Resistance of Gram-Negative Bacilli to Gentamicin

Abstract

Strains of Pseudomonas aeruginosa resistant to gentamicin have appeared during three years of extensive use of this antibiotic in the Winnipeg General Hospital. During October and November of 1970, isolates of P. aeruginosa sensitive to gentamicin were recovered from 62 patients. Thirty-one of these patients received gentamicin; in five patients, strains of P. aeruginosa resistant to gentamicin were isolated after therapy. Four patients received gentamicin parenterally, and one topically. No gentamicin-resistant P. aeruginosa appeared in the 31 patients not given gentamicin. Only two of 622 isolates of Enterobacteriaceae were resistant. Of 108 burns treated between October, 1968 and December, 1970 with daily prophylactic topical applications of gentamicin, 24 were colonized with P. aeruginosa; the organisms in seven patients were initially resistant. Pyocine typing on all resistant organisms from both groups of patients suggests that episodes of cross-infection with gentamicin-resistant strains have occurred in patients with burns. No persisting hospital reservoir of gentamicin-resistant organisms has been identified.