Case #013

A pneumonia four days into amoxicillin and still deteriorating has largely excluded the organisms amoxicillin covers, and the sputum says the same thing more directly: abundant neutrophils, no visible organism. A plainly purulent pneumonia whose pathogen refuses to appear on the film is the signature of Legionella, which stains too faintly to be seen on a routine Gram preparation. Blood cultures sterile at 48 hours argue further against pneumococcus, which is frequently bacteraemic when disease runs this severe. Then comes the systemic reach that pneumococcal pneumonia lacks: confusion, headache and watery diarrhea out of proportion to the chest, a pulse of 82 at 39.6 °C, sodium of 124 mmol/L, raised transaminases, hypophosphatemia and a creatine kinase of 1240 U/L from rhabdomyolysis. The hyponatremia discriminates best, running both commoner and deeper here than in other community-acquired pneumonia. The hotel spa pool supplies the epidemiology, an aerosol-generating warm water system being how the organism reaches a lung at all. Treatment then follows from where the organism lives rather than what it is built from. Legionella is a Gram-negative bacillus and does have a cell wall; amoxicillin failed because the organism replicates inside alveolar macrophages, where the drug does not follow it. That calls for an agent which concentrates intracellularly: a respiratory fluoroquinolone such as levofloxacin, or a macrolide such as azithromycin, for 7 to 10 days and longer if he proves immunocompromised. A negative urinary antigen would have excluded nothing, since the test detects only serogroup 1, and the case is notifiable so the hotel's water system can be traced.