Chlamydia and Rickettsia Intracellular Lifestyle PDF

The intracellular lifestyle of Chlamydia and Rickettsia Dr Suzie Hingley-Wilson, Lecturer in Bacteriology [email protected]  Learning Objectives 1) To cover the impact and aetiology of Chlamydia sp (eg C. trachomatis) 2) To cover the impact and aetiolog...

The intracellular lifestyle of Chlamydia and Rickettsia Dr Suzie Hingley-Wilson, Lecturer in Bacteriology [email protected]  Learning Objectives 1) To cover the impact and aetiology of Chlamydia sp (eg C. trachomatis) 2) To cover the impact and aetiology of Rickettsia sp (eg Rickettsia prowazekii) 1 and 2) Understand their unique life cycle/ intracellular survival  Family which once included 2 genera, Chlamydia and Chlamydophila Single genus: Chlamydia Egs: C. trachomatis; ocular, genital C. psittaci: psittacosis C. pneumoniae (10-20 % CAP, cardiovascular disease)  It’s elementary… Obligate intracellular pathogens Kaufmann Sir Samuel Bedson 1886-1969 “a morphological change from the small infecting elementary body (EB) to the large form or initial body (Bedson and Gostling, 1954) Moulder 1966…it’s a bacteria… Elementary bodies (EB); infectious form, metabolically inactive. electron dense, nucleoid, granular cytoplasm, spherical, approximately 0.2-0.3 microns in diameter Reticular bodies (RB); intracellular reproductive form, metabolically active, chromatin dispersed (transcription) approximately 0.5-2 microns in diameter, can divide by binary fission resulting in new RBs  Non-motile, obligate intracellular coccoid bacilli Inhabit epithelial cells/ macrophages Small enough to pass through 0.45 micron filters Cell wall: existence of peptidoglycan was debated until Liechti et al., 2014, A new metabolic cell-wall labelling method reveals peptidoglycan in Chlamydia trachomatis. Nature Energy parasites: lack ATP-generating ability and must obtain from host cell Chlamydia trachomatis The most common preventable cause of blindness Public health problem in 44 countries, and is responsible for the blindness or visual impairment of about 1.9 million people 142 million people live in trachoma endemic areas SAFE: Surgery, Antibiotics, Facial cleanliness and Environmental improvement In 2018, 146 112 people received surgery and 89.1 million people were treated with antibiotics. Global-level antibiotic coverage in 2018 was 50%. Trachoma (Types A, B and C) Victims with corneal opacity Infection of conjunctival epithelial cells, repeated clinical/subclinical infection and cell infiltration can cause cornea to cloud/scar Trachomatous scarring Trachoma (types A, B and C) Infection of conjunctival epithelial Transmitted by flies, fomites, cells touch Trachomatous trichiasis Favours hot, dry climates Inclusion conjunctivitis (Types Neonatal form D to K) Neonatal form: Inclusion blenorrhoea can develop when infant is in birth canal and appears 5-12 days after birth. Can precede infant pneumonia (can also develop Adult form independently). Adult form: associated with sexual contact via STD form, also from swimming pools contaminated with chlamydia from genital secretions (“swimming pool conjunctivitis”) Genital chlamydiasis NGU with discharge Men: Urethritis (NGU), 7-28 days after infection, mild burning, more frequent need to urinate, white discharge from penis Epididymitis Epididymitis, proctitis, Rieter’s syndrome, lymphogranuloma Lymphogranuloma veneruum venereum (LGV, climatic buboe) Cervicitis Women: urethritis, cervicitis, PID, infertility, ectopic pregnancy, premature Lymphogranuloma veneruum delivery, postpartum fever, LGV Psittacosis/ parrot fever Chlamydia psittaci Isolated from over 100 avian species, esp cockatiels and parakeets EB very resistant (eg in feed for 2 months) Most patients develop symptoms after 10 days Severity of clinical signs range from Non-apparent to flu-like to severe pneumonia (30-60 year olds) Risk groups, occupational disease, pigeon farmers, pet shop owners, veterinarians, poultry workers etc RICKETTSIAE: PHYLOGENY Four genera: Rickettsia Orientia Coxiella Erlichia Igenex  General Features of Rickettsiae Svet.biologije.com Obligate intracellular pathogens Small coccoids or rods (0.3 by 1-2 microns) Fastidious (embryonic eggs, tissue culture cells) Structurally similar to gm- (LPS and PG cell walls) Multiply by binary fission only in infected cells Transmitted by arthropod vectors (eg ticks, mites, lice, fleas) except Coxiella (Q fever)  Typhus Caused by Rickettsia prowazekii Arrives in Europe in 1489 via soldiers returning from Cyprus In 1557-59 an outbreak in England killed 10% of the population Transmitted by Pediculus humanus corporis (infected faeces) Incubation 7-14 days, high fever, chills, headache, may lead to coma Macular eruption 5-6 days after onset  Typhus v typhoid Svet.biologije.c Typhus: , cough, headache, joint and muscle pain, nausea, chills, confusion, low blood pressure (eg Rickettsia typhi or prowazekii) Typhoid (aka resembling typhus): Abdominal tenderness, agitation, bloody stool, chills, confusion, delirium, hallucinations, nose bleeds and fatigue (Salmonella typhi) Vector: Flea/ what you had for tea Treatment: Fluids and antibiotics, oxygen Prevention: Good hygiene, insect repellants, insecticides, vaccine FURTHER READING: Chlamydia/ Rickettsia Elwell, C., Mirrashidi, K. and Engel, J., (2016) Chlamydia cell biology and pathogenesis. Nature Reviews Microbiology 16: 385-400 Thiriot et al., Hacking the host: exploitation of macrophage polarization by intracellular bacterial pathogens, Pathogens and Disease, Volume 78, Issue 1, February 2020, ftaa009, https://doi.org/10.1093/femspd/ftaa009