Virulence and the presence of aminoglycoside resistance genes of Staphylococcus haemolyticus strains isolated from clinical specimens

Abstract

We examined thirty methicillin-resistant Staphylococcus haemolyticus isolates cultured from clinical specimens for antibiotic resistance, various important interactions of the bacteria with epithelial cells and putative virulence determinants. All strains were resistant to oxacillin and carried the mecA gene. Aminocyclitol-3′-phosphotransferase (aph(3′)-IIIa) gene encoding nucleotidyltransferases was detected in 43 %, aminocyclitol-6′-acetyltransferase-aminocyclitol-2″-phosphotransferase (aac(6′)/aph(2″)) gene encoding bifunctional acetyltransferases/phosphotransferases in 33 %, aminocyclitol-4′-adenylyltransferase (ant(4′)-Ia) gene encoding phosphotransferases in 20 %. The coexistence of resistance to methicillin and aminoglycosides was investigated in multi-resistant strains. Coexisting (aac(6′)/aph(2″)) and (aph(3′)-IIIa) genes were detected in 33 % of isolates, whereas 63 % of isolates had at least one of these genes. All strains revealed adherence ability and most of them (63 %) were invasive to epithelial cells. Electron microscopy revealed that the bacteria were found in vacuoles inside the cells. We observed that the contact of the bacteria with host epithelial cells is a prerequisite to their cytotoxicity at 5 h-incubation. Culture supernatant of the strains induced a low effect of cytotoxicity at the same time of incubation. Cell-free supernatant of all isolates expressed cytotoxic activity which caused destruction of HEp-2 cells at 24 h. None of the strains was cytotonic towards CHO cells. Among thirty strains, 27 % revealed lipolytic activity, 43 % produced lecithinase and 20 % were positive for proteinase activity. Analyses of cellular morphology and DNA fragmentation exhibited typical characteristic features of those undergoing apoptosis. The Pearson linear test revealed positive correlations between the apoptotic index at 24 h and percentage of cytotoxicity. Our results provided new insights into the mechanisms contributing to the development of S. haemolyticus-associated infections. The bacteria adhered and invaded to non-professional phagocytes. The invasion of epithelial cells by S. haemolyticus could be similar to phagocytosis that requires polymerization of the actin cytoskeleton. The process is inhibited by cytochalasin D. Moreover, they survived within the cells by residing in membrane bound compartments and induced apoptotic cell death.

Distribution of Aminoglycoside Resistance Genes in Coagulase-Negative Staphylococci Isolated From Hospitalized Patients

“…Antibiotic resistance remains a major threat to public health worldwide (10). Although other studies showed that the most prevalent spices was S. epidermidis (11,12), the results of the present study showed that S. hominis and S. haemolyticus, as the most important causes of nosocomial infections, had the highest prevalence (10).…”

“…Antibiotic resistance remains a major threat to public health worldwide (10). Although other studies showed that the most prevalent spices was S. epidermidis (11,12), the results of the present study showed that S. hominis and S. haemolyticus, as the most important causes of nosocomial infections, had the highest prevalence (10). Insufficient hand hygiene and inadequate disinfection and/or sterilization of medical instruments and surfaces may also be assumed as causes of the distribution of coagulase-negative Staphylococci (CoNS) such as S. hominis and S. haemolyticus in the hospital settings (13).…”

Multifactorial mechanisms of the pathogenesis of methicillin-resistant Staphylococcus hominis isolated from bloodstream infections

“…Adhesion and invasion ability were performed in a quantitative assay using the gentamicin/lysostaphin protection method, with modifications (Krzymińska et al 2012a, b, 2015). For the analysis of bacterial adhesion, the infected HeLa cells were lysed using 0.1% Triton X-100.…”

Clonality, virulence and the occurrence of genes encoding antibiotic resistance among Staphylococcus warneri isolates from bloodstream infections

“…Adhesion and invasion of S. warneri to epithelial cells were determined in a gentamicin/lysostaphin protection assay according to the methods of Bur et al (2013) and Krzyminska et al (2015). HeLa cells were infected with bacteria at an m.o.i.…”