Microbial Diseases of the Digestive System

Transcription

1 PowerPoint Lecture Presentations prepared by Bradley W. Christian, McLennan Community College C H A P T E R 25 Microbial Diseases of the Digestive System

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3 Figure 25.1 The human digestive system. Parotid (salivary) gland Pharynx Oral cavity Tongue Teeth Esophagus Liver Gallbladder Stomach Duodenum Pancreas Small intestine Large intestine Rectum Anus

4 Normal Microbiota of the Digestive System Millions of bacteria per ml of saliva Few microorganisms in the stomach Due to HCl production Large numbers of bacteria in the large intestine Anaerobes and facultative anaerobes 100 billion bacteria per gram of feces

5 Staphylococcal Food Poisoning (Staphylococcal Enterotoxicosis) Enterotoxin produced by Staphylococcus aureus Serological type A Coagulates blood plasma Toxin is not killed by boiling Toxins produced when the organism is allowed to incubate in food (temperature abuse) S. aureus outgrows most bacteria in high osmotic pressure and high temperature Phage typing traces sources of contamination

6 Figure 25.6 The sequence of events in a typical outbreak of staphylococcal food poisoning.

7 Shigellosis (Bacillary Dysentery) Caused by the genus Shigella Facultatively anaerobic; gram-negative Four species Produces the Shiga toxin Small infectious dose Attaches to M cells, invades, and spreads to other cells Damage to the intestinal wall Can invade the bloodstream

8 Salmonellosis (Salmonella Gastroenteritis) Salmonella enterica Gram-negative, facultative anaerobe, nonendosporeforming rods Normal inhabitant of the human intestinal tract 2000 serotypes Invades intestinal mucosa and multiplies Passes through M cells and enters the lymphatics Replicates in macrophages Incubation of 12 to 36 hours; fever, nausea, pain and cramps, diarrhea

9 Salmonellosis (Salmonella Gastroenteritis) 1.4 million cases; 400 deaths annually Associated with commercial chicken and egg production Bacteria survive in the albumin Diagnosed directly from the stool or by PCR Treatment with oral rehydration therapy

10 Typhoid Fever Caused by Salmonella typhi Spread only by human feces Rare in the United States today due to sanitation Bacteria spread throughout the body in phagocytes Releases organism into the bloodstream High fever, headache, intestinal wall ulceration 1 3% of patients become chronic carriers Harbor the organism in the gallbladder

11 Cholera Caused by Vibrio cholerae Slightly curved, gram-negative rod with single polar flagellum Associated with salty waters Produces the cholera toxin Toxin causes the host cells to secrete electrolytes and water Causes "rice water stools" Can lose 12 to 20 liters of fluid per day Causes shock, collapse, organ failure, and death Treatment includes IV fluid replacement

12 Figure Vibrio cholerae, the cause of cholera. Vibrio cholerae

13 Big Picture: Cholera after Natural Disasters Cholera increases when sanitation and sewage disposal systems are compromised Outbreak in Haiti after earthquake due to deficient septic system at the Nepalese base Nepalese soldiers were part of the United Nations peacekeeping force

14 Big Picture: Cholera after Natural Disasters Strategies for disaster preparedness Oral rehydration solutions Salt, sugar, and water Stockpiling vaccines The ultimate solution Proper sanitation, water storage, handwashing

15 Escherichia coli Gastroenteritis Enterohemorrhagic E. coli (EHEC) Produces Shiga-like toxin Released upon the cell's lysis Most outbreaks are due to serotype O157:H7 Cattle are the main reservoir Causes hemorrhagic colitis and hemolytic uremic syndrome

16 Figure Pedestal formation by Enterohemorrhagic E. coli (EHEC) O157:H7.

17 Traveler's Diarrhea Most common cause Enteroaggregative E. coli Can also be caused by Salmonella, Shigella, and Campylobacter Oral rehydration therapy and bismuth-containing preparations

18 Helicobacter Peptic Ulcer Disease Caused by Helicobacter pylori Infects 30 50% of the population in the developed world Grows in the stomach acid by producing urease Converts urea to alkaline ammonia Disrupts stomach mucosa, causing inflammation Diagnostic test requires a biopsy, culture, and urea breath test

19 Clostridium difficile Associated Diarrhea Gram-positive, endospore-forming anaerobe Causes more deaths than all other intestinal infections combined Mostly in health care settings Life-threatening colitis Ulceration and perforation of the intestinal wall Precipitated by the extended use of antibiotics Eliminates competing intestinal bacteria

20 Hepatitis Inflammation of the liver May result from drug or chemical toxicity, Epstein- Barr virus (EBV), cytomegalovirus (CMV), or the hepatitis viruses

21 Hepatitis A Hepatitis A virus (HAV) Single-stranded RNA; lacks an envelope Entry via the oral route; multiplies in the epithelial lining of the intestinal tract Spreads to the liver, kidneys, and spleen Anorexia, malaise, nausea, diarrhea, fever, chills Later, jaundice and dark urine Symptoms last 2 to 21 days; low mortality

22 Hepatitis B Hepatitis B virus (HBV) Double-stranded DNA; enveloped Resembles retroviruses Transmitted via the blood and bodily fluids Up to 1 billion viruses per ml of blood Prevented by a vaccine

23 Hepatitis B Acute hepatitis B Often subclinical Similar symptoms to hepatitis A; gradual recovery Fulminant hepatitis in 1% of cases Sudden massive liver damage; fatal Chronic hepatitis B (HB e Ag) Involves 10% of infected patients May lead to liver cirrhosis or liver cancer Presence of HB e Ag indicates a vigorously replicating virus Treated with interferons and nucleoside analogs

24 Hepatitis C Hepatitis C virus (HCV) Single-stranded RNA; enveloped Often transfusion-transmitted Destroys the liver by using genetic variation to evade the immune response Kills more in the United States than AIDS 85% of cases become chronic 25% develop liver cirrhosis or cancer No vaccine

25 Diseases in Focus 25.3 (2 of 3)

26 Amebic Dysentery (Amebiasis) Caused by Entamoeba histolytica Produces cysts that survive stomach acid Trophozoites produced from cysts in the intestines Multiply in the wall of the large intestine Feces contain blood and mucus Can perforate the intestinal wall, causing abscesses Organisms invade the liver

27 Figure Section of intestinal wall showing a typical flaskshaped ulcer caused by Entamoeba histolytica. Normal mucosa Ulcer

28 Gonorrhea Caused by Neisseria gonorrhoeae Gram-negative diplococcus 300,000 cases in the United States annually Attaches to the epithelial mucosa by the fimbriae Invades the spaces between the columnar epithelial cells Causes inflammation Forms pus Pharyngeal gonorrhea and anal gonorrhea

29 Figure 26.5b The U.S. incidence and distribution of gonorrhea. DC Guam Puerto Rico Virgin Is. KEY Rate per 100,000 population Note: The total rate of gonorrhea for the United States and outlying areas (Guam, Puerto Rico, and Virgin Islands) was per 100,000 population. Geographical distribution of cases in >100.0

30 Gonorrhea Symptoms Men: painful urination and discharge of pus; epididymitis Women: fewer symptoms; pelvic inflammatory disease If left untreated, may disseminate and become systemic Endocarditis Meningitis Arthritis Ophthalmia neonatorum: infant blindness due to a gonorrheal infection of the eyes

31 Gonorrhea No adaptive immunity Antigenic variability Opa proteins bind to T cell receptors, preventing activation and immunological memory Diagnosis with Gram stain, ELISA, or monoclonal antibodies Treatment first with cephalosporins Fluoroquinolones not recommended due to resistance

32 Figure 26.7 A smear of pus from a patient with gonorrhea. Leukocyte nuclei Neisseria gonorrhoeae

33 Syphilis Caused by Treponema pallidum Gram-negative spirochete Grows slowly in cell culture Invades the mucosa or through skin breaks and enters the bloodstream Induces an inflammatory response Some strains cause yaws Skin disease is not sexually transmitted Stable incidence in the United States

34 Figure 26.9 Treponema pallidum, the cause of syphilis.

35 Figure The U.S. incidence and distribution of primary and secondary syphilis. DC Guam Puerto Rico Virgin Is. Incidence of syphilis in the United States, Note: The primary and secondary syphilis rate in the United States and territories (Guam, Puerto Rico, and Virgin Islands) was 5.1 cases per 100,000 population. Geographical distribution of cases in 2012 KEY Rate per 100,000 population >2.2

36 Syphilis Primary stage Chancre at the site of infection about 3 weeks after exposure Painless and highly infectious Disappears after 2 weeks Secondary stage Skin and mucosal rashes, especially on the palms and soles Due to an inflammatory response Latent period No symptoms

37 Syphilis Tertiary stage Appear years after latency Due to cell-mediated immune reactions Gummatous syphilis: gummas on many organs Cardiovascular syphilis: weakens the aorta Neurosyphilis: affects the CNS; dementia Congenital: neurological damage to the fetus

38 Figure Characteristic lesions associated with various stages of syphilis.

39 Genital Herpes Caused by herpes simplex virus type 2 (HSV 2) In the United States, 1 in 4 over age 30 are infected Painful vesicles on the genitals; painful urination Heals within 2 weeks Recurrences from viruses latent in nerve cells Due to menstruation, emotional stress, or illness Diagnosis via culture or PCR No cure; suppression and management with acyclovir, famciclovir, and valacyclovir

40 Figure Genital herpes: initial visits to physicians' offices, United States, 1966 to 2012.

41 Figure Vesicles of genital herpes on a penis.

42 Neonatal Herpes Herpesvirus crosses the placental barrier and infects the fetus Damages the CNS, developmental delays, blindness, hearing loss Survival rate of 40% Newborns infected from HSV exposure during delivery Diagnosed by PCR tests and fluorescent antibody tests Treatment with intravenous acyclovir