Molecular characterization and virulence profile of Klebsiella pneumoniae and Klebsiella oxytoca isolated from ill cats and dogs in Portugal

Klebsiella spp. are important pathogens of humans and companion animals such as cats and dogs, capable of causing severe life-threatening diseases. The aim of this study was to characterize the molecular and phenotypic properties of Klebsiella pneumoniae and Klebsiella oxytoca isolated from ill companion animals by whole genome sequencing, followed by in vitro assessment of biofilm formation and in vivo pathogenicity using the Galleria mellonella model. Two LPS O -types were identified for all the K. pneumoniae isolates tested (O3B and O1/O2v2) and only one for K. oxytoca isolates (OL104), and the most common STs found were ST11 and ST266. Furthermore, a high diversity of K -locus types was found for K. pneumoniae (KL102; KL105; KL31, and KL13). Within K. pneumoniae , one specific O/K/ST-types combination ( i.e., KL105-ST11-O1/O2v2) showed results that were of concern, as it exhibited a high inflammatory response at 12 h post -infection in G. mellonella with 80% of the larvae dead at 72 h post -infection. This virulence potential, on the other hand, did not appear to be directly related to the biofilm -forming capacity. Also, virulence and resistance scores obtained for this set of strains did surpass score 1. The present study demonstrated that Klebsiella spp. isolated from companion animals belonging to STs that can cause human infections and present virulence on an invertebrate model. Thus, this study underscores the role of dogs and cats as reservoirs of resistant Klebsiella spp. that could potentially be transmitted to humans.