Transcript Chapter 25
MICROBIOLOGY Chapter 25 Microbial Diseases of the Digestive System Dr. Abdelraouf A. Elmanama Ph. D Microbiology Medical Technology Department, Faculty of Science, Islamic University-Gaza 2008 Microbial Diseases of the Digestive System • Transmitted in food and water • Fecal-oral cycle can be broken by: • Proper sewage disposal • Disinfection of drinking water • Proper food preparation and storage 2008 The Digestive System 2008 Figure 25.1 Normal Microbiota • >300 species in mouth • Large numbers in large intestine, including: • Bacteroides • E. coli • Enterobacter • Klebsiella • Lactobacillus • Proteus 2008 Dental Caries 2008 Figure 25.3a, b Tooth Decay 2008 Figure 25.4 Periodontal Disease 2008 Figure 25.5 Bacterial Diseases of the Lower Digestive System • Symptoms usually include diarrhea, gastroenteritis, dysentery • Treated with fluid and electrolyte replacement • Infection caused by growth of pathogen • Incubation from 12 hr to 2 wk • Intoxication caused by ingestion of toxin • Symptoms appear 1-48 hr after ingestion 2008 Staphylococcal Food Poisoning • Staphylococcus aureus enterotoxin is a superantigen 2008 Figure 25.6 Shigellosis • Shigella spp. producing Shiga toxin • Shiga toxin causes inflammation and bleeding 2008 Figure 25.8 Salmonellosis • Salmonella enterica serovars such as S. enterica Typhimurium • Mortality (<1%) due to septic shock caused by endotoxin 2008 Figure 25.9 Salmonellosis and Typhoid Fever Incidence 2008 Figure 25.10 Typhoid Fever • Salmonella enterica Typhi • Bacteria spread throughout body in phagocytes • 1-3% recovered patients become carriers, harboring Salmonella in their gallbladder 2008 Cholera • Vibrio cholerae serotypes that produce cholera toxin • Toxin causes host cells to secrete Cl–, HCO–, and water 2008 Figure 25.12 Noncholera Vibrios • Usually from contaminated crustaceans or mollusks • V. cholerae serotypes other than O:1, O:139, and eltor • V. parahaemolyticus • V. vulnificus 2008 Escherichia coli Gastroenteritis • Occurs as traveler's diarrhea and epidemic diarrhea in nurseries • 50% of feedlot cattle may have enterohemorrhagic strains in their intestines • Enterohemorrhagic strains such as E. coli O157:H7 produce Shiga toxin • O = cell wall antigen • H = flagellar antigen 2008 Campylobacter Gastroenteritis • Campylobacter jejuni • Usually transmitted in cow's milk 2008 Helicobacter Peptic ulcer disease • Treated with antibiotics • H. pylori causes stomach cancer 2008 Figure 11.11 Helicobacter Peptic ulcer disease 2008 Figure 25.13 Yersinia Gastroenteritis • Y. enterocolitica and Y. pseudotuberculosis • Can reproduce at 4°C • Usually transmitted in meat and milk 2008 Clostridium perfringens Gastroenteritis • Grow in intestinal tract producing exotoxin 2008 Bacillus cereus Gastroenteritis • Ingestion of bacterial exotoxin produces mild symptoms 2008 Mumps • Mumps virus • Enters through respiratory tract • Infects parotid glands • Prevented with MMR vaccine 2008 Figure 25.14 Hepatitis • Inflammation of the liver • Hepatitis may result from drug or chemical toxicity, EB virus, CMV, or the Hepatitis viruses 2008 Hepatitis Transmission Causative agent Chronic liver disease Vaccine Hepatitis A Fecal-oral Picornaviridae No Inactivated virus Hepatitis B Parenteral, STD Hepadnaviridae Yes Recombinant Hepatitis C Parenteral Filoviridae Yes No Hepatitis D Pareteral, HBV coinfection Deltaviridae Yes HBV vaccine Hepatitis E Fecal-oral Caliciviridae No No 2008 Table 25.1 Hepatitis B Virus 2008 Figure 25.15 Viral Gastroenteritis • Rotavirus • 3 million cases annually • 1-2 day incubation, 1 week illness • Norovirus • 50% of U.S. adults have antibodies • 1-2 day incubation. 1-3 day illness • Treated with rehydration 2008 Figure 25.17 Mycotoxins • Mycotoxins are produced by some fungi: • Claviceps purpurea • Grows on grains • Produces ergot • Toxin restricts blood flow to limbs; causes hallucination • Aspergillus flavus • Grows on grains • Produces aflatoxin • Toxin causes liver damage; liver cancer 2008 Giardiasis • Giardia lamblia • Transmitted by contaminated water • Diagnosed by microscopic examination of stool for ova and trophozoite • Treated with metronidazole 2008 Figure 25.18 Cryptosporidiosis • Cryptosporidium parvum • Transmitted by oocysts in contaminated water • Diagnosed by acid-fast staining of stool or presence of antibodies by FA or ELISA • Treated with oral rehydration 2008 Figure 25.19 Cyclospora Diarrheal Infection • Cyclospora cayetanensis • Transmitted by oocysts in contaminated water • Diagnosed by microscopic examination for oocysts • Treated with trimethoprim and sulfamethoxazole 2008 Amoebic Dysentery • Entamoeba histolytica • Amoeba feeds on RBCs and GI tract tissues • Diagnosis by observing trophozoites in feces • Treated with metronidazole 2008 Amoebic Dysentery Figure 25.20 2008 Amoebic Dysentery Figure 12.18b 2008 MICROBIOLOGY Chapter 25 Microbial Diseases of the Digestive System Dr. Abdelraouf A. Elmanama Ph. D Microbiology Medical Technology Department, Faculty of Science, Islamic University-Gaza 2008 Helminthic Diseases of the Digestive System 2008 Figure 25.21 Tapeworms • Taenia spp. • Transmitted as cysticerci in undercooked meat • Cysticerci may develop in humans • Diagnosed by observing proglottids and eggs in feces • Treatment with praziquantel • Neurocysticercosis may require surgery 2008 Figure 12.27 Tapeworms 2008 Figure 25.22 Hydatid Disease • Echinococcus granulosus • Definitive host: Dogs, wolves • Intermediate host: Sheep and other herbivores; Humans • Transmitted by ingesting E. granulosis eggs • Treatment is surgical 2008 Figure 25.23 Echinococcus granulosus 2008 Figure 12.28 Pinworms • Enterobius vermicularis • Definitive host: Humans • Transmitted by ingesting Enterobius eggs • Treatment with pyrantel pamoate or mebendazole 2008 Pinworms 2008 Figure 12.29 Hookworms • Larvae in soil hatched from eggs shed in feces • Larvae bore through skin; migrate to intestine • Treated with mebendazole 2008 Hookworms 2008 Figure 25.24 Hookworms 2008 Figure 12.30 Ascariasis • Ascaris lumbricoides • Lives in human intestines • Transmitted by ingesting Ascaris eggs • Treated with mebendazole 2008 Figure 25.25 Trichinosis • Trichinella spiralis • Larvae encyst in muscles of humans and other mammals • Transmitted by ingesting larvae in undercooked meat • Treated with mebendazole to kill adults worms 2008 Figure 25.26 Trichinosis Garbage, including undercooked or raw pork 1 Adult Trichinella spiralis develop, invade intestinal wall of pig, and produce larvae that invade muscles. Capsule 2 Section showing T. spiralis larvae encysted in pig’s muscle tissue (capsule is 0.25 to 0.5 in length). 5 Meanwhile, other animals are infected by eating infected meat that has been dumped. Section of T. spiralis Undercooked pork 3 Human eats undercooked pork containing cysts. 4 In human intestine, cyst walls are removed, and T. spiralis adults develop. Adults produce larvae that encyst in muscles. T. spiralis adult 2008 Figure 25.26