[Antibiotic sensitivity of bacteria isolated from pathological specimens and utilization of beta-lactams in an orthopedic surgery service].

From 1980 to 1984, computerized data on the sensitivity to the main antibiotics of 1991 strains isolated from clinical specimens were evaluated in relation to beta-lactam use and hospital activity in a unit of orthopedic surgery. No major variations were found in distribution of species throughout the study period, whereas sensitivity to antimicrobial agents changed. From 1980 to 1982, patients had postoperative prophylactic treatment with cephalosporin (cefazolin) for two days; during the same period, 59% of 557 Gram negative organisms were resistant to cefazolin and 31% of Staphylococci were resistant to methicillin (and to other antibiotics). In 1983 and 1984, cefazolin was replaced by intraoperative flash therapy with a penicillin-M (cloxacillin); concomitantly, sensitivity to cefazolin increased among Gram negative organisms (38% of 485 isolates were cefazolin-resistant; p less than 0.001) and Staphylococci (16% of 342 isolates were methicillin-resistant; p less than 0.001). Phage typing of S. aureus failed to disclose any epidemic outbreak. Since hospital activity remained the same throughout the period under study, it seems justified to correlate the increase in bacterial sensitivity observed to the decrease in use of cephalosporin, although other factors (microepidemic, isolation techniques) may be involved.