Gram Negative Bacilli

Vibrio cholerae traits

curved, Gram negative, facultative anaerobe, motile

Describe the symptoms of cholera. How is it transmitted?

• 75% of those infected will never show symptoms but will act as carriers

• For those who do show symptoms, usually 1-5 days

  • Severe, extremely (rice watery) watery diarrhea

  • Fluid loss can be rapid

  • Severe cases can cause death in ~3 hours (dehydration)

  • No fever 

• ~50% mortality if untreated

• Transmitted fecal-oral human to human (contaminated food or water)

Is Vibrio invasive? Does it produce a toxin?

• Not invasive but it does produce a exotoxin → choleragen

  • induces cells to pump water OUT of cell (draining fluid out of the body)

How is cholera best treated? Prevented?

• Best treated through HYDRATION (m important) & antibiotics 

  • hydrate intravenously (IV, saline)

  • hydrate orally (drink water, but keep in mind that pure water will pass through the intestines; needs to be absorbed in upper digestive tract)

  • well-treated cases mortality ~1%

• Prevention through good hygiene/sanitation; vaccine available - not very effective

Where do V. cholerae infections come from?

Infections come from human to human contact (contaminated food or water)

Pseudomonas traits

• extremely hardy, widespread 

• Gram negative, obligate aerobic rods

• produce colored and fluorescent pigments

• “fruity” odor

• usually motile due to polar flagella

What makes Pseudomonas poor pathogens in most cases? BUT why are they particularly difficult opportunistic pathogens?

• since they’re opportunistic, Pseudomonas is readily killed by a healthy immune system

  • rarely cause infections in healthy people; needs a weakened host to thrive

• produces exotoxins of the same type as diphtheria toxin

  • but not as strong

DIFFICULT BECAUSE

• grows on a lot of different food sources

• resistant to many types of antibiotics/disinfectants

What are the most common types of patients affected by Pseudomonas infections?

• 1 in 10 nosocomial infections

• burn victims (damage prevents immune system access)

• immune compromised (AIDS patients, cancer patients)

• cystic fibrosis (leading cause of pneumonia in CF patients)

Why are the exotoxins of Pseudomonas aeruginosa a concern? How can they treated?

• exotoxins cause local cell damage WHICH causes bacteria to gain entry to blood, cases sepsis and shock due to exotoxins

• treated through antibiotics

Legionella traits

• accidental pathogen

• Gram negative, obligate aerobic rods

• extremely fastidious (difficult to culture)

  • require specific media & are slow-growing

What does "fastidious" mean in microbiology?

• difficult to culture

• requires specific media & are slow-growing

What organism does Legionella normally infect?  What human cell does it resemble?

• Legionella normally infects amoeba

• Legionella resembles macrophages in the human body (ie; lungs)

What are they symptoms of Legionnaires disease?  Which symptom stands out from other pneumonias? 

• Symptoms include

  • 2-14 day incubation

  • Very high fever (104-105°F), shaking chills

  • Dry cough

  • Sometimes diarrhea, nausea, vomiting

  • Fluid in the lungs (X-ray)

• Pontiac fever

  • Mild, self-limiting disease

  • Fever, muscle aches, fatigue

  • Not clear why some get this version

How is Legionella transmitted?  Is it from humans, animals, or the environment?

• Transmitted through inhalation

  • from contaminated air supplies (growth of Legionella in air conditioning systems) → environment

How is Legionnaires' disease diagnosed? Treated?

• Diagnosed by antibody staining of sputum samples, DNA test (b/c hard to culture)

• Treated through antibiotics