Multiplex PCR to detect the genes encoding naturally occurring oxacillinases in Acinetobacter spp.

Objectives: Bacteria of the genus Acinetobacter are increasingly being isolated in hospitals and are recognized as emerging nosocomial pathogens. Species identification is difficult and there is a need for simple molecular methods to differentiate between the species. Naturally occurring oxacillinase genes (bla) have been identified in several Acinetobacter species and their detection by PCR can aid in species identification. The aim of this study was to develop a multiplex PCR to identify intrinsic bla genes (i.e. bla, bla, bla, bla and bla) from Acinetobacter spp. for use as a tool for rapid species identification. Methods: Primers were designed to selectively amplify internal fragments of intrinsic bla from Acinetobacter lwoffii/Acinetobacter schindleri (bla), Acinetobacter johnsonii (bla), Acinetobacter calcoaceticus (bla), Acinetobacter haemolyticus (bla) and Acinetobacter bereziniae (bla). Multiplex PCR was performed in a total of 100 Acinetobacter isolates. Flanking primers were designed for each bla subgroup and products were sequenced. Results: All A. lwoffii, A. schindleri, A. johnsonii, A. calcoaceticus, A. haemolyticus and A. bereziniae isolates were positive for their species-specific amplicons while other Acinetobacter species were negative. Thirty bla novel variants were identified; the majority of these (21/30) were from A. calcoaceticus. ISAba11 was found upstream of bla in four A. haemolyticus isolates, but was not associated with carbapenem resistance. Conclusions: This multiplex PCR specifically detected each of the five different bla subgroups. Therefore, this method has the potential to aid in the identification of these species and monitor the spread of these genes into other Acinetobacter species.