Enterobacterales

Escherichia coli, Shigella, Edwardsiella, Salmonella, Citrobacter, Klebsiella, Enterobacter, Cronobacter sakazakii, Proteus, Providencia, Morganella, Yersinia, Serratia

What are the general characteristics of Enterobacterales?

GNR

Gut bugs, environmental bugs

Facultative anaerobes

GLUC+ / OX- / NIT+

What is the exception to Enterobacterales?

Plesiomonas is OX+

What are the serological antigen characteristics?

O: cell well (somatic) - stable

K: capsular (envelope)

H: flagellar

Vi: capsular (S. typhi)

What kind of diseases can E. coli cause?

Diarrhea/gastroenteritis "Traveler's diarrhea"

Hemorrhagic colitis / HUS

UTIs

What kind of strain is E. coli 0157H7?

Enterohemorrhagic strain (EHEC)

What kind of disease does E. coli 0157H7 cause?

Shiga like toxin (STEC)

Hemolytic uremic syndrome (HUS)

What characteristic should we be worried about for shiga toxin producing E. coli (STEC)?

Antibiotics in risk of developing HUS, so needs to be ruled out before antibiotics

What are the kinds of other virulent E. coli?

Enterotoxigenic (ETEC)

Enteroinvasive (EIEC)

Enteropathogenic (EPEC)

Enteroaggregative (EAEC)

What does Shigella cause?

Shigellosis aka bacilliary dysentery (proliferation in small intestine and dmg the large intestine)

Is shigella normal flora?

Not normal flora

HIGHLY pathogenic <50 bacteria to cause disease, not affected by stomach acid

What Shigella is most severe?

S. dysenteriae (invades bloodstream and has shiga toxin)

What are the serogroups of Shigella?

DysenteriAe

FlexneriB

BoydiiC

SonneiD

What are the biochemicals of Shigella dysenteriae?

MAN- / ONPG-

What are the biochemicals of Shigella flexneri?

MAN+ / ONPG-

What are the biochemicals of Shigella boydii?

MAN+ / ONPG-

What are the biochemicals of Shigella sonnei?

MAN+ / ONPG+

How are Shigella groups determined?

Via bacterial agglutination — if untypeable, boil to inactive capsule that can mask O ag

What are the 2 species of Salmonella?

S. enterica (majority of illness)
S. bongori

What are the reservoirs for Salmonella?

Reptiles, chicken

S. typhi is only found in humans (human feces → human oral)

What is the incubation period for Salmonella?

S. enterica: 12-36 hrs

S. typhi: 2 wks

Why is S. typhi so dangerous? How does it proliferate?

Infected can be carriers → "Typhoid Mary"

Bacterium remain in gallbladder

What are the main biochemicals of Shigella and Salmonella?

Shigella: LAC/H₂S-

Salmonella: LAC-/H₂S+

What are the characteristics of Edwardsiella?

Source: enviro, snakes, turtles

Resembles Salmonella

H₂S+/ONPG- (LAC-)

**IND+/CIT-

(spells HOLIC)

What's the difference between K. pneumoniae and K. oxytoca?

K. pneumo is IND-

K. oxytoca is IND+

What are the characteristics of Klebsiella?

Nosocomial infections (diabetics, alcoholics higher risk)

Highly mucoid

Non-motile/IND-

(K. oxytoca IND+)

What is the causative agent of STD (granuloma inguinale)? What are its characteristics?

K. granulomatis

Does not gram stain/grow in lab media

In Wright/Giemsa, may see Donovan bodies

What are the 3 kinds of Enterobacter? What are their characteristics?

E. cloacae (most common)

E. sakazakii (Cronobacter sakazakii): food poisoning, infant formula, creates a YELLOW pigment

E. taylorae: only isolate LAC-

What are the characteristics of Serratia?

Opportunistic pathogen (NICU outbreaks)

S. marcescens most common

Some strains pink/red pigment that darken at RT

Delayed lactose fermenter but ONPG+

What is the characteristics of Proteus?

Swarmers

H2S+

ONPG-/Lactose-

P. vulgaris IND+ & P. mirabilis IND-

PDA+/Urease+/TDA+

Musky smell

(HOLI+PUT)

What are the characteristics of Providencia?

PDA+/IND+/CIT+/TDA+
VP-

(PICTV)

Providencia rettgeri

What are the characteristics of Morganella?

PDA+/IND+/TDA+/CIT-
Usually H₂S-
VP-

(PITCHV)

(ignore TSI tube color)

Moranella morganii

What are the characteristics of Citrobacter?

H₂S+

IND-

(C. koseri IND+)

Citrobacter freundii

What are the 3 species of Yersinia and what do they cause?

Y. pestis - plague

Y. enterocolitica - enterocolitis

Y. pseudotuberculosis - lymphadenitis

What are the characteristics for Yersinia?

Small GN CB

Motility at 25C

Non-motile at 37C

(Y. pestis always non-motile)

What is the pathology of Y. enterocolitica?

Enterocolitis

What kind of media is used to culture Y. enterolitica?

CIN media (efsulodin-irgasan-novobiocin)

Y. enterolitica: clear with pin centers "bulls-eye"

Aeromonas: also, pink center

What kind of plagues does Y. pestis cause?

Bubonic plague (rodent → flea → you)

Pneumonic plague (black death)

Septic plague: lymph/lungs → blood

What are the characteristics of Y. pestis?

Pinpoint colonies on BAP >24hrs
GNR
CAT+/UREA-/OX-/Nonmotile

(CUON)

What do the colors mean in KIA/TSI?

Acidic: yellow → fermentation + (A)
Alk: red → fermentation = (K)
H₂S: black for sulfur prod
Gas: bubbles/agar breakage/unfilled

What is the purpose of ONPG?

Detects B-galactosidase (enzyme that cleaves lactose into glucose and galactose)

Yellow = positive

What is the purpose of indole test?

Test for tryptophanase

Indole + aldehydes → colored complex

Common to diff E. coli (IND+)

What does MR test?

Whether bacteria can create acidic environment
Red = positive (capable of mixed acid fermentation)

What's the purpose of VP?

Detects metabolism of glucose → acetoin

Red = positive

What is the purpose of citrate?

Test if bacteria can use citrate as carbon source
Growth + blue = positive

What is the purpose of PDA?

Test if bacteria can deaminate phenylalanine → phenylpyruvic acid

Detects with ferric chloride

Green = positive

What is the purpose of urease?

Detects urease enzyme

Hydrolyzes urea → ammonia (Alkaline)

Red/pink = positive

What is the purpose of decarboxylase-dihydrolase?

Test bacteria ability to degrade

Lysin → Cadaverine

Ornithine → Putrescine

Arginine → Putrescine

uses Moeller's decarboxylase

Purple = positive (alkaline)

What is the purpose of LIA?

Used to screen for Salmonella

Test if bacteria can: Decarboxylate lysine or deaminate lysine