Detection of β-Lactamase-Producing Enterococcus faecalis and Vancomycin-Resistant Enterococcus faecium Isolates in Human Invasive Infections in the Public Hospital of Tandil, Argentina

Molecular characterization and biofilm formation ability of Enterococcus faecium and Enterococcus faecalis bloodstream isolates from a Chinese tertiary hospital in Beijing

To investigate the molecular characteristics and biofilm-forming ability of 116 Enterococcus faecium (Efm) and 72 Enterococcus faecalis (Efs) isolates obtained from patients with bloodstream infections (BSI) at a Chinese hospital between July 2011 and March 2018. The presence of glycopeptide resistance genes and five virulence genes (esp, gelE, asa1, hyl, and cylA) was screened using two multiplex PCR. MLST was used to assess the clonality. Crystal violet staining was used to detect biofilms. Vancomycin resistance was detected in 30.1% of Efm and 2.8% of Efs isolates, respectively. All VRE strains carried the vanA gene. The esp, gelE, asa1, and cylA genes in 72 Efs strains were detected at 62.5%, 84.7%, 84.7%, and 69.4%, respectively. Among the 116 Efm isolates, 74.1% and 25.8% carried esp and hyl, respectively. The esp gene was significantly associated with vancomycin-resistant Efm (VREfm) compared to vancomycin-susceptible Efm (VSEfm). In total, 91.7% of Efs and 20.0% of Efm produced biofilms. Twenty-six STs were identified among the 72 Efs isolates, with ST4 (29.2%) being the predominant. In total, 116 Efm strains were grouped into 26 STs, with ST78 (46.6%) being the predominant. Both VREfm (41.7%) and VSEfm (48.8%) were dominant in ST78. There is no clear evidence suggesting that some STs are associated with vancomycin resistance or biofilm formation. Both Efm and Efs BSI isolates showed a polyclonal pattern with a dominant clone and many unique types, implying the coexistence of clonal dissemination and an influx of new clones. The horizontal transmission of resistance genes may play a more important role in VREfm prevalence than clonal expansion.

Successful expansion of hospital-associated clone of vanA-positive vancomycin-resistant Enterococcus faecalis ST9 to an anthropogenically polluted mangrove in Brazil

Mangrove ecosystems are hotspots of biodiversity, but have been threatened by anthropogenic activities. Vancomycin-resistant enterococci (VRE) are nosocomial bacteria classified as high priority by the World Health Organization (WHO). Herein, we describe the identification and genomic characteristics of a vancomycin-resistant Enterococcus faecalis strain isolated from a highly impacted mangrove ecosystem of the northeastern Brazilian, in 2021. Genomic analysis confirmed the existence of the transposon Tn1546-vanA and clinically relevant antimicrobial resistance genes, such as streptogramins, tetracycline, phenicols, and fluoroquinolones. Virulome analysis identified several genes associated to adherence, immune modulation, biofilm, and exoenzymes production. The UFSEfl strain was assigned to sequence type (ST9), whereas phylogenomic analysis with publicly available genomes from a worldwide confirmed clonal relatedness with a hospital-associated Brazilian clone. Our findings highlight the successful expansion of hospital-associated VRE in a mangrove area and shed light on the need for strengthening genomic surveillance of WHO priority pathogens in these vital ecosystems.

Targeted IS-element sequencing uncovers transposition dynamics during selective pressure in enterococci

Insertion sequences (IS) are simple transposons implicated in the genome evolution of diverse pathogenic bacterial species. Enterococci have emerged as important human intestinal pathogens with newly adapted virulence potential and antibiotic resistance. These genetic features arose in tandem with large-scale genome evolution mediated by mobile elements. Pathoadaptation in enterococci is thought to be mediated in part by the IS element IS256 through gene inactivation and recombination events. However, the regulation of IS256 and the mechanisms controlling its activation are not well understood. Here, we adapt an IS256-specfic deep sequencing method to describe how chronic lytic phage infection drives widespread diversification of IS256 in E. faecalis and how antibiotic exposure is associated with IS256 diversification in E. faecium during a clinical human infection. We show through comparative genomics that IS256 is primarily found in hospital-adapted enterococcal isolates. Analyses of IS256 transposase gene levels reveal that IS256 mobility is regulated at the transcriptional level by multiple mechanisms in E. faecalis, indicating tight control of IS256 activation in the absence of selective pressure. Our findings reveal that stressors such as phages and antibiotic exposure drives rapid genome-scale transposition in the enterococci. IS256 diversification can therefore explain how selective pressures mediate evolution of the enterococcal genome, ultimately leading to the emergence of dominant nosocomial lineages that threaten human health.

The occurrence of antibiotic-resistant bacteria on the clothes of nursery teachers in daycare centres

AIMS

Childcare facilities act as microenvironments that facilitate and promote the selection, spread, and transmission of antibiotic-resistant microorganisms in the community. We focused on the study of antimicrobial resistance and genetic predispositions for β-lactamase production in bacterial isolates from nursery teachers' clothing.

METHODS AND RESULTS

Antimicrobial resistance of bacterial strains belonging to Enterobacteriaceae, Enterococcus, Staphylococcus spp., Pseudomonas spp. and Bacillus spp. isolated from 80 samples of nursery teachers' clothing was determined. The selected ESβL genes were found in 30 (44.1%) of 68 strains examined. The CTX-M type ESβL determinants were detected in 15.4%, 71.5%, and 42.5% of the Enterobacteriaceae, Pseudomonas, and Bacillus isolates, respectively. The OXA-type coding genes were detected only in strains of the genera Pseudomonas (57.1%) and Bacillus (48.6%). Thus, most B. cereus strains were sensitive to the recommended antibiotics used to treat infections caused by these bacteria. Methicillin resistance was phenotypically confirmed in 27 (14.6%) of 185 staphylococcal isolates. Four isolates (2.2%) were identified as MRSA. Vancomycin resistance was not observed in any of the staphylococcal and enterococci strains.

CONCLUSIONS

This study has shown that potential pathogens have been isolated from the clothing of nursery teachers, posing a risk of transmission to children. These clothes should be maintained and properly laundered to avoid cross-contamination and the spread of multidrug-resistant (MDR) bacteria in childcare centres.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provides insight into the route of transmission of MDR microorganisms through the clothing of nursery teachers, to which greater importance should be given in the future. Proper procedures for the cleaning and use of clothing in daycare centres should be clarified and standardised.

Impact of PBP4 Alterations on β-Lactam Resistance and Ceftobiprole Non-Susceptibility Among Enterococcus faecalis Clinical Isolates

Penicillin-resistance among Enterococcus faecalis clinical isolates has been recently associated with overexpression or aminoacidic substitutions in low-affinity PBP4. Ceftobiprole (BPR), a new-generation cephalosporin, is a therapeutic option against E. faecalis. Here, we present evidence that pbp4 gene sequence alterations may influence the expression level of the gene and ceftobiprole binding to PBP4 in E. faecalis clinical isolates showing remarkable MDR-phenotypes, and how this could interfere with BPR in vitro antibacterial and bactericidal activity. Seven E. faecalis strains from bloodstream infections were analyzed for their antibiotic and β-lactam resistance. BPR bactericidal activity was assessed by time-kill analysis; pbp4 genes were sequenced and pbp4 relative expression levels of transcription were performed by RT-qPCR. Five penicillin-resistant ampicillin-susceptible (PRAS) isolates were detected, 4 of which were also BPR non-susceptible (BPR-NS). In the time-kill experiments, BPR exposure resulted in a potent bactericidal activity (3-5 log₁₀ reduction) at the different concentrations tested. pbp4 gene sequence analysis revealed some mutations that may account for the changes in PBP4 affinity and MIC increase in the 4 BPR-NS strains (MICs 4-16 mg/L): the deletion of an adenine (delA) in the promoter region in all PRAS/BPR-NS strains; 12 different amino acid substitutions, 7 of which were next to the PBP catalytic-sites. The most significant were: T418A, located 6 amino acids (aa) upstream of the catalytic-serine included in the ⁴²⁴STFK⁴²⁷motif I; L475Q, 7 aa upstream of the ⁴⁸²SDN⁴⁸⁴motif II; V606A and the novel Y605H, 13/14 aa upstream of the ⁶¹⁹KTGT⁶²²motif III. Taken together, our data showed that elevated BPR MICs were attributable to increased transcription of pbp4 - associated with a single upstream adenine deletion and PBP4 alterations in the catalytic-site motifs – which might interfere with the formation of the BPR/PBP4 complex. pbp4 molecular alterations may account for the changes in PBP4 affinity and MIC increase, without affecting BPR cidal activity. Indeed, our in vitro dynamic analysis by time-kill assays showed that BPR exerted a bactericidal activity against E. faecalis clinical isolates, despite their MDR phenotypes.

Transmission of Antibiotic Resistant Bacteria and Genes: Unveiling the Jigsaw Pieces of a One Health Problem

Antimicrobial Resistance is one of the major Global Health challenges of the twenty-first century, and one of the World Health Organization’s (WHO) top ten global health threats. The evolution of antibiotic resistance among bacterial pathogens requires urgent concerted global efforts under a One Health approach integrating human, animal, and environmental surveillance data. This is crucial to develop efficient control strategies and counteract the spread of multidrug-resistant pathogens. The studies in this Special Issue have evidenced the hidden role of less common species, unusual clones or unexplored niches in the dissemination of antimicrobial resistance between different hosts. They reinforce the need for large-scale surveillance studies tracing and tracking both antibiotic resistance and metal tolerance in different bacterial species.