Comparison of disc diffusion results with minimum inhibitory concentration (MIC) values for antimicrobial susceptibility testing of Neisseria gonorrhoeae.

BACKGROUND & OBJECTIVE objectives: As antimicrobial susceptibility testing of Neisseria gonorrhoeae provides guidance for appropriate treatment, there is a need for simple, reliable and cost-effective method for susceptibility testing. The present study was aimed to compare the results of two methods of susceptibility testing, minimum inhibitory concentration (MIC) values by E test with disc diffusion results by Australian Gonococcal Surveillance Programme (AGSP) method in N. gonorrhoeae isolates. METHODS Susceptibility testing for ciprofloxacin, penicillin and ceftriaxone using AGSP method was carried out for 301 confirmed consecutive isolates of N. gonorrhoeae. MIC of ciprofloxacin, penicillin and ceftriaxone was determined by E test in 301, 198 and 128 isolates respectively. The results of the two methods were compared by using Kappa statistics. RESULTS Moderate levels of agreement for ciprofloxacin (kappa=0.44) and penicillin (kappa=0.54) were observed between the two methods. For ceftriaxone, 96.1 and 0.8 per cent isolates were found to be susceptible and less sensitive respectively by both the methods and per cent agreement between the two methods was 96.9 per cent. INTERPRETATION & CONCLUSION Both the methods were easy to perform and gave reproducible results. However, disc diffusion method was cost-effective and more feasible in routine diagnostic laboratories in developing countries like India.