"Salmonella" - what is it, definition of the term
A gram‑negative, facultatively anaerobic, rod‑shaped bacterium of the Enterobacteriaceae family, transmitted via contaminated food, water, or animal contact, responsible for gastroenteritis and occasional systemic infection; it colonizes the intestinal tracts of a wide range of hosts, notably rodents, and can survive in diverse environmental conditions.
Detailed information
The genus comprises Gram‑negative, facultatively anaerobic rods that ferment glucose without gas production. Its genome includes pathogenicity islands encoding type III secretion systems, which inject effector proteins into host cells to manipulate intracellular signaling and facilitate invasion of the intestinal epithelium.
Rodents such as rats and mice serve as natural reservoirs. Colonization occurs primarily in the cecum and colon, where bacteria persist asymptomatically or cause mild enteritis. Shedding in feces contaminates food stores, water sources, and surfaces, creating a route for zoonotic transmission to humans and livestock. Typical prevalence rates in urban rat populations range from 5 % to 20 % depending on environmental sanitation and population density.
Key aspects of rodent‑associated infection:
- Transmission pathways – direct contact with contaminated droppings, ingestion of contaminated feed, inhalation of aerosolized particles during cleaning activities.
- Clinical manifestations in hosts – in rodents, signs may include reduced appetite, weight loss, watery diarrhea, and occasional lethargy; in humans, ingestion leads to gastroenteritis characterized by abdominal cramps, fever, and diarrhea.
- Diagnostic methods – culture on selective agar (e.g., XLD, Hektoen), polymerase chain reaction targeting invA gene, serological assays for specific antigens.
- Control strategies – integrated pest management to reduce rodent numbers, sanitation to eliminate food residues, rodent‑proof storage, and routine testing of environmental samples.
Antimicrobial resistance has emerged as a concern. Strains isolated from rodent populations frequently harbor plasmids conferring resistance to ampicillin, tetracycline, and sulfonamides. Surveillance programs monitor resistance patterns to guide therapeutic choices and inform public‑health interventions.
Preventive measures focus on breaking the contamination cycle. Regular inspection of facilities, prompt removal of carcasses, and disinfection of areas with proven contamination reduce bacterial load. Vaccination of livestock against the pathogen can indirectly lower exposure risk by limiting amplification within animal herds.