LECTURE - Mycoplasmas, Chlamydia, and Treponema Flashcards
Mycoplasma characteristics
gram neg but no peptidoglycan; very small genomes; pliable shape makes them look like junk; pleomorphic
- require lipids and enriched medium to grow
- live in close association with host cells but on outside (not intracellularly)
- colonies = fried egg appearance
- single cell membrane = cholesterol (From medium or host; don’t synthesise it)
- smallest free-living microorganisms
walking pneumoniae
Mycoplasma pneumonia
- sick but not sick enough to be hospitalaized
- young adults
- X-ray = moth-eaten appearance ; typical pneumonia = compact areas of density with clear edges
cells of Mycoplasma pneumoniae hve:
- unique shape
- show gliding motility
- special attachment organelle
- P1 = main protein involved in adherence
- one end is cytoadherence organelle and the other is gliding end
cell membrane of M. pneumoniae
- asymmetrical
- lipoprotein in outer leaflet cause inflammation like LPS; can possess antigenic differences among different strains
M. pneumoniae pathogenesis
- organisms inhaled
- bind to base of ciliated cells in lung through its cytadherence organelle
- depolarize cells and cause ciliastasis
- lipoprotein of outer leaflet membrane triggers inflammation
- peroxide and other reactive O2 species => ciliated cell death and phospholipase may damage host cells
- big virulence = community-acquired resp disease syndrome (CARDS) toxin
- B cells ad T cells simulated non-specifically = Abs bind to RBCs in cold = cold agglutinins formed
M. pneumoniae pathogenesis
- organisms inhaled
- bind to base of ciliated cells in lung through its cytadherence organelle
- depolarize cells and cause ciliastasis
- lipoprotein of outer leaflet membrane triggers inflammation
- peroxide and other reactive O2 species => ciliated cell death and phospholipase may damage host cells
- big virulence = community-acquired resp disease syndrome (CARDS) toxin
- B cells ad T cells simulated non-specifically = Abs bind to RBCs in cold = cold agglutinins formed
diagnosis of M. pneumoniae
- slow-growing = takes 3-6 wks for positive results
- paired sera in using a commercial serology test can confirm etiology
- PCR available but expensive
treatment for M. pneumoniae
azithromycin (other macrolide)
- resistant strains are making headway in Asia, so tetracyclines or fluoroquinolones are backup
genital mycoplasmas
M. genitalium
M. hominis
Ureaplasma spp.
non gonococcal urethritis and cervicitis
Ureaplasma urealyticum
mechanism of Ureaplasma urealyticum
- E production from hydrolysis on urea
- shapeless mycoplasmas = growth advantage on genital tract
- production of ammonia may contribute to local tissue destruction and pathology
- colonize infant at birth but usually disappear by 2 y/o
- adults acquire bu sexual contact; male exudate is more watery
- women are more commonly colonized than men
- lower socioeconomic groups
- 14 serotypes known
the colonies of this organism shows a fried egg appearance
Ureaplasma urealyticum
an emerging cause of STD in women
Mycoplasma genitalium
this is similar to gonococcal pillin
Mycoplasma genitalium terminal organelle
> MgpB and MgpC = undergo phase and antigenic variation through a reciprocal recombination system similar to gonococcal pillin
This is available for detecting M. genitalium in urine, urethral, and endocervical or vaginal swab
rapid nucleic acid amplification test
M. genitalium is present in the general population at rates between those of __ and ___
Chlamydia trachomatis and Neisseria gonorrhoeae
Chlamydial developmental cycle
- attachment and invasion of elementary body (in aa membrane bound inclusion)
- within inclusion = EBs differentiate into a metabolically active and replicatnig reticulate bodies (RBs); closely interacts with host cell
- end of developmental cycle = RBs go bak to being EBs = released by cell lysis or by extrustion of inclusion and can start a new round of infection
- limited growth conditions and antibiotics = reversible arrest of growth or persiistence with RBs transforming into enlarged aberrant bodies (ABs)
1 cause of STI in NA and leading cause of acquired blindness in world
Chlamydia trachomatis
three possible diseases caused by Chlamydia trachomatis
- trachoma = potentially blinding eye infection
STIs:
- typical chlamydia infection
- Lymphogranuloma Venereum (LGV) = infected lymph nodes (bubos) in groin
type of disease is associated with specific serovars of the organism
LGV more common here than in NA
- tropical countries
- but in NA and Europe there is an increasing incidence of infectious proctitis by LGV strains in MSM with HIV infections
most common of the bacterial STIs
- Chlamydia
- spread by fluids during vaginal and anal intercourse; or from a pregnant woman to her fetus during birth (can happen with gonorrhea too)
- often asymptomatic in females and sometimes males
- asymptomatic doesn’t mean safe!!!!; can cause ascending disease; can infect fallopian tubes = sterility , etc.
chlamydia infection in women
- bleeding between menstrual periods
- vaginal bleeding after intercourse
- abdominal pain
- painful intercourse
- low-grade fever
- painful urination
- uge to urinate ore often
- cervical inflammation
- abnormal vaginal discharge
- mucopurulent cervicitis (yellowish discharge that may have foul discharge
- PID (pelvic inflammatory disease)
- ectopic pregnancy
PID
- infection of fallopian tubes, ovaries, and/or uterus characterized by lower abdominal pain during menstruation, irregular menstruatioon, fever, chills
- scarring may cause infertility by blocking fallopian tubes
ectopic pregnancy
development of fetus in fallopian tube which causes rupture of fallopian tubes
chlamydial infection in males symptoms
- watery or milky discharge from penis, pain or burning when urinating, and swollen or tender testicles
- epididymitis
- reactive arthritis (Reiter’s syndrome): more men than women
Epididymitis
spread from urethra to testicle (fever, swelling, and extreme pain in scrotum)
- can lead to sterility
C. trachomatis and trachoma
- passed from eyes of one peson to another by flies, fingers, shared clothing/towels
- repeated infection = scarring of inner part of upper eyelid = turns lashes inwards so it scratches eyeball and cornea
- eyelid scarring = poor tea secretion and drying of eye; increase risk of corneal ulceration => impaired vision and irreversible blindness
T or F. blindness due to trachoma is irreversible
T!
but can be prevented
- SAFE strategy
> surgery for trichiais
> antibiotics to treat C. trachomatis infection
> facial cleanliness
> environmental improvement to reduce transmission
Chlamys
- cloak draped around the shoulder = intracytoplasmic inclusions caused by bacterium are draped around infected cells’ nucleus
C. trachomatis characteristics
- obligate intracellular pathogen = cant grow C. trachomatis in artificial media; have to be tissue culture
- gram neg type cell wall but no peptidoglycan
- smaller diameter than most bacteria
- small genome
- EB and RBs (two stages of life)
C. trachomatis EB attachment and entry
- EBs internalized by phagocytosis or receptor-medidated endocytosis
- endosome is not acidified and Inc proteins inhibit function with lysosome; EB cell wall prevents phagolysosomal fusion and hence allows for intracellular surivial
- endosomes containing EBs fuse together; unique to this organism!
- phosphorylation of host cell proteins induces changes n actin cytoskeleton causing endosomes to move to the perinuclear region; glycogen is deposited with the inclusion
- EBs differentiate into RBs
how does C. trachomatis avoid lysis without peptidoglycan?
EB membranes contain proteins with multiple disulfide cross-links
major outer membrane protein (MOMP) = porin and maybe attachment
polymorphic outer membrane protein (POMP)
small and large cysteine-rich proteins = functional equivalent to peptidoglycan since they allow for intracellular division and extracellular survival
RBs protected by high osmolarity in interior of human cell
detecting Chlamydia
- traditional way > cultivate bacteria in tissue culture cells - current way > PCR > fluorescent monoclonal antibody
** presence of glycogen within incisions detected by iodine staining **
prevention and treatment for Chlamydia
- abstinence and safe sex
- antibiotics = doxycycline (tetracycline) or azithromycin (macrolide)
- erythromycin ophthalmic ointment for newboarns
best target for a vaccine for Chlamydia
proteins that affect EB entry bc once inside cell, Chlamydia is protected from Abs
> human cells infected do NOT display bacterial antigens on surface; so T cells attracted by CTLs not very effective
cause of atypical pneumonia
Chlamydia pneumoniae
- same structure and same life cycle
- atypical pneumonia esp. in young adults
- associated with atherosclerotic plaques in heart
Chlamydia pneumoniae invades…
endothelial cells and triggers a profound inflammatory response
chlamydial infection in infants symptoms
- 20-50% of children born to women with chlamydia will be infected
- conjunctivitis or pneumonia (can be fatal) so all babies should be treated with appropriate antibiotics (erythromycin)
- prematue delivery, miscarriage, stillbirth, or low birthweight
C. trachomatis inside host cells
- RBs replicate
- endosome enlarges to fit all; T3SS expressed (for cytoplasmic nutrients acquisition?)
- RB Inc (inclusion) proteins insert into endosomal membrane = fuses with Golgi fragments = RBs differentiate into EBs = move to center of endosome
- 40h post infection = endosomal membrane disintegrate = release EBsinto host cytoplasm = infect adjacent cells OR…
- endosome fuses with host cytoplasmic membrane to release EBs and RBs (lyse rapidly) into extracellular space
how are spirochetes unique?
genetically distinct from other bacteria, despite their overall gram neg-like structure
spirochetes structure
- stain lie a gram neg; has IM and OM
- no LPS in OM, instead = lipoproteins
- Ab to OM proteins can kill organisms if complement is activated
- corkscrew motility due to flagella (axial filament) that is attached at both poles of the cell
- long, thin with distinctive wavelength and amplitude of coils
spirochetes causing human infection
- Treponema pallidum = syphilis
- Treponema pertenue = yawm a tropical multi-organ disease spread by physical contact
- Leptospira interrogans = Weil’s disease; water-contaminated w infected rodent urine is ingested or enters wounds, causes multi-organ infection (eg: renal failure)
- Borrelia hermsii or B. burgdorferi (tick-borne); B. recurrentis (louse-borne) relapsing fever
T. pallidum
- gram neg spirochete but no antigenic variation
- virulent strains grown in rabbit testes bc they cannot be cultivated in artificial medium; avirulent grown on artificial media
- can be transmitted transplacentally
- STD
stages of syphilis
- primary: typically painless raised and ulcerated lesion (chancre)
- secondary: rash and fever as organisms invade multiple organs
- latent: Ab rises but organisms are not easily detected
- tertiary: slowly progressing inflammatory disease with neurological symptoms, heart damage,, disfiguring lesions in skin
this is a good screen for T. pallidum
Cardiolipin
- released from mitochondria by several diseases so Ab to it is not specific but a good screen
reliable diagnosis for syphilis
serology
- specific serologic tests based on a patient Ab to T. pallidum antigens
T or F. syphilis is still treatable with penicillin
T!
