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

Serine and zinc type carbapenemases are distributed in many genera of bacteria and are typically associated with specific regions or countries.

This study phenotypically determined the prevalence of serine and zinc-type carbapenemases among Gram-negative bacilli recovered from clinical specimens in Benin, Nigeria.

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.

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.

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.