Pneumonia due to Mycoplasma, Chlamydophila and Legionella

The term 'atypical pneumonia' currently identifies pneumonia cases due to Mycoplasma pneumoniae, Chlamydophila pneumoniae and Legionella pneumophila, but this definition is not universally recognised. These infections, together with Streptococcus pneumoniae,aretheleadingcauseof pneumonia in outpatients and they are also responsible for hospitalised pneumonia. Due to the fact that these bacteria are naturally resistant to b-lactams, they should be promptly identified, although single clinical or instrumental signs with a sufficient differential diagnostic accuracy have not been described. The use of scoring systems in order to make a weighted evaluation of individual signs and symptoms has been attempted, but results are as yet inconclusive. The use of specific testing (culture, serology and molecular biology) might be useful in identifying a greater number of atypical pneumonia, although each test has important limitations regarding accuracy and feasibility. An approach based on the evaluation of clinical risk associated with the combination of specific tests could be useful for a personalised antibiotic therapy.