Pseudomonas aeruginosa is a gram-negative bacillus found in soil, water, and plants that can cause opportunistic infections in humans. It is intrinsically resistant to many antibiotics and can acquire additional resistance. P. aeruginosa commonly causes nosocomial infections through growth in water sources like IV tubing. It produces toxins and enzymes that contribute to pathogenesis and can cause both localized infections like pneumonia or bacteremia as well as systemic illness.

1. Gram-negative bacilli
Pseudomonas

2. Pseudomonas: Other Opportunistic
Gram-negative Bacilli
• Family Pseudomonadaceae, which contains over 200 species.
• Most of them are pathogenic to plants, insects, and reptiles.
• A few species cause disease in humans. P. aeruginosa is the most important.
• These organisms are notorious because of the potency to develop innate
resistance to many antibiotics.
• Are obligatory aerobic.
• Non fermented Sugar.
• Mostly oxidase-positive bacteria.
• Most of them are motile by presence of one or two flagella

3. Pseudomonas: Other Opportunistic
Gram-negative Bacilli
• is found in soil, water, plants, and animals.
• it may colonize healthy humans without causing disease(normal flora) .
• Is major cause of nosocomial infections.
• P. Aeruginosa can even grow in laboratory water baths, hot tubs, wet IV tubing,
and other water-containing vessels. This explains why the organism is responsible
for so many nosocomial infections
• P. aeruginosa secretes a capsule-like polysaccharide called alginate.
• P. aeruginosa produces numerous toxins
• Has ability to grow at 42C.
Pseudosel
Agar

5. Antigenic Structure and Toxins
Pathogenesis is based on multiple virulence factors:
endotoxin, exotoxins, and enzymes. adhesins, pili.
1. Its endotoxin, like that of other gram-negative bacteria, causes the
symptoms of sepsis and septic shock.
2. The best known of the exotoxins is exotoxin A, which causes tissue
necrosis. It inhibits by the same mechanism as diphtheria
eukaryotic protein synthesis exotoxin (Corynebacterium).

6. Antigenic Structure and Toxins
Strains of P. aeruginosa that have a
“type III secretion system”
are significantly more virulent than those that do not. This secretion
system transfers the exotoxin from the bacterium directly into the
adjacent human cell, which allows the toxin to avoid neutralizing
antibody.
- cause cell death or interfere with the host immune response to
infection

7. Clinical significance
P. aeruginosa causes both localized and systemic illness
1. Localized infections:
• These may occur in the eye
• Ear elderly diabetic patients or trauma patients
• skin (wound sepsis)
• Urinary tract (particularly in hospitalized patients)
• Respiratory tract (pneumonia)
• Gastrointestinal tract
• meningitis

8. Clinical significance
• 2. Systemic infections:
• Infections reflecting systemic spread of the organism include
bacteremia (most common in patients whose immune system has
been compromised).
• secondary pneumonia.
• bone and joint infections.
• Endocarditis.

9. Antibiotic Resistance
• P. aeruginosa is intrinsically resistant to many antimicrobial agents, and can
acquire additional resistance to many other antimicrobial agents via
horizontal gene transfer or mutations.
• The mechanisms responsible for intrinsic
resistance include various multidrug
efflux pumps (affecting β-lactams,
fluoroquinolones, macrolides,
and other antibiotics).

10. sources
1.Lippincot – chapter 13. third ed.
2. Jawetz-chapter 15. 28th ed.
3. Levinson chapter-18. 14th ed.

11. Thank you