1. Gram Negative Bacteria
Digging Deeper into Microbial Life
Part 2 of 3

2. Gram Negative Bacteria
Stain red*
Their thin layer of peptidoglycan is surrounded by a cell wall
Most are harmful to humans
Produce endotoxins that are often deadly – even after the bacteria is destroyed
Gram negative microbes cause the most and the worst cases of septicemia**
*Using gram staining technique. Note: due to different photography techniques, you may note colors other than expected.
**Septicemia is also known as sepsis, septic shock and bacteremia. It is sometimes referred to “blood poisoning” when speaking with laypeople.

3. Gram Negative Bacteria Types
Pseudomonas aeruginosa
Klebsiella pneumoniae
Haemophilus influenzae
Bordatella pertussis
Legionella pneumoniae

4. Pseudomonas aeruginosa
Opportunistic aerobic bacillus
Found in most non-sterile water
Causes respiratory tract infections
Most:
Strains are antibiotic resistant
Common cause of nosocomial infection in patients hospitalized for over one week
Common microbe cultured in mucus from cystic fibrosis patients
Commonly cultured microbe on respiratory care equipment

5. P. aeruginosa Has characteristic fermented fruit odor
Often described as fetid by the NBRC
Creates a blue – green pigment called pyocyanin
Augments color of pus
Augments color of mucus

6. P. aeruginosa Blue pigment on an agar created by p. aeruginosa
Green pigment on an agar created by p. aeruginosa
The colors can be quite interesting which contrasts the strong, fetid odor the microbe creates.

7. Klebsiella pneumoniae
Facultative anaerobe
Opportunistic
Often antibiotic resistant
Common cause of pneumonia
Leads to small areas of lung destruction
Leads to abscesses
Creates mucus that looks like red currant jelly

8. Haemophilus influenzae
Facultative anaerobic bacillus
Found in over 75% of upper respiratory systems
Opportunistic
Cause of upper respiratory infections (URI)
Cause of epiglottitis in children
Does NOT cause the flu (that’s a virus!)
Requires very specific culturing techniques
Epiglottitis article:

9. Bordatella pertussis Coccobacillus
Cause of pertussis, aka whooping cough
Characterized by long inhalation and choking cough
Produces thick, clear mucus
Cough and mucus production may last for months
Children receive immunization
Teens and adults become ill as immunization does not work against new strains
Vaccine is in new tetanus shots to protect older population

10. B. pertussis
Healthcare workers often swabbed to check for colonization of Bordatella pertussis. Illustration shows procedure for testing for the microbe.

11. Legionella pneumoniae
Aerobic bacillus
Cause of Legionnaire’s disease
Pneumonia
Victims get contaminated by water supply
Often from inhaling steam from showers or hottubs
Hospitals, hotels, and cruise ship contamination may cause an outbreak
CDC information on Legionnaire’s disease:

12. Gram Negative Summary
Like gram positive bacteria, gram negative have the potential to cause serious pulmonary illness.
These microbes have a higher chance of being more serious
Tend to have more powerful toxins
Are less susceptible to antibiotics.
Their endotoxins may continue to damage the host after the death of the bacteria.

13. Study Tool
Gram Positive
Staphylococcus aureus
Streptococcus pneumoniae
Corynebacterium diphtheriae
Bacillus anthracis
Clostridium botulinum
Clostridium tetani
Gram Negative Pseudomonas aeruginosa Klebsiella pneumoniae Haemophilus influenzae Bordatella pertussis Legionella pneumoniae

14. Next Steps
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