Screening for Carbapenemases in Ertapenem-Resistant Enterobacteriaceae Collected at a Tunisian Hospital Between 2014 and 2018.

Background: Carbapenem-resistance is frequently detected in Enterobacteriaceae isolated from patients in Tunisia. The study was performed to identify frequent carbapenemases in Tunisian isolates.

Methods: Between May 2014 and January 2018, 197 ertapenem-resistant Enterobacteriaceae were isolated at the microbiological department of the Military Hospital of Tunis. The strains were phenotypically characterized and then subjected to in-house polymerase chain reaction (PCR) targeting the carbapenemase genes bla_IMP, bla_VIM, bla_NDM, bla_SPM, bla_AIM, bla_DIM,bla_GIM, bla_SIM, bla_KPC, bla_BIC , and bla_OXA-48.

Results: The assessed 197 ertapenem-resistant Enterobacteriaceae from Tunis comprised 170 Klebsiella pneumoniae, 19 Enterobacter cloacae, 6 Escherichia coli, 1 Citrobacter sedlakii, and 1 Enterobacter asburiae. Thereby, 55 out of 197 isolates (27.9%) were from blood cultures, suggesting a systemic disease. The carbapenemase gene bla_OXA-48 quantitatively dominated by far with 153 detections, followed by bla_NDM with 14 detections, which were distributed about the whole study interval. In contrast, bla_BIC and bla_VIM were only infrequently identified in 5 and 3 cases, respectively, while the other carbapenamases were not observed.

Conclusions: The carbapenemase gene bla_OXA-48 was identified in the vast majority of ertapenem-resistant Tunisian Enterobacteriaceae while all other assessed carbapenemases were much less abundant. In a quantitatively relevant minority of isolates, the applied PCR-based screening approach did not identify any carbapenemases.