Abstract
We studied the presence of extended spectrum beta lactamases (ESBLs) in 44 clinical isolates of Escherichia coli collected from out-patients in two university teaching hospitals in South-Eastern Nigeria. Species identification was performed by standard microbiology methods and re-confirmed by MALDI-TOF technology. Phenotypic characterization of ESBL enzymes was done by double disc synergy test and presence of ESBL genes was determined by specific PCR followed by sequencing. Transfer of plasmid DNA was carried out by transformation using E. coli DH5 as recipient strain. Phenotypic characterization identified all isolates to be ESBL positive. 77% of strains were from urine, 13.6% from vaginal swabs and 9.0% from wound swabs. 63.6% were from female patients, 68% were from outpatients and 95.5% from patients younger than 30 years. All ESBL producers were positive in a PCR for blaCTX-M-1 cluster, in exemplary strains blaCTX-M-15 was found by sequencing. In all strains ISEcp1 was found upstream and ORF477 downstream of blaCTX-M. PCR for blaTEM and blaOXA-1 was positive in 93.1% of strains, whereas blaSHV was not detected, aac(6′)-Ib-cr was found in 97.7% of strains. RAPD analysis revealed seven different clonal groups named A through G with the majority of the strains (65.9%) belonging to clone A. Transfer of an ESBL plasmid with co-resistance to gentamicin, kanamycin, tobramycin, doxycycline and trimethropim-sulfamethoxazole was successful in 19 (43.2%) strains. This study showed a high rate of CTX-M-1 cluster - ESBLs in South-Eastern Nigeria and further confirms the worldwide spread of CTX-M ESBL in clinical isolates.
Highlights
Microbial resistance is a growing major public health issue and a strong concern for the medical community
We investigated the molecular epidemiology of clinical isolates of extended spectrum beta lactamases (ESBLs) producing Escherichia coli isolated from outpatients in South-Eastern Nigeria
All 44 E. coli strains were phenotypically confirmed as ESBL, PCR for blaCTX-M and blaCTX-M-1 cluster was positive in all strains
Summary
Microbial resistance is a growing major public health issue and a strong concern for the medical community. Production of β-lactamases is a major means by which Gram-negative bacteria exhibit resistance to β-lactam antibiotics [1]. Extended spectrum β-lactamases (ESBLs) are a group of enzymes that can hydrolyze a variety of β-lactams including cephalosporins like ceftazidime, cefotaxime, ceftriaxone and monobactams like aztreonam in addition to penicillins but do not hydrolyze cephamycins like cefoxitin. Most of the ESBLs have identified namely the CTX-M-1, CTX-M-2, CTX-M-8, CTX-M-9, and CTX-M-25 clusters. CTX-M-14 belonging to the CTX-M-9 cluster and CTX-M-15 belonging to the CTX-M-1 cluster are associated with community-acquired isolates.
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