The efficacy of an acidified sodium chlorite solution to treat canine Pseudomonas aeruginosa otitis externa - Veterinary Medicine
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The efficacy of an acidified sodium chlorite solution to treat canine Pseudomonas aeruginosa otitis externa
These investigators evaluated an antimicrobial solution for use as an ear cleanser in dogs. All dogs had been treated unsuccessfully with other therapies before entering the study.


Table 1. Antibiotic Susceptibility of Pseudomonas aeruginosa Isolates
Sensitivity profiles of the isolates showed that 88.9% had resistance (full or intermediate) to at least one of the tested antibiotics (Table 1). Bacterial isolates were resistant to a median of nine antibiotics. One isolate was resistant to all 20 of the antibiotics for which it was tested.

Table 2. Ear Clinical Scores and Quantitative Culture Counts Before and After Treatment
The results of the quantitative culture counts and clinical scores are in Table 2. The counts showed no significant difference (P = 0.600) between the initial samples and those taken just before treatment. However, a significant reduction in the quantitative culture counts was noted between the samples taken just before treatment and those taken one hour after the initial treatment (P < 0.0001). A significant decrease was noted when the counts made one hour before treatment were compared with the counts made after 14 days of treatment (P = 0.0023).

Gram's-stained impression smears from 13 of the 27 ears (48.1%) were free of gram-negative rods after 14 days of twice-a-day treatment. Quantitative cultures showed fewer than five colonies formed in 12 of 24 ears (50%) after 14 days of twice-a-day treatment.

Subjective clinical scores improved significantly after 14 days of treatment (P < 0.0001). Clinical scores did not correlate with quantitative culture counts before treatment (r = 0.34, P = 0.90), but were correlated after treatment (r = 0.51, P = 0.02). Two patients showed a pronounced drying and slight peeling of the external ear canal at the end of the treatment period. However, the owners did not perceive any discomfort for their pets associated with this finding, and both patients returned to normal after treatment was discontinued or the cleanser was used at a less frequent interval.

No patients had treatment discontinued because of adverse reactions, and no owners reported patient discomfort from irritation by the cleanser. Two patients with three otitic ears did not have quantitative cultures performed because the owners failed to return after 14 days. These patients had impression smears and clinical scores performed after 20 and 21 days of twice-a-day treatment. Owner compliance was self-reported as excellent despite many of the dogs being uncooperative during the initial ear cleanings.


Sanova cleanser appears to be efficacious in treating dogs with uncomplicated P. aeruginosa otitis externa. Quantitative culture counts, clinical scores, and impression smears showed improvement with twice-a-day treatment. The protocol for quantitative cultures of the ear was used as a way of gathering objective data about the number of colony forming units in the ear exudates. To our knowledge, this type of in vivo quantitative culture count data has not been collected previously. The results of the quantitative culture counts from samples taken from each ear twice before the initial treatment indicate that the sampling process did not significantly alter the number of colonies formed. This was an important consideration and suggests that the significant decrease in culture counts after 14 days of treatment was due to the effect of the Sanova cleanser alone. In the study, 50% of the ears had less than five colonies formed after 14 days of twice-a-day treatment, while 48.1% had negative cytology results. Subjective scores significantly improved with treatment, but did not always correlate with quantitative culture counts. Additional patient data may be required to demonstrate a correlation between the two measures.

All the patients in the study tolerated the ear cleanser well, and no owners expressed dissatisfaction with the cleanser. Although the study included a relatively small number of dogs, it would seem to indicate the product is relatively safe and nonirritating despite its cleaning and disinfecting action.

This study was designed to determine the effect of the cleanser on P. aeruginosa. Although individual isolates from the quantitative cultures were not individually identified, because of the inclusion criteria (Gram's-stained impression smears showing only bacterial morphologies consistent with Pseudomonas species and pure culture isolates of P. aeruginosa documented before quantitative culture collection), it was deemed unlikely that the isolates were other clinically important organisms.7


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