Neisseria gonorrhoeae antimicrobial susceptibility in Lilongwe, Malawi, 2007

Malawi adopted syndromic management of sexually transmitted infections in 1993. Based on clinical efficacy and cost, gentamicin 240 mg intramuscularly, and doxycycline 100 mg twice daily x 7 days was selected as the first line regimen to treat urethritis. We sought to establish current laboratory-based Neisseria gonorrhoeae antibiotic susceptibility patterns for Malawi and describe the pattern of susceptibility since syndromic management began.

Between May 15 and August 10, 2007, 126 men with urethritis attending the STD clinic at Kamuzu Central Hospital in Lilongwe had history, genital exam, and urethral swabs taken. All were treated with gentamicin and doxycycline in accordance with Malawi guidelines. Gonorrhea was diagnosed by Gram stain and culture. Antimicrobial susceptibility patterns in gonococcal isolates were determined by disk diffusion and E-test minimum inhibitory concentration (MIC) determination and agar dilution MIC determination.

One hundred six isolates were cultured, and MICs were determined for 100. High levels of resistance to tetracycline and penicillin were observed, but isolates were uniformly susceptible to both gentamicin and ciprofloxacin. Susceptibility patterns identified by the agar dilution MIC and E-test MIC agreed.

The most recent study continues the trend of high susceptibility of gonococcal isolates to gentamicin in Malawi after 14 years of use and suggests agar dilution MICs may be substituted with the simpler E-test methods in future susceptibility testing. However because of the lack of susceptibility criteria for aminoglycosides for N. gonorrhoeae and the difficulty obtaining clinical/in vitro correlates in this setting, caution should be exercised in using these data for modifying treatment regimens.