Detection of blaOXA-23-like and blaNDM-1 in Acinetobacter baumannii from the Eastern Region, Saudi Arabia

Abstract

Acinetobacter baumannii is currently considered as one of the most common successful pathogens in the healthcare system due to its ability to quickly develop resistance. Ten carbapenem-resistant A. calcoaceticus-baumannii complex were isolated from the eastern region, Saudi Arabia in 2014. All isolates were resistant to ciprofloxacin, however, 8 of 10 isolates were tigecycline resistant. Susceptibility test was also carried out for three aminoglycosides, resistance to gentamicin was 80%, amikacin was 90%, and tobramycin was 50%. Colistin susceptibility was seen in all isolates. The 10 isolates harbored bla_OXA-23-like and ISAba1 and 9 of them also carried bla_ADC. Three isolates of 10 harbored bla_NDM-1 coding for NDM metallo-β-lactamase (MBL) with coexistence of bla_ADC together with either bla_GES or bla_TEM or both. Those three isolates exhibited negative Etest MBL screening test. Pulsed-field gel electrophoresis revealed the high clonal variability of the isolates, although two isolates were indistinguishable. The risk of dissemination of carbapenem resistance through presence of ISAba1 upstream of OXA-23-like in all isolates raises the concern about emergence of higher carbapenem prevalence rates in the future in our region. This study also demonstrated the importance of molecular surveillance to provide accurate and reliable data about the resistance rates of A. baumannii. Finally, the high incidence of NDM-1 among our isolates requires a routine surveillance to monitor the future prevalence of this enzyme in the region.

Keywords: Acinetobacter baumannii; Saudi Arabia; carbapenem resistance; β-lactamase.