Perturbation of the indigenous rat oral microbiome by ciprofloxacin dosing

Mucosal surfaces such as the gut, vagina and oral cavity are colonized by microbiota that are an integral component of the healthy ecosystem. Recent molecular techniques make it feasible to correlate antimicrobial dosing levels with changes in microbiome composition. The objective of this study was to characterize the rat oral plaque microbiome composition at doses of ciprofloxacin that were considerably above and below nominal in vitro minimal inhibitory concentrations of a variety of gram-positive oral commensal bacteria. We exposed the oral cavities of rats to relatively low (0.1 μg ml(-1) ) and high (20 μg ml(-1)) doses of ciprofloxacin in the drinking water over a 3-day period. Plaque microbiota were characterized using 454 pyrosequencing. The rat indigenous community was dominated by the genera Rothia (74.4%) and Streptococcus (4.7%). Dosing at 0.1 μg ml(-1) was associated with changes in Rothia and Streptococcus species that were not significant, whereas dosing at 20 μg ml(-1) caused a pronounced (significant) reduction in the relative abundance of the Streptococcus genus. Taxonomic independent analysis indicated that the perturbation in the overall community structure attributed to dosing with ciprofloxacin at either the low or high dose was relatively low. The results suggest that it is feasible to use an antimicrobial dosing regimen to selectively target a specific subset of a mucosal microbiome for elimination with minimal perturbation of the entire community.