Phenotypic Distribution of Serine- and Zinc-Type Carbapenemases Among Clinical Bacterial Isolates in a Tertiary Hospital in Benin, Nigeria

Background: Serine and zinc type carbapenemases are distributed in many genera of bacteria and are typically associated with specific regions or countries. Objectives: This study phenotypically determined the prevalence of serine and zinc-type carbapenemases among Gram-negative bacilli recovered from clinical specimens in Benin, Nigeria. Materials and Methods: Totally, 158 consecutive non-duplicate bacterial isolates (gram-negative bacilli) recovered from clinical samples were screened for serine and zinc-type carbapenemases using the simplified carbapenemase inactivation (sCIM) and ethylenediaminetetraacetic acid -double-disc synergy test methods. Results: The isolates recovered from clinical specimens included 126 Enterobacteriaceae (79.7%), 7 Acinetobacter spp (3.7%), and 28oxidase positive gram negative bacilli (17.7%). Twenty-eight isolates (17.7%) out of the 158 tested samples were carbapenemase positive. There was no significant difference in the prevalence of serine- and zinc-type carbapenemases (P=0.0748). However, the prevalence of zinc-type carbapenemase was significantly higher in Pseudomonas aeruginosa compared with other isolates (P=0.0028) while that of serinetype carbapenemase was not affected by the type of clinical isolates (P=0.7216). Finally, the prevalence of both serine- and zinc-type carbapenemases were not affected (P>0.05) by clinical specimens and the source of isolates (in-patient vs. out-patient) respectively. Conclusion: In general, the prevalence of zinc-type (12%) carbapenemases was insignificantly higher than that of serine-type (5.7%) carbapenemases. The measures to reduce infections caused by carbapenemase-producing organisms (CPOs) are advocated accordingly.