Objective: To determine whether tropicamide, fluorescein, and proparacaine applied topically before sample collection affect the quantity or species of bacteria isolated via aerobic culture.
Animals studied: 12 female adult research beagle cross-breed dogs.
Procedures: A conjunctival swab was taken before and after the sequential application of proparacaine, tropicamide, and fluorescein to the same eye (P/T/F) with a five-minute gap between medications. Paired swabs were submitted for aerobic culture. Bacterial enumeration was performed using the spread plate method. Following a one-week washout period, the procedure was repeated using balanced salt solution (BSS). Following a second one-week washout period, the experiment was repeated using ofloxacin 0.3% solution. Colony counts were compared using one-way ANOVA and Tukey post hoc comparison. Bacterial species reduction was compared using a Friedman rank test and Dunn's method.
Results: The bacterial colony count for P/T/F and BSS was significantly higher than the ofloxacin group (p = 0.0052, p = 0.0022). There was no significant difference for colony counts between P/T/F and BSS (p = 0.9295). The most frequently isolated bacteria included: Psychrobacter spp., Staphylococcus spp., Corynebacterium spp., and Streptococcus spp. The bacterial species reduction for P/T/F and BSS was significantly lower than for ofloxacin (p < 0.0001, p = 0.0160). There was no significant difference for species reduction between P/T/F and BSS (p = 0.3749).
Conclusions: The application of proparacaine, tropicamide, and fluorescein did not significantly decrease the amount or species of bacteria isolated from the conjunctiva in this canine population. The application of these solutions prior to ocular swab collection in healthy dogs is unlikely to affect subsequent culture results.
Keywords: antimicrobial; conjunctival swab; fluorescein; in vivo; proparacaine; tropicamide.
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