Activity of twenty-one antimicrobial agents including l-ofloxacin against quinolone-sensitive and -resistant, and methicillin-sensitive and -resistant Staphylococcus aureus.
There is a need to identify alternative agents to vancomycin for the treatment of infections with methicillin-resistant Staphylococcus aureus (MRSA). One candidate is the l isomer of ofloxacin (DR-3355). We tested 520 frozen MRSA isolates, 248 fresh MRSA isolates, and 375 fresh methicillin-susceptible S. aureus (MSSA) isolates from Minnesota, and 600 clinical isolates of S. aureus (150 MRSA and 450 MSSA) from Illinois. Over 90% of the MRSA strains were resistant to 32 micrograms/ml of oxacillin. Of the 520 frozen MRSA, 24% were susceptible to < or = 2 micrograms/ml ofloxacin, and an additional 74% were susceptible to ofloxacin between 8 and 16 micrograms/ml. More than 98% of all strains were susceptible to < or = 16 micrograms/ml ofloxacin or l-ofloxacin. All the quinolones had a bimodal distribution of in vitro activity, but for only ofloxacin and l-ofloxacin was activity confined to a very narrow range.
Peterson
L R
LR
Clinical Microbiology Section, Northwestern Memorial Hospital, Chicago, IL 60611.
Cooper
I
I
Willard
K E
KE
Fasching
C E
CE
Sinn
L M
LM
Shanholtzer
C J
CJ
Gerding
D N
DN
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000890:Anti-Infective Agents / Q000494:pharmacology; D004353:Drug Evaluation, Preclinical; D004352:Drug Resistance, Microbial; D008712:Methicillin / Q000494:pharmacology; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests; D015242:Ofloxacin / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000187:drug effects*
D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D015242:Ofloxacin; D008712:Methicillin