Abstract
Salmonella species is an important foodborne pathogen with the non-typhoidal serovars such as Enteritidis and Typhimurium as the most predominant strains. This study examines the biofilm formation, phenotypic virulence factors and cell surface characteristics of Salmonella strains from ready-to-eat shrimps. The ready-to-eat shrimps were obtained from open markets between November 2016 and October 2017 in Edo and Delta States, Nigeria. The occurrence of Salmonella strains in this study was 210/1440 (14.58%) of the ready-to-eat shrimp’s samples. The identified strains comprise of Salmonella Enteritidis 11, Salmonella Typhimurium 14 and other Salmonella spp. 20. The 45 identified Salmonella strains revealed the following virulence properties: swimming and swarming motility 45(100%); S-layer 39(86.67%); haemolytic activity 40(88.89%); lipase activity 43(95.56%); protease activity 43(95.56%); gelatinase production 43(95.56%); and DNA degrading activity 41(91.11%). The variation in the formation of biofilm-based on the diversity of Salmonella species was observed with higher percentage of Salmonella Typhimurium strains as strong biofilms producers under different environmental conditions. For surface hydrophobicity using bacterial adherence to hydrocarbons, 25(55.56%) were hydrophilic while 20(44.44%) were moderately hydrophobic from the 45 Salmonella isolates. Using salting aggregation test for surface hydrophobicity, all selected isolates 45(100%) was hydrophilic. Autoaggregation index for the 12 selected Salmonella isolates ranged from 15.2–47.2%, while the autoaggragation index for the 12 selected test bacteria ranged from 26.2–71.3%. Coaggragation between the 12 selected test bacteria and 12 Salmonella isolates ranged from 12.5–81.0%. The occurrence of pathogenic species of Salmonella from ready-to-eat shrimps could be detrimental to the consumers. Findings on the physiological conditions of biofilms formed by the foodborne pathogenic Salmonella and the cell surface characteristics therein are crucial for the advancement of methods for controlling Salmonella from ready-to-eat foods.
Highlights
Food safety is a significant public-health concern which links farming to human health and other areas of food production [1]
This study revealed, 210/1440 (14.58%) of the ready-to-eat shrimp samples were positive for Salmonella species
The Salmonella isolates that appear negative for oxidase, urease, indole and Gram-negative rods were selected as presumptive Salmonella
Summary
Food safety is a significant public-health concern which links farming to human health and other areas of food production [1]. Foodborne pathogenicity is the main cause of the worldwide hospitalizations and morbidity as a consequence of consumption of different foods, including seafood [2]. Microbiological surveillance of ready-to-eat (RTE) shrimp products provides empirical data to enlighten scientific guidance for improving the safety and quality of food. Surveillance data may be useful in explaining research priorities based on risk assessments and enlightening the development of food safety standards. Likewise, it may be an indication of direct consumer exposure the ready-to-eat shrimp products. Due to the fact that these ready-to-eat shrimp products are not always given additional bactericidal treatment prior to consumption, the contamination of ready-to-eat shrimp products by foodborne pathogens continues to draw attention. Vibrio species, Escherichia coli, Campylobacter jejuni and Salmonella enterica contamination accounts for the greatest number of seafood products [8,9]
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