Salmonella enterica subsp. arizonae: Zoonotic Infection and qPCR Detection

Salmonella enterica subsp. arizonae belongs to the family Enterobacteriaceae and is classified within the species Salmonella enterica. It is often grouped serologically within Salmonella subgroup IIIa.

This bacterium is a Gram-negative, motile rod with peritrichous flagella. It is facultatively anaerobic and typically ferments glucose with gas production. Most strains do not ferment lactose (some are late fermenters), and the ability to utilize malonate is a useful distinguishing feature in laboratory identification.

A defining characteristic of S. enterica subsp. arizonae is its strong association with reptiles, including snakes, lizards, and turtles, which serve as natural reservoirs. Carriage rates in reptiles can reach 70–90% in some populations. Poultry, particularly turkeys, are also recognized reservoirs.

Human infection is zoonotic and occurs via multiple routes:

• Direct contact: Handling reptiles or contaminated environments, followed by fecal–oral transmission due to inadequate hand hygiene.
• Foodborne transmission: Consumption of contaminated poultry, eggs, or food exposed to contaminated surfaces.
• Environmental exposure: Contact with surfaces contaminated by reptile feces.

High-risk groups include infants, elderly individuals, immunocompromised patients (e.g., HIV infection, transplant recipients, chemotherapy patients), and people with occupational exposure to animals.

The pathogenic mechanisms are similar to other Salmonella species, involving epithelial invasion and endotoxin-mediated inflammation.

Gastroenteritis: The most common presentation, with an incubation period of 6–72 hours. Symptoms include fever, abdominal pain, diarrhea (often watery), nausea, and vomiting. The illness is typically self-limiting and lasts 3–7 days.

Invasive infections: More frequently observed in infants and immunocompromised individuals. The pathogen can enter the bloodstream, causing bacteremia and sepsis, and may disseminate to other organs, resulting in complications such as osteomyelitis, septic arthritis, meningitis, and endocarditis.

Asymptomatic carriage: Some individuals may carry and shed the bacterium without clinical symptoms.

Specimens for diagnosis depend on clinical presentation and may include stool, rectal swabs, blood, bone marrow, or pus from infected sites.

Isolation is performed using selective media such as SS agar or XLD agar. Enrichment culture may be required for sterile site specimens. Biochemical identification includes malonate utilization, hydrogen sulfide production, and lysine decarboxylase positivity.

Serological testing using O and H antisera allows further classification. Molecular methods, including PCR and gene sequencing (e.g., 16S rRNA), provide rapid and accurate identification and are increasingly used in clinical and epidemiological investigations.

For uncomplicated gastroenteritis, antibiotic therapy is generally not recommended. Supportive care, including hydration and electrolyte management, is usually sufficient.

In cases of invasive infection, severe disease, or high-risk patients, antibiotic treatment is required. Third-generation cephalosporins (e.g., ceftriaxone) or fluoroquinolones (e.g., ciprofloxacin) are commonly used, guided by antimicrobial susceptibility testing.

Prevention focuses on hygiene and risk awareness:

• Wash hands thoroughly after handling reptiles or their environments.
• Avoid allowing reptiles in food preparation areas.
• Limit contact between reptiles and high-risk individuals.
• Ensure proper food handling and thorough cooking of poultry and eggs.

Public health education for pet owners and animal handlers is essential to reduce transmission risk.