Biology subjects

de Lencastre, H.

Publications and source records attributed to de Lencastre, H..

4 recordsLinked to original sources

bioRxiv2022

Spontaneous genomic variation as a survival strategy of nosocomial S. haemolyticus

Staphylococcus haemolyticus is one of the most important nosocomial human pathogens frequently isolated in bloodstream and medical devices related infections. This species is notorious for its multidrug resistance and genome plasticity. However, its mechanisms of evolution and adaptation are still poorly explored. In this study we aimed to characterize the strategies of genetic and phenotypic diversity in S. haemolyticus. Here, we analyzed an invasive S. haemolyticus strain, recovered from a bloodstream infection, for genetic and phenotypic stability after serial passage in vitro (>400 generations) in the absence and presence of sub-inhibitory concentrations of a beta-lactam antibiotic. We performed PFGE of the culture and five colonies at seven time points during stability assays were analyzed for beta-lactams susceptibility, hemolysis, mannitol fermentation and biofilm production. We compared their whole genome regarding chromosomal structure, gene content and mutations and preformed phylogenetic analysis based on core SNPs. We observed a high instability in the PFGE profiles at the different time points during serial passage in vitro in the absence of antibiotic. However, no variation was observed in PFGE patterns in the presence of beta-lactams. Analysis of WGS data for individual colonies collected at different time points showed the occurrence of six large-scale genomic deletions within the oriC environ (36 kbp-348 kbp) in the cell populations analyzed, smaller deletions in non-OriC environ region as well as non-synonymous mutations in clinically relevant genes. The regions of deletion and point mutations included genes encoding amino acid and metal transporters, resistance to environmental stress and beta-lactams, virulence, mannitol fermentation, metabolic processes and IS elements. A parallel variation was additionally detected in clinically significant phenotypic traits such as mannitol fermentation, beta-lactams resistance, hemolysis and biofilm formation. All the genetic variants analyzed were closely related in their core genome (13-292 SNPs). Our results suggest that S. haemolyticus populations are composed of subpopulations of genetic and phenotypic variants that might be affected in antibiotic and stress resistance, specific metabolic processes and virulence. The maintenance of subpopulations in different physiological states might be a strategy to adapt rapidly to a stress situation imposed by the host particularly in the hospital environment.

microbiology↗

bioRxiv2018

Comparative genomic analysis of the emerging pathogen Streptococcus pseudopneumoniae: novel insights into virulence determinants and identification of a novel species-specific molecular marker

Streptococcus pseudopneumoniae is a close relative of the major human pathogen S. pneumoniae. While initially considered as a commensal species, it has been increasingly associated with lower-respiratory tract infections and high prevalence of antimicrobial resistance (AMR). S. pseudopneumoniae is difficult to identify using traditional typing methods due to similarities with S. pneumoniae and other members of the mitis group (SMG). Using phylogenetic and comparative genomic analyses of SMG genomes, we identified a new molecular marker specific for S. pseudopneumoniae and absent from any other bacterial genome sequenced to date. We found that a large number of known virulence and colonization genes are present in the core S. pseudopneumoniae genome and we reveal the impressive number of known and new surface-exposed proteins encoded by this species. Phylogenetic analyses of S. pseudopneumoniae show that specific clades are associated with allelic variants of core proteins. Resistance to tetracycline and macrolides, the two most common resistances, were encoded by Tn916-like integrating conjugative elements and Mega-2. Overall, we found a tight association of genotypic determinants of AMR as well as phenotypic AMR with a specific lineage of S. pseudopneumoniae. Taken together, our results sheds light on the distribution in S. pseudopneumoniae of genes known to be important during invasive disease and colonization and provide insight into features that could contribute to virulence, colonization and adaptation.\n\nImportanceS. pseudopneumoniae is an overlooked pathogen emerging as the causative agent of lower-respiratory tract infections and associated with chronic obstructive pulmonary disease (COPD) and exacerbation of COPD. However, much remains unknown on its clinical importance and epidemiology, mainly due to the lack of specific means to distinguish it from S. pneumoniae. Here, we provide a new molecular marker entirely specific for S. pseudopneumoniae. Furthermore, our research provides a deep analysis of the presence of virulence and colonization genes, as well as AMR determinants in this species. Our results provide crucial information and pave the way for further studies aiming at understanding the pathogenesis and epidemiology of S. pseudopneumoniae.

microbiology↗

bioRxiv2017

Global phylogenomics of multidrug-resistant Staphylococcus aureus sequence type 772: the Bengal Bay clone

The global spread of antimicrobial resistance has been well documented in Gram-negative bacteria and healthcare-associated epidemic pathogens, often emerging from regions with heavy antimicrobial use. However, the degree to which similar processes occur with Gram-positive bacteria in the community setting is less well understood. Here we demonstrate the recent origin and global spread from the Indian subcontinent of a multidrug resistant Staphylococcus aureus lineage, sequence type 772 (Bengal Bay clone). Short-term outbreaks occurred following intercontinental transmission, typically associated with travel and family contacts, but ongoing endemic transmission was uncommon. Instrumental in the emergence of a single dominant clade in the early 1990s was the acquisition of a multidrug resistance integrated plasmid that did not appear to incur a significant fitness cost. The Bengal Bay clone therefore combines the multidrug resistance of traditional healthcare-associated clones with the epidemiological and virulence potential of community-associated clones.

genomics↗

bioRxiv2017

Methicillin resistant Staphylococcus aureus emerged long before the introduction of methicillin in to clinical practice

The spread of drug-resistant bacterial pathogens pose a major threat to global health. It is widely recognised that the widespread use of antibiotics has generated selective pressures that have driven the emergence of resistant strains. Methicillin-resistant Staphylococcus aureus (MRSA) was first observed in 1960, less than one year after the introduction of this second generation {beta}-lactam antibiotic into clinical practice. Epidemiological evidence has always suggested that resistance arose around this period, when the mecA gene encoding methicillin resistance carried on an SCCmec element, was horizontally transferred to an intrinsically sensitive strain of S. aureus. Whole genome sequencing a collection of the very first MRSA isolates allowed us to reconstruct the evolutionary history of the archetypal MRSA. Bayesian phylogenetic reconstruction was applied to infer the time point at which this early MRSA lineage arose and when SCCmec was acquired. MRSA emerged in the mid 1940s, following the acquisition of an ancestral type I SCCmec element, some fourteen years prior to the first therapeutic use of methicillin. Methicillin use was not the original driving factor in the evolution of MRSA as previously thought. Rather it was the widespread use of first generation {beta}-lactams such as penicillin in the years prior to the introduction of methicillin, which selected for S. aureus strains carrying the mecA determinant. Crucially this highlights how new drugs, introduced to circumvent known resistance mechanisms, can be rendered ineffective by unrecognised adaptations in the bacterial population due to the historic selective landscape created by the widespread use of other antibiotics.

microbiology↗