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Gram Negative Rods
Enteric: Enterobacteriaceae
82
Microbiology
Graduate
03/30/2011

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Cards

Term
Enterobacteriaceae general characteristics/epidemiology
Definition

gram-

oxidase-

non-motile OR motile w/ peritrichous flagella

non-fastidious

all except 1 ferment glucose (some ferment lactose; some non-fermenters can be pathogenic? not a good rule)

normal animal/human intestinal flora

>70% UTIs

significant cause: food poisoning

Term
common genera of the Enterobacteriaceae family (6):
Definition

1. Escherichia coli

2. Shigella

3. Proteus

4. Salmonella

5. Yersinia

6. Klebsiella

*all GNB

Term
predominant GNB of colonic flora
Definition
E. coli
Term
enterobacteriaceae: lactose fermenters
Definition

Escherichia

Klebsiella

Term
Enterobacteriaceae: Lactose non-fermenters
Definition

Proteus

Salmonella

Shigella

Yersinia

Term
MacConkey agar
Definition

pink colonies => lactose fermenters

used when testing for enterobacteriaceae

Term
GNB have LPS as an integral part of the cell wall & is released after cell death; typical LPS includes:
Definition

1. lipid A: w/in mem; toxic activity

2. conserved core polysaccharide: common antigen

3. variable O-polysaccharide: serologic diversity

Term
virulence of enterobacteriaceae (4)
Definition

1. capsule (antiphag/poor antigen; inhib opson/complement activation)

2. antigenic variation: K&H antigens (alternatively expressed or not at all; evade host defense)

3. nutrient trap: Fe chelators (siderophores  enterobactin, aerobactin)

4. ~20 bact proteins => "syring" (deliver virulence factors to host) *Yersinia, Salmonella, EPEC, Pseudomonas*

Term
the strains causing extra-intestinal & intestinal infections are different; what part of the host's immune system are important?
Definition

humoral & innate immunity

incr susceptibility w/ dysfunction/deficiencies of these parts of the immune system

Term
most common cause of septic shock?
Definition
GNBs
Term
name the organism w/ major sites of infection: CNS, LRT, bloodstream, GIT, & UTI
Definition
E. coli
Term
name the organism w/ major sites of infection: LRT, bloodstream, UTI
Definition
Klebsiella
Term
name the organism w/ the major sites of infection: LRT & bloodstream
Definition
enterobacter
Term
name the organism w/ the major sites of infection: GIT
Definition

Salmonella

Shigella

Yersinia

Term
name the organism w/ the major sites of infection: UTI
Definition

Proteus

Morganella

Term
[image]
Definition

motility test semi-soft medium inoculated w/ straight neele

motile bacteria swim away from the line of inoculation to find nutrients/cause turbidity 

=> + is cloudy/line of inoculation not visible

and - is clear/line of inoculation visible (bacteria are growing along)

*used to test enterobacteriaceae

Term
[image]
Definition

-citrate utilization test (citrate is sole carbon source & ammonium salts sole N source)

-organisms that metabolizae citrate use ammonium salts --> release ammonia/incr pH

-bromothymol blue: green at neutral & deep blue above pH 7.6

*all salmonella (except S. typhi are +)

Term
urease test
Definition

this tests for the bacteria that produce urease (these organisms will break the C-N bond of amides => co2, nh3, & h20 => basic solution)

results: + is pink

examples: E. coli- & Proteus+

Term
indole test
Definition

+ result: bacterial tryptophanase (converts tryptophan --> indole); adding Kovac's reagent leads to formation of red ring (pink color)

*E. coli+; P. vulgaris+; S. typhimurium-

Term
SIM test
Definition

combined test to determine production of: indole & H2S AND motility

inoculate organism in tube: organism w/ cysteine desulfurase (cysteine --> pyruvate + NH3 + H2S); Fe in medium rxs w/ H2S => black precip; motility (growth away from stab) is difficult to see w/ the H2S rxns

Ex: 1) E. coli does not produce H2S (no black color) & DOES prod indole (red ring)

2) Salmonells prod H2S (black color) & does NOT prod indole (no red ring)

3) Proteus vulgaris produces both H2S & indole (black color and red ring)

Term

triple-sugar-iron (TSI) test

[medium contains: 1% sucrose, 1% lactose, 0.1% glucose, and Fe]

Definition

no fermentation (obligate aerobe): slant & butt remain red

only glucose is fermented: acid in butt turns it yellow (insuff to affect slant)

sucrose or lactose ferments: butt & slant both yellow

gas forms during fermentation: agar cracks (displaced upwards)

H2S is produced: black in butt

Term
[image]
Definition

triple sugar iron (TSI) test results:

red-no fermentation

yellow-acid prod from fermentation

YG-gas produced

Term
testing for enterobacteriaceae on macconkey agar
Definition

selective medium

bile salts & crystal violet inhib GPB growth

lactose (fermentable sugar) allows differentiation

neutral dye: red @ pH<6.8 & colorless @ pH>6.8

Term
Enterobacteriaceae: lactose-fermenters
Definition

Escherichia coli

Klebsiella pneumoniae

(considered to be usually non-pathogenic)

Term
Enterobacteriaceae: lactose non-fermenters
Definition

Salmonella

Shigella

Proteus

(considered to be usually pathogenic)

Term
extra-gastrointestinal infections caused by Escherichia coli are usually:
Definition
endogenous and different strains than those causing intestinal infections
Term
How is a gastroenteritis infection due to Escherichia coli from the environment usually transferred?
Definition
fecal-oral route
Term
virulence factors of Escherichia coli (5)
Definition

1. surface antigens (confer variability)

2. adhesins (indicates cell identity: p fimbriae/pili~UTI; colonization factors~GI; aggregative adherence fimbriae~UTI)

3. capsule

4. endotoxin: LPS

5. Exotoxins: ETEC (enterotoxigenic)~heat stable & heat labile; EHEC (enterohemorrhagic)~shiga-like toxins

Term
most common extra-intestinal Escherichia coli infection & presentation
Definition

UTI

-dysuria, frequency, suprapubic pain

-fever and/or back px => progression to pyelonephritis

Term
name the 2 most common bacterial causes of meningitis in neonates
Definition

1. Streptococcus agalactiae

2. Escherichia coli

Term
what characteristics of E. coli promote UTI?
Definition

serotypes w/ P pili

attaches bacteria to cell linings of the bladder and prevents them being "flushed" out with the urine

Term
2nd most common site of extra-intestinal E. coli infection:
Definition

abdomen/pelvis

may => peritonitis, diverticulitis, appendicitis or visceral abscess

Term
E. coli caused pneumonia
Definition

more common occurrence in hospital borne pneu

(GNBs cause ~70% nosocomial pneumonia)

(E. coli is rarely a cause of community pneumonia)

Term
E. coli causes cellulitis
Definition

frequently infects decubitus ulcer

also infects extremities in diabetic pts

Term

1. Where does bacteremia/septicemia arise (w/ E. coli infection)?

2. What is the most common source of bacteremia?

Definition

1.at any extra-intestinal site

2. Escherichia coli UTIs

Term
top three bacterial causes of UTIs
Definition

1. Escherichia coli (60%)

2. Klebsiella (20%)

3. Proteus (15%)

Term
name the 5 strains of E. coli that cause Gastroenteritis
Definition

1. enteropathogenic E. coli (EPEC)

2. enterotoxigenic E. coli (ETEC)

3. enterohemorrhagic E. coli (EHEC)

4. enteroinvasive (EIEC)

5. enteroaggregative (EAEC)

Term
major cause of non-bloody INFANT diarrhea in the underdeveloped countries, describe the mechanism
Definition

EPEC (enteropathogenic E. coli)

mechanism: Bfp, intimin, Tir allow attachment to intest epithel cells => destruction of microvillus => malabsorption/watery diarrhea 

Term
major cause of non-bloody diarrhea worldwide, especially in children, also called "traveler's diarrhea"-describe virulent factors
Definition

enterotoxigenic E. coli (ETEC)

virulence: heat-labile (LT1-cholera like toxin incr cAMP) & heat-stable (STa toxin incr cGMP) => fluid loss 

Term
organism that causes the most GI infections in the US, describe
Definition

enterohemorhagic E. coli (EHEC) O157:H7 serotype most common in the US

transmission: undercooked meat, vegetables, unpasteurized milk, fruits, water

virulence: shiga toxins (Stx-1) => disrupt protein synthesis => inflammation/lesions/destruction of intestinal villus => fluid secretion

presentation: mild --> bloody diarrhea, severe abdominal px

progression: may => HUS & kidney failure

Term
describe enteroinvasive E. coli (EIEC)
Definition

prevalence: mostly underdeveloped countries

virulence: plasmid mediated invasion & destruction of colonic epithelial cells

presentation: fever, cramp, watery diarrhea --> dysentery w/ scant bloody stools; progresses like Listeria & Shigella

Term
describe enteroaggregative Escherichia coli (EAEC)
Definition

=> infant bloody diarrhea (underdeveloped countries)

presentation: persistent watery diarrhea w/ vomiting, dehydration & fever

virulence: stacked bricks (plasmid-encoded behavior of rods) => short microvilli => poor reabsorption

Term
what are the two most common gastroenteritis causing strains of Escherichia coli?
Definition

-ETEC: traveler's diarrhea; organism in feces; toxins; LT & ST genes

-EHEC: serotype O157:H7; low amt of organism in feces; shiga toxins/genes; usually sorbitol non-fermenters

Term
Which organism is an oxidase negative, citrate & urease test negative, lactose fermenting motile rod?
Definition
Escherichia coli
Term
age groups most commonly infected by salmonelosis
Definition

<5 yr

older adults >60 yr

Term
name the important species & serovars of Salmonella:
Definition

1. Salmonella enterica - clinically more significant

Serovars: Typhimurium & Typhi & Paratyphi

2. Salmonella bongori

Term
common transmission of Salmonella
Definition

poultry & dairy products & undercooked meat

-Salmonella enterica infects the ovaries/upper oviduct tissues of hens

Term
pathogenesis of Salmonella: bacteria can traverse the intestinal layer through...
Definition

-phagocytic microfold (M) cells in peyer's patch => membrane ruffles in intest epithel cells => trap salmonella/induce their endocytosis (w/ salmonella present, epithelial cells secrete IL8 => attract PMNs --> PMN's toxic substances damage intest mucosa => inflammatory diarrhea)

*NTS => massive PMN infiltration (large/small bowel mucosa)

*TTSS play key role in endocytosis/intracell surviv

Term
describe the most common form of salmonellosis
Definition

gastroenteritis

symptoms: fever, vomiting, water diarrhea, cramps

tx: NO antibiotics, usually self-limiting

Term
most common NTS that causes bacteremia
Definition
Salmonella Choleraesuis
Term
most common Salmonellas that causes bacteremia
Definition
Salmonella Paratyphi & Salmonella Typhi
Term
pathogenesis of typhoidal salmonella
Definition

invade: epithelium like other Salmonella --> disseminate through body via macrophages traveling through lymphatics

colonize: reticuloendothelial tissues (liver, spleen, bone marrow) --> re-enter GI tract => re-exposure => intestinal ulcers & necrosis

*Salmonella Typhi => mononuclear cell infiltration (not same as GI PMN infil during NTS infections)

Term
Enteric fever: presentation, progression, w/o tx?
Definition

Salmonella Typhi

early presentation: rose spots on trunk & chest (rash where bacteria is present), hepatosplenomegaly, epistaxis 

progression: bradycardia @ peak of fever

w/o tx: severely ill (GI bleeding/perforation <= hyperplasia & ulceration)

Term
identify Salmonella
Definition

gram-

oxidase-

motile rod

lactose non-fermenter

produce H2S

SS agar: grilliant green, ox bile, high thiosulfate & citrate inhib normal flora (H2S production detected by using thiosulfate & iron - colonies -> black color)

Term
name the 4 species of Shigella
Definition

Shigella dysenteriae

Shigella boydii

Shigella flexneri

Shigella sonnei

Term

1. Name the 5 F's

2. What organism is this associated w/?

Definition

1. Food, Flies, Feces, Fingers, Fomites

2. Shigella

Term
Where does the Shigella bacteria invade the colonic mucosa?
Definition

through M cells of Peyer's Patches

causes mucosal destruction/inflammation

rarely invades the bloodstream

Shigella dysenteriae => shiga toxin (inhib protein synthesis => cell death)

*remember, once these bacteria are inside the cells, they will stay there

Term
what are the two Shigella most common in the US?
Definition

Shigella sonnei

Shigella Flexneri

*neither => shiga toxin => less severe disease (watery diarrhea)

 

Term
What specifically do the shiga toxin+ strains (Shigella) damage?
Definition
glomerular epithelium => HUS
Term
identify Shigella
Definition

non-fermenters (white colonies on MacConkey)

H2S non-producer

neutrophils in fecal stain

 

Term
differentiate bt/w Escherichia coli & Shigella & Salmonella
Definition

1. motility: 

Shigella-not

E. coli-motile

2. H2S production (black colonies on SS agar)

Shigella-not a producer

Salmonella-yes a producer

Term
3 most important human pathogens of genus: Yersinia
Definition

1. Yersinia enterocolitica

2. Yersinia pseudotuberculosis

3. Yersinia pestis

Term
identify Yersinia enterocolitica
Definition

gram- rod

zoonotic pathogen

non-lactose fermenter

motile only @ 28* C

Term
epidemiology of Yersinia enterocolitica
Definition
transmission: oral route from raw meat, unpasteurized milk, fecally contained water
Term
Yersinia enterocolitica virulence
Definition

*70kb plasmid essential (at least 6 genes for outer mem proteins => cytotoxicity, resist phago, apoptosis of host cells)

-chrom inv prod => translocation across epithelium

Term
Bodily target of Yersinia enterocolitica:
Definition
terminal ileum
Term
main presentation of Yersinia enterocolitica diseases:
Definition

acute diarrhea <= enteritis or enterocolitis

also: low fever & cramping 

Term
Identify: GNB w/ prominent capsule, non-fastidious, facultative, oxidase-, lactose fermenting, motile
Definition
Klebsiella
Term
most common/important Klebsiella species (1)
Definition

Klebsiella pneumoniae 

-causes majority of Klebsiella infections in LTCF, hospitals & community

Term
Klebsiella pneumoniae diseases
Definition

1. Pneumonia: minor cause of community; usually lobar (acute, severe, destructive)

2. UTI: not that common

3. Soft-tissue infection: affects devitalized tissues (decubitus & diabetic ulcers & burn sites)

4. Bacteremia: can be caused from infection at any site

Term
Identify Klebsiella granulomatis
Definition

gram- 

encapsulated rod

intracellular pathogen

(has never been cultured)

donovan bodies w/in macrophages (pathognomonic sign)

Term
cause of ~70% STI cases in age group 40-70 
Definition
Klebsiella granulomatis (but this pathogen is also seen in children and sexually inactive adults)
Term
diseases of Klebsiella granulomatis
Definition
-Granuloma inguinale: begins w/ 1 or more subcut nodules --> erode through skin => clean, granulomatou, sharply defined, painless lesions that slowly enlarge (progressive erosion may completely destroy penis/other organ)
Term
Significant Proteus species:
Definition

1. Proteus mirabilis: causes ~90% of Proteus infections

2. Proteus vulgaris

 

normal flora in GUT, soil, & water 

Term
virulence factors for Proteus
Definition

adhesins

flagella 

IgA protease

urease

Term
diseases caused by Proteus mirabilis
Definition

UTI

wound infections

kidney (from urinary tract; more commonly than E. coli)

Term
identify Proteus mirabilis
Definition

lactose non-fermenter

do not form regular colonies

"swarming colonies" from high motility

urease+

Term
[image]
Definition
three most common bacterial causes of UTIs and their distinguishing characteristics
Term
[image]
Definition
3 common causes of GI infections and their distinguishing characteristics
Term

gram-

non-spore forming

anaerobic rods

(name the two genera)

Definition

1. Bacteroides prevotella and Bacteroides porphyromonas (rod or coccobacilli)

2. Fusobacterium (longer rods tapering end)

Term
Bacteroides fragilis diseases
Definition

most common cause of intra-abdominal infections

also: sinusitis, otitis, brain/liver abscesses, pneumonia, skin & soft-tissue infection

Term
identify Bacteroides fragilis
Definition

weakly gram- staining

small pleomorphic rod

strict anaerobe

foul smelling wound w/ presence of gas

Bile Esculin agar: B. fragilis (black growth) vs. Proteus mirabilis (no growth)

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