- Email: [email protected]
Mycobacteriological identification how much? How far?
Ill
Editorial I
Mycobacteriological Identification H o w Much? H o w Far?
I!
Table 1 Organisms Likely to be Recovered from Cultures of Pulmonary Secretions
Lawrence G. Wayne, Ph.D. Tuberculosis Research Laboratory Veterans Administration Hospital Long Beach,~ California Since the discovery of the tubercle bacillus in the late 19th century, Mycobacterium has been one of the most intensely studied genera of bacteria. Nevertheless, the sixth edition of Bergey's Manual o f Determinative Bacteriology, published in 1948, described only 13 species of mycobacteria and only one of these, Mycobacterium tuberculosis, was described as a h u m a n p u l m o n a r y pathogen. At that time two varieties of M. tuberculosis were considered, homhtis and bovis. The task of a clinical laboratory then was to determine whether a given isolate was M. tuberculosis or not and, at most, to establish the variety. In 1954, T i m p e and Runyon recognized the clinically significant "atypical" mycobacteria, and their discovery led to a burst of taxonomic activity. F o r a while the classification of mycobacteria, other than M. tuberculosis, into Runyon Groups, served a useful clinical purpose. It is now recognized that each of the four groups is comprised of a n u m b e r of species with different diagnostic and prognostic significance. At this writing, 38 species of mycobacteria are recognized, and of these, 14 have been implicated as agents of h u m a n lung disease. Should a clinical laboratory be expected to identify all of these organisms? A clinical isolate is identified to help answer one or more of the following questions: Is this organism likely to be the cause of the patient's disease, or is it merely a contaminant? If it is the etiologic agent, how is the disease best managed clinically? W h a t are the public health implications of this organism? In most cases, the routine public health implications are defined once an acid fast isolate is identified as M. tuber-
Acceptable Le~wl of Identification 3t. tuberculosis 3I. bovis complex 3t. kansasii 31. avium/ intracellulare complex M. scrofidaceum MAIS complex
31. xenopi AL gordonae 3L gastri M. terrae complex "Other slow growers" AL fortuitum complex "Other rapid growers"
Species Included ~L M. M. 3L
tuberculosis bovis, M. africanum kansasii avium, 5L intracellulare
3L scrofulaceum Strains intermediate between AL avium and ~L scrofulaceum, as well as ~L simiae and AL asiaticum M. xenopi 3L gordonae AL gastri M. terrae. AL nonchromogenicum, and M. triviale 3L szulgai, M. malmoense 3L fortuitum, 3L chelonei At least 10 species
culosis or M. bovis, rather than some other Mycobacterium. The precise identification to species, subspecies, and serotype for epidemiologic purposes is best left to the highly specialized reference laboratory. To establish the probable clinical significance of the isolate ,and to guide the physician in managing the disease, it is usually sufficient to place mycobacteria, other than M. tuberculosis, into one of several complexes. A guide to the acceptable level of identification of organisms likely to be isolated from pulmonary secretions follows in Table 1. Any laboratory that cultures specimens for mycobacteria should be able to recognize M. tuberculosis and to distinguish it from other
Editors:
Human Pathogen? Yes Yes Usually Often Sometimes Sometimes
Sometimes No No No Sometimes Sometimes No
mycobacteria. Depending upon the volume of mycobacteriology done in a given laboratory and the available expertise, mycobacteria other than M. tuberculosis may be identified on the premises; otherwise, the culture must be sent to a referral laboratory that is capable of identifying it to the acceptable species or complex level as previously cited. Only under unusual circumstances will it be necessary to further refer a strain to one of the few laboratories capable of identifying all cultures to a species or subspecies level. Reference American Thoracic Society. 1977. Referral without guilt, or how far should a good lab go? (Available from local branches of the American Lung Association.)
Donna J. Blazevic, L. R. McCarthy, and Josephine A. Morello
Subscription Rates in U.S. and Canada: one year S42.50; two years $80.00; three years $ 110.00. All other countries: one year $57,,50; two years S 109.50; three years $153.25. Single copies are $2.00 in U.S. and Canada, $2.65 all other countries. Single issues are available in quantity (prices available upon request). All subscriptions are payable in advance. Foreign subscriptions are sent guaranteed air mail. First class postage paid in U.S. and Canada. Address correspondence iegarding subscription to: Clinical Aficrobiology Newsletter. G. K. Hall & Co., 70 Lincoln St., Boston, Massachusetts 0211 i. Please include zip code in subscription address. The Clinical Microbiology Newsletter is published twice monthly. All rights, including that of translation into other languages, reserved. Photomechanical reproduction (photocopy, microcopy) of this newsletter or parts thereof without special permission of the publisher is prohibited.
Editorial I
Mycobacteriological Identification H o w Much? H o w Far?
I!
Table 1 Organisms Likely to be Recovered from Cultures of Pulmonary Secretions
Lawrence G. Wayne, Ph.D. Tuberculosis Research Laboratory Veterans Administration Hospital Long Beach,~ California Since the discovery of the tubercle bacillus in the late 19th century, Mycobacterium has been one of the most intensely studied genera of bacteria. Nevertheless, the sixth edition of Bergey's Manual o f Determinative Bacteriology, published in 1948, described only 13 species of mycobacteria and only one of these, Mycobacterium tuberculosis, was described as a h u m a n p u l m o n a r y pathogen. At that time two varieties of M. tuberculosis were considered, homhtis and bovis. The task of a clinical laboratory then was to determine whether a given isolate was M. tuberculosis or not and, at most, to establish the variety. In 1954, T i m p e and Runyon recognized the clinically significant "atypical" mycobacteria, and their discovery led to a burst of taxonomic activity. F o r a while the classification of mycobacteria, other than M. tuberculosis, into Runyon Groups, served a useful clinical purpose. It is now recognized that each of the four groups is comprised of a n u m b e r of species with different diagnostic and prognostic significance. At this writing, 38 species of mycobacteria are recognized, and of these, 14 have been implicated as agents of h u m a n lung disease. Should a clinical laboratory be expected to identify all of these organisms? A clinical isolate is identified to help answer one or more of the following questions: Is this organism likely to be the cause of the patient's disease, or is it merely a contaminant? If it is the etiologic agent, how is the disease best managed clinically? W h a t are the public health implications of this organism? In most cases, the routine public health implications are defined once an acid fast isolate is identified as M. tuber-
Acceptable Le~wl of Identification 3t. tuberculosis 3I. bovis complex 3t. kansasii 31. avium/ intracellulare complex M. scrofidaceum MAIS complex
31. xenopi AL gordonae 3L gastri M. terrae complex "Other slow growers" AL fortuitum complex "Other rapid growers"
Species Included ~L M. M. 3L
tuberculosis bovis, M. africanum kansasii avium, 5L intracellulare
3L scrofulaceum Strains intermediate between AL avium and ~L scrofulaceum, as well as ~L simiae and AL asiaticum M. xenopi 3L gordonae AL gastri M. terrae. AL nonchromogenicum, and M. triviale 3L szulgai, M. malmoense 3L fortuitum, 3L chelonei At least 10 species
culosis or M. bovis, rather than some other Mycobacterium. The precise identification to species, subspecies, and serotype for epidemiologic purposes is best left to the highly specialized reference laboratory. To establish the probable clinical significance of the isolate ,and to guide the physician in managing the disease, it is usually sufficient to place mycobacteria, other than M. tuberculosis, into one of several complexes. A guide to the acceptable level of identification of organisms likely to be isolated from pulmonary secretions follows in Table 1. Any laboratory that cultures specimens for mycobacteria should be able to recognize M. tuberculosis and to distinguish it from other
Editors:
Human Pathogen? Yes Yes Usually Often Sometimes Sometimes
Sometimes No No No Sometimes Sometimes No
mycobacteria. Depending upon the volume of mycobacteriology done in a given laboratory and the available expertise, mycobacteria other than M. tuberculosis may be identified on the premises; otherwise, the culture must be sent to a referral laboratory that is capable of identifying it to the acceptable species or complex level as previously cited. Only under unusual circumstances will it be necessary to further refer a strain to one of the few laboratories capable of identifying all cultures to a species or subspecies level. Reference American Thoracic Society. 1977. Referral without guilt, or how far should a good lab go? (Available from local branches of the American Lung Association.)
Donna J. Blazevic, L. R. McCarthy, and Josephine A. Morello
Subscription Rates in U.S. and Canada: one year S42.50; two years $80.00; three years $ 110.00. All other countries: one year $57,,50; two years S 109.50; three years $153.25. Single copies are $2.00 in U.S. and Canada, $2.65 all other countries. Single issues are available in quantity (prices available upon request). All subscriptions are payable in advance. Foreign subscriptions are sent guaranteed air mail. First class postage paid in U.S. and Canada. Address correspondence iegarding subscription to: Clinical Aficrobiology Newsletter. G. K. Hall & Co., 70 Lincoln St., Boston, Massachusetts 0211 i. Please include zip code in subscription address. The Clinical Microbiology Newsletter is published twice monthly. All rights, including that of translation into other languages, reserved. Photomechanical reproduction (photocopy, microcopy) of this newsletter or parts thereof without special permission of the publisher is prohibited.