Viability testing of material derived from Mycobacterium tuberculosisprior to removal from a Containment Level-III Laboratory as part of a Laboratory Risk Assessment Program

Table 1 Results of positive Bactec 12B vials (n = 21).

Description of material	Growth on TSA + 5% SBA @ 48 hrs	Growth on Middlebrook 7H11	Kinyoun Stain direct from positive 12B	Probe	Conclusion
RFLP lysate – before CTAB addition (2 vials)	-	+, MTB morphology	AFB+ (4+), serpentine cording	ND	Viable MTB ¹
RFLP lysate from frozen storage #1	-	+, KS of growth AFB -	4 AFB/slide, morph not consistent with TB	MTB-	contaminant present – ubiquitous mycobacteria
RFLP lysate from frozen storage #2	-	+, KS of growth AFB -	15 AFB/slide, morph not consistent with TB	MTB-	contamination present – ubiquitous mycobacteria
RFLP lysate from frozen storage #3 & #4	-	+, KS of growth AFB -	No AFB		contamination present
Boiled lysate	-	+, Smooth colonies not consistent with MTB	AFB+ 5–10/field, clumping, no obvious serpentine cording	MTB-	ubiquitous mycobacteria
Smear, 1 h at 95°C & Smear, 2 h at 95°C²	-	+, MTB morphology	AFB+ (4+), serpentine cording	MTB+	Viable MTB
Protein extracts (2)	-	+, MTB morphology	AFB+ (4+), serpentine cording	MTB+	Viable MTB

¹ Accuprobe was not performed on these isolates, as MTB was expected due to morphology observed in addition to data from prior studies [7].
² All 12Bs from smears (n = 12) were positive, only 2 were chosen as representative for further testing Definitions: KS = Kinyoun stain, AFB = acid-fast bacilli, MTB = M. tuberculosis

ISSN: 1471-2334