Characterization of ESBL (SHV-12) producing clinical isolate of Enterobacter aerogenes from a tertiary care hospital in Nigeria

Abstract

Background: We studied the beta-lactamases of an E. aerogenes isolate recovered from the blood of a two-year-old patient. The isolate demonstrated a disk-diffusion phenotype typical for an AmpC-ESBL co-producer.

Methods: Microbiology studies were performed according to standard protocols. The resistance gene was identified by transconjugation and cloning experiments.

Results: By transconjugation only a narrow spectrum beta-lactamase (TEM-1) encoded on a small plasmid was transmitted. The ESBL was cloned and expressed in an E. coli host. Sequence analysis of the recombinant plasmid revealed blaSHV-12 associated to the insertion sequence, IS26.

Conclusion: This is the first study demonstrated the occurrence of SHV-12 in Nigeria.

Figure 1

The schematic map of the cloned insert (5656 bp). ORFs are indicated by empty arrows and repeat regions by dark shaded boxes.

Figure 2

IEF in ampholyte gradient of pH 3 to 10 with crude extracts. Lane 1, enzymes (pIs, 5.4 & ≈ 9.0) from E. aerogenes (EaN146); lane 2, enzyme (pI 8.2) from the clone (CN146) and lane 3, enzymes (pIs, 5.4 & ≈ 8.9) from the transformant (TN146). The enzymes at pI 9 in lane 1 and pI 8.9 in lane 3 represented chromosomal enzymes (AmpC).