Abstract
Coagulase-negative staphylococci, particularly Staphylococcus epidermidis, can be regarded as potential reservoirs of resistance genes for pathogenic strains, e.g., Staphylococcus aureus. The aim of this study was to assess the prevalence of different resistance phenotypes to macrolide, lincosamide, and streptogramins B (MLSB) antibiotics among erythromycin-resistant S. epidermidis, together with the evaluation of genes promoting the following different types of MLSB resistance:ermA, ermB, ermC,msrA, mphC, and linA/A’. Susceptibility to spiramycin was also examined. Among 75 erythromycin-resistantS. epidermidis isolates, the most frequent phenotypes were macrolides and streptogramins B (MSB) and constitutive MLSB (cMLSB). Moreover, all strains with the cMLSB phenotype and the majority of inducible MLSB (iMLSB) isolates were resistant to spiramycin, whereas strains with the MSB phenotype were sensitive to this antibiotic. The D-shape zone of inhibition around the clindamycin disc near the spiramycin disc was found for some spiramycin-resistant strains with the iMLSB phenotype, suggesting an induction of resistance to clindamycin by this 16-membered macrolide. The most frequently isolated gene was ermC, irrespective of the MLSB resistance phenotype, whereas the most often noted gene combination wasermC, mphC, linA/A’. The results obtained showed that the genes responsible for different mechanisms of MLSB resistance in S. epidermidis generally coexist, often without the phenotypic expression of each of them.
Highlights
Coagulase-negative staphylococci, Staphylococcus epidermidis, can be regarded as potential reservoirs of resistance genes for pathogenic strains, e.g., Staphylococcus aureus
As a natural part of the microflora, drug resistant strains may be selected during antibiotic therapy, which is a potential source of the resistance genes for pathogenic strains, e.g., Staphylococcus aureus (Reyes et al 2007, Otto 2013, Vitali et al 2014)
Coagulase-negative staphylococci (CoNS) are potential reservoirs of antibiotic resistance genes, which can be transferred to S. aureus in vitro and in vivo (Reyes et al 2007, Otto 2013)
Summary
Coagulase-negative staphylococci, Staphylococcus epidermidis, can be regarded as potential reservoirs of resistance genes for pathogenic strains, e.g., Staphylococcus aureus. Coagulase-negative staphylococci (CoNS), Staphylococcus epidermidis, belong to the microbiota of human skin and the mucosal membrane of the upper respiratory tract, and they express low pathogenic potential as commensals in healthy people (Voung & Otto 2002, Otto 2009). They can be responsible for several serious infections in immunocompromised patients, those associated with biomaterials (e.g., catheters, prosthetics etc.), leading to bacteraemia and sepsis (Ziebuhr et al 2006, Caesy et al 2007, Schoenfelder et al 2010, Castro-Alarcón et al 2011). The following tests were used in the identification of CoNS: the coagulase test tube using rabbit plasma (Biomed, Poland) and API Staph strips (bioMérieux, France)
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