Phenotypic Antibiotic Resistance Profiles of Clinical Escherichia coli and Klebsiella pneumoniae Isolates from Cameroon: Prevalence of ESBL, Carbapenemase, and Multidrug Resistance

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The emergence of multidrug-resistant (MDR) Enterobacteriaceae, especially Escherichia coli and Klebsiella pneumoniae, is a critical public health threat in sub-Saharan Africa. In Cameroon, irrational antibiotic use and limited surveillance increase the spread of resistance. This study aimed to determine the phenotypic antibiotic susceptibility profiles of clinical isolates of E. coli and K. pneumoniae and to assess the magnitude of ESBL and carbapenemase production. A total of 130 clinical isolates (100 E. coli, 30 K. pneumoniae) were re-identified by standard biochemical tests. Antibiotic susceptibility was tested by the disk diffusion method on Mueller-Hinton agar using 12 antibiotics (imipenem, meropenem, amoxicillin-clavulanate, cefepime, cefotaxime, ceftazidime, aztreonam, amikacin, gentamicin, ciprofloxacin, ofloxacin, nalidixic acid) according to EUCAST 2023 guidelines. ESBL and carbapenemase production were detected phenotypically. The multiple antibiotic resistance (MAR) index was calculated, and isolates were classified as MDR or XDR based on resistance to ≥ 3 or all - but - ≤ 2 antimicrobial categories, respectively. All isolates showed resistance to at least one antibiotic. Resistance to third-generation cephalosporins was alarmingly high: in E. coli, cefotaxime 85%, ceftazidime 92%, cefepime 90%; in K. pneumoniae, cefotaxime 90%, ceftazidime 100%, cefepime 90%. Carbapenem resistance was observed in 37% (E. coli) and 20% (K. pneumoniae) for meropenem, and 24% (E. coli) and 17% (K. pneumoniae) for imipenem. ESBL production alone was found in 50% of E. coli isolates (17/34 enzyme producers), while carbapenemase alone in 18% (6/34) and ESBL+ carbapenemase co-production in 14% (5/34). In K. pneumoniae, 90% were ESBL producers, and 17% produced carbapenemase. The MAR index ranged from 0.25 to 0.75 for E. coli and 0.33 to 0.83 for K. pneumoniae. Overall, 80% of E. coli and 86.7% of K. pneumoniae were MDR; XDR strains accounted for 4% of E. coli (4 isolates) and 16.7% of K. pneumoniae (5 isolates). This study reveals extremely high rates of resistance to cephalosporins, significant carbapenem resistance, and widespread MDR/XDR phenotypes among clinical isolates of E. coli and K. pneumoniae in Cameroon. The high prevalence of ESBL and carbapenemase producers, including co-producing strains, severely limits therapeutic options. Urgent interventions, such as antimicrobial stewardship and exploration of alternative therapies like medicinal plants, are necessary.

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