Molecular characterisation of extended-spectrum β-lactamase-producing Gram-negative bacterial isolates from surgical wounds of patients at a hospital in North Central Nigeria.

OBJECTIVES: This study aimed to characterise extended-spectrum β-lactamase (ESBL)-producing Gram-negative bacterial isolates from patients with surgical site infections (SSIs) at a tertiary healthcare facility in Abuja, Nigeria.

METHODS: Consecutive, non-duplicate wound swabs were collected over a 3-month period from wounds of patients with SSI and were cultured appropriately. Bacterial isolates were identified using rapid identification kits. The modified agar disk diffusion method was used for antimicrobial susceptibility testing, and phenotypic ESBL activity of the isolates was determined using the double-disk synergy test (DDST). PCR was thereafter used for molecular characterisation of the isolates.

RESULTS: A total of 57.1% (20/35) of the bacterial isolates were Gram-negative, with Pseudomonas aeruginosa (7/20; 35.0%) being the most prevalent. The isolates exhibited varying degree of antimicrobial resistance, with resistance as high as 100% for ampicillin and amoxicillin. Phenotypic ESBL production was observed in 65.0% (13/20) of the Gram-negative bacterial isolates. DNA analysis revealed that 61.5%, 53.8% and 38.5% of the isolates harboured blaSHV , blaCTX-M and blaTEM genes, respectively, with 30.8% of the isolates co-harbouring blaSHV and blaCTX-M . Similarly, 23.1% of the isolates harboured blaSHV and blaTEM , whilst 15.4% harboured blaCTX-M and blaTEM . However, none of the investigated isolates harboured a blaOXA gene.

CONCLUSION: The prevalence of ESBL genes among Gram-negative SSI pathogens is high. This calls for an urgent need to review infection control policies and antimicrobial prescription patterns as well as increased surveillance of ESBLs as the possibility of an epidemic outbreak of multidrug-resistant pathogens in the hospital is high.