Bacteriostatic or bactericidal effect of linezolid against multiresistant Streptococcus pneumoniae.
The nasopharynx plays a critical role as the reservoir of Streptococcus pneumoniae, including drug-resistant strains particularly in children attending day care centers. A total 58 nasopharyngeal, multiresistant isolates of S. pneumoniae collected from healthy pre-school children were susceptible to linezolid (MIC = 0.25-1 mg/l), irrespective of serotype and drug resistance pattern. The majority of them (about 94%) were sensitive to the bactericidal effect of linezolid with MBCs = 0.5-4 mg/l. One isolate was killed at 8 mg/l of linezolid, while two at higher concentrations of this antibiotic with MBCs 16 or 32 mg/l, suggesting tolerance of linezolid. BOX-PCR fingerprinting data imply that two linezolid-tolerant strains belonged to distinct clones. Linezolid tolerance was confirmed by monitoring the viability of these isolates during exposure to 4 or 20 mg/l of this antibiotic. The linezolid-tolerant strains were sensitive to the bactericidal effect of vancomycin. Linezolid tolerance in clinical isolates of pneumococci may represent a potential therapeutic risk, especially in infections in which bactericidal activity of drug is critical for eradication of bacteria.
Department of Pharmaceutical Microbiology, Medical University of Lublin, Poland. anna.malm@am.lublin.pl
Anna
A
Malm
Izabela
I
Korona-Głowniak
Anna
A
Biernasiuk
Anna
A
Kalasiewicz
Marek
M
Juda
D000081:Acetamides / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002675:Child, Preschool; D024901:Drug Resistance, Multiple, Bacterial; D006801:Humans; D000069349:Linezolid; D008826:Microbial Sensitivity Tests; D023303:Oxazolidinones / Q000494:pharmacology*; D010403:Penicillin Resistance; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D014640:Vancomycin / Q000494:pharmacology
D000081:Acetamides; D000900:Anti-Bacterial Agents; D023303:Oxazolidinones; D014640:Vancomycin; D000069349:Linezolid