[Utility of the direct culture examination (Ziehl-Neelsen) using the Bactec system for the presumptive identification of Mycobacterium tuberculosis complex, Mycobacterium avium complex, Mycobacterium xenopi, and Mycobacterium kansasii].
BACKGROUND
The usefulness of the microscopic examination of Bactec 12B and 13A growth medium as a method for the possible identification of M. tuberculosis complex, M. avium complex, M. xenopi, and M. kansasii was performed out to guide the selection of different genetic identification probes and, in the case of M. xenopi, the selection of the temperature of subcultures incubation.


METHODS
Upon detection of an index of growth greater than 100 in Bactec tubes, staining was performed by the Ziehl-Neelsen technique. On the basis of the morphology observed, the possible identification was performed by genetic probes. Subcultures were used for definitive identification.


RESULTS
Three hundred forty-four positive samples were studied by radiometric technique. A total of 190 strains were identified as M. tuberculosis, 88 strains as M. avium-intracellulare (MAI), 33 strains as M. xenopi, 14 strains as M. kansasii and 19 strains were identified as: M. gordonae (10), unpigmented rapid growth microbacteria (7), and M. simiae (2). Sensitivity, specificity, positive predictive value, and negative predictive value were 97.9%, 95.4%, 96.4%, and 97.3%, respectively for M. tuberculosis complex, 84.0%, 99.2%, 97.3% 94.7% for M. avium complex; 63.6%, 98.3%, 80.7%, 96.2% for M. xenopi; 35.7%, 98.1%, 45.5% 97.2% for M. kansasii.


CONCLUSIONS
The morphology of M. tuberculosis complex examined in the radiometric system in useful to differentiate this species from other microbacteria (MOTT), allowing the selection of specific probe used. Within the MOTT, M. avium complex also has morphological characteristics which are useful for its differentiation, the morphology usually described for the remaining species was frequently not observed.
Moreno
C
C
Servicio de Microbiología, Hospital de la Santa Creu i Sant Pau, Barcelona.
Garrigó
M
M
Sánchez
F
F
Coll
P
P
D001431:Bacteriological Techniques / Q000295:instrumentation; D003470:Culture Media / Q000494:pharmacology*; D005069:Evaluation Studies as Topic; D006801:Humans; D008751:Methylene Blue; D009165:Mycobacterium Infections, Nontuberculous / Q000175:diagnosis / Q000382:microbiology*; D015269:Mycobacterium avium Complex / Q000187:drug effects / Q000254:growth & development / Q000302:isolation & purification* / Q000648:ultrastructure; D015270:Mycobacterium avium-intracellulare Infection / Q000175:diagnosis / Q000382:microbiology*; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000254:growth & development / Q000302:isolation & purification* / Q000648:ultrastructure; D009170:Nontuberculous Mycobacteria / Q000187:drug effects / Q000254:growth & development / Q000302:isolation & purification* / Q000648:ultrastructure; D011237:Predictive Value of Tests; D011874:Radiometry; D012394:Rosaniline Dyes; D012680:Sensitivity and Specificity; D013045:Species Specificity; D014376:Tuberculosis / Q000175:diagnosis / Q000382:microbiology*
D003470:Culture Media; D012394:Rosaniline Dyes; C006898:carbol-fuchsin solution; D008751:Methylene Blue
Valor del examen directo (Ziehl-Neelsen) del cultivo en sistema Bactec para la identificación presuntiva de: Mycobacterium tuberculosis complex, Mycobacterium avium complex, Mycobacterium xenopi y Mycobacterium kansasii.