The BACTEC system (Becton Dickinson, Sparks, Md.) was compared with culture on LÃ´wenstein-Jensen egg medium for the detection of Mycobacterium ...
Vol. 29, No. 11
JOURNAL OF CLINICAL MICROBIOLOGY, Nov. 1991, p. 2673-2674 0095-1137/91/112673-02$02.00/0 Copyright © 1991, American Society for Microbiology
Easily Missed Pathogen
SVEN E. HOFFNER,l* BIRGITTA HENRIQUES,' BJORN PETRINI,2 AND GUNILLA KALLENIUS'
National Bacteriological Laboratory, S-105 21 Stockholm,' and Central Microbiolgical Laboratory, Stockholm County Council, S-107 26 Stockholm,2 Sweden Received 26 March 1991/Accepted 31 July 1991
The BACTEC system (Becton Dickinson, Sparks, Md.) was compared with culture on Lôwenstein-Jensen medium for the detection of Mycobacterium malmoense in lymph node samples from children with lymphadenitis. It was found to be significantly more sensitive and rapid. The use of the BACTEC system is thus recommended as a complement to culture on solid media for the primary isolation of atypical mycobacteria, such as M. malmoense.
in 8 samples (47%) from 6 of the 11 children by culturing the samples on LJ medium. If the solid culture had been carried out at 37°C only, the sensitivity would have been even lower; only 5 of 17 (29%) positive cultures would have been detected (Table 1). The time for detection was significantly shorter for the broth cultures; 11 of 16 positive cultures were detected within 2 weeks with the BACTEC system, while no growth was seen within the first 4 weeks of incubation when culturing on solid medium was used (Table 1). Results of this study show that broth culture by the BACTEC system is significantly more sensitive and rapid for the detection of M. malmoense in tissue samples than is solid culture on egg medium. Earlier, we obtained similarly good results by the use of liquid culture and BACTEC radiometry for the detection of the slow-growing mycobacteria belonging to the M. avium complex in clinical tissue samples (3, 4); other investigators have also obtained good results, for example, Takahashi and Foster (10), who compared the BACTEC system with both egg- and agar-based solid media. The lack of sensitivity of conventional solid culture media seen in this and earlier studies prompts us to strongly recommend that a broth medium be included in the primary
Mycobacterium malmoense was first described in 1977 by Schroder and Juhlin (9). This atypical mycobacterium is isolated in increasing numbers from clinical samples, and today, next to Mycobacterium tuberculosis and the Mycobacterium avium complex, it is the most common cause of mycobacterial infection in Sweden. The standard methods for laboratory culture of mycobacteria were originally developed for the isolation of M. tuberculosis and, thus, are not inherently optimal for all types of clinically significant mycobacteria (3). To ensure a sensitive primary isolation of fastidious pathogens such as M. malmoense, it is crucial to carefully choose culture media and conditions. The recovery of atypical mycobacteria after the use of various decontamination and growth conditions was examined by Brooks and coworkers (1). Improved detection of M. malmoense with a pyruvate-containing Lôwenstein-Jensen (LJ) egg medium with a reduced pH has been reported by Katila and colleagues (6). The importance of a long incubation time for the recovery of slow-growing mycobacteria, and especially for the recovery of M. malmoense, has been stressed by Ispahani and Baker (5). Grange and Yates (2) indicated that the incubation temperature is an important factor. They recommend the use of a reduced temperature (30 to 33°C) for the primary isolation of mycobacteria from selected samples (2). Here, we show that the use of a liquid medium and radiometric growth detection has the potential to significantly improve the laboratory detection of M. malmoense in clinical samples. During recent years, we have used Middlebrook 7H12 broth for culturing lymph node and other tissue biopsy specimens (8) and have registered mycobacterial growth in a BACTEC 460 instrument (Becton Dickinson, Sparks, Md.); this is done in addition to culturing on solid LJ and LJpyruvate media (3). The broth cultures were incubated at 37°C; the solid cultures were incubated at both 30 and 37°C. All cultures were monitored for growth once a week for 7 to 8 weeks. In the 6-year period from 1985 to 1990, we isolated M. malmoense from a total of 17 lymph node samples collected from 11 children (ages, 2 to 4 years) with mycobacterial lymphadenitis. The isolates were identified by standard laboratory testing techniques (7). Of the 17 positive cultures representing samples from all children, 16 (94%) were detected with the BACTEC system, while growth was detected *
TABLE 1. Isolation of M. malmoense from cervical lymph nodes Patient
i 2 3
a a a b a a b
4 5 6 7
+ (42)a -
+ (12) + (19) + (12) + (10)
b 9 10
+ (12) + (14)
+ (8) + (28) + (15) + (42) + (10) + (8)
Isolation (time [daysJ) by: BACTEC BATCLJ culture radiometry
Growth only at 30°C.
+ (18) + (8) + (8)
+ (42)a + (42) + (49)a
isolation of mycobacteria from tissues, so that infections caused by atypical mycobacteria will not be missed.
REFERENCES Brooks, R. W., K. L. George, B. C. Parker, J. O. Falkinham III, and H. Gruft. 1984. Recovery and survival of nontuberculous mycobacteria under various growth and decontamination conditions. Can. J. Microbiol. 30:1112-1117. Grange, J. M., and M. D. Yates. 1988. Mycobacterial culture: what temperature? Lancet i:534-535. Hoffner, S. E. 1988. Improved detection of Mycobacterium avium complex with the Bactec radiometric system. Diagn. Microbiol. Infect. Dis. 10:1-6. Hoffner, S. E., K. Hahn, A. Pedersen, and K. Sandstedt. 1989. Rapid radiometric detection of mycobacteria in tissue samples from pigs. J. Apple. Bacteriol. 66:65-67.
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5. Ispahani, P., and M. Baker. 1988. Mycobacterial culture: how long? Lancet i:305. 6. Katila, M.-L., J. Mattilla, and E. Brander. 1989. Enhancement of growth of Mycobacterium malmoense by acidic pH and pyruvate. Eur. J. Clin. Microbiol. Infect. Dis. 8:998-1000. 7. Kent, P. T., and G. P. Kubica. 1985. Public health mycobacteriology. A guide for the level III laboratory. Centers for Disease Control, Atlanta. 8. Middlebrook, G., Z. Reggiardo, and W. D. Tigertt. 1977. Automatable radiometric detection of growth of Mycobacterium tuberculosis in selective media. Am. Rev. Respir. Dis. 15:10661069. 9. Schroder, K. H., and I. Juhlin. 1977. Mycobacterium malmoense sp. nov. Int. J. Syst. Bacteriol. 27:241-246. 10. Takahashi, H., and V. Foster. 1983. Detection and recovery of mycobacteria by a radiometric procedure. J. Clin. Microbiol. 17:380-381.