Biology subjects

De Silva, P. M.

Publications and source records attributed to De Silva, P. M..

3 recordsLinked to original sources

bioRxiv2022

Shigella serotypes associated with carriage in humans establish persistent infection in zebrafish

Shigella represents a paraphyletic group of human-adapted Escherichia coli lineages that converged towards the same enteropathogenic pathovar. In low-income countries, Shigella is typically transmitted by ingestion of contaminated water and food, while in high-income countries sexual transmission among men who have sex with men (MSM) is the dominant route of transmission. Although more than 40 different serotypes of Shigella have been reported globally, within the MSM community the majority of reported cases are attributed to three Shigella serotypes: the Shigella sonnei unique serotype (Ss) and the Shigella flexneri serotypes 2a and 3a. Here, using a zebrafish infection model, we demonstrate that Shigella can establish persistent infection in vivo. In this case, bacteria are not cleared by the host immune system and become tolerant to therapeutic doses of antibiotics. We show that persistence is dependent on the Shigella O-Antigen, a key constituent of the bacterial cell surface and determinant of serotype classification. Representative isolates of three Shigella serotypes associated with global dissemination and MSM transmission (S. sonnei Ss, S. flexneri 2a and 3a) all persist in zebrafish, while a serotype not associated with MSM transmission (S. flexneri 5a) does not. Strikingly, Shigella serotypes which establish persistent infection fail to promote macrophage cell death in vivo. We conclude that zebrafish can be a valuable platform to illuminate host and pathogen factors underlying the establishment of persistent infection with Shigella in humans. HighlightsO_LIShigella can establish persistent infection in zebrafish C_LIO_LIEstablishment of persistent infection in vivo depends on Shigella serotype C_LIO_LIThe same serotypes establishing persistent infection in zebrafish are prevalent in a patient group in whom persistent infection is observed C_LIO_LIShigella serotypes which establish persistent infection fail to promote macrophage cell death in vivo C_LI In BriefIn high-income countries, sexual transmission among men who have sex with men (MSM) is the dominant cause of domestic Shigella transmission. Torraca et al. discover that three serotypes of Shigella associated with MSM transmission also persist in zebrafish. These results indicate that Shigella serotypes associated with MSM transmission can establish carriage in the host, and highlight the use of zebrafish infection to study Shigella persistent infection in humans.

microbiology↗

bioRxiv2022

Temporal GWAS identifies a widely distributed putative adhesin contributing to pathogen success in Shigella spp.

Shigella has emerged as a successful pathogen posing a threat to human health worldwide in the recent years. The rise of Shigella over the years has variably been attributed to AMR genes, virulence, and bacterial competition factor but no method has taken a function-agnostic approach to look for factors associated with modern variants of the pathogens. To address this gap, here we combined historical and modern isolate collections to identify such factors through a novel approach, termed temporal GWAS (tGWAS). Our analyses identified a novel putative adhesin gene, which we called stv that was associated with time of isolation and concentrated in expanding lineages of Shigella spp, as well as widely distributed in other bacterial species. We confirmed that stv is carried on a small 2689bp plasmid and in silico analyses revealed that Stv contained a new protein domain that was in combination with other domains in a manner suggestive of a secreted bacterial toxin. However, an all-proteome AlphaFold interaction screen indicated a high likelihood of interactions with fimbrial proteins, despite fimbrae thought to be defunct in Shigella sp. Collectively, these findings suggest that Stv is a novel protein domain with a likely role in Shigella success that is also widely distributed in other species.

genomics↗

bioRxiv2021

A tale of two plasmids: contributions of plasmid associated phenotypes to epidemiological success among Shigella

Dissemination of antimicrobial resistance (AMR) genes by horizontal gene transfer (HGT) mediated through plasmids is a major global concern. Genomic epidemiology studies have shown varying success of different AMR plasmids during outbreaks, but the underlying reasons for these differences are unclear. Here, we investigated two Shigella plasmids (pKSR100 and pAPR100) that circulated in the same transmission network but had starkly contrasting epidemiological outcomes to identify plasmid features that may have contributed to the differences. We used plasmid comparative genomics to reveal divergence between the two plasmids in genes encoding AMR, SOS response alleviation, and conjugation. Experimental analyses revealed that these genomic differences corresponded with reduced conjugation rates for the epidemiologically successful pKSR100, but more extensive AMR, reduced fitness costs, and a reduced SOS response in the presence of antimicrobials, compared with the less successful pAPR100. The discrepant phenotypes between the two plasmids are consistent with the hypothesis that plasmid associated phenotypes contribute to determining the epidemiological outcome of AMR HGT and suggest that phenotypes relevant in responding to antimicrobial pressure and fitness impact may be more important than those around conjugation in this setting. Plasmid phenotypes could thus be valuable tools in conjunction with genomic epidemiology for predicting AMR dissemination.

microbiology↗