Enterobacteriaceae

1. Enterobacteriaceae
Coliforms-proteus
Shigella
Salmonella

2. Aerobic
Non- sporing,
Non-acid fast,
G-ve bacilli
Intestinal flora

3. Old classification
Salmonella, ShigeelaNon lactose fermenters
Shigella
sonnei/Paracolons
Late lactose fermenters
Escheria,KlebsiellaLactose fermenters

4. New classification
ErwiniaErwinieaeTribe 4
Proteus,Morgenella.ProvidenciaProteeaeTribe 3
Klebsiella,Enterobacter,Hafnia,
Serratia
KlebsielleaeTribe 2
Escherichia,Edwardsiella,Citrob
acter,Salmonella,Shigella
EscherichiaeTribe 1

5. E.coli
Motile-peritrichate flagella,aerobe &
facultative anerobe
Good growth in ordinary media
Culture-fresh isolation-S/smooth form-easily
emulsifiable in saline
Rough forms-/R forms-irregular,dull surface-
autoagglutinable in saline
S-R variation occurs due to subculture-loss of
surface antigens and virulence

7. MacConkey’s agar- bright pink-
IMViC ++--(Indole ,Methyl red,Voges-
Proskauer and citrate utilisation tests

9. Antigenic structure

10. Somatic antigen O,
capsular antigen K-1 and 2,(1resp for
neonatal meningitis..)
Flagellar antigen H
Toxins-exo-hemolysisns and enterotoxins
Enterotoxins-heat labile(LT)—heat stable(ST)
—verotoxin (VT)/Shiga like toxin/SLT

12. ST- two types –A &B-
A-activate cGMP---fluid accumilation
B-activate cGMP/cAMP
VT-similar to Shigella dysenertae Type 1
toxin-
VT A & B subunits-phge encoded
Fimbrae-imp in UTI-P fimbriae binds
specifically to the P blood group substance
on RBC and uroepithelial cells

13. Clinical infections
1.UTI
2.Diarrhea
3.Pyogenic infections
4.Septicemia

14. Urinary Tract infection
Majority of naturally occuring UTI
By those found in feces-O grops-1,2,4,6,7.
Infection may be precipitated by
obstruction,prostatic
enlargement,calculi,pregnancy
Asyymptomatic bacteriuria-5-7% of pregnant-
UTI without no symptoms----can lead to
pyelonephritis,hypertension,premature
births,death of fetus

15. Significant bacteriuria-collect mid tream
sample of urine—sterile wide mouthed
container---lab without delay
In presence of Active infection->= 1 lakh
bacteria /ml----significant bacteriuria
Less than 10’000-not sig
Between equivocal
Semi quantitative-one loopful of urine in non-
inhibitery medium & other in indicator
medium
Former gives quantitative measurement of
bacteriuria-later presumptive diagnosis

16. Antibiotics sensitivity is very imp-done using urine
sample as inocula
Screening tests for presmptive d/g of significant
bacteriuria
3.Griess Nitrate test-+ve –Nitrate reducing b.
4.Catalase test-+-bacteriuria and hematuria
5.Triphenyl Tetrazolium chloride test/TTC –
6.Microscopic demo
7.Glucose test paper
8.Dip slide culture methods
9.The antibody coated bacteria test-to find site of
infection-specific antibodies are present in urine
only whn the kidnes are affected,otherwise inf. In
bladder

17. Diarrheagenic E coli
2.EP-pathogenic
3.ET-toxigenic
4.EH-haemorrhagic
5.EA-aggregative
6.EI-invasive
Diarrhea

18. EPEC
Infants
Do not produce enterotoxin,not invasive
Ininfantile enteritis-bacilli are seen adherent
to the mucosa of SI,to cup like projections of
enterocyte membrane---disruption of brush
border microvilli

19. ETEC
Endemic diarrhoea
Mild watery to fatal d/s
Traveller’s diarrhoea-
Entero toxins produced-LT/ST/both
First adhesion by fimbrial / Colonisation factor
antigens(1,2,3,4,)
D/g- ligated rabbit ilial loop,LT(invitro
methods-tissue culture)

20. EIEC
Resembles shigella-nonmotile,O antigen cross
reactivity
Enter invasive-capacity to invade interstitial
epithelial cellsinvivo, penetrate HeLa cells
C/f-mild diarrhoea to frank dysentery(resmble
shigellosis)
Children and adults
Lab dig- Sereny test-instillation of a suspension of
freshly isolated EIEC /shigella—g.pig eyes-
mucopurulent conjuntivitis
Cell penetration of HeLa/HEP2-d/gtic
Ability to penetrate-plasmid-
Plasmid codes for OM antigens called
VMA(Virulence Marker Antigens) which can be
detected by ELISA

21. EHEC/Shigatoxigenic/Verotoxigenic
Producing VT—mild diarrhoea to fatal
hemorrhagic colitis and hemorrhagic uraemic
syndrome/HUS-young children and yelderly
Primary target of VT is vascular endothelial
cells
In HUS_ch. Renal lesion-capillary micro
angiopathy
Source –contaminated human/animal feces
Food poisoning in veg-salad vegetables
Lab d/g-demo.,VT—DNA probes for VT1 and
VT2 genes –more sensitive-

22. EAEC
Appear aggregated in stacked brick
formaation on hep 2 cells
Persisitant diarr.

23. Septicaemia
Blood stream invasion-shock
Systemic Inflammatory Response
Syndrome(SIRS)

24. Shigella

25. Imp species
1.Shigella dysenteriae---Mannitol non
fermenting
2.Shigella sonnei-mannitol fermenting
3.Shigella boydii---mannitol fermenting
4.Shigella flexneri---mannitol fermenting

26. Dysentery-frequent passage of blood stained
mucopurulent stools
Bacillary and amoebic
MacConkey agar colourless-except shigella
sonnei-pink
Deoxycholate citrate agar-selective medium
Growth is inhibited in Wilson –Blair Bismuth
sulphite medium
Fermentation of mannitol is imp. In
classification-by SH.flexneri,boydii,sonnei
Not by Sh.dysenteriae

27. Antigens-O,K,
Classification
Sh.dysenteriae-mannitol non fermenting-
indole –ve,only member that is always
catalase +ve
Toxin –Shiga toxin by Sh.dysenteriae type 1-
earliest eg. Of an exotoxin produced by Gram
–ve bacillus
Neuro,entero,cyto toxicity
Shiga toxin has A and B units
A-A1 & A2-A1 inactivates host cell 60S
ribosomes

28. Sh.sonnei-catalase –ve,late lactose
fermenters
Mildest of the bacillary dysentery
MC shigellosis in developed countries

29. Pathogenicity
Shigella causes bacillary dysentery-infestion
occurs by ingestion
Low minimal infective dose-10-100 bacilli
only-as they survive gastric acidity than other
enterobacteria
Pathogenic mech. Similar to EIEC

31. Invasive property of bacillus can be
demonstrated by its ability to penetrate
cultured HeLa/Hep2 cells
Invasive property is related to the presence in
the bacillus of large plasmids coding OMP
responsible for cell penrtration—these
proteins are called VMAL(Virulence Marker
Antigens)
Detection of VMA by ELISA serves as a
virulence test for Shigella,as for EIEC

32. Bacillary dysentery
Ingestion----IP-1-7days,usually 48hrs
Frequent passage of loose,scanty feces
containing blood and mucus,along with
abdominal cramps and tenesmus
Cx-Sh.dysenteriae-type 1-arthritis,toxic
neuritis,conjunctivitis,parotitis,intussusception
HUS
T/t- based on sensitivity