Characterisation and genetic analysis of Mycoplasma hominis and Mycoplasma pneumoniae
Mycoplasmas represent some of the smallest and simplest free living organisms known. Mycoplasma hominis and Mycoplasma pneumoniae are two human pathogens that colonise the urogenital and respiratory tracts, respectively, causing a diverse range of disease. Detection of Mycoplasma hominis is hampered by the fastidious nature and genetic heterogeneity of this organism. Characterisation of mycoplasmas is becoming more important due to increasing antibiotic resistance, particularly in M. pneumoniae, and the need for more discriminatory methods to enhance epidemiology and examine transmission chains. Firstly, this thesis develops a quantitative, multiplex, real time PCR assay to simultaneously detect M. hominis and Ureaplasma species in neonatal clinical specimens, where infection is associated with chronic lung disease, bacteremia and other clinical signs. Results showed that the PCR method was clinically more sensitive than culture and has applications for monitoring bacterial load in clinical specimens and characterising bacterial response to antibiotics. Secondly, genetic characterisation of M. hominis was undertaken by the examination of the variable adherence associated antigen and the development of sequence based typing. Due to the genetic heterogeneity of M. hominis, bioinformatics analysis of genomic sequence was used as a novel method to develop a minimum multi locus sequence typing (MLST) scheme that accurately represented genomic phylogeny of this species. Finally, an MLST scheme was developed for M. pneumoniae, to aid the analysis of epidemic periods and clusters of infection. A successful scheme was developed based on eight housekeeping genes which had increased discrimination of M. pneumoniae compared to established typing methods for this organism. Furthermore, the MLST scheme was found to be representative of genomic sequence derived phylogeny, with two distinct genetic clades identified. Application of this MLST to UK epidemics revealed that no predominant sequence type was responsible for the epidemic periods studied, indicating a polyclonal population, supporting the hypothesis that epidemics are driven by population immunity.