WGS of a multidrug resistant Raoultella ornithinolytica isolated from a neonatal septicemic calf

Sepsis is a life-threatening condition in young calves, requiring rapid broad spectrum and bactericidal therapy to maximize survival chances. Only few studies have identified bacteria involved in sepsis in this species and their antimicrobial resistance profile. This report describes neonatal sepsis in a calf caused by multidrug resistant Raoultella ornithinolytica, a pathogen earlier described in human medicine as emerging also causing, amongst others, septicemia. R. ornithinolytica was identified by MALDI-TOF MS in blood cultures of a calf in critically ill condition. Susceptibility testing showed phenotypic resistance against ampicillin, gentamicin, potentiated sulphonamides, streptomycin, tetracyclines and intermediate susceptibility for enrofloxacin. Whole genome sequencing of the isolate confirmed identification as R. ornithinolytica and the multidrug resistant character of the isolate, as antimicrobial resistance genes acting against aminoglycosides, beta-lactam antibiotics, fosfomycin, quinolones, sulphonamides, trimethoprim and tetracyclines were found. The calf recovered after empiric parenteral treatment with enrofloxacin and penicillin for seven days, as well as ketoprofen during the first two stays. To the authors' knowledge, this is the first report of the isolation of R. ornithinolytica from blood cultures in ruminants. It is currently unknown whether animals and farms may act as reservoirs for multidrug resistant R. ornithinolytica strains.