Multidrug-resistant tuberculosis outbreak in an Italian prison: tolerance of pyrazinamide plus levofloxacin prophylaxis and serial interferon gamma release assays.

The optimal treatment for latent tuberculosis infection (LTBI) in subjects exposed to multidrug-resistant (MDR) tuberculosis (TB) remains unclear, and the change in response of the QuantiFERON-TB Gold In-Tube (QTB-IT) test during and after treatment is unknown. Between May 2010 and August 2010, 39 prisoners at the 'Casa Circondariale' of Modena, Italy, were exposed to a patient with active pulmonary MDR TB. All contacts were tested with the tuberculin skin test and QTB-IT. Upon exclusion of active TB, subjects positive to both tests were offered 6 months' treatment with pyrazinamide (PZA) and levofloxacin (LVX). QTB-IT testing was repeated at 3 and 6 months after initial testing in all subjects who were offered LTBI treatment. Seventeen (43.5%) of 39 subjects tested positive to both tuberculin skin test and QTB-IT test, and 12 (70.5%) agreed to receive therapy with PZA and LVX at standard doses. Only five (41.6%) of 12 subjects completed 6 months' treatment. Reasons for discontinuation were asymptomatic hepatitis, gastritis and diarrhoea. The QTB-IT values decreased in all subjects who completed the treatment, in two (33%) of six of those who received treatment for less than 3 months and in one (50%) of two patients who discontinued therapy after 3 months. The QTB-IT test results never turned negative. Despite the small number of subjects, the study confirmed that PZA plus LVX is a poorly tolerated option for MDR LTBI treatment. We observed a large degree of variation in the results of the QTB-IT test results among participants. The study confirmed that the interferon gamma release assay is not a reliable tool for monitoring the treatment of MDR LTBI in clinical practice.

Interferon-gamma-release assays detect recent tuberculosis re-infection in elderly contacts.

The tuberculin skin test (TST) does not discriminate between recent and remote latent tuberculosis infection (LTBI). This study was carried out to test two interferon-gamma-based blood assays in recent contacts with high prevalence of remote LTBI. We performed a contact tracing investigation in a nursing home for the elderly, where elderly patients were exposed to a case of pulmonary tuberculosis. TST, QuantiFERON-TB Gold (QFT-G) and T-SPOT.TB (TS.TB) were performed 8 weeks after the end of potential exposure. IFN-gamma measurements were recorded and correlation with exposure was evaluated. Twenty-seven (37.5%), 32 (44.4%) and 16 (22.2%) subjects were TST, TS.TB and QFT-G positive, respectively; agreement between TS.TB and QFT-G was good among exposed subjects only (K=0.915, 0.218 in unexposed, p<0.001). When amounts of IFN-gamma were corrected for the number of producing T cells, specific IFN-gamma production was significantly different between exposed and unexposed individuals (16.75+/-5.40 vs 2.33+/-0.71 IFN-gamma IU/1000 SFC, p=0.0001). QFT-G and TS.TB provided discordant results among elderly contacts. Unlike TST, the specific IFN-gamma response might discriminate between recent and long-lasting tuberculosis infection.

Posttransplant Mycobacterium tuberculosis disease following liver transplantation and the need for cautious evaluation of Quantiferon TB GOLD results in the transplant setting: a case report.

This report describes a case of pulmonary tuberculosis in a liver transplant patient without a history of previous exposure to Mycobacterium tuberculosis (MTB) complex. Prior to transplantation, the tuberculin skin test was negative and the QuantiFERON-TB Gold (QFT Gold), an interferon gamma-based blood test, was negative before and after transplant including a period beginning on postoperative day 55 when the patient developed a febrile illness with an interstitial infiltrate and pleural effusion that was unresponsive to broad-spectrum antibiotic therapy. Empiric treatment with isoniazid, ethambutol, and levofloxacin resulted in resolution of the clinical symptoms. A sputum culture grew MTB on postoperative day 87. This case illustrates the need for caution when QFT Gold is used as diagnostic tool for latent tuberculosis during the pretransplant assessment. Further studies evaluating the usefulness of QFT Gold and other interferon gamma tests in posttransplantation active infection are warranted.