This document provides information on members of the Enterobacteriaceae family of bacteria. It discusses their characteristics such as being gram-negative rods that are facultative anaerobes and oxidase-negative. It describes diseases caused by different genera including gastrointestinal illnesses caused by E. coli, Salmonella, Shigella, and Yersinia. It also discusses opportunistic infections caused by Citrobacter, Enterobacter, Klebsiella and others. Identification, serotyping, antibiotic resistance patterns of isolates from Libya, and control measures are summarized for key pathogens such as E. coli, Salmonella, Shigella.

1. ENTEROBACTERIACEAE
Prof. Khalifa Sifaw Ghenghesh

2. •
•
•
•
Gram-negative rods
Facultative anaerobes
Oxidase-negative
Most members are motile

3. • Gastrointestinal diseases
(Diarrhoea and Dysentery)
–
–
–
–
Escherichia coli (Lac+)
Salmonella (Lac-)
Shigella (Lac-)
Yersinia entercolitica (Lac-)

4. Salmonella
E. coli

5. • Opportunistic diseases
–
–
–
–
•
•
•
•
•
•
•
•
•
septicemia,
pneumonia,
meningitis
urinary tract infections
Citrobacter
Enterobacter
Escherichia
Hafnia
Klebsiella
Morganella
Proteus
Providencia
Serratia

7. IDENTIFICATION
• In Stool:
– E. coli
• lactose positive
• not usually identified
• Common in healthy intestine
– Shigella, Salmonella,Yersinia
• lactose negative
• identified
• Other sites:
– identified biochemically

8. SEROTYPING
• Reference laboratory:
– antigens
• O (lipopolysaccharide)
• H (flagellar)
• K (capsular)

9. Escherichia coli

10. • Enteropathogenic E. coli (EPEC):
– Adhere to surface of mucosal cells inducing dramatic alteration on
microvilli and the rearrangement of the host cell actin cytoskeleton.
– Adhesion is medicated by two genes:
• A Plasmid-encoded gene (bfpA), responsible for the formation
of the bundle forming pilus.
• A chromosomal-mediated gene (eae) coding for the adhesion
intimin.
•
•
•
•
•
fever
diarrhea
vomiting
nausea
non-bloody stools

11. • Enterotoxigenic E. coli (ETEC):
– Cholera-like diarrhoea
– milder
– Travellers diarrhoea
• Heat labile toxin (LT)
–
–
–
–
like choleragen (Cholera toxin)
activate enterocyte adenyl cyclase
cyclic AMP
chloride and water secretion >>Diarrhea
• Heat stable toxin (ST)
– activate enterocyte guanylate cyclase
– cyclic GMP
– Chloride and water secretion >> Diarrhea

12. • Enteroinvasive E. coli (EIEC):
– Dysentery
– resembles shigellosis

13. • Enterohemorrhagic E. coli (EHEC):
– Usually O157:H7
– Meat
• Hemorrhagic
– bloody, copious diarrhea
– few leukocytes
– afebrile
• Hemolytic-uremic syndrome
– hemolytic anemia
– thrombocytopenia (low platelets)
– kidney failure
• Vero toxin (Shiga-like):
– 2 toxins: SLTI and SLTII (coded by sxt1 and sxt2)

14. TREATMENT
• Gastrointestinal disease:
– Fluid replacement
– Antibiotics
• not used usually unless systemic
–e.g. hemolytic-uremia syndrome
• UTIs:
– Antibiotic Sensitivity Is Necessary.

15. Resistance of Escherichia coli isolated from
urinary tract infections in Benghazi to antibiotics.
------------------------------------------------------------------------------------Hospital
Community
Antibiotic
acquired
acquired
(n=62)
(n=148)
------------------------------------------------------------------------------------Ampicillin
52(84)*
111(75)
Carbenicillin
53(85)
117(79)
Cephaloridine
22(35)
53(36)
Chloramphenicol
37(60)
67(45)
Gentamicin
19(31)
27(18)
Nalidixic acid
3(5)
15(10)
Nitrofurantoin
4(6)
10(7)
Tetracycline
45(73)
121(82)
Trimethoprim
52(84)
120(81)
sulphamethoxazole
*(%)
-------------------------------------------------------------------------------------

16. Shigella

17. • Bacillary Dysentery
• Shigellosis
– bloody faeces
– intestinal pain
– pus
•
•
•
•
•
4 Major O Antigenic Groups:
Serogroup A = Sh. dysenteriae
Serogroup B = Sh. flexneri
Serogroup C = Sh. boydii
Serogroup D = Sh. sonnei
• No H-Antigens.

18. Shiga Toxin
• enterotoxic
• cytotoxic
• inhibits protein synthesis
– lysing 28S rRNA

19. • The Organism Survive
the Passage Through the GIT.
>> Due to O Antigen
• Attach to Colonic Cells.
• Penetrate the Epithelial
Cells.
• Multiply Inside
• Pass to Another Cell.
>>
>>
"Invasiveness"
"Inflamation, Cell Death,
Ulceration, Impaired
Colonic Fluid Absorbtion
and a Discharge of
Blood, Mucus and Pus"

20. • Man only "reservoir"
• Mostly young children
– fecal to oral contact
– children to adults
• Transmitted by adult food handlers
– unwashed hands

21. Treating Shigellosis
• Manage dehydration
• Patients respond to antibiotics
– disease duration diminished

22. CONTROL
– Adequate Sanitization.
– Detection and Treatment of Carriers.
– Carriers Should Not Be Allowed to Handle
Food.
– Proper Sewage Disposal and Chlorination
of Water.
– FLIES >>>>>>>>>>>>>>>>

23. Information about Libyan children with diarrhea
and their Shigella isolates
Patient Sex
Age
(Mo)
Month of Length of Episode Species and
occurrence diarrhea
per day
serotype of
(days)
Shigella
-------------------------------------------------------------------------------------------------------1.
F
11
Sep
1
5
S. sonnei
2.
F
30
Sep
2
3
S. flexneri type2
3.
M
27
Oct
1
6
S. sonnei
4.
F
18
Oct
1
8
S. flexneri type2
5.
F
36
Oct
2
5-7
S. flexneri type2
6.
M
7
Dec
7
7-8
S. flexneri type1
7.
M
7
Apr
1
10
S. flexneri type2
8.
M
13
Jun
10
6-7 S. flexneri type3
9.
M
32
Jul
1
4
S. sonnei

24. Information about Libyan children with diarrhea
and their Shigella isolates
Patient
Faeces with
Mucus
Blood
Presence of
Fever
Vomiting
Species and
serotype of
Shigella
--------------------------------------------------------------------------------------------------------------------1.
+
+
--S. sonnei
2.
----S. flexneri type2
3.
--+
-S. sonnei
4.
----S. flexneri type2
5.
+
+
+
-S. flexneri type2
6.
--+
-S. flexneri type1
7.
+
+
+
+
S. flexneri type2
8.
+
+
+
+
S. flexneri type3
9.
+
+
+
+
S. sonnei

25. Salmonella

26. • More than 2000 antigenic types
(Serotypes).
– Salmonella Typhi
– Salm. Enteritidis
– Salm. Cholera-suis
– Salm. Typhimurium
• Genetically single species
– Salmonella enterica
• Salm. enterica serotype Typhi
ANTIGENIC STRUCTURE:
– O & H Antigens >>> Serotyping.
– Vi-Antigen (protective) >>> Salm. Typhi.

27. CLINICAL INFECTION AND PATHOGENSIS
1. S. Typhi, S. Paratyphi A and B:
– Gastroenteritis, bacteremia and typhoid fever.
– Typhoid Fever (Enteric fever):
•
Fever, headache, diarrhoea, and abdominal pain.
– Human Carriers Are the Only Source of
Infection.
– Transmission:
• contaminated food
• water supply
• poor sanitary conditions
– Mortality Rate:
– Relapse:

28. 2. S. Enteritidis, S. Typhimurium, etc..
– Salmonellosis:
• Self-limiting gastroenteritis with fever for <2 days
and diarrhoea < 7 days.
– Source:
• poultry, eggs
• no human reservoir
– Transmission:
– Pets:

29. • TREARMENT:
– Supportive Therapy and Maintaining Fluid and
Electrolyte Balance.
– Enteric Fever or Septicaemia:
• Antibiotics
– essential
– Carriers of Salm. typhi:
• CONTROL:
– Carriers:
– Food Cooked Properly
– Water Standards Be Observed.

30. Salmonella Serotypes Isolated from Diarrhoeic
Faeces in Tripoli (1975-1980)
– S. Wien
– S. Muenchen
– S. Typhimurium
Salmonella Serotypes Isolated from Children with
Diarrhoea in Tripoli (1992-1993)
– S. Saintpaul
– S. Muenchen
Salmonella Serotypes Isolated from Children with
Diarrhoea in Zliten (2000-2001)
– S. Heidelberg
– S. Enteritidis

31. Reistance of Salmonella species isolated from children
with diarrhoea in Zliten (2000-2001) to antibiotics
________________________________________________
Antibiotic
No. (%) resistant:
(n=23)
--------------------------------------------------------------------------------Ampicillin
23 (100)
Amoxicillin+calvulanic acid
22 (95.7)
Cefoxitin
20 (87)
Gentamicin
18 (78.3)
Doxycycline
21 (91.3)
Chloramphenicol
22 (95.7)
Nalidixic acid
1 (4.3)
Norfloxacin
0 (0.0)
Trimethoprim-sulphamehtoxazole
1 (4.3)
________________________________________________

32. • Department e-mail = dmi.ly
• Khalifa Sifaw Ghenghesh e-mail =
ghenghesh_micro@yahoo.com