Geographic Differences in Time to Culture Conversion in Liquid Media: Tuberculosis Trials Consortium Study 28. Culture Conversion Is Delayed in Africa

Tuberculosis Trials Consortium Study 28, was a double blind, randomized, placebo-controlled, phase 2 clinical trial examining smear positive pulmonary Mycobacterium tuberculosis. Over the course of intensive phase therapy, patients from African sites had substantially delayed and lower rates of culture conversion to negative in liquid media compared to non-African patients. We explored potential explanations of this finding.In TBTC Study 28, protocol-correct patients (n = 328) provided spot sputum specimens for M. tuberculosis culture in liquid media, at baseline and weeks 2, 4, 6 and 8 of study therapy. We compared sputum culture conversion for African and non-African patients stratified by four baseline measures of disease severity: AFB smear quantification, extent of disease on chest radiograph, cavity size and the number of days to detection of M. tuberculosis in liquid media using the Kaplan-Meier product-limit method. We evaluated specimen processing and culture procedures used at 29 study laboratories serving 27 sites.African TB patients had more extensive disease at enrollment than non-African patients. However, African patients with the least disease by the 4 measures of disease severity had conversion rates on liquid media that were substantially lower than conversion rates in non-African patients with the greatest extent of disease. HIV infection, smoking and diabetes did not explain delayed conversion in Africa. Some inter-site variation in laboratory processing and culture procedures within accepted practice for clinical diagnostic laboratories was found.Compared with patients from non-African sites, African patients being treated for TB had delayed sputum culture conversion and lower sputum conversion rates in liquid media that were not explained by baseline severity of disease, HIV status, age, smoking, diabetes or race. Further investigation is warranted into whether modest variation in laboratory processes substantially influences the efficacy outcomes of phase 2 TB treatment trials or if other factors (e.g., nutrition, host response) are involved.ClinicalTrials.gov NCT00144417

Mycobacterium tuberculosis Transmission from Human to Canine

A 71-year-old woman from Tennessee, USA with a 3-week history of a productive, nonbloody cough was evaluated. Chest radiograph showed infiltrates and atelectasis in the upper lobe of the right lung. A tuberculosis (TB) skin test resulted in a 14-mm area of induration. Sputum stained positive for acid-fast bacilli (AFB) and was positive for Mycobacterium tuberculosis by DNA probe and culture. Treatment was initiated with isoniazid, rifampicin, and pyrazinamide. After 14 days of daily, directly observed therapy, the patient complained of nausea, vomiting and diarrhoea. Treatment adjustments were made, and therapy was completed 11 months later with complete recovery. Six months after the patient\u27s TB diagnosis, she took her three and a half-year-old male Yorkshire Terrier to a veterinary clinic with cough, weight loss, and vomiting of several months\u27 duration. Initial sputum sample was negative on AFB staining. Eight days after discharge from a referral veterinary teaching hospital with a presumptive diagnosis of TB, the dog was euthanized due to urethral obstruction. Liver and tracheobronchial lymph node specimens collected at necropsy were positive for M. tuberculosis complex by polymerase chain reaction. The M. tuberculosis isolates from the dog and its owner had an indistinguishable 10-band pattern by IS6110-based restriction fragment length polymorphism genotyping

Two-Component Direct Fluorescent-Antibody Assay for Rapid Identification of Bacillus anthracis

A two-component direct fluorescent-antibody (DFA) assay, using fluorescein-labeled monoclonal antibodies specific to the Bacillus anthracis cell wall (CW-DFA) and capsule (CAP-DFA) antigens, was evaluated and validated for rapid identification of B. anthracis. We analyzed 230 B. anthracis isolates; 228 and 229 were positive by CW-DFA and CAP-DFA assays, respectively. We also tested 56 non–B. anthracis strains; 10 B. cereus and 2 B. thuringiensis were positive by the CW-DFA assay, and 1 B. megaterium strain was positive by CAP-DFA. Analysis of the combined DFA results identified 227 of 230 B. anthracis isolates; all 56 strains of the other Bacillus spp. were negative. Both DFA assays tested positive on 14 of 26 clinical specimens from the 2001 anthrax outbreak investigation. The two-component DFA assay is a sensitive, specific, and rapid confirmatory test for B. anthracis in cultures and may be useful directly on clinical specimens

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

Enhanced pre-immigration screening and program expansion decreased TB importation

Relapse Associated with Active Disease Caused by Beijing Strain of Mycobacterium tuberculosis1

Risk for relapse was higher among persons of Asian–Pacific Islander descent

Transfer of a Mycobacterium tuberculosis Genotyping Method, Spoligotyping, from a Reverse Line-Blot Hybridization, Membrane-Based Assay to the Luminex Multianalyte Profiling System

Spoligotyping using Luminex technology was shown to be a highly reproducible method suitable for high-throughput analysis. Spoligotyping of 48 isolates using the traditional membrane-based assay and the Luminex assay yielded concordant results for all isolates. The Luminex platform provides greater flexibility and cost effectiveness than the membrane-based assay

Evaluation of a Two-Step Approach for Large-Scale, Prospective Genotyping of Mycobacterium tuberculosis Isolates in the United States

Genotyping of Mycobacterium tuberculosis isolates is useful in tuberculosis control for confirming suspected transmission links, identifying unsuspected transmission, and detecting or confirming possible false-positive cultures. The value is greatly increased by reducing the turnaround time from positive culture to genotyping result and by increasing the proportion of cases for which results are available. Although IS6110 fingerprinting provides the highest discrimination, amplification-based methods allow rapid, high-throughput processing and yield digital results that can be readily analyzed and thus are better suited for large-scale genotyping. M. tuberculosis isolates (n = 259) representing 99% of culture-positive cases of tuberculosis diagnosed in Wisconsin in the years 2000 to 2003 were genotyped by using spoligotyping, mycobacterial interspersed repetitive unit (MIRU) typing, and IS6110 fingerprinting. Spoligotyping clustered 64.1% of the isolates, MIRU typing clustered 46.7% of the isolates, and IS6110 fingerprinting clustered 29.7% of the isolates. The combination of spoligotyping and MIRU typing yielded 184 unique isolates and 26 clusters containing 75 isolates (29.0%). The addition of IS6110 fingerprinting reduced the number of clustered isolates to 30 (11.6%) if an exact pattern match was required or to 44 (17.0%) if the definition of a matching IS6110 fingerprint was expanded to include patterns that differed by the addition of a single band. Regardless of the genotyping method chosen, the addition of a second or third method decreased clustering. Our results indicate that using spoligotyping and MIRU typing together provides adequate discrimination in most cases. IS6110 fingerprinting can then be used as a secondary typing method to type the clustered isolates when additional discrimination is needed

Relapse associated with active disease caused by Beijing strain of Mycobacterium tuberculosis.

The role of microbial factors in outcomes of tuberculosis treatment has not been well studied. We performed a case-control study to evaluate the association between a Beijing strain and tuberculosis treatment outcomes. Isolates from patients with culture-positive treatment failure (n = 8) or relapse (n = 54) were compared with isolates from randomly selected controls (n = 296) by using spoligotyping. Patients with Beijing strains had a higher risk for relapse (odds ratio [OR] 2.0, 95% confidence interval [CI] 1.0-4.0, p = 0.04) but not for treatment failure. Adjustment for factors previously associated with relapse had little effect on the association between Beijing strains and relapse. Beijing strains were strongly associated with relapse among Asian-Pacific Islanders (OR 11, 95% CI 1.1-108, p = 0.04). Active disease caused by a Beijing strain was associated with increased risk for relapse, particularly among Asian-Pacific Islanders