Chapter 21: Rickettsias, Chlamydias, Spirochetes, and Vibrios Flashcards
What are two types of relapsing fever in the genus Borrelia including their causes and vectors
1) Louse-borne relapsing fever
- Caused when Borrelia recurrentis is transmitted between humans by the human body louse
- Lice become infected with B. recurrentis when they feed on infected humans, the only reseroir for this spirochete
2)** Tick-borne relapsing fever**
- Several Borrelia species can cause this disease
- Transmitted to humans by soft ticks of genus Ornithodorus
- Ticks and rodents are common reservoirs of infections
Spirochetes: Borreila
What are both types of relapsing fever characterized by and treatment
- Characterized by recurring episodes of septicemia and fever
- Due to the body’s repeated efforts to remove the spirochetes
- Successful treatment is with doxycyline or erthromycin
Spirochetes: Borrelia
Describe Leptospira
- Motile by means of two axial filaments
- Obligately aerobic bacteria
- Found in numerous wild and domestic animals (ex. rats, raccons, foxes, horse, cattle, pigs)
- Grows in kidney tubules
- Grown on special media enriched with bovine serum albumin or rabbit serum
Spirochetes: Leptospira interrogans
Describe Leptospriosis
- Caused by L. interrogans
- Zoonotic in nature
- One end of the spriochete is hooked like a question mark
- Humans contract disease via contact with infected urine or environment
- Leptospira enters cuts/abrasions in skin and mucous membranes
- Travels via bloodstram throughout the body
- Infection may lead to kidney dysfuntion
- Bacteremia eventually resolves; spirochetes found only in kidneys
- Eradication impractial due to the varous animal reservours
- Vaccine available for animals
Spirochetes
How do humans contract Leptospirosis
- Via contact with infected urine or enviroment
- Leptospira enters cuts/abrasion in skin mucous membranes
Spirochetes: Leptospira
How does Leptospira travel?
- Travels via the bloodstream throughout the body
- Infection may lead to kidney dysfunction
- Bacteremia eventually resolves then the spirochetes will only be found in the kidneys
Spirochetes: Leptospira
What are three genera of the more pathogenic vibrios
- Vibrio
- Campylobacter
- Helicobacter
Vibrios
Contrast Vibrio with enteric bacteria in terms of their flagella and biochemical properties.
Compare: Vibrios and enteric bacteria both have O polysacharide antigens
Contrast: Vibrios are oxidase positive with polar flagellum
Describe the action of cholera toxin in causing cholera
Step 1) Cholera toxin binds to membrane of epithlial cell
Step 2) Portion of toxin (part A) enters the cell
Step 3) A1 activates adenylate cyclase (AC)
Step 4) Cyclic AMP (cAMP) is synthesized
Step 5) Cyclic AMP stimulates cell to secrete Cl-, Na+, and other electrolytes
Step 6) Water follows electrolytes into lumen
Name three species of Vibrio and describe the resulting diseases
- Vibrio cholerae causes cholera (particularly O1 El Tor strain)
- Vibrio parahaemolyticus results from ingestion of shellfish; causes cholera-like gastroenteritis
- Vibrio vulnificus causes spepticemia due to consumption of contaminated shellfish, and wound infections can result from washing wounds with contaminated seawater
List several possible reserviors of Campylobacter jejuni
Campylobacter jejuni is zoonotic - many animals serve as reservoirs for the bacteria including:
- Poultry
- Dogs
- Cats
- Pigs
- Cattle
Humans become infected by consuming contaminated food, milk, or water
Poultry is the most common source of infection
What is the most common source of infection for Campylobacter jejuni bacteria
Poultry is the most common source of infection
Describe the pathogenesis of Campylobacter jejuni
- Bacteria possesses adhesins, cytotoxins and endotoxins
- Infections produce self-limiting bloody and frequent diarrhea that may last 7-10 days
- Appears to colonize and invade jejunum, ileum and colon producing bloody lesions
Describe the pathogenesis of Helicobacter pylori
- Produces numerous virulence factors that enable it to colonize the stomac
- Proteins that inhibits acid production in stomach
- Flagella help the pathogen to burrow through the stomach lining
- Adhesins facilitate binding to gastric cells
- Exotoxins - Cytotoxin-associated gene A product (CagA)
- Enzymes like urease that help neutralize stomach acid
Discuss the major change in medical opinion concerning the cause of peptic ulcers
- H. pylori causes gastritis and most peptic ulcers, erosions of the mucus membrane of the stomach or small intestine
- Prevailing viewing that - stress, alcohol consumption, spicy food, or excess stomach acid production cause peptic ulcers
- Robin Warren and Barry Marshall detected Helicobacter colonizing the majority of their patients’ stomachs
Pathogenic Gram negative Vibrios: Helicobacter pylori
Dr. Marshall drank one of his cultures of Helicobacter. He developed painful gastritis and was able to isolate H. pylori in his stomach.
Describe the effect of Helicobacter pylori on the lining of the human stomach.
The formation of a peptic ulcer begins when H. pylori (protected by urease) burrows through the stomach’s protective layer of mucus to reach the underlying epithelial cells
1) Where the bacteria attach to the cells’ cytoplasmic membranes and multiply. A varitey of factors - the triggering of inflammation by bacterial exotoxin and destruction of mucus producing cells by the bacteria- causes the layer of mucus to become thin
2) Allowing acidic gastric jusic to digest the stomach lining, H. pylori gains access to the underlying muscle tissue and blood vessels
3) Those bacteria that are phagocytized survive in part through the actions of catalase and superoxide dismutase, enzmes that neutralize part of the phagocytes’ killing mechanism
