Pyrolysis mass spectrometry in epidemiological and population genetic studies of Haemophilus influenzae

Haemophilus influenzae serotype b (Hib) vaccines have reduced the amount of invasive Hib disease in immunised infants. However, Hib disease remains in unvaccinated infants and adults and non-capsulate H. influenzae (NCHi) still causes infections, including outbreaks of respiratory disease. Characterisation of strains and the bacterial population as a whole is therefore necessary to detect outbreaks of infection with NCHi or changes in the population, for example, to vaccine-resistant clones of Hib. The rapid, simple and objective technique of pyrolysis mass spectrometry (PMS) was investigated as an alternative to current complex, subjective methods. PMS was compared with ribotyping and multilocus enzyme electrophoresis (MLEE) for population genetic analyses of Hib and with ribotyping and protein profiling for epidemiological analyses of NCHi. PMS clustered all the isolates of Hib together whereas MLEE and ribotyping distinguished certain clones - this is probably because the three methods examine different (and unrelated) characteristics of the organisms. The PMS results were essentially similar to those from ribotyping and protein profiling for the epidemiological analyses of outbreaks of NCHi disease. Therefore, PMS is probably unsuitable for comparisons of Hib populations but it is a useful addition to the arsenal of techniques for the characterisation of NCHi.