SALMONELLAE

SALMONELLAE

MORPHOLOGY

• Salmonellae are small, Gram-negative, rod-shaped bacteria
• Size: 1-4 μm in length and 0.5-1.5 μm in width
• Motile at 37°C with peritrichous flagella
• Non-motile at room temperature

ANTIGENIC STRUCTURE

• Salmonellae have a lipopolysaccharide (LPS) outer membrane
• LPS contains O-antigens (somatic antigens) and H-antigens (flagellar antigens)
• O-antigens are responsible for serological classification
• H-antigens are responsible for flagellar motility

CLINICAL SYNDROMES CAUSED BY SALMONELLAE IN HUMANS

• Enteric fever (typhoid fever, paratyphoid fever)
• Gastroenteritis (salmonellosis)
• Reactive arthritis
• Iritis and uveitis
• Meningitis and encephalitis (rare)

PATHOGENESIS AND CLINICAL MANIFESTATIONS OF ENTERIC FEVER → Ingestion of contaminated food or water contaminated with Salmonella → Bacteria colonize the small intestine and invade the intestinal epithelial cells → Systemic spread to the lymphoid tissues, Peyer's patches, and liver → Toxins and cytokines trigger fever, headache, abdominal pain, and rash

PATHOGENESIS AND CLINICAL MANIFESTATIONS OF ENTERIC FEVER (CONTINUED) → Invasive phase: Salmonella invades the intestinal epithelial cells and macrophages → Intracellular phase: Salmonella survives inside macrophages and evades the immune system → Systemic phase: Salmonella causes fever, headache, abdominal pain, and rash

LABORATORY DIAGNOSIS OF SALMONELLA INFECTION

• Isolation of Salmonella from stool, blood, or other body fluids
• Identification of Salmonella using biochemical tests (e.g., IMViC)
• Serological tests (e.g., Widal test) for the diagnosis of enteric fever
• PCR (Polymerase Chain Reaction) for rapid detection of Salmonella genetic material

DIAGNOSTIC LABORATORY TESTS FOR SALMONELLA

• Blood cultures for enteric fever
• Stool cultures for gastroenteritis
• Biopsy and histopathology for reactive arthritis and iritis
• Cerebrospinal fluid analysis for meningitis and encephalitis

TREATMENT OF SALMONELLA INFECTION

• Antibiotics (e.g., ciprofloxacin, ampicillin) for enteric fever
• Fluid replacement and supportive care for gastroenteritis
• Anti-inflammatory drugs for reactive arthritis
• Corticosteroids for iritis and uveitis

SALMONELLA LIFE CYCLE

1. Ingestion of contaminated food or water
2. Colonization of the small intestine
3. Invasion of intestinal epithelial cells
4. Systemic spread to lymphoid tissues and liver
5. Survival inside macrophages
6. Release of toxins and cytokines
7. Fever, headache, abdominal pain, and rash

MEMORY TRICK FOR SALMONELLA LIFE CYCLE "INCISIVE SYNDROME" = Ingestion, Colonization, Invasion, Spread, Survival, Toxins, Inflammation, Symptoms, Yucky Rash

NCH POINTS

• Salmonellae are classified into two main groups: Enteritidis and Typhimurium
• Enteric fever is a systemic infection caused by Salmonella Typhi and Salmonella Paratyphi
• Reactive arthritis is a form of seronegative spondyloarthritis

MUHS POINTS

• Salmonella gastroenteritis is a major cause of morbidity worldwide
• Enteric fever is a significant cause of mortality in developing countries
• Salmonella infections can cause reactive arthritis and iritis