Pathogenic potential of non-typhoidal Salmonella serovars isolated from aquatic environments in Mexico

Genomic characteristics of Salmonella Montevideo and Pomona: impact of isolation source on antibiotic resistance, virulence and metabolic capacity

Salmonella enterica is known for its disease-causing serotypes, including Montevideo and Pomona. These serotypes have been found in various environments, including river water, sediments, food, and animals. However, the global spread of these serotypes has increased, leading to many reported infections and outbreaks. The goal of this study was the genomic analysis of 48 strains of S. Montevideo and S. Pomona isolated from different sources, including clinical. Results showed that environmental strains carried more antibiotic resistance genes than the clinical strains, such as genes for resistance to aminoglycosides, chloramphenicol, and sulfonamides. Additionally, the type 4 secretion system, was only found in environmental strains. .Also many phosphotransferase transport systems were identified and the presence of genes for the alternative pathway Entner-Doudoroff. The origin of isolation may have a significant impact on the ability of Salmonella isolates to adapt and survive in different environments, leading to genomic flexibility and a selection advantage.

In vitro invasiveness and antimicrobial resistance of Salmonella enterica subspecies isolated from wild and captive reptiles

Reptiles are carriers of Salmonella and can intermittently shed bacteria in their faeces. Contact with snakes and lizards is a source of human salmonellosis. Here, two populations of reptiles, wild and captive were surveyed for Salmonella. One hundred thirty wild-caught reptiles were sampled for Salmonella including 2 turtle, 9 snake and 31 lizard species. Fifty-two of 130 (40%) animals were Salmonella positive: one of 5 (20%) turtles, 7 of 14 (50%) snakes and 44 of 111 (39.6%) lizards. One hundred twenty-two reptiles were sampled from a zoo collection including 1 turtle, 6 tortoise, 9 lizard, 14 snake and 1 crocodile species. Forty-two of 122 (34.4%) captive reptiles sampled were Salmonella positive. Salmonella was most commonly isolated from lizards and snakes. Fifteen serotypes were identified from zoo and 19 from wild-caught reptiles and most were members of subspecies enterica (I), salamae (II), arizonae (IIIa) or diarizonae (IIIb). Antimicrobial susceptibility testing was conducted on all Salmonella isolates; only two exhibited resistance, a Salmonella subsp. (II) ser. 21:z₁₀ :z₆ (Wandsbek) isolate cultured from a wild-caught reptile and a Salmonella Typhimurium DT120 isolated from a captive snake. The invasive capacity of reptile-associated Salmonella strains into cultured human intestinal epithelial (Caco2) and mouse macrophages cell lines (J774A.1) was also investigated. All isolates were invasive into both cell lines. Significant (P ≤ 0.001) variability in invasiveness into polarized Caco2 cells was observed. Salmonella Eastbourne exhibited the highest invasiveness into Caco2 cells and Salmonella Chester the lowest, with mean per cent recoveries of 19.99 ± 0.32 and 1.23 ± 0.30, respectively. Invasion into J774A.1 macrophages was also variable but was not significant. Salmonella subsp. II ser. 17:g,t:- (Bleadon) exhibited the highest invasiveness into J774A.1 with a mean per cent recovery of 10.19 ± 0.19. Thus, reptile-associated Salmonellae are likely to have different capacities to cause disease in humans.

Genetics and physiology of Salmonella houtenae isolated from a river in Mexico provides insight into the aquatic habitat influence on its adaptation and pathogenesis

Salmonella enterica subsp. houtenae (IV) is a non-enteric subspecies of the genus Salmonella and has recently been implicated in extraintestinal diseases in humans. In Mexico, its reported that rivers are a reservoir of Salmonella houtenae, however, detailed information about the virulence and infective capacity of this bacterium are limited. Here, we present the high-quality genome draft of Salmonella houtenae str. CFSAN039533 isolated from a river in Culiacan, Mexico. In addition, its virulence, antimicrobial resistance profile and the use of carbon sources for its primary metabolism are analyzed. The genome sequence of CFSAN03953 strain comprises 4.74-Mb which contains 4266 protein coding genes and 77 tRNA genes. The strain belongs to the Marine serotype (48: g, z51: -), and showed several virulence genes related to the SPI-1, SPI-2, SPI-3, SPI-5 and fimbriae genes. The strain exhibited a susceptible phenotype, which contrasted with the resistance genes of aminoglycosides family identified into the genome. Carbon source degradation evaluation along with the genomic analysis, indicated that the strain can use a relatively broad spectrum of compounds related to the central metabolic pathways. This study provides information on the genetics and physiology of Salmonella houtenae that confirms its ability to survive and adapt to the environment. In addition, its pathogenic potential and infective capacity towards warm-blooded hosts are demonstrated.