Salmonellosis is a global health problem, affecting approximately 1.3 billion people annually. Most of these cases are related to food contamination. However, although the majority of Salmonella serovars are pathogenic to humans, animals can be asymptomatic carriers of these bacteria. Nowadays, a wide range of animals is present in human households as pets, including reptiles, amphibians, dogs, cats, ornamental birds, and rodents. Pets contaminate the environment of their owners by shedding the bacteria intermittently in their feaces. In consequence, theyare thought to cause salmonellosis through pet-to-human transmission. Each Salmonella serovar has a different zoonotic potential, which is strongly regulated by stress factors such as transportation, crowding, food deprivation, or temperature. In this review, we summarize the latest reports concerning Salmonella-prevalence and distribution in pets as well as the risk factors and means of prevention of human salmonellosis caused by contact with their pets. Our literature analysis (based on PubMed and Google Scholar databases) is limited to the distribution of Salmonella serovars found in commonly owned pet species. We collected the recent results of studies concerning testing for Salmonella spp. in biological samples, indicating their prevalence in pets, with regard to clinical cases of human salmonellosis.

Non-typhoidal Salmonella (NTS) are globally distributed zoonotic pathogens of major concern within the One Health–One Biofilm framework. Fluoroquinolone-resistant Salmonella strains are included by the World Health Organization (WHO) in the Bacterial Priority Pathogens List as high-risk agents. A key virulence determinant of Salmonella is its ability to form biofilms, which may display multidrug-resistant (MDR) characteristics and contribute to bacterial persistence and treatment failure. Animals, particularly poultry and reptiles, represent important reservoirs of Salmonella, and reptile-associated salmonellosis (RAS) may manifest as extraintestinal infections in humans. In the post-antibiotic era, there is an urgent need to identify effective alternatives to conventional therapies. This review summarizes current knowledge on Salmonella biofilms, with particular attention to their MDR potential, and discusses possible strategies for their prevention and eradication, including specific immunoprophylaxis, bacteriophage therapy, and alternative antimicrobials. The promising antimicrobials include plant-based compounds/extracts, bacteriocins, fatty acids, and synthetic/semi-synthetic substances. The integration of vaccination, phage therapy, and novel anti-biofilm compounds may provide a sustainable alternative to antibiotics in controlling Salmonella infections and aligns with the principles of the One Health approach.

The One Health approach emphasizes the importance of zoonoses due to their pandemic potential, highlighting the need to characterize emerging bacterial pathogens across animal reservoirs. Non-typhoidal Salmonella (NTS) species are among the most common zoonotic agents and can be transmitted by various reservoirs, including reptiles. Both direct and indirect contact with reptiles may result in Reptile-Associated Salmonellosis (RAS), which mainly affects children, immunocompromised individuals, pregnant women, and the elderly. This study aimed to isolate and characterize the Gram-negative intestinal microbiota from free-living snakes in Poland (Natrix natrix, Natrix tessellata, Coronella austriaca, Zamenis longissimus, and Elaphe dione) and to determine the prevalence and virulence potential of Salmonella. Using MALDI-TOF Mass Spectrometry, 432 isolates were identified. Serological analysis of 62 Salmonella isolates revealed 10 distinct O-antigen groups, and rare serovars O:38, O:48, O:57 and others were confirmed. Salmonella isolates were tested for antibiotic susceptibility and resistance to Human Serum; most isolates survived exposure to serum while remaining susceptible to antibiotics. One isolate was classified as multidrug-resistant (MDR), showing resistance to amoxicillin/clavulanic acid, ampicillin, cefuroxime, cephalexin, tigecycline, and fosfomycin. These findings demonstrate that wild snakes in Poland can act as reservoirs of pathogenic and zoonotic Salmonella, emphasizing their epidemiological significance in natural ecosystems.

Salmonella enterica as common pathogens of humans and animals are good model organisms to conduct research on bacterial biology. Because these bacteria can multiply in both the external environments and in the living hosts, they prove their wide adaptability. It has been previously demonstrated that prolonged exposition of Salmonella serotype O48 cells to normal human serum led to an increase in resistance to sera in connection with the synthesis of very long O-antigen. In this work, we have studied the phenotype connected to virulence of Salmonella enterica strains that were subjected to consecutive passages in 50% human serum from platelet-poor plasma (SPPP). We found that eight passages in SPPP may not be enough for the bacteria to become serum-resistant (S. Typhimurium ATCC 14028, S. Senftenberg). Moreover, C1q and C3c complement components bound to Salmonellae (S. Typhimurium ATCC 14028, S. Hammonia) membrane proteins, which composition has been changed after passaging in sera. Interestingly, passages in SPPP generated genetic changes within gene fljB, which translated to cells’ motility (S. Typhimurium ATCC 14028, S. Erlangen). One strain, S. Hammonia exposed to a serum developed a multi-drug resistance (MDR) phenotype and two S. Isaszeg and S. Erlangen tolerance to disinfectants containing quaternary ammonium salts (QAS). Furthermore, colonial morphotypes of the serum adaptants were similar to those produced by starter cultures. These observations suggest that overcoming stressful conditions is manifested on many levels. Despite great phenotypic diversity occurring after prolonged exposition to SPPP, morphotypes of colonies remained unchanged in basic media. This work is an example in which stable morphotypes distinguished by altered virulence can be confusing during laboratory work with life-threatening strains.

Helicobacter pylori is a spiral microorganism capable of inducing a range of gastric diseases. Among different virulence determinants produced by this bacterium, VacA and CagA are of critical importance for the development of these conditions. Taking into account the ability to chronically colonize the stomach, drug-resistant strains of this pathogen can be repeatedly exposed to subinhibitory antibiotic concentrations, which in turn may reduce or enhance their extracellular vesicles (EVs)-derived virulence towards gastric cells. With the use of different experimental techniques, we were the first to demonstrate that subinhibitory antibiotic concentrations modify both the cytotoxicity and cytopathic effect induced by EVs of H. pylori in gastric cells. The ability to induce vacuolization and the hummingbird phenotype in gastric cells presented an antibiotic-specific pattern. At the highest doses tested, all EV types induced phenotypic changes and cytotoxicity in gastric cells; however, the highest lethal effect was observed for EVs isolated from native (antibiotic-unexposed) cells. This suggests that short-term exposure of H. pylori to subinhibitory antibiotic concentrations does not translate into exacerbation of its EVs-dependent virulence. Nevertheless, extensive research in this area is undoubtedly needed to confirm these observations.