1. بسم الله الرحمن الرحيم 1 1 1

2. Ass . Professor of of Medical Microbiology
Gram-Negative Rods
Enterobacteriaceae
Dr. Manal El Said
Ass . Professor of of Medical Microbiology

3. Characters of Enterobacteriaceae
All Enterobacteriaciae
- Gram-negative rods
- Ferment glucose with acid production
- Reduce nitrates into nitrites
- Oxidase negative

4. Characters of Enterobacteriaceae
Enterobacteriaceae divided into TWO main groups according to action on LACTOSE
Lactose Fermenters (LF)
Lactose Non-Fermenters (LNF)
E. coli
Citrobacter
Klbesiella
Enterobacter
Salmonella
Shigella,
Proteus,
Yersinia

5. Lactose fermenter: 1-Escherichia coli`
Lactose fermenter:
1-Escherichia coli
Diseases
Urinary tract infection (UTI)
Sepsis
Neonatal meningitis
Traveler's diarrhea
Characteristics
Facultative gram-negative rods
Ferment lactose.

6. Habitat and Transmission
Lactose fermenter:
1-Escherichia coli
Habitat and Transmission
Habitat is the human colon
It colonizes the vagina and urethra ascends UTI
Acquired during birth in neonatal meningitis
Fecal–oral route in diarrhea.

7. Lactose fermenter: 1-Escherichia coli Pathogenesis
1- Endotoxin
It causes septic shock.
Two enterotoxins are produced.
1- Heat-labile toxin
2- Heat-stable toxin
2- Pili
For attachment to mucosal surfaces

8. Lactose fermenter: 1-Escherichia coli Pathogenesis
3- Capsule
It impedes phagocytosis.
4-Verotoxin (Shiga-like toxin)
It is enterotoxin produced by O157:H7 serotype E. coli
It causes bloody diarrhea and hemolytic-uremic syndrome associated with eating undercooked meat.

9. Lactose fermenter: 1-Escherichia coli Pathogenesis
Predisposing factors to UTI in women include:
- Proximity of the anus to the vagina & urethra
- Short urethra.
Abnormalities e.g., strictures, valves & stones.
In-dwelling urinary catheters UTI
Intravenous lines sepsis
Colonization of the vagina neonatal meningitis.

10. Lactose fermenter: 1-Escherichia coli Laboratory Diagnosis
1-Gram-stained smear

11. Lactose fermenter: 1-Escherichia coli Laboratory Diagnosis
Lactose-fermenting colonies on Eosin Methylene Blue EMB (Green) or MacConkey's agar.
Uninoculated plate

12. Lactose fermenter: 1-Escherichia coli Laboratory Diagnosis
Triple Sugar Iron agar shows acid slant and acid butt with gas but no H2S.
Biochemical reactions.
Type organism by O & H antigens by using antisera.

13. Lactose fermenter: 1-Escherichia coli
Treatment
Urinary tract infections:
Ampicillin or sulfonamides
Meningitis and sepsis:
Third-generation cephalosporins
Traveler's diarrhea:
- Rehydration
- Trimethoprim-sulfamethoxazole
Antibiotic resistance mediated by plasmid-encoded enzymes:
- β-lactamase
- Aminoglycoside-modifying enzymes.

14. Lactose fermenter: 1-Escherichia coli Prevention
Prevention of UTI :
Limit the frequency and duration of urinary catheterization.
Prevention of sepsis :
Remove or switch sites of intravenous lines.
Prevention of Traveler's diarrhea :
- Eating only cooked food and drinking boiled water.
- Prophylactic doxycycline.
There is no vaccine.

15. 2-Klebsiella pneumoniae`
Lactose fermenter:
2-Klebsiella pneumoniae
Diseases
Pneumonia
UTI
Sepsis.
Characteristics
Facultative gram-negative rods
Polysaccharide capsule

16. 2-Klebsiella pneumoniae Habitat and Transmission
Lactose fermenter:
2-Klebsiella pneumoniae
Habitat and Transmission
Habitat is the human upper respiratory & enteric tracts.
Organism is transmitted to the lungs by:
- Aspiration from upper respiratory tract
- Inhalation of respiratory droplets.
It is transmitted to the urinary tract by ascending spread of fecal flora.

17. 2-Klebsiella pneumoniae
Lactose fermenter:
2-Klebsiella pneumoniae
Pathogenesis
Endotoxin causes fever and shock associated with sepsis.
Capsule : impedes phagocytosis.
No exotoxin known.
Chronic pulmonary disease predisposes to pneumonia
Catheterization predisposes to UTI.

18. 2-Klebsiella pneumoniae
Lactose fermenter:
2-Klebsiella pneumoniae
Laboratory Diagnosis
1-Gram-stained smear

19. 2-Klebsiella pneumoniae
Lactose fermenter:
2-Klebsiella pneumoniae
Laboratory Diagnosis
2- Lactose-fermenting on MacConkey's agar
Mucoid colonies (polysaccharide capsule)

20. 2-Klebsiella pneumoniae
Lactose fermenter:
2-Klebsiella pneumoniae
Laboratory Diagnosis
3- Differentiated from Enterobacter and Serratia by biochemical reactions.

21. 2-Klebsiella pneumoniae
Lactose fermenter:
2-Klebsiella pneumoniae
Treatment
Cephalosporins alone or with aminoglycoside.
Resistance is mediated by plasmid-encoded enzymes.
Prevention
No vaccine or drug is available.
Urinary & intravenous catheters should be removed .

22. 3-Enterobacter cloacae &Serratia marcescens
Lactose Fermenter:
3-Enterobacter cloacae &Serratia marcescens
Enteric gram-negative rod similar to K. pneumoniae. but they are motile
They causes :
- Hospital-acquired pneumonia
- UTI
- Sepsis
Highly antibiotic-resistant.

23. Lactose fermenter: Citrobacter
Enteric gram-negative rod similar to E. coli except being citrate positive.
Found in faeces of humans and may be isolated from a variety of clinical specimens.
C. koseri occasionally causes neonatal meningitis.