Association between Mycoplasma-specific polymerase chain reaction assay results and oral bacterial contamination of bronchoalveolar lavage fluid samples from dogs with respiratory tract disease: 121 cases (2005-2012)

Objective-To determine whether an association exists between oral bacterial contamination of bronchoalveolar lavage fluid (BALF) and positive PCR assay results for the detection of Mycoplasma spp in BALF samples of dogs with lower respiratory tract (LRT; portion from the trachea to the lungs) disease. Design-Retrospective case series. Animals-121 dogs with LRT disease. Procedures-Medical records from January 2005 to April 2012 were reviewed. Dogs with LRT disease that had BALF samples evaluated by use of Mycoplasma-specific PCR assay, bacterial culture, and cytologic examination were included. Information on signalment, final diagnoses, and BALF testing results was extracted. Results-83 (68.6%) dogs had BALF samples with negative PCR assay results for Mycoplasma spp, and 38 (31.4%) had positive results. The BALF samples with cytologic evidence of oral bacterial contamination were 5.1 times as likely to have positive Mycoplasma-specific PCR assay results as were noncontaminated samples. Compared with hound or herding dogs, other breeds were 13.6 times as likely to have positive PCR assay results. Dogs with bronchitis were less likely than dogs with other LRT diseases to have positive Mycoplasma-specific PCR assay results. No significant association was found between Mycoplasma-specific PCR assay results and bacterial culture results. Conclusions and Clinical Relevance-In dogs with LRT disease, Mycoplasma-specific PCR assay results for BALF samples should be interpreted in terms of possible oral bacterial contamination. Mycoplasma-specific PCR assay of BALF samples from herding dogs, hound dogs, and dogs with bronchitis may be less rewarding than for other dogs with LRT disease.