In vitro activity of telithromycin against Haemophilus influenzae at epithelial lining fluid concentrationsReport as inadecuate




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BMC Microbiology

, 8:23

First Online: 29 January 2008Received: 13 July 2007Accepted: 29 January 2008

Abstract

BackgroundHaemophilus influenzae is one of the main aetiological agents of community-acquired respiratory tract infections. The primary aim of this study was to evaluate the antibacterial activity of telithromycin against H. influenzae clinical isolates showing different pattern of resistance in comparison with azithromycin and clarithromycin at 1-4 ×, 1-2 ×, 1 ×, 2 ×, 4 × minimum inhibitory concentration MIC and to peak concentrations in epithelial lining fluid ELF. The secondary aim was to determine the influence of CO2 enriched atmosphere on bacterial susceptibility.

ResultsTelithromycin showed high activity against H. influenzae, including strains susceptible to β-lactams n = 200, β-lactamase producer n = 50 and β-lactamase negative ampicillin resistant BLNAR n = 10, with MIC from ≤0.03 to 4 mg-L, and MIC50-MIC90 of 1-2 mg-L with susceptibility rate of 100%, and minimum bactericidal concentrations MBC from 2 to 4-fold higher than the MIC. Azithromycin was the most active tested macrolide range: 0.25 – 4 mg-L; MIC50-MIC90: 1-2 mg-L, comparable to telithromycin, while clarithromycin showed the highest MICs and MBCs range: 0.25 – 8 mg-L; MIC50-MIC90: 2-8 mg-L. In time-kill studies, telithromycin showed a bactericidal activity at the higher concentrations 4 – 2 × MIC and ELF against all the strains, being complete after 12 – 24 hours from drug exposition. At MIC concentrations, at ambient air, bactericidal activity of telithromycin and azithromycin was quite similar at 12 hours, and better than that of clarithromycin. Besides, telithromycin and clarithromycin at ELF concentrations were bactericidal after 12 hours of incubation for most strains, while 24 hours were needed to azithromycin to be bactericidal. Incubation in CO2 significantly influenced the MICs and MBCs, and only slightly the in vitro killing curves.

ConclusionTelithromycin showed an in-vitro potency against H. influenzae comparable to azithromycin, with an in-vitro killing rate more rapid and superior to clarithromycin at 2X-MIC against β-lactamase producers and BLNAR strains, and to azithromycin at ELF concentrations against β-lactamase negative strains. Against all strains, MICs and MBCs were lower in the absence of CO2 for the tested antibiotics, showing an adverse effect of incubation in a CO2 environment. The in-vitro potency together with the tissue concentrations of the antimicrobial, should be considered in predicting efficacy.

Electronic supplementary materialThe online version of this article doi:10.1186-1471-2180-8-23 contains supplementary material, which is available to authorized users.

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Author: Elena De Vecchi - Lucia Nicola - Monica Larosa - Lorenzo Drago

Source: https://link.springer.com/article/10.1186/1471-2180-8-23







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