Biology subjects

Horswill, A. R.

Publications and source records attributed to Horswill, A. R..

21 records · Page 2Linked to original sources

bioRxiv2020

MgrA regulates interaction of Staphylococcus aureus with mucin

BackgroundTo defend the lungs, mucus adheres to bacterial cells and facilitates their removal by ciliary transport. Our goals were to measure the affinity of mucus for the respiratory pathogen Staphylococcus aureus and identify bacterial genes that regulate this interaction. MethodsS. aureus was added to pig tracheas to determine whether it binds mucus or epithelial cells. To quantify its affinity for mucus, we developed a competition assay in microtiter plates. Mucin was added over a dose range as an inhibitor of bacterial attachment. We then examined how transcriptional regulator MgrA and cell wall transpeptidase sortase (SrtA) affect bacterial interaction with mucin. ResultsIn pig tracheas, S. aureus bound mucus strands from submucosal glands more than epithelial cells. In microtiter plate assays, {Delta}srtA failed to attach even in the absence of mucin. Mucin blocked wild type S. aureus attachment in a dose-dependent manner. Higher concentrations were needed to inhibit binding of {Delta}mgrA. Co-deletion of ebh and sraP, which encode surface proteins repressed by MgrA, suppressed the {Delta}mgrA binding phenotype. No differences between {Delta}mgrA and wild type were observed when methylcellulose or heparin sulfate were substituted for mucin, indicating specificity. ConclusionsMucin decreases attachment of S. aureus to plastic, consistent with its physiologic role in host defense. S. aureus deficient in MgrA has decreased affinity for mucin. Ebh and SraP, which are normally repressed by MgrA, may function as inhibitors of attachment to mucin. These data show that specific bacterial factors may regulate the interaction of S. aureus with mucus.

microbiology↗

bioRxiv2019

Identification of key determinants of Staphylococcus aureus vaginal colonization

Staphylococcus aureus is an important pathogen responsible for nosocomial and community acquired infections in humans, and methicillin-resistant S. aureus (MRSA) infections have continued to increase despite wide-spread preventative measures. S. aureus can colonize the female vaginal tract and reports have suggested an increase in MRSA infections in pregnant and postpartum women as well as outbreaks in newborn nurseries. Currently, little is known about specific factors that promote MRSA vaginal colonization and subsequent infection. To study S. aureus colonization of the female reproductive tract in a mammalian system, we developed a mouse model of S. aureus vaginal carriage and demonstrated that both hospital-associated and community-associated MRSA isolates can colonize the murine vaginal tract. Immunohistochemical analysis revealed an increase in neutrophils in the vaginal lumen during MRSA colonization. Additionally, we observed that a mutant lacking fibrinogen binding adhesins exhibited decreased persistence within the mouse vagina. To further identify novel factors that promote vaginal colonization, we performed RNA-sequencing to determine the transcriptome of MRSA growing in vivo during vaginal carriage at 5 hours, 1-day, and 3-days post-inoculation. Over 25% of bacterial genes were differentially regulated at all time points during colonization compared to laboratory cultures. The most highly induced genes were those involved in iron acquisition, including the Isd system and siderophore transport systems. Mutants deficient in these pathways did not persist as well during in vivo colonization. These results reveal that fibrinogen binding as well as the capacity to overcome host nutritional limitation are important determinants of MRSA vaginal colonization.\n\nIMPORTANCEStaphylococcus aureus is an opportunistic pathogen able to cause a wide variety of infections in humans. Recent reports have suggested an increasing prevalence of MRSA in pregnant and postpartum women, coinciding with the increased incidence of MRSA infections in the NICU and newborn nurseries. Vertical transmission from mothers to infants at delivery is a likely route of MRSA acquisition by the newborn, however, essentially nothing is known about host and bacterial factors that influence MRSA carriage in the vagina. Here, we established a mouse model of vaginal colonization and observed that multiple MRSA strains can persist in the vaginal tract. Additionally, we determined that MRSA interactions with fibrinogen as well as iron uptake can promote vaginal persistence. This study is the first to identify molecular mechanisms which govern vaginal colonization by MRSA, the critical initial step preceding infection and neonatal transmission.

microbiology↗

bioRxiv2018

Increased rates of genomic mutation in a biofilm co-culture model of P. aeruginosa and S. aureus

Biofilms are major contributors to disease chronicity and are typically multi-species in nature. Pseudomonas aeruginosa and Staphylococcus aureus are leading causes of morbidity and mortality in a variety of chronic diseases but current in vitro dual-species biofilms models involving these pathogens are limited by short co-culture times (24 to 48 hours). Here, we describe the establishment of a stable (240 hour) co-culture biofilm model of P. aeruginosa and S. aureus that is reproducible and more representative of chronic disease.\n\nThe ability of two P. aeruginosa strains, (PAO1 and a cystic fibrosis isolate, PA21), to form co-culture biofilms with S. aureus was investigated. Co-culture was stable for longer periods using P. aeruginosa PA21 and S. aureus viability within the model improved in the presence of exogenous hemin. Biofilm co-culture was associated with increased tolerance of P. aeruginosa to tobramycin and increased susceptibility of S. aureus to tobramycin and a novel antimicrobial, HT61, previously shown to be more effective against non-dividing cultures of Staphylococcal spp. Biofilm growth was also associated with increased short-term mutation rates; 10-fold for P. aeruginosa and 500-fold for S. aureus.\n\nBy describing a reproducible 240 hour co-culture biofilm model of P. aeruginosa and S. aureus, we have shown that interspecies interactions between these organisms may influence short-term mutation rates and evolution, which could be of importance in understanding the adaptive processes that lead to the development of antimicrobial resistance.

microbiology↗