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J Antimicrob Chemother. 2007 Jan;59(1):59-65. Epub 2006 Nov 20.

Susceptibility of Actinobacillus actinomycetemcomitans to six antibiotics decreases as biofilm matures.

Author information

1
Department of Microbiology, Tokyo Dental College, 1-2-2 Masago, Mihama-ku, Chiba 261-8502, Japan.

Abstract

OBJECTIVES:

Actinobacillus actinomycetemcomitans is a major causative agent of chronic and aggressive periodontitis. Freshly isolated strains of A. actinomycetemcomitans display rough-type colonies and initiate biofilm formation on glass surfaces. The purpose of this study was to determine the antibiotic susceptibility of A. actinomycetemcomitans biofilm during different phases of maturation.

METHODS:

Using 96-well microtitre plates, we determined the antibiotic susceptibility of rough-type strain 310a to concentrations from 0.1 to 10 mg/L each of erythromycin, ofloxacin, ampicillin, cefalexin, tetracycline and minocycline during biofilm formation. Antibiotics were added at the start of the culture (early phase) and after 24 h of cultivation (mature phase).

RESULTS:

Adding 10 mg/L of ampicillin, 10 mg/L of cefalexin, 0.1 or 1 mg/L of tetracycline, or 0.1 mg/L of minocycline significantly inhibited 310a biofilm formation in the early phase, but not in the mature phase. Although adding 10 mg/L of erythromycin, tetracycline or minocycline reduced biofilm development in the early phase, it enhanced 310a biofilm development in the mature phase. Ofloxacin exerted a strong inhibitory effect in both the early and mature phases of biofilm formation throughout all experiments.

CONCLUSIONS:

The present study demonstrated that the susceptibility of A. actinomycetemcomitans to many antibiotics decreased after biofilm maturation.

PMID:
17118939
DOI:
10.1093/jac/dkl452
[Indexed for MEDLINE]

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