Biology subjects

Miles, S. L.

Publications and source records attributed to Miles, S. L..

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

Acquisition of a large virulence plasmid (pINV) promoted temperature-dependent virulence and global dispersal of O96:H19 enteroinvasive Escherichia coli

Enteroinvasive Escherichia coli (EIEC) and Shigella are closely related agents of bacillary dysentery. It is widely viewed that EIEC and Shigella species evolved from E. coli via independent acquisitions of a large virulence plasmid (pINV) encoding a type three secretion system (T3SS). Sequence Type (ST)99 O96:H19 E. coli is an emergent clone of EIEC responsible for recent outbreaks in Europe and South America. Here, we reconstruct the evolutionary history of ST99 E. coli using BactDating, revealing distinct phylogenomic clusters of pINV-positive and -negative isolates. To study the impact of pINV acquisition on the virulence of this clone, we developed an EIEC-zebrafish infection model showing that virulence of ST99 EIEC is thermoregulated. Strikingly, zebrafish infection using the oldest available pINV-negative isolate reveals a separate, temperature-independent mechanism of virulence, indicating that ST99 non-EIEC strains were virulent before pINV acquisition. Taken together, these results suggest that an already pathogenic E. coli acquired pINV and that virulence of ST99 isolates became thermoregulated once pINV was acquired. ImportanceEnteroinvasive Escherichia coli (EIEC) and Shigella are etiological agents of bacillary dysentery. Sequence Type (ST)99 is an emergent clone of EIEC hypothesised to cause human disease by the recent acquisition of pINV, a large plasmid encoding a type three secretion system (T3SS) that confers the ability to invade human cells. Here, using phylogenomic reconstruction and zebrafish larvae infection, we show that the virulence of ST99 EIEC isolates is highly dependent on temperature, while pINV-negative isolates encode a separate temperature-independent mechanism of virulence. These results highlight that ST99 non-EIEC isolates may have been virulent before pINV acquisition and highlight an important role for pINV acquisition in the emergence of ST99 EIEC in humans, allowing wider dissemination across Europe and South America.

microbiology↗

bioRxiv2022

P1 bacteriophage-enabled delivery of CRISPR-Cas9 antimicrobial activity against Shigella flexneri

The discovery of clustered, regularly interspaced, short palindromic repeats (CRISPR) and the Cas9 RNA-guided nuclease provides unprecedented opportunities to selectively kill specific populations or species of bacteria. However, the use of CRISPR-Cas9 to clear bacterial infections in vivo is hampered by the inefficient delivery of cas9 genetic constructs into bacterial cells. Here, we use a broad-host-range P1-derived phagemid to deliver the CRISPR-Cas9 chromosomal-targeting system into Escherichia coli and the dysentery-causing Shigella flexneri to achieve DNA sequence-specific killing of targeted bacterial cells. We show that genetic modification of the helper P1 phage DNA packaging site (pac) significantly enhances the purity of packaged phagemid and improves the Cas9-mediated killing of S. flexneri cells. We further demonstrate that P1 phage particles can deliver chromosomal-targeting cas9 phagemids into S. flexneri in vivo using a zebrafish larvae infection model, where it significantly reduces the bacterial load and promotes host survival. Our study highlights the potential of combining a P1 bacteriophage-based delivery with the CRISPR chromosomal-targeting system to achieve DNA sequence-specific cell lethality and efficient clearance of bacterial infection.

microbiology↗