5.6 Salmonella etc Flashcards
salmonella characteristics - type of baceria, fermentation, habitat, environment, survivability
- Typical Enterobacterales
- Gram negative rods
- Non-lactose fermenter
- Habitat: Large intestine of carrier animals
– Carry Salmonella without any signs - Can survive and multiply in environment and food
salmonella nomeclature
genus + serotype
ie.
Say salmonella, then skip subspecies (enterica or bongori) and say serotype
eg.
* Genus: Salmonella
* Species: enterica
* Subsp: enterica
* Serovar: Enteritidis, Typhimurium, Choleraesuis, Dublin, etc.
* Full formal scientific name: Salmonella enterica subsp. enterica serovar Enteritidis
* Usual name: Salmonella Enteritidis
how to we serotype salmonella serovars?
- > 2500 (often named) serovars
- Serotyping using slide agglutination for
– O antigen (LPS)
– H antigen (flagella)
Replaced more and more by genotyping (whole genome sequencing)
where can we find salmonella?
- Not “normal flora” (except reptiles)
- Large bowel carrier animal
- Survives fecally - contaminated environment (months)
- Can multiply in environment (20-45oC),
- Can multiply in food
– warm meats, and many others; cross contamination
what species can carry salmonella?
- poultry*
- Reptiles*: iguanas, bearded dragons, turtles
- wild birds
- swine
- cattle
- rodents
- dogs and cats may carry the bacteria
- Humans are carriers of certain types of Salmonella
Why Salmonella is a One Health problem?
Salmonella in food-producing animals present a serious public health concern, because food products of animal origin are a significant source of human infection
Two major types of diseases (Salmonellosis)
- Diarrhea (severe inflammation)
- Septicemia (shock, death, abortion)
Salmonella: virulence factors, how it infects cells and results
Major characteristic: Invasiveness (facultative intracellular)
– LPS: adherence and induction of inflammatory response
– Fimbriae
– Type III secretion system (trigger mechanism)
* Transfer of toxins into host cells during invasion
* Transfer of proteins for intracellular survival
❖ Migration through intestine, survival (temporary) in macrophages and may show systemic dissemination (septicemia, endotoxic shock)
❖ Severe local inflammation (LPS) and cell damage (=>inflammatory enteritis with secretory diarrhea)
Salmonella: pathogenicity
Epithelial M cells uptake salmonella
Inflammatory response=> diarrhea
Blood vessels=> bacteremia=> several tissues
clinical signs of salmonellosis in animals
-acute enteritis: fever, severe diarrhea
-newborn > enteritis > bacteremia
-may lead to colic
type of lesions produced by salmonella and their severity
- Lesions are most severe in the lower ileum, cecum, and colon
- Vary from shortening to complete destruction of villi
- Hemorrhage and fibrin are usually seen
dog and cat signs of salmonellosis
dogs and cats are asymptomatic carriers
What determines whether or not you develop salmonellosis when exposed:
- Dose
- Virulence (serovar, strain)
- Susceptibility (age, immunity, stability of intestinal microbiota, breed?, nutrition?)
- Gastric acidity
- Multiple other host factors
- Environment: Multiplication, hygiene
typically, salmonellosis is a disease of _______ animals mixed from different sources, where __________ and _________.
Typically, salmonellosis is a disease of young animals mixed from different sources, where hygiene is poor and immune status is uncertain
Salmonella: diagnosis
- Culture from feces:
– Liquid enrichment media
– Solid selective/indicator (MacConkey, Brilliant green agar, Hektoen)
– Culture is needed for AST and serotyping - Real-time PCR: can be combined with culture if RT-PCR is positive
❖How to determine the carrier status?
- Repeated isolation on agar
❖How to determine clinical salmonellosis?
- Single isolation from feces, blood, or any tissue + clinical signs
