Detection of virulence and resistance genes in salmonella Isolated from meat products
DOI:
https://doi.org/10.64149/Keywords:
Salmonella; virulence genes; antimicrobial resistance; meat products; cross-sectional study; Pakistan.Abstract
Background: In low and middle-income countries, salmonella contamination of meat products contributes significantly to the burden of foodborne illness. The concurrent characterization of virulence and resistance genes within individual isolates has not been studied in low-resource settings, which does not allow risk stratification when surveying for public health.
Methods: A cross-sectional study enrolled 226 meat product samples (chicken n=93, beef n=80, mutton n=53) stratified by facility source (markets n=134, slaughterhouses n=92) in Lahore, Pakistan in December of 2024-May of 2025. Salmonella was isolated following ISO 6579:2002 culture methods with biochemical confirmatory testing. Isolates confirmed as salmonella were characterized using multiplex PCR to test for a collection of eight virulence genes (hilA, invA, mgtC, spiA, sopB, sopE, avrA, spvC) and seven resistance determinants (blaTEM, tetA, tetB, sul1, sul2, aadA, qnrS). Prevalence estimates are reported with 95% exact binomial confidence intervals and the association between meat type and facility source were assessed using chi-square testing.
Results: Overall salmonella prevalence was 17.3% (39/226; 95% CI 12.8–23.0%), with a statistically significant difference between meat types (p=0.009), specifically chicken (27.2%), beef (15.0%), and mutton (3.8%). The risk of salmonella in samples from slaughterhouses was 56% higher than from markets (22.2% versus 14.2%, RR 1.56, 95% CI 1.10–2.22). Of the 39 confirmed isolates, the frequency of the virulence genes were: hilA 89.7% (n=35), mgtC 76.9% (n=30), spiA 76.9% (n=30), invA 74.4% (n=29), sopB 51.3% (n=20), sopE 46.2% (n=18), avrA 43.6% (n=17), spvC 33.3% (n=13).
Conclusions: Salmonella contamination of meat products in Pakistan is common and is characterized by virtually universal virulence gene carriage and the predominance of multidrug resistant phenotypes, especially in chicken. Slaughterhouse processing is a critical point of intervention.
