Question

2. An 11-year-old girl is admitted to the hospital for treatment of lymphoma. During cytoreductive chemotherapy, she develops a fever and pneumonia. Analysis of pulmonary fluid shows a few white cells (neutrophils) and slender, gram-negative rods. The isolated bacteria produce a characteristic apple-green pigment on tryptic soy agar. What organism is likely to be causing the infection? What led you to this diagnosis? How is the patient likely to have contracted this bacterium? Name another group of patients at risk from this bacterium. •

Answer 1

2.

Pseudomonas aeruginosa is a Gram-negative, rod-shaped, motile organism (polar flagella) which characteristically produce water-soluble pigments which diffuse through the medium. This organism produces apple green pigment on tryptic soy agar.
Pseudomonas aeruginosa is often preliminarily identified by its typical odor in vitro. The smell is described as grape-like, tortilla-like (production of aminoacetophenone).

The bacteria might have reached the girl during her stay in hospitals via the hands of healthcare workers, or by hospital equipment that is not properly cleaned. Pseudomonas are the reason for most of the nosocomial infections. They are opportunistic infections causing the disease when the immunity is lowered. The child already has lymphoma and under chemotherapy. Here her immune system is compromised and the infection occurred at this chance.

Pseudomonas aeruginosa is an opportunistic pathogen that infects burns, wounds, surgical incisions and sites of catheterization. It is the most common cause of infections of burn injuries and of the outer ear (otitis externa). It can, in rare circumstances, cause community-acquired pneumonias, as well as ventilator-associated pneumonias.