TABLE 2.
Detection of MRSA on CHROMagar Staph aureus when it was supplemented with 4 μg of methicillin per ml and at antibiotic susceptibility breakpointsa
| S. aureus typeb | No. of strains tested (n = 114) | % of strains showing positive colored growth on CHROMagar Staph aureus
|
% of strains showing resistance to the following antibiotics at the indicated susceptibility breakpoints (dilution in agar [μg/ml])
|
||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Without MET | With MET or OXc | MET (4) | OX (4) | PEN (0.12) | ERY (0.2) | TET (4) | GEN (1) | GEN (4) | GEN (8) | ||
| MSSA | 68 | 100 | 0 | 0 | 0 | 97e | 15 | 7 | 1 | 0 | 0 |
| HAMRSAd | 34 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 |
| CAMRSAd | 12 | 100 | 30 | 100 | 100 | 100 | 25 | 0 | 0 | 0 | 0 |
a
MET, methicillin; OX, oxacillin; PEN, penicillin; ERY, erythromycin; TET, tetracycline; GEN, gentamicin.
b
MSSA, methicillin-sensitive S. aureus; HAMRSA, hospital-acquired MRSA; CAMRSA, community-acquired MRSA.
c
Addition of 4 μg of methicillin or oxacillin per ml to the chromogenic medium. Similar results were obtained with both drugs.
d
Isolates were tested by the rapid MRSA-Screen latex agglutination test (PBP 2′ Test, DR900M; Oxoid) for the presence of PBP 2a.
e
Three isolates susceptible to penicillin were beta-lactamase enzyme negative.