Chapter 25 Infections of the Gastrointestinal Tract

GI tract

extends from mouth to anus, direct contact with food

accessory organs

do not directly contact food

salivary glands, liver, gallbladder

mucosa-associated lymphoid tissue (MALT)

tonsils, appendix, Peyer’s patches

“sample” the environment by phagocytosis; present findings to lymphocytes

microbiome

most diverse and densely populated part of the body, plays an essential role in our health and in disease

mild symptoms of a GI infection

diarrhea

gastritis→ inflammation of the stomach

enteritis→ inflammation of intestines

gastroenteritis→ inflammation of stomach and intestines

severe symptoms of a GI infection

dysentery→ infectious gastroenteritis w/ abdominal pain

hypovolemic shock→ low blood volume or blood loss from severe dehydration

dental plaques

Biofilms of Streptococcus mutans, which attach to the tooth

Carbohydrate-dependent; sucrose is cariogenic (good at forming dental caries)

Fermentation of sugar leads to acid production

viral gastroenteritis

sudden onset: watery diarrhea, nausea/vomiting, cramps, bloating

Complications: dehydration; severe cases occur in very young and elderly individuals

spreads via the fecal-oral route

rotavirus

common in babies and infants in the fall and winter

norovirus

adult infection, responsible for outbreaks (cruise ships, schools)

hepatitis

inflammation of the liver, caused by non-related viruses

hepatitis A virus

Fecal-oral transmission, usually an acute infection (symptoms within a short amt of time)

hepatitis B virus

spreads through direct contact with infected body fluids

acute infection→ 50% of cases are asymptomatic but infectious

chronic infection→ after 6 months of no symptoms; continued presence of the infectious antigen in the blood

lifelong infectious illness leads to scarring of the liver (cirrhosis)

hepatitis C virus

DNA virus; transmitted by blood-to-blood contact (intravenous drugs)

acute→ usually undiagnosed; antivirals effective

chronic→ 50% of individuals do not know they are infected; accumulation of liver damage occurs

no vaccine available

hepatitis D virus

Can’t replicate on its own (needs Hep B to hitch a ride)

fecal-oral transmission

helicobacter pylori

Gram-negative, curved rod; transmitted person-to-person via saliva

produces urease; leads to peptic ulcer disease; treated with antibiotics

foodbourne infection

After ingestion of the pathogen, colonization occurs, disease acts in days to weeks

food poisoning

Driven by ingestion of toxin, acts immediately

staphylococcal food poisoning

ingestion of endotoxin produced by S. aureus; rapid onset (within a few hours)

listeriosis

listeria monogenous (gram positive bacilli) from unpasteurized dairy products

Clostridium perfringens gastroenteritis

Gram-positive bacilli that form endospores, from meats and meat stews that are contaminated

campylobacter jejuni

Gram-negative, leading cause of diarrhea in the US, bacteria burrow into the epithelial cells of the intestines

Guillain-Barré syndrome → rare autoimmune disease b/c surface of the pathogen resembles lipids seen in the nervous system

bacterial dysentary

In severe cases causes stool w/ mucus and blood

The shiga toxin disrupts protein synthesis in the host cell, killing it

escheria coli gastroenteritis

Gram-negative bacilli, caused by enterotoxin found in water, vegetation, and soil

enteropathogenic E. coli (EPEC)

major cause of diarrhea in developing countries, fatal in infants

enteroinvasive e. coli (EIEC)

likes to get into the cell, similar to shigella

enterotoxigenic e. coli (ETEC)

secretes an exotoxin that causes diarrhea, fatal for children under 5

enterohemorrhagic E, coli (EHEC)

cause of serious outbreaks, shiga-toxin-producing E. coli

e. coli 0157: H7

progresses to severe bloody diarrhea, hemolytic uremic syndrome, do NOT use antibiotics, leads to a massive release of toxin when cell lysis occurs

salmonella gastroenteritis

causes by s. enterica which is found in raw eggs and poultry

s. typhi

causes typhoid fever

Clostridioides difficle

Gram-positive, healthcare-acquired infection

develops following antibiotic treatment

can progress to pseudomembranous colitis (colon inflammation)

treated by fecal transplant

Giardia lamblia - giardiasis

Cysts are ingested, and trophozoites are released

Drink purified water to prevent

does NOT grow on blood agar

cryptosporidiosis

Ingestion of oocysts found in contaminated water

Swimming pool chlorination is not effective

fecal-oral transmission