Species-specific diagnostic test to identify infection of a mammal, such as a human, with chlamydia pneumoniae, fragment of nucleic acid derived from chlamydia pneumoniae, protein derived from chlamydia pneumoniae, polyclonal monospecific antibody, diagnostic kit for the diagnosis of infection of a mammal, as a human, with chlamydia pneumoniae, composition to immunize a mammal as a human, against chlamydia pneumoniae, use of a protein, and use of a nucleic acid fragment.