Agar dilution method for susceptibility testing of Neisseria gonorrhoeae

Abstract

The antibiotic susceptibilities of Neisseria gonorrhoeae isolates obtained from patients attending a clinic for sexually transmitted diseases in Tucumán, Argentina, were determined by the agar dilution method (MIC). 3.5% of the isolates produced β-lactamase. A total of 96.5% of β-lactamase negative isolates tested were susceptible to penicillin (MIC ≤ 2 μgml-1); 14.03% of the tested isolates were resistant to tetracycline (MIC ≤ 2 μgml-1), and 98% of the tested isolates were susceptible to spectinomycin (MIC ≤ 64 μgml-1). The MICs for 95% of the isolates, tested for other drugs were: ≤ 2 μgml-1 for cefoxitin, ≤ 0.06 μgml-1 for cefotaxime, ≤ 0.25 μgml-1 for norfloxacin, ≤ 10 μgml-1 for cephaloridine, ≤ 10 μgml-1 for cephalexin, and ≤ 50 μgml-1 for kanamycin. Antibiotic resistance among N. gonorrhoeae isolates from Tucumán, Argentina, appeared to be primarily limited to penicillin and tetracycline, which has been a general use against gonorrhoeae in Tucumán since 1960. Periodic monitoring of the underlying susceptibility profiles of the N. gonorrhoeae strains prevalent in areas of frequent transmission may provide clues regarding treatment options and emerging of drug resistance.