Scientists have reported several Salmonella types from healthy people who often worked in the food sector.
Researchers identified five rare Salmonella serovars in China and used whole genome sequencing to look at their spread among asymptomatic individuals. Antibiotic resistance genes and virulence genes were also found.
According to the study published in China CDC Weekly, healthy individuals, particularly food handlers, could be potential sources of Salmonella dissemination. Monitoring Salmonella prevalence in this group is essential to understand and manage associated risks.
Between 2013 and 2020, fecal samples were collected from people undergoing occupational health examinations in Yulin City. A total of 7,044 Salmonella isolates were recovered from 372,708 individual samples. Among these, 119 Salmonella serovars were identified in healthy people.
A total of 14 isolates of rare serovars were sourced from individuals ranging in age from 17 to 60. A dozen were men and two were women. Thirteen people were engaged in food handling. The isolates were one each of Salmonella Welikade, Mountpleasant, and Coeln, two of Salmonella Ealing, and nine of Salmonella Ouakam.
Seven Salmonella Ouakam isolates were collected from healthy individuals, all employees at the same company, within one week, indicating the potential for asymptomatic transmission. There were no detailed epidemiological data to confirm an outbreak.
Antibiotics assessed were Amikacin, Ceftazidime, Chloramphenicol, Ciprofloxacin, Colistin, Ertapenem, Meropenem, Piperacillin-Tazobacta, Tetracycline, Tigecycline, and Trimethoprim-Sulfamethoxazole.
Salmonella Welikade, Mountpleasant, and Ealing isolates were susceptible to all 11 antibiotics tested. However, the Salmonella Coeln isolate and nine Salmonella Ouakam isolates were multi-drug resistant. Both exhibited resistance to Chloramphenicol, Trimethoprim-Sulfamethoxazole, and Tetracycline. The Salmonella Coeln isolate was resistant to Tigecycline, an antibiotic typically reserved for severe Gram-negative infections. All Salmonella Ouakam isolates were resistant to Ceftazidime and Ciprofloxacin.
“This study underscores the critical importance of active surveillance among healthy individuals, especially within key occupational groups such as food workers, to monitor foodborne pathogens,” said scientists.
Salmonella spread
In another study, an early-warning module, using whole genome sequencing data, identified a newly regionally prevalent sequence type of monophasic Salmonella Typhimurium at the end of 2023, likely associated with pork consumption.
A total of 31 Salmonella 4,[5],12:i:- sequence type (ST) 8333 isolates were obtained from sporadic diarrhea cases between 2017 and 2023. Twenty five isolates were sourced from Sichuan Province. This area has the largest volume of pigs for slaughter.
Analysis revealed a close genetic relationship among these isolates, indicating that the ST8333 strain spread to Xinjiang, Sichuan, and Jiangsu after originating in Qinghai Province in 2017. A total of 27 antimicrobial resistance genes belonging to seven classes were identified.
Some ST8333 isolates carry a certain plasmid, originally sourced from a swine fecal swab In Sichuan. Experts said this suggests that the strain isolated from patients may be related to eating contaminated pork products.
Scientists said continued detection indicates ongoing circulation with findings showing the need to implement monitoring and control measures to prevent further spread of the multidrug-resistant ST8333 to other regions.
“To prevent a nationwide pandemic, food production enterprises and public health departments should prioritize surveillance of these ST8333 isolates. Our study highlighted Sichuan as a reservoir for the emergence and transmission of multidrug-resistant ST8333 strains, emphasizing the need for strengthened surveillance in this region to rapidly interrupt transmission,” they added.
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