Micro Bio: Chapter 25 Microbial diseases of the Digestive System

How are most microbial diseases of the digestive system transmitted?

fecal-oral cycle

Gastrointestinal tract consists of?
and accessory?

mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anus
accessory: teeth, tongue, salivary glands, liver, gallbladder and pancreas
mama & papa eat such large steaks at restaurants.

what type of microbes inhabit the stomach?

few microbes b/c it cannot survive the protein digesting gastric enzyme and acidic environment generated from the production of hydrochloric acid (HCI)

what type of microbes inhabit the small intestine?

few microbes
- food moves through it rapidly
- contains Paneth cells that are able to:
- phagocytize bacteria
- produce defensins
- produce lysozyme
the wall contains Peyer's patches

About 80 % of the immune system is located in the intestinal tract collectively called

gut-associated lymphoid tissue (GALT).

What are the two types of diseases w/i digestive system?

infection and intoxication

infection characteristics, point of entry and incubation?

- pathogen enters and grows in the GI
- delayed appearance of GI disturbance symptoms
- fever is usual
- diarrhea
the time req. for bacterial cells to grow and their products to produce symptoms ranges from 12 hours to 2 weeks.


ingestion of performed toxin
fast appearance of GI disturbance symptoms
fever is unusual
very sudden appearance (w/i a few hours)

Salmonella spp. characteristics

gram -
calculative anaerobe

What are the two diseases caused by Salmonella spp.?

Typhoid fever

Salmonellosis (Salmonella Gastroenteritis)
causative agent?

Salmonella typhimurium

Salmonellosis (Salmonella Gastroenteritis)
source of pathogen?

the GI of animals

Salmonellosis (Salmonella Gastroenteritis)
incubation time?

12-36 hours

Salmonellosis (Salmonella Gastroenteritis)

moderate fever, nausea, abdominal pain and cramps, diarrhea
patients could continue shed the pathogen for up to 6 months
estimated 1.4 million cases and 400 deaths a year

Typhoid Fever
causative agent?

Salmonella Typhi

Typhoid Fever
Source of pathogen?

feces of humans; the pathogen is not found in animals

Typhoid Fever
Incubation period?

2-3 weeks

Typhoid fever

high fever, headache, diarrhea occurs later
recovered patients could become chronic carriers even continue shed the pathogen forever
350-400 cases a year in the US

Dental carries (tooth decay)
causative agent?

is the most common infectious disease
Streptococcus mutans

Streptococcus mutans

gram positive
alpha hemolytic

dental carries/ Streptococcus mutans

begins when tooth enamel and dentin are eroded and the pulp is exposed to bacterial infection
the bacteria metabolize sugar; produce sticky products helping them adhere to the surface of teeth and also produce acids that erode the enamel
w/i minutes after

How do you prevent dental carries?

minimal ingestion of sucrose, brushing, flossing and professional cleaning to remove plaque and the use of flouride

dental carries/Streptococcus mutans

restriction of sugar in diet and regular cleaning

Periodontal disease
causative agent?

inflammation and degeneration of the gums and or the bones that support the teeth
multiple bacteria

affects what part of the body?

- the infection is limited to the gums (gingivae); bleeding while brushing the teeth
- several different bacteria are found in these such as streptococci, actinomycetes, and gram negative anaerobes

characteristics and CA?

CA: it is caused by several different bacteria; Porphyromona spp.
it is a chronic condition progressed from gingivitis
it often does not cause much discomfort
it can damage the supporting bone and tissue and lead to the loss of the teeth


the gums are inflamed and bleed easily
pus forms in pockets surrounding the teeth (periodontal pockets) which progresses toward the root tips; the bone and tissue that support the teeth are destroyed, leading eventually to loosening and loss of the teeth;

Porphyromona spp.

gram negative

Acute necrotizing ulcerative gingivitis
characteristics and CA?

aka Vincent's disease or trench mouth
- CA: Prevotella intermedia is often found in this condition and spirochetes
- more serious mouth infection
- accompanied by foul breath
- can be painful to make chewing difficult
- Oziding agents (i.e. hydrogen perox

Staphylococcal Food Poisoning (Staphylococcus Enterotoxicosis)

- leading cause of gastroenteritis
- intoxication caused by ingesting an enterotoxin produced S. aureus
- high resistant to heat
- vegetable cells can tolerate 60 C for half an hour
- resistance to drying and radiation helps them survive on skin surfaces

Staphylococcus aureus

produces several toxins that damage tissues or increase the microorganisms's virulence
produces toxin of serological type A
coagulates positive (blood plasma)
no direct pathogenic effect can be attributed to the enzyme
population of about 1 million bacter

Escherichia coli Gastroenteritis

Shiga Toxin-Producing Enterohemoryhagic E. coli
Traveler's Diarrhea
- by ETEC; EAEC Salmonella Shigella, other bacteria, viruses and protozoa

Escherichia coli Gastroenteritis
what do two different strains cause?

Enterotoxigenic: pathogenic form that is not invasive but forms an enterotoxin that produces watery diarrhea that resembles a mild form of cholera
Enteroinvasive: pathogenic form that invades the intestinal wall producing inflammation, fever, and dysenter

what does enterohemorrhagic Escherichia coli (Gastroenteritis) cause?

pathogenic form that produces Shiga toxins that cause hemorrhagic colitis resulting in very bloody stools and hemolytic uremic syndrome that results in blood in the urine and possible kidney failure

Bacteria Inhabit Most of the Digestive System

each mm. of saliva can contain billions of bacteria
b/c the stomach produces HCI and b/c food moves to rapidly through the small intestine, both of these organs have few resident microorganisms
large intestine has anaerobic Lactobacillus and Bacteroides a

Several Antimicrobial defense mechanisms in the digestive tract

high acid content in the stomach
Panted cells in small intestine phagocytize bacteria and produce antibacterial proteins called defensins and the antibacterial, enzyme and lysozyme

Dysentery signs and symptoms?

severe diarrhea accompanied by blood or mucus, can occur during infection or intoxication; also is accompanied by abdominal cramps, nausea, and vomiting


is applied to diseases causing inflammation of the stomach and intestinal mucosa

Shigellosis (Bacillary Dysentery or Traveler's Diarrhea)
causative agent?

Caused by a group of facultatively anaerobic gram negative rods of the genus Shigella
is mild to severe depending on the bacterial strain
- they invade and multiply in intestinal epithelial cells,
- Infection spreads to neighboring cells, causing tissue d


Bacteria are shed in human feces, ingested


Symptoms: include blood and mucus in the stools, abdominal cramps and fever; infections by Shigella dysenteriae result in ulceration of the intestinal mucosa
incubation: 12 hours to 2 weeks

Salmonellosis (Salmonella Gastroenteritis)
causative agent?

causative agent: Salmonella enterica serotypes
symptoms: nausea, abdominal pain and diarrhea
*septic shock can occur infants and elderly

Salmonellosis (Salmonella Gastroenteritis)

12-36 hours after eating large numbers of Salmonella

Salmonellosis (Salmonella Gastroenteritis)

eggs and poultry can be contaminated


- contagious disease
- enveloped virus, its genome is (-)ssRNA; in Paramyxovirus family
- produces painful swelling of the salivary glands (parotid glands) about 16-18 days after exposure
- transmitted through saliva and respiratory tract its portal of en


inflammation of the liver produces symptoms like a loss of appetite, malaise, fever and jaundice.

Hepatitis A virus (HAV)

enter vie the oral route
it multiplies in the epithelial cells of intestinal tract
does not lead to chronic hepatitis

Hepatitis B virus (HBV)

dsDNA genome
transmission is through the blood parenteral path, sexual contact etc
may result in chronic hepatitis and eventually lead to cirrhosis and/or live cancer

Hepatitis C virus (HCV)

(+)ssRNA genome
transmission is through parenteral path
majority results in chronic hepatitis

Viral Gastroenteritis

90% of the cases are caused by either the rotavirus or the noroviruses

most common?

dsRNA genome
transmission is through fecal oral route
the most common cause of the viral gastroenteritis


more than 90% of the children in the US have been infected by age 3.
The immunity acquired then makes rotavirus infections much less common in adults. In most cases, following an incubation period of 2-3 days, the patient suffers form low-grade fever, dia


(+)ssRNA genome
very contagious
transmission: contaminated food/water, person to person contact and aerosolized viruses


50% of adult Americans show evidence, by serum antibodies, that they have been infected. It is however, uncommon in infants.
The virus is shed in stools for 10-14 days by recovered patients and is in airborne droplets from vomitus which are infectious.

Aflatoxin Poisoning

aflatoxin is a toxin produced by a common mold
CA: Aspergillus flavus
mycotoxin is found in many foods, but it is particularly likely to be found in peanuts
this poisoning causes serious damage to livestock when their feed is contaminated with the mold.

Aflatoxin Poisoning

in humans, aflatoxin contributes to cirrhosis of the liver and cancer of the liver, particularly in India and Africa where food is subject to aflatoxin contamination


caused by Giardia lambia, a flagellated protozoan that is capable of attaching of the intestinal wall of humans and wild animals and is transmitted in contaminated water
the disease is characterized by malaise, nausea, flatulence (intestinal gas), weaknes

Amoebic Dysentery (Amoebiasis)

is spread mostly by food or water contaminated with cysts of the protozoan amoeba, Entamoeba histolytica.
Although stomach acid can destroy trophozoites, it does not affect the cysts
in the intestinal tract the cyst wall is digested away and the trophozoi

Helminthic diseases of the digestive system

helminthic parasites are very common in the human intestinal tract, especially under conditions of poor sanitation


pork tapeworm
beef tapeworm
fish tapeworm

Pork tapeworm

Taenia sodium

Beef tapeworm

Taenia saginata

Fish tapeworm

Diphyllobothrium latum

Hydatid Disease

is a helminthic disease caused by Echinococcus granulosus

Echinococcus granulosus

is one of the most dangerous tapeworm
eggs are ingested by humans (intermediate host) often through the feces of an infected dog
eggs hatch in the small intestine of humans. larvae migrate to liver or lungs; larvae develop into hydatid cysts
definitive ho

What is the definitive and intermediate hosts for Echinococcus granulosus?

intermediate hosts- humans, sheep and deer
definitive hosts- dogs and coyotes

What is a definitive host?

is an organism that harbors the adult forum (sexually reproducing stage, produce eggs) of a parasite


humans are the definitive hosts for pinworms , Enterobius vermicularis
the disease is acquired by ingesting Enteriobius eggs


Ancylostoma duodenale and Necatur americans
hookworm larvae are in the soil and bore through the human skin and migrate to the intestine to mature into adults


CA: Ascaris lumbricoides
adults live in human intestines; the disease is acquired by ingesting Ascaris eggs


CA: Trichinella spirali
larvae encyst in muscles of humans and other mammals to cause trichinosis
the roundworm is contracted by ingesting undercooked meat containing larvae
adult females mature in the intestine and lay eggs
the new larvae migrate to inva

causative agent?

urinary bladder (lower urinary tract) infection
CA: Escherichia coli
Staphylococcus saprophyticus

This is a common infection in females for 3 reasons?

there are microbes at the opening and along the length of the urethra
careless personal hygiene
sexual intercourse


primary Escherichia coli
usually a complication of a lower urinary tract infection


CA: Neisseriae gonorrhoeae
microbes attaches to mucosal cells of the oral-pharyngeal area, genitals, eyes, and rectum by means of fimbrea
symptoms: in males: painful urination and pus discharge which is not treated; can cause blockage of the urethra and s