Biology subjects

Audshasai, T.

Publications and source records attributed to Audshasai, T..

3 recordsLinked to original sources

bioRxiv2024

The Streptococcus pneumoniae transcriptome in patient cerebrospinal fluid identifies novel virulence factors required for meningitis

To better understand Streptococcus pneumoniae pathogenesis we performed RNA sequencing on cerebrospinal fluid (CSF) from meningitis patients to identify bacterial genes expressed during invasion of the central nervous system. Comparison to transcriptome data for serotype 1 S. pneumoniae cultured in ex vivo human CSF defined a subset of 57 genes with high expression during human meningitis. Deletion of two of the most highly expressed genetic loci, bgaA (encodes for a {beta}-galactosidase) or the SP_1801-5 putative stress response operon, resulted in S. pneumoniae strains still able to transmigrate the blood brain barrier but which were more susceptible to complement opsonisation and unable to maintain brain infection in a murine meningitis model. In 1144 meningitis patients, infection with bgaA containing S. pneumoniae strains was associated with a higher mortality (22% versus 14% p=0.02). These data demonstrate that direct bacterial RNAseq from CSF can identify previously undescribed S. pneumoniae virulence factors required for meningitis pathogenesis.

microbiology↗

bioRxiv2023

Hypervirulent pneumococci display high levels of nasopharyngeal shedding and rapid onward transmission

Streptococcus pneumoniae serotype 1 is a major cause of invasive pneumococcal disease. Despite its high attack rate, serotype 1 exhibits a low carriage prevalence within the population, which raises important questions about the relationship between carriage and transmission of hypervirulent pneumococcal strains between individuals. We compared the transmission dynamics of serotype 1 sequence type ST217 to serotype 2 strain D39 using a novel model of transmission in young adult mice. Donor index mice were intranasally infected with ST217, D39 or isogenic pneumolysin-deficient mutants and co-housed with recipient naive contact mice. Three days later, all mice were infected with influenza A virus (IAV). Pneumococcal transmission was analysed during colonisation alone and co-infection with IAV by quantification of shedding and nasal colonisation in index and contact mice. The role of the toxin pneumolysin in shedding, transmission and colonisation, and the host nasopharyngeal immune response were investigated. We show that ST217 was shed in index mice at significantly greater levels compared to D39. Upon viral co-infection, ST217 was shed and transmitted at a faster rate to contact mice and displayed higher transmission levels compared to D39. Interestingly, the toxin pneumolysin did not play a role in shedding. However, upon acquisition by contact mice, pneumolysin-dependent macrophage recruitment was observed in the nasopharynx. Our results show that the rapid and high transmission rate of serotype 1 is a key factor in its ability to disseminate quickly within the population and cause disease outbreaks.

microbiology↗

bioRxiv2021

Streptococcus pneumoniae rapidly translocates from the nasopharynx through the cribriform plate to invade and inflame the dura

The entry routes and translocation mechanisms of bacterial pathogens into the central nervous system remain obscure. We report here that Streptococcus pneumoniae (Sp) or polystyrene microspheres, applied to the nose of a mouse, appeared in the meninges of the dorsal cortex within minutes. Recovery of viable bacteria from dissected tissue and fluorescence microscopy showed that up to at least 72h, Sp and microspheres were predominantly in the outer of the two meninges, the pachymeninx. No Sp were found in blood or cerebrospinal fluid. Evidence that this was not an artifact of the method of administration is that in mice infected by horizontal transmission, Sp were also predominantly in the meninges and absent from blood. Intravital imaging through the skull, and flow cytometry showed recruitment and activation of LysM+ cells in the dorsal pachymeninx at 5h and 10h following intranasal infection. Imaging of the cribriform plate suggested that both Sp and microspheres entered through its foramina via an inward flow of fluid connecting the nose to the pachymeninx. Our findings bring further insight into the invasion mechanisms of bacterial pathogens such as Sp into the central nervous system, but are also pertinent to the delivery of drugs to the brain, and the entry of air-borne particles into the cranium.

microbiology↗