Untitled Quiz

Study Notes

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.

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.

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.

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 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 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

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.

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