Seroreactivity to Mycoplasma pneumoniae and Legionella pneumophila: lack of a statistically significant relationship.

We reviewed antibody titers to Mycoplasma pneumoniae and Legionella pneumophila serogroup I in sera from 1,060 cases of acute respiratory infection to determine whether there was an association in seroreactivity to these organisms. Of the 170 serum pairs with antibodies to L. pneumophila (35 seroconversions and 135 with presumptive titers), 32 (18.8%) demonstrated seroreactivity to M. pneumoniae (17 seroconversions and 15 with presumptive titers). This frequency was not significantly greater than the seroreactivity to M. pneumoniae observed in sera without antibodies to L. pneumophila (17.5%) (0.05 less than P less than 0.10), which included 111 seroconversions and 45 sera with presumptive titers.