Diagnostic limitations of oropharyngeal swab cultures and inconsistent presence of secondary bacterial infection in canine aspiration pneumonia.

Oropharyngeal swabs poorly predict bronchoalveolar lavage findings and should not guide antimicrobial therapy in canine aspiration pneumonia.

This prospective study of 30 dogs with aspiration pneumonia (AP) evaluated the diagnostic utility of oropharyngeal (OP) swab cultures compared to bronchoalveolar lavage fluid (BALF) cultures and assessed the frequency of secondary bacterial infection (SBI) using four different definitions. All OP swabs were positive with a median of 4 organisms, while only 16 of 30 BALF cultures were positive with a median of 1 organism. Critically, 91% of OP isolates were not recovered from BALF, demonstrating poor concordance between sample sites. The frequency of SBI varied dramatically (30-77%) depending on the definition applied, ranging from simple culture positivity to requiring specific inflammatory markers or clinical recovery without antimicrobials. The authors concluded that OP swabs are inappropriate surrogates for BALF cultures in AP cases and that not all AP cases require antimicrobial therapy. These findings suggest that current diagnostic approaches may overestimate bacterial infection in canine AP and highlight the need for standardized diagnostic criteria to guide antimicrobial prescribing decisions.

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