Tohoku J. Exp. Med., 2012, 226(2)

Complicated Secondary Pneumonia after Swine-Origin Influenza A Virus Infection in an Immunocompetent Patient

RYOTARO IGUSA,¹ TOMOHIRO SAKAKIBARA,² TAIZO SHIBAHARA,² KAZUHIRO SAKAMOTO,³ HIDEKAZU NISHIMURA⁴ and KOZO OTA⁵

¹Department of Respiratory Medicine, Osaki Citizen Hospital, Osaki, Japan
²Department of Respiratory Medicine, Tohuku University Hospital, Sendai, Japan
³Department of Pathology, Osaki Citizen Hospital, Osaki, Japan
⁴Department of Virus Research Center, Clinical Research Division, Sendai Medical Center, Sendai, Japan
⁵Department of Medicine, Osaki Citizen Hospital, Osaki, Japan

The pandemic of the swine-origin influenza A virus (S-OIV) in 2009 demonstrated severe viral pneumonia followed by acute respiratory distress syndrome (ARDS). Although ARDS would be caused by the influenza virus pneumonia itself, it has remained unclear whether other respiratory viral or bacterial infections coexist with S-OIV pneumonia. We report an immunocompetent patient with methicillin-resistant Staphylococcus aureus (MRSA) and Herpes simplex virus (HSV) pneumonia secondary to S-OIV infection. A 57-year-old man previously without major medical illness was admitted to our hospital with severe pneumonia accompanied by ARDS due to S-OIV. In his clinical course, anti-influenza treatment was not effective. Sputum culture revealed the presence of MRSA, and HSV was isolated in broncho-alveoler lavage (BAL) fluid. Administration of an antiviral agent (acyclovir), an antibacterial agent (linezolid), and a corticosteroid (methylprednisolone) successfully improved the pneumonia and ARDS. HSV pneumonia can scarcely be seen in healthy people. However recently it has been recognized as a ventilator-associated pneumonia. Although coexistence of Streptococcus pneumoniae and MRSA was reported in S-OIV pneumonia, secondary viral infection has not been reported. The present report is the first patient with HSV pneumonia secondary to S-OIV infection. We propose that a possibility of hidden HSV pneumonia should be taken into consideration in patients with prolonged severe pneumonia due to influenza infection.

keywords —— acute respiratory distress syndrome; herpes simplex virus pneumonia; methicillin-resistant Staphylococcus aureus; swine-origin influenza virus; ventilator-associated pneumonia

© 2012 Tohoku University Medical Press

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Tohoku J. Exp. Med., 2012, 226, 117-120

Corresponding: Ryotaro Igusa, M.D., Ph.D., Department of Respiratory Medicine, Osaki Citizen Hospital, Furukawa Senjyujimati 2-3-10, Osaki, Miyagi 989-6183, Japan.

e-mail: ryoigusa@h-osaki.jp