Mycobacterium tuberculosis transmission between cluster members with similar fingerprint patterns

Abstract

Molecular epidemiologic studies provide evidence of transmission of Mycobacterium tuberculosis within clusters of patients whose isolates share identical IS6110-DNA fingerprint patterns. However, M. tuberculosis transmission among patients whose isolates have similar but not identical DNA fingerprint patterns (i.e., differing by a single band) has not been well documented. We used DNA fingerprinting, combined with conventional epidemiology, to show unsuspected patterns of tuberculosis transmission associated with three public bars in the same city. Among clustered TB cases, DNA fingerprinting analysis of isolates with similar and identical fingerprints helped us discover epidemiologic links missed during routine tuberculosis contact investigations.

Figure 1

Restriction fragment length polymorphism patterns of Mycobacterium tuberculosis isolates from 11 patients residing in two geographically contiguous counties, Arkansas, 1992–1998. IS6110 patterns are shown on the left and polymorphic GC-rich sequence on the right. Lane M shows M. tuberculosis strain H37Rv DNA marker (left) and 1-kb DNA ladder (right). Lane 1, isolate from patient 11; Lane 2, patient 13; Lanes 3–6, patients 4, 1, 3, and 2; Lanes 7–9, patients 10, 9, and 8; Lane 10, patient whose isolate differed by three bands and was not included in the study; and Lane 11, patient 5.

Figure 2

Epidemologic links among tuberculosis patients, Arkansas, 1992–1998. The circles represent the three public bars associated with the cluster of patients. Patient (Pt.) numbers enclosed with boxes and oval circles show patient isolates with patterns A and B, respectively. Parentheses show year of diagnosis. Solid black lines show epidemiologic links found during contact investigations. Dashed black lines show additional epidemiologic links discovered after DNA fingerprinting was done on the isolates and after standardized interviews were conducted with the clustered patients. Absence of lines means that no epidemiologic links were discovered for patients.