ABSTRACT
Globally, Salmonella species leads the most significant food-related pathogens of public health concern, whose major vehicle of transmission remains to a large extent poultry products. In Nigeria, there is still scarcity of data on the recovery of multidrug-resistant ESBL-producing Salmonella strains in chicken meat. Hence, this study investigated the public health risks of exposures to multi-drug resistant ESBL-producing Salmonella spp. in raw chicken meat vended within four States in Southern Nigeria
The research was carried out between October 2017 and September 2020. The chicken meat samples were collected using simple random sampling methods. Detection of Salmonella sp. was performed by meat rinse centrifugation-plating technique. Presumptive Salmonella colonies were identified by phenotypic and 16S rRNA gene sequencing. The confirmed Salmonella isolates were tested for multi-drug resistance with the Kirby Bauer disc diffusion test.Detection and confirmation of extended-spectrum beta-lactamase (ESBL) phenotypes were performed with double disc synergy and combination disc tests. Sequencing of the ESBL-encoding genes (blaSHV, blaTEM, and blaCTX-M) were also performed using PCR. The conserved and three dimensional (3D) domains in the ESBLs were respectively characterized by the reverse position-specific BLAST (RPS-BLAST) and Cn3D modeling tool. The probable microbial and chemical risks of contaminated chicken meat on human consumers were quantified with FDA-iRisk stochastic software (version 4.0) and mathematical models respectively.
Of the two hundred and twenty nine (229) presumptive Salmonella isolates examined, 52 isolates were confirmed as Salmonella species, 46isolates were multidrug-resistant and 41 isolates confirmed as multidrug-resistant ESBL-producing Salmonella species. Overall, the Salmonella isolates were most resistant to ampicillin (96.15%) but were more sensitive to gentamycin (40.39%). The main serotypes were Salmonella enterica subsp. enterica serovarTyphimurium (35/52; 67.31%) and Salmonella enterica subsp. enterica serovarEnteritidis (17/52; 32.69%). The most and least prevalent ESBL-encoding genes were blaCTX-M (92.685) and blaTEM (31.71%). The RPS-BLAST and Cn3D modeling tool confirmed the three ESBL-encoding genes as serine-based hydrolases that consisted of two 3D domains with unique ligands such as sodium ion, formic acid and glycerol. The public health risks of acute diarrhoea were estimated as 4.70 × 10-5 and 4.78 × 10-5, while the annual burdens diarrhea were ₦33,950,770 and ₦32,900,950 from 390805 cases and 270566 cases in the 2 – 5 years and 13 – 65 years human population groups respectively. A risk mitigation index of 0.85 (85 % reduction in annual diarrhea burden) was deduced from the risk mitigation practices of chicken meat consumers in southern Nigeria. Moreover, non-carcinogenic risks were substantially low for the metals studied in all the locations except for Cd among children in Warri location. However, the incremental cancer risk ranged from 10-4 to 10-3 in all the locations, suggests at least a cancer case per 1,000 exposed people.The findings in this study further highlights the need for rational use of antibiotics in poultry farming, proper meat handling/cooking practices (mitigation protocols), and enforcement of other standard food safety by regulatory agencies so as to reduce or prevent the risk of multi-drug resistant ESBL-bacterial mediated foodborne diseases.
