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U.S. Department of Health and Human Services

  

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TB Notes 4, 2004

No. 4, 2004

HIGHLIGHTS FROM STATE AND LOCAL PROGRAMS

TB Strain with Strong Persistence and with Highly Efficient and Rapid Transmission to HIV-Infected Patients, Louisiana, 2004

The Louisiana Office of Public Health TB Control Program detected a cluster of TB cases caused by the same organism, identified through restriction fragment length polymorphism (RFLP) fingerprinting. These cases were highly infectious, with multiple failures of directly observed therapy (DOT) for latent TB infection (LTBI) with isoniazid (INH, sometimes abbreviated as H), and with extremely virulent and rapidly transmissible organisms.

The source patient, Patient A, identified in November 1998, was diagnosed with sputum smear–positive TB and started on a standard adult treatment regimen of isoniazid, rifampin, pyrazinamide, and ethambutol (HRZE). Treatment compliance was adequate, recovery was satisfactory, sputum-smear conversion occurred within the first 2 months, and the patient was considered cured upon completion of 6 months of DOT. Six household contacts and five nonhousehold contacts of Patient A were evaluated, using Mantoux tuberculin testing, with infection rates of 100% (6/6) and 60% (3/5) respectively. In Louisiana, two different regimens for the treatment of LTBI are used. For children and HIV-infected persons, the recommended duration of LTBI treatment is 9 months. For all others, the recommended treatment duration is 6 months. All contacts with LTBI were treated with either the 6-month or the 9-month INH regimen, as appropriate.

In July 1999, Patient B, one of Patient A’s children and a member of the household, was diagnosed with sputum smear–positive TB, with the same organism. A standard adult treatment regimen (HRZE) was used. Again, treatment compliance was adequate, recovery was satisfactory, sputum-smear conversion occurred within the first 2 months, and the patient was considered cured upon completion of 6 months of DOT.

In November 1999, Patient A was rediagnosed with sputum smear–positive TB, once more with the same TB organism. It is not clear whether the relapse was due to reactivation of previous disease or reinfection from Patient B. Patient A was re-treated with PAS (A) and ciprofloxacin (C) in addition to the standard drugs (HRZE). Once again, treatment compliance was adequate, recovery was satisfactory, sputum-smear conversion occurred within the first 2 months, and the patient was considered cured upon completion of 8 months of DOT. Six additional nonhousehold contacts of Patient A were investigated, with an infection rate of 88% (5/6). All contacts with LTBI were treated with INH for either 6 or 9 months.

In February 2004, Patient C, one of Patient A’s grandchildren living in the same household, was diagnosed with sputum smear–positive TB. The same organism was identified. Patient C is currently on a directly observed regimen of INH, rifampin, pyrazinamide, and streptomycin (HRZS), is recovering well, and had sputum smear conversion within the first 2 months. Of the five household contacts of Patient C who were investigated, all were infected (infection rate of 100%). In addition, an infection rate of 55% (31/55) was found in high-risk nonhousehold contacts. In low-risk nonhousehold contacts, however, the infection rate was as low as 2% (1/52). Once again, all contacts with LTBI were treated with INH for either 6 or 9 months.

Recently, three more cases were diagnosed with sputum smear–positive or culture-positive TB, due to the same organism. They are summarized as follows:

  • In February 2004, Patient D, a step-grandparent and household contact of Patient C, was diagnosed with culture-positive TB.
  • In May 2004, Patient E was diagnosed with sputum smear–positive TB. Patient E was never named as a contact of Patient C. However, after RFLP matching, both cases were linked, with less than 3 hours’ exposure. Patient E is known to be HIV infected.
  • Also in May 2004, Patient F was diagnosed with culture-positive TB. Again, Patient F was not named as a contact of Patient C. After RFLP matching, however, Patient F was also linked to Patient C, having had occasional exposures totaling less than 4 hours per month. Patient F is also known to be HIV infected.

This case review shows that, in spite of prompt diagnosis and appropriate treatment of the cases, thorough contact identification and investigation, and adequate treatment for LTBI with INH, transmission of infection and occurrence of disease persisted. Infection rates for Patients A and C were 100% among high-risk household contacts, and were consistently high, even among high-risk nonhousehold contacts. The failure of INH treatment for LTBI to prevent disease, at least in Patient C, and possibly in Patient B, is an unusual finding. INH treatment for LTBI has been proven highly (at least 85%) effective at preventing disease.

Of note, documented transmission to Patients E and F, both HIV infected, was the result of very limited and short contact with Patient C. Even with an extremely timely and thorough TB contact investigation, this type of almost casual exposure usually will be missed. A high index of suspicion for HIV-infected contacts is obviously warranted, but in reality, the HIV status of contacts is often not known or not disclosed. As a result, it is advisable that all known HIV-infected persons, being highly susceptible to TB infection, have routine and regular tests for LTBI and TB disease. Treatment for LTBI is recommended for all coinfected persons. Timely assessment of risk and adequate prevention of TB will unquestionably improve the health and prolong the lives of HIV-infected persons.

—Reported by Peter Vranken, RN, DPH, MBA
EIS Officer, Office of Workforce and Career Development
Assigned to the Infectious Disease Epidemiology Section,
Louisiana Office of Public Health
and Carol Williams
Regional TB Manager, TB Control Section
Louisiana Office of Public Health

 


Released October 2008
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