Positive Airway Cultures in Dogs and Cats Receiving Mechanical Ventilation for Tick Paralysis

SIMPLE SUMMARY: Aspiration pneumonia is known to be a common complication of tick paralysis in dogs and cats. This study aims to describe the clinical course, and culture and susceptibility profiles, of dogs and cats mechanically ventilated for tick paralysis that had positive airway cultures. A retrospective electronic medical record review was conducted. Twenty-four dogs, and two cats were included. The majority of these cases also had concurrent evidence of aspiration pneumonia based on chest X-rays and arterial blood gas results. Appropriate use of antimicrobials was shown to improve outcome. Clinicians should have an index of suspicion for the development of bacterial pneumonia in dogs and cats undergoing mechanical ventilation for tick paralysis. Empirical antimicrobials appropriate for the likely organisms and based on illness severity should be commenced pending culture and susceptibility testing, after which antimicrobial escalation or de-escalation is indicated to optimise outcomes while adhering to principals of antimicrobial stewardship. ABSTRACT: Animals with tick paralysis often require mechanical ventilation (MV) but previous publications have identified knowledge gaps regarding the development of bacterial pneumonia, and the specific pathogens involved. The objectives of this study were to describe the clinical course and culture and susceptibility profiles of bacteria isolated from airway samples of dogs and cats mechanically ventilated for tick paralysis that had positive airway cultures. Medical records were reviewed, and cases included if they had a positive airway sample culture during MV for tick paralysis. Twenty-four dogs and two cats were included. Most (85%) received empirical antimicrobials before airway sampling. The most common organisms isolated included Staphylococcus spp. (11), Klebsiella spp. (9), Enterococcus faecalis (8), Escherichia coli (6), Enterococcus faecium (3), Pseudomonas aeruginosa (4), and Mycoplasma spp. (3). Evidence of aspiration pneumonia was present in 22/25 (88%) cases that had thoracic radiographs performed. Seventy-seven percent of cases received antimicrobials to which the cultured bacteria were susceptible during hospitalisation. The median duration of MV was 4 days (range 1–10). Most (77%) survived to discharge, 19% were euthanised, and one died. In a multivariable logistic regression analysis it was identified that selection of antimicrobials to which the causative bacteria are susceptible was associated with survival to discharge (Odds ratio 45.8, p = 0.014; 95%CI 1.98–14,808), as was length of MV, with every day an animal is ventilated associated with a 4.7 times increased chance of survival (p = 0.015; 95% CI 1.21–78.4).