Carbapenem-resistance in Acinetobacter baumannii: prevalence, antibiotic resistance profile and carbapenemase genes in clinical and hospital environmental strains.

Background: Acinetobacter baumannii, a Gram-negative member of the ESKAPE pathogen group, is known to develop resistance to several antibiotics rapidly, and carbapenem-resistant A. baumannii (CRAB) is highly implicated in life-threatening infections, especially within hospital settings.

Objective: This study detected CRAB in clinical and hospital-environmental samples, evaluated the antibiotic resistance patterns and screened for prevalent carbapenemase genes in isolates from a hospital in Southwest Nigeria.

Methods: A total of 150 clinical and hospital environmental samples were analysed using culture-dependent and molecular methods for the detection of Acinetobacter baumannii. Antibiotic susceptibility test was done using the Kirby-Bauer disk diffusion technique. Phenotypic screening for carbapenemase was via simplified carbapenem inactivation method (sCIM), and molecular detection of blaKPC type, blaOXA-48-like, blaVIM type, blaNDM-1, blaIMP variants and blaOXA-23-like genes by Polymerase chain reaction.

Results: Altogether, only 29.4% (42/143 isolates) of recovered isolates were identified as A. baumannii, giving a prevalence of 28.0% (42/150 samples), predominantly from sputum. All isolates had the gluconolactonase gene, while 5/42 had the blaOXA-51-like gene. Resistance to meropenem and cefiderocol was 100.0% and 88.1%, respectively, while gentamicin was most effective in vitro (7.1%); 54.8% were multidrug-resistant, and 88.1% (37/42) had MARI ≥ 0.2. Overall, 39/42 (92.9%) isolates had ≥ one or more carbapenemase genes; 61.9% (26/42) had the blaKPC type gene, 59.5% (25/42) had the blaIMP variants while 45.2% had the blaVIM type gene; no strain had the blaNDM-1 or the blaOXA-23-like gene.

Conclusions: This study reports the occurrence of MDR strains, and of blaKPC type, blaIMP variants and blaVIM type carbapenemase genes in A. baumannii isolates from clinical and hospital environmental samples, contributing to the pool of existing data on their occurrence. It also highlights the need for monitoring and continued surveillance of the strains, most especially in the clinical setting.