Mycobacteria

Question 1

M. Tuberculosis

Answer 1

40.9/100,000 in Singapore (not common but high in developed country)

Spread by aerosol

Intracellular survival - latency, reactivation

Acid Fast (if positive indicate contagious) -> Culture (gold standard)

Screening test: PPD and IGRA (can do with ppl who have BCS vaccination)

Combination Treatment for 6 months [2 months of 4 drugs (pyrazinamide, isoniazid, rifampin, and ethambutol (eye toxicity)) and 4 months of 2 drugs - if the culture from the beginning is not resistance to the 2 drugs], do baseline liver function test + refer to the ophthalmologist, notify MOH

No need to isolate the patient because sputum smear is negative, but if there is cavity then there is a need to do isolation.

X-Ray: patchy and not clear lung with higher condensation toward apical

Significance: May/may not be isolated (immune related forms)

Sample: 24 year old nurse / 21 year old student / 58 year old renal with Diabetes Metilitis

Question 2

Nontuberculosis Mycobaceria (NTM)

Answer 2

Environmental reservoir hence not contagious
Colonizers or opportunistic infections
Acid-fast smears (Cannot differentiate)
Cultures -Differentiate from MTB by molecular methods (HPLC or MALDI-TOF)

Question 3

Leprosy

Answer 3

Can’t be grown in the micro lab. Need histological investigation or molecular test

Th2 response (IL-4, IL-10)
No skin test response
Many skin lesion with normal hair growth, cartilage loss

Question 4

Acid Fast Positive Non-mycobacteria

Answer 4

Tsukamurella sp, Nocardia sp

To distinguish between non-mycobacteria and mycobacteria is through culture.

Question 5

Mycobacterium avium

Answer 5

Nonchromogen, Slow growing NTM, Asso. HIV; elderly female non-smoker, Treat with clarithromycin, chronic cough

60 year old female with chronic cough

Question 6

Mycobacterium abscessus

Answer 6

Nonchromogen, Rapidly growing NTM Respiratory, skin tissue infections, combination treatment for 2 months, multidrug resistance

Significance: immunity, post-procedure

Sample: 60 year old female with chronic cough

Question 7

Nocardia brasiliensis

Answer 7

Nonmycobacteria, soil bacteria, aerobic actinomycete, opportunistic pathogen, inhalation, skin inoculation, similar presentation to mycobacteria, growth rate btwn bacteria and mycobacteria (2-3 days), Weak AFB, negative on ZN stain (differentiating test), Amino acid utilization, molecular, MALDI, HPLC

Leukemia patient / 58 year old renal with Diabetes Metilitis

Question 8

Myobacterium Chimaera

Answer 8

Similar to M. intracellulare,
Water origin
Elderly with underlying COPD; bronchiectasis, haemoptysis, cavitationAerosol from heater-cooler units leading to contaminated operating field
Presentation 5 mth - 4 yrs post-op
Cause post-op baceraemia, pneumonia, endocarditis, vascular graft infection, myocarditis, osetomycelitis, thrombocytopaenia
LIPA, Hain NTMDR test, ITS sequencing
Combo treatment: quinolones, rifampin and ethambutol +/- Macrolides,