16 – Other Enterobacterales Flashcards
Natural host or habitat (Salmonella)
- Found in gut of a variety of animals
- Canada: Salmonella ID from agricultural animals varies across country
o Most common in humans: S. Enteritidis and Heidelberg
Taxonomy (Salmonella)
- 3 species
- *grouped into serovars/serotypes
Serovars
- Defined by presence of surface antigens
o O-antigens
o H-antigens
O-antigens
- Based on oligosaccharides associated with LPS
H-antigens
- Based on flagellar proteins
- Can have 2 phases (express multiple flagellar proteins)
- Strains may be micro- or di-phasic
Virulence factors
- Salmonella pathogenicity islands (SPI)
- Type 3 secretion systems
- Fimbriae: adherence and colonization
Salmonella pathogenicity islands
- Gene clusters containing virulence genes
Type 3 secretion systems
- Detects host cells
- Act as a needle/syringe to inject effector molecular
- Involved with INVASION
Salmonella Dublin (cattle)
- Cause of severe disease in endemic herds
S. Dublin (cattle): severe disease in endemic herds
- septicemia in calves <1 week old
- acute enteritis in older calves and adults
- abortion in pregnant cows
- chronic enteritis in older cows (inappetence, decreased weight gain)
- terminal dry gangrene: necrosis of feet
S. Dublin (cattle): management
- cleaning calving areas
- rodent control
- vaccination possible
Salmonella Cholersuis (pig)
- maintained by carriers
- during acute disease large numbers shed in feces
Salmonella Cholersuis (pig) cause of
- *sepsis
- Enterocolitis
- Secondary infections following bacteremia (pneumonia, hepatitis)
Salmonella Cholersuis (pig): management
- Reducing stress=reduce shedding by carriers
o Housing density, nutrition, concurrent infectious diseases - Autogenous bacterins (get bacteria from farm and make a vaccine with the exact strain) may be helpful
Salmonella Pullorum (poultry/birds)
- Canada has been free since 1982
- Infects ova and chicks infected prior to hatching
o Environment gets contaminated=facilitate transmission - *young chicks and poults
- Survivors=reservoir for flock
Salmonella Pullorum (poultry): in young chicks and poults
- Inappetence
- Depression
- Diarrhea
- Death
Salmonella Pullorum (poultry): in older birds
- Inappetence
- Arthritis
- Decreased production
- Diarrhea
- Pyrexia (abnormal elevation in body T (fever)
- Increased mortality
Salmonella (poultry): other serotypes found in Canada
- Fecal-oral transmission: direct fecal contact or through litter fluff or water
- Often see highest losses in young <2 weeks old: septicemia
Salmonella Typhi (people)
- Spread by contaminated food and water
- High fever, weakness, stomach pains, death
- Uncommon in western countries (usually travel associated, S. Asia=highest risk region)
o Eat food served hot, and pasteurized, no veggies unless cleaned with clean water - Vaccination possible and important
Yersinia microbiological characteristics
- Most biocontainment level 2 (Yersinia pestis=3)
- Selective media helpful for ID
- Lactose NON-fermenting
- Motile (except Y. pestis)
- Facultative intracellular parasites: survive within macrophages
Y. pestis (humans)
- Black death killed ~60% of Europeans in middle ages
- Spread through Neolithic decline (population decline)
- *outbreaks likely started in larger communities and spread along with trade
Y. pestis: Sylvatic (disease of wild animals) plague (rodents)
- SW US (ex. New Mexico, Arizona, California)
- Cycle between rodents and fleas (prairie dogs=highly susceptible)
o Source for other animals (cat and dogs can get sick if eat rodent or bitten by a flea)
Y. pestis in cats: 3 forms
- Bubonic
- Septicemic
- Pneumonic
Y. pestis in cats: Bubonic
- Lymphadenomegaly, most often submandibular LN following eating infected rodents
- May look like abscess
- High fever
Y. pestis in cats: Septicemic
- May or may not follow bubonic form
- Haematogenous dissemination
- Death 1-2 days
Y. pestis in cats: Pneumonic
- may follow haematogenous dissemination
- may be due to inhaling infectious droplets
- SERIOUS zoonotic risk
- Another reason to beware the hissing cat
Y. pestis in dogs
- Not as common
- Treat with Streptomycin
- Generally start with parenteral antibiotics and switch to oral with improvement
Y. pseudotuberculosis
- Most commonly sporadic disease: abscessation of internal organs
- Found in intestine and can cause enteric infections
- Cause enteric disease in ruminants under stressful conditions (cold, wet weather, poor diet)
- Can see cattle and sheep abortions (1-9% of affected animals)
Y. pseudotuberculosis: cause of ‘pseudotuberculosis’ in guinea=pigs, 2 forms
- Septicemic form
- Nodules in internal organs
*reported to cause septicemia in wide variety of species
Y. enterocolitica (humans)
- enteric pathogen
- associated with eating undercooked pork
- symptoms vary with age
- septicemia can occur
- rarely associated with enteric disease in ruminants
Y. enterocolitica (humans) septicemia can occur and is associated with
- iron overload
- treatment with iron-chelating agents
Y. enterocolitica (human): young children symptoms
- fever
- abdominal pain
- diarrhea which may be bloody
Y. enterocolitica (human): older children/adults symptoms
- fever
- abdominal pain which can mimic appendicitis
Y. ruckeri (fish)
- rainbow trout (widely farmed)=very susceptible
- most often affects fry and fingerling fish
- outbreaks have low, sustained mortality leads to large losses
- behavioural changes (swimming near surface, loss of appetite)
- subcutaneous hemorrhages: post-mortem reveals septicemia
Fry
- juvenile fish which can feed themselves
- no longer dependent on yolk sac
Fingerling
- stage past fry
- juvenile fish which have developed scales and working fins
Sample collection for Salmonella sp.
- Feces
- Blood for serology
- Other affected tissues (abortuses, viscera/bone if septicemic)
Sample collection for Y. pestis
- EXTREME CAUTION (do NOT re-cap needles)
- Lymph nodes, aspirates
- Edematous tissue
- Blood
Sample collection for other Yersinia sp.
- Affected tissues (lymph nodes, blood, feces)
Sample collection for other Enterobacterales
- Affected tissues depending on site of infection
Sample handling
- Do NOT freeze
Salmonella spp. : lab ID
- Culture: selective media
- Serological
Yersinia spp. Lab ID
- Selective media helpful
- Incubation temperature can be helpful
o Y. ruckeri motile at 22 degree C
Lab ID in general
- Colony morphology
- Biochemical tests
- Serology MALDI-TOF
- DNA fingerprinting for strain typing (outbreak ID!)
Zoonotic/interspecies transmission
- Probably under-recognized
- Know what is common in the area you practice
Salmonella zoonotic/interspecies transmission
- Consider all zoonotic
- Foodborne + contact with infected/colonized animals
o Poultry, pigs, horses, owl pellets (petting zoos)
o Feeder mice and reptiles that eat them
Yersinia pestis zoonotic/interspecies transmission
- Exudates
- Respiratory droplets (hissing cat!)
- Fleas
Treatment
- Based on SUSCEPTIBILITY TESTING
- *intrinsic resistance is common and varies WIDELY by genus and species
Resistance is emerging
- Broad spectrum beta-lactamases (ESBLs and carbapenemases)
- Fluroquinolone resistance
- Mobile genetic elements with multiple resistance genes
What drugs are all Enterobacterales intrinsically resistant to?
- Benzylpenicillin
- Glycopeptides
- Lipoglycopeptides
- Fusidic acid
- Macrolides
- Lincosaminds
- Streptogramins
- Rifampicini
- oxazolidinones
