De Bels et al. Journal of Medical Case Reports 2012, 6:20 http://www.jmedicalcasereports.com/content/6/1/20 technique that requires much experience, is not standar- dized and has significant laboratory-to-laboratory variations. In our institution, in order to get better sensitivity (for example, after reinfections), better reproducibility, greater objectivity and less cross-reactivity in the serol- ogy tests for Chlamydiaceae, two-level serological testing has been implemented for C. pneumoniae. The first level test is a search by ELISA-technique for anti-major outer membrane protein (MOMP) IgG and IgA antibo- dies (C. pneumoniae-IgG & IgA-ELISA plus, Medac, Hamburg, Germany) which are species-specific. This permits us to screen patients. The disadvantage of anti- MOMP antibodies is their late appearance in acute pri- mary infection (three weeks for IgA, six to eight weeks for IgG) and their considerable persistence in human serum afterwards, independent of the bacterial eradica- tion. In general, the prevalence of C. pneumoniae IgG antibody reaches 50% in adults above 20 years of age, and 80% in the elderly population (> 70 years old). The second level test is another ELISA assay, rELISA (Medac), for the detection of genus-specific anti-lipopo- lysaccharide(LPS) antibodies. Chlamydiae contain, as a common immunodominant antigen, the LPS to which the first immune reaction is directed. These anti-LPSs have the main advantage of rising quickly during acute infection (five to ten days for IgA), allowing early diag- nosis, and returning to normal a few weeks after the infection and are thus associated to the eradication of the bacterium [26]. The use of paired sera enables the discrimination of current infections, reinfections and reactivations (defined by titer increase) from chronic persistent ones (constant LPS, IgG and IgA antibody titers, present in 5% to 10% of the adult population) for which no antibacterial treatment is needed. The latter is due to the chronic presence of bacteria in the organism in a latent phase (monocytes). Criteria for acute infec- tions are a four-fold increase in IgA or IgG or a dou- bling of IgA and IgG at 10 to 15 days. Moreover, the described consecutive sera of our patient underwent an additional retrospective exami- nation by a MIF assay (Chlamydia MIF IgG & Chla- mydia MIF IgM, Focus Diagnostics, Cypress, CA, USA). A straightforward IgG seroconversion could also be observed (Table 1). Thanks to the detection of IgA and of IgG antibodies to C. pneumoniae in various combinations, serology allows a classification of the state of infection. In our patient, reinfection was diagnosed because MIF were positive on admis- sion; there was a four-fold increase in anti-MOMP IgG and, finally, an important rise and a rapid decline in anti-LPS IgA. Page 5 of 6 Conclusion C. pneumoniae can induce very severe ARDS. We describe the first published case of ARDS due to C. pneumoniae infection successfully treated by ECMO. Definite Chlamydophila diagnosis remains a challenge but should be sought for in severe ARDS patients with- out evidence of other infectious cause. A quick and spe- cific method for the definite diagnosis of Chlamydophila infections should be developed. Consent Written informed consent was obtained from the patient for publication of this case report and any accompany- ing images. A copy of the written consent is available for review by the Editor-in-Chief of this journal. Funding No funding was granted for this study. Author details 1Intensive Care Department, Brugmann University Hospital, 4 Place Van Gehuchten, 1020, Brussels, Belgium. 2Microbiology Laboratory, AZ Sint Jan Ziekenhuis, 10 Ruddershove, 8000 Brugge, Belgium. 3Microbiology Laboratory, Brugmann University Hospital, 4 Place Van Gehuchten, 1020, Brussels, Belgium. Authors’ contributions DDB, JD and PG have taken part in the conception, the design and the writing of the article. JD and SJ have acquired the data. SW has analyzed and interpreted the data. VYMD and MR have done all the microbiological analyses. JD, MR and SR have critically revisited it for important intellectual content. All authors read and approved the final manuscript. Competing interests The authors declare that they have no competing interests. Received: 14 June 2011 Accepted: 17 January 2012 Published: 17 January 2012 References 1. 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