Streptococcus pneumoniae in vitro development of resistance to amoxicillin/clavulanic acid, cefaclor, levofloxacin and azithromycin.
The purpose of this study was to determine effect of repeated exposure to sub-inhibitory concentrations of amoxicillin/clavulanic acid on the development of resistance in Streptococcus pneumoniae. Other agents, azithromycin, cefaclor and levofloxacin, were also tested. Twenty S. pneumoniae were passaged for 9 days in the presence of sub-inhibitory concentrations of each antimicrobial agent and MICs determined by NCCLS macro-dilution method. There was a four-fold increase in amoxicillin/clavulanic acid MICs for 2 of 20 isolates. Three of 9 tested against cefaclor, 11 of 13 tested against azithromycin and 9 of 20 tested against levofloxacin showed > or =4-fold increase. Amoxicillin/clavulanic acid was the most stable of the agents tested. Cefaclor MICs were also fairly stable. Azithromycin and levofloxacin MICs were most affected.
Laboratory Specialists, Inc., 1651 A Crossings Parkway, Westlake, OH 44145, USA. amdlmk@aol.com
Laura M
LM
Koeth
Caryn E
CE
Good
Kay A
KA
Saunders
Charles
C
Jakielaszek
D019980:Amoxicillin-Potassium Clavulanate Combination / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017963:Azithromycin / Q000494:pharmacology*; D002433:Cefaclor / Q000494:pharmacology*; D003470:Culture Media; D024901:Drug Resistance, Multiple, Bacterial; D004359:Drug Therapy, Combination; D006801:Humans; D064704:Levofloxacin; D008826:Microbial Sensitivity Tests; D015242:Ofloxacin / Q000494:pharmacology*; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000254:growth & development
D000900:Anti-Bacterial Agents; D003470:Culture Media; D002433:Cefaclor; D064704:Levofloxacin; D019980:Amoxicillin-Potassium Clavulanate Combination; D017963:Azithromycin; D015242:Ofloxacin