2. General characteristics
• Proteus species are widespread in the environment.
• Are normal inhabitants of the human intestinal tract.
• Nitrate-positive.
• Facultative anaerobic.
• Oxidase-negative.
• Ferment glucose ( lac - )
• The two species to most commonly produce infections in humans are
P. mirabilis and P. vulgaris.
4. pathology
• P. mirabilis causes urinary tract infections ( make stones) and
occasionally other infections, such as bloodstream infection and
respiratory tract infections.
• P. vulgaris is probably more frequently implicated in wound and soft
tissue infections than UTIs.
Antibiotic Profile
P. mirabilis is resistant to nitrofurantoin(used for UTI).
P. vulgaris is generally more resistant to various antibiotics
(specifically ampicillin, amoxicillin..etc).
5. P. mirabilis
Indole test positive .
(to convert tryptophan into indole)
P. Vulgaris
Indole test negative .
• They have ability to swarm over the
surface of media. ( motile )
• H2S positive
• Non Lactose ferment.
• Urease positive.
• Oxidase negative
• Catalase positive.
• phenylalanine deaminase
10. 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
11. 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
12.
13. 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).
14. 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
15. 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
16. 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.
17. 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).
