Is C. Pneumoniae Research in Peril?

Chlamydia pneumoniae is an obligate intra-cellular parasite which infects mucosal surfaces of the human respiratory tract causing sinusitis, pharyngitis, bronchitis, and pneumonia. Although the bacterium causes acute disease, mildly symptomatic, asymptomatic, or unrecognized infections are most common (Kuo et al., 1995). C. pneumoniae infections are widespread among children 5–14 years of age and by age 20 years about 50% of young adults have detectable antibodies to the microorganism. The seroprevalence to C. pneumoniae continues to rise in the population and reaches approximately 75% in the elderly. Moreover, the epidemiological data suggests that most people are infected and re-infected throughout life (Kuo et al., 1995). C. pneumoniae was established as a human respiratory pathogen in 1986 (Grayston et al., 1986) and initially research on this pathogen was rigorous , especially due to its association with variety of chronic diseases such as Reiter's syndrome, sarcoidosis, asthma, chronic obstructive pulmonary disease (COPD), multiple sclerosis, Alzheimer disease, and atherosclerosis. However in recent years, the interest in basic as well as clinical research on C. pneumoniae has undergone a sharp decline. One of the major factors that could have contributed to this decline may include frequent discrepancies in published data. Multiple studies have described the presence of C. pneumoniae in patient samples from those who suffered from the chronic diseases listed above by either serology, polymerase chain reaction (PCR), RT-PCR, immunocytochemistry (ICC) or electron microscopy, and occasionally even by direct isolation of the bacterium. Conversely, there are laboratories which could not confirm these findings. Inter-laboratory variations in sample collection, processing and C. pneumoniae detection methods are likely to be responsible for these inconsistencies (reviewed in Boman and Hammerschlag, 2002). However, numerous studies published on C. pneumoniae, describing the presence or absence of the microorganism , often lacked appropriate positive and/ or negative controls. Using only one or two methods for C. pneumoniae detection in clinical specimens is insufficient and may have led to inaccurate conclusions Furthermore, positive labeling of cells or tissue for C. pneumoniae antigen(s) with an antibody does not necessarily represent an intact bacterium. It has been demonstrated that chlamydiae-infected cells stay positive for several of the chlamydial antigens, for example LPS, weeks after the bacterium has been degraded by lysosomes (Wolf et al., 2005). Direct isolation of C. pneumoniae from a patient's sample still represents the most conclusive, yet the most difficult method of detection of this pathogen. In spite of these …