Subspecies IIIa and IIIb Salmonellae Are Defective for Colonization of Murine Models of Salmonellosis Compared to Salmonella enterica subsp. I Serovar Typhimurium

Abstract

Non-subspecies I salmonellae are commensals of cold-blooded vertebrates and cause sporadic disease in mammals. The reasons why non-subspecies I salmonellae do not circulate in populations of warm-blooded vertebrates, but instead only cause occasional disease in this niche, are unknown. We examined the ability of Salmonella enterica subsp. IIIa (subsp. arizonae) and subsp. IIIb (subsp. diarizonae) isolates to grow competitively with subspecies I (serovar Typhimurium) ATCC 14028 in vitro, to colonize Salmonella-sensitive BALB/c mice, and to persist in the intestine of Salmonella-resistant CBA/J mice in competitive infections. Subspecies IIIa had severely reduced intestinal colonization, intestinal persistence, and systemic spread in mice. Subspecies IIIa is nonmotile on swarming agar and thus may also have reduced motility under viscous conditions in vivo. Surprisingly, subspecies IIIb colonizes the intestinal tract of BALB/c mice normally yet does not spread systemically. Subspecies IIIb colonization of the intestine of CBA/J mice is reduced late in infection. In order to understand why these isolates do not colonize systemic sites, we determined that subspecies IIIa and IIIb are not internalized well and do not replicate in J774-A.1 murine macrophages, despite normal adherence to these cells. We further show that selected effectors of both type III secretion systems 1 and 2 are secreted by subspecies IIIa and IIIb in vitro but that each of these isolates secretes a different combination of effectors. We outline the phenotypic differences between these subspecies and subspecies I and provide a possible explanation for the inability of these strains to spread systemically in murine models.

Prevalence ofSalmonellaspp., and serovars isolated from captive exotic reptiles in New Zealand

“…Salmonella subspecies II isolates are considered to be commensals of poikilothermic vertebrates such as reptiles, and only rarely cause disease in humans (Katribe et al 2009). In New Zealand, Salmonella subspecies II are isolated predominantly from reptiles or environmental samples (Anonymous 2010).…”

The Type III Secretion System Effector SeoC of Salmonella enterica subsp. salamae and S. enterica subsp. arizonae ADP-Ribosylates Src and Inhibits Opsonophagocytosis

“…enterica subsp. diarizonae are internalized poorly by J774.A1 macrophages (43). Additionally, from a variety of Salmonella serovars isolated from crocodiles, only subspecies enterica and not salamae or diarizonae displayed invasive phenotypes in a mouse model system (44).…”

SalmonellaSpp. and Shiga Toxin–ProducingEscherichia coliPrevalence in an Ocellated Lizard (Timon lepidus) Research Center in Spain

“…Salmonella survives well in the environment and on different surfaces (Mermin et al, 2004;Bauwens et al, 2006). So, the presence of S. enterica I in the water creates enhanced opportunities for transmission, eventually to humans, and suggests a contact with a source of infection, such as wild animals, possibly birds (Katribe et al, 2009), but further epidemiological studies must be done to determine the origin of this subspecies.…”