Microbiology - Problem Drill 21: Microbial Diseases of the Digestive System

Transcription

1 Microbiology - Problem Drill 21: Microbial Diseases of the Digestive System No. 1 of Which of the following organs is not part of the gastrointestinal tract (GI)? (A) Esophagus (B) Small intestine (C) Stomach (D) None of the above Remember the accessory digestive organs are involved in the grinding of nutrients or secretion of digestive enzymes. Remember the accessory digestive organs are involved in the grinding of nutrients or secretion of digestive enzymes. Remember the accessory digestive organs are involved in the grinding of nutrients or secretion of digestive enzymes. D. Correct! All of these listed are part of the GI system. They all have a membranous covering called the peritoneum surrounding the organs. The GI tract is a long tube lined by a mucous membrane includes the: mouth, esophagus, stomach, small intestine, large intestine, rectum and anus. The mouth is part of the GI tract while teeth and tongue are part of the accessory digestive organs.

2 No. 2 of Which of the following answers best defines microbial antagonism? (A) Immune system fighting microbes referred to as microbial antagonism. (B) One colonizing bacteria inhibits another type of bacteria from growth in the same area. (C) A negative response by an organ or tissue to microbe growth. (D) The effect that antimicrobials such as antibiotics have on microbe growth. An immune response is an antibody against bacteria. B. Correct! One microbe colonizes an area preventing another type from growing there. These types of responses can be immunological and include inflammation. Antimicrobials (which can include antibiotics) are antagonistic to bacteria but are not describes as microbial antagonistics. Normal microbes grow within various sections of the digestive system. These microbes do not usually cause disease, at least in individuals with a normal immune system. The natural microbiota actually helps the body by providing vitamins, intestinal gases and additional digestion of nutrients. The presence of these helpful bacteria keeps pathogenic bacteria from growing in the same area which is referred to as microbial antagonism. Naturally occurring microbes can actually produce substance that make their local environment difficult for the growth of specific pathogens.

3 No. 3 of The cause of caries is best described by which of the following? (A) Biofilm formation (B) Acid production by bacteria on the tooth (C) Breakdown of the gum i.e. gingivitis (D) Plaque build up S. mutans does form a biofilm which is called plaque. However the formation of plaque does not in and of itself cause cavities. B. Correct! Yes, bacteria that grow in / plaque produce acid as a by product. This acid dissolves the enamel of a tooth. Gingivitis is the inflammation of the gum around a tooth. Inflammation is caused by the presence of bacteria. Plaque is another word for the biofilm caused by S. mutans. The plaque itself does not cause cavities. Caries is another word for a tooth cavity. A cavity is caused by the acid that is produced when bacteria replicate on the surface of a tooth. The bacteria live on the biofilm commonly referred to as plaque.

4 No. 4 of Which of the following is not a function of the body s natural microbiota? (A) Make vitamins: B12, folic acid and others. (B) Take advantage of the host when the opportunity arises. (C) Help digest nutrients. (D) Keep pathogenic bacteria from colonizing the same sites: microbial antagonism. Intestinal microbes will make vitamins. B. Correct! Natural microbiota may grow out of control in an immuno compromised individual however that is not one of their functions. The microbes will help breakdown nutrients. About 40% of the volume in feces is bacterial. Microbial antagonism is one of the objectives of natural microbiota. A host with a weakened immune system may have an uncontrolled growth of the natural microbiota. However this is not one of the purposes.

5 No. 5 of Which microbial group contributes the largest number of digestive tract diseases in the US? (A) Bacteria (B) Helminths (C) Protozoa (D) Viruses A. Correct! Bacteria are responsible for the majority of digestive diseases caused by microbes. In the US helminth infection is infrequent compared to bacteria or virus. Less then 10%. Viruses cause 30 to 40% of cases of infectious diarrhea in the U.S. Bacteria are responsible for the majority of digestive diseases caused by microbes

6 No. 6 of Typhoid fever is caused by a genus of bacteria that also causes. (A) Cholera (B) Cryptosporidiosis (C) Traveler s Diarrhea (D) Salmonellosis Cholera is caused by the genus Vibrio. Cryptosporidiosis is caused by the genus. Traveler s diarrhea is caused by E. coli. D. Correct! Correct Typhoid fever is caused by the bacterium Salmonella. Salmonellosis is an infection with Salmonella bacteria usually caused by what is known as Non-Typhoidal Salmonella

7 No. 7 of The digestive system has its own naturally occurring microbiota. With respect to the normal microbiota of the digestive system, which of the following statements is false? (A) Tongue and teeth have microbes numbering in the millions per milliliter. (B) The most common oral microbe is streptococcus. (C) The lower intestine and colon have bacteria in the billions per milliliter. (D) None of the above This statement is true; there are millions of microbes per milliliter of solution. This statement is true. The most common oral microbe is streptococcus. The lower intestine and colon have billions of bacteria per milliliter, this statement is correct. D. Correct! All of the statements presented are true. Therefore this is the only correct answer. The esophagus stomach and duodenum have almost no naturally occurring microbiota. The mouth and pharynx have microbes that number in the millions per milliliter. Microbiota in the lower small intestine and colon contain billions of microbes. Most of the bacteria in the lower small intestine and colon are of the genus Bacteroides followed in predominance by Gram-positive Lactobacillus and facultative enterobacteria such as Escherichia and Klebsiella. Fungi such as the yeast Candida and the protozoa Entamoeba also live in the colon. The normal intestinal microbiota eats the partially digested contents of the colon. The mucous membrane that lines the GI tract keeps the microbes from getting into the body.

8 No. 8 of Guillain-Barre syndrome is associated with Campylobacter is characterized by and. (A) Rash and fever (B) Nerve inflammation and bilateral paralysis (C) Rash and paralysis (D) Unilateral paralysis and nerve inflammation Rash is not associated with Guillian-Barre syndrome associated with Campylobacter. B. Correct! Bilateral paralysis and nerve inflammation is associated with Guillian Barre syndrome. Rash is not associated with Guillian-Barre syndrome associated with Campylobacter. Bilateral paralysis and nerve inflammation is associated with Guillian Barre syndrome not unilateral. Guillain-Barre syndrome is an auto immune disease which can be triggered in multiple ways. It is considered an acute disease that is associated with fever and nerve inflammation. It can cause bilateral weakness and paralysis. In the most extreme cases paralysis of the legs or feet will result.

9 No. 9 of Which of the following statements with respect to Hemolytic uremic syndrome associated with the E. coli pathogen O157:H7 is incorrect? (A) It may result in kidney damage. (B) It s associated with bloody diarrhea. (C) It has low platelet counts is evident. (D) Antibiotics are recommended to kill the E. coli bacterium. HUS leads to kidney failure. O157:H7 is associated with bloody diarrhea. Broken platelets result in low platelet counts, hemolytic anemia. D. Correct! CDC does not recommend use of antibiotics to treat this infection at this time. Hemolytic uremic syndrome (HUS) affects about 5-10% of infected people infected with E. coli O157:H7. HUS leads to kidney failure. Red blood cells are destroyed plugging the small vessels of the kidney resulting in tissue damage and death. The broken platelets result in low platelet counts (hemolytic anemia). The end result is acute renal failure. Bloody diarrhea is a symptom associated with the infection as well. Most people recover without antibiotics in 5 to 10 days. CDC does not recommend use of antibiotics to treat this infection. The presence of antibiotics may induce the bacteriophage to become induced. There is some evidence that antibiotics may increase the chance of kidney complications. Antidiarrheal agents and fluids should however be used.

10 No. 10 of Why do diets high in sugar and starches have increased risk of tooth decay? (A) They are converted into acids by bacteria. The acid breaks down the tooth enamel. (B) They are acidic and destroys the tooth s enamel. (C) They are converted into acids by bacteria which destroy the gingiva. (D) They are acidic and destroys the gingiva. A. Correct! Bacteria on tooth use sugars and starches making acid as a byproduct. The acid breaks down the tooth enamel. The sugar and starches do not by themselves breakdown the tooth enamel. A person can have gingivitis and not have tooth decay. Breakdown of the gingival does not necessarily lead to tooth decay. Cavity formation or caries begins by S. mutans (a viridans strep) making a biofilm (plaque) on a tooth. Bacteria growing on the tooth s surface make acid which then destroys the enamel. Eventually the hole enlarges to such an extent that bacteria can enter the dentin and pulp. The secretions of the bacteria untreated can destroy the nerve of the tooth and the blood vessels leading to loss of the tooth.