Microorganisms and the Digestive System

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/G/GITract.html

I. Mouth

a. Teeth- dental caries- the formation of films on the surfaces of teeth – most predominant form of bacteria Streptococcus mutans. These bacteria cling to the surface of teeth and can initiate dental caries.

b. The bacterial populations that attach to teeth include other streptococci as well as Actinomyces which are filmentous bacteria.

c. While the basic environment of the mouth can encourage and promote the growth of microorganisms, there are also antimicrobial substances in the region around the teeth

d. Protection is provided by the saliva as well as by crevicular fluid, that is produced by the connection between the gums and the teeth.

e. Lysozyme is also present in this region of the mouth. Lysozyme acts to lyse or break open cells.

f. Bacteria use the sugar for metabolic processes. If lactic acid is produced it can aid in the breakdown of the enamel on the teeth.

g. Decay becomes a problem if the decay proceeds to the inner levels of the tooth. This can lead to serious infection. Dental abscesses can occur. These are normally inhabited by a variety of anaerobic bacteria. Most soft tissue infections can be treated by penicillin or its derivatives.

h. More serious than glucose is the intake of sucrose. This sugar is highly cariogenic and leads rapidly to tooth decay. It is not the sugar that is ingested during meals but the sugar ingested between meals that proves to be the greatest problem to children and teenagers.

http://news.bbc.co.uk/cbbcnews/hi/sci_tech/newsid_1825000/1825748.stm

Could genetically modified bacteria stop tooth decay. Check it out!

II. Periodontal Disease

a. Inflammation or degeneration of the structures that supports the tooth. The roots of the tooth are protected by a specialized type of connective tissue called cementum. As people age – bacteria may infiltrate into this region and cause caries in the cementum. This initiates periodontal disease.

b. If the inflammation and infection by the bacteria is limited to the gums the situation is described as gingivitis

c. Gingivitis is usually caused by streptococcus, actimomycetes, and anaerobic bacteria.

d. A chromic condition with inflammation that causes the loss of teeth is called periodontitis.

e. In this situation the gums are chronically inflamed and red. They bleed. There is bone loss as well as a destruction in the support tissue in and around the teeth.

f. This is a serious situation if the periodontal pockets and disease are not treated.

g. This can lead to acute necrotizing ulcerative gingivitis also known as trench mouth. The bacterium usually associated with this is Prevotella intermedia.

h. Treatment includes oxidizing agents, debridement, and the administration of metronidazole.

http://www.gaba.com/teeth_care/gingivitis.html

Problems with the gums and teeth

III. Bacterial Diseases of the Lower Digestive Tract

Digestive system

Microscopic View Graphic

a. An infection is when a pathogen enters the GI tract and multiplies. They are also able to pass through the GI tract and enter the blood stream through the gastric mucosa. Infections are characterized by gastrointestinal disturbances and fever.

b. Intoxication is caused by the ingestion of a preformed toxin. Most intoxications such as that caused by Staphylococcus aureus are characterized by a very sudden appearance of symptoms.

Characteristics

Gram-positive, cluster-forming coccus
nonmotile, nonsporeforming facultative anaerobe
fermentation of glucose produces mainly lactic acid
catalase-positive
coagulase-positive
golden yellow colony on agar
normal flora of humans found on nasal passages, skin and mucous membranes
pathogen of humans, causes a wide range of suppurative infections, as well as food poisoning and toxic shock syndrome

Staphylococcus aureus from a pustular exudates

c. Dysentery – results in severe diarrhea accompanied by blood and mucous. These symptoms also include abdmoninal cramps, nausea, and vomiting.

d. Gastroenteritis describes diseases that cause inflammation of the stomach and the intestinal mucosa

e. Infant diarrhea- rotaviruses, E. coli and Shigella. Dr. Paul Offit, Childrens Hospital( CHOP) Tremendous problem in developing countries. High infant mortality due to lack of medical intervention and dehydration( loss of bodily fluids)

Scenario I. Staphyloccal food poisoning.

http://vm.cfsan.fda.gov/~mow/chap3.html - Bad Bug Book

Keep hot foods hot (at or above140° F) and cold foods cold (at or below 41° F).
Do not store foods longer than four hours at room temperature.
Cool cooked foods as soon as possible using shallow, uncovered containers or covered containers vented to allow heat to escape.
Cool and reheat foods one time.
Exclude food handlers with exposed infections, such as a boil or cut on the hands, from food preparation and handling.
Touch food with bare hands as little as possible. Do not handle food with bare hands after touching your face or if you have open sores on your hands.
Wash hands with soap and water before preparing food. If you touch your face while preparing food, wash your hands handling food again.

Case Study - http://www.cdc.gov/mmwr/preview/mmwrhtml/00050415.htm

http://www.cdc.gov/epo/mmwr/preview/mmwrhtml/00000825.htm

Characteristics of Staphylococcus

· Resistant to environmental stresses

· They have vegetative cells that can tolerate fairly high temperatures

· They are resistant to dehydration and drying

· They can grow in salty meat like ham as in the case study above

The Location of Staphylococcus in the body

· They are found in the nasal passages

· They travel from the nasal passages to food because people can blow their nose or touch discarded Kleenex not realizing the potential for transfer of the microorganisms

· If these bacteria are then transferred to food at a temperature at which they can grow the food becomes contaminated. If the food is left at room temperature or warmer, the food acts as an incubator. This is referred to as temperature abuse.

· As these bacteria reproduce they can divide and produce an enterotoxin into the food. This then leads to staphylococcus intoxication.

Staphylococcus Toxins –

Serological type A – serological testing. This toxin is also associated with the property of these bacteria which is the ability to coagulate rabbit plasma – this is known as coagulase positive. The enterotoxin is heat stable and can survive up to 30 minutes of boiling once it is produced.

http://vm.cfsan.fda.gov/~ebam/bam-13a.html

A population of about 1 million bacteria may produce enough enterotoxins to cause illness.

Custards

Cream pies

Hams are examples of foods that can be contaminated with these bacteria.

Effects of the toxin.

a. Vomiting

b. Diarrhea

c. Severe abdominal cramps

d. Recovery generally within 24 hours

Scenario II. Shigellosis ( Bacillary Dysentery) . Page 694- Case Study. Read and review.

a. Severe form of diarrhea caused by a facultative anaerobe( gram – . These seem to be limited to primates

Shigella dysenteriae, S. flexneri, S boydii, and S. sonnei

b. This may be a less severe infection known as traveler’s diarrhea.

c. http://www.cdc.gov/travel/food-drink-risks.htm

Food and water precautions by the CDC for travelers.

How can I avoid traveler's diarrhea?

When you are visiting an area where the water may not be clean, you should be careful about these things:

· Do not drink tap water and do not use it to brush your teeth.

· Do not drink bottled water if the seal on the bottle has been broken.

· Do not use ice that has been made from tap water.

· Do not drink milk or eat dairy products that have not been pasteurized (heated to a temperature where all germs are killed).

· Do not eat raw fruits or vegetables unless they can be peeled and you are the one who peels them.

· Do not eat lettuce and other leafy raw vegetables (like spinach), and do not eat cut-up fruit salad.

· Do not eat raw or rare (slightly cooked) meat or fish.

· Do not eat food from people who sell food on the street.

What is safe to eat or drink?

· Soft drinks that are carbonated (drinks with a gas called carbon dioxide in them).

· Hot drinks, such as tea or coffee.

· Carbonated or noncarbonated bottled water as long as you are the one who breaks the seal on the bottle.

· Raw fruits or vegetables that can be peeled, as long as you are the one who peels them.

· Food that is served hot.

· Meat that is well cooked.

Infections

· S. sonnei. It causes a elatively mild dysentery.

· Extreme infections are caused by S. dysenteriae. This is associated with the Shiga toxin

· The infectious dose of bacteria is quite small

· These bacteria proliferate in the small intestine but the greatest damage or problem is in the region of the large intestine

· The number of cases per year in the United States is roughly 20,000-30,000..

· The antibiotic of choice is fluoroquinolines.

Scenario III. Salmonellosis – Salmonella Gastroenteritis

· Salmonella can cause a variety of diseases including gastroenteritis and enteric typhoid fever. Currently all strains of Salmonella are classified in a single species. Salmonella enterica.

· Lipopolysaccharide A and O are antigens and the Vi antigen is a virulence factor.

· Salmonella is a gram negative bacillus, produces acid and gas during the fermentation of glucose. They also produce H2S from sulfur containing amino acids( cysteine and methionine)

· Widely distributed in nature.

· Associated with eggs and poultry

· Fecal – oral transmission may occur

· Carrier status may be a problem

· Pet turtles have been found to be carriers so that having turtles as pets in many states is illegal( NJ )

Yong children and the elderly are particularly vulnerable to this infection

Pathogenesis

a. Survive the gastric juices

b. Infiltrate the lining of the small intestine and multiply

c. The bacteria are able to survive inside phagocytic cells

d. They are able to produce systemic disease

Gastroenteritis

a. Diarrhea

b. Abdominal Cramps

c. Vomiting

d. Self- limiting infection of 24-72 hours.

Enteric typhoid fever

a. Severe life threatening bacterial infection

b. Incubation period ranges from 5-21 days

c. Rash can appear on the trunk

d. Generalized feeling of malaise, fever, and discomfort

e. Complications can include intesetinal hemorrhages and endocarditis

f. Antibiotic therapy and early diagnosis can eliminate severe symptoms and mortality

g. Antibiotics include beta lactams and fluoroquinolones

The majority of the clinically useful beta-lactams belong to either the penicillin (penam) or cephalosporin (cephem) group. Moxalactam is an antibacterial that belongs to the oxacephem group which is closely related to the cephalosporins. For convenience, it is common to include it as a member of the cephalosporins because its pharmacology is so closely related to the so-called third generation cephalosporins. The beta-lactams also include the carbapenems (e.g., imipenem), the monobactams, e.g., aztreonam, and the beta-lactamase inhibitors, (e.g., clavulanic acid).

Fluoroquinolones (flu-roe-KWIN-a-lones) are used to treat bacterial infections in many different parts of the body. They work by killing bacteria or preventing their growth. However, these medicines will not work for colds, flu, or other virus infections. Fluoroquinolones may also be used for other problems as determined by your doctor. Fluoroquinolones are available only with your doctor's prescription,

Ciprofloxacin
- Oral suspension (U.S.)
- Tablets (U.S. and Canada)
Enoxacin
- Tablets (U.S.)
Gatifloxacin
- Tablets (U.S.)
Levofloxacin
- Tablets (U.S. and Canada)
Lomefloxacin
- Tablets (U.S.)
Moxifloxacin
- Tablets (U.S.)
Norfloxacin
- Tablets (U.S. and Canada)
Ofloxacin
- Tablets (U.S. and Canada)
Sparfloxacin
- Tablets (U.S.)

Parenteral

Ciprofloxacin
- Injection (U.S. and Canada)
Gatifloxacin
- Injection (U.S.)
Levofloxacin
- Injection (U.S. and Canada)
Moxifloxacin
- Injection (U.S.)
Ofloxacin
- Injection (U.S.)

Laboratory ID

a. Stool culture

b. Bacteria grown on MacConkey Agar.

Scenario IV. Campylobacter.

· Members of Campylobacter aer curved, spiral, or S- shaped. They resemble vibrios microscopically. They have a single polar flagellum. They are motile organisms.

· They are also characterized by capsular and flagellar antigens.

· They are also microaerophilic.( They need oxygen but at lower concentrations than that of air)

· Campylobacters are widely distributed in nature. They have a commensalistic relationship with many vertebrates. This means that they can inhibit the GI tract without causing disease. While humans receive no benefit from this relationship the bacteria can a residence and nutritional benefits.

· The most common route of infection is fecal-oral

· Food and water can also be contaminated.

· http://www.hawaii.gov/doh/about/press/1998/prcampy.html

· http://www.cdc.gov/ncidod/dbmd/diseaseinfo/campylobacter_g.htm

C. jejuni

· acute enteritis

· 1-7 day incubation

· Affects healthy individuals

· This disease can last days to weeks but in general is self limiting

· Symptoms can include headache, fever, mualgai and intestingal crampin and diarrhea which may or may not be bloody.

· C. jejuni may cause traveler’s diarrhea.

· Bacteremia may occur in compromised hosts or in the elderly

Diagnosis- Isolated from feces using special selective media

Catalase and oxidase positive

Disease V. Vibrio cholera

· Cholera a problem in Asia. India has outbreaks. Cholera epidemics are caused by problems with sanitations.

· Cholera is a waterborne infection. Cholera is found in brackish or low salt water that is found in estuaries or salt marshes.

· Tiny crustaceans are colonized by the bacteria as are algae and other plants.

· The causative agent of cholera is a gram negative curved rod with a polar flagellum. Its serotype O.1 causes the most frequently recognized epidemiological form. A variant of this group 139 has caused recent severe epidemics in India.

· Cholera bacteria grow in the small intestine and produce an enterotoxin that causes the secretion of electrolytes

· The appearance of stools has been characterized as rice water stools from the masses of intestinal mucus, epithelial cells, and bacteria that are released.

( chloride and bicarbonates) as well as loss of water.

· The sudden loss of electrolytes can cause collapse, organ failure, and death.

· Infections of Cholera have occurred in the Gulf Coast area .

· Cholera can be identified in selective media because they prefer alkaline environments which inhibit the growth of many other organisms

Treatment

· Vaccines may be given to children but they have a short duration

· Tetracyclines are effective antibiotics – broad spectrum – affect protein synthesis. ( activity of the ribosomal subunits in the process of translation)

· Rehydration therapy is very effective in saving lives and reducing the severity of infections

Group 1
- Tetracycline
- Oxytetracycline
Group 2
- Demeclocycline
- Methacycline
Group 3
- Doxycycline
- Minocycline

Heliobacter pylori

· Recently linked to the development of gastric ulcers

· Grows in the acidic environment of the stomach

· People with blood type O are more affected by this bacterium

· Normally people secrete a mucus type covering over the mucosa which protects it from the effects of the acid. When this is disrupted by infection, the lining may be penetrated causing an ulcer to form.

· Stomach cancer can also result

· Heliobacter causes an inflammation in the gastric mucosa. It is able to grow in this environment because it has an enzyme capable of converting urea to ammonia which is very basic. The bacteria are then able to tolerate the acidity .

· Treatment of this condition with antibiotics can effectively eliminate a high proportion of cases of gastric ulcers

· http://www.helico.com/

Disease 6 - B. cereus – Gastroenteritis

· Large, gram positive spore forming bacteria. It is very common in soil and on vegetation.

· In general it is harmless

· It has been identified as the source of foddborne infections

· Contamination can occur in foods

· Heating does not always destroy the endospores.

· The infection is primarily diarrhea

· The symptoms occur 8-16 hours after eating.

· This disease is generally self-limiting

Disease 7. Cytomegalovirus

http://www.cdc.gov/ncidod/diseases/cmv.htm

http://kidshealth.org/parent/infections/bacterial_viral/cytomegalovirus.html

http://www.thebody.com/pinf/cmv.html

http://www.health.state.ny.us/nysdoh/communicable_diseases/en/cytomega.htm

· Cytomegalovirus is a Herpes virus.

· It causes swollen lymph glands

· Once an individual is infected, the infection is for life

· Some epidemiologists estimate that more than 50 % of the people in the United States have been infected with this virus during their lifetime.

· This disease is particularly dangerous to individuals with HIV

· There is a danger of transmission of the virus to the fetus in pregnant women. Tests for immune status to this virus are available. Each year children are born with sever symptoms as a result of this infection.

· Serological tests include – Elisa and immunofluorescent antibodies

Interesting Parasites

Giardiasis

http://vm.cfsan.fda.gov/~mow/chap22.html

a. Causative agent – flagellated protozoan

b. Causes severe diarrhea and malabsorption syndrome

c. Characterized by “fatty stools”

d. Weakness

e. Weight loss

f. Flatulence

g. Metronidazole is effective treatment. ( Flagyl)

Amebiasis

Spread by water contaminated with the cysts of a protozoan Amoeba, Entamoeba histolytica
Gastric juices cannot destroy the cysts of this protozoan
Severe dysentery can occur with bleeding and mucus
The presence of this organism can be diagnosed by the Elisa or Fluorescent antibody tests