chlamydia, rickettsia, mycoplasma Flashcards
chlamydia
gram-negative; obligate intracellular; unique developmental cycle; ubiquitous
developmental cycle of chlamydia
attachment and entry redistribution to nuclear periphery early differentiaiton contact-dependent replication detachment and asynchronous late differentiation lysis and release of infectious progeny
chlamydia virulence factors
type III secretion - molecualr syringes that inject virulence factors directly into the cytosol of infected cell
auto-transported polymorphic membrane protein gene family
common these in chlamydial infections
frequently long-lasting in the absence of treatment
repeated infecitons following natural clearance or antibiotic treatment of an initial infeciton
infections are often asymptomatic or minially symptomatic
infections can cause inflammatory and scarring complications in the absence of treatment, often with minimal or no symptoms
genital chlamydia trachomatis primary infection
often mild or asymptomatic
men: non-gonococcal urethritis
women: urethritis, cervicitis
sequelae of chronic infection by genital chlamydia trachomatis in women
PID
ectopic pregnancy
infertility
lymphogranuloma venereum (serovars L1-L3)
shallow ulcer on genitalia; invasic: lymphodenopathy of inguinal lymph nodes; potentially severe complications; risk factor for HIV
immunity in genital infections
both antibody and cell-mediated immunity required
immunity short-lived
no vaccine
vaccine made more difficult because the disease is host-mediated
ocular chlamydia trachomatis (serovars A-C)
primary infection: inclusion conjunctivitis
chronic infection: trachoma
infection of newborns
opthalmia neonatorum
pneumonia syndrome of newborn
reiter’s syndrome
triad of urethritis, conjunctivitis and arthritis
occurs in about 6% of individuals following chlamydial genital infection
chlamydia penumoniae
worldwide distribution, >50% sero-prevalence
primary infection ranges from common cold-like symptoms to atypical, community-acquired pneumonia
chlamydia psittaci (avian)
zoonosis from infected birds
flu-like illness to severe pneumonia
occupational hazard for people exposed to exotic birds or poultry, BGE engineers; classified as category B biological weapon by CDC
rickettsia
gram-negative alpha-proteobacteria; difficult to gram stain ; obligate intracellular; no developmental cycle; transmission primarily through arhropods (lice, fleas, ticks); infect non-phagocytic cells, primarily endothelial cells
ricketssia virulence factors
outer membrane protein B (ompB) implicated in adhesion and invasion
phospholipase D mediates phagosomal escape
R. typhi has cytotoxic and phospholipase A2 activities which may function in phagosomal escape
