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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