Lipopolysaccharide gel profiles of Haemophilus influenzae type b are not stable epidemiologic markers

Abstract

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of lipopolysaccharide (LPS) was performed to assess the usefulness of this technique for the epidemiologic analysis of Haemophilus influenza type b isolates. LPS samples were prepared from isolates which had been passaged either in vitro or in infant rats. Preparations from paired isolates from a number of epidemiologically related clinical situations also were examined. The gel patterns of LPS prepared on different occasions from an individual isolate were stable. However, the LPS gel patterns changed in 5 of 14 (36%) of the passaged isolates, and differences in gel patterns also were observed among epidemiologically related isolates. The variability in LPS electrophoretic patterns of individual isolates indicated that this technique is not useful for the epidemiologic analysis of H. influenzae type b disease.

Haemophilus influenzae type b lipooligosaccharide: stability of expression and association with virulence

“…Single-colony passage of these 30 Hib strains resulted in the identification of 3 strains which gave rise to variants with antigenically different LOS characteristics. These data are similar to those of Tolan et al (36), who recently reported that three of six Hib isolates from an outbreak of Hib disease in an Amish community yielded variants with altered LOS profiles, as determined by SDS-polyacrylamide gel electrophoresis, after in vitro passage. In contrast, four other Hib strains used routinely by these workers did not yield any LOS variants after 21 passages in vitro (36).…”

“…These data are similar to those of Tolan et al (36), who recently reported that three of six Hib isolates from an outbreak of Hib disease in an Amish community yielded variants with altered LOS profiles, as determined by SDS-polyacrylamide gel electrophoresis, after in vitro passage. In contrast, four other Hib strains used routinely by these workers did not yield any LOS variants after 21 passages in vitro (36). These data, together with those obtained from the present study, suggest that the stability of expression of the LOS phenotype by Hib is a strain-specific phenomenon, with some Hib strains giving rise to LOS phenotypic variants at much higher rates than others.…”

“…The mechanism(s) by which changes in Hib LOS phenotype are associated with changes in serum resistance is unclear. Hib has been shown to activate the alternative complement pathway in the absence of specific antibody, but it is apparently not susceptible to its bactericidal activity under these conditions (33,36). Conversely, the serumsensitive strains involved in the present study and in a previous study (7) were killed by normal serum bactericidal activity involving the classical pathway of complement activation ( Table 5).…”

“…Our findings concerning the stability of expression of LOS by Hib have potentially important implications for two different areas of research involving Hib. As assessed by SDS-PAGGE, the LOS phenotype has been used by several laboratories studying the epidemiologic aspects of Hib disease (14,22,36). While our data indicate that not every LOS antigenic variant has an altered LOS profile in SDS-PAGGE relative to the respective parental strain (Fig.…”

“…1), all of the Hib strains used in our study exhibited detectable frequencies of LOS antigenic variation ( Table 2). These data and those of Tolan et al (36) suggest that the LOS phenotype may not be a reliable strain marker for epidemiologic studies. Perhaps more importantly, investigation of the genetic control of Hib LOS synthesis involving genetic transformation experiments must now take into account the occurrence of spontaneous LOS variation.…”