Detection of sasX Gene and Distribution of SCCmec Types in Invasive and Non-invasive Coagulase-negative Staphylococci

Abstract

Background: Coagulase-negative staphylococci, which belongto the normal microbiota of the skin and mucous membranes, areopportunistic pathogens. sasX, a newly described protein, is thoughtto play an important role in nasal colonization and methicillinresistant Staphylococcus aureus virulence, and it may be acquiredfrom coagulase-negative staphylococci by horizontal gene transfer. Ithas been considered that understanding the function ofsasX gene mayhelp clarify the relevance of the different adhesion mechanisms in thepathogenesis of infections associated with biofilm.Aims: To investigate the sasX gene presence, staphylococcal cassettechromosome mec types, and antimicrobial resistance patterns ofinvasive and noninvasive coagulase-negative staphylococci isolates.Study Design: Cross-sectional study.Methods: The study included a total of 180 coagulase-negativestaphylococci strains. Non-invasive isolates (n=91) were obtainedfrom the hands of healthy volunteers who do not work at the hospital(n=30), the nasal vestibule of healthy volunteer hospital workers(n=26), and central venous catheter (n=35). Invasive isolates (n=89)were isolated from peripheral blood cultures of inpatients who donot have catheters. All isolates were identified by conventionalmicrobiological methods, automated systems, and, if needed,with matrix-assisted laser desorption/ionization-time of flight.Staphylococcal cassette chromosome mec typing, sasX and mec genedetection, antibiotic susceptibility, and sasX gene sequence analysiswere performed.Results: Peripheral blood, central venous catheter colonization, andnasal vestibule isolates were positive for the sasX gene, whereas handisolates were negative. sasX gene was present in 17 isolates, and nostatistical significance was found between invasive and noninvasiveisolates (p=0.173). Sequence analysis of the sasX genes showed highhomology to related proteins of Staphylococcus phage SPbeta-likeand Staphylococcus epidermidis RP62A. staphylococcal cassettechromosome mec type V was the most prevalent regardless of species.staphylococcal cassette chromosome mec type II was more frequentin invasive isolates and found to be statistically important for invasiveand noninvasive S. epidermidis isolates (p=0.029). Staphylococcushaemolyticus isolates had the overall highest resistance rates.Resistance to ciprofloxacin, trimethoprim-sulfamethoxazole, anderythromycin was found to be higher in isolates from catheter andblood culture. Staphylococcus hominis isolates had the highest rate forinducible clindamycin resistance. None of the isolates were resistantto vancomycin, teicoplanin, and linezolid.Conclusion: The sasX gene is detected in 9.44% of the isolates. Thereis no statistical difference between the sasX-positive and -negativeisolates in terms of antibacterial resistance and the presence of sasXand SCCmec types. Further studies about the role of sasX at virulencein coagulase-negative staphylococci, especially from clinical samplessuch as tracheal aspirate and abscess isolates, and distribution ofstaphylococcal cassette chromosome mec types are needed.