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Pseudomonas Aeruginosa Infections

Pseudomonas is a small gram-negative bacillus that produces nosocomial infections, superinfections of various parts of the body, and a rare disease called melioidosis. This bacillus is also associated with bacteremia, endocarditis, and osteomyelitis in drug addicts. In local Pseudomonas infections, treatment is usually successful and complications rare. However, in patients with poor immunologic resistance­premature infants, the elderly, or those with debilitating disease, burns, or wounds-septicemic Pseudomonas infections are serious and sometimes fatal.

Causes of Pseudomonas aeruginosa infections

The most common species of Pseudomonas is P. aeruginosa. Other species that typically cause disease in humans include P. maltophilia, P. cepacia, P. fluorescens, P. testosteroni, P. acidovorans, P. alcaligenes, P. stutzeri, P. putrefaciens, and P. putida. These organisms are frequently found in hospital liquids that have been al­lowed to stand for a long time, such as benzalkonium chloride, hexachlorophene soap, saline solution, penicillin, water in flower vases, and fluids in incubators, humidifiers, and respiratory therapy equipment.

In elderly patients, Pseudomonas infection usually enters through the genitourinary tract; in infants, through the umbilical cord, skin, and GI tract.

Signs and symptoms of Pseudomonas aeruginosa infections

The most common infections associated with Pseudomonas include skin infections (such as burns and pressure ulcers), urinary tract infections, infant epidemic diarrhea and other diarrhea illnesses, bronchitis, pneumonia, bronchiectasis, meningitis, corneal ulcers, mastoiditis, otitis externa, otitis media, endocarditis, and bacteremia. Drainage in these infections has a distinct, sickly sweet odor and a greenish­blue pus that forms a crust on wounds. Other symptoms depend on the site of infection. For example, when it invades the lungs, Pseudomonas causes pneumonia with fever, chills, and a productive cough.

Diagnosis of Pseudomonas aeruginosa infections

Diagnosis requires isolation of the Pseudomonas organism in blood, spinal fluid, urine, exudate, or sputum culture.

Treatment of Pseudomonas aeruginosa infections

In the debilitated or otherwise vulnerable patient with clinical evidence of Pseudomonas infection, treatment should begin immediately, without waiting for results of laboratory tests. Antibiotic treatment includes amino­glycosides, such as gentamicin or tobramycin, combined with a Pseudomonas-sensitive penicillin, such as carbenicillin disodium or ticarcillin. An alternative combination is amikacin and a similar penicillin. Such combination therapy is necessary because Pseudomonas quickly becomes resistant to carbenicillin alone.

CLINICAL TIP :- In bacteremia, an aminoglycoside and betalactam with anti-Pseudomonal activity increases survival rates.

In urinary tract infections, carbenicillin indanyl sodium can be used alone if the organism is susceptible and the infection doesn't have systemic effects; it is excreted in the urine and builds up high urine levels that prevent resistance.

Local Pseudomonas infections or septicemia secondary to wound infection requires 1 % acetic acid irrigations, topical application of colistimethate sodium and polymyxin B, and debridement or drainage of the infected wound.