Biological characteristics of a sheep-derived strain of Salmonella and its small colony variant in Aksu, Xinjiang of China

Abstract:

[Background] The small colony variants (SCVs) of bacteria are subpopulations with small colonies, slow growth, and atypical phenotypic characteristics, leading to recurrent infection. Little is known about the food-borne SCVs of Salmonella in China. [Objective] To provide experimental data for the prevention and control of food-borne Salmonella and the guarantee of animal food safety. [Methods] The SCV was induced by the addition of aminoglycoside antibiotics in the medium of a Salmonella strain isolated from sheep bile. The colony morphology, growth, biochemical characteristics, auxotrophy, antibiotic resistance, resistance genes, virulence genes, and biofilm formation ability of the wild type and SCV were determined and compared. [Results] A heme-dependent Salmonella SCV was obtained after induction with kanamycin. Compared with the wild type, the SCV showed a growth rate decrease of 84%, the inability of using citrate, a hemolysis ability increase of 40%, increased tolerance to sulfonamides and aminoglycosides, a biofilm formation reduction of 45%, and a motility decrease of 78%. [Conclusion] The biological characteristics of the Salmonella SCV were significantly different from those of the wild type, which made it difficult to identify the SCVs of Salmonella. The changes of the pathogenicity and drug resistance of SCVs may pose great challenges to the prevention and control of salmonellosis, and the mechanism remains to be studied.