ABSTRACT
<p><b>BACKGROUND</b>To isolate and identify pathogen of atypical pneumonia in Guangdong.</p><p><b>METHODS</b>Pathogens were isolated from variety of samples collected from atypical pneumonia patient by using MDCK cells, and identified with serological and molecular methods.</p><p><b>RESULTS</b>A novel coronavirus was isolated from patients with atypical pneumonia, from which an RNA fragment of 279 nt was amplified by nested RT-PCR. And sequence assay showed that only 39-65 percent of sequence of the virus was homogenous to known coronavirus, but almost 100% homogenous (with one base exception, 12a to t) to SARS-associated coronavirus isolated from patients outside Guangdong, such as in Beijing, Hong Kong, Taiwan, Germany, Italy and so on. Indirect immunofluorescence test showed a specific antigen-antibody reactivity between the coronavirus and convalescent-phase sera of SARS patients.</p><p><b>CONCLUSION</b>The pathogen of the atypical pneumonia in Guangdong province was a novel type of coronavirus, which could be isolated by using MDCK cells.</p>