Rapid identification of Acinetobacter baumannii, Acinetobacter nosocomialis and Acinetobacter pittii with a multiplex PCR assay.

Acinetobacter baumannii, Acinetobacter nosocomialis and Acinetobacter pittii are clinically relevant members of the Acinetobacter calcoaceticus-A. baumannii (Acb) complex and important nosocomial pathogens. These three species are genetically closely related and phenotypically similar; however, they differ in their epidemiology, antibiotic resistance and pathogenicity. In this study, we investigated the use of a multiplex PCR-based assay designed to detect internal fragments of the 16S-23S rRNA intergenic region and the gyrB and recA genes. The assay was capable of differentiating A. baumannii, A. nosocomialis and A. pittii in a reliable manner. In 23 different reference strains and 89 clinical isolates of Acinetobacter species, the assay accurately identified clinically relevant Acb complex species except those 'between 1 and 3' or 'close to 13TU'. None of the non-Acb complex species was misidentified. In an analysis of 1034 positive blood cultures, the assay had a sensitivity of 92.4 % and specificity of 98.2 % for Acb complex identification. Our results show that a single multiplex PCR assay can reliably differentiate clinically relevant Acb complex species. Thus, this method may be used to better understand the clinical differences between infections caused by these species.