54. Genus Salmonella. Causative agents of typhoid and paratyphoid diseases.
Covers the general characteristics of Salmonella, including its Gram-negative rod morphology, biochemical and culture features, and serological classification by O, H and Vi antigens. It then lists the pathogenic species and serotypes, virulence factors in a summary table, transmission and reservoirs, and the clinical course of typhoid, paratyphoid and septicaemia. Laboratory diagnosis, treatment with antibiotic choices and resistance, and typhoid vaccines with hygiene measures close the note.
Topic 54 of 113 in the MU Sofia syllabus for Microbiology (Dental Medicine, Year 2). The free AceMed note covers it in 9 sections, about 332 words (3 min of reading), with 13 flashcards.
In this note
Genus Salmonella – Causative agents of Typhoid and Paratyphoid Diseases
I. General Characteristics
II. Classification and Types
III. Virulence Factors
IV. Transmission and Epidemiology
V. Clinical Features and Diseases
VI. Laboratory Diagnosis
VII. Treatment
VIII. Prevention and Control
I. General Characteristics
Family: Enterobacteriaceae
Gram Staining: Gram-negative rods
Motility: Motile (peritrichous flagella)
Spores: Non-spore forming
Capsule: No microcapsule usually (S. Typhi has one)
Pili: Present – used for adhesion
Oxygen Requirement: Facultative anaerobes
Biochemical:
Oxidase (-)
Lactose (-)
H2S (+) (except S. Paratyphi A)
Media:
Non-fastidious – grow on MacConkey agar, Deoxycholate Citrate Agar (DCA)
Produce rounded, transparent colonies on MacConkey agar
On DCA – black-centered colonies (due to H2S production)
Serologic Classification:
Based on O (somatic), H (flagellar), and Vi (capsular) antigens
II. Classification and Types
Species:
Salmonella enterica
Salmonella bongori
Pathogenic Serotypes:
S. Typhi – Human-specific pathogen
S. Paratyphi A, B, C – Milder illness
S. Enteritidis, S. Typhimurium – Cause toxicoinfections and gastroenteritis
