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W. B. SCHAEFER
human and animal infections (Krasnow and Gross, 1975; Schaefer, unpublished data). Boisvert (1974) found niacin- and urease-positive strains
of M. intracellulare type 18 which show delayed photochromogenicity.
H. The rapidly growing mycobacteria
Among the mycobacteria that appear in clinical specimens either as
contaminants or as opportunist pathogens, there is a group distinguished
by rapid growth and lack of pigmentation. This category has been designated as Group IV by Runyon (1959). This group of strains is heterogeneous, but three predominating species have been differentiated by their
biochemical and serological characteristics. They are Mycobacterium
fortuitum, Mycobacterium chelonei (synonyms : M . abscessus and M. borstelense), and Mycobacterium peregrinum. All three give a positive reaction to
the three-day arylsulphatase test. M . fortuitum and M. peregrinum reduce
nitrate, whereas M. chelonei does not.
The three species can be identified by seroagglutination. M . fortuitum
sera are usually specific without absorption, whereas M . chelonei sera and
M . peregrinum sera become specific only after absorption by M . peregrinum
and M . chelonei strains respectively. M . fortuitum and M. chelonei strains
often produce unstable suspensions. Such strains can only be identified by
agglutinin absorption tests using M. fortuitum and ill. chelonei sera respectively. Truly rough strains are devoid of the species-specific antigens and
cannot be identified serologically (Jenkins et al., 1971).
I. Mycobacteriu m gastri, Mycobacteriu m terrae, Mycobacteriu m
triviale and Mycobacterium gordonae
M . gastri was described by Wayne (1966) as a saprophytic mycobacterium. Its colonies resemble those of M . kansasii, but are usually nonphotochromogenic. They rapidly hydrolyse Tween-80, lack nitrate
reductase, and have a moderately positive catalase test. They are specifically
agglutinated by M . gastri antisera (Schroder and Magnusson, 1970), and
their methanol or phenol extracts give a specific precipitin band with the
same sera (Wayne, 1971a, b). Immunodiffusion analyses of culture filtrates
show a high degree of antigenic similarity between cytoplasmic antigens
of M . gastri and M. kansasii (Norlin et al., 1969).
M. terrae, also described by Wayne (1966), is a saprophyte producing
pale buff to white colonies. It rapidly hydrolyses Tween-80, reduces
nitrate moderately, and has a high catalase activity. Antigenically, M .
terrae is heterogeneous.
M . gordonae is the name for a widely spread group of saprophytic,
scotochromogenic mycobacteria. It hydrolyses Tween-80 which readily
distinguishes it from iM. scrofulaceum. M . gordonae includes many sero-
W. B. SCHAEFER
human and animal infections (Krasnow and Gross, 1975; Schaefer, unpublished data). Boisvert (1974) found niacin- and urease-positive strains
of M. intracellulare type 18 which show delayed photochromogenicity.
H. The rapidly growing mycobacteria
Among the mycobacteria that appear in clinical specimens either as
contaminants or as opportunist pathogens, there is a group distinguished
by rapid growth and lack of pigmentation. This category has been designated as Group IV by Runyon (1959). This group of strains is heterogeneous, but three predominating species have been differentiated by their
biochemical and serological characteristics. They are Mycobacterium
fortuitum, Mycobacterium chelonei (synonyms : M . abscessus and M. borstelense), and Mycobacterium peregrinum. All three give a positive reaction to
the three-day arylsulphatase test. M . fortuitum and M. peregrinum reduce
nitrate, whereas M. chelonei does not.
The three species can be identified by seroagglutination. M . fortuitum
sera are usually specific without absorption, whereas M . chelonei sera and
M . peregrinum sera become specific only after absorption by M . peregrinum
and M . chelonei strains respectively. M . fortuitum and M. chelonei strains
often produce unstable suspensions. Such strains can only be identified by
agglutinin absorption tests using M. fortuitum and ill. chelonei sera respectively. Truly rough strains are devoid of the species-specific antigens and
cannot be identified serologically (Jenkins et al., 1971).
I. Mycobacteriu m gastri, Mycobacteriu m terrae, Mycobacteriu m
triviale and Mycobacterium gordonae
M . gastri was described by Wayne (1966) as a saprophytic mycobacterium. Its colonies resemble those of M . kansasii, but are usually nonphotochromogenic. They rapidly hydrolyse Tween-80, lack nitrate
reductase, and have a moderately positive catalase test. They are specifically
agglutinated by M . gastri antisera (Schroder and Magnusson, 1970), and
their methanol or phenol extracts give a specific precipitin band with the
same sera (Wayne, 1971a, b). Immunodiffusion analyses of culture filtrates
show a high degree of antigenic similarity between cytoplasmic antigens
of M . gastri and M. kansasii (Norlin et al., 1969).
M. terrae, also described by Wayne (1966), is a saprophyte producing
pale buff to white colonies. It rapidly hydrolyses Tween-80, reduces
nitrate moderately, and has a high catalase activity. Antigenically, M .
terrae is heterogeneous.
M . gordonae is the name for a widely spread group of saprophytic,
scotochromogenic mycobacteria. It hydrolyses Tween-80 which readily
distinguishes it from iM. scrofulaceum. M . gordonae includes many sero-