Gentamicin-carbenicillin synergy among gentamicin resistant Pseudomonas aeruginosa

Forty-five isolates of gentamicin resistant Pseudomonas aeruginosa were evaluated for gentamicin-carbenicillin synergy. Only 9 percent (4/45) showed synergy. Of nine isolates with demonstrable zones around a gentamicin disc (8 to 12 mm), none showed a synergistic response. Effective treatment of gentamicin resistant Ps. aeruginosa with gentamicin and carbenicillin should not be assumed without additional test procedures.