There are a number of genes related to antibiotic resistance that have been identified in various members of the genus Rickettsia. We have first compared the genomes of Orientia isolates with the genome of Rickettsia bellii. This is because R. bellii represents the most ancestral major phylogenetic split within the genus Rickettsia (Stothard, Clark and Fuerst, 1994); Stothard and Fuerst, 1995). [Comparison with additional members of Rickettsia have been performed for several genes, and more will be done in the future].
Among the genes in Rickettsia with the potential to be involved in antibiotic resistance many do not have a homologue that can be identified within the genomes of isolates of Orientia. These genes include (but are unlikely to be limited to):
emrA – “Multidrug resistance protein A”: present in R. bellii
emrB – “multidrug resistance protein B”: present in R. bellii
“Tellurite resistance protein-related protein”: present in R. bellii
“mrcA” = “Penicillin-binding protein 1A”: present in R. bellii
dacF – “Penicillin-binding protein dacF precursor”: present in R. bellii
pbpC – “Bifunctional penicillin-binding protein 1C”: present in R. bellii
blaD – “Class D beta-lactamase”: present in R. bellii
folKP – “Folate synthesis bifunctional protein”: present in R. bellii
Also missing are genes that are components of the RND efflux system including:
Efflux transporter, RND family, MFP subunit: present in R. bellii
RND family efflux transporter: present in R. bellii
Membrane-fusion protein component of the RND family transporter: present in R. bellii
RND efflux system, outer membrane protein: present in R. bellii