Salmonella Infantis clones with pESI-like plasmids harboring several virulence and resistance genes have been reported worldwide. In the present study, we compared the population structure of 161 Salmonella Infantis isolates obtained from humans and broilers in Slovenia from 2007 to 2021.

Staphylococcus pseudintermedius is a common cause of skin and soft tissue infections in dogs but can also cause infections in cats and humans. The frequency of methicillin-resistant S. pseudintermedius (MRSP) strains is increasing worldwide. Here, we obtained 43 MRSP isolates from dogs (n = 41), one cat (n = 1) and the small animal clinic environment (n = 1) in Slovenia from the period 2008-2018, which underwent whole-genome sequencing (WGS) and antimicrobial susceptibility testing. Five sequence types (STs) were identified, with ST71 (32/43) and ST551 (8/43) being the predominant. In Slovenia, ST551 was first detected in 2016, whereas a decrease in the frequency of ST71 was observed after 2015. All isolates were multidrug-resistant and most antimicrobial-resistant phenotypes could be linked to acquisition of the corresponding resistance genes or gene mutations. Core-genome multilocus sequence typing (cgMLST) revealed several potential MRSP transmission routes: (i) between two veterinary clinics by a single MRSP-positive dog, (ii) between the environment of a veterinary clinic and a dog, and (iii) between a canine and a feline patient through the contaminated environment of a veterinary clinic. Of the six dogs that were additionally sampled from 14 days to five months after the initial sampling, each harbored the same MRSP strain, suggesting a limited within-host diversity of MRSP in symptomatic dogs. The present results highlight the importance of MRSP-positive dogs in the spread of veterinary care-associated MRSP infections and call for the implementation of strict control measures to reduce MRSP contamination in veterinary clinic environments originating from animal-contact surfaces.

Salmonella enterica subsp. enterica serovar Infantis is the most prevalent serovar in broilers and broiler meat in the European Union. The aim of our study was to test the biofilm formation and antimicrobial effect of disinfectants on genetically characterized S. Infantis isolates from poultry, food, and humans. For the biofilm formation under various temperature conditions (8 °C, 20 °C, and 28 °C) and incubation times (72 h and 168 h), the crystal violet staining method was used. The evaluation of the in vitro antimicrobial effect of Ecocid^® S, ethanol, and hydrogen peroxide was determined using the broth microdilution method. The antibiofilm effect of subinhibitory concentration (1/8 MIC) of disinfectants was then tested on S. Infantis 323/19 strain that had the highest biofilm formation potential. Our results showed that the biofilm formation was strain-specific; however, it was higher at 20 °C and prolonged incubation time. Moreover, strains carrying a pESI plasmid showed higher biofilm formation potential. The antibiofilm potential of disinfectants on S. Infantis 323/19 strain at 20 °C was effective after a shorter incubation time. As shown in our study, more effective precautionary measures should be implemented to ensure biofilm prevention and removal in order to control the S. Infantis occurrence.

In humans, transmission of bacteria causing fatal sepsis in the neonates through mother’s milk has been reported. In dogs, it is believed that bacteria from canine milk are not the primary cause of neonatal infections. Staphylococcus pseudintermedius is colonizing the skin and mucocutaneous junctions in adult dogs and can act as an opportunistic pathogen. This bacterium was previously isolated from the canine milk and, although, its transmission from the dam’s milk to the newborn puppies causing a neonatal sepsis was suggested, this hypothesis has not been confirmed. A 4.5-year-old healthy Boston terrier dam had an elective cesarean section, delivering five normal puppies and one dead runt. Next day, two puppies developed pustules on their legs and around the muzzle. After two more days, strings of blood were noticed in the stool of the biggest puppy that suddenly died later that night. The same day, blood became visible in the feces of all other puppies. Necropsy of the dead puppy revealed a distended abdomen, catarrhal gastroenteritis with lymphadenopathy, dark red and slightly firm lung, mild dilatation of the right heart chamber and congestion of the liver, spleen, pancreas and meninges. The thoracic cavity contained white-yellow slightly opaque exudate, and there was transudate in the abdominal cavity. Histopathology revealed an acute interstitial pneumonia and multifocal myocardial necrosis with mineralization. Bacteriology of the internal organs, body cavity effusions of the dead puppy and dam’s milk revealed a diffuse growth of S. pseudintermedius in pure culture. Whole genome sequencing (WGS) revealed that all isolates belonged to the sequence type 241 and differed in 2–5 single nucleotide polymorphisms; thus, the epidemiological link between the outbreak-associated isolates was confirmed. This is the first report of a confirmed transmission of S. pseudintermedius through dam’s milk causing a neonatal sepsis in a puppy after an elective cesarean section. The epidemiological link between S. pseudintermedius isolates obtained from dam’s milk and internal organs of the affected puppy was confirmed by WGS. Our findings indicate that milk of healthy dams can serve as a reservoir of bacteria that can cause fatal sepsis in the newborn puppies.