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J Antimicrob Chemother. 2012 May;67(5):1155-8. doi: 10.1093/jac/dks014. Epub 2012 Feb 9.

In vitro interference of tigecycline at subinhibitory concentrations on biofilm development by Enterococcus faecalis.

Author information

1
Microbiology Department, Hospital Central de la Defensa Gómez-Ulla, Madrid, Spain.

Abstract

OBJECTIVES:

Since biofilm formation is the hallmark of Enterococcus faecalis isolates, the aim of this study was to quantify biofilm formation in the presence of subinhibitory concentrations of tigecycline.

METHODS:

Interference of tigecycline on biofilm formation was spectrophotometrically quantified using 20 biofilm-producing E. faecalis isolates with tigecycline MICs of 0.12 (8 strains) or 0.25 mg/L (12 strains). Biofilm production was measured in antibiotic-free tryptic soy broth supplemented with 1% glucose and compared with biofilm production in the same medium with tigecycline at subinhibitory concentrations (0.25× or 0.5× MIC, similar to trough concentrations in serum or concentrations in the colon after a standard dose) by reading the optical density at 450 nm (OD(450)) after staining with Crystal Violet.

RESULTS:

In the presence of subinhibitory tigecycline concentrations, pooled OD(450) values for the 20 strains [median (IQR)] were significantly lower than those for controls: 0.468 (0.379-0.516) for antibiotic-free controls versus 0.295 (0.200-0.395) for 0.25× MIC tigecycline (P < 0.001) and 0.287 (0.245-0.479) for 0.5× MIC tigecycline (P < 0.001), with significant differences between pooled OD(450) values obtained with each concentration of tigecycline (P = 0.022). In 17 out of 20 (85%) strains the OD(450) obtained with 0.25× MIC tigecycline was significantly (P < 0.05) lower than the basal OD(450), while this occurred in 12 out of 20 (60%) strains with 0.5× MIC.

CONCLUSIONS:

In vitro tigecycline subinhibitory concentrations were able to interfere with biofilm formation by E. faecalis.

PMID:
22323499
DOI:
10.1093/jac/dks014
[Indexed for MEDLINE]

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