1. ENTEROBACTERIACEAE .

2. ENTEROBACTERIACEAE Objectives: Definitions Scientific Classification
Common features
Growth on differential media distinguishing properties
Strains specific virulence factors , diseases and common treatment

3. ENTEROBACTERIACEAE
Definition: A family of aerobic and anaerobic Gram-negative bacteria that includes, both normal and pathogenic enteric microorganisms they are able to reduce nitrates to nitrites and to ferment glucose with production of acid and gas ie:Salmonella, Escherichia coli, Yersinia pestis, Klebsiella and Shigella.

4. Identification features
Antigenic features (Serological):
They have complex antigenic structure grouping into three antigens:(O somatic,H flagellar and K capsule)
O antigens: The most external part of the cell wall lipopolysaccharides, O antingens are resistant to heat and alcohol.
H antigens: They are located on flagella they are denatured or removed by heat or alcohol
Capsular antigens: They are external to O antigens but not all enterobacteriaceae some are polysaccharides others are proteins in nature

5. Scientific Classification
Domain: Bacteria
Phylum: Proteobacteria
Class: Gammaproteobacteria
Order:Enterobacteriales
Family: Enterobacteriaceae
Genera:

6. Identification features cont..
Structure:
Are Gram-negative rods with lipopolysaccharides in their cell envelope.
Most have flagella and motile except shigella
Some have capsules
Biochemical and growth properties:
All ferment glucose and are oxidase negative
Lactose fermenting genera are benign, non lactose fermenting ones are more pathogenic
All are facultative anaerobes survive in GI tract
They grow well on MacConkey medium

7. Virulence Factors Virulence determinants:
Endotoxin: Part of lipopolysaccharides are produced by all Enterobacteriaceae responsible for systemic infection establishment.
Exotoxins: Produced by some species leading to diarrhoea
Adhesins and fimbriae: Found on some species help in adhesion to the colon,bladder or on other tissues.
Intracellular growth and enteroinvasive: Protects them from host defenses i.e: Shigella,Yersinia and E.coli respectively

8. Virulence Factors cont…
e. Antibiotic resistance: Develops rapidly f. Capsule: On some spp. Which is antiphagocytic ie:Klebsiella spp. and Salmonella spp.

9. Epidemiology
The Enterobacteriaceae have Worldwide distribution pattern found in the soil , water and vegetation they are part of intestinal flora of many animals and humans.
Human pathogens: The invasive and that associated with diseases in man are: Salmonella , Shigella and Yersinia.
Opportunistics: E.coli,Klebsiella,Enterobacter,Proteus generally they are not invasasive and part of normal flora-Disease is by compromised immunity or introduced into sterile site.

10. Lactose-Fermenting Enterobacteriaceae
Escherichia coli (Normal flora of lower human GIT) found in normal stool form pink colonies on MacConkey medium
Pathogenesis:
Endotoxin: Caused by all strains
Noncytotoxic enterotoxins: Caused by enterotoxigenic strains(ETEC)
Heat labile enterotoxins leading to altered electrolyte transport and diarrhoea.
Heat stabile enterotoxins leading to fluid loss and diarrhoea

11. Lactose-Fermenting Enterobacteriaceae cont…
c. Verotoxin: a shiga like toxin –cytotoxic to intestinal villi and colon epithelial cells enterohemorrhagic strains.(EHEC) d. Invasion and destruction of colonic epithelial cells: Enteroinvasive strains(EIEC) e. Adherence to mucosa of small intestine:(Plasmid mediated): Enteropathogenic strains and enteroaggregative strains.(EAggEC) f. P fimbriae-mediated adherence to uroepithelium: Uro-pathogenic strains(UPEC)

12. Diseases caused by E.coli
Gastroenteritis: Clinical manifestations are strain specific.
E.coli strain
Site of Action
Clinical Features
Pathogenesis
Enterotoxigenic
(ETEC)
Small intestine
Waterly diarrhoea,cramp, nausea,low grade fever travelers& infants
Enterotoxins promote cAMP hence electrolyte loss
Enteroaggregative (EAggEC)
Persistent infant diarrhea,low grade fever
Aggregative adherence to mucosa prevents fluid absorption.
Enteropathogenic
(EPEC)
Copious watery infant diarrhoea,vomiting mucoid stool
Adherence and destruction of epithelial cell
Enteroinvasive
(EIEC)
Large intestine
Fever,Cramps,watery diarrhoea,dysentery
Invasion and destruction of epithelial cells lining the colon
Enterohemorrhagic
(EHEC)
Severe Cramps,Blood diarrhoea(hemorrhagic colitis)
Cytotoxic verotoxin inhibits protein synthesis

13. Diseases caused by E.coli cont….
b. Hemolytic uremic syndrome(HUS): Complication of gastroenteritis caused by EHEC which occurs primarily in children associated with undercooked beef products leads to acute renal failure,thrombocytopenia c. Urinary tract infection(UTI): Cystitis and pyelonephritis are common conditions d. Neonatal meningitis: Associated with strains that have capsular antigen e. Septicemia: The organisms enter circulation from GIT or Urinary tract-Common cause of gram –ve septicemia

14. Transmission Endogenous transmission(originating from within ):
This originates from within the source ie: normal flora from the bowel
Nosocomial transmission: Transmission from infected colleague ie: Hospital
Ingestion of contaminated food or water
Treatment:
Antibiotic choice depends on the site of infection and susceptibility of organism

15. Klebsiella pneumoniae
Pathogenesis:
Has prominent capsule that hinders phagocytosis and important for virulence.
Diseases:
Primary lobar pneumonia which results from inhalation of organisms into the lungs(Alcoholic and compromised individuals are at high risk of the infection).
Bacteremia and UTI also Klebsiella are implicated

16. Enterobacter,Citrobacter and Serratia
These species are rarely cause infection unless an individual is immunocopromised
Multiple antibiotic resistance is common in Enterobacter

17. Medically important Enterobacteriaceae and Diseases
ORGANISM
DISEASES
Lactose Positive:
E.Coli
Klebsiella,Serratia,Citrobacter,Enterobacter
-Diarrhoea ,sepsis,UTI Neonatal meningitis
-Opportunistic infection (e.g pneumonia, neonatal meningitis and sepsis)
Lactose Negative:
Salmonella
Shigella
Proteus
Yersinia
-Diarrhoea,typhoid fever,bacteremia,eustiomyelitis,menigitis,liver disease
-Dysentery
-UTI
-Plague.mesenteric lymphadenitis,diarrhea

18. Colony Morphology- Some Enterobacteriaceae
LACTOSE
FERMENTERS
NON LACTOSE
Medium
E.coli
Klebsiella
Salmonella
Shigella
MacConkey agar
Eosin-methylene blue(EMB)agar
Hektoen enteric (HE)Agar
Salmonella-Shigella agar
Purple/pink
Red/black
Yellow/orange
Pink
Purple
Colourless
Blue green with black centre
Colourless with black center
Green/blue green

19. Non Lactose Fermenting Enterobacteriaceae
Salmonella:
They are normally found in many animals GIT but not among normal human flora many serotypes are identified based on surface antigens.
Pathogenesis:
They have antiphagocytic capsule
They growth and replicate intracellularly
Endotoxin and exotoxin(Produces by some serotypes cause enteritis)

20. Non Lactose Fermenting Enterobacteriaceae
Diseases:
Enteritis(S.enteritidis and other serotypes) Incubation period hrs -Spontaneous recovery takes place within 2-7days
Typhoid(enteric) fever (S.typhi) Incubation period: 10-14days
Bacteremia
Localized infections in other sites(e.g Osteomyelitis,Meningitis, Liver)

21. Non Lactose Fermenting Enterobacteriaceae
Transmission:
All serotypes are transmitted by Fecal oral route
Ingestion of large numbers organisms in contaminated water and food(eg: raw eggs , improperly cooked chicken etc.)
Asymptomatic carriers(S.typhi) Some who recover from typhoid fever may continue to carry S.typhi in gallbladder for months

22. Non Lactose Fermenting Enterobacteriaceae
Shigella
All four species are pathogenic to human
Pathogenesis:
Invasion of colonic mucosa and replication takes place in mucosa cells
S.dysenteriae produces Shiga toxin(typeA-B) that inhibits protein synthesis
Bacillary dysentery(Shigellosis)
Causes profuse watery diarrhoea,abd cramps and fever,Tenesmus and bloody stool

23. Shigella cont….. Transmission: Transmission is by Fecal – oral route
Ingestion of contaminated food or water from human
Treatment:
Rehydration –necessary
Antimotility agents(e.g Clotrimazole) but may prolong disease.

24. Non Lactose Fermenting Enterobacteriaceae
Yersinia pestis:
Found in numerous small animals like dogs , cats and transmittable to human by fleas.
Pathogenesis:
It has antiphagocytic capsule,grow intracellularly and produces exotoxin and able to disseminate from infection site
Disease caused by Yersinia pestis:
Bubonic plague-Acquired from bite of infected flea

25. Non Lactose Fermenting Enterobacteriaceae
Bubonic plague cont..
IP: 7days
High fever,painful bubo(Inflammed swollen lymph node) in groin or axilla, bacteremia that can lead to death if untreated(Mortality rate >75%)
Pneumonic plague: Acquired by inhalation of infectious droplets from infected person.
IP: 2-3 days
Fever,malaise followed by respiratory problem then death (Mortality rate >90%)

26. Non Lactose Fermenting Enterobacteriaceae
Pneumonic plague cont….:
Prevention and Treatment:
Effective pest control , isolation of infected patients and vaccination.
Treatment: Streptomycin ,Gentamycin, Chloramphenicol and Tetracycline

27. Non Lactose Fermenting Enterobacteriaceae
Yersinia enterocolitica:
Carried by livestock , rabbits and rodents transmitted though contaminated food and water or blood products.
Diseases:
Enterocolitis( Common)-Blood diarrhoea,fever and abdominal pains (Chronic-may last for a year).
Mesenteric lymphadenitis:-Enlargement of mesenteric lymph nodes can present like appendicitis-Common in young children

28. Non Lactose Fermenting Enterobacteriaceae
Yersinia enterocolitica cont…..:
Transfusion related septicemia:
Y.enterocolitica can grow at low temperatures and multiply to toxic level in refrigerated blood stored for several weeks.
Proteus mirabilis:
Normal flora of human GIT
Common cause of UTI marked by elevated urine pH

29. .
THANK U FOR LISTENING