Gastrointestinal pathogens of the family Vibrionaceae: Include the following medically important genera: Vibio cholerae, Aeromonas, Campylobacter, and Helicobacter pylori.

1. Vibrionaceae
Prof. Alaa H. Al-Charrakh
Babylon University, Iraq

2. Gastrointestinal pathogens of the family
Vibrionaceae: Include the genera:
Vibrio
V. cholerae: cholera
V. parahaemolyticus: gastroenteritis
Aeromonas
A. hydrophila: gastroenteritis; wound infection
Campylobacter
C. jejuni: gastroenteritis
Helicobacter
H. pylori: gastritis; peptic ulcer; gastric cancer,
MALToma

3. Vibrio cholerae
-Gram-ve curved rod. Motile by a polar flagellum.
-Grow at a high pH (8.5- 9.0) and are rapidly killed by gastric acid.
-Oxidase-positive.
-Vibrio species inhabit marine environments, and are halophilic.

4. V. cholerae O1:
Sero-subtypes: Inaba, Ogava & Hikojima
Two biotypes of V. cholerae O1: classical and El Tor.
Hemolysin V-P test Polymixin B
classical - - sensitive
El Tor + + resistant
Antigenic structure & biological classification
O antigen: confers serological specificity.
Serogroups O1 and O139 cause cholera.

5. El Tor V. cholerae
• It was first identified in 1905 at a quarantine camp on
the Sinai Peninsula in El-Tor, Egypt. The vibrios were
found in the guts of six pilgrims returning from Mecca.

6. Cholera epidemics
- Are associated with V. cholerae O1
- None O1 V. cholerae (O139) reported
in Bangladesh in 1992
- In 2007, a lack of clean drinking water
in Iraq led to an outbreak of cholera. A
total of 181 people were infected, with 10
deaths reported. Basic water
sterilization became impossible in some
places due to restrictions on the
availability of chlorine for water
sterilization.

7. V. cholerae is pathogenic only for humans.
Mean infective dose: 108
-1010
. Gastric acid provides some
protection.
Mouth intestine attach to the microvilli of the epithelial cells
and multiply release cholera toxin.
Major virulence factors:
Toxin-coregulated pili (TCP): adherence to mucosal cells.
Enterotoxin (cholera toxin): produced by O1 and O139 strains.
Hemagglutinin-protease: releases bacteria from mucosal cells.
other enterotoxins, flagellum, siderophores.
Pathogenesis and Immunity

8. Clinical Diseases
Incubation period: 1-4 days.
-Sudden onset of nausea and vomiting, and profuse diarrhea
with abdominal cramps; "rice water" stool (containing mucus,
epithelial cells, and large numbers of vibrios)
-rapid loss of fluid and electrolytes profound dehydration
that leads to circulatory collapse (hypovolemic shock).
Carrier state seldom exceeds 3-4 weeks.
The El Tor biotype causes milder disease than the classical
biotype.
V. cholerae

9. Cholera Toxin
CT is a proteinaceous enterotoxin.
It composed of a AB subunit. The B subunit forms a
pentameric structure that binds the CT to the receptor
on the eukaryotic cells.
The A subunit contains the enzyma-tically active portion
or the toxin
Proteolytic cleavage of the A subunit results in A1 and
A2 peptide units which remain linked by a disulfide
bond.
Once the A subunit is internalized by the eukaryotic cell, the disulfide bond
is reduced.
The A1 subunit contains a ADP-ribosyltransferase which covalently modifies
the G protein, which regulates adenylate cyclase. Adenylate cyclase
mediates the formation of cAMP
The increase in cAMP levels bring about the secretion of chloride and
bicarbonate from the mucosal cells into the intestinal lumen

10. Activation of
adenyl cyclase
Activation of
adenyl cyclase
Pathogenesis of Cholera Toxin
INTESTINAL
CELL
ReceptorReceptor
+ NAD G-2-ADP-ribose + NicotinamideProtein G + NAD G-2-ADP-ribose + Nicotinamide+ NAD G-2-ADP-ribose + NicotinamideProtein G
ADP-ribosyulation of Protein G
• Subunits B facilitate entry of subunit A (Active subunit) into cell
• Subunit A cleaves nicotinamide from NAD and transfers the
remaining ADP-ribose to protein G (locked protein G)
• Activates adenyl cyclase to convert ATP to cAMP - secretions
A
A
A
A
ATP cAMP secretionsATP cAMP secretions
Locked G proteinLocked G protein
A
B
B
B
B
B B
Cholera toxin A
B
B
B
B
B B
Cholera toxin

11. Specimens: mucus flecks from stool.
Smears: Dark-field or phase contrast microscopy may show the
rapidly motile vibrios.
Culture: peptone agar, blood agar (pH near 9.0), or TCBS
(thiosulfate-citrate-bile salts-sucrose) agar. Alkaline peptone
broth can be used for enrichment.
Biochemical tests
Serological tests: slide agglutination tests using anti-O1 or
O139 antiserum.
Diagnostic lab tests

12. Growth of V. cholerae on TCBS

13. Controls:
1. Improvement of sanitation and personal hygiene.
2. Isolation of patients, and their excreta be disinfected.
3. Vaccination: in development.
Treatment
Water and electrolyte replacement - most important.
Antibiotic treatment: tetracycline or trimethoprim-
sulfamethoxazole.

14. - Halophilic
- Causes acute gastroenteritis following ingestion of contaminated
seafood (e.g., raw fish or shellfish).
Incubation period: 5-72 hours.
Symptoms: sudden onset of nausea, vomiting, abdominal cramps,
no or low grade fever, and watery (mostly) to bloody diarrhea.
V. parahaemolyticus

15. Campylobacter
Campylobacters contain pathogens for various animals, which
serve as reservoirs (Zoonotic). C. jejuni is a common cause of
diarrhea in humans.
Morphology
Small gram-negative rods with coma,
S or “gull wing" shapes.
Motile with a single polar flagellum.
C. jejuni, enteritis, and occasionally systemic invasion.

16. Campylobacter
Physiology and Structure
Microaerophilic: grows best in the presence of 5% O2 + 10%
CO2 (anaerobic jar plus gas generating pack).
Most Campylobacter pathogens can grow at 42 o
C.
Oxidase- and catalase-positive.

17. Pathogenesis and Clinical diseases
C. jejuni
Infections are acquired from ingestion of contaminated food,
particularly, poultry.
Mouth multiply in the small intestine invade the
epithelium cause inflammation presence of RBC and
WBC in the stools.
Ingestion of about 104
bacteria is usually necessary to produce
infection.

18. Pathogenesis and Clinical Diseases
C. jejuni
Acute onset of crampy abdominal pain, profuse diarrhea
that may be grossly bloody, headache, malaise, and fever.
Usually self-limited (5-8 days).
Occasionally, the bloodstream is invaded and a clinical
picture of enteric fever develop.
Guillain-Barré syndrome is an autoimmune disease of the
peripheral nervous system resulting from infection by C. jejuni
due to antigenic cross-reactivity between LPS and
glycosphingolipids of the neural tissue in the peripheral nervous
system.

19. Laboratory Diagnosis
Specimens: diarrheal stool
Smears: small, gram-negative "gull-wing" shaped rods.
Commercial kits for detection of specific antigens in the specimen.
Culture: selective media (e.g., Skirrow's medium and Camp BAP
medium, in which blood, charcoal, and antibiotics are added),
microaerophilic environment; 42 o
C for C. jejuni.
Treatment, Prevention, and Control
Replacement of lost fluid and electrolytes.
Antibiotics used for severe infections or septicemia.
Prevention: proper preparation of food; avoidance of unpasteurized
dairy products; preventing contamination of water supplies.

20. Helicobacter pylori
Spiral-shaped, gram-negative
rod.
Highly motile with polar flagella.
Grow on complex media in
microaerophilic (5% O2 and 10%
CO2 ) conditions.
Morphology and Physiology

21. Physiology of H. pylori
Grows optimally at a pH of 6.0-7.0.
Able to survive in the stomach because
1. it stays deep in the mucus layer near
the epithelial surface where physiological
pH is present;
2. it produces a potent urease, which catalyzes production
of ammonia that further neutralizes the acid;
3. It produces an acid-inhibitory protein that blocks acid
secretion from parietal cells.

22. Pathogenesis and Clinical Diseases
Present on the gastric mucosa of less than 20% of persons
under 30
increases in prevalence to 40%-60% of persons age 60.
The prevalence reaches over 80% in developing countries.
H. pylori is associated with gastritis, peptic ulcer, gastric
adenocarcinoma, gastric mucosa-associated lymphoid type
(MALT) B-cell lymphomas.
Chronic gastritis is a risk factor for gastric carcinoma.

23. Steps of ulcer formation:
Colonization of the epithelial cells (inhibit gastric acid
secretion, neutralization of gastric acid, pass through the
gastric mucus, adhere to the epithelial cells)
Localized tissue damage by urease byproducts, enzymes
(mucinase, phospholipase etc.), and cytotoxins (vacuolating
cytotoxin A)
stimulation of inflammatory response by LPS.

24. Gastric ulcer formation with H. pylori
Mucous
layer
Gastric
epithelium
Basement
membrane
Helicobacter
pylori
Mucus-secreting
cell
LUMEN OF STOMACH
Mucous
layer
Gastric
epithelium
Basement
membrane
Helicobacter
pylori
Mucus-secreting
cell
LUMEN OF STOMACH
Bacteria
invade &
multiply
Bacteria
invade &
multiply
Epithelium
destroyed by
gastric acid
Ulcer
formation
Epithelium
destroyed by
gastric acid
Ulcer
formation

25. Laboratory diagnosis
Histological examination of
gastric biopsies
Culturing biopsy specimens
Urease test is a rapid methods
for detection of H. pylori in
biopsy specimens or pure
culture.
Urea-breath test
Treatment, Prevention, and
Control
Treatment:
Bithmus plus antibiotics
Omeprazole (a proton pump
inhibitor), clarithromycin plus
ammoxicillin or metronidazole
Humans are the main reservoir.
Mechanism of transmission is
most likely oral-fecal, and
improved hygienic standards can
be helpful for prevention.