Abstract
Glycosaminoglycans (GAGs) are linear polysaccharides and are among the primary components of mucosal surfaces in mammalian systems. The GAG layer lining the mucosal surface of the urinary tract is thought to play a critical role in urinary tract homeostasis and provide a barrier against urinary tract infection (UTI). This key component of the host-microbe interface may serve as a scaffolding site or a nutrient source for the urinary microbiota or invading pathogens, but its exact role in UTI pathogenesis is unclear. Although members of the gut microbiota have been shown to degrade GAGs, the utilization and degradation of GAGs by the urinary microbiota or uropathogens had not been investigated. In this study, we developed an in vitro plate-based assay to measure GAG degradation and utilization and used this assay to screen a library of 37 urinary bacterial isolates representing both urinary microbiota and uropathogenic species. This novel assay is more rapid, inexpensive, and quantitative compared to previously developed assays, and can measure three of the major classes of human GAGs. Our findings demonstrate that this assay captures the well-characterized ability of Streptococcus agalactiae to degrade hyaluronic acid and partially degrade chondroitin sulfate. Additionally, we present the first known report of chondroitin sulfate degradation by Proteus mirabilis, an important uropathogen and a causative agent of acute, recurrent, and catheter-associated urinary tract infections (CAUTI). In contrast, we observed that uropathogenic Escherichia coli (UPEC) and members of the urinary microbiota, including lactobacilli, were unable to degrade GAGs.
Highlights
Urinary tract infection (UTI) is among the most common adult bacterial infections encountered in community and clinical settings
We developed a semi-quantitative plate-based assay to assess the metabolic potential of 37 urinary microbiota strains to utilize and degrade clinically relevant GAGs in standard basal media and artificial urine media
Our results demonstrate that this assay can capture the well-characterized ability of S. agalactiae to degrade HA and partially degrade CS as well as the ability of P. heparinus to degrade HA, HP, and CS
Summary
Urinary tract infection (UTI) is among the most common adult bacterial infections encountered in community and clinical settings. When a patient experiences ≥2 symptomatic infections in six months or ≥3 infections in one year, it is defined as recurrent urinary tract infection (rUTI) (Malik et al, 2018b). Present rUTI therapies heavily rely on antimicrobials to achieve sterility in the urinary tract, but are undermined by increasing rates of antimicrobial resistance and allergy (Malik et al, 2018a). While a constant flux of urine containing electrolytes, osmolytes, amino acids, and carbohydrates may support the urinary microbiota, an understudied carbon source in the urinary tract is the glycosaminoglycan (GAG) layer lining the luminal surface of the bladder epithelium (Figure 1A). Relevant GAGs include heparin/heparan sulfate (HP), chondroitin sulfate (CS), hyaluronic acid (HA), and keratan sulfate (KS)
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