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Questions and Answers
What is a critical role of the unique metabolic aspect of Salmonella in its detection?
What is a critical role of the unique metabolic aspect of Salmonella in its detection?
- Utilization of glucose as a primary energy source
- Production of lactic acid under anaerobic conditions
- Ability to use tetrathionate as an electron acceptor (correct)
- Ability to ferment lactose for growth
Which of the following Salmonella serovars primarily poses a public health concern?
Which of the following Salmonella serovars primarily poses a public health concern?
- Salmonella enterica serovar Typhimurium (correct)
- Salmonella enterica serovar indica
- Salmonella bongori
- Salmonella enterica serovar diarizonae
How does the pathogenesis of Salmonella differ from that of other enteric pathogens?
How does the pathogenesis of Salmonella differ from that of other enteric pathogens?
- Salmonella exclusively affects birds and reptiles.
- Other enteric pathogens do not cause any gastroenteritis symptoms.
- Salmonella employs unique mechanisms not seen in other pathogens. (correct)
- Salmonella's mechanism of action depends only on its antibiotic resistance.
What is the primary disease syndrome associated with Salmonella infection?
What is the primary disease syndrome associated with Salmonella infection?
Which method is NOT typically used to detect Salmonella infections?
Which method is NOT typically used to detect Salmonella infections?
Flashcards
Salmonella Species
Salmonella Species
Two main species: Salmonella enterica and Salmonella bongori. The primary focus is on serovars of Salmonella enterica.
Salmonella Serovars Identification
Salmonella Serovars Identification
Traditionally identified by O and H antigens (serotyping). Also identifiable via enrichment culture, chromogenic media, phage analysis, antibiotic sensitivity, and genome structure analysis (e.g., pulsed-field gel electrophoresis).
Salmonella Infection in Animals
Salmonella Infection in Animals
Salmonella strains are found in the intestines of wide range of animals (fish, reptiles, birds, mammals). Many mammals shed Salmonella without showing symptoms, especially birds and reptils.
Salmonella Enteritis Symptoms
Salmonella Enteritis Symptoms
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Salmonella Detection Methods
Salmonella Detection Methods
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Study Notes
Salmonella: Learning Outcomes
- Salmonella are detected, classified, and traced.
- The role of host- and serovar-specific factors in infection outcomes is understood.
- Knowledge of zoonotic Salmonella serovars and their public health significance is important.
- The mechanisms of Salmonella pathogenesis differ from other enteric pathogens.
Salmonella Nomenclature
- Two species: S. enterica and S. bongori.
- Subspecies of S. enterica (e.g., enterica, diarizonae, salamae) are of primary interest.
- Key serovars (e.g., Typhimurium, Dublin, Enteritidis).
- Serovars are identified by O and H antigens; written in capital letters without italics.
Salmonella Detection
- Enrichment culture based on metabolism (e.g., use of tetrathionate) to isolate Salmonella from samples.
- Chromogenic media for detection of Salmonella-specific activities (e.g., H2S production).
- Analysis methods: serotyping, phage and antibiotic sensitivity, genome structure (e.g., pulsed-field gel electrophoresis), multi-locus sequencing typing.
- These methods aid in identifying sources and monitoring trends.
Salmonella Infections
- Strains found in various animals (fish, reptiles, birds, mammals).
- In many mammals, Salmonella are not commensals but may be shed asymptomatically after infection.
- Asymptomatic shedding in birds and reptiles poses health risk to owners.
- Main disease syndromes:
- Enteritis (watery diarrhea, foul smell, sometimes bloody).
- Septicemia (fever, loss of appetite, depression, reduced milk production, sometimes fatal).
- Abortion (low probability, can affect pregnant animals).
Host-Adapted vs. Non-Adapted Salmonella
- Host-adapted strains cause more serious systemic disease, often restricted to the specific host.
- Non-adapted (ubiquitous) strains cause gastroenteritis and are more likely to be zoonotic.
- Examples of host-adapted strains in different animal groups (cattle, sheep, pigs, poultry, humans).
- S. Typhimurium and S. Enteritidis common serovars for zoonotic transmission in human cases.
- Non-adapted strains are often associated with gastro-enteritis.
Salmonella Pathogenesis
- Salmonella invades epithelial cells in the small intestine.
- Unlike many E. coli strains, Salmonella actively enters the host cells.
- Two type III secretion systems (T3SS) play roles in invasion.
- SPI-1 is critical for cellular invasion, while SPI-2 contributes to survival and multiplication inside the cell.
- Prevents fusion with lysosomes, enabling bacterial replication.
- Important effector proteins (e.g., SipA, SopB, SopE) hijack cellular pathways.
- Disrupts tight junctions and barriers, leading to diarrhea.
- Host-adapted vs. non-adapted strains also exhibit differences in their ability to elicit inflammatory responses
Salmonella as Live Oral Vaccines
- Attenuated Salmonella strains are used as live oral vaccines, often combined with foreign antigens for broader protection against infectious agents.
- Attenuation methods (limiting amino acid biosynthesis pathways) limit bacterial growth and improve safety.
Salmonella Infections and their Impact in Various Host Animals
- Hosts: cattle, sheep, pigs and poultry are common
- Main Disease Syndromes associated with infections in different animals are described
- Zoonotic diseases caused by Salmonella, which also impact human health are listed
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