Epidemiological investigation of nosocomial Acinetobacter infections using arbitrarily primed PCR & pulse field gel electrophoresis.

BACKGROUND & OBJECTIVE Nosocomial infections caused by Acinetobacter spp. are a significant problem worldwide. Information on epidemiological investigation of outbreaks caused by Acinetobacter species in India is lacking. The present investigation was carried out to elucidate molecular epidemiology of Acinetobacter species isolated from nosocomial infections in a tertiary care hospital in south India using two DNA-based typing methods. METHODS The medical records of 43 patients with Acinetobacter infection during a period of 24 months were reviewed and Acinetobacter isolates obtained from these patients were characterized phenotypically by assimilation tests and genotypically by arbitrarily primed PCR (AP-PCR) and pulse field gel electrophoresis (PFGE). Susceptibility testing results of the Acinetobacter isolates were also analysed. RESULTS Most of the infections were nosocomial, and the majority of these were acquired in intensive care units (ICUs). A. baumannii accounted for 41.8 per cent (n=18) of all pneumonia acquired in the ICU. AP-PCR with M13 primer distinguished 8 different PCR patterns comprising of 2 to 6 DNA fragments of 0.1 to 1.0 kb. PFGE identified 9 distinct profiles with five subvarients. By APPCR, epidemiologically unrelated strains could not be differentiated and often differences within biotypes of A. baumannii were not detectable. ApaI macrorestriction (PFGE) identified at least 4 outbreaks caused by 3 clones of A. baumannii and one clone of DNA group 13TU, one replacing the other in a well-defined temporal order. INTERPRETATION & CONCLUSION Most of A. baumannii isolates were multidrug resistant. PFGE was more discriminatory [Discriminatory Index (DI)=0.96 than AP-PCR fingerprinting (DI=0.88)] in the present study. However, AP-PCR fingerprinting is more useful as a simple and rapid identification technique for epidemiological investigation of nosocomial Acinetobacter infections.