A COUGH THAT LINGERED: DIAGNOSING LEGIONELLA PNEUMONIA. R. Mann 1 , D.W. Brady 1 ; 1 Emory University, Decatur, GA LEARNING OBJECTIVES: 1. Diagnose legionella pneumonia from its clinical manifestations. 2. Recognize the limited utility of the legionella urinary antigen in excluding the diagnosis of legionella in a patient with a pneumonia that has been refractory to treatment. CASE INFORMATION: A 40 year old black male presented complaining of a 3-week history of cough (productive of dark yellow sputum), fevers, chills, nightsweats, and malaise. He initially was treated at an out of town facility with a 5 day course of azithromycin, with some improvement in symptoms; however, within 2 ± 3 days after completing the medication, the symptoms returned. He presented to a second emergency room, where he received a chest xray and was discharged home with a prescription for guafenesin. One week later, he presented again. A second chest xray revealed interval worsening of a right middle and right upper lobe pneumonia with a patchy airspace opacity in the left upper lobe consistent with pneumonia. On exam his blood pressure was 156/75, pulse 119, respiratory rate 30, temperature 36.9C, with bilateral rales throughout. Pulse ox-70% on room air ( ABG on 100% FiO2-pH 7.44; pC02 30; pO2 100); WBC count 16.5 (77%N,6%Mono,16%L), ; HIV test was negative. He was admitted and treated with IV ceftriaxone and erythromycin for the first 72 hours with worsening hypoxemia. Erythromycin was replaced with IV Azithromycin for the next 48 hours with no improvement. Levofloxacin 750mg IV qd was added to replace azithromycin to cover Legionella. A Legionella urine antigen was negative. After 48 hours of high dose Levofloxacin, the patient showed little clinical improvement. Legionella, mycoplasma, and influenza serologies were sent, as preparations were being made for bronchoscopy. On the 3rd day of high dose Levofloxacin the patient began to require lower FiO2's and subsequently the Legionella Pneumophilia IgM serology was found to be positive (1:64) . Within the next week, the patient was discharged home to complete a 21 day course of high dose Levofloxacin for treatment of Legionella pneumonia. DISCUSSION: This patient's final diagnosis was made after a protracted outpatient and subsequent inpatient course of therapy. His pneumonia ultimately was found to have been caused by Legionella pnuemophila; however, the legionella urinary antigen was negative. Clinicians should be aware that the legionella urinary antigen only tests for serogroup I of L. pnuemophila, and a negative urinary antigen does not, in fact, rule out infection caused by L. pneumophila (the most common Legionella species causing community-acquired pneumonia in the U.S.). Often, serum antibodies are needed to confirm or exclude the diagnosis.