Published on March 3, 2016
1. Microbiology Report: Digestive System Presentation By: Jess Christian B. Pacot Vin Myco Calang
2. Microbial Diseases of the Digestive System ● Microbial diseases that affects our Digestive System. ● Unlike the other Microbial diseases, Microbial diseases of the digestive system usually result from ingestion of food and water contaminated with pathogenic microorganisms or their toxins. ● Microbial diseases of the Digestive system are typically transmitted by a fecal-oral cycle. - Pathogens usually enter the food or water supply after being shed in feces of people or animals infected them. - Proper, responsible and effective sanitation practices in food handling and/or by modern methods of sewage treatment and disinfection of drinking water can prevent this cycle.
3. Structure and Function of the Digestive System ● Digestive system is divided into two principal groups of organs: - Gastrointestinal (GI) Tract or Alimentary canal ● Includes mouth, pharynx, esophagus, stomach, small intestine, and large intestine. - Accessory structures ● Includes teeth, tongue, salivary glands, liver, gallbladder, and pancreas. ● The purpose of digestive system is to digest food – that is, to break them down into small molecules that can be taken up and used by body cells. The process is called absorption. ● The end-products of digestion pass from the small intestine into the blood or lymph for distribution to body cells. Then the food moves through the large intestine where water, vitamins, and nutrients are absorbed from it. ● The resulting undigested solid (feces), are eliminated via anus.
4. Normal Microbiota of the Digestive System ● A wide variety of bacteria colonize the mouth, with each milliliter of saliva can contain millions of bacteria. ● The stomach and small intestine have relatively few microorganisms because of the acidity of the stomach. ● The large intestine have enormous microbial populations, exceeding 100 billion bacteria per gram of feces. – Anaerobes in genera lactobacillus and bacterioides, and facultative anaerobes, such as E. coli, and Enterobacter, Klebsiella, and Proteus spp. Inhabited the large intestine. ● *Facultative anaerobes are organisms that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation or anaerobic respiration if oxygen is absent.
5. Lactobacillus Bacteroides E. coli - Most of these bacteria assist in the enzymatic breakdown of foods, and some of them synthesize useful vitamins.
6. Bacterial Diseases of the Mouth ● Dental Caries (Tooth Decay) – Begin when enamel and dentin are eroded, leaving the pulp cavity exposed to bacterial infection. – The bacterium Streptococcus mutans, a cariogenic (caries- causing) bacterium found in the mouth, uses sucrose to form dextran from glucose and lactic acid from fructose. ● Bacteria adhere to teeth and begin to produce a gummy polysaccharide of glucose called dextran. Then forms into dental plaque ● Acid produced during carbohydrate fermentation destroys tooth enamel at the site of the plaque. ● Once the enamel is destroyed via Demineralisation, the pulp will be left exposed. Leaving the pulp cavity open and may form abscesses in the tissues surrounding the root caused by the decay if it left untreated. – Caries are prevented by restricting the ingestion of sucrose and by the physical removal plaque.
7. Periodontal Disease ● Periodontal disease, a term for a number of conditions characterized by inflammation and degeneration of structures that supports the teeth. – The roots of the tooth are protected by a covering of specialized connective tissue called cementum. ● As the gums recede with age, the formation of caries on the cementum becomes more common. ● Gingivitis is an inflammation of the gums, or gingivae. – Gingivitis is caused by streptococci, actinomycetes, and anaerobic gram-negative bacteria.
8. ● Gingivitis can progress to a chronic condition called periodontitis, which is responsible for nearly 10% of tooth loss in older adults. – Toxins destroy the gingiva and bone that support the tooth and the cementum that protects the root. – periodontitis is due to an inflammatory response to a variety of bacteria growing on the gums. ● Acute necrotizing ulcerative gingivitis, also termed Vincent's disease or trench mouth, is one of the more common serious mouth infections. The disease causes enough pain that normal chewing is difficult. – This mouth disease is caused by a bacteria Prevotella intermedia.
9. Tooth Decay Gingivitis Periodontitis Acute Necrotizing Ulcerative Gingivitis
10. Healthy Gingivitis Periodontitis
11. Bacterial diseases of the lower Digestive system ● Diseases of the digestive system are essentially of two types: – Infections ● It occurs when a pathogen enters the GI tract and multiplies. ● Symptoms of infection generally include a fever. – Intoxication ● It is caused by the ingestion of such a preformed toxins. ● Fever is not usually a symptom of intoxication. ● Both infections and intoxications often cause diarrhea, dysentery (severe diarrhea accompanied by blood or mucus), abdominal cramps, nausea, vomiting and gastroenteritis (disease causing inflammation of the stomach and intestinal mucosa). ● These conditions are usually treated with fluid and electrolyte replacement.
12. Staphylococcal Food Poisoning (Staphylococcal Enterotoxicosis) ● A leading cause of gastroenteritis. An intoxication caused by ingesting an enterotoxin produced by S. aureus. ● S. aureus is often an inhabitant of the nasal passages, from which it contaminates the hands, and inoculated into the food. As it enters the food, it incubates in the food, a situation called temperature abuse, they reproduce and release enterotoxin into the food. ● S. aureus produces several toxins that damage tissues or increase the microorganism's virulence. – The toxin quickly triggers the brain's vomiting reflex center; abdominal cramps and usually diarrhea. Recovery is usually completed within 24 hours.
13. Shigellosis (Bacillary Dysentery) ● It is a severe form of diarrhea caused by a group of facultative anaerobic gram-negative rods of the genus Shigella. ● Shigellosis can cause as many as 20 bowel movements in one day. Additional symptoms of infection are abdominal cramps and fever. Infection with S. dysenteriae often results in a severe dysentery and prostration. Also causes ulceration in the intestinal mucosa. ● Diagnosis is usually based on recovery of the microbes from rectal swabs.
14. Salmonellosis (Salmonella Gastroenteritis) ● The Salmonella bacteria (named for their discoverer, Daniel Salmon) are gram-negative, facultatively anaerobic, non–endospore-forming rods. Their normal habitat is the intestinal tracts of humans and many animals. ● All salmonellae are considered pathogenic to some degree, causing salmonellosis, or Salmonella gastroenteritis. ● Salmonellosis has an incubation time of about 12 to 36 hours. ● Symptoms include moderate fever accompanied by nausea, abdominal pain and cramps, and diarrhea. ● The mortality rate is overall very low, probably less than 1%. However, the death rate is higher in infants and among the very old; death is usually from septic shock. ● *Septic shock is what happens as a complication of an infection where toxins can initiate a full-body inflammatory response. It often occurs in people who are elderly or have a weakened immune system.
15. ● Prevention also depends on good sanitation practices to deter contamination and on proper refrigeration to prevent increases in bacterial numbers. The microbes are generally destroyed by normal cooking. Chicken, for example, should be cooked at temperatures of 76–82°C and ground beef at 71°C. ● Laboratory diagnosis is based on isolation and identification of Salmonella from feces and foods.
16. Typhoid Fever ● The most virulent serotype of Salmonella, S. typhi, causes the bacterial disease typhoid fever. ● This pathogen is not found in animals; it is spread only in the feces of other humans. ● The patient with typhoid fever suffers from a high fever of about 40°C and continual headache. Diarrhea appears only during the second or third week, and the fever then tends to decline. In severe cases, which can be fatal, ulceration and perforation of the intestinal wall can occur. ● Substantial numbers of recovered patients, about 1–3%, become chronic carriers. They harbor the pathogen in the gallbladder and continue to shed bacteria for several months. A number of such carriers continue to shed the organism indefinitely. ● Vaccines are available for high-risk people.
17. Cholera ● The causative agent of cholera, one of the most serious gastrointestinal diseases, is Vibrio cholerae, a slightly curved, gram-negative rod with a single polar flagellum. ● Cholera bacilli grow in the small intestine and produce an exotoxin, cholera toxin.It alters the membrane permeability of the intestinal mucosa; the resulting vomiting and diarrhea cause a loss of body fluid. ● The incubation period is approximately 3 days. The symptoms last a few days; profuse watery diarrhea, vomiting, and leg cramps. Rapid loss of body fluids leads to dehydration and shock. Untreated cholera has a 50% mortality rate. ● Treatment often includes the use of antibiotics such as doxycycline, but the most effective therapy is intravenous replacement of the lost fluids and electrolytes. As much as 10% of the patient’s body weight within a few hours may be required. Rehydration therapy is so effective that in Bangladesh, for example, where cholera is common, deaths are considered “unusual.”
18. Noncholera Vibrios ● At least 11 species of Vibrio, in addition to V. cholerae, can cause human illness. Most are adapted to life in salty coastal waters. ● Signs and symptoms, which resemble those of cholera, include abdominal pain, vomiting, a burning sensation in the stomach, and watery stools. Treatment by antibiotics and rehydration is usually effective. The incubation time is normally less than 24 hours. Recovery usually follows in a few days. ● The disease is contracted by eating contaminated crustaceans or contaminated mollusks. ● Vibrio gastroenteritis can be caused by V. parahamolticus and V. vulnificus.
19. Escherichia coli Gastroenteritis ● E. coli are normally harmless, but certain strains can be pathogenic. ● E. coli Gastroenteritis can be caused by these strains of E. coli: – Enteropathogenic E. coli (EPEC) – Enteroinvasive E. coli (EIEC) – Enterointoxigenic E. coli (ETEC) – Enteroaggregative E. coli (EAEC) – Shiga-toxin-producing E. coli (STEC) ● The disease occurs as epidemic diarrhea in nurseries, as traveler's diarrhea, as endemic diarrhea is less developed countries, and as hemorrhagic colitis. ● Traveler's diarrhea is a digestive tract disorder that commonly causes loose stools and abdominal cramps. ● Enterohemorrhagic E.coli, such as E.coli O157:H7, produces Shiga toxins that cause inflammation and bleeding of the colon, including hemorrhagic colitis. Shiga toxins can also affect the kidneys to cause hemolytic uremic syndrome. ● *Hemorrhagic colitis is a type of gastroenteritis in which certain strains of the bacterium Escherichia coli infect the large intestine and produce a toxin (Shiga toxin) that causes bloody diarrhea and other serious complications. ● *Hemolytic uremic syndrome (HUS) is a condition that results from the abnormal premature destruction of red blood cells. Once this process begins, the damaged red blood cells start to clog the filtering system in the kidneys, which may eventually cause the life-threatening kidney failure associated with hemolytic uremic syndrome.
20. Campylobacter Gastroenteritis ● Campylobacter are gram-negative, microaerophilic, spirally curved bacteria that have emerged as the leading cause of food- borne illness in the United States. ● The bacteria’s optimum growth temperature of about 42°C approximates that of their animal hosts, but the bacteria do not replicate in food. ● Clinically, it is characterized by fever, cramping abdominal pain, and diarrhea or dysentery. Normally, recovery follows within a week.
21. Helicobacter Peptic Ulcer Disease ● This syndrome includes gastric and duodenal ulcers. ● Helicobacter pylori produces ammonia, which neutralizes stomach acid; the bacteria colonize the stomach mucosa and cause peptic ulcer diseases. ● The eradication of H. pylori with antimicrobial drugs usually leads to the disappearance of peptic ulcers. Several antibiotics, usually administered in combination, have proven effective. Bismuth subsalicylate (Pepto-Bismol) is also effective and is often part of the drug regimen.
22. Yersinia Gastroenteritis ● Yersinia enterocolitica and Y. pseudotuberculosis. These gram-negative bacteria are intestinal inhabitants of many domestic ani-mals and are often transmitted in meat and milk. ● These pathogens cause Yersinia gastroenteritis, or yersiniosis. The symptoms are diarrhea, fever, headache, and abdominal pain. The pain is often severe enough to cause a misdiagnosis of appendicitis.
23. Clostridium perfringens Gastroenteritis ● A large, gram-positive, endospore-forming, obligately anaerobic rod. This bacterium is also responsible for human gas gangrene. ● *Gas gangrene (also known as clostridial myonecrosis and myonecrosis) is a bacterial infection that produces gas in tissues in gangrene. ● Most outbreaks of Clostridium perfringens gastroenteritis are associated with meats or meat stews contaminated with intestinal contents of the animal during slaughter. ● Endospores survive heating and germinate when foods (usually meats) are stored at room temperature. ● Exotoxin produced when the bacteria grow in the intestines is responsible for the symptom. ● Diagnosis is based on isolation and identification of bacteria is stool samples.
24. Clostridium difficile–associated diarrhea● Clostridium difficile–associated diarrhea, is a diseases condition that has appeared in recent decades and has been described as being responsible for more deaths than all other intestinal infections combined. C. difficile is a gram-positive, endospore-forming anaerobe found in the stool of many healthy adults. ● The exotoxins it produces cause a disease that manifests itself in symptoms ranging from a mild case of diarrhea to life-threatening colitis (inflammation of the colon). The colitis can result in ulceration, and possible perforation, of the intestinal wall. ● A diagnosis of C. difficile–associated diarrhea can be confirmed by an immunoassay that detects the responsible exotoxins. ● Taking antibiotics can kill these "good" bacteria, allowing C. difficile to multiply and release toxins that damage the cells lining the intestinal wall. ● Treatment, of course, requires discontinuation of the precipitating antibiotic and oral rehydration therapy. Treatment usually involves metronidazole, a drug that targets the metabolism of anaerobes, or the antibiotics fidaxomicin or vancomycin. – Other treatments are Nonantibiotic Polymer, Immunoglobulins, Probiotics,
25. Bacillus cereus Gastroenteritis ● Bacillus cereus is a large, gram-positive, endospore- forming bacterium that is very common in soil and vegetation and is generally considered harmless. It has, however, been identified as the cause of outbreaks of foodborne illness. ● Some cases of Bacillus cereus gastroenteritis resemble C. perfringens intoxications and are almost entirely diarrheal in nature (usually appearing 8 to 16 hours after ingestion). Other episodes involve nausea and vomiting (usually 2 to 5 hours after ingestion).
26. Viral Diseases of the Digestive System ● Mumps – Mumps virus enters and exits the body through the respiratory tract. – About 16-18 days after exposure, the virus causes inflammation of the parotid glands, fever, and pain during swallowing. About 4-7 days later, orchitis may occur. ● Orchitis is an inflammation of one or both of the testicles. – After onset of the symptoms, the virus is found in the blood, saliva, and urine. – A measles, mumps, rubella (MMR) vaccine is available. – Diagnosis is based on symptoms, or an ELISA test is performed on viruses cultured in embroyonated eggs or cell culture.
27. Hepatitis ● Hepatitis is an inflammation of the liver. At least five different viruses cause hepatitis, and probably more remain to be discovered or become better known. ● Symptoms include loss of appetite, malaise, fever, and jaundice. ● Viral causes of hepatitis include hepatitis viruses, Epstein-Barr virus (EBV), and cytomegalovirus (CMV).
28. Hepatitis A ● The hepatitis A virus (HAV) is the causative agent of hepatitis A.The virus contains single-stranded RNA and lacks an envelope. It can be grown in cell culture. ● At least 50 % of all cases are subclinical. In clinical cases, the initial symptoms are anorexia (loss of appetite), malaise, nausea, diarrhea, abdominal discomfort, fever, and chills. ● HAV is ingested in contaminated food or water, grows in the cells of the intestinal mucosa, and spreads to the liver, kidneys, and spleen in the blood. ● The virus is eliminated with feces. ● The incubation period 2-6 weeks; the period of disease is 2-21days, and recovery is complete in 4-6 weeks. ● Diagnosis is based on tests for IgM antibodies. ● No specific treatment for the disease exists, but people at risk of exposure or who have been exposed to hepatitis A can be given immune globulin, which provides protection for several months. Inactivated vaccines are now available and are recommended for travelers to areas of endemic disease and for high-risk groups, such as homosexual men and injecting drug users (IDUs). HAV vaccination is now part of the recommended childhood vaccination schedule.
29. Hepatitis B ● Hepatitis B virus (HBV) causes hepatits B, which is frequently serious. ● HBV is transmitted by blood transfusions, contaminated syringes, salvia, sweat, breast milk, and semen. ● Blood is tested for HbsAg (hepatitis B surface antigen) before being used in transfusion. ● The average incubation period is 3 months; recovery is usually complete, but some patients develop a chronic infection or become carriers. ● A vaccine against HBsAg is available. ● Hepatitis B can be acute or chronic.
30. Hepatitis C, D and E ● Hepatitis C – Hepatitis C virus (HCV) is transmitted via blood. – The average incubation period is 2-22 weeks: the disease is usually mild, but some patients develop chronic hepatitis. – Blood is tested for HCV antibodies before being used in transfusion. ● Hepatitis D – Hepatitis D virus (HCV) has a circular strand of RNA and uses HBsAg as a coat. ● Hepatitis E – Hepatitis E virus (HEV) is spread by the fecal-oral route. ● Other Types of Hepatitis – There is an evidence of the existence of of blood-transmitted viruses known as hepatitis F (HFV) and hepatitis G (HGV).
31. Viral Gastroenteritis ● Acute gastroenteritis is one of the most common diseases of humans. About 90% of cases of acute viral gastroenteritis are caused by either the rotavirus or the human caliciviruses, better known as the Norwalk family of viruses; or collectively, the noroviruses. – Rotavirus is the most common viral gastroenteritis especially in children. It can cause low-grade fever, diarrhea, and vomiting. These symptoms last for about a week. – Norovirus or Norwalk-like virus which cause vomiting and/or diarrhea for 2 or 3 days in patients. ● The main focus of treatment is to prevent dehydration by drinking plenty of fluids. In severe cases, hospitalization and intravenous fluids are necessary.
32. Fungal Infection in Digestive System ● Some fungi produce toxins called mycotoxins. When ingested, these toxins cause blood diseases, nervous system disorders, kidney damage, liver damage, and even cancer. Mycotoxin intoxication is considered when multiple patients have similar clinical signs and symptoms. Diagnosis is usually based on finding the fungi or mycotoxins in the suspected food. ● Ergot Poisoning – The mycotoxins produced by C. purpurea cause ergot poisoning, or ergotism, which results from the ingestion of rye or other cereal grains contaminated with the fungus. – The toxin can restrict blood flow in the limbs, with resulting gangrene. It may also cause hallucinogenic symptoms, producing bizarre behavior similar to that caused by LSD.
33. ● Aflatoxin Poisoning – Aflatoxin is a mycotoxin produced by the fungus Aspergillus flavus, a common mold. Aflatoxin has been found in many foods but is particularly likely to be found on peanuts. – Aflatoxin poisoning can cause serious damage to livestock when their feed is contaminated with A. flavus. Although the risk to humans is unknown, there is strong evidence that aflatoxin contributes to cirrhosis of the liver and cancer of the liver in parts of the world, such as India and Africa, where food is subject to aflatoxin contamination.
34. Protozoan Diseases of the Digestive System ● Usually they are ingested as resistant, infective cysts and are shed in greatly increased numbers as newly produced cysts. ● Giardiasis – Giardia lamblia grows in the intestines of humans and wild animals and is transmitted in contaminated water. – Symptom of giardiasis are malaise, nausea, flatulence, weakness, and abdominal cramps that persist for weeks. – Diagnosis is based on identification of the protozoa in the small intestine.
35. ● Cryptosporidiosis – Crytosporidium parvum causes diarrhea; in immunosuppressed patients, the disease is prolonged for months. – The pathogen is transmitted in contaminated water. – Diagnosis is based in the identification of oocysts in feces. – Nitazoxanide has been FDA-approved for treatment of diarrhea caused by Cryptosporidium in people with healthy immune systems and is available by prescription. However, the effectiveness of nitazoxanide in immunosuppressed individuals is unclear. ● Cyclospora diarrheal infection – C. cayetanensis causes diarrhea; the protozoan was first identified in 1993. – It is transmitted in contaminated produce. – The symptoms of Cyclospora diarrheal infection are a few days of watery diarrhea, but in some cases it may persist for weeks. – Diagnosis is based on the identifcation of oocysts in feces. – The antibiotic combination of trimethoprim and sulfamethoxazole is used for treatment.
36. ● Amoebic dysentery (Amebiasis) – Amoebic dysentery is caused by Entamoeba histolyica growing the large intestine. – Although stomach acid can destroy trophozoites, it does not affect the cysts. In the intestinal tract, the cyst wall is digested away, and the trophozoites are released. They then multiply in the epithelial cells of the wall of the large intestine. – Diagnosis of Amoebic dysentery is by identifying the pathogens in feces. – Metronidazole plus iodoquinol are the drugs of choice in treatment.
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