Occurrence of ESBL and carbapenemase producers and polymyxin- and fosfomycin-resistant Enterobacterales among pets in a veterinary clinic, Egypt

• Rapid diagnostic tests for detecting MDR Enterobacterales from pets. • Occurrence of ESBL, carbapenemase, fosfomycin, and colistin resistance genes. • First case of a mcr-1 - and fosA- producing E. coli isolates from pets in Egypt. • Potential zoonotic transmission risk of multidrug resistance from pets to humans. This study investigates the transmission risk of extended-spectrum ß-lactamase (ESBL) producers, carbapenemase producers, polymyxin-resistant, and fosfomycin-resistant Enterobacterales from healthy and sick dogs and cats in Tanta governate, Nile Delta region, Egypt. A total of 206 different samples were collected from healthy and sick pet animals. Samples were screened for different resistance mechanisms using mSuperCarba, SuperPolymyxin, ChromID ESBL, and SuperFOS selective plates. Antimicrobial susceptibility testing was performed using disk diffusion and broth microdilution techniques. Phenotypic confirmation of resistance traits was done using various rapid diagnostic tests. PCR screening was performed for ESBLs, carbapenemases, mcr , and fosA genes. Molecular typing and clonality evaluation were also performed. The isolates ( Escherichia coli , n=17 and Enterobacter cloacae , n=1), showing acquired multidrug resistance (MDR) phenotype, were identified in 13 animals, accounting for 25% of the total cases. Production of ESBLs was the most prevalent resistance mechanism, the corresponding producers predominantly carrying the bla CTX-M-15 gene (92.3%), while the bla SHV-12 gene was identified in a single isolate. The bla NDM-5 carbapenemase gene was identified in three E. coli isolates, those latter sharing the same sequence type (ST361). A single colistin-resistant E. coli was isolated and carried both mcr-1 and bla CTX-M-15 , while a fosfomycin-resistant E. coli isolate co-produced fosA5 and SHV-12. Notably, 69.2% of resistant bacteria were isolated from sick pets, compared to 30.7% in healthy ones. E. coli isolates showed various sequence types, with ESBL-producing strains belonging to seven different STs and NDM-5 enzyme producers belonging to ST361. This study highlights significant antimicrobial resistance in companion animals and the potential risk for zoonotic transmission.