Co-occurence of blaNDM-1 and blaOXA-23 or blaOXA-58 in clinical strains of Acinetobacter baumanii

Ramoul. A*1,2, Rolain. J-M2

1 : Département de Biochimie, Université Badji Mokhtar. Annaba 23000, Algérie.
2 : Unité de recherche sur les maladies infectieuses et tropicales émergentes (URMITE), UM 63, CNRS 7278, IRD 198, INSERM 1095, IHU Méditerranée Infection, Faculté de Médecine et de Pharmacie, Aix-Marseille- Université, Marseille, France

Infections by carbapenem-resistant Acinetobacter baumannii are a growing global issue.

Objective: The objective of this study was to evaluate the rate of antibiotic resistance, the transfer of antibiotic resistance genes, and molecular epidemiology of clinical strains of Acinetobacter baumannii.

Material and Methods: Forty-three clinical strains of A. baumannii were identified using API20NE and MALDI-TOF MS. Antibiotic susceptibility tests were carried out using agar diffusion assays and the E-test. Molecular identification of the strains was performed by real-time PCR, followed by sequencing of the positive genes. Conjugation assays determined the transferability of carbapenem resistance genes.

Results and discussion: All 43 isolates were imipenem-resistant, with mean Minimum Inhibitory Concentrations (MICs) ≥ 32 µg/mL. Among these strains, twenty-five isolates carried the blaOXA-23 gene, seven carried the blaNDM-1 gene, six carried the blaOXA-58 gene and one carried the blaOXA-24 gene. Transfer of plasmid NDM-1 to E. coli J 53 was successful for one of three strains carrying blaNDM-1 and blaOXA-23 genes.

Conclusion: The phylogenetic tree obtained by concatenating csuE and blaOXA-51 partial gene sequences showed no genetic relationship between these isolates and the resistance gene blaNDM-1. However, the blaOXA-23 gene is spreading into bronchial aspiration isolates.