Related Experiment Video
Updated: Mar 23, 2026
Production of Germ-Free Fast-Growing Broilers from a Commercial Line for Microbiota Studies
Published on: June 18, 2020
DIFFERENCES IN CULTURAL YIELD OF MYCOBACTERIUM TUBERCULOSIS ON MEDIA PREPARED USING COMMERCIAL AND HOUSEHOLD EGGS
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.
Insights
Using antibiotic-free eggs for Mycobacterial culture media significantly improves tuberculosis (TB) diagnosis accuracy, especially for smear-negative samples. This finding is crucial for diagnosing TB in vulnerable populations.
Area of Science:
- Microbiology
- Medical Diagnostics
- Infectious Diseases
Background:
- Mycobacterial culture is the gold standard for tuberculosis (TB) diagnosis.
- Commercial eggs used in culture media contain antibiotics, potentially causing false negatives.
- Antibiotic contamination in culture media can hinder accurate TB detection.
Purpose of the Study:
- To compare Mycobacterial growth on culture media prepared from commercial eggs versus antibiotic-free household eggs.
- To evaluate the impact of antibiotic-containing commercial eggs on TB diagnostic sensitivity.
Main Methods:
- Sputum samples with varying acid-fast bacilli (AFB) loads were inoculated onto Ogawa medium prepared from both commercial and household eggs.
- Cultures were incubated for 60 days with regular inspection for colony appearance.
- Statistical analysis, including F test and unpaired Student's t test, was performed.
Main Results:
- One microscopically negative sample grew on household egg media but not on commercial egg media.
- Significant differences in time to culture positivity were observed for samples with 1+, 2+, and 3+ AFB loads (p < 0.05).
- Commercial eggs, due to antibiotic content, led to false-negative results in TB cultures.
Conclusions:
- Antibiotics in commercial eggs can cause false negativity in Mycobacterial cultures, particularly for smear-negative TB cases.
- This is a significant concern for diagnosing TB in HIV patients with high smear negativity rates.
- Development of antibiotic-free egg media or alternative diagnostic methods is essential for accurate TB diagnosis.
