RIBOTYPING OF STRAINS OF MORAXELLA (BRANHAMELLA) CATARRHALIS CULTUREDFROM THE NASOPHARYNX AND MIDDLE-EAR OF CHILDREN WITH OTITIS-MEDIA

Moraxella (Branhamella) catarrhalis is frequently present in the nasop haryngeal microflora of small children, especially during episodes of acute otitis media. By means of ribotyping (restriction endonuclease a nalysis of chromosomal DNA combined with rRNA probing), we studied the genetic heterogeneity of 78 cultures of M. catarrhalis obtained from different localities in the nasopharynx of nine young children with se cretory otitis media. Using HindIII and PstI as endonucleases, five di fferent ribotypes were recognized, representing at least five differen t genotypes of M. catarrhalis. The distribution of these types was fou nd to be almost identical to the distribution among 16 M. catarrhalis strains cultured from middle ear exudates of 16 children with acute ot itis media. Ribotype HAPA was found in two-thirds of all the cultures investigated; and 44% of the children harboured more than one ribotype in the nasopharynx at the same time. The vast majority of the nasopha ryngeal M. catarrhalis cultures were beta-lactamase positive. One chil d had both a HAPA ribotype, beta-lactamase-negative strain in the naso pharyngeal secretions, and HAPA ribotype, beta-lactamase-positive stra ins at the entrance of the eustachian tube, the nasopharyngeal tonsils , the folds of the nasopharyngeal tonsils and the oropharynx. All exce pt one of the M. catarrhalis strains cultured from middle ear exudates were beta-lactamase positive.