Background. The emergence of multidrug and extensive drug resistant strains of Acinetobacter baumannii‎ is a multifactorial consequence. Carbapenems, once considered the traditional standard of care for Acinetobacter infections however, are gradually being curtailed from the therapeutic regime due to the emergence of Carbapenem resistant Acinetobacter baumannii‎ (CRAB). Several carbapenem resistant mechanisms have been postulated for the rise of CRAB. This study investigated clinical A.baumannii isolates for the presence and level of expression of enzymatic and non-enzymatic genes, putatively associated with carbapenem resistance and their association with sequence typing. Methods. Uniplex, and Multiplex PCR were performed to identify the presence of oxacillinase (OXA) and metallo β-lactamase (MBLs) genes respectively. The level of expression of efflux pumps (adeB and adeJ) and porins (carO, omp33-36 and oprD) was investigated by Real-time PCR. Results. Of the 112 isolates obtained during this study, 100% were multidrug-resistant and 48.2% were extensive drug-resistant A.baumannii. All CRAB isolates harbored blaOXA−51−like, while, 82.1% and 63.4% of these isolates carried blaOXA−23−like and blaOXA−24/40−like genes, respectively. In contrast, the frequency of metallo β-lactamase genes was comparatively less than the oxacillinase genes. Over-expression of adeB and adeJ was observed in 66% and 42.8% A.baumannii strains respectively, while, decreased expression of carO, omp33-36 and oprD was observed in 75%, 66% and 72.3% strains respectively. Conclusion. Consistent with that reported by others, our study highlights the significant dissemination of the oxacillinase, blaOXA−23−like in CRAB isolates, particularly the simultaneous occurrence of blaOXA−23−like with blaOXA−40. Interestingly, while changes in the expression of efflux pumps and porins were observed nevertheless, more in depth investigation is required to decipher their contribution to carbapenem resistance in these strains.

Introduction:Acinetobacter baumannii infections are a growing public-health concern. The bacterium’s potentiality to acquire resistance to a number of commonly used antibiotics has turned it into a formidable pathogen. Aims: Molecular characterization of extensive drug resistant (XDR) typing of A. baumannii clinical isolates by polymerase chain reaction. Materials and methods: Thirty XDR A. baumannii were investigated for the presence of genes encoding carbapenemase resistance, biofilm capacity, autoinducer synthase, virulence and surface motility by polymerase chain reaction (PCR). Later, the isolates were typed by plasmid-based replicon (Rep) (PBRT) and trilocus sequence typing. Results: All 30 XDR A. baumannii strains displayed genes related to surface motility, autoinducer synthase, virulence determinant, biofilm related genes except PER, and bap, the frequency of which was 83.3% and 76.6%, respectively. Analysis of rep genes showed highest frequency of rep6 and rep2 genes, with frequency of 75% and 65%, respectively. All XDR A. baumannii strains belonged to SG I (European clone II) group. Conclusions: Our results show the extraordinary plasticity of XDR A. baumannii and suggest that the strains have gained endemicity in our hospital, which could be a great concern in the near future.