Community-acquired extended-spectrum and plasmid-mediated ampC beta-lactamase-producing multidrug-resistant Enterobacter cloacae septicaemia in a cat with euthyroid sick syndrome

A 7-year-old castrated male Korean Shorthair cat was referred with lethargy and anorexia. Laboratory examination revealed moderate degenerative changes of peripheral neutrophils on blood smear examination and decreased levels of free and total thyroxine (T₄) as well as bacterial growth on blood culture. Molecular analyses of the 16S ribosomal RNA gene and heat shock protein 60 gene confirmed the bacterium as Enterobacter cloacae. A minimal inhibitory concentration test showed multidrug resistance of the bacterium against 16 antibiotics. Polymerase chain reaction (PCR) and subsequent sequencing specifically for bla_TEM, bla_SHV, bla_CTX-M, and plasmid-mediated ampC genes revealed positive results to bla_TEM-1, bla_CTX-M-15, and plasmid-mediated bla_ACT-1 genes, indicating that the isolated bacterium contains plasmids containing genes encoding extended-spectrum beta-lactamase and plasmid-mediated ampC beta-lactamase. After 1 month of treatment with antibiotics and levothyroxine, the cat’s condition improved; both the thyroid function test and the blood culture showed no abnormalities. This is the first report of community-acquired multidrug-resistant E. cloacae-induced euthyroid sick syndrome in a cat. By the prompt diagnostic procedures and properly selected antibiotic therapy, the cat was recovered from the multidrug-resistant bacterium-induced septicaemia.