Microbiology
Summary
Pseudomonas aeruginosa is an oxidase-positive, catalase-positive, gram-negative bacillus that thrives in aquatic environments. Unique features include its blue-green pigment production and a distinctive grape-like odor.
P. aeruginosa is a major cause of gram-negative nosocomial pneumonia and pulmonary infection in cystic fibrosis patients. It also has the ability to cause osteomyelitis, particularly in IV drug users and diabetics, and can be fatal in burn patients. Additional risks associated with Pseudomonas include urinary tract infections, skin lesions such as hot tub folliculitis, otitis externa (swimmer's ear), and ecthyma gangrenosum (a skin infection characterized by necrotic ulcers) in immunocompromised patients. Antipseudomonal penicillins like piperacillin combined with tazobactam, aminoglycosides, and fluoroquinolones are the mainstay of treatment.
Lesson Outline
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FAQs
Pyocyanin and pyoverdin are two pigments produced by P. aeruginosa. Pyocyanin contributes to tissue damage and impairs the immune system and interferes with cellular functions. Pyoverdin is an iron chelator, helping the bacterium to acquire this essential nutrient from the host. This facilitates bacterial growth and persistence in host tissues.
Treatment of P. aeruginosa often involves antipseudomonal penicillins such as piperacillin and tazobactam, aminoglycosides, and fluoroquinolones. However, due to the bacterium's intrinsic and acquired resistance mechanisms, the choice of treatment may vary based on the local susceptibility patterns and the site of infection.
P. aeruginosa is a common cause of gram-negative nosocomial pneumonia, primarily due to its presence in hospital environments, its resistance to many antibiotics, and its ability to colonize and infect patients with compromised immunity or those on mechanical ventilation. It frequently colonizes indwelling devices and causes infections, hence it is often associated with hospital-acquired or healthcare-associated infections.
In patients with cystic fibrosis, the thick mucus in the lungs provides an ideal environment for P. aeruginosa to grow. The bacterium causes chronic lung infection and inflammation leading to lung damage over time. It can produce various virulence factors including exotoxin A, which inhibits protein synthesis in the host cells and can cause extensive tissue damage.
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