
 staphylococcus aureus is a well - adapted human / zoonotic colonizer which can also cause a wide range of diseases and its treatment is becoming more difficult because of increasing rates of drug resistance both in hospital and community settings .
community - acquired methicillin - resistant s. aureus ( ca - mrsa ) has been a subject of interest in the last decade . traditionally , the risk factors for ca - mrsa are chronic illness , history of recurrent use of antibiotics and intravenous drug abuse . moreover , new risk factors such as attendance in military service and day care centers , homosexuality , tattooing , contact sports , sharing soaps and towels , having pets and age  2 years have been proposed , yet several patients with ca - mrsa infections do not have any recognized risk factor for methicillin resistance ( 1 - 6 ) .
in addition to epidemiological differences , ca - mrsa and hospital - acquired methicillin - resistant s. aureus ( ha - mrsa ) differ in antibiotic resistance pattern .
ca - mrsa clones are usually resistant only to -lactams and erythromycin and are usually susceptible to co - trimoxazole , clindamycin and fluoroquinolones ( 1 , 2 , 5 , 7 ) . from a molecular perspective
, ha - mrsa strains usually carry staphylococcal cassette chromosome mec ( sccmec ) types i - iii while ca - mrsa strains carry sccmec types iv or v ( 1 , 4 , 5 , 8) . the aim of this study was to determine the frequency of invasive ca - mrsa in children admitted to the pediatric wards of imam reza and ghaem teaching hospitals .
in this retrospective observational study , data of s. aureus - positive cultures from sterile body sites ( i.e. blood , bone puncture , joint fluid and lymph node aspiration ) was gathered from microbiology laboratory files from march 20 2006 to march 19 2012 .
the community or hospital origin of s. aureus infection was determined by hospital files and telephone communication with the patients parents according to the cdc criteria ( 1 , 6 ) .
during this 6-year period , 23 invasive community - acquired s. aureus cultures were recovered from pediatric patients ( 8 girls and 15 boys ) .
isolates were from blood ( n = 15 ) , synovial fluid ( n = 2 ) , bone puncture ( n = 3 ) and lymph node aspiration ( n = 3 ) .
seventeen isolates ( 74% ) were resistant to methicillin . septic arthritis , osteomyelitis and sepsis
( table 1 ) the resistance rate for erythromycin , cotrimoxazole , ciprofloxacin , tetracycline , and genta - micin was 71% , 53% , 36% , 50% and 44% for ca - mrsa and 0% , 0% , 20% , 50% , 33% for community - acquired methicillin susceptible s. aureus , respectively .
invasive staphylococcal infections like osteomyelitis , septic arthritis and pneumonia are common causes of admission to pediatric wards .
however , based on our daily clinical observations , there is a high incidence of ca - mrsa in our institutions .
this research confirms that the rate of methicillin resistance among invasive community - acquired isolates has been very high ( 74% ) in pediatric patients during the past six years .
there is a high difference in the prevalence of ca - mrsa in different geographic areas .
for example in the us , ca - mrsa prevalence varies between 15% in north eastern states up to 72% in southern states ( 3 ) . in middle east countries ,
the prevalence of ca - mrsa is 62% in saudi arabia ( 9 ) and 52% in turkey ( 10 ) , 11% in south of india ( 11 ) , and 74% in taiwan , ( 12 ) which is close to our estimation in this study .
ca - mrsa was more common in boys in our study ( male / female ratio = 2 ) .
also in a study of the nicu of texas children hospital , most subjects ( 65 of 89 ) were male ( 14 ) .
sex difference in our study can be explained by considering the fact that bone and joint infections are more common in boys ( 15 ) .
resistance of ca - mrsa to non--lactam antibiotics like co - trimoxazole and ciprofloxacin has been reported 0% and 10.7% in the us and 11% and 10% in saudi arabia , respectively ( 8 , 9 ) . in this study ,
high rate of resistance to co - trimoxazole and ciprofloxacin was observed among our invasive ca - mrsa isolates .
interestingly , multidrug resistant ca - mrsa has been recently reported from other asian countries ( 16 ) .
the rate of ca - mrsa in our community is very high and similar to asian ca - mrsa clones which are also resistant to co - trimoxazole and ciprofloxacin .
although further epidemiological and molecular investigations are needed to confirm the results of this study , we recommend that in these two hospitals , for invasive community - acquired s. aureus infections treatment should be started with drugs like clindamycin , vancomycin , linezolid or daptomycin .
 background and objectivecommunity - acquired methicillin - resistant staphylococcus aureus ( ca - mrsa ) is increasingly reported worldwide . 
 we aimed to determine the frequency of invasive ca - mrsa in children admitted to the pediatric wards of imam reza and ghaem hospitals of mashhad , iran.materials and methodsin this retrospective study , data regarding s. aureus isolates from pediatric patients sterile body sites ( i.e. blood  joint , bone and lymph node aspiration ) were retrieved in a time period from march 2006 to march 2012 . 
 disc diffusion data was analyzed to determine the resistance pattern of the isolates , and differentiation between community - acquired and nosocomial s. aureus was done according to cdc guidelines.resultstwenty three invasive community - acquired s. aureus isolates from sterile body sites were identified , of which seventeen ( 74% ) were ca - mrsa . 
 the ca - mrsa isolates showed high frequency of resistance to non--lactam antibiotics ( 71% to erythromycin  
 53% to co - trimoxazole , 44% to gentamicin and 36% to ciprofloxacin).conclusionin this study , the majority of invasive community - acquired s. aureus isolates were found to be ca - mrsa . 
 therefore , we recommend that primary treatment should be with antibiotics such as clindamycin , vancomycin , linezolid or daptomycin for any invasive infection suspected to be caused by s. aureus in these two hospitals . 
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
CONCLUSION