Microbiology

1. Microbial Diseases of the Digestive
System

2. Microbial Diseases of the Digestive System
• Transmitted in food and water – ingestion of
microbes or their toxins

3. The Digestive System
Figure 25.1
• GI tract:
• Mouth
• Pharynx
• Esophagus
• Stomach
• Small intestine
• Large intestine
• Accessory structures
include teeth, tongue,
salivary glands, liver,
gallbladder, pancreas

4. Bacterial Diseases of the Mouth
• Dental carries (tooth decay)
• Periodontal Disease

5. Figure 25.3a, b
Pathogen: primarily Streptococcus mutans
Symptoms: Discolored or hole in tooth enamel
Treatment: remove decayed area
Prevention: reduction of dietary sucrose
Dental Caries (Tooth Decay)

6. Figure 25.4
• Streptococcus mutans uses sucrose to form
dextran from glucose & lactic acid from fructose
plaque
Dental Caries (Tooth Decay)

7. Figure 25.5
a. Caries of the cementum & gingivitis
 caused by streptococci, actinomycetes, anaerobic
gram-negative bacteria
Periodontal Disease

8. b. Chronic gum disease (Periodontitis)
is due to inflammatory response to variety of
bacteria growing on gums
Symptoms of periodontal disease:
• bleeding gums
• Pus pockets
Treatment: remove damaged area, antibiotics
Prevention: Plaque removal
Periodontal Disease

9. Periodontal Disease
c. Acute necrotizing ulcerative gingivitis
Pathogen: Prevotella intermedia and spirochetes
Symptoms: pain chewing, halitosis
Treatment: removed damaged area; metronidazole
Prevention: brushing & flossing

10. • Staphylococcal Food Poisoning
• Shigellosis
• Salmonellosis
• Typhoid Fever
• Cholera
• Vibrio Parahaemolyticus gastroenteritis & V.
vulnificus gastroenteritis ( Non-cholera Vibrios)
• Escherichia coli Gastroenteritis
Bacterial Diseases of the Lower Digestive System

11. Bacterial Diseases of the Lower Digestive System
• Helicobacter Peptic ulcer disease
• Helicobacter pylori Peptic ulcer disease
• Yersinia Gastroenteritis
• Clostridium perfringens Gastroenteritis
• Clostridium difficile-Associated Diarrhea
• Bacillus cereus Gastroentiritis

12. Staphylococcal Food Poisoning (Staphylococcal
Enterotoxicosis)
Figure 25.6
 Caused by ingestion of
enterotoxin in improperly
stored foods (room temp)
Pathogen:
Staphylococcus aereus
Source: foods w/ high
osmotic pressure & those not
cooked immediately before
consumption

13. Shigellosis (Bacillary Dysentery)
Figure 25.8
Pathogen:
• Shigella spp.
producing Shiga toxin
Symptoms:
• blood & mucus in
stools
• Abdominal cramps
• & fever
S. dysenteriae
 causes ulceration of
the intestinal mucosa
Treatment: quinolones

14. Invasion of
epithelial cell of
intestinal wall
by Shigella (4
spp.) bacterium.
Blood and
mucus in stools,
abdominal
cramps, fever
Similar to
invasion by
Salmonella
bacteria

15. Salmonellosis (Salmonella Gastroenteritis)
Figure 25.9
Pathogen:
• Salmonella enterica serovars
such as S. enterica
Typhimurium
Symptoms:
• Nausea, abdominal pain,
diarrhea 12 – 36 hours after
eating
• Possible fever
• Septic shock can occur in
the infants & elderly
Treatment:
• Oral rehydration

16. Pathogen:
• Salmonella typhi – transmitted by human feces
Symptoms
• High fever and malaise after 2-week incubation,
lasts 2 – 3 weeks
 S. typhi is harbored in the gall bladder of carrier
Treatment:
Quinolones, cephalosporins
Typhoid Fever

17. Cholera
Figure 25.12
Pathogen
• Vibrio cholerae 0:1 & 0:139
Symptoms:
• vomiting and diarrhea dehydration
Incubation
~ 3 days, untreated results in 50% mortality
Treatment:
Rehydration, doxycycline

18. Pathogen:
V. parahaemolyticus
Source:
• Usually from contaminated crustaceans or
mollusks
Symptoms:
Cholera-like diarrhea, but generally milder
Treatment: rehydration; antibiotics
Vibrio parahaemolyticus gastroenteritis

19. V. vulnificus gastroenteritis
• Pathogen: V. vulnificus
• Symptoms: rapidly spreading tissue destruction
• Treatment: antibiotics

20. Pathogens:
• enterotoxigenic or enteroinvasive strains of E.
coli- cause traveler’s diarrhea
• Enterohemorrhagic strains such as E. coli
O157:H7 - produce Shiga toxin that causes
inflammation and bleeding of colon (colitis)
• Can affect kidneys to cause hemolytic uremic
syndrome
Escherichia coli Gastroenteritis

21. Pathogen:
Campylobacter jejuni
Usually transmitted in cow's milk
Symptoms:
Fever, abdominal pain, diarrhea
Treatment: none
Campylobacter Gastroenteritis

22. Helicobacter Peptic ulcer disease
Pathogen:
Helicobacter pylori-
cause stomach cancer
Symptom:
Peptic ulcer
Treatment
• antibiotics and
bismuth
Figure 11.11

23. Helicobacter pylori Peptic ulcer disease
Figure 25.13

24. Pathogen:
Y. enterocolitica
Can reproduce at 4°C (refrigerated foods)
Usually transmitted in meat and milk
Symptoms:
• abdominal pain and diarrhea, usually mild;
• maybe confused with appendicitis
Treatment:
Oral rehydration
Yersinia Gastroenteritis

25. Self-limiting gastroenteritis
• Pathogen: Clostridium perfringens
• Endospores survive heating and germinate
when foods (meat) stored at room temperature
• Grow in intestinal tract producing exotoxin
• Symptom: diarrhea
• Treatment: oral rehydration
Clostridium perfringens Gastroenteritis

26. Clostridium difficile-Associated Diarrhea
• Pathogen: Clostridium difficile
• Symptoms: mild diarrhea to colitis
The condition is usually associated with
hospitalized patients & nursing home residents
• Treatment: metronidazole, vancomycin

27. Due to ingestion of food contaminated with soil
saprophyte Bacillus cereus
• Pathogen: Bacillus cereus
• Symptoms: diarrhea, nausea, vomiting
• Treatment: none
Bacillus cereus Gastroenteritis

28. Viral Diseases of the Digestive System
• Mumps
• Hepatitis ( A, B, C, D, E)
• Viral Gastroenteritis

29. Mumps
Figure 25.14
Pathogen: mumps virus,
paramyxoviridae
Symptoms
• inflammation of parotid
glands, fever, pain
during swallowing
Prevention:
• MMR (measles, mumps,
rubella) vaccine

30.  Inflammation of the liver
Symptoms
• loss of appetite,
• malaise,
• fever,
• jaundice
Cause:
• drug or chemical toxicity,
• EB (Epstein-Barr) virus,
• CMV (cytomegalovirus),
• or the Hepatitis viruses
Hepatitis

31. Hepatitis (A, B, C, D, E)
1. Hepatitis A
• Pathogen: Hepatitis A virus, Picornaviridae
• Symptoms: mostly subclinical; fever, headache; in
malaise, jaundice in severe cases; no chronic
disease
• Method of transmission: Ingestion
• Vaccine: Inactivated virus, Postexposure immune
globulin

32. Hepatitis (A, B, C, D, E)
2. Hepatitis B
Frequently serious, unlike HAV which is
subclinical
Pathogen: Hepatitis B virus, Hepadnaviridae
Symptoms:
• Frequently subclinical; similar to HAV but no
headache;
• more likely to progress to severe liver damage;
• chronic disease occurs
Method of transmission: parenteral (blood
transfusions, syringes), saliva, sweat, breast milk ,
sexual contact

33. Hepatitis B Virus
Figure 25.15

34. Hepa B Virus

35. Hepatitis (A, B, C, D, E)
3. Hepatitis C –
• Pathogen: Hepatitis C virus, Flaviviradae
• Symptoms: Similar to HBV, more likely to
become chronic
• Method of transmission: Parenteral
• vaccine: none

36. Effects of Hepatitis C on human liver

37. Hepatitis (A, B, C, D, E)
4. Hepatitis D (Delta)
Pathogen: Hepatitis D virus, Delta viridae
Circular strand of RNA
Uses HBSAg as a coat
Symptoms:
• severe liver damage; high mortality rate
• chronic disease may occur
Method of transmission:
Parenteral; requires co-infection w/ Hepatitis B
Vaccine: HBV

38. Hepatitis (A, B, C, D, E)
5. Hepatitis E
Pathogen: Hepatitis E virus, Caliciviridae
Symptoms:
• Similar to HAV, but pregnant women may have
mortality
• No chronic disease
Method of transmission: ingestion
Vaccine: HAV vaccine

39. Hepatitis (A, B, C, D, E)
Table 25.1
Transmission Causative
agent
Chronic
liver
disease
Vaccine
Hepatitis A Fecal-oral Picornaviridae No Inactivated
virus
Hepatitis B Parenteral,
STD
Hepadnavirida
e
Yes Recombinant
Hepatitis C Parenteral Filoviridae Yes No
Hepatitis D Parenteral,
HBV
coinfection
Deltaviridae Yes HBV vaccine
Hepatitis E Fecal-oral Caliciviridae No HAV vaccine

40. Viral Gastroenteritis
Pathogens:
• Rotavirus (wheel shape –
Norwalk or norovirus family)
Symptoms: vomiting, diarrhea
for 1 week
• Norovirus
Symptoms: vomiting, diarrhea
for 2-3 days
Treatment
oral rehydration
Figure 25.17

41. Fungal Diseases of the Digestive System
Cause : Mycotoxin – can affect the blood, nervous
system,
kidneys or liver
Examples of Fungal Diseases of the Digestive
System
1. Ergot poisoning (Ergotism)
Pathogen: Claviceps purpurea- grows on cereal grains
Symptoms: restricted blood flow to limbs, hallucination
Treatment: none
2. Aflatoxin poisoning
Pathogen: Aspergillus flavus -grows on peanuts

42. Protozoan Diseases of the Digestive System
• Giardiasis
• Cryptosporidiosis
• Cyclospora Diarrheal Infection
• Amoebic Dysentery (Amoebiasis)

43. Giardiasis
Figure 25.18
Pathogen:
 Giardia lamblia
Method of transmission:
 ingestion of
contaminated water
Symptoms:
Malaise, nausea, flatulence,
weakness, weight loss, &
abdominal cramps, char.
Odor of H2S in the breath &
stools
Treatment:
metronidazole

44. Cryptosporidiosis
Figure 25.19
Pathogen:
• Cryptosporidium hominis
Method of transmission:
• Ingestion of water
contaminated oocysts of
C.h.
Symptoms:
• Self-limiting diarrhea but
may be life threatening in
immuno-suppressed
individuals
Treatment:

45. Pathogen:
Cyclospora cayetanensis
Symptoms:
watery diarrhea
Treatment:
trimethoprim and sulfamethoxazole
Cyclospora Diarrheal Infection

46. Amoebic Dysentery (Amoebiasis)
Pathogen:
• Entamoeba histolytica
Symptoms:
• lysing of epithelial cells
• abscesses
Treatment
metronidazole

47. Amoebic Dysentery – flask-shaped ulcer
Figure 25.20

48. Amoebic Dysentery
Figure 12.18b

49. Helminthic Diseases of the Digestive System
• Tapeworms
• Hydatid Disease
• Nematodes(Pinworms, Hookworms, Ascariasis,
Trichinellosis)

50. Tapeworms
Figure 12.27
Pathogen:
Taenia spp.
• Taenia saginata (beef
Tapeworm)
• T. solium (pork
tapeworm)
• Diphyllobothrium
latum (fish tapeworm)
Treatment: praziquantel
Neurocysticercosis (pork
tapeworm larvae) may
require surgery

51. Tapeworms – cysticerci can occur in many tissues
Figure 25.22

52. Hydatid Disease
Figure 25.23
Pathogen:
Echinococcus granulosus
tapeworm
Definitive host: Dogs,
wolves
Intermediate host: Sheep
and other herbivores;
Humans
Method of transmission
Ingestion of E. granulosis
eggs
Treatment: surgical;

53. Echinococcus granulosus
Figure 12.28

54. Nematodes: Pinworms
Pathogen: Enterobius vermicularis
Symptom: Itching around the anus
• Definitive host: Humans
• Method of Transmission: ingestion Enterobius eggs
• Treatment: pyrantel pamoate or mebendazole

55. Pinworms
Figure 12.29

56. Hookworms
Pathogen: Necator americanus, Ancyclostoma
duodenale
Symptom: large infections may result to anemia
Treatment: mebendazole

57. Ancylostoma Hookworms
Figure 25.24

58. Hookworms
Figure 12.30

59. Ascariasis
Figure 25.25
Pathogen:
• Ascaris lumbricoides
Method of
transmission
• by ingesting Ascaris
eggs
Treatment:
mebendazole

60. Trichinellosis
Figure 25.26
Pathogen:
Trichinella spiralis
• Larvae encyst in muscles of humans
and other mammals
Method of transmission:
ingestion of larvae in undercooked
meat
Symptoms:
fever, swelling around the eyes, &
gastrointestinal upset
Treatment: mebendazole;
corticosteroid

61. Trichinellosis – Trichinella spiralis
Figure 25.26
Adult Trichinella spiralis develop,
invade intestinal wall of pig, and
produce larvae that invade muscles.
Section showing T.
spiralis larvae encysted
in pig’s muscle tissue
(capsule is 0.25 to 0.5 in
length).
Human eats
undercooked
pork containing
cysts.
1
2
3
In human intestine, cyst
walls are removed, and
T. spiralis adults
develop. Adults
produce larvae that
encyst in muscles.
4
Meanwhile,
other animals
are infected by
eating infected
meat that has
been dumped.
5
Capsule
Section of T. spiralis
Undercooked pork
Garbage,
including
undercooked
or raw pork
T. spiralis adult