Molecular Characterization and Antibiotic Resistance of Broad-Spectrum β-Lactamase-Producing Enterobacterales in...

The effectiveness of antibiotic therapy for urogenital tract infections (UTIs) is increasingly compromised by the global dissemination of extended-spectrum β-lactamase-producing Enterobacterales (ESβL-En). This study aimed to assess the involvement of broad-spectrum β-lactamase-producing Enterobacterales (BSβL-En) in UTIs and to establish their antibiotic susceptibility profile.

A cross-sectional study was conducted from October to December 2019 at the Army Training Hospital Omar Bongo Ondimba. All patients suspected of having a UTI were included. BSβL-En isolates were recovered using MacConkey agar supplemented with cefotaxime. Phenotypic screening for β-lactamase (ESβL, AmpC, and carbapenemases) using specific phenotypic confirmatory disc diffusion test. Antimicrobial susceptibility was determined using the disk diffusion method and minimum inhibitory concentration (MIC) assays. The presence of resistance genes (bla _CTX-M, bla _TEM, bla _CARBA, bla _IMP, mcr-1 and mcr-2) was investigated by polymerase chain reaction.

A total of 295 patients were enrolled, among whom 18.3% (54/295) had UTIs. Of the isolated uropathogens 74.1% were BSβL-En. The predominant species were Enterobacter cloacae (8/54, 14.8%), Escherichia coli (6/54, 11.1%) and Kluyvera spp (5/54, 9.3%). Among 40 BSβL-En isolates, 87.5% (n = 35/40) were confirmed by molecular analysis. Notably 48.5% (17/35) harbored at least two bla genes, simultaneously. Fourteen isolates carried the bla _CARBA and bla _IMP genes, which in combination with the bla _CTX-M and bla _TEM. About 40.0% of the isolates (14/35) carried the bla _CTX-M, 8.6% had the bla _TEM (3/35), and 2.9% had the bla _IMP (n = 1/35). All urinary isolates were multidrug-resistant (MDR), exhibiting high levels of β-lactamase production, with resistance rates of 81.6% ± 0.16% for first-line antibiotics (e.g., β-lactams, fluoroquinolones) and 61.7% ± 0.04% for last-resort antibiotics (e.g., imipenen, ertapenem, and colistin). The prevalence of carbapenem resistance genes was 44.1%, whereas no colistin resistance genes (mcr-1 and mcr-2) were detected.

This study highlights a high prevalence of multidrug-resistant uropathogens producing BSβL, with significant resistance to both first-line and last-resort antibiotics.