Sean R. Toney

Prospective Comparison of the Tuberculin Skin Test and 2 Whole-Blood Interferon-γ Release Assays in Persons with Suspected Tuberculosis

BACKGROUND Interferon-gamma release assays (IGRAs) are attractive alternatives to the tuberculin skin test (TST) for detecting Mycobacterium tuberculosis infection. However, the inability to definitively confirm the presence of most M. tuberculosis infections hampers assessment of IGRA accuracy. Although IGRAs are primarily indicated for the detection of latent tuberculosis infection, we sought to determine the sensitivity of the TST and 2 whole-blood IGRAs (QuantiFERON-TB assay [QFT] and QuantiFERON-TB Gold assay [QFT-G]) in situations in which infection is confirmed by recovery of M. tuberculosis by culture. METHODS We conducted a prospective, multicenter, cross-sectional comparison study in which 148 persons suspected to have tuberculosis were tested simultaneously with the TST, QFT, and QFT-G. RESULTS M. tuberculosis was cultured from samples from 69 (47%) of 148 persons suspected to have tuberculosis; the TST induration was > or = 5 mm for 51 (73.9%) of the 69 subjects (95% confidence interval [CI], 62.5%-82.8%). The QFT indicated tuberculosis infection for 48 (69.6%) of the 69 subjects (95% CI, 57.9%-79.2%) and was indeterminate for 7 (10.1%). The QFT-G yielded positive results for 46 (66.7%) of the 69 subjects (95% CI, 54.9%-76.7%) and indeterminate results for 9 subjects (13.0%). If subjects with indeterminate QFT-G results were excluded, 46 (76.7%) of 60 subjects (95% CI, 64.6%-85.6%) had positive TST results, and the same number of subjects had positive QFT-G results. HIV infection was associated with false-negative TST results but not with false-negative QFT-G results. CONCLUSIONS The TST, QFT, and QFT-G have similar sensitivity in persons with culture-confirmed infection. As with the TST, negative QFT and QFT-G results should not be used to exclude the diagnosis of tuberculosis in persons with suggestive signs or symptoms.

Detection of Mycobacterium tuberculosis Infection in United States Navy Recruits Using the Tuberculin Skin Test or Whole-Blood Interferon-γ Release Assays

Background Military personnel are at risk for acquiring Mycobacterium tuberculosis infection because of activities in close quarters and in regions with a high prevalence of tuberculosis (TB). Accurate tests are needed to avoid unnecessary treatment because of false-positive results and to avoid TB because of false-negative results and failure to diagnose and treat M. tuberculosis infection. We sought to estimate the specificity of the tuberculin skin test (TST) and 2 whole-blood interferon-gamma release assays (QuantiFERON-TB assay [QFT] and QuantiFERON-TB Gold assay [QFT-G]) and to identify factors associated with test discordance. Methods A cross-sectional comparison study was performed in which 856 US Navy recruits were tested for M. tuberculosis infection using the TST, QFT, and QFT-G. Results Among the study subjects, 5.1% of TSTs resulted in an induration > or = 10 mm, and 2.9% of TSTs resulted in an induration > or = 15 mm. Eleven percent of QFT results and 0.6% of QFT-G results were positive. Assuming recruits at low risk for M. tuberculosis exposure were not infected, estimates of TST specificity were 99.1% (95% confidence interval [CI], 98.3%-99.9%) when a 15-mm cutoff value was used and 98.4% (95% CI, 97.3%-99.4%) when a 10-mm cutoff value was used. The estimated QFT specificity was 92.3% (95% CI, 90.0%-94.5%), and the estimated QFT-G specificity was 99.8% (95% CI, 99.5%-100%). Recruits who were born in countries with a high prevalence of TB were 26-40 times more likely to have discordant results involving a positive TST result and a negative QFT-G result than were recruits born in countries with a low prevalence of TB. Nineteen (50%) of 38 recruits with this type of discordant results had a TST induration > or = 15 mm. Conclusions The QFT-G and TST are more specific than the QFT. No statistically significant difference in specificity between the QFT-G and TST was found using a 15-mm induration cutoff value. The discordant results observed among recruits with increased risk of M. tuberculosis infection may have been because of lower TST specificity or lower QFT-G sensitivity. Negative QFT-G results for recruits born in countries where TB is highly prevalent and whose TST induration was > or = 15 mm suggest that the QFT-G may be less sensitive than the TST. Additional studies are needed to determine the risk of TB when TST and QFT-G results are discordant.

Furunculosis Due to Mycobacterium mageritense Associated with Footbaths at a Nail Salon

ABSTRACT We report two cases of lower-extremity furunculosis caused by Mycobacterium mageritense. Both patients were patrons of the same nail salon, where they received footbaths prior to pedicures. M. mageritense bacteria isolated from two whirlpool footbaths were determined to be closely related to the patient isolates by pulsed-field gel electrophoresis.

Persistence of Nontuberculous Mycobacteria in a Drinking Water System after Addition of Filtration Treatment

ABSTRACT There is evidence that drinking water may be a source of infections with pathogenic nontuberculous mycobacteria (NTM) in humans. One method by which NTM are believed to enter drinking water distribution systems is by their intracellular colonization of protozoa. Our goal was to determine whether we could detect a reduction in the prevalence of NTM recovered from an unfiltered surface drinking water system after the addition of ozonation and filtration treatment and to characterize NTM isolates by using molecular methods. We sampled water from two initially unfiltered surface drinking water treatment plants over a 29-month period. One plant received the addition of filtration and ozonation after 6 months of sampling. Sample sites included those at treatment plant effluents, distributed water, and cold water taps (point-of-use [POU] sites) in public or commercial buildings located within each distribution system. NTM were recovered from 27% of the sites. POU sites yielded the majority of NTM, with >50% recovery despite the addition of ozonation and filtration. Closely related electrophoretic groups of Mycobacterium avium were found to persist at POU sites for up to 26 months. Water collected from POU cold water outlets was persistently colonized with NTM despite the addition of ozonation and filtration to a drinking water system. This suggests that cold water POU outlets need to be considered as a potential source of chronic human exposure to NTM.

Multidrug-Resistant Tuberculosis Outbreak among US-bound Hmong Refugees, Thailand, 2005

Enhanced pre-immigration screening and program expansion decreased TB importation.

Multiphasic Approach Reveals Genetic Diversity of Environmental and Patient Isolates of Mycobacterium mucogenicum and Mycobacterium phocaicum Associated with an Outbreak of Bacteremias at a Texas Hospital

ABSTRACT Between March and May 2006, a Texas hospital identified five Mycobacterium mucogenicum bloodstream infections among hospitalized oncology patients using fluorescence high-performance liquid chromatography analysis of mycolic acids. Isolates from blood cultures were compared to 16 isolates from environmental sites or water associated with this ward. These isolates were further characterized by hsp65, 16S rRNA, and rpoB gene sequencing, hsp65 PCR restriction analysis, and molecular typing methods, including repetitive element PCR, random amplified polymorphic DNA PCR, and pulsed-field gel electrophoresis (PFGE) of large restriction fragments. Three of five patient isolates were confirmed as M. mucogenicum and were in a single cluster as determined by all identification and typing methods. The remaining two patient isolates were identified as different strains of Mycobacterium phocaicum by rpoB sequence analysis. One of these matched an environmental isolate from a swab of a hand shower in the patients room, while none of the clinical isolates of M. mucogenicum matched environmental strains. Among the other 15 environmental isolates, 11 were identified as M. mucogenicum and 4 as M. phocaicum strains, all of which were unrelated by typing methods. Although the 16S rRNA gene sequences matched for all 14 M. mucogenicum isolates, there were two each of the hsp65 and rpoB sequevars, seven PCR typing patterns, and 12 PFGE patterns. Among the seven M. phocaicum isolates were three 16S rRNA sequevars, two hsp65 sequevars, two rpoB sequevars, six PCR typing patterns, and six PFGE patterns. This outbreak represents the first case of catheter-associated bacteremia caused by M. phocaicum and the first report of clinical isolates from a U.S. hospital. The investigation highlights important differences in the available typing methods for mycobacteria and demonstrates the genetic diversity of these organisms even within narrow confines of time and space.

First Isolations of Segniliparus rugosus from Patients with Cystic Fibrosis

ABSTRACT We report three cases of the new genus Segniliparus isolated from patients with cystic fibrosis. All isolates were unambiguously identified by 16S rRNA gene sequencing as Segniliparus rugosus (GenBank accession no. AY 60892). Drug susceptibility results that may enhance treatment for cystic fibrosis patients with this opportunistic pathogen are presented.

Molecular Comparison of Mycobacterium avium Isolates from Clinical and Environmental Sources

ABSTRACT We collected Mycobacterium avium isolates from clinical and drinking-water sources and compared isolates among themselves and to each other using molecular methods. Four clinical isolates were related to water isolates. Groups of indistinguishable clinical isolates were identified. The groups of identical clinical isolates suggest a common source of exposure.

Characterization of a novel rapidly growing Mycobacterium species associated with sepsis.

ABSTRACT A rapidly growing mycobacterium was isolated five times from blood cultures from a 6-year-old female patient with relapsed pre-B-cell acute lymphocytic leukemia. All five isolates had identical nucleotide sequences for the first 500 bp of the 16S rRNA gene, indicative of a single species. High-performance liquid chromatography analysis of mycolic acids indicated that the species was similar to Mycobacterium smegmatis. Sequence analysis of the 16S rRNA gene (1,455 bp) for one isolate demonstrated that the species was closely related to Mycobacterium diernhoferi. Based on the phenotypic features and phylogenetic analysis, it was concluded that the isolates represented a novel rapidly growing Mycobacterium species. The name “Mycobacterium hackensackense” is proposed for this unique strain, 147-0552T, which was deposited in the American Type Culture Collection as ATCC BAA-823T.

Point-of-Use Membrane Filtration and Hyperchlorination to Prevent Patient Exposure to Rapidly Growing Mycobacteria in the Potable Water Supply of a Skilled Nursing Facility

BACKGROUND Healthcare-associated outbreaks and pseudo-outbreaks of rapidly growing mycobacteria (RGM) are frequently associated with contaminated tap water. A pseudo-outbreak of Mycobacterium chelonae-M. abscessus in patients undergoing bronchoscopy was identified by 2 acute care hospitals. RGM was identified in bronchoscopy specimens of 28 patients, 25 of whom resided in the same skilled nursing facility (SNF). An investigation ruled out bronchoscopy procedures, specimen collection, and scope reprocessing at the hospitals as sources of transmission. OBJECTIVE To identify the reservoir for RGM within the SNF and evaluate 2 water system treatments, hyperchlorination and point-of-use (POU) membrane filters, to reduce RGM. DESIGN A comparative in situ study of 2 water system treatments to prevent RGM transmission. SETTING An SNF specializing in care of patients requiring ventilator support. METHODS RGM and heterotrophic plate count (HPC) bacteria were examined in facility water before and after hyperchlorination and in a subsequent 24-week assessment of filtered water by colony enumeration on Middlebrook and R2A media. RESULTS Mycobacterium chelonae was consistently isolated from the SNF water supply. Hyperchlorination reduced RGM by 1.5 log(10) initially, but the population returned to original levels within 90 days. Concentration of HPC bacteria also decreased temporarily. RGM were reduced below detection level in filtered water, a 3-log(10) reduction. HPC bacteria were not recovered from newly installed filters, although low quantities were found in water from 2-week-old filters. CONCLUSION POU membrane filters may be a feasible prevention measure for healthcare facilities to limit exposure of sensitive individuals to RGM in potable water systems.