The Case of the Vanishing Link

Abstract

Learning Objectives: Staphylococcus aureus (SA) is a rare cause of community acquired pneumonia(CAP) and a major cause of influenza related mortality and morbidity. Necrotizing pneumonia due to Panton Valentin leucocidin (PVL) toxin secreting strains of S. aureus is associated with a mortality rate of up to 40-60%. Both methicillin resistant (MRSA) and methicillin sensitive S. aureus (MSSA) can carry gene for PVL toxin. Methods: A sixty-three year old female with a history of asthma, who had lost her husband 1 week ago from pneumonia, presented to the emergency room with a fever, generalized malaise, nasal discharge, cough, sputum production and shortness of breath for 3 days. Blood work demonstrated leukocytosis with bandemia. Chest X-Ray showed bilateral infiltrates. She was treated for CAP with Ceftriaxone and Azithromycin. Blood culture grew MSSA. She received nafcillin but her condition deteriorated. She required high flow 100% oxygen. Chest CT scans done 7 days apart showed blossoming bilateral infiltrate and development of multiple cavitary lesions of the lung. She was started on Linezolid, Clindamycin and intravenous immunoglobulin (IVIG) for suspected necrotizing pneumonia with PVL toxin producing MSSA. She underwent extra corporeal membrane oxygenation with subsequent recovery. The genetic study confirmed PVL gene consistent with MRSA USA 300. Results: PVL toxin causes lysis of the neutrophil with release of pro-inflammatory cytokines. Influenza like prodrome, leukopenia, thrombocytopenia, hemorrhage and pleural effusion are indicators of fatal outcome. Clindamycin and Linezolid have antitoxin effect and may improve clinical outcome. IVIg has also been used with some success. In the U.K. routine testing is done as most European PVL strains are MSSA, however it is not recommended in the U.S. Conclusions: The suspicion of PVL toxin producing SA strain as a cause of necrotizing pneumonia is extremely important. Early initiation of treatment with appropriate antibiotics directed at the toxin and IVIG might be lifesaving. Checking for PVL toxin may help in early determination of a fatal pathogen.