Pseudomonas is a Gram-negative, motile bacteria that is a major human pathogen. It commonly colonizes the skin and intestines of healthy individuals but can cause disease in immunocompromised patients. Pseudomonas produces pigments like pyocyanin and pyoverdin that inhibit other bacteria and cause tissue damage. It is resistant to many antibiotics but can be treated with drugs like carbapenems, aminoglycosides, fluoroquinolones, and certain cephalosporins depending on the infection site. Pseudomonas uses factors like pili, flagella, alginate, and toxins to cause both local and systemic infections, making it an important nosocomial pathogen.

1. Pseudomonas
For NEET PG

2. General Characteristics
● Gram negative, non sporing, motile aerobic baciilli with polar flegella
pseudomonas aeuginosa is a major human pathogen.
● Grows well at 37-42 degree C, growth at 42 degree C differentiates
pseudomonas aeuginosa from other pseudomonas spp.
● Pseudomonas aeruginosa colonised normal humans in small intestine and
skin.
● It causes disease in humans with abnormal host defense's especially in
patients with neutropenia.
● Mostly non-capsulated but strains isolated from patients with cystic fibrosis
gives mucoid colony as a result of overproduction of slime layer of alginate.

3. Pigment production
● Produces water soluble pigments which diffuses freely into the medium,
inhibits other bacteria and cause tissue injury.
● Pyocynin: bluish green pigment produced only by pseudomonas aeruginosa.
● Pyoverdin(fluorescein): gives greenish yellow colour to the colony
● Pyorubin: Impart red colour.
● Pyomelanin: Impart brown black colour.

4. Treatment
1. Pseudomonas posses a number of drug resistant plasmids conferring them
resistance to several antibiotics.
● Antipseudomoal drugs:
Extended spectrum penicillins-carbenicilline, piperacilline, ticarcilline
Extended spectrum cephalosporine:
3rd generation: ceftazidime, cefoperazone
4th generation: cefepime, cefpirome

5. Cont.
● Carbepenems: Imipenem, Meropenems
● Monobactam: aztreonam
● FLUOROQUINOLONES: Ciprofloxacin, levofloxacin
● Aminoglycosides: amikacin,tobramycin,gentamicin
● Drug of choice: aminoglycosides+penicillins except.
In CNS infection: ceftazidime+/- Aminoglycosides
In UTI: Ciprofloxacin
In malignant otitis externa: cprofloxacin or cephalosporine or
carbapenems

6. Resistance
● Resistant to common antiseptics and disinfectants such as quarentary
ammonium compounds,chlorxylenols hexachlorophans, dettol and cetrimides
and it grows in bottles containing these antiseptics and disinfectants.
● Cetrimide agar is infact used as selective media for growing pseudomonas.
● Sensitive to acids, beta glutaraldehyde, silver salts and strong phenolic
disinfectants.
● Most common organism causing infection in burn patients and silver
sulphonamide compounds are used as topical cream in burn patients.

7. Antigenic structure and Virulence factors
● Pili/fimbrae helps in colonisation and single polar flagella helps in
chemotactic movement towards host.
● Alginate an exopolysaccharide responsible for mucoid colony from patients
with cystic fibrosis, helps in bio-film formation and thus adhesion with host
mucosal cell and protection from immune cells.
● Lipopolysaccharide layer of cell wall responsible for endotoxic property of
organism.

8. Toxins
Diffusible toxins(secreted by type-II secretory system): Exotoxin A an
important enzyme which acts like diphtheria toxin and inhibits host protein
synthesis by inhibiting EF2.
Other diffusible toxins are protease, phospholipase C, elastase, hemolysins.
Non diffusible toxins(secreted by type-III secretory system): Exotoxin S and
T- bifunctiobal enzyme with GTPase and ADP-ribosyl transferase activity.
Exotoxin-U a phospholipase and Exotoxin Y an adenyl cyclase

9. Local, skin and soft tissue infection
● Most common cause of osteo chondritis of dorsum of the foot after penitrating
wound.
● MC agent causing infections in burn.
● Folliculitis in hot tub users
● Extended period of swimming leading to swimmer's ear in children's.
● Malignent otitis external in elderly and diabetic patients.
● Pathognomonic skin leishions called Icthyma gangrenosum which occurs
singly or in small numbers in perinim, extremities and buttocks.

10. Systematic infections
● P. aeruginosa related nosocomial infections occurs in patients undergoing
machanical ventilator(ventilator associated pneumonia), on intravascular or
urinary catheter(catheter related infections) chemotherapy, antibiotic
treatments etc.
● These infections occurs due to initial colonisation and subsequent infection.
● Major pathogen causing lung infections in patients with cystic fibrosis.
● Bacteremia leading to sepsis and septic shock.
● Native valve endocarditis in I/V drug abusers