Three kittens, ages 5, 9, and 17 weeks, were found dead by separate caregivers and were submitted for necropsy. At gross necropsy, each kitten had hemorrhagic or bloody fibrinoserous thoracic fluid and differing distributions of pulmonary consolidation. On histologic examination, the pulmonary lesion in each kitten was similar and was characterized by acute necrotizing and hemorrhagic pneumonia and pleuritis, with numerous intralesional small Gram-negative rods. A pure culture of a distinct serotype of Escherichia coli was identified in lung tissue from each kitten (O4:H5, O6:H7, O6:H5). Lung isolates, genotyped by polymerase chain reaction, carried genes that are characteristic of extraintestinal pathogenic E. coli (ExPEC), including cnf-1, papG allele I, papA, papC, sfa, fim, hlyD, malX, iroN, fyuA, kpsMII, and ompT. Escherichia coli isolates from the intestines of 2 of the kittens were 100% related to the respective lung isolate, as determined by pulsed-field gel electrophoresis. Cultures of fecal samples collected from a clinically healthy cohort population of kittens revealed 16 of 19 tested kittens (84%) to be shedding hemolytic E. coli. Ten different serotypes were identified from 43 hemolytic E. coli fecal isolates from the cohort population, each of which had a genetic profile consistent with that typical of ExPEC. To the authors' knowledge, this is the first report to describe a cluster of isolated cases of pneumonia in kittens caused by distinct serotypes of ExPEC and to evaluate the prevalence of hemolytic E. coli carrying ExPEC-associated genes in the feces of a cohort population of kittens.
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