Tohoku J. Exp. Med., 2007, 213(2)

Increased Rates of Intense Nasopharyngeal Bacterial Colonization of Vietnamese Children with Radiological Pneumonia

DANG DUC ANH,⁵ PHAN LE THANH HUONG,⁵ KIWAO WATANABE,¹ NGUYEN THU NGUYET,⁶ NGUYEN THU HIEN ANH,⁵ NGO THI THI,⁶ NGUYEN TIEN DUNG,⁷ DOAN MAI PHUONG,⁷ SUSUMU TANIMURA,² YASUSHI OHKUSA,⁴ TSUYOSHI NAGATAKE,¹ HIROSHI WATANABE¹ and KAZUNORI OISHI^1,3

¹Department of Internal Medicine, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
²Socio-Environmental Medicine, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
³Laboratory for Clinical Research on Infectious Diseases, International Research Center for Infectious Diseases Research, Institute for Microbial Diseases, Osaka University, Suita, Japan
⁴National Institute of Infectious Disease, Tokyo, Japan
⁵National Institute of Hygiene and Epidemiology, Hanoi, Vietnam
⁶National Pediatric Hospital, Hanoi, Vietnam
⁷Bach Mai Hospital, Hanoi, Vietnam

Acute lower respiratory infection (ALRI), primarily pneumonia, is the leading cause of death in children under the age of five. Bacterial ALRI is preceded by asymptomatic bacterial colonization. Bacterial colonization, therefore, may have an important role in the development of pneumonia in children. This case-control study was conducted in order to determine if intense bacterial colonization was increased in the nasopharynx of pediatric patients with ALRI. One hundred-sixty four pediatric patients with ALRI and 70 healthy children < 5 years of age were enrolled in Hanoi, Vietnam between 2001 and 2002. Bacterial pathogens were isolated from nasopharyngeal secretions and quantitatively cultured. Of 164 patients, 91 were diagnosed as having radiological pneumonia (PN group) and 73 as having acute bronchitis (AB group). Intense growth of any bacterial pathogen (≥ 10⁶ colony-forming units/ml) was highest in the PN group (49.4%), followed by the AB group (28.8%), with healthy children having the lowest (17.1%). Patients with intense bacterial growth were more likely to develop pneumonia, but not acute bronchitis, than were patients with light or no bacterial growth. The results of this case-control study suggest that the vertical spread of intense bacterial pathogens colonized in the nasopharynx to the lower airway leads to bacterial pneumonia in children under the age of five.

keywords —— radiological pneumonia; children; bacterial colonization; Vietnam; Streptococcus pneumoniae

© 2007 Tohoku University Medical Press

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Tohoku J. Exp. Med., 2007, 213, 167-172

Correspondence: Kazunori Oishi, Laboratory for Clinical Research on Infectious Diseases, International Research Center for Infectious Diseases, Research Institute for Microbial Diseases, Osaka University, 2-2 Yamada-oka, Suita, Japan.

e-mail: oishik@biken.osaka-u.ac.jp