All patients were U.S.-born and human immunodeficiency virus-seronegative, and had pulmonary TB. All six adults were female with a mean age of 28 years (range: 21–36 years). The three pediatric patients ranged in age from 10–19 months. Eight of nine patients completed treatment; one patient who had clinical, culture-negative disease disappeared shortly after starting treatment.
The source patient lived in multiple households before and after incarceration. The Figure shows the epidemiologic curve and source patient's living arrangements in chronological order. Before incarceration, the source patient lived with a friend (Patient 8), who was later diagnosed with smear- and culture-negative TB. During October–November 2005, the source patient lived in the same prison dormitory room as the index patient (Patient 1), who was the first patient to have TB disease diagnosed in January 2006.10
The source patient socialized frequently with a friend (Patient 7) before, during, and after incarceration. Upon release from prison, the source patient lived with another friend and her two children for two weeks; one child (Patient 4) later had TB diagnosed. The source patient then lived with two cousins and their five children for 14 weeks until her diagnosis. Both adult cousins (Patients 3 and 6) and two of the children (Patients 2 and 5) subsequently had TB diagnosed.
Five (63%) of eight secondary patients had isolates available for genotyping. Three patients did not have isolates: two adults had culture-negative TB, and one child did not have specimens collected. All five isolates had the same spoligotyping pattern as the source patient. Of the three secondary case isolates typed with RFLP, all had the same one-band pattern as the source patient's RFLP pattern from 1996 and 2006. However, the isolates in this outbreak had two distinct MIRU patterns. Based on the difference in the MIRU patterns, we assigned two cluster designations (Cluster A and Cluster B) (). The difference in these patterns, and therefore clusters, was a single-tandem repeat at locus 27. Because of the strong epidemiologic links between the source patient and all secondary patients, we requested genotyping for all five of the source patient's isolates. On subsequent testing, two of the source patient's isolates showed evidence of a mixed population of M. tuberculosis, with both three and four tandem repeats at MIRU locus 27, consistent with the two distinct clusters.
Genotype patterns of source patient and secondary patients and resulting cluster designations (n=6)
The investigation identified 22 people as household contacts; 12 (55%) were adults and 10 (45%) were children younger than 15 years of age (). Among household contacts, three (25%) adults and three (30%) children had TB diagnosed, and six (50%) adults and six (60%) children had latent TB infection diagnosed. When we expanded the investigation, we identified 69 additional contacts. Within the wider network, one (2%) adult contact had TB disease and 11 (16%) had latent TB infection. Of the 12 household contacts with latent TB infection, four (67%) adults and all six (100%) children completed nine months of isoniazid treatment. Of the other 11 contacts with latent TB infection, seven (64%) started and four (36%) completed treatment.
Results of a tuberculosis outbreak investigation for the source patient in Connecticut