EnterobacteriaceaeLecture -17

Dr.Baha,H. AL-AmiediPh. D.Microbiology

Gram-negative rods

EnterobacteriaceaeCharacters of Enterobacteriaceae

AllEnterobacteriaciaeGram-negative rods

Ferment glucose with acid productionReduce nitrates into nitrites

Oxidase negativeFacultative anaerobic

exceptMotileShigellaandKlebsiellaNon-capsulated except Klebsiella

Non-fastidiousGrow on bile containing media (MacConkey

agar)

EnterobacteriaceaeSome Enterobacteriaceae are true pathogens

Salmonella.sppShigella.sppYersinia.spp

Certain strains ofcoli.E,EPEC,ETEC(EIEC, EHEC)

areEnterobacteriaceaeMost members of theopportunisticor cause secondary infections of

wounds, the urinary and respiratory tracts, andthe circulatory system e.g. E. coli.

Enterobacteriaceae divided into TWO maingroups according to action on LACTOSE

Lactose Fermenters (LF)E. coli, Citrobacter, Klbesiella,

EnterobacterLactose Non-Fermenters (LNF)Salmonella, Shigella, Proteus,

YersiniaIdentification of Enterobacteriaceae

Gram stainAll Enterobacteriaceae are Gram-negative

rodsArranged in single

Virulence Factors Associated withEnterobacteriaceae

Common Virulence FactorsEndotoxin

CapsuleAntigenic phase variation

Sequestration of growth factorsResistance to serum killing

Antimicrobial resistance

Factors Associated with SpecificPathogens

Exotoxin productionExpression of adhesion factors

Intracellular survival andmultiplicationEndotoxine(LPS)

Endotoxine (LPS):is composed of three part1-polysaccharide core

2-O-Antigen3-Lipid A

Not all Endotoxine are equally toxic,Toxicityseem depend on structural variation of lipid A.the lipid A represent the major surface Antigenof bacterial cell wall and cause fever byrelesing toxins. It is stable at 100 C.Exotoxine

Exotoxine: such as the enterotoxins produceby E coli,shigella ,vibro cholera , klebsiellapneumonia &psedomonas aeroginosa ,it isprotien & donot cause fever ,unstable at 100 C.Excreted by living bacterial cell. It stimulatingformation

Of neutralization of Antibodies.Adhesion colonization factors

are involve in bacterial attachment to cell andtissues

And in bacterial conjugation fimbriae (pilli)Usually play the role of adhesion factors.

Capsules:either antiphagocytic as in klebsiella &E coli

responsible for neonatal meningitis or preventdestruction in phagocytes as in case ofsalmonella.

Endotoxin-Mediated ToxicityFever

Leukopenia (reduced # of WBCs)(<5000/mm3)followed by

leukocytosis (increased # ofWBCs)(>10-12,000/mm3)

Activation of complementThrombocytopenia (reduced # of

platelets)DIC (Disseminated intravascular

coagulation)Decreased peripheral circulation and

perfusion(blood flow) to major organsShockDeath

Escherichia coliIt is Gram negative short bacilli ,non-

capsulated ,non-motile,aerobic& faculltativeanaerobic,lives only on human or animalintestine so detection of E coli in drinkingwater as evidence of recent pollution withhuman or animal excreta.

Antigenic structure:they have complex antigenic structure with

1-asomatic lipopolysaccharide antigendesigenated as(O )

2-aheat labile capsulr antigen (K)with itscomponents L,A,B

3-Flagellar Antigen (H)E coli produce four type of clinical infection

:1-Diarrhea2-Urinary tract infection

3-poygenic infection4-septicaemia

Diarrhea infectionFour group of Ecoli are involved in production

of diarrhea in infant ,older ,children &adult.1-Enteropathogenic Ecoli(E.P.E.C)produce

diarrhea in children,in infent sever diarrhea2-Enterotoxigenic E coli(E.T.E.C):cause

travelerDiarrhea in adult ,the effect of exotoxins

produced by them,3-Enteroinvasive Ecoli (E.I.E.C):they are

found in older children &adult . Due to invadbacilli intestinal epithelial cell.they do notproduce toxins.

4-enterohaemorrhagic E coli(E.H.E.C):Produce haemorrhagic colitis due totoxine

Laboratory diagnosis1-cultural character:the sample grow onMacConky agar which containe lactose &PH indicater E coli usually ferments lactose,

acide will be generated & the colonies willturn pink.

2-biochemical reaction:it fermentslactose,glucose,manitol,maltose with acid

And gase .lndole&methyl read is positiveCitrate is negative&urease not hydrolysed3-using specific serotypes depend on antigen

ProteusIt is gram negative rod motile &show

swarming of growth in proteus vulgaris &Proteus mirabilis while absent in other species

, aerobic & facultative anaerobic,Non-sporing &non-capsulated ,culture emit

characteristic putrefactive (fishy) odor.produce urease (several species),

There are four species in this genus;1-proteus vulgaris2-proteus mirabilis3-proteus morganii4-proteus rettigeri

Antigenic composition :like most gramnegative enterobacter proteus species haveH,O and K antigen

Proteus vulgaries are agglutinated by sera oftyphus patient due to sharing of species

Polysaccharide in antigen with rickettsiaeThis used as basis of well-felix agglutination

Test for typhus infectionPathogenecity: it is opportunistic pathogenCause urinary tract infection ,may produce

Pyogenic lesion like abscess infection ofwound

Ear or respiratory tract.Klebsiella

It is gram negative , non-motile, capsulatethick& bacilli producing mucoid pink colonieson MacConky medium,it is found in mucosa ofupper respiratory tract, intestinal &urinarytract infection , it is member of Normal florathat may cause sever systemic infection undercertain condition immunocompromis,debiluitation.Klebsiella pneumoniae

It is responsible for the most infection whichmay cause pneumonia &lung abscesses alsomay cause urinary tract infections .Virulence factor for Klebsiella pneumoniae

1-capsular mucoid polysaccharide which can

resist to action of phagocytes.2-some strain carry plasmid coding for

production heat –stable enterotoxine3-antibiotic resistance due to species contain

resistance plasmids(R-plasmids)which conferresistance to antibiotic

Identification ofIdentification of EnterobacteriaceaeEnterobacteriaceae

Gram stainGram stain

AllAll EnterobacteriaceaeEnterobacteriaceae are Gramare Gram--negative rodsnegative rods

Arranged in singleArranged in single

Endotoxine(LPSEndotoxine(LPS))

Classification ofClassification of EnterobacteriaceaeEnterobacteriaceae according toaccording tolactose fermentation (growth onlactose fermentation (growth on MacConkeyMacConkey

Agar)Agar)

Classification ofClassification of EnterobacteriaceaeEnterobacteriaceae according toaccording tolactose fermentation (growth onlactose fermentation (growth on MacConkeyMacConkey

Agar)Agar)

EnterobacteriaceaeEnterobacteriaceae

Lactose Non-Fermenters

Colorless colonies

Salmonella sppSchigella spp

Proteus sppYersinina spp

Lactose Fermenters

Acid

Pink colonies

Escherichia coliKlebsiella spp

Enterobacter sppCitrobacter spp

No acid

Neutralred