24.E: Digestive System Infections (Exercises)
24.1: Anatomy and Normal Microbiota of the Digestive System
The human digestive system, or the gastrointestinal (GI) tract, begins with the mouth and ends with the anus. The parts of the mouth include the teeth, the gums, the tongue, the oral vestibule (the space between the gums, lips, and teeth), and the oral cavity proper (the space behind the teeth and gums). Other parts of the GI tract are the pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anus.
Multiple Choice
Which of the following is NOT a way the normal microbiota of the intestine helps to prevent infection?
- It produces acids that lower the pH of the stomach.
- It speeds up the process by which microbes are flushed from the digestive tract.
- It consumes food and occupies space, outcompeting potential pathogens.
- It generates large quantities of oxygen that kill anaerobic pathogens.
- Answer
-
D
What types of microbes live in the intestines?
- Diverse species of bacteria, archaea, and fungi, especially Bacteroides and Firmicutes bacteria
- A narrow range of bacteria, especially Firmicutes
- A narrow range of bacteria and fungi, especially Bacteroides
- Archaea and fungi only
- Answer
-
A
Fill in the Blank
The part of the gastrointestinal tract with the largest natural microbiota is the _________.
- Answer
-
Large intestine or colon
Short Answer
How does the diarrhea caused by dysentery differ from other types of diarrhea?
24.2: Microbial Diseases of the Mouth and Oral Cavity
Despite the presence of saliva and the mechanical forces of chewing and eating, some microbes thrive in the mouth. These microbes can cause damage to the teeth and can cause infections that have the potential to spread beyond the mouth and sometimes throughout the body.
Multiple Choice
What pathogen is the most important contributor to biofilms in plaque?
- Staphylococcus aureus
- Streptococcus mutans
- Escherichia coli
- Clostridium difficile
- Answer
-
B
What type of organism causes thrush?
- a bacterium
- a virus
- a fungus
- a protozoan
- Answer
-
C
In mumps, what glands swell to produce the disease’s characteristic appearance?
- the sublingual glands
- the gastric glands
- the parotid glands
- the submandibular glands
- Answer
-
C
Which of the following is true of HSV-1?
- It causes oral thrush in immunocompromised patients.
- Infection is generally self-limiting.
- It is a bacterium.
- It is usually treated with amoxicillin.
- Answer
-
B
Fill in the Blank
When plaque becomes heavy and hardened, it is called dental calculus or _________.
- Answer
-
tartar
Short Answer
Why do sugary foods promote dental caries?
24.3: Bacterial Infections of the Gastrointestinal Tract
Major causes of gastrointestinal illness include Salmonella spp., Staphylococcus spp., Helicobacter pylori , Clostridium perfringens , Clostridium difficile , Bacillus cereus , and Yersinia bacteria. C. difficile is an important cause of hospital acquired infection. Vibrio cholerae causes cholera, which can be a severe diarrheal illness. Different strains of E. coli , including ETEC, EPEC, EIEC, and EHEC, cause different illnesses with varying degrees of severity.
Multiple Choice
Which type of E. coli infection can be severe with life-threatening consequences such as hemolytic uremic syndrome?
- ETEC
- EPEC
- EHEC
- EIEC
- Answer
-
C
Which species of Shigella has a type that produces Shiga toxin?
- S. boydii
- S. flexneri
- S. dysenteriae
- S. sonnei
- Answer
-
C
Which type of bacterium produces an A-B toxin?
- Salmonella
- Vibrio cholera
- ETEC
- Shigella dysenteriae
- Answer
-
B
Fill in the Blank
Antibiotic associated pseudomembranous colitis is caused by _________.
- Answer
-
Clostridium difficile
Critical Thinking
Why does use of antibiotics and/or proton pump inhibitors contribute to the development of C. difficile infections?
Why did scientists initially think it was unlikely that a bacterium caused peptic ulcers?
Does it makes a difference in treatment to know if a particular illness is caused by a bacterium (an infection) or a toxin (an intoxication)?
24.4: Viral Infections of the Gastrointestinal Tract
Common viral causes of gastroenteritis include rotaviruses, noroviruses, and astroviruses. Hepatitis may be caused by several unrelated viruses: hepatitis viruses A, B, C, D, and E. The hepatitis viruses differ in their modes of transmission, treatment, and potential for chronic infection.
Multiple Choice
Which form of hepatitisvirus can only infect an individual who is already infected with another hepatitisvirus?
- HDV
- HAV
- HBV
- HEV
- Answer
-
A
Which cause of viral gastroenteritis commonly causes projectile vomiting?
- hepatitisvirus
- Astroviruses
- Rotavirus
- Noroviruses
- Answer
-
D
Fill in the Blank
Jaundice results from a buildup of _________.
- Answer
-
bilirubin
Short Answer
Which forms of viral hepatitis are transmitted through the fecal-oral route?
Critical Thinking
Based on what you know about HBV, what are some ways that its transmission could be reduced in a health-care setting?
24.5: Protozoan Infections of the Gastrointestinal Tract
Like other microbes, protozoa are abundant in natural microbiota but can also be associated with significant illness. Gastrointestinal diseases caused by protozoa are generally associated with exposure to contaminated food and water, meaning that those without access to good sanitation are at greatest risk. Even in developed countries, infections can occur and these microbes have sometimes caused significant outbreaks from contamination of public water supplies.
Multiple Choice
Which protozoan is associated with the ability to cause severe dysentery?
- Giardia lamblia
- Cryptosporidium hominis
- Cyclospora cayetanesis
- Entamoeba histolytica
- Answer
-
D
Which protozoan has a unique appearance, with a blue halo, when viewed using ultraviolet fluorescence microscopy?
- Giardia lamblia
- Cryptosporidium hominis
- Cyclospora cayetanesis
- Entamoeba histolytica
- Answer
-
C
The micrograph shows protozoans attached to the intestinal wall of a gerbil. Based on what you know about protozoan intestinal parasites, what is it?
(credit: Dr. Stan Erlandsen, Centers for Disease Control and Prevention)
- Giardia lamblia
- Cryptosporidium hominis
- Cyclospora cayetanesis
- Entamoeba histolytica
Fill in the Blank
Chronic _________ infections cause the unique sign of disease of greasy stool and are often resistant to treatment.
- Answer
-
giardia
Short Answer
What is an O&P exam?
24.6: Helminthic Infections of the Gastrointestinal Tract
Helminths are widespread intestinal parasites. These parasites can be divided into three common groups: round-bodied worms also described as nematodes, flat-bodied worms that are segmented (also described as cestodes), and flat-bodied worms that are non-segmented (also described as trematodes). The nematodes include roundworms, pinworms, hookworms, and whipworms. Many of these parasites are so well adapted to the human host that there is little obvious disease.
Multiple Choice
What is another name for Trichuris trichiura ?
- pinworm
- whipworm
- hookworm
- ascariasis
- Answer
-
B
Which type of helminth infection can be diagnosed using tape?
- pinworm
- whipworm
- hookworm
- tapeworm
- Answer
-
A
Fill in the Blank
Liver flukes are often found in the _________ duct.
- Answer
-
bile
Short Answer
Why does the coughing up of worms play an important part in the life cycle of some helminths, such as the roundworm Ascaris lumbricoides ?
Critical Thinking
Cases of strongyloidiasis are often more severe in patients who are using corticosteroids to treat another disorder. Explain why this might occur.