Petersen, F. C. | Search bioRxiv

bioRxiv2019

Impact of narrow spectrum Penicillin V on the oral and fecal resistome in a young child treated for otitis media

BackgroundAntibiotic overuse has led to a global emergence of resistant bacteria, and children are among the frequent users. Most studies with broad-spectrum antibiotics show severe impact on the resistome development of patients. Although narrow-spectrum antibiotics are believed to have less side-effects, their impact on the microbiome and resistome is mostly unknown. The aim of this study was to investigate the impact of the narrow-spectrum antibiotic phenoxymethylpenicillin (Penicillin V) on the microbiome and resistome of a child treated for acute otitis media (OM).\n\nMethodsOral and fecal samples were collected from a one-year child before (day 0) and after (day 5 and 30) receiving Penicillin V against OM. Metagenomic sequencing data was analysed to determine taxonomic profiling, using Kraken and Bracken software, and resistance profiling, using KMA in combination with the ResFinder database.\n\nResultsIn the oral samples, 11 antimicrobial resistance genes (ARGs), belonging to four classes, were identified at baseline. At day 5, the abundance of some ARGs was increased, some remained unchanged, while others disappeared. At day 30, most ARGs had returned to baseline levels, or lower. In the fecal samples we observed seven ARGs at baseline and five at day 5, with only one gene observed at day 5 being present at baseline. At day 30 the number of ARGs increased to 21 ARGs from 7 different classes.\n\nConclusionsPenicillin V had a remarkable impact on the fecal resistome indicating that even narrow-pectrum antibiotics may have important consequences in selecting for a more resistant microbiome.

microbiology↗

bioRxiv2019

Conserved pheromone production, response and degradation by Streptococcus mutans

Streptococcus mutans, a bacterium with high cariogenic potential, coordinates competence for natural transformation and bacteriocin production via the XIP and CSP pheromones. CSP is effective in inducing bacteriocin responses, but not competence in chemically defined media (CDM). This is in contrast to XIP, which is a strong inducer of competence in CDM, but can also stimulate bacteriocin genes as a late response. Inter-connections between the pathways activated by the two pheromones have been characterized in certain detail in S. mutans UA159, but it is mostly unknown whether such findings are representative for the species. In this study, we used bioassays based on luciferase reporters for the bacteriocin gene cipB and the alternative sigma factor sigX to investigate various S. mutans isolates for production and response to CSP and XIP pheromones in CDM. Similar to S. mutans UA159, endogenous CSP was undetectable in the culture supernatants of all tested strains. During optimization of the bioassay using the cipB reporter, we discovered that the acivity of exogenous CSP used as a standard was reduced over time during S. mutans growth. Using a FRET-CSP reporter peptide, we found that S. mutans UA159 was indeed able to degrade CSP, and that such proteolytic activity was not significantly different in isogenic mutants with deletion of the protease gene htrA, or the competence genes sigX, oppD, and comR. CSP proteolysis was also detected in all the wild type strains, indicating that such activity is conserved in S. mutans. For the XIP pheromone, endogenous production was observed in the supernatants of all 34 tested strains at peak concentrations in culture supernatants that varied between 200 nM and 26000 nM. Transformation in the presence of exogenous XIP was detected in all, but one, of the isolates. The efficiency of transformation varied, however, among the different strains, and for those with the highest transformation rates, endogenous XIP peak concentrations in the supernatants were above 2000 nM XIP. We conclude that XIP production and inducing effect on transformation, as well as proteolytic activity leading to the inactivation of CSP are conserved functions among different S. mutans isolates. Understanding the functionality and conservation of pheromone systems in S. mutans may lead to novel strategies to prevent or treat unbalances in oral microbiomes that may favour diseases.

microbiology↗

bioRxiv2019

Mouse IgG2a antibodies specific for the commensal Streptococcus mitis show stronger cross-reactivity with Streptococcus pneumoniae than IgG1 antibodies

Here we show that mouse IgG2a and IgG1 antibodies specific for the commensal Streptococcus mitis cross-react with the pathogen Streptococcus pneumoniae, although the cross-reactivity conferred by IgG2a is stronger than IgG1 antibodies. These findings may have implications for designing S. mitis-based vaccines against pneumococcal infections.

immunology↗