Medical Technology Department, Faculty of Science, Islamic University-Gaza

MMICROBBIOLOGY

Dr. Abdelraouf A. ElmanamaDr. Abdelraouf A. ElmanamaPh. D MicrobiologyPh. D Microbiology

2008

Chapter 25Chapter 25Microbial Diseases of the Digestive SystemMicrobial Diseases of the Digestive System

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

Figure 25.1

2008

• >300 species in mouth

• Large numbers in large intestine, including:

• Bacteroides

• E. coli

• Enterobacter

• Klebsiella

• Lactobacillus

• Proteus

Normal Microbiota

2008

Dental Caries

Figure 25.3a, b

2008

Tooth Decay

Figure 25.4

2008

Periodontal Disease

Figure 25.5

2008

• 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

Bacterial Diseases of the Lower Digestive System

2008

Staphylococcal Food Poisoning

Figure 25.6

• Staphylococcus aureus enterotoxin is a superantigen

2008

Shigellosis

Figure 25.8

• Shigella spp. producing Shiga toxin

• Shiga toxin causes inflammation and bleeding

2008

Salmonellosis

Figure 25.9

• Salmonella enterica serovars such as S. enterica Typhimurium

• Mortality (<1%) due to septic shock caused by endotoxin

2008

Salmonellosis and Typhoid Fever Incidence

Figure 25.10

2008

• Salmonella enterica Typhi

• Bacteria spread throughout body in phagocytes

• 1-3% recovered patients become carriers, harboring Salmonella in their gallbladder

Typhoid Fever

2008

Cholera

Figure 25.12

• Vibrio cholerae serotypes that produce cholera toxin

• Toxin causes host cells to secrete Cl–, HCO–, and water

2008

• Usually from contaminated crustaceans or mollusks

• V. cholerae serotypes other than O:1, O:139, and eltor

• V. parahaemolyticus

• V. vulnificus

Noncholera Vibrios

2008

• 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

Escherichia coli Gastroenteritis

2008

• Campylobacter jejuni

• Usually transmitted in cow's milk

Campylobacter Gastroenteritis

2008

Helicobacter Peptic ulcer disease

• Treated with antibiotics

• H. pylori causes stomach cancer

Figure 11.11

2008

Helicobacter Peptic ulcer disease

Figure 25.13

2008

• Y. enterocolitica and Y. pseudotuberculosis

• Can reproduce at 4°C

• Usually transmitted in meat and milk

Yersinia Gastroenteritis

2008

• Grow in intestinal tract producing exotoxin

Clostridium perfringens Gastroenteritis

2008

• Ingestion of bacterial exotoxin produces mild symptoms

Bacillus cereus Gastroenteritis

2008

Mumps

Figure 25.14

• Mumps virus

• Enters through respiratory tract

• Infects parotid glands

• Prevented with MMR vaccine

2008

• Inflammation of the liver

• Hepatitis may result from drug or chemical toxicity, EB virus, CMV, or the Hepatitis viruses

Hepatitis

2008

Hepatitis

Table 25.1

TransmissionCausative agentChronic liver disease

Vaccine

Hepatitis AFecal-oralPicornaviridaeNoInactivated virus

Hepatitis BParenteral, STDHepadnaviridaeYesRecombinant

Hepatitis CParenteralFiloviridaeYesNo

Hepatitis DPareteral, HBV coinfection

DeltaviridaeYesHBV vaccine

Hepatitis EFecal-oralCaliciviridaeNoNo

2008

Hepatitis B Virus

Figure 25.15

2008

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

Figure 25.17

2008

• 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

Mycotoxins

2008

Giardiasis

Figure 25.18

• Giardia lamblia

• Transmitted by contaminated water

• Diagnosed by microscopic examination of stool for ova and trophozoite

• Treated with metronidazole

2008

Cryptosporidiosis

Figure 25.19

• 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

• Cyclospora cayetanensis

• Transmitted by oocysts in contaminated water

• Diagnosed by microscopic examination for oocysts

• Treated with trimethoprim and sulfamethoxazole

Cyclospora Diarrheal Infection

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

Medical Technology Department, Faculty of Science, Islamic University-Gaza

MMICROBBIOLOGY

Dr. Abdelraouf A. ElmanamaDr. Abdelraouf A. ElmanamaPh. D MicrobiologyPh. D Microbiology

2008

Chapter 25Chapter 25Microbial Diseases of the Digestive SystemMicrobial Diseases of the Digestive System

2008

Helminthic Diseases of the Digestive System

Figure 25.21

2008

Tapeworms

Figure 12.27

• 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

Tapeworms

Figure 25.22

2008

Hydatid Disease

Figure 25.23

• Echinococcus granulosus

• Definitive host: Dogs, wolves

• Intermediate host: Sheep and other herbivores; Humans

• Transmitted by ingesting E. granulosis eggs

• Treatment is surgical

2008

Echinococcus granulosus

Figure 12.28

2008

Pinworms

• Enterobius vermicularis

• Definitive host: Humans

• Transmitted by ingesting Enterobius eggs

• Treatment with pyrantel pamoate or mebendazole

2008

Pinworms

Figure 12.29

2008

Hookworms

• Larvae in soil hatched from eggs shed in feces

• Larvae bore through skin; migrate to intestine

• Treated with mebendazole

2008

Hookworms

Figure 25.24

2008

Hookworms

Figure 12.30

2008

Ascariasis

Figure 25.25

• Ascaris lumbricoides

• Lives in human intestines

• Transmitted by ingesting Ascaris eggs

• Treated with mebendazole

2008

Trichinosis

Figure 25.26

• 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

Trichinosis

Figure 25.26

Adult Trichinella spiralis develop, invade intestinal wall of pig, and produce larvae that invade muscles.

Section showing T. spiralis larvae encysted in pig’s muscle tissue (capsule is 0.25 to 0.5 in length).

Human eats undercooked pork containing cysts.

1

2

3

In human intestine, cyst walls are removed, and T. spiralis adults develop. Adults produce larvae that encyst in muscles.

4

Meanwhile, other animals are infected by eating infected meat that has been dumped.

5

Capsule

Section of T. spiralis

Undercooked pork

Garbage, including undercooked or raw pork

T. spiralis adult