Frequency of serological evidence of Bordetella infections and mixed infections with other respiratory pathogens in university students with cough illnesses

Banked acute-phase and convalescent-phase serum samples from a previous study of respiratory illness in university students were examined for significant (greater than or equal to2-fold) increases in ELISA titers of IgA and IgG antibody to Bordetella pertussis filamentous hemagglutinin, pertactin, and fimbriae-2 and greater than or equal to4-fold titer increases to agglutinogens by agglutination. ELISA titers of antibody to pertussis toxin could not be determined because of technical problems. Chlamydia pneumoniae infections were diagnosed by culture or by a greater than or equal to4-fold increase in immunofluorescence assay titer or a single high titer (greater than or equal to 512). Mycoplasma pneumoniae, influenza A and B, adenovirus, and respiratory syncytial virus infections were diagnosed by greater than or equal to4-fold increases in complement fixation titer or a single high titer (greater than or equal to 64). There were 319 subjects with cough of greater than or equal to5 days' duration, and of these, 47 (15%) had significant increases in antibody to B. pertussis antigens; 26 (8%) had significant increases to fimbriae-2 or agglutinogens, indicative of B. pertussis infection, and 2 (1%) had evidence of non-B. pertussis bordetella infections. Seventeen (36%) had evidence of mixed infections or cross-reacting antibodies (influenza B infections, 5; adenovirus infections, 4; influenza A infections, 3; C. pneumoniae infections, 3; and IM. pneumoniae infections, 2). Our findings suggest that bordetella infections are common in young adults with cough illnesses (incidence, 9%), and a surprising number of these are mixed infections with other respiratory pathogens.