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
Salmonella: control and therapy
Salmonella: control and therapy Immunization? (live attenuated oral vaccines=> cell-mediated immunity)
Competitive exclusion (probiotics); Hygiene
Antimicrobial therapy
– Usually, self-limiting infections
– For severe disease and septicemia only
- Treatment of intestinal salmonellosis or asymptomatic infection is controversial because of risk of creating carriers or antibiotic resistance
famous disease caused by Yersinia pestis
Bubonic plague/black death
type of disease caused by Yersinia pestis
bubonic - most common. Flea/rodent to human transmission
septicemic - secondary to bubonic, or enters through break in the skin
pneumonic - most deadly. Human to human via air droplets
yersinia pestis ecology in the USA
-occurs naturally in the western US, especially in the semi arid grasslands and scrub woodlands of the southwestern states of Arizona, Colorado, New Mexico, and Utah
-yersinia pestis is transmitted by fleas and cycles naturally among wild rodents, including rock squirrels, ground squirrels, prairie dogs, and wood rats
-occasionally, infections among rodents increase dramatically, causing an outbreak. During outbreaks, many rodents die, causing fleas to seek other sources of blood
-humans and domestic animals that are bitten by fleas from dead animals are at risk for contracting plague, especially diring an epizootic. cats usually become very ill from plague and can infect humans when they cough infectious droplets in the air. dogs are less likely to be ill, but if they can still bring plague-infected fleas into the home. People can also be exposed by handling dead animals.
yersinia pestis signs in cats
-Submandibular lymphadenopathy, most likely due to eating a plague- infected rodent or rabbit, with inoculation of the plague bacteria into the oral mucosa
-Fatal plague case in a cat shows a submandibular lymphadenopathy with a draining abscess. The plague bacteria in this abscess are potentially infectious to other animals and people
Proteus vulgaris, Proteus mirabilis are entobacterales that cause what?
(opportunist: UTI, otitis, others)
proteus mirabilis motility type
swarming
Klebsiella pneumoniae type of pathogen, effects in various animal species
– Opportunist, pneumonia in horses, mastitis in cattle, UTI in companion animals, hospital-acquired infections in humans
ESKAPE group
Enterobacter cloacae, Enterobacter aerogenes type of pathogen, character
– Opportunists, resistant hospital-acquired infections in humans and animals
– Members of the ESKAPE group of multi-resistant bacteria, emerging hospital problems
