[Evaluation of in vitro activity of pristinamycin against Haemophilus influenzae].
The activity of pristinamycin against H. influenzae was evaluated using various in vitro tests. Minimal inhibitory concentrations (MICs) were determined by an agar dilution method. The range of MICs was from 0.25 mg/l to 8 mg/l. MIC 50 was 2 mg/l; MIC 90 was 4 mg/l. The activity of component pristinamycin II (PII) is similar to that of pristinamycin and superior to that of component pristinamycin I (PI). Minimal bactericidal concentrations (MBCs) were equal to or two times higher than MICs. Killing curves showed a bactericidal activity obtained after 6 hours at MIC x 2 and MIC x 4 of pristinamycin. Component PII exhibited a bactericidal activity at MIC x 4. The post-antibiotic effect was high with pristinamycin: after two hours of contact with the antibiotic, PAEs were 2 hours with 1 mg/l, from 4 to 6.8 hours with 2 mg/l, and 6.7 hours with 4 mg/l. The PAEs with component PII were from 1 hour to 2 hours at concentrations of 1, 2, or 4 mg/l. Antibiotic resistance to various antibiotics did not influence the antibacterial activity of pristinamycin. At a breakpoint < or = 2 mg/l, more than 85% of the strains were sensitive to pristinamycin. The unimodal distribution of the strains showed the lack of acquired resistance to pristinamycin in these bacterial species.
Dabernat
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Laboratoire de Microbiologie, CHU Purpan, Toulouse, France.
D004305:Dose-Response Relationship, Drug; D004352:Drug Resistance, Microbial; D006193:Haemophilus influenzae / Q000187:drug effects*; D066298:In Vitro Techniques; D014769:Virginiamycin / Q000494:pharmacology*
D014769:Virginiamycin
Evaluation de l'activité in vitro de la pristinamycine sur Haemophilus influenzae.