Temperature effect on cephalothin sensitivity of methicillin-resistant Staphylococcus aureus.
Nineteen methicillin-resistant Staphylococcus aureus isolates from clinical specimens were tested for cephalothin sensitivity by disk diffusion and tube-dilution methods using incubation temperatures of 35 C and 30 C. Resistant colonies were observed to grow within the zones of antibiotic inhibition for 17 of the 19 isolates at 30 C but not at 35 C incubation. Twenty control strains known to be methicillin-sensitive did not show these resistant colonies at 30 C. Five of the methicillin-resistant isolates were sensitive, one of intermediate sensitivity to cephalothin, and the rest were resistent by tube-dilution testing at 35 C. At 30 C, however, two isolates were of intermediate sensitivity, and the rest were resistant to cephalothin by tube-dilution testing. These observations strongly suggest that the 30 C incubation temperature is more reliable in detecting in-vitro resistance of methicillin-resistant strains of Staphylococcus aureus to cephalothin in agar as well as in liquid media.
D002512:Cephalothin / Q000494:pharmacology*; D006801:Humans; D008712:Methicillin / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D010403:Penicillin Resistance; D013210:Staphylococcus / Q000187:drug effects*; D013696:Temperature
D008712:Methicillin; D002512:Cephalothin