Micro 4.6 Gram negative rods

What are Gram Negative Bacilli?

A diverse group divided into two main categories around the fermentation of lactose.

What are the two categories of Gram Negative Bacilli?

Coliforms and Non-coliforms.

Where can Gram Negative Bacilli be found?

In a variety of environments.

What oxygen conditions do many Gram Negative Bacilli prefer?

Many are anaerobic or facultative anaerobes.

Where is endotoxin found?

ONLY in Gram - bacteria.

What acts as an additional boundary outside the cell wall?

The outer membrane.

What do porins do?

Allow for movement of small molecules across and into the periplasmic space.

What is the outer membrane resistant to?

Many antibiotics, drying, and detergents.

What is Lipid A?

The toxic component of endotoxin released when the outer membrane is damaged.

What determines the degree of signs/symptoms caused by endotoxin?

The amount of endotoxin released.

What symptoms can endotoxin cause?

Fever and inflammation.

What causes endotoxic shock?

Gram - sepsis.

What does endotoxic shock involve?

Massively complex and uncoordinated immune response.

What results from high TNF activation in endotoxic shock?

High fever and vascular damage.

What does vascular damage from endotoxin lead to?

Ischemia and eventually tissue/organ death.

What are common secondary manifestations of endotoxic shock?

Petechial hemorrhages, tachy/bradycardia, ARDS, and loss of blood pH regulation.

What is the mortality rate of endotoxic shock in clinical settings?

Roughly 40 - 60%.

What kind of bacteria is E. coli?

A coliform.

Why is E. coli a model organism?

Its entire genome is known and it is used to explore genetics and evolution.

Where is E. coli commonly found?

As a common commensal in many animals.

What does the presence of E. coli in food or water indicate?

Fecal contamination.

How many different subtypes of E. coli are there?

100.

What are examples of E. coli subtypes?

Enterotoxigenic, Enteroinvasive, Enteropathogenic, and Enterohemorrhagic - O157:H7.

What toxin does E. coli O157:H7 produce?

Shiga toxin.

What syndromes can E. coli cause?

Dysentery and Hemolytic Uremic Syndrome.

What is S. enteritidis?

A zoonotic pathogen from birds and reptiles.

What does S. enteritidis cause?

Salmonella food poisoning.

What is S. typhi?

A human-only pathogen.

What disease does S. typhi cause?

Typhoid fever.

What can typhoid fever lead to?

Perforation of the intestines, septic shock, and dysentery.

What disease does Vibrio cholerae cause?

Cholera.

What is the shape of Vibrio cholerae?

Comma shaped.

Where is Vibrio cholerae commonly found?

In sewage, mixed salt/fresh water, and contaminated seafood.

What is the infectious dose (ID) of Vibrio cholerae?

High - ~10,000,000 cells.

What does cholera toxin do?

Causes secretion of electrolytes into the intestinal lumen.

What follows salt in the intestine?

Water - by osmosis.

What is the hallmark symptom of cholera?

"Rice water stool."

What is the primary treatment for cholera?

Rehydration.

Is there a vaccine for cholera?

Yes.

What does Helicobacter pylori cause?

Gastric and intestinal ulcers.

What was believed to cause ulcers before 1982?

Stress.

How common is Helicobacter pylori?

Common resident in 80% of the population.

What cancers are chronic ulcers linked to?

Esophageal, gastric, and colorectal cancers.

Where are Pseudomonas spp. commonly found?

In the environment such as soil and water.

Where are Pseudomonas spp. common contaminants?

In hospitals.

What shape are Pseudomonas spp.?

Gram negative, free-living, bacillus shaped cells.

What do most Pseudomonas species produce?

Water soluble pigments (pyocyanin) and distinct odors.

What are Pseudomonas spp. used for industrially?

Bioremediation - adapting to environments and breaking down complex compounds.

What is P. aeruginosa the most common cause of?

Nosocomial infection.

What does P. aeruginosa secrete?

Glycocalyx slime.

What does glycocalyx slime do?

Prevents phagocytosis and allows biofilm formation.

Where does P. aeruginosa colonize?

Ventilators, IV equipment, etc.

What pigment does P. aeruginosa produce?

Pyocyanin - blue-green fluorescent pigment.

What infections does P. aeruginosa cause in hospitals?

UTI and LRI.

Who is at high risk for P. aeruginosa infection?

Burn and CF patients.

What are two external conditions caused by P. aeruginosa?

Swimmer's Ear and Hot tub folliculitis.

How do skin infections from P. aeruginosa occur?

Microbes enter through traumatized skin or hair follicles.

What is the usual treatment for P. aeruginosa?

Colistin.