Salmonella

• What type of bacteria is Salmonella?

  Gram-negative, flagellated, unencapsulated, and non-spore forming bacilli
• What are the two species of the genus Salmonella based on DNA homology and host range?

  Salmonella Enterica and Salmonella Bongori
• How many subspecies is Salmonella Enterica divided into?

  Six subspecies
• Which subgroup of Salmonella Enterica contains most pathogenic strains for humans?

  Subgroup I of S. Enterica subsp. enterica
• How many serotypes of Salmonella are currently described?

  More than 2400 serotypes
• How is a Salmonella serotype named?

  It is named as S. Enterica subsp. enterica serotype Enteritidis
• What are the three clinical syndromes produced by Salmonella infections in humans?

  Gastroenteritis, enteric fever, or focal disease
• What is the motility characteristic of Salmonella bacilli?

  They are motile with peritrichous flagella
• At what temperature are Salmonella bacilli killed in 1 hour?

  55ºC
• What is the role of lipopolysaccharide (LPS) in Salmonella?

  LPS functions as an endotoxin and is important for virulence
• What are the three components of the LPS complex in Salmonella?

  Outer O polysaccharide coat, R core, and inner lipid A coat
• What is the significance of the O-antigen specificity in Salmonella?

  It helps to determine the virulence of the bacteria
• What is the effect of endotoxins produced by Salmonella?

  They cause fever and activate the serum complement and clotting systems
• What are the three major antigens possessed by Salmonella?

  H (flagellar), O (somatic), and surface antigens (Vi, M, N, and F antigens)
• What is the stability of the H antigen in Salmonella?

  It is heat and alcohol labile
• How is the O antigen characterized in terms of stability?

  It is heat and alcohol stable
• What happens to the Vi antigen during boiling?

  It is destroyed by boiling within 1 hour
• What is the primary habitat of S. Typhi and S. Paratyphi?

  They colonize the small intestine, especially ileac mucosa in infected human hosts
• What is the role of carriers in the transmission of enteric fever?

  Carriers are important reservoirs of infection for enteric fever
• What percentage of patients become chronic carriers of Salmonella?

  About 2–4% of patients
• What is the infectious dose for S. Typhi infections?

  The infectious dose is low, making person-to-person spread common
• How does the epidemiology of typhoid fever differ between developed and developing countries?

  Typhoid fever has been virtually eliminated in developed countries due to improved sanitation
• What are the antigenic variations observed in Salmonellae?

  • OH–O variation: Loss of flagella in flagellated strains
  • V–W variation: Expression and loss of Vi antigen
  • S–R variation: Change from smooth to rough morphology and loss of virulence
  • Phase variation: Alternation between phase 1 and phase 2 flagellar antigens
  • Variation in O antigen: Changes due to lysogenization with converting phages
• What are the main sources of infection for S. Typhi?

  • Contaminated food and water
  • Infected food handlers
  • Poor personal hygiene
• What are the clinical syndromes caused by Salmonella infections?

  • Gastroenteritis
  • Enteric fever
  • Focal disease
• What are the characteristics of Salmonella as pathogens?

  • Ubiquitous in humans and animals
  • Colonize various hosts including poultry, reptiles, and humans
  • Cause significant economic losses in livestock
• What are the key factors in the epidemiology of enteric fever?

  • Endemic in developing countries with poor sanitation
  • High incidence in the Indian subcontinent and Southeast Asia
  • Significant global morbidity and mortality rates
• What are the characteristics of the carrier state in Salmonella infections?

  • Convalescent, temporary, and chronic carriers
  • Chronic carriers excrete bacilli for over a year
  • Higher prevalence in women and older individuals
• What are the main reservoirs for nontyphoidal Salmonella?

  • Poultry
  • Livestock
  • Reptiles
  • Pets
• What are the effects of Salmonella's lipopolysaccharide (LPS) on the immune system?

  • Functions as an endotoxin
  • Causes fever and activates immune responses
  • Important in the pathogenesis of infections
• What are the implications of antigenic variation in Salmonella?

  • Allows evasion of host immune response
  • Facilitates adaptation to different environments
  • Impacts vaccine development and effectiveness
• What are the clinical implications of the Vi antigen in Salmonella?

  • Related to virulence
  • Present in specific serotypes like S. Typhi
  • Affects agglutination by specific antisera
• What are the characteristics of the O antigen in Salmonella?

  • Integral part of the cell wall
  • Heat and alcohol stable
  • Less immunogenic than H antigen
• What are the characteristics of the H antigen in Salmonella?

  • Present on flagella
  • Heat and alcohol labile
  • Strongly immunogenic
• Who was Typhoid Mary and what was her role in disease transmission?

  Mary Mallon, known as Typhoid Mary, was a New York cook who caused at least seven outbreaks of typhoid fever.
• How long did Typhoid Mary cause outbreaks of typhoid fever?

  She caused outbreaks over a period of 15 years.
• What are the common sources of infection for S. Typhi?

  Food, vegetables, and water contaminated with human feces infected by S. Typhi.
• What is the infectious dose for S. Typhi infections?

  The infectious dose for S. Typhi infections is low, allowing for person-to-person spread.
• What factors increase susceptibility to S. Typhi infections?

  Age, immunosuppression, underlying diseases, or reduced gastric acidity increase susceptibility.
• Is there an animal reservoir for typhoidal salmonellae?

  No, there is no animal reservoir for typhoidal salmonellae.