Phenotypic and genotypic characterization of antibiotic-resistant Klebsiella spp. from chicken eggshells in traditional and modern markets of Surabaya

Abstract

The emergence of antibiotic-resistant bacteria in food products is a growing public health concern. Among these, Klebsiella spp. are opportunistic pathogens capable of causing severe infections and disseminating antimicrobial resistance genes, including extended-spectrum β-lactamases (ESBLs). This study aimed to evaluate the phenotypic and genotypic profiles of antibiotic-resistant Klebsiella spp. isolated from chicken eggshells in traditional and modern markets of Surabaya, Indonesia. A total of 150 eggshell swab samples were collected across five administrative regions, with equal representation from traditional and modern markets. Presumptive Klebsiella isolates were enriched, cultured on MacConkey agar, and confirmed via Gram staining and biochemical tests. Antibiotic susceptibility was assessed using the Kirby–Bauer disk diffusion method against ampicillin, tetracycline, ciprofloxacin, gentamicin, and sulfamethoxazole–trimethoprim. Multidrug-resistant (MDR) isolates were further analyzed for ESBL-associated genes (blaSHV, blaTEM, blaCTX-M) via PCR. From 150 samples, 28 isolates (18.7%) were confirmed as Klebsiella spp., with similar prevalence in traditional (20.0%) and modern (17.3%) markets. Phenotypic analysis revealed high resistance to ampicillin (78.6%) and lower resistance to other antibiotics. Four isolates (14.3%) were classified as MDR, all recovered from modern markets. Genotypic detection showed that all MDR isolates carried the blaSHV gene, whereas blaTEM and blaCTX-M were absent, indicating SHV-type β-lactamase as the primary determinant of β-lactam resistance. These findings demonstrate that chicken eggs in Surabaya can serve as reservoirs of phenotypically and genotypically antibiotic-resistant Klebsiella, posing potential public health risks. Integrated phenotypic and genotypic surveillance, responsible antimicrobial use in poultry, and improved hygiene practices in both traditional and modern markets are essential to mitigate the spread of multidrug-resistant bacteria through the food chain.