Question

6. This 48 year old man had a long history of alcoholism and was admitted to the intensive care unit with profound hypotension and gastrointestinal bleeding. He was intubated and given intravenous fluids and transfused with packet red blood cells. He remained intubated and ventilator dependent for several weeks. He developed fevers and was treated with broad-spectrum antibiotics. Culture of his tracheal aspirate initially showed Staphylococcus aureus. After further antibiotic therapy, a gram stain of his tracheal aspirate showed gram negative rods. His chest radiograph demonstrated an infiltrate and changes consistent with multiple small abscesses. Culture of the tracheal aspirate yielded heavy growth of an oxidase-positive, non-lactose fermenting, gram negative rod that produced a blue-green water soluble pigment. The causative agent of this infection is

Answer 1

The most likely chance of this infection is "prolonged intubation and putting on ventilator". Such is the nature of "hospital-acquired infections" and two major causative agents are S.aureus and Pseudomonas aeroginosa. The description of micro organism in the later part of the question shkws that the organism discussed is P.aeroginosa. While S.aureus takes sometime to show up, as in this case ( also because it is a notmal flora and only under abnormal conditions will turn pathogenic), Pseudomonas is known to fluorish fast once it enters the infection and outnumbers S.aureus.