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Isolation and Identification of Waterborne Antibiotic-Resistant Bacteria and Molecular Characterization of their Antibiotic Resistance Genes
Published on: March 3, 2023
Linezolid-resistant Enterococcus faecium strains isolated from one hospital in Poland -commensals or hospital-adapted
Beata Krawczyk1, Magdalena Wysocka1, Roman Kotłowski1
1Department of Molecular Biotechnology and Microbiology, Faculty of Chemistry, Gdańsk University of Technology, Gdańsk, Poland.
Abstract:
One of the most pressing problems of enterococci infections is occurring resistance to linezolid, which is an antibiotic used in the treatment of infections caused by vancomycin-resistant strains (VRE). The main objective of our research was to investigate the relationship of 19 linezolid-resistant E. faecium isolates from 18 patients hospitalized at Clinical Hospital in Gdansk (Poland). One of the LZDREF was isolated in 2003 (K2003), and another 18 were collected from 2013 to 2017. Genotyping with PCR MP method indicated 14 main unrelated genetic profiles and no association with K2003 strain. Two isolates with the same genotype and genetically closely related two sub-types (2 isolates for each sub-type) were hospital-derived colonizations of patients. The other unrelated genotypes were discussed in the context of colonization, nosocomial infections, and commensal origin, taking into account prior exposure to linezolid. We determined the presence of a point mutation G2576T in six loci of 23S rDNA. There was also a significant correlation (p<0.0015) between the presence of MIC>32 value and the presence of G2576T point mutation on the sixth rrn. We also detected 5 virulence genes for all isolates: gelE, cylA, asa1, hyl, esp. Correlation (p≤0.0001) was observed between the presence of gelE gene encoding gelatinase and two other genes: cylA and asa1 encoding cytolysin and collagen binding protein responsible for aggregation of bacterial cells, respectively. Significant correlation was also observed between asa1 and cfr genes encoding 23S rRNA rybonuclease responsible for resistance to PhLOPSA antibiotics (p = 0.0004). The multidimensional analysis has also shown the correlation between cfr gene and GI-tract (p = 0, 0491), which suggests horizontal gene transfer inside the gut microbiota and the risk of colonization with linezolid-resistant strains without previously being treated with the antibiotic. The patient could have been colonized with LZDRVREF strains which in the absence of competitive microbiota quickly settle in ecological niches favourable for them and pose a risk for the patient.
Insights
Linezolid-resistant Enterococcus faecium strains show diverse genetic profiles and virulence factors. A G2576T mutation in 23S rDNA correlates with high MIC values, suggesting complex resistance mechanisms in hospital-acquired infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Genetics
Background:
- Enterococci infections pose a significant challenge due to increasing resistance to antibiotics like linezolid.
- Vancomycin-resistant Enterococci (VRE) are a particular concern, necessitating effective treatment options.
- Linezolid is a crucial antibiotic for treating VRE infections.
Purpose of the Study:
- To investigate the genetic relatedness and characteristics of linezolid-resistant Enterococcus faecium (LZDREF) isolates.
- To identify potential genetic markers and virulence factors associated with linezolid resistance.
- To understand the transmission and origin of LZDREF in a hospital setting.
Main Methods:
- Genotyping of 19 LZDREF isolates using the PCR-RFLP method.
- Detection of the G2576T point mutation in 23S rDNA genes.
- Screening for five key virulence genes (gelE, cylA, asa1, hyl, esp).
- Correlation analysis of genetic profiles, mutations, virulence genes, and clinical data.
Main Results:
- Fourteen distinct genetic profiles were identified among the LZDREF isolates, with no clear association to an older strain.
- The G2576T point mutation in the 23S rDNA was found in six loci and correlated significantly with high linezolid minimum inhibitory concentration (MIC) values (p<0.0015).
- All isolates harbored five virulence genes (gelE, cylA, asa1, hyl, esp), with significant correlations observed between gelE, cylA, and asa1 (p≤0.0001).
- The cfr gene showed a significant correlation with the asa1 gene (p = 0.0004) and the gastrointestinal tract (p = 0.0491), suggesting horizontal gene transfer.
Conclusions:
- Linezolid resistance in Enterococcus faecium is associated with diverse genetic backgrounds and the presence of specific virulence factors.
- The G2576T mutation in 23S rDNA is a key marker for high-level linezolid resistance.
- Horizontal gene transfer, particularly of the cfr gene within the gut microbiota, may contribute to the spread of linezolid resistance, posing a risk for colonization even in non-treated patients.
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