Delayed identification of Acinetobacter baumannii during an outbreak owing to disrupted bla by ISAba19.

Early detection of Acinetobacter baumannii, an emerging pathogen in hospital settings, is of interest. The bla family had been used as a marker to detect A. baumannii. During an infection outbreak, 14 isolates produced a 1.7-kb PCR band instead of 353 bp for this marker. This work sought the reasons behind the increased marker size. Characterisation of isolates was done by API-20NE, gyrB multiplex PCR and 16S-23S rRNA ITS sequencing. The 1.7-kb band generated and the complete bla variant were sequenced to find the probable integrated element. Susceptibility testing to various antimicrobials was performed by microdilution. bla, metallo-β-lactamases (MBLs), the ISAba1 element and the presence of ISAba1 adjacent to bla were sought. rep-PCR, global clonal (GC) lineage determination and multilocus sequence typing (MLST) were performed to analyse the relationship among isolates. Isolates were characterised as Acinetobacter baumannii-calcoaceticus complex by API-20NE. gyrB multiplex PCR and 16S-23S ITS sequencing verified the isolates as A. baumannii. Sequencing of the 1.7-kb band revealed ISAba19 as the disrupting element. The bla variant was bla, which was elongated to 2.2 kb due to ISAba19. The bla family was found in 67% of isolates. MBL genes were not detected; however, ISAba1-bla was characterised in carbapenem-resistant isolates (53%; 8/15). Isolates were divided into three clusters by rep-PCR. All strains were ST2 and all but one belonged to GC II. Identification of A. baumannii based only on bla is not reliable. Besides bla, multiplex PCR of gyrB and rpoB could provide rapid and cost-effective results.