| |
TB Notes Newsletter
Return to TB Notes 2, 2006 Main Menu
This is an archived document. The links
and content are no longer being updated.
No. 2, 2006
HIGHLIGHTS FROM STATE AND LOCAL PROGRAMS
Molecular Genotyping of Mycobacterium tuberculosis
in Connecticut
After more than a decade of use, molecular genotyping of Mycobacterium
tuberculosis isolates is now a standard public health tool.
Genotyping has been used in a variety of settings, including defining
strains prevalent in the population, detecting outbreaks in institutions
and the community, evaluating the completeness of contact investigations,
and determining laboratory contamination.1-5
In 2005, CDC launched the Genotyping TB Program, making laboratory
capacity available to state health departments interested in genotyping
M. tuberculosis isolates. In New England, the six state health laboratories are now routinely forwarding
all culture-confirmed isolates from patients with pulmonary TB to
one of the program’s reference laboratories for genotyping. To accelerate
the decline of TB in New England, the state
health departments coordinate cross-jurisdictional investigations
to prevent the transmission of TB across state lines. In this report,
we describe one recent outbreak of TB in Fairfield
County, Connecticut. This outbreak would not
have been detected without the use of molecular genotyping.
Connecticut TB Outbreak
Since 2005, universal genotyping of pulmonary TB isolates has
detected five clusters in Connecticut. One cluster, with cases diagnosed
during February 2004–May 2005, consisted of four Hispanic males
from one city in Fairfield
County (Table 1). Risk factors included
HIV infection (2), unemployment (2), and incarceration (2).
Table 1: Fairfield County, Connecticut TB Cluster, February
2004-May 2005
| Age Groups (YTS) |
Occupation |
Country of Birth |
Date of entry into the U.S. |
HIV Status |
TB Risk Factors |
| 15-24 |
Restaurant |
Mexico |
Unknown |
Negative |
Foreign
born |
| 25-44 |
Painter |
Mexico |
Post-2000 |
Negative |
Foreign
born |
| 24-44 |
Unemployed |
Mexico |
Pre-2000 |
Positive |
Foreign
born: History incarceration, Excess alcohol |
| 25-44 |
Unemployed |
U.S. |
N/A |
Positive |
History
incarceration |
Comment
In Connecticut, molecular genotyping is radically transforming TB control
practices. Two methods based on polymerase chain reaction (PCR)
are initially used. The first, spoligotyping, is a method for simultaneous
detection and typing of M. tuberculosis strains. The second,
mycobacterial interspersed repetitive unit–variable number tandem
repeat (MIRU-VNTR) analysis, is a typing method that determines
the number of repeated mycobacterial interspersed units at 12 independent
loci.6 These methods provide faster turnaround times
and produce digital results that make comparisons easier. A non-PCR
technique, restriction fragment length polymorphism (RFLP), continues
to be used to further define suspected outbreak strains. The population-based
application of genotyping has revealed unsuspected transmission
patterns that might not have been identified using conventional
epidemiological techniques. Originally seven persons were identified
in the Fairfield County
cluster. Genotyping, using RFLP, showed that three strains were
not identical to the dominant strain infecting the other four patients.
In response to this newly recognized cluster of four related TB
cases, the DPH attempted a more intensive epidemiologic investigation
with limited results, since two of the individuals had returned
to Mexico.
At this time, genotyping results are pending from another case potentially
involved in this outbreak.
As more knowledge is gained about the use of molecular techniques
and earlier detection of clusters, further investigations will continue
to reveal previously unrecognized epidemiologic links between cases
and define new settings where transmission occurred.7
We believe that the addition of molecular genotyping as a public
health tool will augment TB control and accelerate the reduction
of cases in Connecticut and the United States.
—Reported by T Condren, MPH, M Williams,
RN,
TB Control Program
Connecticut Department of Public Health
G Budnick, MPS,
Connecticut Public Health Laboratory
J Hadler, MD, MPH, State Epidemiologist
M Lobato, MD, Division of TB Control, CDC
References
- Small PM, Hopewell
PC, Singh SP, et al. The epidemiology of tuberculosis in San
Francisco. A population-based study using conventional and molecular
methods. N Engl J Med 1994; 330: 1703-9.
- Jereb JA, Burwen DR, Dooley SW, et al. Nosocomial outbreak of
tuberculosis in a renal transplant unit: application of a new
technique for restriction fragment length polymorphism analysis
of Mycobacterium tuberculosis isolates. J Infect Dis
1993 168:1219-24.
- Daley CL, Small PM, Schecter GF, Schoolnik GK, McAdam RA, Jacobs
WR Jr, Hopewell PC. An outbreak of tuberculosis with accelerated
progression among persons infected with the human immunodeficiency
virus. An analysis using restriction-fragment-length polymorphisms.
N Engl J Med 1992;326:231-5.
- Cronin WA, Golub JE, Lathan MJ, et al. Molecular epidemiology
of tuberculosis in a low- to moderate-incidence state: are contact
investigations enough? Emerg Infect Dis 2002;8:1271-9.
- CDC. Misdiagnoses of tuberculosis resulting from laboratory
cross-contamination of Mycobacterium tuberculosis cultures--New Jersey, 1998. MMWR. 2000;49:413-6.
- Kwara A, Schiro R, Cowan, LS , et al. Evaluation of the epidemiologic
utility of secondary typing methods for differentiation of Mycobacterium
tuberculosis isolates. J Clin Micro, June 2003; 41:
2683-2685.
- Miller AC, Sharnprapai S, Suruki R, et al. Impact of genotyping
of Mycobacterium tuberculosis on public health practice
in Massachusetts. Emerg Infect Dis 2002;8:1285-9.
Last Reviewed: 05/18/2008
Content Source: Division of Tuberculosis Elimination
National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention
|
