Enterobacte Lec. 5

8/17/2019 Enterobacte Lec. 5

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EnterobacteriaceaeEnterobacteriaceaeLec5


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1-Cytolytic toxins

2-A-B toxins


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Exotoxin Include membrane-disrupting enzymes,such as the α-toxin (phospholipase C) producedby C.perfringens, which breaks down membranephospholipids

The B portion of the A-B toxins binds to aspecic cell surface receptor, and then the Asubunit is transferred into the interior of thecell, where it acts to promote cell injury


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The largest, most heterogeneous collection of medicallyimportant gram-negative rods

>40 genera and 150 species

e!er than "0 species are responsible for more than #5$of the infections

%t found !orld!ide in soil, !ater, and vegetation


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part of the normal intestinal flora

&0$ to &5$ of all septicemias, more than '0$ of urinarytract infections ()T%s*, and many intestinal infections

Salmonella typhi, Shigella species, Yersinia pestis

Escherichia coli, Klebsiella pneumoniae, Proteusmirabilis


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+ecome pathogenic !hen they acuire virulence factor

an originate from an animal

.r from a human carrier

.r through the endogenous spread of organisms

erment glucose, reduce nitrate

atalase positive and o/idase negativeoderately sied

2ram-negative rods

Either nonmotile or motile !ith peritrichous flagella

3o not form spores ome have capsules

acultative anaerobes

6ave simple nutritional reuirements

7esistance to bile salts in some selective medium


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There are several selective and diferential mediaused to isolate distinguishes between LF & LNFThe most important media are:

MacConkey agarosin Methylene !lue "M!# agar$almonella $higella "$$# agar%n addition to Triple $ugar %ron "T$%# agar


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Method:Method:

acCon!ey a"ar is inoculated with testedacCon!ey a"ar is inoculated with tested

or"anismor"anism usin" strea! plate techni#ueusin" strea! plate techni#ue

$ncubate the plate in incubator at %& C'2( hrs$ncubate the plate in incubator at %& C'2( hrs

esults:esults: )* or"anism appears as pin! colonies +e")* or"anism appears as pin! colonies +e" E.E.

colicoli

.)* or"anism appears as colorless colonies.)* or"anism appears as colorless colonies

+e"+e" ShigellaShigella


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T%


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'ram stain o('ram stain o( Salmonella typhi Salmonella typhi (rom a positive blood culture)(rom a positive blood culture)

Note the intense staining at the ends o( the bacteria)Note the intense staining at the ends o( the bacteria)

This *bipolar staining* is characteristic o( theThis *bipolar staining* is characteristic o( the

nterobacteriaceaenterobacteriaceae


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Sites of infections with common members of theSites of infections with common members of the

EnterobacteriaceaeEnterobacteriaceae


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L89 onsists of three components9

the outermost somatic . polysaccharide

a core polysaccharide common to all Enterobacteriaceae (enterobacterial common antigen*

lipid :


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serologic classification . polysaccharides

capsular ; antigens(type-specific

polysaccharides* the flagellar 6 proteins

Antigenic structure of EnterobacteriaceaeAntigenic structure of Enterobacteriaceae


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Common Virulence Factors Associated withEnterobacteriaceae Endoto/in apsule

:ntigenic phase variation (variation in e/pression of antigens., ; or 6 protect cell from antibody mediated cell death*

Type %%% secretion systems (!hich is molecular syringe of "0 proteins that facilitate transfer of bacterial virulence factorinto the host and !ithout it bacteria becomes less virulence*<

euestration of gro!th factors (such as siderophores production !hich chleating iron from hemeprotein ofhemoglobin*


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7esistance to serum =illing (+acterial capsules can protectthe organism from serum =illing and prevent the binding of

bacteria to complement and so subseuent complement-mediated clearance*

:ntimicrobial resistance (since organism can developresistance to antibiotics and encoded on transferable

plasmids !hich e/change among bacterial spp


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epsis(presence of pus forming bacteria in body*,)T%s, meningitis, gastroenteritis

2ram-negative, facultative anaerobic rodsLactose fermenter o/idase negative.uter membrane ma=es the organisms susceptible to

dryingLipopolysaccharide consists of outer somatic .

polysaccharide, core polysaccharide (common

antigen*, and lipid : (endoto/in*


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Incidence of Enterobacteriaceae associated with bacteremiaIncidence of Enterobacteriaceae associated with bacteremia


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Diseases +acteremia (most commonly isolated gram-negative rod*)rinary tract infection (most common cause of bacterial )T%s*

limited to bladder (cystitis* or can spread to =idneys(pyelonephritis* or prostate (prostatitis*

:t least five different pathogenic groups cause gastroenteritis

(E8E, ETE, E6E, E%E, E:E ?eonatal meningitis (usually !ith strains carrying the ;1

capsular antigen* %ntraabdominal infections (associated !ith intestinal perforation*ost infections are endogenous


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1-/astroenteritisenteropatho"enic +00C

enterotoxi"enic +0T0Centerohemorrha"ic +00C

enteroin3asi3e +0$0Centeroa""re"ati3e +0A0C 0 coli


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0T0C4 Tra3eler5s diarrhea6 infant diarrhea inde3elopin" countries6 watery diarrhea,3omitin", cramps, nausea, low-"rade fe3er lasmid-mediated, heat-stable and'or heat-

labile enterotoxins that stimulatehypersecretion of 7uids and electrolytes


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E8E9 %nfant diarrhea in underdeveloped countries!atery diarrhea and vomiting, nonbloody stools< 8erson to person spread

8lasmid-mediated

?onfimbrial adhesin oderately invasive


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0A0C4 $nfant diarrhea in underde3elopedcountries6 tra3eler5s diarrhea, persistent orchronic diarrhea

lasmid-mediated a""re"ati3e adherence of

rods0nteroa""re"ati3e heat stable toxin +0A8T

Bric!-li!e a""re"ates on cell surfaces


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E6E9 %nitial !atery diarrhea, follo!ed by grossly bloody diarrhea (hemorrhagic colitis* !ith abdominalcramps little or no fever may progress to hemolyticuremic syndrome (6)* develops !hen the to/in from E<

coli bacteria, =no!n as higa-li=e to/in (LT* , enters thecirculation by binding to special receptors

6emolytic uremic syndrome (6)*uremic syndrome (6)* characteried by brea=up of red blood cells and acute =idney failure<


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0$0C4 9isease in underde3eloped countries6fe3er, crampin", watery diarrhea6 maypro"ress to dysentery, bloody stools, fe3er,se3ere in7ammation

lasmid-mediated in3asion and destruction ofepithelial cells

8ome are non motile strains,


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0coli in Colon contaminate urethraascend into bladder and may mi"rate to

!idney or prostate

:T$s4 due to bacterial 3irulence factor such asadhesins +primarily pili and hemolysin lyAthat lyses erythrocytes ; other cells


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E


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ay be originated from )T or 2%

ortality (death rat* is high

Enterobacte Lec. 5

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