Respiratory Treatment and Prevention (Advances in Experimental Medicine and Biology)

1 Introduction and Taxonomy

Non-tuberculous mycobacteria (NTM) are spe-
cies other than those belonging to theMycobac-
terium tuberculosiscomplex and do not cause
leprosy. NTM are generally free-living
organisms that are ubiquitous in the environ-
ment. There have been more than 140 NTM spe-
cies identified to-date. They can cause a wide
range of mycobacterial infections, with pulmo-
nary infections being the most frequent
(65–90 %) (van Ingen et al.2012d).
Mycobacteria are aerobic, non-motile
organisms that appear positive with acid-fast
alcohol staining. They have a lipid rich, hydro-
phobic cell wall, substantially thicker than that of
the most other bacteria. The thickness and com-
position of the cell wall renders mycobacteria
impermeable to hydrophilic nutrients and resis-
tant to heavy metals, disinfectants, and
antibiotics (Jarlier and Nikaido 1994 ). Four
groups of human pathogens are recognized in
theMycobacteriumgenus: (1)Mycobacterium
tuberculosis complex, (2) Mycobacterium

leprae,(3) slowly growing NTM, and (4) rapidly

growing mycobacteria.

Historically, NTM have been classified by

according to their growth rate and pigment for-

mation (Runyon 1959 ) (Fig.1). Types I, II, and

III, so-called slow growers take 7 days or more to

grow, and have been classified by their colora-

tion. If the pigment is produced only on exposure

to light, they are photochromogens (type I); if it

is produced in the dark, they are

scotochromogens (type II); if the bacteria are

not strongly pigmented, they are

non-photochromogens (type III). Rapid growers

(type IV) grow in less than 7 days, which how-

ever, is still more slowly than most other bacteria

do.

2 Epidemiology

Infections caused by NTM differ on several

points from the classical epidemiology of tuber-

culosis (TB):

NTM

>7 days

Slow growers

Type I

M. kansasii

M. marinum

Type II

M. gordonae

M. scrofulaceum

Type III

MAC - M. avium, M. intracellulare

M. xenopi

M. ulcerans

M. terrae

M. haemophilum

< 7 days

Rapid growers

Type IV

M. fortuitum

M. abscessus

M. chelonae

Fig. 1 Classification of non-tuberculous mycobacteria (NTM) (Adapted from Runyon 1959 )

20 I. Porvaznik et al.