Prevalence of Multidrug-Resistant Escherichia coli O157:H7 from Live Bird Markets in Lagos, Nigeria

1. Introduction

Microbial foodborne illness remains a significant global concern despite extensive scientific and technological advancements. This is particularly true in developing countries, especially in Africa, where poor food handling practices, inadequate food safety laws, and a lack of education for food handlers are prevalent (Haileselassie et al., 2013; Ekpunobi et al., 2024a).

Escherichia coli (E. coli), a gram-negative bacterium which has a significant impact on human and animal health. Most E. coli reside in the large intestine as commensals but can become a dangerous pathogen that promotes intestinal and systemic illnesses under various conditions (Kittana et al., 2018; Chukwunwejim et al., 2025). One of the most significant foodborne pathogens that has received increased attention in recent years is E. coli O157:H7. This enterohemorrhagic strain can cause life-threatening illnesses such as hemorrhagic colitis and hemolytic-uremic syndrome (HUS).

The emergence of antimicrobial resistance (AMR) is a major problem in both human and veterinary medicine. Antimicrobial agents are routinely administered to poultry as antimicrobial growth promoters (AMGP), and the indiscriminate use of these antimicrobials for both therapeutic and preventive purposes could increase the risk of resistance (Hassan, 2021; Obidi and Ekpunobi, 2025). Development of resistance to antimicrobial is a complex phenomenon that involves bacterial genetic and metabolic mechanisms, and it can be expedited due to antibiotic selection pressure (Zhang et al., 2015; Munita and Arias, 2016; Ekpunobi et al, 2025). Due to intensive production, the antibiotic selection pressure for resistance in microorganisms is high, and consequently, their faecal flora contains a comparatively high proportion of resistant microorganisms (van den Bogaard and Stobberingh, 2001; Hassan et al., 2021). Those resistant organisms can transmit into human, animals, and the environment (McEwen and Collignon, 2018; Obidi et al., 2025).

Poultry meat serves as a potential source of human infection, as there is a high chance of contamination with E. coli during food preparation. Studies have shown that broiler meat can contain antimicrobial-resistant coli, which can be transmitted to people through the food chain, representing a possible risk of human infections (Suswati et al., 2025). In Nigeria, where unsanitary conditions and poor health facilities are widespread, there is an urgent need to study this emerging pathogen and its characteristics to reduce human health hazards. The lack of rigorous surveillance for food pathogens presents a challenge in demonstrating the magnitude of contamination with E. coli O157:H7 in the poultry industry. This study aims to generate data to address this gap.

2. Materials and Methods

2.1. Sample Collection

Poultry feces samples were obtained from the Poultry Market in Alaba Market, Lagos State. Aseptic techniques were used to collect fresh chicken feces in sterile 10 ml test tubes containing sterile buffered saline water, which served as a pre-enrichment medium. The samples were transported to the laboratory in a transport bag within one hour for prompt analysis.

2.2. Microbiological Isolation and Identification

Samples were pre-enriched in 9 ml of Tryptic Soy Broth (TSB) and incubated at 37°C for 24 hours. After incubation, 0.1 ml of the pre-enrichment broth was inoculated onto prepared plates of Eosin Methylene Blue (EMB) agar and incubated at 37°C for 24 hours. Medium-sized colonies exhibiting a green metallic sheen were considered to be E. coli and sub-cultured onto Sorbitol MacConkey (SMAC) agar (Oxoid, UK). Colorless colonies (non-sorbitol fermenters) were purified by sub-culturing, twice onto fresh SMAC agar and were considered presumptive E. coli O157. The serogroup O157 of E. coli was determined using a latex agglutination test kit (E. coli O157 latex test, Oxoid^®, UK) as described by the manufacturer.

2.3. Antimicrobial Susceptibility Testing

The confirmed coli O157 isolates were tested for their susceptibility to antimicrobial agents using the agar disc diffusion method, following CLSI guidelines. The following commercially available Gram-negative antibiotic discs were used: ceftazidime (30 μg), cefuroxime (30 μg), gentamicin (10 μg), cefixime (5 μg), ofloxacin (5 μg), amoxicillin (30 μg), nitrofurantoin (5 μg), ciprofloxacin (30 μg).

The antibiotic discs were placed on Mueller Hinton agar plates previously seeded with an overnight culture of the test organisms. The plates were incubated at 37°C for 24 hours, after which the zones of inhibition were measured and interpreted.

3. Results and Discussion

A total of 180 poultry fecal samples were analyzed. Out of these, 105 (58.33%) were identified as Escherichia coli isolates. The isolation process further revealed that 74 (41.11%) of the isolates were non-sorbitol fermenters, and 26 (14.44%) were confirmed as Escherichia coli O157:H7 using the latex agglutination test. The prevalence of E. coli O157:H7 in this study, at (26/180) 14.44%, is quite similar to previously reported findings in Lagos and Ogun state, Nigeria (Aibinu et al., 2007; Olatoye et al., 2012). The study reported a slightly higher prevalence than reports from Ethiopia (13.4%)(Shecho et al., 2017). The variations in prevalence may be due to differences in sampling techniques, geographical areas, and a lack of strict hygiene measures. The high occurrence in indigenous chickens from live bird markets might be explained by the high concentration and interaction of diverse birds from different sources.

The public health implication of the high prevalence of E. coli O157:H7 in indigenous chickens in live bird markets is that, the presence of these pathogenic organisms puts live bird sellers and intermediaries at risk of occupational hazards. Furthermore, pathogenic E. coli from the gut can contaminate chicken meat, posing serious public health problems, including zoonotic transfer to human consumers (Odo et al., 2021; Chukwunwejim et al., 2025).

The antimicrobial susceptibility pattern observed among the 26 E. coli O157 isolates demonstrates an alarming level of multidrug resistance (MDR), with nearly all isolates resistant to third-generation cephalosporins (cefixime, cefotaxime, ceftriaxone), aminopenicillins (amoxiclav), and first-line fluoroquinolones (nalidixic acid, ofloxacin).

FigureF1. Heat map representing antimicrobial susceptibility/resistance in 26 E. coli O157:H7 isolates. The Green color in heat map indicates antibiotic sensitivity and red color indicates antibiotic resistance in the 26 isolates. 

FigureF1. Heat map representing antimicrobial susceptibility/resistance in 26 E. coli O157:H7 isolates. The Green color in heat map indicates antibiotic sensitivity and red color indicates antibiotic resistance in the 26 isolates. 

This finding is consistent with previous reports from Sub-Saharan Africa, where the widespread and often unregulated use of broad-spectrum antibiotics in both human and veterinary practice has driven the rapid emergence of resistant Enterobacteriaceae (Odonkor & Addo, 2018; Ekpunobi and Agu, 2024).

A key observation in this dataset is the near-universal resistance to extended-spectrum cephalosporins (CXM, CTX, CRO), suggesting the potential involvement of extended-spectrum β-lactamase (ESBL) production, which is now increasingly reported in E. coli O157 and other diarrheagenic pathotypes (Paterson & Bonomo, 2005; Ezemba et al., 2022; Ekpunobi et al., 2024b). The resistance to cephalosporins, coupled with high resistance to aminopenicillins (AUG), leaves very limited therapeutic options for empirical treatment in resource-limited settings such as Nigeria.

Interestingly, imipenem (a carbapenem) retained moderate activity, with approximately 40% of isolates remaining susceptible. This aligns with global surveillance reports that carbapenems often remain the “last line” against MDR E. coli. However, the reduced susceptibility even to imipenem in more than half the isolates is a serious public health concern, raising the possibility of emerging carbapenemase-producing Enterobacteriaceae (CPE) within the region.

Gentamicin and lomefloxacin demonstrated low but noteworthy activity, with 15–20% susceptibility rates. While this suggests some residual therapeutic potential, their limited efficacy means they cannot be relied upon for routine management. The low susceptibility rates further emphasize the multidrug-resistant nature of these isolates, where resistance spans at least three or more antibiotic classes, fulfilling the definition of MDR.

The clinical and epidemiological implications are profound. Infections with MDR E. coli O157 are not only difficult to treat but also carry risks of outbreaks due to food and water contamination, especially in settings where routine laboratory confirmation and surveillance are weak. For Nigeria, this underscores the urgent need for enhanced surveillance systemto detect ESBL- and carbapenemase-producing strains early, strengthening laboratory capacity and antimicrobial stewardship programs to regulate inappropriate antibiotic use in hospitals, communities, and animal husbandry.

4. Conclusions

In conclusion, this study found a high prevalence and a significant level of multidrug resistance in E. coli O157:H7 from poultry feces in a Lagos live bird market. The data presented here reveal a disturbing trend of escalating resistance, mirroring global concerns about a looming post-antibiotic era. Without urgent containment measures, infections caused by E. coli O157 in Nigeria could become untreatable with conventional antibiotics, compounding morbidity and mortality rates.These findings highlight a substantial public health threat to both those who work with the birds and consumers. There is an urgent need for effective surveillance and control measures to combat the spread of these pathogens and to regulate the use of antimicrobials in the poultry industry.