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Background and purpose: Methicillin-resistant Staphylococcus aureus (MRSA) isolates are the most common pathogen that causes hospital and community acquired infections. Studying on drug resistance, it is important strategy to prevent these types of infections. The use of molecular typing methods is essential for determining the origin of the strains and also in epidemiological investigations. The aim of present study was to survey the molecular characteristics of Staphylococcus aureus (SA), to detect mecA gene, and typing SCCmec in the strains isolated from staffs in Vali-aser and Mousavi hospitals in Zanjan province. Materials and methods: This descriptive study was carried out on 104 SA isolates collected from the clinical samples at Vali-aser and Mousavi hospitals. The identification of all tested isolates were confirmed by Gram's stain, coagulase and manitol salt agar and the isolates were tested for antibiotic resistance by the disc-diffusion method. In addition, the genotypes of SCCmec in the MRSA isolates were determined by multiplex PCR and the results were analyzed using the chi-square. Results: The highest resistance was shown against oxacillin, penicillin, tetracyclin and co-trimoxazole and the most sensitive antibiotics were amikacin and ciprofloxacin and all of the isolates were sensitive to vancomycin and all of the isolates were resistant to at least three classes of antibiotics. Five (8.6%) MRSA strains were SCCmec type I, 11 (19%) were type II, 20 (34.5%) were type III, 17 (29.3) were type IV-a, 1 (1.7%) were type IV-b, 2(3.4%) were type IV-c, 11 (19%) were type IV-d and 18(31%) were type V. Overall, 19 (32.7%) MRSA strains could not be typed. Conclusion: Our findings show that clinical isolates of MRSA in our hospital carrying various types of staphylococcal cassette chromosome mec (SCCmec) types. SCCmec typse III and V were the predominant strain of MRSA identified.

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Background and purpose: Clindamycin is used in treatment of common infections caused by methicillin-resistant Staphylococcus aureus (MRSA). Constitutive or inducible resistance of clindamycin are important factors in choosing that as an effective antibiotic. The aims of this study were to determine inducible resistance clindamycin and analysis of multiple antibiotic resistance profile in clinical isolates of MRSA. Materials and methods: Identification of 250 clinical Staphylococcus aureus isolates was carried out using biochemical and molecular methods. After determining the sensitivity to erythromycin, constitutive or inducible clindamycin resistance were detected by D test according to CLSI guidelines. Results: Out of 250 clinical Staphylococcus aureus isolates, 130 isolates (52%) were resistant to methicillin. Among them, 118 isolates (90.8%) were resistant to erythromycin. Moreover, 105 (88.9%), 9(7.6%) and 4 (3.3%) isolates were identified as constitutive and inducible resistance to clindamycin and MS phenotype, respectively. Conclusion: Inappropriate antibiotic therapy in MRSA infections leads to development of constitutive resistance and treatment failure. Also, due to increasing constitutive resistance in MRSA isolates, performing D test is essential to distinguish the constitutive and inducible resistance and selecting the best treatment.

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Background and purpose: Methicillin-resistant Staphylococcus. aureus (MRSA) is specific strain of S.aureus that is a major cause of nosocomial infection. Nowadays, Vancomycin is the first-line treatment of severe MRSA infections. However, resistance to Vancomycin is reported in the form of Vancomycin-resistant Staphylococcus aureus (VRSA) too. This study aimed at determining the prevalence of MRSA and VRSA in healthcare staff and inpatients.

Materials and methods: The study was performed in 447 healthcare workers and inpatients in Teaching Hospitals, in Sari, Iran, 2015. Staphylococcus aureus were isolated from the subjects using diagnostic tests. Then antibiotic resistance patterns of the isolates was determined by disk diffusion method. E-TEST was used for the methicillin and Vancomycin resistant isolates. Prevalence of mecA resistant gene in the isolates was analyzed by PCR. Finally, Induced resistance to Clindamycin was investigated.

Results: E-TEST showed that 31.31% of the isolates were resistant to methicillin and 16.1% were vancomycin-intermediate S. aureus (VISA). Prevalence of mecA gene in resistant isolates was 96.8%. The highest resistance was detected against Gentamicin (45.5%) and the lowest resistance rates were found against Vancomycin (0%) and Amikacin (14.1%). We also found that 12.9% of MRSA isolates were inducible resistance to Clindamycin.

Conclusion: This study revealed that MRSA isolates have a high resistance to Erythromycin, Clindamycin, Gentamicin, and Ciprofloxacin. Also, a high rate of multidrug-resistant was seen in MRSA isolates. But despite intermediate resistance to Vancomycin, this antibiotic can be used as a valuable drug in treatment of MRSA.

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Background and purpose: The aims of this study were to evaluate the antibiotic resistance
of Healthcare-associated Methicillin-resistant Staphylococcus aureus (HA-MRSA) and Community associated MRSA (CA-MRSA)-resistant strains of Staphylococcus aureus strains and to investigate the frequency of different types of spa typing, SCCmec I, II, III, IV, V, and type IV, among the strains of MRSA isolated from clinical specimens of children in Tehran Children's Medical Center Hospital.
Materials and methods: In this cross-sectional study, antibiotic susceptibility test was performed using Kirby-Baer method according to the CLSI guidelines. Presence of mecA, PVL, spa genes, as well as different types of SCCmec I, II, III, IV, V, and major subtypes of SCCmec IV were investigated using Multiplex PCR.
Results: Among 133 clinical isolates of S. aureus, 70 (53%) were methicillin-susceptible (MSSA) and 63 (47%) were MRSA. The mecA and PVL genes frequency distributions among MRSA strains were 100% and 3.1%, respectively. In the present study, there were 5 SCCmec (I-V) types, indicating wide variations in the hospital investigated. In addition, high prevalence of SCCmec III (30.1%) and III + Iva (23.8%) was observed. Of 63 strains of MRSA, 46 were classified into 11 spa types. The most common type was spa t037 that was found in 53.9% (n= 34) of the strains.
Conclusion: High prevalence of SCCmec III + Iva and emergence of CA-MRSA strains in hospitals can be a serious warning to practitioners and infection control committees.
 

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Background and purpose: Rotational use of antibiotics can decrease antibiotic resistance in Staphylococcus aureus strains. The present study aimed to evaluate the alteration of oxacillin resistance in methicillin-resistant Staphylococcus aureus (MRSA) strain carrying SCCmec III cassette in long-term evolutionary experiments in an antibiotic-free medium.
Materials and methods: In a cross-sectional study, 10 MRSA isolates were identified between September to December 2018 by conventional microbiology methods from clinical isolates of a university hospital. Then, SCCmec typing was carried out using Multiplex PCR. One strain was included in the evolutionary experiment as ancestor and was cultivated for up to 900 generations. Minimum inhibitory concentration (MIC) of oxacillin of the evolved strains was evaluated. The selected strains were compared with the ancestral strain in terms of growth characteristics such as generation time and competitive cultivation.
Results: Out of ten MRSA isolates, six and four were found to harbor SCCmec type III and SCCmec type IV, respectively. One strain with SCCmec III was randomly selected as ancestral strain. The ancestor was resistant to oxacillin while the evolved strains were susceptible. Generation times in the evolved strains were 6-8 minutes shorter than those in the ancestral strain. The evolved strains, with the ratio of 1% in competition experiment, accounted for 20-48% of the final population.
Conclusion: Compared to the ancestor, the evolved strains presented higher fitness in the oxacillin-free environment. The current study indicates the powerful effect of antibiotic rotation strategy on reducing methicillin resistant MRSA.
 

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 Background and purpose: Methicillin-resistant Staphylococcus aureus (MRSA) is one of the major hospital and non-hospital pathogens in children. This meta-analysis and systematic review aimed at exploring the data on prevalence of MRSA in Iranian children.
Materials and methods: Primary articles in English and Persian were searched using the following keywords: prevalence, children, methicillin-resistant staphylococcus aureus (MRSA), and Iran. Electronic databases, including Pubmed, Web of Science, Google Scholar and Iranian databases such as Magiran and SID were searched for articles published in 2007-2019. Qualitative assessment of studies was done using STROBE checklist and data analysis was done in STSTA V11.
Results: A total of 55 articles were identified and 23 met the study inclusion criteria. The prevalence of MRSA in children with S. aureus infection was 22%. The prevalence of community acquired and nosocomial MRSA was 17% and 38%, respectively.
Conclusion: The current meta-analysis showed considerable rates of nosocomial and community acquired MRSA infections among children in Iran. So, pediatricians should consider this issue in empirical treatment.