S. IIIb 61:k:1,5,(7)¶

At a Glance


Antigenic Formula	`61:k:1,5,`
Serogroup	O:61
NCBI Pathogen Detection	View isolates

Background Information¶

Salmonella enterica subsp. diarizonae serovar 61:k:1,5,(7) (antigenic formula 61:k:1,5,(7)) is a serovar of the O:61 serogroup. This serovar was first found in sheep in1952 from carcasses of newborn lambs. InGreat Britain, serovar IIIb 61:k:1,5,(7) is the predominant Salmonella serotype in sheep, representing more than 60% of reported infections in this species. Chronic proliferative rhinitis (CPR) in sheep has been reported as a new disease associated with serovar IIIb 61:k:1,5,(7) in the USA, Spain, and Switzerland. CPR is a chronic disease mainly affecting adult sheep, posing a risk of spreading serovar IIIb 61:k:1,5,(7) between flocks and exhibiting zoonotic potential. Infection with serovar IIIb 61:k:1,5,(7) can also cause abortions in sheep.

Genetic Characteristics¶

Serovar IIIb 61:k:1,5,(7) has been found to be polyphyletic with two lineages identified and one stand-alone singleton that does not cluster with any other Salmonella IIIb 61:k:1,5,(7) isolates. Among IIIb 61:k:1,5,(7) isolates in Swiss sheep flocks Weber et al. analyzed, no resistant isolates were detected, except for one isolate showing resistance against ampicillin. A German study pointed out that all IIIb 61:k:1,5,(7) strains they tested were susceptible to 13 out of 14 antimicrobial substances, with resistance observed only to sulfamethoxazole. The high number of macrorestriction groups among IIIb 61:k:1,5,(7) strains suggests low clonality within this serovar. Schnydrig et al. claimed that serovar IIIb 61:(k):1,5,(7) tends to be opportunistic, with low virulence and high susceptibility to antimicrobials. Serovar IIIb 61:k:1,5,(7) consists oftwo distinct lineages, characterized by sequence types ST432 and ST439. ST432 is the more dominant lineage and has been isolated from sheep, humans, and other sources. In contrast, all ST439 isolates with known origins were recovered exclusively from human clinical samples. The ST432 lineage exhibits increased pseudogenization and carries a virB/D4 plasmid encoding a type IV secretion system (T4SS). Notably, it lacks the iro gene cluster, which is responsible for salmochelin siderophore production and iron acquisition. These traits likely enable ST432 to persistently colonize the intestines of sheep. Additionally, ST432 isolates were found to be highly clonal, showing minimal genetic variation over a sampling period of nearly 20 years.

Animal Reservoir¶

Serovar IIIb 61:k:1,5,(7) is host-adapted to sheep.

Geographical Distribution¶

Serovar IIIb 61:k:1,5,(7) has been reported in the US, Canada, Brazil, and Europe.

Human/Animal Outbreaks¶

Not clear, at least no recent human outbreaks linked to this serovar have been reported.

S. IIIb 61:k:1,5,(7)¶

Background Information¶

Genetic Characteristics¶

Animal Reservoir¶

Geographical Distribution¶

Human/Animal Outbreaks¶

Border Rejections¶

Recalls¶

References¶