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Mouse foot pad growth of M. leprae in relation to bacteriological index
Abstract:
A retrospective analysis was made of the mouse foot-pad growth of M. leprae from 35 cases of lepromatous leprosy with B.I. ranging from 1.33 to 4.0 (Dharmendra scale). Of these 35 cases, 6 were found to be harbouring dapsone resistant bacilli and 18 cases sensitive bacilli. In 11 of them there was no growth in the control group of animals. The analysis showed that there was no difference in the mean B.I. between those showing no growth and those showing growth in the 1st, 2nd or 3rd harvest. A minimum B.I. around 1.5 is considered adequate for positive foot-pad takes. Another interesting observation made in the study was that the growth rate in the control group foot-pads was consistently higher in mice receiving dapsone resistant bacilli as compared to those inoculated with bacilli, sensitive to the drug.
Insights
This study found no significant difference in leprosy bacilli growth based on dapsone resistance. However, dapsone-resistant M. leprae showed higher growth rates in mouse foot-pads compared to sensitive strains.
Area of Science:
- Microbiology
- Immunology
- Dermatology
Background:
- Leprosy remains a significant global health challenge, particularly lepromatous leprosy.
- Dapsone resistance in Mycobacterium leprae (M. leprae) complicates treatment outcomes.
- Mouse foot-pad models are crucial for assessing M. leprae viability and drug efficacy.
Purpose of the Study:
- To analyze M. leprae growth in mouse foot-pads from leprosy patients with varying dapsone sensitivity.
- To determine the minimum bacterial index (B.I.) required for successful M. leprae inoculation in mice.
- To compare the growth rates of dapsone-sensitive and dapsone-resistant M. leprae.
Main Methods:
- Retrospective analysis of M. leprae growth in mouse foot-pads from 35 lepromatous leprosy cases.
- Classification of M. leprae based on dapsone sensitivity (resistant or sensitive).
- Measurement of bacterial index (B.I.) and assessment of growth across multiple harvests.
Main Results:
- No significant difference in mean B.I. was observed between groups with or without M. leprae growth in the first three harvests.
- A minimum B.I. of approximately 1.5 was identified as adequate for positive foot-pad inoculation.
- Mice inoculated with dapsone-resistant M. leprae exhibited consistently higher growth rates in control foot-pads compared to those with sensitive bacilli.
Conclusions:
- The study suggests that M. leprae B.I. alone may not be a reliable indicator for differentiating dapsone sensitivity in mouse models.
- Dapsone-resistant M. leprae demonstrates enhanced growth potential in vivo, irrespective of initial inoculation B.I.
- These findings highlight the importance of monitoring drug resistance in M. leprae and its implications for disease progression.