Microorganism Spread, Intoxication, Dysentery

Microorganism Spread

Intoxication occurs when illness is caused by ingesting toxins produced by bacteria in food.
Bacteria multiply in improperly stored food and release toxins.
Symptoms appear rapidly due to direct toxin ingestion.
The incubation period is short, with symptoms appearing within a few hours.
Bacillus cereus contaminates starchy foods and produces toxins.

Dysentery is a severe condition where microorganisms damage the GI tract, leading to blood and pus in the stool.
It indicates a serious, invasive infection.
Dysentery outbreaks are more severe than typical watery diarrhea.

Hektoen enteric agar is used to test for Shigella bacteria.
The agar contains lactose.
Enterobacteriaceae family: A broad family of bacteria.
- Divided based on lactose fermentation: coliforms (ferment lactose) and non-coliforms (do not ferment lactose).
- Shigella is a non-coliform.
- Hektoen plates are designed to identify non-lactose fermenters like Shigella by showing no color change.
- Salmonella is also a non-coliform and can be tested using Hektoen enteric agar.

Shigella was discovered by scientist Shiga, with the toxin named after him.
Different Shigella species exist, including sonnei, dysenteriae, and flexneri.
Shigella dysenteriae is the most dangerous but is rare in the United States.
Shigella flexneri is more common in other countries; some cases have caused brain inflammation and death, especially in children.
In the US, sonnei is the most common species found.

Shigellosis primarily affects young children (toddler age).
Adults can also contract it.
Transmission occurs through the fecal-oral route, meaning ingestion of fecal matter.
- Indirect transmission via house flies, fomites (contaminated objects), and contaminated water.
The infectious dose (ID50) is very low, meaning only a small amount of bacteria is needed to cause infection.
Antacids can lower stomach acidity, potentially reducing the ID50.
Dysentery is the main symptom.

Patients can be carriers, either symptomatic or asymptomatic.
Carriers can shed bacteria in their stool for up to a month after recovery (convalescent period).
Typhoid Mary: A famous Salmonella carrier who spread typhoid fever while working as a cook.

Shigella manipulates host cells by hijacking the cytoskeleton (internal protein network that maintains cell shape).
Shigella forms a pocket around itself to invade GI tract epithelial cells.
After diving in, pathogens manipulate the cytoskeleton to facilitate invasion of the lining of the GI tract, leading to multiplication.
Shigella kills cells in the GI tract, leading to abscess formation (damaged cells, blood, and pus).
Shigella dysenteriae produces Shiga toxin, which is potent and kills gastrointestinal epithelial cells and renal cells (kidney cells), potentially leading to kidney failure.

E. coli O157:H7 is a strain that produces a toxin similar to the Shiga toxin.
Associated with outbreaks from uncooked produce like spinach and romaine lettuce.
Can also be contracted from raw (unpasteurized) milk and undercooked beef.
Pasteurization involves heating milk to kill harmful bacteria.

Salmonella is also in the Enterobacteriaceae family, is a rod-shaped bacterium with numerous flagella (motile), and is a non-coliform (cannot ferment lactose).
Reservoir: The natural habitat for bacteria which includes the GI tracts of various animals, including cold-blooded animals like reptiles, and also humans.
Thousands of subspecies exist, preventing full immunity.
Salmonella enterica is the main species causing illness in the United States (salmonellosis, or food poisoning).
Typhoid fever is more common abroad.
Salmonella has three names: genus, species, and subspecies, listed in Bergey's Manual.

Symptoms include watery diarrhea, high fever, headache, chills, and nausea, lasting for a couple of days.
Commonly contracted from chicken.
Salmonella manipulates host cells and invades the GI tract lining, causing inflammation.
Invasions are proteins that facilitates the invasion of the bacteria into the GI tract lining.
The immune system's response contributes to symptoms.
Elderly individuals are more vulnerable to severe illness.

Sources include poultry (chicken and turkey), reptiles, uncooked eggs, and exposure to animals.
Proper cooking of foods is essential for prevention.
Freezing food may not eliminate Salmonella.
Children under five and the elderly are particularly vulnerable.
Treatment focuses on staying hydrated.

Mary Mallon (Typhoid Mary) was a chronic carrier of Salmonella typhi (typhoid fever).
She worked as a cook for wealthy families, unknowingly infecting them.
Three people died from her cooking.
She was isolated multiple times but denied being a carrier.
Public health officials had to balance individual rights with public safety.

Giardia is a protozoan (eukaryote) with flagella.
Beavers are the reservoir; transmission occurs through contaminated water while camping.
Giardia attaches to the intestines, preventing nutrient absorption, resulting in greasy diarrhea and hydrogen sulfide gas production (leading to belching).
Species named Giardia lamblia.