Chlamydia pneumoniae is frequently detected in the blood after acute lung infection

Abstract

To the Editors: The obligate intracellular bacterium Chlamydia pneumoniae is a common cause of acute respiratory infections with a worldwide seroprevalence of up to 70% 1. Bacterial persistence following acute infection in the respiratory tract or in atherosclerotic blood vessels has been suggested to be involved in the pathogenesis of chronic inflammatory diseases, such as chronic obstructive pulmonary disease and atherosclerosis 2, 3. It has been shown in animal models that after acute lung infection with C. pneumoniae , the pathogen is systemically distributed in the blood circulation using blood monocytes as a vector 4, 5. However, data supporting this hypothesis in humans are still missing. From in vitro observations, it is known that C. pneumoniae infection of human blood monocytes results in a nonreplicative but viable state of the pathogen, which is refractory to antibiotic treatment 6. The objective of this study was to analyse whether C. pneumoniae systemically disseminates from the lung to the blood in patients with an acute lower respiratory tract infection (LRTI). Patients recovering from acute C. pneumoniae lung infection were monitored for the presence of C. pneumoniae DNA in the blood during follow-up visits (at 30 and 90 days post infection) and compared with patients after Streptococcus pneumoniae infection. Patients presenting at the emergency room or outpatient departments of the University Hospital Schleswig-Holstein, Campus Luebeck (Luebeck, Germany) with radiographically confirmed nonsevere community-acquired pneumonia (CAP) or severe LRTI with fever, productive cough and positive auscultatory findings were tested during a 3-yr period for the presence of C. pneumoniae or S. pneumoniae as causative pathogens of the disease. Inclusion criteria were the ability …