Related Experiment Video
Updated: Aug 12, 2026
Sequencing of Bacterial Microflora in Peripheral Blood: our Experience with HIV-infected Patients
Published on: June 11, 2011
Analysis of plasmids in Mycobacterium avium-intracellulare isolates from persons with acquired immunodeficiency
Abstract:
Twenty-six strains of the Mycobacterium avium complex isolated from persons with AIDS were examined for plasmid content. The strains were of serotypes 4, 8, 4/6, and 4/8. Plasmid content was determined by agarose gel electrophoresis. All 26 strains carried small plasmids (9 to 15 Mdal), with 11 strains carrying 1 small plasmid and 15 carrying 2. Ten strains also carried large plasmids (greater than 100 Mdal), and 1 strain carried a 60 Mdal plasmid. We have reported molecular cloning of plasmid pLR7, a small plasmid derived from a serotype 4 strain. Cloned segments of pLR7 were used as hybridization probes to detect homologous plasmids in the AIDS-associated strains. Each of the 26 strains carried a plasmid closely related to pLR7. Considerable heterogeneity of size and restriction sites was observed. The finding of plasmids in all strains raises the possibility that they may play a role in virulence. The plasmids will serve as a useful marker for epidemiology and might be useful as probes for detecting M. avium-intracellulare in clinical material.
Insights
All Mycobacterium avium complex strains from AIDS patients contained plasmids, suggesting a role in virulence. These plasmids can be used for epidemiology and clinical detection of M. avium-intracellulare.
Area of Science:
- Microbiology
- Molecular Biology
- Infectious Diseases
Background:
- Mycobacterium avium complex (MAC) is an opportunistic pathogen.
- MAC infections are particularly common and severe in individuals with Acquired Immunodeficiency Syndrome (AIDS).
- The role of plasmids in MAC virulence and pathogenesis is not fully understood.
Purpose of the Study:
- To investigate the plasmid content of MAC strains isolated from AIDS patients.
- To determine if specific plasmids are associated with these clinical isolates.
- To explore the potential use of these plasmids as diagnostic or epidemiological markers.
Main Methods:
- Plasmid DNA was extracted from 26 MAC strains (serotypes 4, 8, 4/6, 4/8) isolated from AIDS patients.
- Agarose gel electrophoresis was used to analyze plasmid size and number.
- Molecular cloning of a representative plasmid (pLR7) was performed.
- Cloned plasmid segments were used as hybridization probes to screen other isolates.
Main Results:
- All 26 MAC strains harbored small plasmids (9-15 Mdal), with most carrying one or two.
- Ten strains also contained large plasmids (>100 Mdal), and one had a 60 Mdal plasmid.
- All strains possessed plasmids homologous to the cloned pLR7, indicating a conserved plasmid element.
- Significant heterogeneity in plasmid size and restriction sites was observed among strains.
Conclusions:
- The universal presence of plasmids in MAC strains from AIDS patients suggests their potential involvement in virulence.
- These plasmids represent valuable genetic markers for epidemiological tracking of MAC infections.
- MAC plasmids could potentially be developed into probes for the clinical detection of M. avium-intracellulare.
