1. Biosafety Implications of GeneXpert MTB/RIF assay: Experience of the National Tuberculosis Reference Laboratory , Lagos
Nwokoye N, Onubogu CC, Nwadike PO, Abiodun AT, Tochukwu NE, Ejezie CO, Onwuamah CK, Gidado M, Elom E, Idigbe OE
Presenter
Nwokoye Nkiru

2. Introduction
Tuberculosis (TB) is an airborne infection that is transmitted primarily via aerosol
Occupational transmission of TB has been demonstrated among health care workers (Kehinde et al., 2011)
Test methods that involve aerosol-generating procedures expose testing personnel to high risk of TB infection.
The Genexpert MTB/RIF (Xpert) assay has been described as a point-of-care test that can be performed outside the biosafety cabinet.
Sample reagent (SR) contains compounds that effectively kill the TB bacilli (Banada et al. 2012)

3. Introduction… Worrisome issues
What if the sample reagent fails to Kill theTB bacilli?
What if the substandard sputum cup leaks and releases the bacilli?
What if the released bacilli are not the susceptibleTB but MDR or even XDR-TB?

4. Objective
To assessing the killing effect of the sample reagent on tubercle bacilli.
Methodology
The study investigated 604 patients that were referred to the National Tuberculosis Reference Laboratory, Nigerian Institute of Medical Research (NIMR), Lagos, between January and December 2012.
Categories of patients enrolled included presumptive drug resistant-TB (DR-TB) cases and HIV positive patients showing symptoms of TB.
GeneXpert assay and TB culture were done as per standard protocol

5. Findings and implications
Result
Implication
Table 1: MTB and Rifampicin resistance detection by Xpert assay
Xpert characteristics Frequency (%)
MTB detected 164(27.2)
MTB not detected 440(72.9)
Rifampicin resistance detection
Resistance detected 68(41.5)
Resistance not detected 95(57.9)
Indeterminate 1(0.6)
High prevalence of Rifampicin resistant TB
High MDR-TB prevalence among the study population

6. Table 2: MTB detection by Xpert based on HIV-status
Findings and implications...
Table 2: MTB detection by Xpert based on HIV-status
MTB detection HIV status Negative Positive Total
Negative 174(39.5%) 82(50.0%) (42.4%)
Positive 240(54.6%) 54(32.9%) (48.7%)
Unknown 26(5.9%) 28(17.0%) (8.9%) Total (100.0%) (100.0%) (100.0%)
Implication
Increased detection of MTB among the HIV-positive patient
smear microscopy has reduced sensitivity in HIV –positive patient (onubogu et al., 2012; Oludiran et al., 2008)
Xpert is a Veritable tool for TB diagnosis in HIV co-infected patients

7. Findings and implications...
Table 3: Growth inhibition by Xpert sample reagent (SR)
Growth on LJ without SR(control)
Growth on LJ with SR Negative Positive Total
Negative 123(100.%) 65(82.3%) 188(93.1%)
Positive 0(0.0%) 14(17.7%) 14(6.9%)
Total (60.9%) 79(39.1%) 202(100.0%)
p =
Implications
Xpert SR was unable to kill all the TB bacilli after 15 mins of incubation
Processing involves aerosol generating procedures, Sputum cups are not leak proof, N95 respirator is not worn
Following national policy, laboratory personnel performing Xpert assay has 17.7% chances of being exposed to live TB bacilli

8. Recommendations
National policy on diagnosis of DR-TB should be reviewed to accommodate
Use of leak proof, screw capped sputum container for processing of xpert specimens
Processing of xpert samples in a well ventilated laboratory
Use of N95 respirator when handling known or suspected DR-TB specimens
(screw cap sputum cup)
N95 respirator

9. Conclusion
Xpert is a veritable tool for TB diagnosis particularly in HIV co- infected patients
Following national policy, laboratory personnel performing Xpert assay has 17.7% chances of being exposed to live TB bacilli.
National policy on DR-TB diagnosis should be reviewed to avert upsurge of laboratory acquired DR-TB
References
Kehinde AO, Baba A, Bakare RA, Ige OM, Gbadeyanka CF, Adebiyi OE (2011). Pulmonary tuberculosis among health care workers at two designated DOTS Centers in urban city of Ibadan, Nigeria. Indian J Med Res 133:
Onubogu CC, Nwokoye NN, Kunle-Ope CN, Raheem TY, Igbasi UT, Tochukwu N, et al. (2012). Sensitivity of direct smear microscopy for the diagnosis of TB in high HIV prevalent population . Scientific Research and Essay 7:
Oludiran KA, Eziuka OR, Mayowa IO, Ajani BR, kikelomo O (2008). Bacteriology of childhood tuberculosis in Ibadan, Nigeria: A five-year review. Trop. Med. Health 36:
Banada P, Sivasubramani SK, Blakemore R, Boehme C, Perkin MD, Fennelly K, Alland D(2010). Containment of bioaerosol infection risk by the Xpert MTB/RIF assay and its applicability to point-of-care settings, J. Clin. Microbiol. 48:3551–3557.

10. References
Kehinde AO, Baba A, Bakare RA, Ige OM, Gbadeyanka CF, Adebiyi OE (2011). Pulmonary tuberculosis among health care workers at two designated DOTS Centers in urban city of Ibadan, Nigeria. Indian J Med Res 133:
Onubogu CC, Nwokoye NN, Kunle-Ope CN, Raheem TY, Igbasi UT, Tochukwu N, et al. (2012). Sensitivity of direct smear microscopy for the diagnosis of TB in high HIV prevalent population . Scientific Research and Essay 7:
Oludiran KA, Eziuka OR, Mayowa IO, Ajani BR, kikelomo O (2008). Bacteriology of childhood tuberculosis in Ibadan, Nigeria: A five-year review. Trop. Med. Health 36:
Banada P, Sivasubramani SK, Blakemore R, Boehme C, Perkin MD, Fennelly K, Alland D(2010). Containment of bioaerosol infection risk by the Xpert MTB/RIF assay and its applicability to point-of-care settings, J. Clin. Microbiol. 48:3551– 3557.

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