Mycology and Tuberculosis

Mycology is the study of fungi.

There are 3 levels of mycobacteriology laboratory service:-

Level 1 : responsible for collecting and shipping specimens. If bio-safety requirements are met, Level 1 labs may also prepare smears and acid-fast stains (AFB - acid-fast bacilli) for microscopy.

Level 2 : performs Level 1 services and recover organisms by culture, identify isolates of m.tuberculosis and refer non-m.tuberculosis isolates of mycobacteria to Level 3.

Level 3 : performs all Levels 1 and 2 services, identify all species of mycobacterium and perform drug susceptibility tests.


Tuberculosis

Symptoms include persistent cough, fever, weight loss.

Confirmation is by tuberculin skin test, chest x-ray.

Definite diagnosis is made after isolation and identification of infecting organism in the lab:-

1) Decontamination, digestion, concentration of specimen
2) Microscope examination for acid-fast bacilli (AFB) on smears
3) Isolation by culture
4) Tests to identify recovered bacilli
5) Tests for drug susceptibility

M.tuberculosis notes:-

1) Culturing and identification is a long process. May take many days to report.
2) There are 25 species of mycobacterium, of which m.tuberculosis is one of the five most frequently encountered pathogenic species.
3) M.tuberculosis is transmitted by droplet. Therefore breaking or leaking during centrifuging is a hazard.
4) Bio-safety Laboratory Practice 3 (BSL-3) must be followed. Aerosol-generating procedures should be done in Class I or Class II biological safety cabinets, and centrifuging in aerosol-free cups.
5) Laboratory layout should provide separate areas for different activities.
6) BSL-2 space for preparing material and handling cultures and specimens.
7) BSL-3 space for manipulating cultures and specimens.
8) BSL-3 has safety cabinet and centrifuge, non-permeable walls and surfaces, low air pressure, air-lock, and HEPA filters direct to atmosphere.
9) Technicians should wear protective clothing and respirators. A changing room is therefore needed.