Shigella
Detection of multiple human enteropathogens in Norway rats (Rattus norvegicus) from an under-resourced neighborhood of Vancouver, British Columbia.
Himsworth CG, Lee L, Byers KA, Atwal HK, Gabaldon G, Ritchie G, Lowe C, Matic N, Chorlton S, Hoang L, Wobeser B, Leung V. PLoS Negl Trop Dis https://doi.org/10.1371/journal.pntd.0011669
Wild city rats can carry infectious organisms including various bacteria, protozoa, and viruses that are capable of causing disease in humans. People living in low-income areas or unhoused may have increased contact with rats and therefore may be particularly vulnerable. However, little is known regarding the role that rats have in spreading these organisms during human outbreaks of disease. From January to August 2021, there was an outbreak of Shigella flexneri, a bacteria that causes gastrointestinal disease, among homeless or poorly housed people in the Downtown Eastside neighborhood of Vancouver, Canada. We hypothesized that rats may have been involved in propagating the outbreak, so we trapped rats within the outbreak area and compared Shigella spp. strains from the feces of these rats and human patients. We found that some Norway rats were carrying Shigella spp., with two samples showing relatedness to the human samples. Rats were often carrying more than one potential human pathogen in their feces. This study highlights the importance of managing rat populations to reduce the spread of diseases to humans, especially among low-income neighborhoods with marginalized, unhoused, or poorly housed individuals.
Ritchie G, Leung V, Himsworth CG, Byers KA, Lee LKF, Chorlton S, Stefanovic A, Romney MG, Matic N, Lowe CF. 2023. Microbiol Spectr 2023 May 31;e0477722. doi: 10.1128/spectrum.04777-22.
During an investigation into a cluster of Shigella flexneri serotype 2a cases in an underserved community, we assessed the relatedness of human and rat S. flexneri isolates utilizing a novel PCR targeting insertion sites (IS-PCR) of mobile elements in the Shigella genome characteristic of the cluster strain. Whole-genome sequences of S. flexneri (n = 50) associated with the cluster were analyzed. De novo genome assemblies were analyzed by a Geneious V10.2.6 motif search, and two unique IS were identified in all human Shigella sequences of the local cluster. Hydrolysis probe PCR assays were designed to detect these sequences consisting of forward and reverse primers to amplify across each insertion site and a hydrolysis probe spanning the insertion site. IS-PCR was performed for three Shigella PCR-positive culture-negative rat intestine specimens from this community. Both insertion sites were detected in the de novo genome assemblies of all clinical S. flexneri isolates (n = 50). Two of the three PCR-positive culture-negative rat samples were positive for both unique ISs identified in the human S. flexneri isolates, suggesting that the rat Shigella species strains were closely related to the human strains in the cluster. The cycle threshold (Ct) values were >35, indicating that the bacterial load was very low in the rat samples. Two unique IS were identified in clinical isolates from a community S. flexneri cluster. Both IS targets were identified in PCR-positive (Shigella spp.), culture-negative rat tissue and clinical isolates from humans, indicating relatedness.