Microbiology An Introduction - Diseases of the GI Tract PDF

Microbiology an Introduction Chapter 25 Microbial Diseases of the Digestive System Copyright © 2021 Pearson Education Ltd. All Rights Reserved Bacterial Diseases of the Lower Digestive System Staphyloc...

Microbiology an Introduction Chapter 25 Microbial Diseases of the Digestive System Copyright © 2021 Pearson Education Ltd. All Rights Reserved Bacterial Diseases of the Lower Digestive System Staphylococcal Food Poisoning Enterotoxin produced by Staphylococcus aureus – Toxin is not inactivated 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 Copyright © 2021 Pearson Education Ltd. All Rights Reserved  ‫راحزال‬ ‫ايبيالم‬ Shigellosis (Bacillary Dysentery) Caused by the genus Shigella – Facultatively anaerobic; gram-negative 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 Copyright © 2021 Pearson Education Ltd. All Rights Reserved Figure 25.7 Shigellosis Shigella M cell Epithelial cell lining intestinal tract Membrane ruffle Shigella enters an epithelial cell. Shigella multiplies inside the cell. Shigella invades neighboring epithelial cells, thus avoiding immune defenses. An abscess forms as epithelial cells are killed by the infection. The bacteria rarely spread in the bloodstream. Mucosal abscess Copyright © 2021 Pearson Education Ltd. All Rights Reserved Salmonellosis (Salmonella Gastroenteritis) Salmonella enterica – Gram-negative, facultative anaerobe – Normal inhabitant of the human intestinal tract and many animals – 2000 serotypes Invades intestinal mucosa and multiplies – Passes through M cells and enters the lymphatics – Replicates in macrophages fever, nausea, pain and cramps, diarrhea Copyright © 2021 Pearson Education Ltd. All Rights Reserved  Salmonella M Figure 25.8 cell Epithelial cell Salmonellosis lining intestinal tract Membrane ruffle Salmonella enters an epithelial cell. Salmonella multiplies within a vesicle inside the cell. Salmonella multiplies in mucosal cells; there the inflammatory response results in diarrhea. Occasionally, the bacteria cross the epithelial cell membrane and enter the lymphatic system and bloodstream. Lymph node Bloodstrea m Copyright © 2021 Pearson Education Ltd. All Rights Reserved Typhoid Fever Caused by Salmonella serotype Typhi – Spread only by human feces 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 Copyright © 2021 Pearson Education Ltd. All Rights Reserved 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” Pateint lose 12 to 20 liters of fluid per day – Causes shock, collapse, organ failure, and death Treatment includes IV fluid replacement. Copyright © 2021 Pearson Education Ltd. All Rights Reserved 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 Copyright © 2021 Pearson Education Ltd. All Rights Reserved Campylobacteriosis (Campylobacter Gastroenteritis) Caused by Campylobacter jejuni – Gram-negative, microaerophilic, spirally curved Foodborne illness – Common in the intestines of poultry – 60% of cattle excrete organism in feces and milk Fever, cramping, abdominal pain, diarrhea, dysentery One in 1000 cases leads to Guillain-Barré syndrome (autoimmune disease damaging peripheral nerves). Helicobacter Peptic Ulcer Disease Caused by Helicobacter pylori – Grows in the stomach acid by producing urease Converts urea to alkaline ammonia – Disrupts stomach mucosa, causing inflammation Treated with antimicrobial drugs Diagnostic test requires a biopsy, culture, and urea breath test. 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 Copyright © 2021 Pearson Education Ltd. All Rights Reserved Viral Diseases of the Digestive System Mumps Virus targets the parotid glands – Painful swelling 16 to 18 days after exposure Transmitted in the saliva and respiratory secretions – Multiplies in respiratory tract and reaches the salivary glands via the bloodstream May cause orchitis (swelling of testes), meningitis, ovary inflammation, and pancreatitis Prevented with MMR vaccine Copyright © 2021 Pearson Education Ltd. All Rights Reserved Figure 25.13 A Case of Mumps Copyright © 2021 Pearson Education Ltd. All Rights Reserved Hepatitis A Hepatitis A virus (HAV) – 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 Inactivated vaccine for prevention Copyright © 2021 Pearson Education Ltd. All Rights Reserved Hepatitis B Hepatitis B virus (HBV) Transmitted via the blood and bodily fluids – Up to 1 billion viruses per ml of blood Prevented by a vaccine Copyright © 2021 Pearson Education Ltd. All Rights Reserved Hepatitis B Acute hepatitis B – Similar symptoms to hepatitis A; gradual recovery Chronic hepatitis B – Involves 10% of infected patients – May lead to liver cirrhosis or liver cancer – Treated with interferons Copyright © 2021 Pearson Education Ltd. All Rights Reserved Hepatitis C Hepatitis C virus (HCV) – Often transfusion-transmitted Destroys the liver by using genetic variation to evade the immune response 85% of cases become chronic – 25% develop liver cirrhosis or cancer No vaccine Copyright © 2021 Pearson Education Ltd. All Rights Reserved Diseases in Focus 25.3 Healthy liver. Copyright © 2021 Pearson Education Ltd. All Rights Reserved Viral Gastroenteritis Rotavirus – Common in children; low mortality – low-grade fever, diarrhea, vomiting – Prevented with a live oral vaccine Norovirus – Fecal-oral transmission – Low infectious dose – diarrhea and vomiting Copyright © 2021 Pearson Education Ltd. All Rights Reserved Protozoan Diseases of the Digestive System Giardiasis Caused by Giardia intestinalis – Flagellated protozoan – Attaches to the intestinal wall Prolonged diarrhea, malaise, weight loss, flatulence, cramps Copyright © 2021 Pearson Education Ltd. All Rights Reserved 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 Copyright © 2021 Pearson Education Ltd. All Rights Reserved Hydatid Disease Caused by the tapeworm Echinococcus granulosus Eggs are ingested and migrate to the liver, lungs, or brain. – Develops a hydatid cyst Can grow and hold up to 15 liters of fluid May rupture, causing anaphylactic shock Diagnosis with serological tests, X-rays, CT, and MRI Treatment with surgical removal or albendazole Copyright © 2021 Pearson Education Ltd. All Rights Reserved Figure 25.23 A Hydatid Cyst Formed by Echinococcus Granulosus Right lung Cyst Copyright © 2021 Pearson Education Ltd. All Rights Reserved