Occurrence and characteristics of Salmonella isolated from various vegetable sources: Potential for the human-food interface in salmonellosis in Vientiane, the capital of Laos PDR

Abstract

Salmonella is one of the most frequently reported causes of bacterial foodborne outbreaks in the world. Despite this, cases associated with raw vegetable consumption have increased, however very few studies have focused on this. The present study is an overview of the role of vegetables as a concern for Salmonella circulating in Vientiane, the capital of the Lao People's Democratic Republic (Lao PDR). A cross-sectional study was surveyed during the first half 2019 on various types of vegetable sold in retailers in the area. The prevalence, serotype, antimicrobial resistance pattern and genetic profile of Salmonella were investigated. In this study, a total of 80 vegetable samples were collected. 26 (32.5%) positive isolates consisting of 13 different serotypes were determined. S. Corvallis was the most common serotype detected (4/26; 15.4%). Six (23.1%) isolates were found to be resistant to ampicillin, and five (19.2%) isolates resisted sulfamethoxazole-trimethoprim, tetracycline and amoxicillin-clavulanic acid. In addition, a genetic comparison of the vegetable-originated Salmonella with the isolates recovered from hospitalized patients and meats for consumption was carried out using Multilocus sequence typing (MLST). Identical clones of “ST469-S. Rissen” derived from humans, meat and vegetables were evidenced. The inter-species transmission between hosts highlights an alarming possible trend of human-food interface in salmonellosis in Vientiane. Thus, educating individuals on hygienic practices should be recommended. Likewise, intersectoral collaborations should be paid more attention together with scale-up intervention to the entire food chain at the policy level for successful salmonellosis control.