Of 35 cats housed together in a single room in a Connecticut shelter, 25 began showing clinical signs of dyspnea, lethargy, and anorexia over 4 to 6 weeks. Cats that became sick were not vaccinated and were less than 2 years of age, while all other cats had been vaccinated for rabies and panleukopenia. Affected animals either died within 48 hours of showing signs or recovered after receiving antibiotics and supportive care. Thirteen cats died; necropsy, histopathology, and microbiology with bacterial isolations were performed on these animals. All cats had similar gross lesions, including moist, edematous, hyperemic, and mottled lungs with focal areas of consolidation. The lungs showed microscopic progression of pneumonia. Bacteriologic testing of the lungs of 7 cats yielded pure hemolytic Escherichia coli in 5 cats, E coli and Bordetella bronchiseptica in 1 cat, and no growth in the seventh cat. Serotyping, DNA isolation, and virulence genotyping revealed all isolates to be hemolytic and belonging to the O4:H5 serotype. All the isolates harbored genes encoding for virulence factors associated with extraintestinal pathogenic E coli (ExPEC) strains. The same strain had infected all the cats, implying a point source clonal outbreak. It was speculated the infection may have been contracted from fecal flora; cats with subclinical infection; contaminated water or food; or infected personnel. While ExPEC strains have been implicated in necrohemorrhagic pneumonia in dogs, this is the first report of ExPEC-induced pneumonia in cats.

COMMENTARY: This article is significant for several reasons: It is the first time an extraintestinal pathogenic strain of E coli has been implicated in causing pneumonia in cats, the disease occurs acutely and is associated with a high mortality rate, and there are zoonotic implications. The study reported that many of the characteristics of the bacterial isolates in these cases were similar to those found in dogs. In addition, previous reports have shown ExPEC isolates from humans and dogs to be indistinguishable. This group of organisms has been associated with urinary tract infection, meningitis, septicemia, and pneumonia in animals and in humans. It is a concern that cats are also susceptible to these pathogens and might be a zoonotic reservoir for them. -- Jennifer L. Schori, VMD

Extraintestinal pathogenic Escherichia coli-induced acute necrotizing pneumonia in cats. Sura R,Van Kruiningen HJ, DebRoy C, et al. ZOONOSES PUBLIC HEALTH 54:307-313, 2007.