Gustave, C.-A. | Search bioRxiv

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↗

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↗