Biology subjects

Tristan, A.

Publications and source records attributed to Tristan, A..

4 recordsLinked to original sources

bioRxiv2023

Proteomic assay for rapid characterization of Staphylococcus aureus antimicrobial resistance directly from blood cultures

An efficient management of bloodstream infections requires a fast identification of the pathogen and a determination of its antimicrobial resistance profile. Staphylococcus aureus is among the most common pathogen causing bloodstream infection. A prompt characterization of methicillin-resistant Staphylococcus aureus (MRSA) and their aminoglycoside resistance profile is therefore crucial to quickly adapt the treatment and improve clinical outcomes. Among analytical technologies, targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS) has emerged as a promising tool to detect resistance mechanisms in clinical samples. Herein we present a rapid proteomic workflow to detect and quantify the most clinically relevant antimicrobial resistance effectors in S. aureus: PBP2a, PBP2c, APH(3)-III, ANT(4)-I, and AAC(6)-APH(2), directly from positive blood cultures and in less than 70 minutes. This approach provided 99% sensitivity for PBP2a (n=98/99 strains) detection. Sensitivity was 100% for PBP2c (n=5/5), APH(3)-III (n=16/16) and ANT(4)-I (n=20/20), and 94% for AAC(6)-APH(2) (n=16/17). Across the entire collection, 100% specificity was reported for each of the 5 resistance proteins. Additionally, relative quantification of ANT(4)-I expression allowed to discriminate kanamycin-susceptible and -resistant strains, in strains all harboring the ant(4)-Ia gene. The LC-MS/MS method presented herein demonstrates its ability to provide a reliable and in-depth profiling of S. aureus resistance, directly from positive blood culture and in a short turnaround time, as required in clinical laboratories.

microbiology↗

bioRxiv2020

Potential role of Mercury pollutants in the success of Methicillin-Resistant Staphylococcus aureus USA300 in Latin America

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) lineage known as USA300-North American (NA) has become highly prevalent in North America whilst a USA300 variant known as USA300-LV, harboring a mercury resistance element (COMER), has become dominant in South America. We investigated whether mercury pollution, which is common in South America notably because of artisanal gold mining, may explain the local dominance pattern of USA300-LV. Density-based estimation of epidemic success in 250 genomes of the ST8 lineage revealed that the acquisition of COMER in USA300 progenitors increased success in South American countries but decreased success elsewhere. The fitness of USA300-LV was impaired in vitro compared with USA300-NA, but the addition of sub-inhibitory concentration of mercury provided a strong fitness advantage to USA300-LV and triggered an overexpression of major virulence factors. The success of USA300-LV in South America may result from low-level mercury exposure selecting resistant and virulent strains.

microbiology↗

bioRxiv2019

Necrotizing Soft-Tissue Infections-Staphylococcus aureus -but not Streptococcus pyogenes- isolates display high rate of internalization and cytotoxicity toward human myoblasts

Necrotizing Soft Tissue Infections (NSTIs), often reaching the deep fascia and muscle, are mainly caused by group A Streptococcus (GAS) and to a lesser extent by Staphylococcus aureus (SA). Conversely SA is a leading etiologic agent of pyomyositis suggesting that SA could have a specific tropism for the muscle. To assess the pathogenicity of these two bacterial species for muscles cells in comparison to keratinocytes, adhesion and invasion of NSTI-GAS and NSTI-SA were assessed on these cells. Bloodstream infections (BSI) SA isolates and non-invasive coagulase negative Staphylococci (CNS) isolates were used as controls. SA isolates from NSTI and from BSI exhibited stronger internalization into human keratinocytes and myoblasts than CNS or NSTI-GAS. While the median level of SA internalization culminated at 2% in human keratinocytes, it reached over 30% in human myoblasts due to a higher percentage of infected myoblasts (>11%) as compared to keratinocytes (<3%) assessed by transmission electron microscopy. Higher cytotoxicity for myoblasts of NSTI-SA as compared to BSI-SA, was attributed to higher levels of psm and RNAIII transcripts in NSTI group as compared to hematogenous group. However, the two groups were not discriminated at the genomic level. The cellular basis of high internalization rate in myoblasts was attributed to higher expression of 5{beta}1 integrin in myoblasts as compared to keratinocytes. Major contribution of FnbpAB-integrin 5{beta}1 pathway to internalization was confirmed by isogenic mutants. Our findings suggest the contribution of NSTI-SA severity by its unique propensity to invade and kill myoblasts, a property not shared by NSTI-GAS. ImportanceNecrotizing Soft Tissue Infection (NSTI) is a severe infection caused mainly by group A Streptococcus (GAS) and occasionally by S. aureus (SA); the latter being more often associated with pyomyositis. NSTIs frequently involve the deep fascia and may provoke muscle necrosis. The goal of this study was to determine the tropism and pathogenicity of these two bacterial species for muscle cells. The results revealed a high tropism of SA for myoblasts and myotubes followed by cytotoxicity as opposed to GAS that did not invade these cells. This study uncover a novel mechanism of SA contribution to NSTI with a direct muscle involvement, while in GAS NSTI this is likely indirect, for instance, secondary to vascular occlusion.

molecular biology↗

bioRxiv2017

Demographic fluctuation of community-acquired antibiotic-resistant Staphylococcus aureus lineages: potential role of flimsy antibiotic exposure

Community-acquired (CA) -as opposed to hospital acquired- methicillin-resistant Staphylococcus aureus (MRSA) lineages arose worldwide during the 1990s. To determine which factors, including selective antibiotic pressure, govern the expansion of two major lineages of CA-MRSA, namely \"USA300\" in Northern America and the \"European ST80\" in North Africa, Europe and the Middle East, we explored virulence factor expression, and fitness levels with or without antibiotics. The sampled strains were collected in a temporal window representing various steps of the epidemics, reflecting predicted effective population size as inferred from whole genome analysis. In addition to slight variations in virulence factor expression and biofilm production that might influence the ecological niches of theses lineages, competitive fitness experiments revealed that the biological cost of resistance to methicillin, fusidic-acid and fluoroquinolone is totally reversed in the presence of trace amount of antibiotics. Our results suggest that low-level antibiotics exposure in human and animal environments contributed to the expansion of both European-ST80 and USA300 lineages in community setting. This surge was likely driven by antibiotic (ab)use promoting the accumulation of antibiotics as environmental pollutants. The current results provide a novel link between effective population size increase of a pathogen and a selective advantage conferred by antibiotic resistance.

microbiology↗