Biology subjects

Pereira, A. P.

Publications and source records attributed to Pereira, A. P..

3 recordsLinked to original sources

bioRxiv2025

Single point mutations in global regulatory genes restore cephalosporin resistance in a low-MIC Enterococcus faecium natural isolate

Enterococcus faecium exhibits intrinsic resistance to cephalosporins (CPH), yet the genetic determinants of this phenotype remain incompletely understood. To date, E. faecium strains with low minimum inhibitory concentrations (MICs) to CPH have only been described following genetic manipulation. At Parc Tauli University Hospital, we identified a clinical isolate of ampicillin-susceptible E. faecium (Efm5) that exhibited unusually low-MICs to cefotaxime (1 mg/L), ceftriaxone (3 mg/L), and ceftaroline (0.19 mg/L). Upon single exposure to ceftriaxone (100 mg/L), Efm5 rapidly yielded variants with markedly increased MICs to ceftriaxone (>256 mg/L) and cefotaxime (>32 mg/L), while MICs to ampicillin and ceftaroline were unaffected. Whole-genome sequencing revealed that the high-MIC variants carried single nucleotide polymorphisms (SNPs) leading to non-synonymous mutations in croS, nusG or rpoB genes. Phenotypic assays confirmed that these mutations were associated with ceftriaxone resistance and immunoblots revealed increased expression of penicillin-binding protein 5 (PBP5) in all the high-MIC variants. Transcriptional profiling showed upregulation of the pbp5 operon, which includes ftsW, psr and pbp5, in the croS variants. This study provides the first evidence that E. faecium isolates with low-MICs to CPH can arise in clinical settings without laboratory manipulation, challenging the prevailing notion of absolute intrinsic CPH resistance in this species and offering a novel framework to explore previously unrecognized resistance pathways.

microbiology↗

bioRxiv2022

Evolution of chlorhexidine susceptibility and of the EfrEF operon among Enterococcus faecalis from diverse environments, clones and time spans

Chlorhexidine (CHX) is widely used to control the spread of pathogens (e.g. human/animal clinical settings, ambulatory care, food industry). E. faecalis, a major nosocomial pathogen, is broadly distributed in diverse hosts and environments facilitating its exposure to CHX over the years. Nevertheless, CHX activity against E. faecalis is understudied. Our goal was to assess CHX activity and the variability of ChlR-EfrEF proteins (associated with CHX tolerance) among 673 field isolates and 1784 E. faecalis genomes from PATRIC database from different sources, time spans, clonal lineages and antibiotic resistance profiles. CHX minimum inhibitory concentrations (MICCHX) and minimum bactericidal concentrations (MBCCHX) against E. faecalis presented normal distributions (0.5-64 mg/L). However, more CHX tolerant isolates were detected in the food chain and recent human infections, suggesting an adaptability of E. faecalis populations in settings where CHX is heavily used. Heterogeneity in ChlR-EfrEF sequences was identified, with isolates harboring incomplete ChlR-EfrEF proteins, particularly the EfrE identified in the ST40 clonal lineage, showing low MICCHX ([≤]1mg/L). Distinct ST40-E. faecalis subpopulations carrying truncated and non-truncated EfrE were detected, the former being predominant in human isolates. This study provides a new insight about CHX susceptibility and ChlR-EfrEF variability within diverse E. faecalis populations. The MICCHX/MBCCHX of more tolerant E. faecalis (MICCHX=8mg/L; MBCCHX=64mg/L) remain lower than in-use concentrations of CHX (>500mg/L). However, CHX increasing use combined with concentration gradients occurring in diverse environments potentially selecting multidrug-resistant strains with different CHX susceptibilities, alert to the importance of monitoring the trends of E. faecalis CHX tolerance within a One-Health approach.

microbiology↗

bioRxiv2019

Identification of 2CS-CHXT operon signature of chlorhexidine tolerance among Enterococcus faecium

Chlorhexidine (CHX) is a broad-spectrum antiseptic widely used in community and clinical contexts for many years, recently acquiring higher relevance in nosocomial infections control worldwide. Despite of this, CHX tolerance has been poorly understood among Enterococcus faecium, one of the leading agents causing nosocomial infections. This study provides new phenotypic and molecular data for a better identification of CHX tolerant E. faecium subpopulations in community and clinical contexts. MICCHX distribution of 106 E. faecium suggested the occurrence of tolerant subpopulations in diverse sources (human, animal, food, environment) and phylogenomic backgrounds (clades A1/A2/B), with predominance in clade A1. They carried a specific variant of 2CS-CHXT operon, here identified. It encodes a glucose and an amino-acid-polyamine-organocation family transporters, besides the DNA-binding-response-regulator ChtR with a P102H mutation previously described in only CHX tolerant clade A1 E. faecium, and the ChtS sensor. Combined data from normal MIC distribution and 2CS-CHXT operon characterization supports a tentative epidemiological cut-off (ECOFF) of 8 mg/L to CHX, useful to detect tolerant E. faecium populations in future surveillance studies. The spread of tolerant E. faecium in diverse epidemiological backgrounds alerts for a prudent use of CHX in multiple contexts.\n\nImportanceChlorhexidine is one of the substances included in the World Health Organizations List of Essential Medicines which comprises the safest and most effective medicines needed in global health systems. Although it has been widely applied as a disinfectant and antiseptic since the 1950s in healthcare (skin, hands, mouthwashes, eye drops), its use in hospitals to prevent nosocomial infections has increased worldwide in recent years. Here we provide a comprehensive study on chlorhexidine tolerance among Enterococcus faecium, one of the leading nosocomial agents worldwide, and identified a novel 2CS-CHXT operon as a signature of tolerant strains occurring in diverse phylogenomic groups. Finally, our data allowed to propose a tentative epidemiological cut-off of 8 mg/L, useful to detect tolerant E. faecium populations in future surveillance studies in community and clinical contexts.

microbiology↗