Pathogens in COPD exacerbations identified by comprehensive real-time PCR plus older methods

Kenichiro Shimizu,1 Yutaka Yoshii,1 Miyuki Morozumi,2 Naoko Chiba,2 Kimiko Ubukata,2 Hironori Uruga,3 Shigeo Hanada,3 Nayuta Saito,1 Tsukasa Kadota,1 Saburo Ito,1 Hiroshi Wakui,1 Naoki Takasaka,1 Shunsuke Minagawa,1 Jun Kojima,1 Hiromichi Hara,1 Takanori Numata,1 Makoto Kawaishi,1 Keisuke Saito,4 Jun Araya,1 Yumi Kaneko,1 Katsutoshi Nakayama,1 Kazuma Kishi,3 Kazuyoshi Kuwano1 1Division of Respiratory Diseases, Department of Internal Medicine, The Jikei University School of Medicine, 2Department of Infectious Diseases, Keio University School of Medicine, 3Department of Respiratory Medicine, Respiratory Center, Toranomon Hospital, 4Department of Respiratory Medicine, The Jikei University Daisan Hospital, Tokyo, Japan Abstract: Respiratory infection is a major cause of exacerbation in chronic obstructive pulmonary disease (COPD). Infectious contributions to exacerbations remain incompletely described. We therefore analyzed respiratory tract samples by comprehensive real-time polymerase chain reaction (PCR) in combination with conventional methods. We evaluated multiple risk factors for prolonged hospitalization to manage COPD exacerbations, including infectious agents. Over 19 months, we prospectively studied 46 patients with 50 COPD exacerbations, collecting nasopharyngeal swab and sputum samples from each. We carried out real-time PCR designed to detect six bacterial species and eleven viruses, together with conventional procedures, including sputum culture. Infectious etiologies of COPD exacerbations were identified in 44 of 50 exacerbations (88%). Infections were viral in 17 of 50 exacerbations (34%). COPD exacerbations caused by Gram-negative bacilli, including enteric and nonfermenting organisms, were significantly associated with prolonged hospitalization for COPD exacerbations. Our results support the use of a combination of real-time PCR and conventional methods for determining both infectious etiologies and risk of extended hospitalization. Keywords: COPD, exacerbation, etiology, real-time PCR, prolonged hospitalization, risk factor