Technical factors influencing the bactericidal activity of teicoplanin against staphylococci.
Considering 99.9% Killing after 24h of incubation, mean bactericidal activity of teicoplanin against 48 clinical isolates of Staphylococci resulted to be 67.7 micrograms/ml. Fortyfour out of 48 strains (91.7%) resulted tolerant. The high percentage of tolerant was dependent on survivors above the 0.1% allowed in several tube dilutions. Prolonged incubation consistently reduced this number. Only 37.5% of our strains remained tolerant after 48h of incubation. Bactericidal activity of teicoplanin was also significantly influenced by other technical factors. Human serum enhanced the killing of teicoplanin. For 9 strains of Staphylococcus aureus geometric mean MBC decreased from 49.9 muug/ml to 3.9 micrograms/ml (p less than 0.05); also actively growing bacteria demonstrated a higher killing rate, resulting in lower MBCs (mean 3.8 micrograms/ml). Micromethod technique was greatly influenced by the carryover phenomenon. The spot subculture technique is not accurate for bactericidal studies. A standardized technique for determining the minimal bactericidal activity is needed.
Pasticci
M B
MB
Istituto di Clinica delle Malattie Infettive, Università degli Studi di Perugia.
Moretti
A
A
Frongillo
R F
RF
Baldelli
F
F
Moretti
M V
MV
Pauluzzi
S
S
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D006020:Glycopeptides / Q000494:pharmacology; D008826:Microbial Sensitivity Tests / Q000295:instrumentation / Q000379:methods*; D012015:Reference Standards; D013211:Staphylococcus aureus / Q000187:drug effects*; D017334:Teicoplanin
D000900:Anti-Bacterial Agents; D006020:Glycopeptides; D017334:Teicoplanin