PENICILLIN SUSCEPTIBILITY TESTING OF PENICILLINASE-PRODUCING NEISSERIA-GONORRHOEAE BY THE E-TEST - A NEED FOR CAUTION

The penicillin MICs of 52 clinical isolates of penicillinase producing Neisseria gonorrhoeae (PPNG) and five reference strains were tested by agar dilution and the E test. All 52 PPNG were scored resistant (greater than or equal to 2 mg/L) by agar dilution whereas only 78.8% (41/52) and 82.7% (43/52) were classified as resistant by normal (0.016-256 mg/L) and low range (0.002-32 mg/L) E test MICs respectively. Isolates with an E test penicillin MIC greater than or equal to 0.19 mg/L should be checked by a specific test for beta-lactamase production.