Salt tolerance of EMRSA-16 and its effect on the sensitivity of screening cultures.
The salt (NaCl) tolerance of methicillin-resistant Staphylococcus aureus (EMRSA)-16 was compared with 18 other MRSA isolates by an agar incorporation technique. The NaCl minimum inhibitory concentration (MIC) of EMRSA-16 was 7% which compared with an MIC50 of 7%, MIC90 of 10%, range (5.5-10.5%) for the other isolates. Study of the growth kinetics in broth containing NaCl at concentrations up to 10% indicated complete inhibition of growth by 7 and 10% NaCl and partial inhibition by 5%. Addition of EMRSA-16 at inocula of < or = 1 cfu/mL into salt broths revealed lower than expected EMRSA recovery from broths containing 5, 7.5 and 10% NaCl. Two and a half per cent NaCl broths were not inhibitory. Selective broth containing 2.5% NaCl should be considered for use when screening for EMRSA-16.
Jones
E M
EM
Department of Medical Microbiology, Southmead Health Services, NHS Trust, Westbury-on-Trym, Bristol, UK.
Bowker
K E
KE
Cooke
R
R
Marshall
R J
RJ
Reeves
D S
DS
MacGowan
A P
AP
D003470:Culture Media / Q000592:standards*; D006801:Humans; D017053:Infection Control; D008403:Mass Screening; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests / Q000592:standards*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012965:Sodium Chloride; D013211:Staphylococcus aureus / Q000254:growth & development*; D013997:Time Factors
D003470:Culture Media; D012965:Sodium Chloride