Extensively drug-resistant Acinetobacter baumannii co-producing VIM-2 and OXA-23 in intensive care units: Results of a one-day point prevalence in a Tunisian hospital

Abstract

Objective: The main objective of this study was to identify carbapenem resistance mechanisms among clinical, commensal and environmental carbapenem-resistant Acinetobacter baumannii (CRAB) strains isolated in 5 Tunisian intensive care units (ICUs).

Materials and methods: CRAB isolates were recovered from different sources: clinical specimens, rectal and environmental swabs. Bacterial identification was carried out using conventional methods and susceptibility testing according to EUCAST recommendations. Evaluation of phenotypic carbapenemase production of was performed using seven different methods, and molecular detection of carbapenemase-coding genes (bla_OXA23, bla_OXA24, bla_OXA58, bla_NDM, bla_GES, bla_OXA48, bla_IMP, bla_VIM and bla_KPC) was done by PCR. The genetic relationships between CRAB isolates were analyzed by pulsed-field gel electrophoresis.

Results: All in all, 46 CRAB isolates were identified in clinical specimens (n = 26/26), rectal swabs (n = 17/36) and environmental swabs (n = 3/63). Most of them (n = 41/46) were clonally related and found in the different ICUs. All of the CARB isolates harbored bla_OXA-51-like and bla_OXA-23 genes, while bla_VIM-2 gene was detected in 42 isolates (91.3 %). Phenotypic carbapenemase activity was found in all 46 strains, using the CIM-Tris test with 100 % sensitivity for OXA-23 and VIM-carbapenemase detection, thereby justifying its routine use.

Conclusion: The emergence and diffusion of clonal CRAB strains inducing high mortality rates in ICUs is a major public health concern. Enhanced infection control practices and mandatory staff education are needed to control the spread of these multidrug-resistant bacteria.

Keywords: Acinetobacter baumannii; Carbapenem resistance; Intensive care units; VIM-2 and OXA-23.