Sequence analysis of genes mediating extended-spectrum beta-lactamase (ESBL) production in isolates of Enterobacteriaceae in a Lagos Teaching Hospital, Nigeria

BACKGROUND Extended-spectrum β-lactamases (ESBLs) in Gram-negative organisms is now a major concern in Enterobacteriaceae worldwide. This study determined a point-prevalence and genetic profiles of ESBL-producing isolates among members of the family Enterobacteriaceae in Lagos State University Teaching Hospital Ikeja, Nigeria. METHODS Consecutive non-repetitive invasive multidrug-resistant isolates of the family Enterobacteriaceae obtained over a period of 1 month (October 2011) were studied. The isolates were identified using VITEK-2/VITEK MS Systems. Susceptibility testing was performed using E test technique; results were interpreted according to the criteria recommended by the Clinical and Laboratory Standards Institute (CLSI, 2012). ESBL production was detected by E test ESBL method and confirmed by polymerase chain reaction (PCR). RESULTS During the one-month study period, 38 isolates with ESBL phenotypic characteristics were identified and confirmed by PCR. Of these, 21 (55.3 %) were E. coli, 12 (31.6 %) K. pneumoniae, 3 (7.9 %) Proteus spp., 1 (2.6 %) each M. morganii and C. freundii. Thirty (79 %) harbored bla CTX-M genes. Sequence analysis revealed that they were all bla CTX-M-15 genes. Twenty-nine (96.7 %) of these, also harbored bla TEM genes simultaneously. All the CTX-M-15-producing isolates carried insertion sequence bla ISEcP1 upstream of bla CTX-M-15 genes. The E. coli isolates were genetically heterogeneous, while the K. pneumoniae had 98 % homology. CONCLUSIONS Our point-prevalence surveillance study revealed a high prevalence of Enterobacteriaceae isolates harboring bla CTX-M-15 in the Hospital. Urgent implementation of antibiotic stewardship and other preventive strategies are necessary at this time in our hospital.