8th December 2016 Microbiology Obligate intracellular parasites: Rickettsia Rickettsia sp .: Alpha proteobacteria Rickettsiales Order Rickettsiales Family Rickettsiaceae Anaplasmataceae Genus Rickettsia Orientia Ehrlichia - infect macrophages; huge inflammatory response Anaplasma Species R. rickettsii R. akari R. prowazekii R. typhi O. tsutsugamushi Rickettsiaceae · Obligate intracellular bacteria · Live free in cytoplasm - fundamental difference between chlamydia (lives in phagosome) Anaplasmataceae · Obligate intracellular bacteria · Live in cytoplasmic vacuoles lipopolysaccharide O-polysaccharide lipid A · Ehrlichia infect macrophages Howard Ricketts - discovered Rickettsia, isolated it form Guniea pigs, injected himself and died: worked out the life cycle. porin outer membrane Rickettsia- characteristics · Obligate, Intracellular bacteria periplasmic space lipoprotein peptidoglycan · Grow only in cytoplasm of host cells · Aerobic · Small (0.3 x 1-2 um width) plasma membrane Gram negative rods - like the chlamydia, doesn't have a lot of peptidoglycan · Weak gram stain · Full sized LPS Loosely adherent slime layer Do not possess: (makes us think they are non-motile, but they do by entering the eukaryotic cells) · Flagellae · Pili Enter eukaryotic cells
8th December 2016 Microbiology · Stimulate phagocytosis · Degrade phagosome membrane · Live free in cytoplasm/nucleus Grow slowly · Binary fission - 9-12hrs doubling time · Genome sequencing · Small genome (<1500 kb) not as small as chlamydia, but use the host for most things (parasite) efficient and slim down in the genes they actually need · Require host for: · CHO metabolism · Lipid biosynthesis · Nucleotide synthesis · Amino acid synthesis · Can produce ATP via TCA cycle · Can also parasitise energy · ATP translocase Rickettsia-Gram negative envelope Standard envelope (S-LPS) Rickettsia- Endotoxin (LPS) Full length sugars, O antigen and Lipid A · Lipopolysaccharide · Poor endotoxin activity · Lipid A · Core (SR-LPS) (R-LPS) Lipopolysaccharide (LPS) · O antigen Contains: Polysaccharide (PS) . Glucose . KDO O-antigon n Outer core Inner core lipid A · Glucosamine 2 · Phosphate . Fatty acids Quinovosamine - presence of this amino sugar - diagnostic test of the antibody cf Proteus (antibodies that are cross-reactive with this protein and this will tell us if the patient has or had an infection) Rickettsia sp. · Humans are accidental hosts · Maintained in animal and arthropod reservoirs - they move between animals and ticks and mites in the wild - their life cycle. This maintains the
Microbiology 8th December 2016 organism and high levels and we have no way of removing the natural reservoir of this pathogen Spotted fever group 17+ species R. rickettsii most important Causes problems through out the world, not just in South America Organism R. rickettsii Rocky Mountain Spotted Fever R. akari Rickettsial pox US R. prowazekii Human disease Typhus - cold fog (cannot think properly) Disease Rocky Mountain spotted fever Organism Vector R. rickettsii Tick-borne Reservoir Ticks, wild rodents Distribution Western hemisphere WW It is unlikely that humans are a reservoir as they die before they can pass it on Rickettsialpox Scrub typhus O. tsutsugamushi Epidemic typhus Murine endemic typhus