Pseudomonas aeruginosa (PA):
Gram-negative bacillus found widely in nature, in soil and water.
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The genus Pseudomonas >140 species,> saprophytic & >25 species are associated with humans. Most known to cause disease in humans are associated with opportunistic infections.
⬆️ MR : ⬇️ host defenses, resistance to ABX & production of extracellular enzymes & toxins.
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Often found in water in sinks & can contaminate respiratory equipment, which can serve as an environmental reservoir, especially in ICUs. Is the most serious pathogen causing ventilator-associated pneumonia & remains the most important pathogen in patients with CF.
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The green pigment produced by Pseudomonas aeruginosa is easily seen on Mueller-Hinton agar plate used for disk antimicrobial susceptibility testing.
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Resistance mechanism
-AmpC beta-lactamase
-Extended-spectrum beta-lactamase
-Downregulation of the outer membrane protein OprD, a carbapenem-specific porin
-Multidrug efflux pumps
-Ability of the organism to form a biofilm
-Possible transfer of a 16S rRNA methylase gene.
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Virulence Factors of Pseudomonas aeruginosa:
The three major types of virulence factors in P. aeruginosa include; factors involved in attachment and motility, factors involved in colonization, & factors involved in chronic infection.
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Pathogenesis of Pseudomonas aeruginosa:👇👇👇
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Rx of P. aeruginosa Infec:
A large SR & MA found that the most effective measures for preventing the development of an MDR inf in the ICU was combination of standard care (hand hygiene & contact precautions), antimicrobial stewardship, environmental cleaning, & source control.
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Common antibiotics that are used as first-line therapy include carbapenems, cephalosporins, aminoglycosides, and fluoroquinolones.
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Oral antibiotics:
Fluoroquinolones are the only antibiotic class available as an oral formulation that is reliably active. Ciprofloxacin: dosed 750 mg orally x 12 hours & levofloxacin 750 mg x daily. For PA alone infection, levofloxacin has no advantage over ciprofloxacin.
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Multidrug-Resistant PA Infections:
A significant clinical challenge and can substantially complicate the approach to selection of optimal antibiotic therapy.
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Combination antibiotic therapy is not routinely recommended for infections caused by DR-PA if in vitro susceptibility to a first-line antibiotic (i.e., ceftolozane-tazobactam, ceftazidime-avibactam, or imipenem-cilastatin-relebactam) has been confirmed.
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Nebulized antibiotics for the treatment of respiratory infections caused by DR-P aeruginosa is not recommended.
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Reference:
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