Three-Year Longitudinal Study: Prevalence of Salmonella Enterica in Chicken Meat is Higher in Supermarkets than Wet Markets from Mexico

Worldwide, chicken meat is considered one of the main sources of Salmonella enterica in humans. To protect consumers from this foodborne pathogen, international health authorities recommend the establishment of continuous Salmonella surveillance programs in meat. However, these programs are scarce in many world regions; thus, the goal of the present study was to perform a longitudinal surveillance of S. enterica in chicken meat in Mexico. A total of 1160 samples were collected and analyzed monthly from 2016 to 2018 in ten chicken meat retailers (supermarkets and wet markets) located in central Mexico. The isolation and identification of S. enterica was carried out using conventional and molecular methods. Overall, S. enterica was recovered from 18.1% (210/1160) of the chicken meat samples. Remarkably, during the three years of evaluation, S. enterica was more prevalent (p < 0.0001) in supermarkets (27.2%, 158/580) than in wet markets (9.0%, 52/580). The study was 3.8 times more likely (odds ratio = 3.8, p < 0.0001) to recover S. enterica from supermarkets than wet markets. Additionally, a higher prevalence (p < 0.05) of this pathogen was observed during the spring, summer, autumn, and winter in supermarkets compared with wet markets. Moreover, the recovery rate of S. enterica from supermarkets showed a gradual increase from 20.78% to 42% (p < 0.0001) from 2016 to 2018. Interestingly, no correlation (p > 0.05) was observed between the S. enterica recovery rate in chicken meat and reported cases of Salmonella infections in humans. Higher levels of S. enterica in chicken meat retailed in supermarkets are not unusual; this phenomenon has also been reported in some European and Asian countries. Together, these results uncover an important health threat that needs to be urgently addressed by poultry meat producers and retailers.