Susceptibilities of invasive Neisseria meningitidis strains to agents used for prophylaxis and to penicillin G.

Background The antimicrobial susceptibility of isolates of Neisseria meningitidis to agents used for chemoprophylaxis and to penicillin G was determined. Methods Fifty N. meningitidis strains detected in Nova Scotia between 2004 and 2018 were included. The isolates were originally isolated from sites that might prompt chemoprophylaxis (27 blood, 18 cerebrospinal fluid [CSF], 3 CSF-blood, and 2 conjunctiva). Minimal inhibitory concentrations (MICs) were determined to azithromycin, ciprofloxacin, minocycline, rifampin, trimethoprim-sulfamethoxazole, and penicillin G, using a diffusion gradient strip on Mueller-Hinton agar with 5% sheep blood in 5% CO2 for 20-24 hours. Results All isolates remained susceptible to azithromycin, ciprofloxacin, minocycline, and rifampin, but there was 26% resistance to trimethoprim-sulfamethoxazole. There was a rise in penicillin MIC of the isolates over the study period. Conclusion In our province, N. meningitidis isolates causing invasive infection remain susceptible to commonly used antimicrobial agents used for chemoprophylaxis. Significant resistance to trimethoprim-sulfamethoxazole is present and the degree of susceptibility to penicillin G is lessening.