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mycoplasma Flashcards

1
Q

characteristics of mycoplasma

A

little to no peptidoglycan, hence gram staining cannot be used to visualise

beta lactams do not work against mycoplasmas

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2
Q

characteristics of mycoplasma spp.:

A

not obligate intracellular pathogens
no peptidoglycan in cell envelopes
naturally resistant to penicillins and cephalosporins

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3
Q

characteristics of chlamydia spp.:

A

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

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4
Q

name the 3 bacteria of the mycoplasma spp.:

A

mycoplasma pneumoniae
mycoplasma hominis
mycoplasma genitalium

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5
Q

mycoplasma pneumoniae: clinical presentations

A

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

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6
Q

mycoplasma pneumoniae: diagnosis

A

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)

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7
Q

mycoplasma pneumoniae: treatment

A

erythromycin, tetracycline or respiratory quinolone for 2-3 weeks

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8
Q

mycoplasma hominis: culture

A

fried egg colonies

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9
Q

mycoplasma hominis: clinical presentations

A

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

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10
Q

mycoplasma genitalium: histology

A

genitalia appearance

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11
Q

mycoplasma genitalium: clinical presentations

A

non-gonococcal urethritis

bacterial vaginosis, pelvic inflammatory disease

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12
Q

chlamydophilia pneumoniae: clinical presentations

A

atypical pneumonia in young adults (common cause), bronchitis, sinusitis

possible association with atherosclerosis and coronary heart disease; unclear evidence

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13
Q

chlamydophilia pneumoniae: treatment

A

tetracyclines or macrolides (erythromycin)

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14
Q

chlamydophilia psittaci: transmission

A

zoonosis (acquired from birds) - NOT person to person

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15
Q

chlamydophilia psittaci: clinical presentations

A

flu like initial illness leading to pneumonia
dissemination of infection may lead to infection of brain, meninges, heart, joints
rare cause of endocarditis

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16
Q

chlamydophilia psittaci: treatment

A

tetracyclines or macrolides (erythromycin)

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17
Q

chlamydia trachomatis - oculogenital biovars A, B, Ba, C: character

A

acquired mainly from human sources

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18
Q

chlamydia trachomatis - oculogenital biovars A, B, Ba, C: transmission

A

flies, fingers and fomites

19
Q

chlamydia trachomatis - oculogenital biovars A, B, Ba, C: clinical presentations

A

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

20
Q

chlamydia trachomatis - oculogenital biovars A, B, Ba, C: diagnosis

A

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)

21
Q

chlamydia trachomatis - oculogenital biovars A, B, Ba, C: treatment

A

tetracyclines or macrolides (erythromycin)

22
Q

chlamydia trachomatis - lymphogranuloma venereum (LGV) biovars L1, L2, L3: character

A

mostly in the tropics and subtropics

23
Q

chlamydia trachomatis - lymphogranuloma venereum (LGV) biovars L1, L2, L3: transmission

A

sexually transmitted disease

24
Q

chlamydia trachomatis - lymphogranuloma venereum (LGV) biovars L1, L2, L3: clinical presentations

A

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

25
Q

chlamydia trachomatis - lymphogranuloma venereum (LGV) biovars L1, L2, L3: treatment

A

tetracyclines or macrolides (erythromycin)

26
Q

chlamydia trachomatis - lymphogranuloma venereum (LGV) biovars L1, L2, L3: prevention

A

contact tracing, screening of high risk people, condoms, education

27
Q

chlamydia trachomatis - oculogenital biovars D-K: character

A

common in developed countries

28
Q

chlamydia trachomatis - oculogenital biovars D-K: transmission

A

sexually transmitted disease, autoinfection (fingers - eyes)

29
Q

chlamydia trachomatis - oculogenital biovars D-K: clinical presentations

A

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

30
Q

chlamydia trachomatis - oculogenital biovars D-K: treatment

A

tetracyclines or macrolides (erythromycins);

note - erythromycin is needed to treat ophthalmia neonatorum to prevent subsequent pneumonitis

31
Q

name the obligate intracellular pathogens

A

rickettsia, ehrlichia, coxiella spp.

coxiella is sporing, the other 2 are non sporing

32
Q

coxiella burnetii: character

A

spore forming, replicates in acidified phagolysosome of macrophages, naturally infects sheep, cattle and goats

alot of shedding in urine, faeces and milk

33
Q

coxiella burnetii: transmission

A

zoonosis, inhalation of airborne spores, drinking of infected milk

34
Q

coxiella burnetii: clinical presentations

A

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)

35
Q

coxiella burnetii: diagnosis

A

serology, pcr and culture at reference labs only

36
Q

coxiella burnetii: treatment

A

doxycycline (for acute infection), hydroxychloroquine - weak base which diffuses into phagolysosomes to increase pH, disrupting bacterial replication

37
Q

characteristics of rickettsia & orientia spp.

A

small gram negative rods that reproduce in endothelial cells

transmitted by zoonosis, through arthropod vectors

38
Q

name the 3 groups of the rickettsia & orientia spp.

A

typhus group, spotted fever group, scrub typhus group

39
Q

rickettia & orientia spp.: transmission

A

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

40
Q

rickettia & orientia spp.: clinical presentations

A

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

41
Q

rickettsia & orientia spp.: diagnosis

A

weil-felix test (low specificity & sensitivity, no longer the method of choice)

serology

42
Q

rickettsia & orientia spp.: treatment

A

doxycycline, chloramphenicol

**antibiotic resistant strains of o. tsutsugamushi are found in northern thailand

43
Q

rickettsia & orientia spp.: prevention

A

delousing at-risk population (construction workers, imported diseases endemic in malaysia - tick, murine, and scrub typhus)

microb (12 decks)

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