Cidal activity was studied by killing curves with tinidazole and amoxicillin (alone and in combination) at concentrations similar to those achieved in crevicular fluid (41.2 microg/mL tinidazole and 14.05 microg/mL amoxicillin) against an inoculum of ca. 10(7)colony-forming units/mL of four bacterial groups, each one composed of four different strains of the following periodontal isolates: Prevotella spp., Fusobacterium spp. and Veillonella spp. (anaerobes) and one amoxicillin-susceptible Streptococcus spp. (facultative) in a proportion of 1:1:1:1. When only beta-lactamase-negative Prevotella or Fusobacterium strains were tested, significantly higher reductions were found with amoxicillin (>4 log reduction at 48 h) versus controls.
The presence of beta-lactamase-positive Prevotella spp. or F. nucleatum strains rendered amoxicillin inactive (no reductions at 48 h), with no differences from controls. Amoxicillin+tinidazole produced >3 log reduction at 24h and >4 log reduction at 48 h regardless of the presence or not of beta-lactamase-positive strains.
The presence in crevicular fluid of beta-lactamases produced by beta-lactamase-positive periodontal pathogens may have ecological and therapeutic consequences since it may protect beta-lactamase-negative periodontal pathogens from amoxicillin treatment.
In vitro, tinidazole offered high antianaerobic activity against beta-lactamase-positive and -negative periodontal pathogens, avoiding amoxicillin inactivation.
JournalInternational journal of antimicrobial agents
Int J Antimicrob Agents (1872-7913)
Microbiology Department, School of Medicine, Universidad Complutense, Avenida Complutense s/n, 28040 Madrid, Spain.
Int J Antimicrob Agents. 2009 May;33(5):449-52
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