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

• 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

Who produce the Tribe?

Erwing (1963)

Blackening of the colony or medium

H2S

Triple sugar iron agar (TSI)

Species:

Salmonella

Proteus

Arizona

Citrobacter

Edwardsiella

Lysine Iron Agar (LIA)

Species:

Salmonella

Arizona

Citrobacter

Edwardsiella

Rapid Urease Producers & DEAMINASE producing

Species:

Proteus

Providencia

Morganella

Slow Urease Producers

Species:

Citrobacter

Klebsiella

Enterobacter except. E. gergoviae

Yersinia

Serratia

Lysine decarboxylation (LDC) Positive

Species:

Klebsiella

Escherichia

Edwardsiella

Serratia

Salmonella except S. paratyphi A

Hafnia

Lysine decarboxylation (LDC) Negative

Species:

Proteus

Providencia

Morganella

Citrobacter

Yersinia

Enterobacter except E. aerogenes & E. gergoviae

Shigella

• 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

What is the IMVC of this?

++--

Escherichia coli

EMB Agar- _____

Green metallic sheen

Escherichia coli

PROPERTIES:

• 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

• most common cause of UTIs in human

Uropathogenic Escherichia coli

Escherichia coli

GASTROINTESTINAL PATHOGENS

• 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

• 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

• 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

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:

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:

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

Verotoxin II

Escherichia coli

GASTROINTESTINAL PATHOGENS

• diarrheal syndromes and UTIs- DAEC (Diffusely Adherent E. coli)

• diarrhea by adhering to the surface of the intestinal mucosa- EAEC (Enteroaggregative E. coli)

Extraintestinal Infections

• most common causes of septicemia and meningitis among neonates

Enteroadherent Escherichia coli

Escherichia coli

Other Escherichia Species

• yellow-pigmented

• isolated from cerebrospinal fluid (CSF), wounds, and blood

Escherichia hermannii

Escherichia coli

Other Escherichia Species

• i__solated__ from humans with infected wounds

• Yellow pigmented

Escherichia vulneris

Escherichia coli

Other Escherichia Species

• 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

What is the IMVC of this?

--++

• 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

What is the IMVC of this?

--++

Enterobacter, Cronobacter**, and** Pantoea

• 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:

• isolated predominantly from the respiratory tract

• positive for sucrose, raffinose, and ornithine

• Indole-positive (60%)

S. odorifera biogroup 1

S. odorifera

Two biogroups:

• 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

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

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

• Shigellosis/Bacillary Dysentery

What stage is this?

• Incubation period for 1-7 days

• Fever, abdominal cramping and pain, diarrhea

Early Stage

Shigella

Clinical Infections

• Shigellosis/Bacillary Dysentery

What stage is this?

• Watery diarrhea for 3 days

Diarrheic Stage

Shigella

Clinical Infections

• 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:

• 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:

• occurs when the bacteria spread to the bloodstream

Septicemic form

Yersinia pestis

3 forms:

• 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

• 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