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24.E: Digestive System Infections (Exercises)

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    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?

    1. It produces acids that lower the pH of the stomach.
    2. It speeds up the process by which microbes are flushed from the digestive tract.
    3. It consumes food and occupies space, outcompeting potential pathogens.
    4. It generates large quantities of oxygen that kill anaerobic pathogens.
    Answer

    D

    What types of microbes live in the intestines?

    1. Diverse species of bacteria, archaea, and fungi, especially Bacteroides and Firmicutes bacteria
    2. A narrow range of bacteria, especially Firmicutes
    3. A narrow range of bacteria and fungi, especially Bacteroides
    4. 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?

    1. Staphylococcus aureus
    2. Streptococcus mutans
    3. Escherichia coli
    4. Clostridium difficile
    Answer

    B

    What type of organism causes thrush?

    1. a bacterium
    2. a virus
    3. a fungus
    4. a protozoan
    Answer

    C

    In mumps, what glands swell to produce the disease’s characteristic appearance?

    1. the sublingual glands
    2. the gastric glands
    3. the parotid glands
    4. the submandibular glands
    Answer

    C

    Which of the following is true of HSV-1?

    1. It causes oral thrush in immunocompromised patients.
    2. Infection is generally self-limiting.
    3. It is a bacterium.
    4. 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?

    1. ETEC
    2. EPEC
    3. EHEC
    4. EIEC
    Answer

    C

    Which species of Shigella has a type that produces Shiga toxin?

    1. S. boydii
    2. S. flexneri
    3. S. dysenteriae
    4. S. sonnei
    Answer

    C

    Which type of bacterium produces an A-B toxin?

    1. Salmonella
    2. Vibrio cholera
    3. ETEC
    4. 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?

    1. HDV
    2. HAV
    3. HBV
    4. HEV
    Answer

    A

    Which cause of viral gastroenteritis commonly causes projectile vomiting?

    1. hepatitisvirus
    2. Astroviruses
    3. Rotavirus
    4. 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?

    1. Giardia lamblia
    2. Cryptosporidium hominis
    3. Cyclospora cayetanesis
    4. Entamoeba histolytica
    Answer

    D

    Which protozoan has a unique appearance, with a blue halo, when viewed using ultraviolet fluorescence microscopy?

    1. Giardia lamblia
    2. Cryptosporidium hominis
    3. Cyclospora cayetanesis
    4. 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?

    Micrograph of kite-shaped cells with tails

    (credit: Dr. Stan Erlandsen, Centers for Disease Control and Prevention)

    1. Giardia lamblia
    2. Cryptosporidium hominis
    3. Cyclospora cayetanesis
    4. 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?

    1. pinworm
    2. whipworm
    3. hookworm
    4. ascariasis
    Answer

    B

    Which type of helminth infection can be diagnosed using tape?

    1. pinworm
    2. whipworm
    3. hookworm
    4. 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.

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