Use of a novel selective medium to detect methicillin-resistant Staphylococcus aureus in colonized patients of an intensive care unit.
BACKGROUND
Detection of colonized patients is important for implementing control measures for methicillin-resistant Staphylococcus aureus (MRSA). Laboratory detection of MRSA carriers is increased by the use of selective screening media, helping control dissemination of such organisms.


OBJECTIVE
To evaluate three different media, including selective and nonselective media, in the detection of MRSA from clinical specimens of patients of an intensive care unit (ICU).


METHODS
Adult patients in the ICU of the Hospital Mãe de Deus, Porto Alegre, Brazil.


METHODS
A total of 224 specimens were obtained from the nares of patients and plated on blood agar, mannitol salt agar containing 2 microg/mL of oxacillin (MSAO), and oxacillin resistance screening agar base (ORSAB). The presence of MRSA was investigated in typical colonies growing on the three types of media. Discrepant results were resolved by detection of the mecA gene by polymerase chain reaction and the modified penicillin binding protein known as PBP2'.


RESULTS
MRSA was detected in 32 (14.3%) of 224 specimens. Blood agar, MSAO, and ORSAB detected MRSA in 17, 31, and 28 specimens, respectively. After the coagulase test, no false resistance was observed.


CONCLUSIONS
MSAO and ORSAB performed equivalently in the detection of MRSA of colonized patients and require a single supplementary test (coagulase) to confirm MRSA.
Dias
Cícero Gomes
CG
Department of Microbiology and Parasitology, Fundação Faculdade Federal de Ciências Médicas de Porto Alegre, Porto Alegre, Brazil.
Röpke
Marcos Vinícius Rosa
MV
Superti
Silvana
S
Berquó
Laura
L
d'Azevedo
Pedro
P
D001483:Base Sequence; D002353:Carrier State; D003470:Culture Media; D017931:DNA Primers; D005798:Genes, Bacterial; D006801:Humans; D007362:Intensive Care Units; D016106:Methicillin Resistance; D013203:Staphylococcal Infections / Q000175:diagnosis* / Q000382:microbiology; D013211:Staphylococcus aureus / Q000235:genetics / Q000302:isolation & purification*
D003470:Culture Media; D017931:DNA Primers