Three cats, aged 2 to 11 years, presented to the University of Minnesota Veterinary Diagnostic Laboratory over a 3-year period following euthanasia or death due to respiratory distress. Thoracic radiographs revealed nodular, soft tissue opacities throughout the lung fields in all cases. On postmortem examination, approximately 60% to 80% of the lung parenchyma were expanded by multifocal to coalescing, well-demarcated, beige, semi-firm nodules. Histologically, large numbers of neutrophils, fewer macrophages, fibrin, and cellular and karyorrhectic debris effaced the pulmonary parenchyma. The inflammatory foci contained aggregates of gram-negative cocci. 16s rRNA Sanger sequencing and whole-genome sequencing identified the bacteria isolated from the lung of all cats under aerobic conditions as a novel Neisseria spp. Based on whole-genome sequence analysis, all 3 sequences shared 92.71% and 92.67% average nucleotide identity with closely related Neisseria animaloris NZ LR134440T and Neisseria animaloris GCA 002108605T, respectively. The in silico DNA-DNA hybridization identity compared to our isolates was 46.6% and 33.8% with strain DSM Neisseria zoodegmatis 21642 and strain DSM 21643, respectively. All 3 sequences have less than 95% average nucleotide identity and less than 70% DNA-DNA hybridization identity, suggesting that the 3 isolates are a novel species of the genus Neisseria. Infection with Neisseria spp. induces an embolic pneumonia in cats that radiographically and pathologically resembles a metastatic neoplastic process and should be considered among the etiologic differential diagnoses in cases of infectious pulmonary disease with a disseminated, nodular lung pattern.
Keywords: Neisseria; bacterial pneumonia; bacteriology; feline; lung; next-generation sequencing; veterinary pathology.