although long considered a typical nosocomial pathogen , methicillin - resistant 
 staphylococcus aureus ( mrsa ) has recently emerged as a cause of 
 infections in communities . currently , two main categories are recognized : 
 hospital - associated ( ha - mrsa ) and community - associated mrsa ( ca - mrsa ) . infections caused by 
 ca - mrsa begin in communities in people lacking known ha - mrsa risk factors , including recent 
 hospital contact , surgery , residence in a long - term care facility , dialysis or the presence 
 of invasive medical devices . ca - mrsa 
 causes skin and soft - tissue infection ( ssti ) , which accounts for more than half of all 
 ssti - related s. aureus isolates in an outpatient setting in the united 
 states . while severe and life - threatening infections such as necrotizing 
 pneumonia , necrotizing fasciitis and severe sepsis represent rare cases , these life - threatening infections can 
 become virulent strains with the presence of panton - valentine leukocidin ( pvl ) toxin . in japan hisata surveyed 818 
 healthy children s nasal cavities and found mrsa among 35 children ( 4.3% ) . two thirds of 
 these 35 were categorized as ca - mrsa by genetic characteristics . , ssti was infected with either 
 methicillin - sensitive staphylococcus aureus ( mssa ) or streptococcus 
 pyogen . currently , clinicians have to consider ca - mrsa as a causative organism 
 and should become familiar with treatment for this infection . the patient is a previously healthy 38-year - old male mechanic with a lacerated wound to his 
 right index finger . the finger was injured one hour earlier , when heavy machinery 
 accidentally fell at his workplace . he stated he was not currently taking any medication and had not recently been to a 
 hospital . examination of the patient revealed normal findingsexcept for the proximal region 
 of his right index finger , which revealed a laceration 15 mm long , with slight swelling of 
 the area . an x - ray of the right index finger confirmed a fracture line of the proximal 
 phalanx without any deep tissue pathology . the wound was dressed on 
 the third and seventh days , with no sign of infection or swelling . however , ten days after the injury , the sutured wound showed marked swelling and redness , 
 so the patient was admitted with a diagnosis of suppurative cellulitis of the right index 
 finger . physical examination of the patient revealed a temperature of 38.2c , blood pressure 
 of 154/84 mmhg and a pulse rate of 110 beats / min . the right index finger and dorsum of the 
 right hand were warm , swollen and erythematous . routine laboratory findings on admission disclosed normal values , except for a 
 white blood cell count of 16,800 , with 83.3% neutrophils and 3.68 c - reactive protein . the wound was debrided with saline , and then 
 2 g of cefazolin was administered intravenously twice a day for 10 days . however , the results of culture of the pus from the day of admission were received 
 on day 10 and revealed 10 to 20 colonies of gram - positive cocci . the cocci proved to be 
 mrsa , susceptible to vancomycin and chloramphenicol , intermediately resistant to minocycline 
 and fosfomycin and resistant to ampicillin - sulbactam , amoxicillin , cefazolin , gentamicin , 
 clindamycin , erythromycin , imipenem , trimethoprim - sulfamethoxazole and levofloxacin . the 
 patient was given 0.5 g of vancomycin intravenously for an additional four days after the 
 tenth day of hospitalization . many investigators have identified isolates that cause ca - mrsa infection by using the 
 epidemiological definition based on the patient s lack of healthcare risk factors in their 
 medical history , a definition advocated by the centers for disease control and prevention 
 ( cdc ) in 2000 . as ca - mrsa strains vary in genetic and antimicrobial resistance 
 profile , ca - mrsa is classified by the type of antimicrobial resistance profiles and genetic 
 characteristics . the genetic profile was not evaluated in this case because it is not 
 commercially available . in regard to antimicrobial resistance profiles , however , the 
 patient s strain shows a multi - resistant pattern to microbes , suggesting a similarity with 
 the pattern of ha - mrsa . ca - mrsa is generally more susceptible to antibiotics than ha - mrsa . 
 while ha - mrsa tends to be multi - resistant , ca - mrsa is usually susceptible to narrow - spectrum 
 non--lactams such as fluoroquinolones , clindamycin , 
 trimethoprim - sulfamethoxazole ( tmp - smx ) and tetracyclines . the antimicrobial resistance finding of our patient s isolates an 
 ha - mrsa pattern may be interpreted to imply that the culture was contaminated by ha - mrsa in 
 the hospital . however , the culture yielded 10 to 20 colonies of gram - positive cocci 
 identifying mrsa in this case , which is too many to suggest contamination of the culture . ca - mrsa strains are gradually becoming entrenched as nosocomial pathogens and vice 
 versa . nevertheless , in this 
 case , mrsa was isolated from an outpatient with no known exposure to the health care 
 environment in a community hospital , and this serves as a warning to primary care physicians 
 of the emergence of mrsa in outpatient settings . the infection route of mrsa is speculated to be mrsa colonization of the patient , although 
 no supporting data was obtained in this case . s. aureus colonization of the 
 nares , hands and groin occurs in about 30% of healthy adults . ca - mrsa colonizes about 3% of healthy individuals and is a risk 
 factor for the development of a ca - mrsa ssti . although elimination of s. aureus nasal 
 colonization with intranasal mupirocin in a hospital setting can reduce nosocomial 
 infection , there are limited data showing that reducing ca - mrsa colonization 
 decreases invasive disease . investigators have previously shown that despite decreasing 
 ca - mrsa colonization through eradication , the rates of ssti are not affected . therefore , although ca - mrsa has tropism for colonizing 
 human skin , it is not clear that this colonization must precede infection . it is more likely that ca - mrsa is 
 acquired from shared fomites or close contact with colonized or infected individuals . this 
 has led us to speculate that the family members of the patient discussed might constitute a 
 route of infection in relation to compromised skin integrity ( lacerations , abrasions and 
 burns ) , which is a risk factor for ca - mrsa . as the present patient demonstrated systemic toxicity , we treated him with antibiotics 
 intravenously . empiric antibiotic therapy might be considered for those who are 
 immunocompromised or who present with a large surrounding area of cellulitis , systemic 
 toxicity or lymphangitis . the patient 
 improved with administration of cefazolin , although the mrsa was resistant to cefazolin in 
 the sensitivity study . one potential explanation for this result is that incision and 
 drainage ( i&d ) without cefazolin had been effective . in the treatment of ca - mrsa skin 
 infection , there is evidence suggesting that i&d is more important than antibiotic 
 susceptibility in immunocompetent patients . one piece of data shows that most patients 
 receiving i&d followed by antibiotic treatment for ca - mrsa skin infection had equivalent 
 clinical outcomes whether the antibiotic prescribed was effective or not . in an immunocompetent pediatric 
 population with i&d for abscesses smaller than 5 cm , children receiving no antibiotics 
 or antibiotics to which the pathogen was resistant fared as well as those receiving 
 effective antibiotics . moreover , in a 
 large community prospective study of skin and soft - tissue infection , 57% of ca - mrsa 
 infections were resistant to the empirically prescribed antibiotic . fortunately , neither 
 susceptibility nor resistance to antibiotics prescribed had any effect on patient 
 outcomes . perhaps a large , rigorous , 
 randomized controlled trial will be needed to show physicians whether antibiotics are 
 effective or not . in conclusion , the patient with suppurative cellulitis due to ca - mrsa was successfully 
 treated with i&d followed by antibiotics . as mrsa has emerged in the outpatient setting , 
 ca - mrsa should be considered a possible etiologic agent of ssti in healthy individuals with 
 no classical risk factors for acquisition of mrsa .
infections caused by methicillin - resistant staphylococcus aureus ( mrsa ) 
 have recently occurred in communities in people lacking known healthcare risk factors . 
 this mrsa infection is referred to as community - associated mrsa ( ca - mrsa ) infection , and 
 is distinct from hospital - associated mrsa infection , which occurs in people with risk 
 factors . 
 we experienced a patient diagnosed with ca - mrsa cellulitis , as culture of pus 
 revealed mrsa and he had not been exposed to healthcare environments for the past year . 
 the patient was a previously healthy 38-year - old man with suppurative cellulitis in his 
 right index finger following injury to the finger at his worksite . 
 the cellulitis was 
 successfully managed with incision and drainage ( i&d ) , followed by cefazolin during a 
 10-day clinical course , although the patient s mrsa strain was resistant to cefazolin . 
 there are several reports that suggest that i&d followed by antibiotic treatment for 
 ca - mrsa skin infection produces equivalent clinical outcomes , whether the antibiotic 
 prescribed was effective or not . given that mrsa emerged in an outpatient setting , ca - mrsa 
 should be considered a possible etiology of skin infection in healthy individuals with no 
 classical risk factors for acquisition of mrsa .