Microbial Diseases of the Digestive System PDF

Pharmacy Chapter 25: Microbial Diseases of the Digestive System Microbiology II : 1 Dr. Mohammad Al-Najjar and Dr. Amin Omar : Introduction Diseases of the digestive system usually result from the ingestion of microorganisms or their toxins in food and water Fecal–oral transmission can be interrupte...

Pharmacy Chapter 25: Microbial Diseases of the Digestive System Microbiology II : 1 Dr. Mohammad Al-Najjar and Dr. Amin Omar : Introduction Diseases of the digestive system usually result from the ingestion of microorganisms or their toxins in food and water Fecal–oral transmission can be interrupted by proper disposal of sewage disinfection of drinking water proper food preparation and storage >700 bacterial species in mouth. Stomach and small intestine have few resident microbes Up to 40% of fecal mass is microbial cells. Bacteria in large intestine assist in: ✓ degrading food ✓ synthesizing vitamins ✓ competitively inhibit pathogens ✓ chemically alter medications ✓ produce carcinogens Structure and Function of the Digestive System The digestive system is essentially a tube-like structure, the gastrointestinal (GI) tract, or alimentary canal—mainly the mouth, pharynx (throat), esophagus (food tube leading to the stomach), stomach, and the small and large intestines. It also includes accessory structures such as the teeth and tongue. the salivary glands, liver, gallbladder, and pancreas lie outside the GI tract and produce secretions that are conveyed by ducts into it. Normal Microbiota of the Digestive System Bacteria heavily populate most of the digestive system. In the mouth, each milliliter of saliva can contain millions of bacteria. Because of the hydrochloric acid produced by the stomach and the rapid movement of food through the small intestine, these organs house relatively few microorganisms. By contrast, the large intestine has enormous microbial populations, exceeding 100 billion bacteria per gram of feces. (Up to 40% of fecal mass is microbial cell material.) The small intestine also contains important antimicrobial defenses, most significantly, millions of specialized, granule-filled cells called Paneth cells. These are capable of phagocytizing bacteria, and they also produce antibacterial proteins called defensins and the antibacterial enzyme lysozyme. Bacterial Diseases of the Mouth Dental Caries or dental plaques cause Tooth Decay are accumulations of masses of microorganisms and their products. The most important cariogenic (caries-causing) bacterium is Streptococcus mutans, a gram-positive. S. mutans is capable of metabolizing a wide range of carbohydrates, tolerates a high level of acidity, and synthesizes dextran, a gummy polysaccharide of glucose molecules that is an important factor in the formation of dental plaque The bacterial population of plaque may harbor over 400 bacterial species but is predominantly streptococci and filamentous members of the genus Actinomyces The stages of tooth decay Periodontal Disease Periodontal Disease is an Inflammation and degeneration of structures that support the teeth. Includes Gingivitis the infection is restricted to the gums, Periodontitis: chronic condition of Gingivitis. The stages of periodontal disease Bacterial Diseases of the Lower Digestive System 1. Staphylococcal Food Poisoning (Staphylococcal Enterotoxicosis) 2. Shigellosis (Bacillary Dysentery) 3. Salmonellosis (Salmonella Gastroenteritis) 4. Typhoid Fever 5. Cholera 6. Noncholera Vibrios 7. Escherichia coli Gastroenteritis Traveler’s Diarrhea 8. Campylobacteriosis (Campylobacter Gastroenteritis) 9. Helicobacter Peptic Ulcer Disease 10. Yersinia Gastroenteritis 11. Clostridium perfringens Gastroenteritis 12. Clostridium difficile–Associated Diarrhea 13. Bacillus cereus Gastroenteritis Bacterial Diseases of the Lower Digestive System Diseases of the digestive system are essentially of two types: ❖ Infections and Intoxications Infection occurs when a pathogen enters the GI tract and multiplies Intoxication is caused by the ingestion of toxin. Most intoxications are caused by Staphylococcus aureus. Both infections and intoxications often cause diarrhea, Severe diarrhea accompanied by blood or mucus is called dysentery. The general term gastroenteritis is applied to diseases causing inflammation of the stomach and intestinal mucosa. 1. Staphylococcal Food Poisoning (Staphylococcal Enterotoxicosis) leading cause of gastroenteritis is staphylococcal food poisoning, an intoxication caused by ingesting an enterotoxin produced by S. aureus. Symptoms ,nausea, vomiting and diarrhea begins after 1-6 hrs after eating and lasting for 24 hrs 2. Shigellosis (Bacillary Dysentery) Shigellosis, also known as bacillary dysentery to differentiate it from amebic dysentery infects human only. The toxin responsible is unusually virulent and is known as the Shiga toxin They proliferate to immense numbers in the small intestine, but the primary site of disease is the large intestine. There, the bacteria attach to epithelial M cells Treatment by; 1- rehydration 2- Fluoroquinolon (ciprofloxacin) which eliminates gut excretion 3. Salmonellosis (Salmonella Gastroenteritis) The salmonellae first invade the intestinal mucosa and multiply there. Occasionally they manage to pass through the intestinal mucosa at M cells to enter the lymphatic and cardiovascular systems, Infects animals and human Antibiotic therapy is not useful, only rehydration are required At severe case, toxemia and bloodstream infection may occur, Ciprofloxacin and Trimethoprim is appropriate treatment. 4. Typhoid Fever The most virulent serotype of Salmonella, S. typhi, causes the bacterial disease typhoid fever. Unlike the salmonellae that cause salmonellosis, this pathogen is not found in animals; it’s spread only in the feces of other humans. Instead of being destroyed by phagocytic cells, S. typhi multiply within them and are disseminated into multiple organs, especially the spleen and liver The patient with typhoid fever suffers from a high fever of about 40°C and continual headache. Treatment by: ❖ceftriaxone (third-generation cephalosporin) or azithromycin 5. Cholera Vibrio cholera is The causative agent of cholera, one of the most serious gastrointestinal diseases. Cholera bacilli grow in the small intestine and produce an exotoxin, that causes host cells to secrete water and electrolytes, especially potassium. The result is watery stools containing masses of intestinal mucus and epithelial cells— called “rice water stools”. As much as 12 to 20 liters (3 to 5 gallons) of fluids can be lost in a day, and the sudden loss of these fluids and electrolytes causes shock, collapse, and often death. Treatment by: 1. Replacement of fluids and electrolytes losses 2. Tetracycline effective in eliminating the vibrio from the bowel 6. Noncholera Vibrios One of the most causative is Vibrio parahaemolyticus found in Raw oysters and crustaceans, such as shrimp and crabs. 7. Escherichia coli Gastroenteritis Some toxin-secreting pathogenic strains of E. coli are well adapted to invasion of intestinal epithelial cells, causing gastroenteritis. Other locations, such as the urinary tract, bloodstream, and central nervous system, can also be affected. Five pathogenic varieties (pathotypes) of E. coli have been well characterized. 1. Enteropathogenic E. coli (EPEC) is a major cause of diarrhea in developing countries and is potentially fatal in infants. 2. Enteroinvasive E. coli (EIEC) is generally agreed to be almost synonymous with Shigella—it has the same pathogenic mechanisms. 3. Enteroaggregative E. coli (EAEC) is a group of coliforms found only in humans 4. Enterohemorrhagic E. coli (EHEC) these bacteria produce a Shiga-like toxin. 5. Enterotoxigenic E. coli (ETEC) secrets enterotoxins that cause diarrhea 8. Traveler’s Diarrhea It has long been observed that travel broadens the mind and loosens the bowels, leading to the common name of traveler’s diarrhea. The most common bacterial cause is ETEC and EAEC. Traveler’s diarrhea can also be caused by other gastrointestinal pathogens, such as Salmonella, Shigella Campylobacter As well as various unidentified bacterial pathogens, viruses, and protozoan parasites. 9. Campylobacteriosis (Campylobacter Gastroenteritis Campylobacter are gram-negative, microaerophilic, spirally curved bacteria that have emerged as the leading cause of tenesmus diarrhea. Caused by C. jejuni. Campylobacteriosis is prevented by thoroughly cooking chicken and pasteurizing milk. Usually transmitted in cow's milk Treated with azithromycin or erythromycin (In sever cases ) 10. Helicobacter Peptic Ulcer Disease Helicobacter is responsible for most cases of peptic ulcer disease. H. pylori can grow in the highly acidic environment of the stomach, which is lethal for most microorganisms. H. pylori produces large amounts of urease, an enzyme that converts urea to the alkaline compound ammonia, resulting in a locally high pH in the area of growth Several antibiotics, usually administered in combination, have proven effective in treatment. In addition, Bismuth subsalicylate (Pepto-BismolR) as well as proton pump inhibitor are also effective and are often part of the drug regimen. 11. Clostridium perfringens Gastroenteritis Clostridium perfringens is One of the most common, food poisoning It is a large, gram-positive, endospore-forming, obligate anaerobic rod. This bacterium is also responsible for human gas gangrene The microbe grows in the intestinal tract and produces an exotoxin that causes the typical symptoms of abdominal pain and diarrhea. 12. Clostridium difficile–Associated Diarrhea The elimination of most competing intestinal bacteria permits rapid proliferation of the toxin-producing C. difficile. Infections treatment could be with vancomycin although recurrence is common Viral Diseases of the Digestive System Mumps Hepatitis Viral Gastroenteritis Rotavirus and Norovirus Mumps The targets of the mumps virus, the parotid glands, Because the parotids are one of the three pairs of salivary glands of the digestive system, An infected person is most infective to others during the first 48 hours before clinical symptoms appear. Once the viruses have begun to multiply in the respiratory tract and local lymph nodes in the neck, they reach the salivary glands via the blood. An effective attenuated live vaccine is available and is often administered as part of the trivalent measles, mumps, rubella (MMR) vaccine 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. Hepatitis is an occasional result of infections by other viruses such as Epstein-Barr virus (EBV) or cytomegalovirus (CMV). Drug and chemical toxicity can also cause acute hepatitis that is clinically identical to viral hepatitis. Viral Gastroenteritis Rotavirus and Norovirus Rotavirus is probably the most common cause of viral gastroenteritis, especially in children (rota = wheel) Fungal Diseases of the Digestive System Mycotoxins are produced fungi cause blood diseases, nervous system disorders, kidney damage, liver damage, and even cancer Ergot and Aflatoxin Poisoning o Claviceps purpurea fungus causing smut infections on grain crops, cause ergot poisoning after ingesting grains contaminated with the fungus o The toxin can restrict blood flow in the limbs, resulting with gangrene. o It may also cause hallucinogenic symptoms, producing bizarre behavior similar to that caused by LSD. o Aflatoxin is a mycotoxin produced by the fungus Aspergillus flavus, a common mold. It has been found in many foods but is particularly likely to be found on peanuts. Protozoan Diseases of the Digestive System Giardiasis (flagellated protozoan) Amebic Dysentery (Amoebiasis) Balantidial Dysentery (ciliary protozoan) Helminthic Diseases of the Digestive System Platyhelminthes ❖ Tapeworms : Hydatid Disease (Echinococcus granulosus) Nematodes: ❖ Pinworms ❖ Hookworms ❖ Whipworm (Trichuris trichiura) ❖ Ascariasis ❖ Trichinellosis Platyhelminthes Surgical removal Nematodes