Genetic Characterization of a Vancomycin-Resistant Staphylococcus aureus Isolate from the Respiratory Tract of a Patient in a University Hospital in Northeastern Iran

Abstract

Emergence of vancomycin-intermediate Staphylococcus aureus (VISA) and vancomycin-resistant S. aureus (VRSA) strains has led to global concerns about treatments for staphylococcal infections. These strains are currently rare even though there is an upward trend in their reported incidence. Therefore, appropriate screening and epidemiological evaluation of VRSA strains can affect future global health care policies. Isolates of Staphylococcus aureus were obtained from various clinical samples and were then evaluated with agar screening, disk diffusion, and MIC methods to determine resistance to vancomycin and methicillin. After confirmation of the isolated VRSA strain, genetic analysis was performed by evaluating mecA and vanA gene presence, SCCmec, agr, and spa types, and toxin profiles. Multilocus sequence typing (MLST) and plasmid analysis were also performed. The VRSA strain was resistant to oxacillin (MIC of 128 g/ml) and vancomycin (MIC of 512 g/ml). Disk diffusion antimicrobial susceptibility tests showed resistance to oxacillin, vancomycin, levofloxacin, ciprofloxacin, trimethoprim-sulfamethoxazole, clindamycin, rifampin, and tetracycline. The isolate was susceptible to minocycline and gentamicin. PCRs were positive for the mecA and vanA genes. Other genetic characteristics include SCCmec type III, agr I, spa type t037, and sequence type (ST) 1283. The plasmid profile shows five plasmids with a size of ϳ1.7 kb to >10 kb. The isolated VRSA strain was obtained from a critically ill hospitalized patient. Genetic analysis of this strain suggested that the strain was a methicillin-resistant S. aureus (MRSA) clone endemic in Asia that underwent some genetic changes, such as mutation in the gmk gene and acquisition of the vanA gene.

The Comparison ofStaphylococcus aureusIsolated From Blood and Wound Specimens for Genes Encoding Polysaccharide Intercellular Adhesion (PIA)

“…Resistance to vancomycin has been reported from several parts of the world in sporadic conditions, similar to Iran (17,18). In our study, MRSA isolates were resistant to more antibiotics when compared to MSSA strains, and this difference between the two groups was significant for several antibiotics.…”

High Prevalence of Icaadbc Genes Responsible for Biofilm Formation in Clinical Isolates of Staphylococcus aureus From Hospitalized Children

“…All the studied isolates were susceptible to vancomycin and linezolid; although these drugs are the last choices for treatment of S. aureus infections, resistance to vancomycin has been sporadically reported from some areas of the world, similar to Iran (18,19). Moreover, resistance to linezolid was detected in 19 of 20 isolates studied by Armin et al (20).…”

Several Virulence Factors of Multidrug-Resistant Staphylococcus aureus Isolates From Hospitalized Patients in Tehran

“…Infections caused by MRSA often prove difficult to treat because of high levels of resistance to multiple antibiotics as a result of both intrinsic and acquired mechanisms (3). Moreover, in recent years vancomycin resistance have made treatment of these isolates very difficult (4). Drug resistance in S. aureus is occurred by complex genetic arrays such as the staphylococcal cassette chromosome mec (SCCmec) elements for methicillin-resistance and likewise all the beta-lactam antibiotics via production of new Penicillin Binding Protein2a (PBP2a) (5).…”