by enterococci. The previous use of antibiotics as risk factors in a case-control study]

Nosocomial infection by enterococci is of growing importance and recognition. The risk factors, morbidity and prognosis of the same were investigated by a case and control study in a third level university hospital.

One hundred patients with nosocomial infection by enterococci were compared with 100 randomly selected control patients with non enterococcic nosocomial infection. Cases and controls were taken from a series of 10,926 patients examined in search of nosocomial infection by successive cut offs of prevalence.

The prevalence of nosocomial infection by enterococci was found to be 9.9 per 1,000 admissions. Analysis among cases and controls by the odds ratio indicated a positive association for nosocomial infection by enterococci for the following risk factors: male sex (1.8), receipt of intensive care (3.6), predisposing diseases (3.1), urinary catheter (3), abdominal-genital surgery (2.4) or nephro-urologic surgery (4.6), other previous infections (1.9) and previous exposure to antibiotics (3.7), mainly aminoglucosides (4.2). Urinary infections and those of the surgical wound predominated, 15 patients had bacteremia, with mortality related with infection being 2%, preinfection hospital stay was 34.7 days and the mean stay was of 8.3 days but these data were not statistically different in the control group. The enterococcic infections were most frequently polymicrobian (odds ratio 5.5) received worse antibiotic coverage (5.1) and presented greater number of therapeutic failures or recurrences (2.5).

Nosocomial infection by enterococci is relatively frequent and virulent. The risk factors identified in this study are in agreement with those found in most series. The previous use of aminoglucosides was specially capable of selecting enterococci but only 13% demonstrated high level resistance to gentamicin.