Use of different PCR-based DNA fingerprinting techniques and pulsed-field gel electrophoresis to investigate the epidemiology of Acinetobacter calcoaceticus-Acinetobacter baumannii complex

Abstract

Acinetobacter calcoaceticus-Acinetobacter baumannii complex is an important nosocomial pathogen for which optimal typing methods in epidemiologic investigations have not been defined. We compared DNA macrorestriction analysis by pulsed-field gel electrophoresis (PFGE) with different PCR-based DNA fingerprinting techniques, including enterobacterial repetitive intergenic consensus (ERIC) polymerase chain reaction (PCR), repetitive extragenic palindromic (REP) PCR, arbitrary-primed PCR with primer M13, and multiplex PCR with primers REP-1, REP-2 and M13, for characterization of 98 clinical isolates (including 10 apparent outbreak-related isolates and 68 presumed epidemiologically unrelated isolates) in a tertiary-care hospital over a 4-year period. The PFGE patterns after SmaI restriction of the bacterial DNA were analyzed by computer software (Gelcompar) using the unweighted pair group method with arithmetic averages clustering and the Dice coefficient. A cluster of 48 isolates (cluster A), including 9 outbreak isolates, linked at a level of 83.4% similarity was observed. This epidemic strain and its variants were also found among the 68 presumed epidemiologically unrelated isolates, and this may represent ongoing endemic infection in this institution. The discrimination index for the PCR-based DNA fingerprinting techniques was 0.75 for enterobacterial repetitive intergenic consensus 1, 0.71 for M13, 0.77 for REP-1, 0.77 for REP-2, and 0.87 for multiplex PCR. The discriminatory power of PFGE was found to be higher than those of PCR-based techniques. It was concluded that both PFGE and PCR-based fingerprinting are useful for typing of A. calcoaceticus-A. baumannii complex. However, PFGE can detect minor mutations among outbreak strains, and this is important for epidemiological study of this species in a complex endemic setting.