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Sophia's Path > Microbiology > Flashcards

Microbiology Flashcards

1
Q

MTB vs NTM

A

MTB - Mycobacterium Tuberculosis (droplet transmission)

NTM - Non-Tuberculosis Mycobacteria (everywhere, e.g. water, soil)

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2
Q

Mycobacterium Microcrobiology

A 
Non-motile rod shaped
Gram +ve
Intracellular
Aerobic
Thick, waxy cell wall
Relatively slow growing (cf other bacteria)
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3
Q

Mycobacterium Staining

A 
Acid alcohol fast bacilli (AAFBs)
Sputum sample:
1. Auramine - fluorescence
2. Ziehl Neelsen (ZN) Stain - stay pink when decolouriser is added
3. Gram +ve
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4
Q

NTM

A

Environmental or atypical mycobacteria
No person-to-person transmission
A/w immunosupression
Resistant to classical anti-TB tx

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5
Q

“Slow growing” NTM - M. Avium Intracellulare (MAI)/ M. Avium Complex (MAC)

A

“Slow growing”
Pulmonary - immunocompetent w/ underlying lung disease e.g. bronchiectasis, cavities, CF, COPD (resembles TB)
Children - pharyngitis/cervical adenitis
Immunosupressed = disseminated infection - cytotoxics, lymphoma, HIV (multibacilllary infection, bacteraemia - longstanding diarrhoea)

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6
Q

“Slow growing” NTM - M. Marinum

A

“Slow growing”
Swimming/fish tank pool granuloma
Single/clusters of papules/plaques
Swimming pool/aquarium owners

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7
Q

“Slow growing” NTM - M. Ulcerans

A

Skin lesions e.g. Bainsdale, Buruli ulcer
Chronic progressive painless ulcer
Seldom fatal
Deformity

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8
Q

“Rapid growing” NTM

A

M. Abscessus, M. Chelonae, M. Fortuitum

Skin/ soft tissue infection
Hospital setting - isolated from blood culture vascular catheters, other devices
Usually treat with macrolide

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9
Q

Treatment of M. Avium Intracellulare (MAI)

A

Clarithromycin/azithromycin
Rifampicin
Ethambutol
+/- Amikacin/streptomycin

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10
Q

Features of Leprosy (M. Leprae and M. Lepromatosis)

A

Lifelong illness
Incubation period 2-10 years
Transmission nasal secretions (poor)

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11
Q

Manifestations of Leprosy (M. Leprae and M. Lepromatosis)

A

Nerves = thickening/ damage –> sensory neuropathy/hypothesia
Disability secondary to nerve damage
Skin = depigmentation/ plaques/ trophic ulcers etc
Profound disfigurement
Eyes (keratitis) and bone (periositis aseptic necrosis)

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12
Q

Tx of Leprosy (M. Leprae and M. Lepromatosis)

A

Rifampicin
Dapsone
Clofazime - if multibacillary

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13
Q

Immunological Spectrum of Leprosy

A
  1. Tuberculoid (TT) - paucibacillary
    Few bacilli in skin lesions
    Th1 mediated - robust response
  2. Lepromatous (LL) - multibacillary
    Abundant bacilli in multiple skin lesions, neuropathic ulcers
    Th2 mediated - poor response

(Also in between - BT, BB, BL)

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14
Q

MTB Presentation

A 
Cough 
Haemoptyisis
Fever (night sweats)
Weightloss
Malaise
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15
Q

MTB Complex Microbiolgy

A

7 closely related species

M. bovis - infection via contact with cows (e..g unpasteurised milk)
M. africanum - West Africa

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16
Q

MTB Transmission

A

Droplet/ airborne
Infectious dose = 1-10 bacilli
Air remains infectious up to 30 mins

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17
Q

MTB Prevention

A 
BCG vaccine
Live attenuated strain M. Bovis
Babies in high prevalence communities
Efficacy 70-80% prevention of severe childhood TB
Protection wanes
Contraindicated in HIV
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18
Q

MTB Natural History

A

Primary TB
Latent TB
Reactivation (Post-primary)

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19
Q

Primary TB

A 
Asymptomatic (usually)
Ghon focus/ complex
Granuloma
Ipsilateral lymphadenopathy
Rarely - erythema nodosum
Occassionally - miliary/ diseminated
20
Q

Post-Primary TB

A

Reactivation (exogenous re-infection)
>5 year post primary
Risk factors = immunosupression, chronic alcohol use, malnutrition, ageing

21
Q

Pulmonary TB

A

Caeating granulomata - lung parenchyma, mediastinal LN

upper lobe

22
Q

Extra-pulmonary

A

Lymphadenitis - scrofula, cervical LNs
GI
Peritoneal
Genitourinary - slow progression to renal disease, spread to lower urinary tractmmon)
Bone/joint - haematogenous spread (spine/Potts disease most common)

23
Q

Spinal Tb

A

back pain
haematogenous spread
iliopsoas abscess
tx 12/12 anit-TB

24
Q

TB Drugs (1st Line)

A 
Rifampicin
- drug interaction (raised transaminases, induces CYP450), orange secretions, hepatotoxicity
Isoniazid
- peripheral neuropathy, give B6/pyrodoxine
Pyrazinamide
- hyperuricaemia, hepatotoxicity
Ethambutol
- optic neuritis
25
Q

TB Treatement

A

Isoniazid + Rifampicin + Pyrazinamide + Ethambutol = 2/12
Continue Isoniazid + Rifampicin for 4/12

(TB Meningitis - continue Isoniazid + Rifampicin for 8-10/12)

26
Q

S. pneumonia features

A 
Gram +ve diplococci
rust sputum
Lobar on CXR
(vaccine for at risk groups)
Alpha haemolytic - aerobic conditions
Beta haemolytic - anaerobic conditions
27
Q

H. influenza

A

Gram -ve cocco-bacilli
smoking/COPD (pre-existing lung disease)
chocolate agar
May produce Beta lactamase

28
Q

M. catarrhalis

A

Gram -ve coccus
Smoking
aerobic
oxidase-positive diplococcus

29
Q

S. aureus

A

Gram +ve cocci
“grape-bunch clusters”
pot-influenza infection
cavitation on CXR

30
Q

K. pneumonia

A

Gram -ve, enterobacter
Haemoptysis
Alcohol
Elderly

31
Q

Legionella pneumophilia

A 
travel/air conditioning/water towers
Hepatitis
Low Na
Can cause multi organ failure
Buffered charcoal yeast extract (special culture)
32
Q

Resp Infection in HIV

A

P. Jiroveci (PCP)
TB
Cryptococcus neoformans

33
Q

Resp Infection in Neutropenia

A

Fungi - Aspergillus spp.

34
Q

Resp Infection in Bone Marrow Tx

A

Aspergillus

CMV

35
Q

Resp Infection in Splenectomy

A

Encapsulated Organisms - H. influenza, S. pneumonia, N. meningitidis

36
Q

Resp Infection in CF

A

Pseudamonas aeruginosa

Burkholderia cepacia

37
Q

Coxiella burnettii

A

Q fever
worldwide
domestic/farm animals - transmitted yb aerosol or milk
hepatitis

38
Q

Empyema

A

Consider if not improving on Abx treatment

Difficult to treat - difficult to penetrate + acidotic environment

39
Q

CAP Organisms

A

Typical (85%)

  • S. Pneumoniae
  • H. Influenza

Atypical (15%)

  • Legionella
  • Mycoplasma
  • Coxiella burnetii
  • Chlamydia psittaci
40
Q

HAP Organisms

A 
Staph Aureus 
Enterobacteriaciae - E. Coli, Klebsiella
Pseudamonas spp.
H. Influenzae
Acinetobacter baumanii
Fungi (Candida)
41
Q

Pneumocystis jiroveci (PCP)

A 
Protozoan
Ubiquitous in environment
Insidious onset
Dry cough, weightloss, SOB, malaise
CXR: 'bats wing' (bilateral ground glass shadowing)
Dx immunoflouresence on BAK
Rx septrin (co-trimoxalose)
Immunosupressed - prophylactic septrin
Walk test - desaturate will walking - definitive indication for PCP
42
Q

Aspergillus fumigatus - resp infection

A

Allergic bronchopulmonary aspergillosis = chronic wheeze, eosinophilia, bronchiectasis

Aspergilloma - fungal ball in pre exosting cavity - haemoptysis

Invasive aspergillosis in prolonged neutropenia (immunocompromised) - treat with Amphotericin B

43
Q

Diagnosis for Resp Tract Infection

A

Urine Antigen Test - not definitive. Severe CAP - S. Pneumoniae, Legionella

Ab Test -paired serum sample (presentation + 10-14/7). Rise in Ab level - Chlamydia, Legionella (difficult to culture)

Immunofluorescence - virology - PCP detected by silver stain

44
Q

Neisseria Gonorrhoeae

A

obligate intracellular

Gram -ve diplococcus

45
Q

Gonorrhoea

A

Opathalmia neonatorum = neontal conjunctivitis - transfer from birth canal to baby

Complement deficiency = disseminated disease

Complicated infection = PID - female infertility

46
Q

Gonorrhoea Dx and Tx

A

Urethral (or rectal) smear and culture

Single dose ceftriaxone IM - 250mg
Single dose cefixime PO - 400mg
Resistant - spectinomycin IM - 2g

47
Q

Chlamydia trachomatis

A

obligate intracellular
Gram -ve
cannot be cultured on agar

Sophia's Path (8 decks)

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