Extended-spectrum Beta-lactamase Orthopedic Wound Infections in Nigeria

Extended-spectrum beta-lactamase (ESBL)-producing Gram-negative bacteria are emerging and impacting significantly on the management of patients and hospital costs. Besides, they are not being routinely sought after in diagnostic laboratories thus contributing to treatment failure.

Bacterial isolates from wounds of 45 patients were identified using commercial identification kits and antibiotic susceptibility was evaluated by the Bauer-Kirby method. Screening and phenotypic confirmation of ESBL production were done as prescribed by the Clinical and Laboratory Standards Institute. The conjugation experiment was performed by the mating assay in broth between the ESBL producers and E. coli ATCC 25922 as the recipient.

Out of 102 Gram-negative bacteria isolated, 36 were positive for ESBL mainly of the Enterobacteriaceae family (33) and the rest were oxidase-positive bacilli (3). The predominant bacteria were Klebsiella spp. and E. coli. Others were Serratia rubidae, Citrobacter freundii, Morganella morgannii, Proteus spp., Providencia stuartii, and Enterobacter spp. There was a significant association between treatment with third-generation cephalosporins (3GCs) and isolation of ESBLs (P=0.0020). The ESBL producers were multiply resistant and moderately sensitive to colistin. The conjugation experiment showed that the ESBL gene was transferred horizontally and tetracycline, cotrimoxazole, nitrofurantoin, gentamicin, and aztreonam resistance genes were co-transferred. No mortality was recorded but the mean length of stay in the hospital was 82 days.

The development and spread of ESBL among Gram-negative bacteria and possible horizontal transfer calls for concern, especially in view of treatment failure, high treatment cost, and consequent discomfort to patients.