Year :
2020
| Month :
March
| Volume :
14
| Issue :
3
| Page :
DC15 - DC19
Full Version
Study of Contaminants Growing on Lowenstein Jensen Media during Mycobacterium tuberculosis Culture from a Respiratory Speciality Hospital in Northern India
Published: March 1, 2020 | DOI: https://doi.org/10.7860/JCDR/2020/43525.13586
Amit Aggarwal, Ritu Singhal, Manpreet Bhalla, Vithal Prasad Myneedu
1. Senior Resident, Department of Medical Microbiology, National Institute of Tuberculosis and Respiratory Diseases, Delhi, India.
2. Assistant Professor, Department of Medical Microbiology, National Institute of Tuberculosis and Respiratory Diseases, Delhi, India.
3. Assistant Professor, Department of Medical Microbiology, National Institute of Tuberculosis and Respiratory Diseases, Delhi, India.
4. Professor and Head, Department of Medical Microbiology, National Institute of Tuberculosis and Respiratory Diseases, Delhi, India.
Correspondence Address :
Dr. Amit Aggarwal,
AA-292, Shalimar Bagh, Delhi-110088, India.
E-mail: amit.aggarwal.microbiology@gmail.com
Abstract
Introduction: Lowenstein Jensen (LJ) culture contamination is one of the most frequent problems encountered during Mycobacterium tuberculosis (M. tuberculosis) culture. Contaminated cultures are repeated at an additional cost and thus hinder diagnosis. This problem is of more significant concern in Extrapulmonary (EP) samples which have very fewer bacilli loads. Unfortunately, our current contaminant knowledge from past studies is minimal, which is entirely based on pulmonary samples, and not on EP samples. Development of newer culture methods will remain incomplete unless we have a good knowledge about contaminant profiles from both types of samples.
Aim: To isolate and identify bacterial and fungal contaminants growing on LJ media during M. tuberculosis complex culture in both pulmonary and EP samples.
Materials and Methods: LJ media pairs (5074) were inoculated, of which 2030 were inoculated with pulmonary samples and 3044 with EP samples. Mycobacterial, non-Mycobacterial and fungal growth were differentiated based on characteristics like colony morphology (on Chocolate agar, blood agar, Mackonkey Agar and Sabouraud’s Dextrose Agar), staining (Gram stain and Ziehl Neelsen) and biochemical reactions (Indole, Urea, Citrate and Triple Sugar Iron). Statistical analysis was done using SPSS version 20 (IBM®, New York, NY, USA) and Chi-square test was performed.
Results: Overall Contamination Rate (CR) was 2.2%. Individually, CR was 2.9% (60/2030) in pulmonary samples and 1.7% (52/3044) in EP samples (p<0.05). Of the total 303 organisms isolated in the study, 87.8% (266/303) were of bacterial origin and remaining 12.2% (37/303) were fungal. Bacteria isolated belonged to 12 different genera amongst which aerobic spore bearers (Bacillus spp) were the most common. All the 37 fungal isolates were moulds, of which 22 were Aspergillus spp (A. flavus, A. fumigatus and A. niger). Bacterial contaminants were more in pulmonary samples, whereas fungal in EP samples (p<0.05). All the contaminants were breakthrough as none grew as mixture along with acid-fast organisms.
Conclusion: Breakthrough nature of contaminants indicates that they probably act by completely inhibiting the growth of any acid-fast bacilli present in the sample. This observation becomes quite relevant in EP samples wherein M. tuberculosis bacilli load is already very less. This M. tuberculosis growth masking can thus decrease the overall sensitivity of LJ culture.
Keywords
Bacteria, Culture media, Extrapulmonary samples, Pulmonary samples, Sputum
DOI: 10.7860/JCDR/2020/43525.13586
Date of Submission: Dec 28, 2019
Date of Peer Review: Jan 21, 2020
Date of Acceptance: Feb 25, 2020
Date of Publishing: Mar 01, 2020
AUTHOR DECLARATION:
• Financial or Other Competing Interests: None
• Was Ethics Committee Approval obtained for this study? Yes
• Was informed consent obtained from the subjects involved in the study? No
• For any images presented appropriate consent has been obtained from the subjects. NA
PLAGIARISM CHECKING METHODS:
• Plagiarism X-checker: Dec 31, 2019
• Manual Googling: Feb 24, 2020
• iThenticate Software: Feb 26, 2020 (3%)
ETYMOLOGY: Author Origin
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