mycoplasma Flashcards
characteristics of mycoplasma
little to no peptidoglycan, hence gram staining cannot be used to visualise
beta lactams do not work against mycoplasmas
characteristics of mycoplasma spp.:
not obligate intracellular pathogens
no peptidoglycan in cell envelopes
naturally resistant to penicillins and cephalosporins
characteristics of chlamydia spp.:
obligate intracellular pathogens
little peptidoglycan in cell envelopes
possesses penicillin binding proteins but beta lactams are still not the best treatment possible
infectious form = elementary body, enters host cell and replicates inside a membrane-bound vesicle in second form = reticular body; new eb are formed and released from the cel
name the 3 bacteria of the mycoplasma spp.:
mycoplasma pneumoniae
mycoplasma hominis
mycoplasma genitalium
mycoplasma pneumoniae: clinical presentations
walking pneumonia: most do not become seriously ill, hence become agents for transmission, patchy opacities are often seen on x-ray
paroxysmal cough in children; may be confused with whooping cough
serious disease in immunocompromised and sickle cell anemia patients
other complications include: stevens johnson syndrome, joint pains, encephalitis, meningitis, hemolytic anemia, myocarditis, pericarditis
mycoplasma pneumoniae: diagnosis
typically clinical; serology is not very useful and culture is difficult
serology: cold agglutinins are produced in 50% of the patients (antibiotics react with the I antigen present on all human RBCs, most easily detectable at 4degc)
specific serology: complement fixation test, igM assays (observe rising titres in)
mycoplasma pneumoniae: treatment
erythromycin, tetracycline or respiratory quinolone for 2-3 weeks
mycoplasma hominis: culture
fried egg colonies
mycoplasma hominis: clinical presentations
uti, renal stones
bacterial vaginosis, pelvic inflammatory disease
post-abortion/post-partum fever, premature neonatal meningitis, neonatal respiratory tract infections
post transplant infections
**ureaplasma urealyticum can also cause such infections
mycoplasma genitalium: histology
genitalia appearance
mycoplasma genitalium: clinical presentations
non-gonococcal urethritis
bacterial vaginosis, pelvic inflammatory disease
chlamydophilia pneumoniae: clinical presentations
atypical pneumonia in young adults (common cause), bronchitis, sinusitis
possible association with atherosclerosis and coronary heart disease; unclear evidence
chlamydophilia pneumoniae: treatment
tetracyclines or macrolides (erythromycin)
chlamydophilia psittaci: transmission
zoonosis (acquired from birds) - NOT person to person
chlamydophilia psittaci: clinical presentations
flu like initial illness leading to pneumonia
dissemination of infection may lead to infection of brain, meninges, heart, joints
rare cause of endocarditis
chlamydophilia psittaci: treatment
tetracyclines or macrolides (erythromycin)
chlamydia trachomatis - oculogenital biovars A, B, Ba, C: character
acquired mainly from human sources
chlamydia trachomatis - oculogenital biovars A, B, Ba, C: transmission
flies, fingers and fomites
chlamydia trachomatis - oculogenital biovars A, B, Ba, C: clinical presentations
trachoma - eye infection leading to eventual blindness
pannus formation (clouding of the cornea) chrnic inflammation of eyelids lead to scarring of eyelids and secondary scarring of cornea
**protective immunity does not develop, hence repeated infections occur
chlamydia trachomatis - oculogenital biovars A, B, Ba, C: diagnosis
applies to all chlamyodia
culture, molecular methods (pcr, nucleic acid amplification techniques - preferred for all c. trachomatis)
chlamydial fixation test (only genus-specific)
microimmunofluorescence (detects species and serovar specific antibodies)
chlamydia trachomatis - oculogenital biovars A, B, Ba, C: treatment
tetracyclines or macrolides (erythromycin)
chlamydia trachomatis - lymphogranuloma venereum (LGV) biovars L1, L2, L3: character
mostly in the tropics and subtropics
chlamydia trachomatis - lymphogranuloma venereum (LGV) biovars L1, L2, L3: transmission
sexually transmitted disease
chlamydia trachomatis - lymphogranuloma venereum (LGV) biovars L1, L2, L3: clinical presentations
primary lesions: small papule/vesicle on genitalia
infection spreads to regional lymph nodes which enlarge, suppurate and discharge through sinuses; males - inguinal glands; females and homosexual males - perirectal glands suppurate, leading to proctitis and bloody anal discharge
chronic inflammation can lead to rectal stricture and bloody anal discharge
chlamydia trachomatis - lymphogranuloma venereum (LGV) biovars L1, L2, L3: treatment
tetracyclines or macrolides (erythromycin)
chlamydia trachomatis - lymphogranuloma venereum (LGV) biovars L1, L2, L3: prevention
contact tracing, screening of high risk people, condoms, education
chlamydia trachomatis - oculogenital biovars D-K: character
common in developed countries
chlamydia trachomatis - oculogenital biovars D-K: transmission
sexually transmitted disease, autoinfection (fingers - eyes)
chlamydia trachomatis - oculogenital biovars D-K: clinical presentations
males: important cause of non-gonococcal urethritis, common asymptomatic carriage, infection may spread to epididymis and prostate, proctitis in homosexual males
females: mucopurulent cervicitis, urethritis, acute salpingitis, pelvic inflammatory disease, fitz-hugh-curtis syndrome, proctitis
in both genders: adult inclusion conjunctivitis due to autoinfection with fingers (paratrachoma)
in neonates: ophthalmia neonatorum due to endocervical inflammation in mother, pneumonia, staccato sough
chlamydia trachomatis - oculogenital biovars D-K: treatment
tetracyclines or macrolides (erythromycins);
note - erythromycin is needed to treat ophthalmia neonatorum to prevent subsequent pneumonitis
name the obligate intracellular pathogens
rickettsia, ehrlichia, coxiella spp.
coxiella is sporing, the other 2 are non sporing
coxiella burnetii: character
spore forming, replicates in acidified phagolysosome of macrophages, naturally infects sheep, cattle and goats
alot of shedding in urine, faeces and milk
coxiella burnetii: transmission
zoonosis, inhalation of airborne spores, drinking of infected milk
coxiella burnetii: clinical presentations
acute q fever - most become infected asymptomatically or suffer only minor symptoms; some present with pneumonia, hepatitis and/or PUO (pyrexia with unknown origin)
chronic q fever: endocarditis (culture negative; does not grow in conventional blood culture system)
coxiella burnetii: diagnosis
serology, pcr and culture at reference labs only
coxiella burnetii: treatment
doxycycline (for acute infection), hydroxychloroquine - weak base which diffuses into phagolysosomes to increase pH, disrupting bacterial replication
characteristics of rickettsia & orientia spp.
small gram negative rods that reproduce in endothelial cells
transmitted by zoonosis, through arthropod vectors
name the 3 groups of the rickettsia & orientia spp.
typhus group, spotted fever group, scrub typhus group
rickettia & orientia spp.: transmission
typhus group (r. prowazekii, r. typhi) - transmitted by louse or flea
spotted fever group (r. rickettsii, r. akari, r. felis) - transmitted by ticks
scrub typhus group (orientia tsutsugamushi) - transmitted by chiggers (parasitic larval stage of a mite)
exceptions: r. akari - mouse mite; r. felis - cat flea
rickettia & orientia spp.: clinical presentations
general features:
pyrexia with unknown origin, with headache and muscle pain
skin rash (rickettsialpox: eventually vesicular)
with severe disease bacterial replication damages the endothelium so badly that hypotension ensues, leading to hypoperfusion of organs and multiple organ failure. less severe vasculitis can cause dry gangrene due to vessel compromise
eschar: ulcer with dark/black crust (seen in spotted fever and scrub typhus infections)
specific features:
r. prowazekii: epidemic typhus, infection kills louse vector, infection may reactivate after many years (Brill-Zinsser disease) - main reservoir is man, centrifugal rash; meaning rash is concentrated on the extremities
r. typhii: murine typhus
r. rickettsii: rocky mountain spotted fever, centripetal rash; meaning rash is concentrated in the torso
r. akari: rickettsialpox
r. felis: flea borne spotted fever
o. tsutsugamushi: scrub typhus
rickettsia & orientia spp.: diagnosis
weil-felix test (low specificity & sensitivity, no longer the method of choice)
serology
rickettsia & orientia spp.: treatment
doxycycline, chloramphenicol
**antibiotic resistant strains of o. tsutsugamushi are found in northern thailand
rickettsia & orientia spp.: prevention
delousing at-risk population (construction workers, imported diseases endemic in malaysia - tick, murine, and scrub typhus)
