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Flashcards in enterobacterales bacteria Deck (26)
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1
Q

What does it mean if you get gram - cocci on a gram stain?

A

Either:
1. You messed up your Gram stain!
2. There was some other change to the cell wall!
3. The organism you Gram stained isn’t a pathogen

2
Q

enterobacterales shared features

A

Gram negative rods
Facultatively anaerobic
Oxidase negative
Most are motile
Growth on blood agar - similar colonies
* Some, not all, are hemolytic except Proteus (swarms)

Grow on MacConkey’s agar
* Tolerate bile salts
* Lactose fermentation is variable
* Helps differentiate in family

3
Q

5 main genera in enterobacterales

A

E. coli
salmonella
yersinia
klebsiella pneumonia
proteus

4
Q

2 main groups of enterobacterales

A

lactose fermentation positive
* Escherichia
* Klebsiella

lactose fermentation negative
* Proteus
* Salmonella
* Yersinia

5
Q

which genera are strong vs intermediate pathogens in enterobacterales

A

strong: E. coli, salmonella, yersinia
intermediate: klebsiella pneumoniae, proteus

6
Q

Where does E. coli come from?

A

NORMAL FLORA of most vertebrates
* Lower ileum
* Large intestine
* Colonizes neonatal GIT within hours of birth

Survives well in the environment
Makes “coliform” counts valuable indices of fecal contamination

7
Q

How is E. coli transmitted?

A

Feco-oral (most common route)
Inhalation
Direct inoculation
Ascending infections
* Cystitis
* Pyometra
* Transient in urogenital tract

8
Q

virulence of E. coli

A

not all strains are virulent, some are harmless
very diverse bacteria

9
Q

how does E. coli cause dz?

A

Not all E. coli strains are virulent.
Strains with Virulence Factors act by:
* Attachment: pili, adhesions
* Avoidance of phagocytosis: capsule
* Cellular effects (physiological or toxicity): hemolysin, CNF
* Systemic Effects: endotoxin

But the contribution of the virulence factor depends on the site of infection
Some strains may be virulent at one site but avirulent at another (e.g., Non-Enteric versus Enteric)

10
Q

What diseases does E.coli cause?

A

E. coli has been incriminated in infectious disease involving virtually every tissue and organ system – because some strains of E.coli are very good opportunistic pathogens
Common ones:
* sepsis
* bladder infections
* pyometra
* mastitis

11
Q

How to treat E. coli and other enterobacterales?

A

There are multiple drug resistant strains of Enterobacterales
* Particularly E. coli, and Klebsiella and Salmonella
* Drug resistance plasmids are readily transferred among members of the Enterobacterales

MUST DO SUSEPTIBILITY TESTING
Enterobacterales are some of the MOST antibiotic resistant bacteria currently in existence

Ancillary therapies:
* Critically important
* Surgery/drainage/debridement
* Fluid therapy
* Anti-endotoxin therapies

12
Q

Salmonella species/strains

A

2 species:
* salmonella enterica
* salmonella bongeria

over 2400 serotypes of these species

13
Q

Where does salmonella come from?

A
  • Parasites of the Gastro-intestinal Tract (GIT)
  • Salmonella is NOT normal flora

Can be present in CARRIER ANIMALS
* Present in GIT of carrier animals which can include wide variety of mammals, birds, reptiles and insects!!!
* This is not the same as “normal flora”!

Survive LONG time in the environment
* Major source of infection (contaminated feedstuffs, water, etc)

14
Q

how is salmonella transmitted?

A

Feco-oral transmission
* Variety of animal species are carriers (Reptiles, Cattle, Horses, Others)

Recrudescence of infection in carrier animals

15
Q

How does salmonella cause dz?

A

Avoidance of killing by phagocytes
* Facultative Intracellular Parasites
* Live inside of macrophages

Systemic carrier states
* Not just in the intestine
* Live in macrophages
* In mediastinal lymph nodes and liver

16
Q

What diseases does salmonella cause?

A

Enteritis
* Horses, Cattle
* Less common in carnivores

Septicemia with Localization
* SEPTICEMIC, with localization in lungs, joints, kidneys, heart, spleen, etc
* Mostly occurs in YOUNG animals
* Ability to invade intestines, survive inside macrophages

Carrier State
* Salmonella can also localise in phagocytes (macrophages)
* Facultative Intracellular Parasites
* Inside macrophages they are transported to local lymph nodes (e.g., MLN), liver, spleen & gallbladder and remain there for weeks to years = CARRIER STATE
* Salmonella are shed intermittently & inapparently in their feces
* Infections may recrudesce & clinical disease (diarrhea) redevelops

17
Q

Where does yersinia pestis come from?

A

Wild rodents are the reservoir
Rodents (mice, rats) prairie dogs, squirrels
Flea-rodent-flea life cycle

18
Q

How does yersinia cause dz?

A

Avoidance of killing by phagocytes
Facultative Intracellular Parasites (live in macrophages)
like salmonella

19
Q

What diseases does yersinia pestis cause?

A

Non-enteric Yersinia

Plague (Black Death) in humans and cats
* Rarely in other species e.g., dogs, ungulates
* Occasionally see disease in reservoir spp.
* Bubonic form (lymph nodes)
* Pneumonic form (lungs)
* Septicemic form (systemic)

Plague clinical signs:
* Severe depression
* Fever
* Enlarged peripheral lymph nodes

19
Q

What diseases does yersinia pestis cause?

A

Non-enteric Yersinia

Plague (Black Death) in humans and cats
* Rarely in other species e.g., dogs, ungulates
* Occasionally see disease in reservoir spp.
* Bubonic form (lymph nodes)
* Pneumonic form (lungs)
* Septicemic form (systemic)

Plague clinical signs:
* Severe depression
* Fever
* Enlarged peripheral lymph nodes

20
Q

How to diagnose Yersinia pestis infection?

A

With caution!!!
Send aspirates of pus, blood, LNs to specialized labs
* Notify public health authorities
* Bipolar staining
* PCR & culture
* Be careful if handling these secretions!

21
Q

klebsiella

A

enterobacterales
most common: K. pneumoniae
in normal fecal flora, saprophyte, likes sawdust

22
Q

what diseases does klebsiella cause?

A

Pneumonia (usually secondary to viruses/other bacteria)
Cystitis (dogs)
Mastitis (cattle)
Endometritis (horses)
Navel ill; septicemia with localisation (all species)
Nosocomial infections (due to antimicrobial resistance)
can be involved in superinfections

similar to e. coli

23
Q

proteus

A

enterobacterales
in normal fecal flora, saprophytes, likes moist environments
swarm blood agar plates

24
Q

What diseases does proteus cause?

A

Relatively low grade pathogen (Opportunistic infections!)
Cystitis (dogs, horses)
Otitis externa (dogs & cats)
Prostatitis (dogs)
Wound infections
* Careful – commonly a contaminant if collect a poor/inappropriate sample

25
Q

diagnosing klebsiella and proteus infections

A

Isolation from sterile sites using aseptic techniques
Don’t routinely cause disease in sites that have normal flora
Apply the four point rule > if significant > we ASSUME that they are causing the infection
BUT take care with Proteus and sample collection!
Repeated cultures may help