Enteric Gram-Negative Rods (ENTEROBACTERIACEAE)

Review well < 3

* Often referred to as __**enterics**__ or __**coliforms**__
* **Gram-negative bacilli** and **coccobacilli**
* __facultative anaerobes__ or __aerobes__
* ferment a __wide range of carbohydrates__ (**all ferment glucose**)
* possess a complex antigenic structure
* produce a variety of toxins and other virulence factors
* **large, moist, & gray color (sheep blood’s agar or in CAP)**
* Catalase positive

Enterobacteriaceae

Do not produce cytochrome oxidase except for __________

Plesiomonas

reduce nitrate to nitrite except for _______ __and__ ___________

Photorhabdus and Xenorhabdus

motile at body temperature except for ______,__ ______, and__ _______

*Klebsiella, Shigella,* and *Yersinia*

Catalase positive except _________

Shigella dysenteriae type 1

**Classification of Selected Species Within the Family Enterobacteriaceae**

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Who produce the Tribe?

Erwing (1963)

Blackening of the colony or medium

H2S

^^**Triple sugar iron agar (TSI)**^^

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Species:

*Salmonella*

*Proteus*

*Arizona*

*Citrobacter*

*Edwardsiella*

^^**Lysine Iron Agar (LIA)**^^

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Species:

*Salmonella*

*Arizona*

*Citrobacter*

*Edwardsiella*

^^**Rapid Urease Producers & DEAMINASE producing**^^

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Species:

*Proteus*

*Providencia*

*Morganella*

^^**Slow Urease Producers**^^

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Species:

*Citrobacter*

*Klebsiella*

*Enterobacter* except. *E. gergoviae*

*Yersinia*

*Serratia*

^^**Lysine decarboxylation (LDC) Positive**^^

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Species:

*Klebsiella*

*Escherichia*

*Edwardsiella*

*Serratia*

*Salmonella* except *S. paratyphi A*

*Hafnia*

Lysine decarboxylation (LDC) Negative

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Species:

*Proteus*

*Providencia*

*Morganella*

*Citrobacter*

*Yersinia*

*Enterobacter* except *E. aerogenes* & *E. gergoviae*

*Shigella*

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* __**Colon bacillus/ Golden Bacillus**__
* 1885- Escherich
* facultative anaerobic; glucose fermenting, **gram-negative**, **oxidase-negative rods** capable of growth on MacConkey agar
* used as a primary marker of fecal contamination in water quality testing
* **lactose-positive** (__pink__) colony with a surrounding area of precipitated bile salts on MAC agar- __**lactose fermenter**__
* __Most common cause of gram-negative nosocomial infections__

*Escherichia coli*

^^***Escherichia coli***^^

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What is the IMVC of this?

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^^***Escherichia coli***^^

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EMB Agar- _____

Green metallic sheen

^^***Escherichia coli***^^

PROPERTIES:

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* Fermentation of __________??
* Production of indole from tryptophan
* __Glucose fermentation by the mixed acid pathway__: **methyl red positive** and **Voges-Proskauer negative**
* __Does not produce H2S, deoxyribonuclease (DNase), urease, or phenylalanine deaminase__
* **Cannot use citrate as a sole carbon source**

Glucose, Lactose, Trehalose, and Xylose

^^***Escherichia coli***^^

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* most common cause of UTIs in human

Uropathogenic *Escherichia coli*

^^***Escherichia coli***^^

GASTROINTESTINAL PATHOGENS

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* **diarrhea of adults and especially children**
* one of the major __**causes of infant bacterial diarrhea**__
* most common cause of diarrheal disease sometimes referred to as __**TRAVELER’S DIARRHEA**__
* **Produces heat-labile enterotoxin**

Enterotoxigenic *Escherichia coli*

^^***Escherichia coli***^^

GASTROINTESTINAL PATHOGENS

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* known to cause __**INFANTILE DIARRHEA**__
* characterized by low-grade fever, malaise, vomiting, and diarrhea
* **O serogroups**- cause of diarrhea
* **H antigenic**- intestinal infections
* STOOL: watery with mucus but without blood

Enteropathogenic *Escherichia coli*

^^***Escherichia coli***^^

GASTROINTESTINAL PATHOGENS

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* produce **dysentery with direct penetration, invasion, and destruction of the intestinal mucosa**
* __**similar to shigellosis**__
* **nonmotile** and generally **DO NOT FERMENT LACTOSE**
* do not decarboxylate lysine

Enteroinvasive *Escherichia coli*

^^***Escherichia coli***^^

GASTROINTESTINAL PATHOGENS

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==**0157:H7 (1982)**==- **hemorrhagic diarrhea, colitis, and hemolytic uremic syndrome (HUS).**

* __DOES NOT FERMENT SORBITOL__ in 24 hours
* watery diarrhea
* blood diarrhea with abdominal cramps and low-grade fever or an absence of fever

Enterohemorrhagic *Escherichia coli*

^^***Escherichia coli***^^

Enterohemorrhagic *Escherichia coli*

2 TOXINS:

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What is the **identical to the Shiga toxin-produces damage to Vero cells (African green monkey kidney cells)** ?

Verotoxin I

^^***Escherichia coli***^^

Enterohemorrhagic *Escherichia coli*

2 TOXINS:

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What is the **Shiga toxin I & Shiga toxin 2 (Shiga-toxin producing E.coli) (STEC)** ?

Verotoxin II

^^***Escherichia coli***^^

GASTROINTESTINAL PATHOGENS

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* diarrheal syndromes and UTIs- **DAEC (Diffusely Adherent E. coli)**
* diarrhea by adhering to the surface of the intestinal mucosa- **EAEC (Enteroaggregative E. coli)**

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Extraintestinal Infections

* __**most common causes of septicemia and meningitis among neonates**__

Enteroadherent *Escherichia coli*

^^***Escherichia coli***^^

Other Escherichia Species

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* **yellow-pigmented**
* __**isolated**__ **from** __**cerebrospinal fluid (CSF),**__ **wounds, and blood**

*Escherichia hermannii*

^^***Escherichia coli***^^

Other Escherichia Species

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* i__**solated**__ **from** __**humans**__ **with infected wounds**
* Yellow pigmented

*Escherichia vulneris*

^^***Escherichia coli***^^

Other Escherichia Species

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* associated with __**diarrheal disease in children**__

*Escherichia albertii*

* Most grow on __Simmons citrate and in potassium cyanide broth__
* **Non produce H2S**
* A **few hydrolyze urea slowly**
* All are __**methyl red test negative**__ and __**Voges-Proskauer positive**__
* With a few exceptions, no indole is produced from tryptophan
* **Motility is variable**

*Klebsiella* and *Raoultella*

* **most commonly isolated species; large polysaccharide capsule**
* moist, capsulated: mucoid colonies or tend to “string”- Friedlander’s Bacillus
* **very necrotic** and hemorrhagic- __**“Current jelly like sputum”**__

*K. pneumoniae*

**Klebsiella and Raoultella**

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What is the IMVC of this?

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* The __**ONLY INDOLE POSITIVE**__ *Klebsiella* species
* isolated in stool and blood cultures
* **ornithine-positive**
* linked to antibiotic-associated hemorrhagic colitis

*Klebsiella oxytoca*

* Highly associated with the __**presence of plasmid-mediated ESBLs**__
* __isolated__ from __nasal secretions and cerebral abscesses__

*K. pneumoniae subsp. ozaenae*

* has been __**isolated from patients with rhinoscleroma**__
* nasal cavity- __intense swelling & malformation of the entire face and neck__

*K. pneumoniae subsp. rhinoscleromatis*

* __**indole and ornithine decarboxylase-positive**__

*Raoutella (Klebsiella) ornithinolytica*

* have been __**isolated from the urine, respiratory tracts, and blood of humans**__

*Raoutella (Klebsiella) planticola*

* has been __**isolated from primarily sterile sites**__

*K. variicola*

* __**granuloma inguinale**__
* a **sexually transmitted disease**

*Klebsiella granulomatis* (formerly *Calymmatobacterium granulomatis*)

* **Motile**
* __resembles Klebsiella when growing on MAC agar__
* Grow on Simmons citrate medium and potassium cyanide broth
* the **methyl red test is negative**, and the **Voges-Proskauer test is positive**
* usually __**produce ornithine decarboxylase**__
* Slow urease producer except for E. gergoviae

*Enterobacter, Cronobacter*, and *Pantoea*

%%***Enterobacter, Cronobacter*****, and** ***Pantoea***%%

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What is the IMVC of this?

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%%***Enterobacter, Cronobacter*****, and** ***Pantoea***%%

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* lysine decarboxylase is produced by most species but not by _________

*E. gergoviae* or *E. cloacae*

* __**lactose negative**__ but __**ONPG positive**__

*Enterobacter taylorae*

* __Resembles Enterobacter aerogenes__
* **Rapid Urease Produce (RUP)**
* Causes infection of the urinary tract, and blood

*Enterobacter gergoviae*

* __Biochemically similar to Enterobacter cloacae__
* typically **produces a yellow pigment**
* __**pathogen in neonates**__-- meningitis and bacteremia, often **coming from powdered infant formula**

*Cronobacter (Enterobacter) sakazakii*

* lysine-, ornithine-, and arginine-negative or “__**TRIPLE DECARBOXYLASES NEGATIVE.**__”
* __**Indole positive and mannitol**__, raffinose, salicin, sucrose, maltose, and __**xylose negative**__

*Pantoea (Enterobacter) agglomerans*

* __**Opportunistic pathogens**__
* Associated with __outbreaks in health care settings__
* ability to **produce extracellular DNase**
* __**ferment lactose slowly**__ and are **positive** for the o-nitrophenyl-B-D-galactopyranoside **(ONPG) test** except *S. fronticola*

*Serratia*

__3 species__ that **produce a characteristic pink-to-red pigment, prodigiosin, especially when the cultures are incubated at room temperature**

*S. marcescens*

*S. rubidaea*

*S. plymuthica*

* __**dirty, musty odor**__ resembling that of **rotten potatoes**

*S. odorifera*

%%**S. odorifera**%%

Two biogroups:

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* isolated predominantly from the respiratory tract
* __**positive for sucrose, raffinose, and ornithine**__
* Indole-positive (60%)

*S. odorifera* biogroup 1

%%**S. odorifera**%%

Two biogroups:

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* __**negative for sucrose, raffinose, and ornithine**__
* isolated from blood and CSF
* may also be indole-positive (50%)

*S. odorifera* biogroup 2

* Very similar to S. marscesens but differentiated to S. marscesens by its __**ability to ferment arabinose**__

*Serratia liquefaciens*

* **also produces red pigment-** __**prodigiosin**__

*Serratia rubidaea*

%%**Serratia**%%

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What is the IMVC of this?

\- variable ++

* has been **linked to gastroenteritis**
* occasionally __isolated from stool cultures__
* **delayed positive citrate reaction**
* __**Motile and late lactose fermente**__r; __ONPG Positive, CDC positive, ODC positive__

*Hafnia*

* formerly *Enterobacter alvei*
* Resembles *Enterobacter*

**To differentiate**

* Late lactose fermenter
* Citrate Negative

**To differentiate from** ***Serratia***

* DNase negative
* Lipase negative
* Gelatinase negative

*Hafnia alvei*

* tribe Proteeae--ability to deaminate the amino acid phenylalanine; __**non lactose fermenters**__
* normal intestinal microbiota; **opportunistic pathogens**
* “__**CHOCOLATE CAKE**__” or “__**BURNT CHOCOLATE**__” smell

UNIQUE CHARACTERISTICS:

* Rapid Urease Producers (RUP- RXN within 4 hours)
* typical swarming motility (growth in waves or swarms)
* H2S producing in TSI but not in LIA

*Proteus*

***Hafnia***

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What is the IMVC of this?

\- Variable + -

* __**hydrolyze urea**__ and __**produce H2S**__
* ***P. mirabilis*** __does not produce indole from tryptophan__ and is *ornithine-positive*
* ***P. vulgaris*** __produces indole__ and is __ornithine-negative__; f__ermenter sucrose__; __acid/acid reaction in triple sugar iron (TSI) agar__

*Proteus mirabilis* & *Proteus vulgaris*

* **motile but does not swarm**
* __Indole, methyl red, urease, Ornithine decarboxylase and Phenylalanine deaminase__ **POSITIVE**

*Morganella*

* cause of UTI
* cause of neonatal sepsis

*M. morganii*

* __**lactose**__ **negative**, __**Deaminase**__ **Positive**, __**H2S**__ **negative**
* Motile but no swarming
* __ferments mannose & citrate__

*Providencia*

* pathogen of the urinary tract
* cause **occasional outbreaks in health care settings**
* __**diarrheal disease among travelers**__

*P. rettgeri*

* __**outbreaks in burn units**__
* **isolated** from __urine cultures__

*P. stuartii*

most commonly __**found in the feces of children with diarrhea**__

*P. alcalifaciens*

**rarely isolated**

*P. rustigianii*

yet to be __**isolated from any clinical specimens**__

*P. heimbachae*

* **negative** for __urea__
* **positive** for __lysine decarboxylase, H2S,__ and __indole__
* do **not grow on Simmons citrate**

*Edwardsiella*

* __**Opportunist**__
* causing bacteremia and wound infections

*E. tarda*

__**Isolated from snakes, birds,**__ **and** __**water**__

*E. hoshinae*

Causes __**enteric septicemia in fish**__

*E. ictaluri*

* **hydrolyze urea slowly** and __**ferment lactose**__
* producing colonies on MAC agar that resemble those of E. coli
* grown on **Simmons citrate medium**
* __**positive methyl red test**__

*Citrobacter*

* **produce H2S** and **some strains (50%)** __**fail to ferment lactose**__
* colony morphology on primary selective media can be mistake for Salmonella when isolated from stool cultures
* **hydrolyze urea**, but all __**fail to decarboxylase lysine**__

*C. freundii*

* cause of **nursery** __**outbreaks**__ **of neonatal meningitis** and **brain abscesses**

*C. koseri*

* __**rare**__ **human pathogen**
* associated with __community-acquired infections__ including a septicemia in patient with cervical cancer

*C. braakii*

* **formerly** in the __family Vibrionaceae__
* __**oxidase-positive, glucose-fermenting, facultatively anaerobic, gram-negative bacilli**__
* does __not have the ability to produce gas from glucose__
* susceptible to agent O/129
* motile by monotrichous or two to five lophotrichous flagella

*Plesiomonas*

* **more common** __**watery**__ **or** __**secretory diarrhea**__
* A subacute or chronic disease that lasts from 14 days to 2 to 3 months
* a **more invasive, dysenteric from that resembles colitis**

*P. shigelloides*

* __**gram-negative**__, facultatively anaerobic bacilli that morphologically resemble other enteric bacteria
* Selective and differential media; clear, colorless, non-lactose-fermenting colonies
* **colonies with black centers** are seen if the media (e.g., HE or XLD) contain indicators for **H2S production**
* __**do not ferment lactose**__
* **negative for indole, the Voges-Proskauer test, phenylalanine deaminase, and urea**
* do __not__ grow in medium containing potassium cyanide
* **Most produce H2S** except __*Salmonella paratyphi A*__

*Salmonella*

* **nonmotile**
* do __not produce gas__ from glucose except *S. flexneri*
* do __not hydrolyze H2S__
* do __not decarboxylate lysine__
* do __not use acetate or mucate as a source of carbon__
* named after **KIYOSHI SHIGA**

*Shigella*

* ability to decarboxylate ornithine
* __**slowly ferments lactose**__
* **ONPG-positive**

*S. sonnei*

enteric disease (__**BACILLARY DYSENTERY**__)

*Shigella dysenteriae*

**Shigella**

Clinical Infections

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* Shigellosis/Bacillary Dysentery

__What stage is this?__

* Incubation period for 1-7 days
* **Fever, abdominal cramping and pain, diarrhea**

Early Stage

**Shigella**

Clinical Infections

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* Shigellosis/Bacillary Dysentery

__What stage is this?__

* **Watery diarrhea for 3 days**

Diarrheic Stage

**Shigella**

Clinical Infections

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* Shigellosis/Bacillary Dysentery

__What phase is this?__

* __frequent__ **stools with blood, pus, and mucus**
* __Bacteria__ had **invaded the lining of th GIT**

Dysenteric Phase

* __short__, **pleomorphic Gram-negative rods** that often exhibit bipolar staining
* __**catalase positive**__
* **microaerophilic** or **facultatively anaerobic**

*Yersinia*

* cause of __**plague, black death**__
* typically causing a mild diarrheal disease, following ingestion of contaminated food and/ or water

*Y. pestis*

* __**zoonotic food-borne pathogens**__
* typically causing a mild diarrheal disease, following ingestion of contaminated food and/ or water

*Y. enterocolitica* and *Y. pseudotuberculosis*

* causative agent of the ancient disease plague
* a **gram-negative, short, plump bacillus**
* Bipolar staining- “__**SAFETY-PIN appearance**__”- Methylene Blue or Wayson stain
* May be isolated on routine culture medium
* grows at 37 C
* preferential growth temperature: 25 to 30 C

*Yersinia pestis*

@@***Yersinia pestis***@@

3 forms:

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* **most common**
* results from the __**bite of an infected flea**__
* symptoms appear 2 to 5 days after infection
* high fever with painful regional lymph buboes (swollen lymph nodes) begin to appear

Bubonic form

@@***Yersinia pestis***@@

3 forms:

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* occurs when the bacteria spread to the bloodstream

Septicemic form

@@***Yersinia pestis***@@

3 forms:

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* occurs **secondary to bubonic plague or the septicemic form**
* can be a **primary infection if the bacteria are** __**inhaled**__

Pneumonic plague

* __**gram-negative coccobacilli**__ with __**bipolar staining**__
* Grows on **SBA and MAC**
* optimal growth temperature of 25 to 30 C
* found in a wide variety of __animals, including domestic swine, cats, and dogs__
* produce a __**heat-stable enterotoxin**__
* ability to __**survive in cold temperatures**__

*Yersinia enterocolitica*

* selective medium to **detect the presence of** ***Y. enterocolitica***
* cefsulodin, irgasan, novobiocin, bile salts, and crystal violet as inhibitory agents

Cefsulodin-irgasan-novobiocin (CIN) agar

* __**modification of CIN agar**__
* Added __Mannitol__
* Fermentation of mannitol: red at the center of the colony and the bile to precipitate
* Nonfermentation of mannitol produces a colorless, translucent colony

Yersinia-selective agar (YSA) base

* Pathogen **primarily of rodents, particularly guinea pigs**
* characterized by **caseous swelling** called ***PSEUDOTUBERCULOSIS***
* appears as a __**typical-looking plague bacillus**__
* motility at 18 C to 22 C
* **production of urease**, and ability to __**ferment rhamnose**__
* **often fatal in animals**

*Yersinia pseudotuberculosis*

Other Genera of the Family Enterobacteriaceae

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* __**Budivicia aquatica**__
* **usually found in water**; however, they occasionally occur in clinical specimens

*Budivicia*

* *B. agrestis* and *B. noackiae*- **isolated from human specimens**
* similar to both Citro bacter and Kluyvera species, but DNA hybridization distinctly differentiates Buttiauxella from both genera

*Buttiauxella*

* five species: *C. davisae, C. lapagei, C. neteri*, and *Cedecea* __species types 3 and 5__
* **Most** have been **recovered from sputum, blood, and wounds**
* __***C. davisae***__ is the **most commonly isolated species**

*Cedecea*

* *Ewingella americana* is the **only species**
* come from **human blood cultures or respiratory specimens** and **exhibit resistance to multiple antimicrobial agents**

*Ewingella*

* found in respiratory, urine, and blood cultures
* __Most strains are nonpigmented__, but __occasional isolates may produce a reddish-blue or violet pigment__
* resemble E. coli colonies growing on MAC agar
* __***K. ascorbata***__ **does not ferment glucose** at 5 C
* __***K. cryocrescens***__ **ferments glucose**

*Kluyvera*

* ***L. adecarboxylata***- have a __**yellow pigment but only on initial isolation**__
* Has **similar IMViC reactions to** ***E. coli***
* __negative for lysine__ and __ornithine decarboxylase__ and __arginine dihydrolase__

*Leclercia*