ABSTRACT
BACKGROUND AND OBJECTIVES: Staphylococcus aureus is an important pathogen that can be colonized in the nose and increase the risk of spreading infections in hospitals. The present study aimed at determining the phenotypic and genotypic characterization of S. aureus strains isolated from patients and healthcare workers (HCWs) from a teaching hospital in Isfahan, Iran. MATERIALS AND METHODS: This cross-sectional study was performed on 262 nasal swabs and 23 clinical isolates that were collected from a teaching hospital during February and April 2016. Staphylococcal cassette chromosome mec (SCCmec) and multilocus sequence typing (MLST) were performed for selected isolates. RESULTS: Overall, 23% and 18% of healthcare workers and patients were carriers, respectively. Methicillin-resistant S. aureus (MRSA) rate was 13%, 33% and 52% in nasal HCWs, nasal patients, and clinical samples, respectively. The molecular typing of MRSA isolates revealed that the most common SCCmec type is SCCmec type III (88%). The highest rate of resistance was observed against tetracycline and erythromycin, with 48.7%. The most frequently detected toxin genes among S. aureus isolates were hla (99%) and sea (44%), moreover, pvl genes were detected in (40%) of MRSA isolates. The results of MLST showed 7 different sequence types (STs): ST859 (2/9), ST6 (2/9), ST639 (1/9), ST343 (1/9), ST239 (1/9), ST291 (1/9) and ST25 (1/9). CONCLUSION: Our results revealed that ST clones associated with healthcare-associated MRSA (HA-MRSA) are actively circulating among nasal carriage in our healthcare setting, and thus, effective infection control policies are needed to reduce nasal carriage in healthcare settings.
ABSTRACT
BACKGROUND AND OBJECTIVES: Macrolide, lincosamide and streptogramin B (MLS B) are noteworthy antibiotics for the treatment of Staphylococcus aureus infections. The purpose of this study, was to determine the phenotypic and genotypic characterization of macrolide resistance, among S. aureus, isolated from clinical samples and nasal swabs. MATERIALS AND METHODS: Totally, 162 non-duplicate S. aureus isolates were collected from clinical samples and nasal swabs, from patients and healthcare workers (HCWs), between March 2016 and September 2016, at four teaching hospitals in Isfahan. The antibiotic resistance profile was determined using disk diffusion test and the presence of resistance genes was detected, using PCR. RESULTS: Of 162 S. aureus isolates, 43.8% (71/162) and 34% (55/162) isolates were erythromycin-resistant and methicillin-resistant S. aureus (MRSA), respectively. The prevalence of constitutive MLS B (cMLS B), inducible MLS B (iMLS B), macrolide-streptogramin B-resistant (MS B) and lincosamide-streptogramin-A resistance (LS A) phenotype was 32%, 6%, 6% and 2%, respectively. The most common erythromycin resistance genes, in S. aureus isolates were ermC (35.2%), followed by ermA (20.4%) and msrA (17.3%). Meanwhile, msrA was detected in 43.6% of MRSA isolates. The frequency of coexistence of ermA+ermC+msrA, in S. aureus isolates was 7% and it was only detected in MRSA isolates. CONCLUSION: In the current study, cMLS B phenotype was the most common erythromycin resistance pattern and ermC was the most prevalent gene in erythromycin-resistant isolates. The results revealed that the various mechanisms of erythromycin resistance are expanding in Isfahan.
