• Muhammad Yahya Noori Dow University of Health Sciences http://orcid.org/0000-0002-3661-9222
  • Zaheer Ali National TB Control Program
  • Ghazala Khan University of Karachi
  • Shaheen Sharafat Dow University of Health Sciences
  • Muhammad Masroor Dow University of Health Sciences


Background: Mycobacterial culture is considered as the gold standard for TB diagnosis.  It is performed on egg-based media using commercially available eggs to grow Mycobacteria from clinical samples.  These eggs are known to contain high concentration of antibiotics, including fluoroquinolones, given to chicken to prevent early mortality.  This study was performed to compare Mycobacterial growth on media prepared from commercial and antibiotic free household eggs. Methods: Sputum samples from negative (No bacilli in 100 oil immersion field), scanty (1–9 AFB in 100 fields), 1+ (10–99 bacilli per field), 2+ (1–10 bacilli per field) and 3+ (>10 bacilli per field) were inoculated dually on Ogawa medium prepared from commercial and household eggs. Tubes were inspected every fourth day for the appearance of colonies till 60 days.  Data tabulations and statistical analysis (F test for variation and unpaired Student’s t test) were performed on Microsoft Excel®. Results: One microscopically negative sample showed growth on media prepared from household eggs, while all were negative on that prepared from commercial eggs.  There were significant differences in time to culture positivity for samples graded 1+ (p=0.02), 2+ (p=0.002) and 3+ (p=0.0003). Conclusion: Commercial eggs containing antibiotics can be a source of false negativity in cultures especially in microscopically negative samples. This can be of special concern in HIV patients who have high smear negativity. It is therefore important to either develop provision of antibiotic free eggs for media preparation or to develop and validate other laboratory investigations for smear negative TB patients.

Author Biographies

Muhammad Yahya Noori, Dow University of Health Sciences

Assistant Professor of PathologyDow International Medical CollegeFocal Person for Provincial Tuberculosis Reference Lab SindhDow University of Health Sciences

Zaheer Ali, National TB Control Program

MicrobiologistProvincial Reference Lab for TuberculosisNational TB Control Program

Ghazala Khan, University of Karachi

StudentFaculty of PharmacyUnivesity of Karachi

Shaheen Sharafat, Dow University of Health Sciences

Professor of PathologyDirector Dow Diagnostic and Research LaboratoryDow International Medical CollegeDow University of Health Sciences

Muhammad Masroor, Dow University of Health Sciences

Professor of MedicinePrincipal Dow International Medical CollegeDirector Ojha Institute of Chest DiseasesProvice ChancellorDow University of Health Sciences


Zumla A, George A, Sharma V, Herbert N. WHO's 2013 global report on tuberculosis: successes, threats, and opportunities. Lancet 2013;382(9907);1765–7.

Leung E, Minion J, Benedetti A, Pai M, Menzies D. Microcolony culture techniques for tuberculosis diagnosis: a systematic review. Int J Tuberc Lung Dis 2012;16(1):16–23.

Armand S, Vanhuls P, Delcroix G, Courcol R, Lemartre N. Comparison of the Xpert MTB/RIF test with an IS6110-TaqMan real-time PCR assay for direct detection of Mycobacterium tuberculosis in respiratory and nonrespiratory specimens. J Clin Microbiol 2013;49(5):1772–6.

Hepple P, Ford N, McNerney R. Microscopy compared to culture for the diagnosis of tuberculosis in induced sputum samples: a systematic review. Int J Tuberc Lung Dis 2012;16(5):579–88.

Van Deun A. What is the role of mycobacterial culture in diagnosis and case definition? In: Frieden T, editor. Toman's tuberculosis case detection, treatment, and monitoring; questions and answers. 2 ed. Geneva: World Health Organization; 2004. p.35–43.

Asad F. Antibiotic Residue in Poultry Product. [PhD Thesis]. Faisalabad: University of Agriculture; 2012 [cited 2015 Jan 15]. Available from: http://prr.hec.gov.pk/Thesis/1783S.pdf

Amjad H, Iqbal J, Naeem M. Estimation of selected residual antibiotics in muscle, kidney, liver, and egg of layer chicken. Proc Pak Acad Sci 2006;43(1):29–37.

van der Heijden YF, Maruri F, Blackman A, Mitchel E, Bian A, Shintani AK, et al. Fluoroquinolone susceptibility in Mycobacterium tuberculosis after pre-diagnosis exposure to older-versus newer-generation fluoroquinolones. Int J Antimicrob Agents 2013;42(3):232–7.

Microsoft. Microsoft Excel. 2010.

Behr MA, Warren SA, Salamon H, Hopewell PC, de Leon AP, Daley CL, et al. Transmission of Mycobacterium tuberculosis from patients smear-negative for acid-fast bacilli. Lancet 1999;353(9151):444–9.

Colebunders R, Bastian I. A review of the diagnosis and treatment of smear-negative pulmonary tuberculosis. Int J Tuberc Lung Dis 2000;4(2):97–107.