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MICROBIOLOGY
Chapter 25
Microbial Diseases of the Digestive System
Dr. Abdelraouf A. Elmanama
Ph. D Microbiology
Medical Technology Department, Faculty of Science, Islamic University-Gaza
2008
Microbial Diseases of the Digestive
System
• Transmitted in food and water
• Fecal-oral cycle can be broken by:
• Proper sewage disposal
• Disinfection of drinking water
• Proper food preparation and storage
2008
The Digestive System
2008
Figure 25.1
Normal Microbiota
• >300 species in mouth
• Large numbers in large intestine, including:
• Bacteroides
• E. coli
• Enterobacter
• Klebsiella
• Lactobacillus
• Proteus
2008
Dental Caries
2008
Figure 25.3a, b
Tooth Decay
2008
Figure 25.4
Periodontal Disease
2008
Figure 25.5
Bacterial Diseases of the Lower Digestive System
• Symptoms usually include diarrhea, gastroenteritis,
dysentery
• Treated with fluid and electrolyte replacement
• Infection caused by growth of pathogen
• Incubation from 12 hr to 2 wk
• Intoxication caused by ingestion of toxin
• Symptoms appear 1-48 hr after ingestion
2008
Staphylococcal Food Poisoning
• Staphylococcus
aureus
enterotoxin is a
superantigen
2008
Figure 25.6
Shigellosis
• Shigella spp.
producing Shiga
toxin
• Shiga toxin causes
inflammation and
bleeding
2008
Figure 25.8
Salmonellosis
• Salmonella enterica
serovars such as S.
enterica Typhimurium
• Mortality (<1%) due to
septic shock caused by
endotoxin
2008
Figure 25.9
Salmonellosis and Typhoid Fever Incidence
2008
Figure 25.10
Typhoid Fever
• Salmonella enterica Typhi
• Bacteria spread throughout body in phagocytes
• 1-3% recovered patients become carriers, harboring
Salmonella in their gallbladder
2008
Cholera
• Vibrio cholerae serotypes that produce cholera toxin
• Toxin causes host cells to secrete Cl–, HCO–, and
water
2008
Figure 25.12
Noncholera Vibrios
• Usually from contaminated crustaceans or mollusks
• V. cholerae serotypes other than O:1, O:139, and
eltor
• V. parahaemolyticus
• V. vulnificus
2008
Escherichia coli Gastroenteritis
• Occurs as traveler's diarrhea and epidemic diarrhea in
nurseries
• 50% of feedlot cattle may have enterohemorrhagic
strains in their intestines
• Enterohemorrhagic strains such as E. coli O157:H7
produce Shiga toxin
• O = cell wall antigen
• H = flagellar antigen
2008
Campylobacter Gastroenteritis
• Campylobacter jejuni
• Usually transmitted in cow's milk
2008
Helicobacter Peptic ulcer disease
• Treated with antibiotics
• H. pylori causes
stomach cancer
2008
Figure 11.11
Helicobacter Peptic ulcer disease
2008
Figure 25.13
Yersinia Gastroenteritis
• Y. enterocolitica and Y. pseudotuberculosis
• Can reproduce at 4°C
• Usually transmitted in meat and milk
2008
Clostridium perfringens Gastroenteritis
• Grow in intestinal tract producing exotoxin
2008
Bacillus cereus Gastroenteritis
• Ingestion of bacterial exotoxin produces mild symptoms
2008
Mumps
• Mumps virus
• Enters through
respiratory tract
• Infects parotid
glands
• Prevented with
MMR vaccine
2008
Figure 25.14
Hepatitis
• Inflammation of the liver
• Hepatitis may result from drug or chemical toxicity, EB
virus, CMV, or the Hepatitis viruses
2008
Hepatitis
Transmission
Causative agent
Chronic liver
disease
Vaccine
Hepatitis A
Fecal-oral
Picornaviridae
No
Inactivated virus
Hepatitis B
Parenteral, STD
Hepadnaviridae
Yes
Recombinant
Hepatitis C
Parenteral
Filoviridae
Yes
No
Hepatitis D
Pareteral, HBV
coinfection
Deltaviridae
Yes
HBV vaccine
Hepatitis E
Fecal-oral
Caliciviridae
No
No
2008
Table 25.1
Hepatitis B Virus
2008
Figure 25.15
Viral Gastroenteritis
• Rotavirus
• 3 million cases annually
• 1-2 day incubation, 1
week illness
• Norovirus
• 50% of U.S. adults have
antibodies
• 1-2 day incubation. 1-3
day illness
• Treated with rehydration
2008
Figure 25.17
Mycotoxins
• Mycotoxins are produced by some fungi:
• Claviceps purpurea
• Grows on grains
• Produces ergot
• Toxin restricts blood flow to limbs; causes
hallucination
• Aspergillus flavus
• Grows on grains
• Produces aflatoxin
• Toxin causes liver damage; liver cancer
2008
Giardiasis
• Giardia lamblia
• Transmitted by
contaminated water
• Diagnosed by
microscopic
examination of
stool for ova and
trophozoite
• Treated with
metronidazole
2008
Figure 25.18
Cryptosporidiosis
• Cryptosporidium
parvum
• Transmitted by oocysts
in contaminated water
• Diagnosed by acid-fast
staining of stool or
presence of antibodies
by FA or ELISA
• Treated with oral
rehydration
2008
Figure 25.19
Cyclospora Diarrheal Infection
• Cyclospora cayetanensis
• Transmitted by oocysts in contaminated water
• Diagnosed by microscopic examination for oocysts
• Treated with trimethoprim and sulfamethoxazole
2008
Amoebic Dysentery
• Entamoeba histolytica
• Amoeba feeds on RBCs and GI tract tissues
• Diagnosis by observing trophozoites in feces
• Treated with metronidazole
2008
Amoebic Dysentery
Figure 25.20
2008
Amoebic Dysentery
Figure 12.18b
2008
MICROBIOLOGY
Chapter 25
Microbial Diseases of the Digestive System
Dr. Abdelraouf A. Elmanama
Ph. D Microbiology
Medical Technology Department, Faculty of Science, Islamic University-Gaza
2008
Helminthic Diseases of the Digestive System
2008
Figure 25.21
Tapeworms
• Taenia spp.
• Transmitted as cysticerci
in undercooked meat
• Cysticerci may develop in
humans
• Diagnosed by observing
proglottids and eggs in
feces
• Treatment with
praziquantel
• Neurocysticercosis may
require surgery
2008
Figure 12.27
Tapeworms
2008
Figure 25.22
Hydatid Disease
• Echinococcus
granulosus
• Definitive host:
Dogs, wolves
• Intermediate host:
Sheep and other
herbivores;
Humans
• Transmitted by
ingesting E.
granulosis eggs
• Treatment is
surgical
2008
Figure 25.23
Echinococcus granulosus
2008
Figure 12.28
Pinworms
• Enterobius vermicularis
• Definitive host: Humans
• Transmitted by ingesting Enterobius eggs
• Treatment with pyrantel pamoate or mebendazole
2008
Pinworms
2008
Figure 12.29
Hookworms
• Larvae in soil hatched from eggs shed in feces
• Larvae bore through skin; migrate to intestine
• Treated with mebendazole
2008
Hookworms
2008
Figure 25.24
Hookworms
2008
Figure 12.30
Ascariasis
• Ascaris
lumbricoides
• Lives in human
intestines
• Transmitted by
ingesting Ascaris
eggs
• Treated with
mebendazole
2008
Figure 25.25
Trichinosis
• Trichinella spiralis
• Larvae encyst in
muscles of humans
and other mammals
• Transmitted by
ingesting larvae in
undercooked meat
• Treated with
mebendazole to kill
adults worms
2008
Figure 25.26
Trichinosis
Garbage,
including
undercooked
or raw pork
1 Adult Trichinella spiralis develop,
invade intestinal wall of pig, and
produce larvae that invade muscles.
Capsule
2 Section showing T.
spiralis larvae encysted
in pig’s muscle tissue
(capsule is 0.25 to 0.5 in
length).
5 Meanwhile,
other animals
are infected by
eating infected
meat that has
been dumped.
Section of T. spiralis
Undercooked pork
3 Human eats
undercooked
pork containing
cysts.
4 In human intestine, cyst
walls are removed, and
T. spiralis adults
develop. Adults
produce larvae that
encyst in muscles.
T. spiralis adult
2008
Figure 25.26