Abstract

Antibiotic resistance profiles of Escherichia coli were investigated in an intensive pig production system in the uMgungundlovu District, South Africa, using the ‘farm-to-fork’ approach. Four hundred seventeen (417) samples were collected from pig and pig products at different points (farm, transport, and abattoir). E. coli was isolated and enumerated using the Colilert® 18/Quanti-Tray® 2000 system. Ten isolates from each Quanti-tray were selected randomly and putatively identified on eosin methylene blue agar. Real-time PCR targeting the uidA gene was used to confirm isolates to the genus level. The Kirby–Bauer disc diffusion method was used to determine the isolates’ antibiotic susceptibility profiles against 20 antibiotics. A total of 1044 confirmed E. coli isolates were obtained across the three critical points in the food chain. Resistance was observed to all the antibiotics tested with the highest and lowest rates obtained against tetracycline (88.5%) and meropenem (0.2%), respectively. Resistance was also observed to chloramphenicol (71.4%), ampicillin (71.1%), trimethoprim-sulfamethoxazole (61.3%), amoxicillin-clavulanate (43.8%), cephalexin (34.3%), azithromycin (23.9%), nalidixic acid (22.1%), cefoxitin (21.1%), ceftriaxone (18.9%), ciprofloxacin (17.3%), cefotaxime (16.9%), gentamicin (15.5%), cefepime (13.8%), ceftazidime (9.8%), amikacin (3.4%), piperacillin-tazobactam (1.2%), tigecycline (0.9%), and imipenem (0.3%). Multidrug resistance (MDR) was observed in 71.2% of the resistant isolates with an overall multiple antibiotic resistance (MAR) index of 0.25, indicating exposure to high antibiotic use environments at the farm level. A high percentage of resistance was observed to growth promoters and antibiotics approved for veterinary medicine in South Africa. Of concern was resistance to critically important antibiotics for animal and human use and the watch and reserve categories of antibiotics. This could have adverse animal and human health consequences from a food safety perspective, necessitating efficient antibiotic stewardship and guidelines to streamline antibiotic use in the food-animal production chain.

Highlights

  • Animal-based protein consumption continues to increase worldwide due to economic development and urbanization [1]

  • We investigated the antibiotic resistance profiles of E. coli in an intensive pig production system in uMgungundlovu District, KwaZulu-Natal, South Africa using the farm-to-fork approach to determine the nature and extent of antibiotic resistance in food animal production

  • The prevalence of multidrug resistance (MDR) isolates and multiple antibiotic resistance (MAR) index of E. coli from different sampling sources were compared using the ANOVA, Tukey test, and a p-value of < 0.05 was considered statistically significant. This is the first study in South Africa investigating antibioticresistant E. coli in intensive pig farming using the “farm-to-fork” approach

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Summary

Introduction

Animal-based protein consumption continues to increase worldwide due to economic development and urbanization [1]. The subtherapeutic use of antibiotics as growth promoters results in the development and subsequent transmission of resistant bacteria between animals and from animals to humans [14]. The European Union (EU) has restricted the use of AGPs since 1999 and completely banned their use in 2006 [18] Both the World Organization for Animal Health (OIE) [19] and the World Health Organization (WHO) have compiled lists of critically important antibiotics for animal and human health to minimize the health risks associated with antimicrobial use and subsequent resistance in food-producing animals [20].

Discussion
Study Clearance and Ethical Consideration
Study Site and Sample Collection
Antibiotic Susceptibility Testing
Findings
Statistical Analysis and Interpretation
Conclusions
Full Text
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