title: Clinical test to detect mecA and antibiotic resistance in Staphylococcus aureus, based on novel biotechnological methods.
abstract: OBJECTIVE
  Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most common organisms isolated from clinical samples, and has been associated with morbidity and mortality among hospitalized patients. The aim of this study was to evaluate the prevalence and antibiotic susceptibility patterns among MRSA and methicillin-sensitive S. aureus (MSSA) isolates collected from four hospitals in Iran.
  
  
  METHODS
  A total of 183 isolates of S. aureus were collected from various clinical specimens of four hospitals in Iran. The isolates were identified by using the conventional biochemical tests. Three methods-oxacillin agar disk diffusion, oxacillin agar screening, and PCR- were applied to determine susceptibility to oxacillin. The conventional disk agar diffusion test was used to evaluate the antibiotic sensitivity of our isolates against 15 antibiotics, according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI).
  
  
  RESULTS
  Of 183 isolates, 77 isolates (42.1%) were found to be MRSA, by the PCR method. The highest antibiotic resistance was found to be against penicillin, co-trimoxazole, erythromycin, and tetracycline respectively. All isolates were susceptible to vancomycin, according to the results of disk agar diffusion. Among other antibiotics, teicoplanin (84%) and fusidic acid (80.5%) were more active against MRSA isolates. For the different methods evaluated, the sensitivities and specificities were as follows: for disk agar diffusion (84.9% and 95.9%) and for agar screening test with oxacillin concentrations of 0.6 μg/ml (70.8% and 97.4%), 4 μg/ml (96.1%and 97.2%) and 6 μg/ml (96% and 96.3%), respectively.
  
  
  CONCLUSIONS
  The results of our study showed that 47% of S. aureus isolates were MRSA. Overall, in this research study, resistance to all test antimicrobial agents in MRSA isolates were higher than that of MSSA isolates. Our results also revealed that 85% of mecA-positive isolates and 15% of mecA-negative isolates were resistant to methicillin; while 96% of mecA-negative isolates were sensitive to methicillin. Meanwhile 4% of mecA-positive isolates were also sensitive to methicillin.
authors.affiliation: a Department of Microbiology , Ahar Branch, Islamic Azad University , Ahar , Iran.
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Shahmohammadi
authors.affiliation: a Department of Microbiology , Ahar Branch, Islamic Azad University , Ahar , Iran.|b Department of Microbiology , School of Medicine, Tabriz University of Medical Sciences , Tabriz , Iran.
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Nahaei
authors.affiliation: d Department of Medical Nanotechnology , Faculty of Advanced Medical Sciences, Tabriz University of Medical Sciences , Tabriz , Iran.
authors.forename: Abolfazl
authors.initials: A
authors.lastname: Akbarzadeh
authors.affiliation: c Liver and Gastrointestinal Disease Research Center, Tabriz University of Medical Sciences , Tabriz , Iran.|d Department of Medical Nanotechnology , Faculty of Advanced Medical Sciences, Tabriz University of Medical Sciences , Tabriz , Iran.
authors.forename: Morteza
authors.initials: M
authors.lastname: Milani
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D006801:Humans; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests / Q000379:methods; D046915:Penicillin-Binding Proteins / Q000235:genetics*; D016133:Polymerase Chain Reaction / Q000379:methods*; D013203:Staphylococcal Infections / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D046915:Penicillin-Binding Proteins; C487789:mecA protein, Staphylococcus aureus
keywords: Methicillin-resistant Staphylococcus aureus (MRSA); Methicillin-sensitive S. aureus (MSSA); Oxacillin agar screening; PCR; mecA