Comparative evaluation of the MB/BacT and BACTEC 460 TB systems for the detection of mycobacteria from clinical specimens: clinical relevance of higher recovery rates from broth-based detection systems.
New broth-based detection systems have higher recovery rates of mycobacteria from clinical specimens than traditional cultures on solid media. The clinical significance of this higher sensitivity rate is largely unknown. We prospectively evaluated the performances of two liquid media detection systems (the MB/BacT system and the BACTEC 460 TB system) and an egg-based Lowenstein-Gruft solid medium (LG) on the recovery rates of mycobacteria from 849 clinical specimens. Mycobacteria (other then M. gordonae) were detected in 51 (6.0%) specimens. In 12/51 (23%) specimens, mycobacteria (five mycobacterium tuberculosis (MtB) and seven non-M tuberculosis complex (MOTT) were recovered only from the broth-based systems. Review of the patients' clinical charts revealed that failure of LG to recover Mtb were due to nonmycobacterial overgrowth and antibiotic treatment. The recovered MOTT were all clinically nonsignificant. Higher sensitivity of broth-based mycobacteria detection systems is largely due to their capability to recover mycobacteria from treated tuberculous patients or from partially decontaminated specimens. The high recovery rates of nonclinically significant MOTT could potentially increase inappropriate use of antibiotics.
Laverdiere
M
M
Department of Microbiology, Infectious-Diseases Hôpital Maisonneuve-Rosemont, University of Montréal, Quebec, Canada. laverdim@ere.umontreal.ca
Poirier
L
L
Weiss
K
K
Béliveau
C
C
Bédard
L
L
Desnoyers
D
D
D015373:Bacterial Typing Techniques; D003470:Culture Media; D005069:Evaluation Studies as Topic; D006801:Humans; D009164:Mycobacterium Infections / Q000175:diagnosis; D009169:Mycobacterium tuberculosis / Q000145:classification* / Q000302:isolation & purification; D009170:Nontuberculous Mycobacteria / Q000145:classification* / Q000302:isolation & purification; D011336:Probability; D011446:Prospective Studies; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity; D013048:Specimen Handling / Q000379:methods
D003470:Culture Media; D011933:Reagent Kits, Diagnostic