ArticleBMC microbiology2026
Distribution of extended-spectrum β-lactamases (blaSHV, blaTEM, blaCTX-M) and AmpC β-lactamases -encoding genes among second- and third-generation cephalosporin-resistant Escherichia coli clinical isolates in Sana'a, Yemen.
Article in BMC microbiology, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
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Abstract
backgroundThe global dissemination of extended-spectrum β-lactamases (ESBL) and AmpC β-lactamases among Escherichia coli poses a therapeutic challenge, contributing to the failure of empirical broad-spectrum antibiotic regimens. In conflict-affected and resource-limited settings like Yemen, the lack of molecular surveillance compromises infection control. This study aimed to determine the genotypic distribution of ESBL-, AmpC-, and dual-producing E. coli isolates resistant to second- and third-generation cephalosporins (specifically, ceftazidime, cefotaxime, or cefoxitin) across major health centers in Sana'a, Yemen.
methodsA cross-sectional study was conducted enrolling 222 non-duplicate, consecutive clinical E. coli isolates that demonstrated phenotypic resistance or reduced susceptibility to second- and third-generation cephalosporins during routine diagnostic screening. Isolates were collected from Al-Yemen Al-Saeed Hospital, Modern European Hospital, and the National Center of Public Health Laboratories (NCPHL). Species confirmation was performed using standard biochemical profiling and the VITEK 2 automated system. Antimicrobial susceptibility testing followed CLSI criteria. Phenotypic production of ESBL and AmpC was validated using the Double-Disk Synergy Test (DDST) and boronic acid inhibition assays, respectively. Target resistance genes (blaSHV, blaTEM, blaCTX-M, blaMOX, blaCIT, blaDHA, blaACC, blaEBC, and blaFOX) were characterized via conventional multiplex polymerase chain reaction (PCR). Statistical analyses were performed using descriptive data and Pearson's chi-square (χ²) tests.
resultsOf the 222 cephalosporin-resistant isolates, 112 (50.5%) were phenotypic ESBL-producers, 90 (40.5%) were AmpC-producers, and 20 (9.0%) were dual (ESBL+AmpC) co-producers. Anatomical specimen tropism was observed (χ² = 40.8, P = 0.001); ESBL-only producers significantly clustered in urinary tract infections (58.0%, adjusted residual = + 5.1), whereas AmpC-producers dominated wound infections (40.0%, adjusted residual = + 5.0). Genotypically, blaCTX-M was predominant in the ESBL group (107/112, 95.5%), while blaEBC (50.0%) and blaFOX (37.8%) were predominant in the AmpC group; blaEBC was also most common (55.0%) in dual-producing isolates. Carriage of at least one ESBL or AmpC gene was detected in 90.5% (201/222) of isolates. Phenotypic carbapenem resistance was observed in 14.4% of AmpC isolates (imipenem) and 20.0% of dual-producing isolates.
conclusionsThis study describes the distribution of ESBL and AmpC β-lactamases among clinical E. coli isolates resistant to second- and third-generation cephalosporins in Sana'a, Yemen, with blaCTX-M and blaEBC being the most frequently detected genes. A high proportion (90.5%) of isolates harbored at least one β-lactamase gene. The distinct associations of ESBLs with urine and AmpC with wounds support the need for targeted revisions to antibiotic stewardship. Furthermore, the detection of carbapenem resistance in AmpC and dual-producing strains highlights the need for molecular surveillance to monitor resistance trends in Yemeni clinical settings.
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