in 2000 , a methicillin - resistant staphylococcal aureus ( mrsa ) strain was isolated from a patient admitted to a multisite 1,100-bed tertiary - care teaching hospital in the netherlands . this strain recurred during several outbreaks and spread to a 190-bed nursing home , which is part of the hospital . during a large outbreak in 2003 in the nursing home , 48 patients and 15 nurses were identified as carriers of mrsa , either in their nares , throat , perineum , or a combination of these sites . all mrsa isolates from the outbreaks were sent to the national institute of public health and the environment ( rivm ) for identification and genotyping by pulsed - field gel electrophoresis ( pfge ) . most mrsa had the same pfge pattern , rivm cluster 35 . in 2003 , a 31-year - old female nurse who had psoriasis was identified as an mrsa carrier during the above - mentioned mrsa outbreak . the nurse was treated to eliminate mrsa carriage by applying mupirocin ointment in her nares and washing with a chlorhexidine in ethanol solution for 7 days . initially she became mrsa - negative but later converted to a carrier state again : samples from her nose , throat , perineum , and skin lesions were taken , and mrsa could be isolated from all sites . she was treated for her psoriasis with topical application of triamcinolonacetonide / tetracycline to minimize the skin lesions and thereafter with oral doxycycline and rifampin to eliminate mrsa . however , after some weeks , she became colonized again at all previously mentioned sites . screening her home environment showed that her 1-year - old daughter , who also had psoriasis , was colonized in the nose , throat , and skin lesions . the nares , but not the perineum , of their healthy pet dog were also colonized . samples from nose , throat , and perineum from the patient 's husband were mrsa negative , as were samples from nose , throat , perineum , and skin lesions of the baby 's grandmother , who also had psoriasis and took care of the baby when the mother worked . the staphylococci isolated from the nurse , her child , and the dog were all identified as s. aureus by conventional methods , vitek 2 ( biomrieux , marcy - l'etoile , france ) and martineau polymerase chain reaction ( pcr ) , which targets the tuf gene ( 1 ) . susceptibility testing was performed by using the vitek 2 , according to the manufacturer 's instructions . the isolates were resistant to penicillin g , ofloxacin , trimethoprim - sulfamethoxazole , and fusidic acid and tested susceptible to aminoglycosides , tetracyclines , erythromycin , clindamycin , vancomycin , rifampin , and oxacillin . disk diffusion testing demonstrated susceptibility to mupirocin . because the meca - positive mrsa isolates from previous outbreaks in the nursing home were also resistant to ofloxacin , trimethoprim - sulfamethoxazole , and fusidic acid , and tested either oxacillin resistant or oxacillin susceptible by vitek 2 , the oxacillin resistance of our isolates was also tested by several other methods . the oxacillin screening test ( mueller - hinton agar supplemented with 4% nacl containing oxacillin at a concentration of 6 g / ml ) showed no growth after 24 h and 48 h of incubation at 35c . however , the etest ( ab biodisk , solna , sweden ) showed that the isolates of the dog and the baby had an oxacillin mic of 6 mg / l and the isolate from the nurse had an oxacillin mic of 4 mg / l and could therefore be classified as oxacillin resistant . in addition , a pbp2 slide latex agglutination test ( oxoid , haarlem , netherlands ) was positive for all three isolates . the presence of the meca gene ( 2 ) was demonstrated by a positive meca pcr for all three isolates . characterization of the staphylococcal chromosome cassette mec ( sccmec ) was performed by typing the ccra / b gene complex , the mec complex , and by means of a pcr strategy , which detects structural variants of sccmec covering the entire genetic element ( 26 ) . typing the sccmec of the mrsa strains cultured from the dog and its owner showed that these seemed to be identical ( ccra / b gene type 4 , mec complex class b , and no loci a - h were found ) . pfge showed that all three mrsa isolates ( from the dog , the child , and the nurse ) had indistinguishable patterns and that they belonged to rivm cluster 35 , an epidemic human mrsa cluster . this cluster was the same one cultured previously from patients and contacts in the nursing home during several outbreaks since 2000 . on the basis of these data , we assume that the dog became colonized with the same strain as its owner through contact , and that either the dog or the baby or an unknown source within the nursing home reinfected the nurse . afterward , the mother and the dog received an oral course of doxycycline and rifampin ; the baby was treated with clarithromycin and rifampin . this treatment finally eliminated mrsa from the mother , the child , and the dog . follow - up cultures from the dog and the child were taken for 2 months , the mother was monitored for 9 months , and all cultures remained negative . mrsa is an important cause of human nosocomial and community - acquired infections worldwide . in contrast , few cases of mrsa infections in dogs have been reported ( 811 ) . we report the first known case of human - to - animal transmission of mrsa in the netherlands . in the united states , the transmission of mrsa between a pet dog and its owners has been reported ( 12 ) : a patient with diabetes had recurrent infections of the leg with a mupirocin - resistant mrsa strain , and his wife had cellulitis . culture from their dog 's nose grew an mrsa isolate with the same antimicrobial - resistance pattern and an identical pfge pattern as the isolate cultured from wounds and nares of the couple . further recurrence of the mrsa infection of the couple was only prevented when the dog was no longer an mrsa carrier ( 12 ) . ( 13 ) isolated an mrsa strain with an identical phage type from the nose of a male nurse , his wife , and their pet dog . transmission of mrsa between humans and horses has also been suspected in a veterinary teaching hospital in the united states ( 14 ) . sccmec is a mobile genetic element that carries the meca gene , which mediates methicillin resistance in staphylococci . to date , four sccmec types have been described ( 2,3,6 ) . typing the sccmec of the mrsa in our study showed that they were of an uncommon type , which could not be classified as one of the four sccmec types . oliveira et al . ( 2 ) defined sccmec type iv as harboring ccra / b type 4 in combination with characteristic loci , whereas ito et al . ( 3 ) defined sccmec type iv as the unique combination of the class b mec and type 2 ccr gene complex . our mrsa had ccra / b type 4 and class b mec but no loci . therefore , this mrsa can not be classified in the current system and may present a new sccmec type . this new type may spread successfully , as has been seen with sccmec types i  iv . during the 1960s , mrsa carrying sccmec type i spread across the world , followed by a second wave of mrsa during the late 1970s that carried sccmec ii ; strains with sccmec iii spread during the 1980s , and strains with sccmec type iv have been isolated worldwide since the beginning of the 1990s . recently , an isolate with a ccr5 type was described ( 15 ) , which indicates that additional sccmec types are present in s. aureus . isolates with new sccmec types may be the frontrunners of new waves of mrsa , posing an unknown health threat . automated systems such as vitek 2 are generally reported to be reliable for testing methicillin or oxacillin susceptibility , but the vitek 2 did not detect mrsa in our study . misclassification of meca - positive s. aureus as oxacillin susceptible by the vitek 2 has been reported before by felten et al . this can be explained by their relatively low oxacillin mics ( 4 mg / l and 6 mg / l , respectively ) . the most reliable procedure for detecting mrsa remains the pcr amplification of the meca gene . mrsa in this study was resistant to fluoroquinolones , which is common in mrsa but not in methicillin - susceptible s. aureus ( 17 ) . therefore , fluoroquinolone - resistant s. aureus strains should always be suspected of being mrsa and should be tested for the presence of the meca gene by pcr . in conclusion , dogs and other pets living in close contact with human mrsa carriers can become colonized with mrsa . failure to detect and treat these colonized pets can result in recurrent mrsa colonization or infection in humans . therefore , the risk of pets being the source of unexplained carriage or relapse of infection in humans should be recognized . antimicrobial therapy of healthcare workers and , at the same time , of mrsa carriers and any infected family members or pets , can eliminate recurrent mrsa carriage .
methicillin - resistant staphylococcus aureus ( mrsa ) was cultured from the nose of a healthy dog whose owner was colonized with mrsa while she worked in a dutch nursing home . 
 pulsed - field gel electrophoresis and typing of the staphylococcal chromosome cassette mec ( sccmec ) region showed that both mrsa strains were identical .