Phase variation of lic1A, lic2A and lic3A in colonization of the nasopharynx, bloodstream and cerebrospinal fluid by Haemophilus influenzae type b

The role of phase variation of lic1A. lic2A and lic3A in the ability of Hae mophilus influenzae type b to colonize the nasopharynx, bloodstream and cer ebrospinal fluid (CSF) of infants was investigated, This was achieved by us ing PCR to determine the number of 5'-CAAT-3' repeats present in each gene, which is indicative of whether each ORF can be expressed, Multiple PCR pro ducts of different intensities were amplified from all three genes at each site sampled. This indicated that the nasopharynx. bloodstream and CSF were colonized by a heterogeneous population of organisms, expressing different combinations of lic genes, At each site however, a predominant PCR product was amplified from each gene, indicating that organisms with this genotype were the most abundant. The number of 5'-CAAT-3' repeats in this predomina nt product varied depending upon whether organisms were isolated from the n asopharynx, bloodstream or CSF, These observations suggest that the express ion of different combinations of lic genes may influence the efficiency wit h which H, influenzae colonizes the nasopharynx, bloodstream and CSF of inf ant rats.