Identifying children with tuberculosis among household contacts in The Gambia.

SETTING: Greater Banjul Area of the Gambia. OBJECTIVES: To identify co-prevalent tuberculosis (TB) among child contacts of adults with smear-positive TB. DESIGN: Child contacts aged <15 years in the immediate household and compound were prospectively enrolled and evaluated for TB disease using screening questionnaires and the tuberculin skin test (TST). Symptomatic and/or TST-positive (10 mm) contacts were further investigated. RESULTS: Of 4042 child contacts who underwent symptom screening and TST, 3339 (82.6%) were diagnosed as TB-exposed but not infected, 639 (15.8%) were latently infected and 64 (1.6%) had co-prevalent TB. Of the 64 TB cases, 50 (78.1%) were from within the immediate household of the index case, and 14 (21.9%) from within the same compound. Of the 27 asymptomatic but TST-positive children diagnosed with TB, 7 were microbiologically confirmed. The median age of the TB cases was 4.4 years (interquartile range 1.9-6.9); 53.1% were aged <5 years. Of the 4042 child contacts, 206 (5%) slept in the same bed as the index case; 28.1% of all TB cases occurred in this group. Symptom screening alone would have detected only 57.8% of the co-prevalent cases. CONCLUSION: In our community setting, if contact tracing is restricted to symptom screening and immediate households only, nearly half of all co-prevalent TB disease in child contacts would be missed.

Tuberculosis drug resistance in Bamako, Mali, from 2006 to 2014.

BACKGROUND: Although Drug resistance tuberculosis is not a new phenomenon, Mali remains one of the "blank" countries without systematic data. METHODS: Between 2006 and 2014, we enrolled pulmonary TB patients from local TB diagnostics centers and a university referral hospital in several observational cohort studies. These consecutive patients had first line drug susceptibility testing (DST) performed on their isolates. A subset of MDR was subsequently tested for second line drug resistance. RESULTS: A total of 1186 mycobacterial cultures were performed on samples from 522 patients, including 1105 sputa and 81 blood samples, yielding one or more Mycobacterium tuberculosis complex (Mtbc) positive cultures for 343 patients. Phenotypic DST was performed on 337 (98.3%) unique Mtbc isolates, of which 127 (37.7%) were resistant to at least one drug, including 75 (22.3%) with multidrug resistance (MDR). The overall prevalence of MDR-TB was 3.4% among new patients and 66.3% among retreatment patients. Second line DST was available for 38 (50.7%) of MDR patients and seven (18.4%) had resistance to either fluoroquinolones or second-line injectable drugs. CONCLUSION: The drug resistance levels, including MDR, found in this study are relatively high, likely related to the selected referral population. While worrisome, the numbers remained stable over the study period. These findings prompt a nationwide drug resistance survey, as well as continuous surveillance of all retreatment patients, which will provide more accurate results on countrywide drug resistance rates and ensure that MDR patients access appropriate second line treatment.

Contribution of Xpert® MTB/RIF to the diagnosis of pulmonary tuberculosis among TB-exposed children in The Gambia.

SETTING: Greater Banjul Area, The Gambia. OBJECTIVE: To conduct a pragmatic evaluation of the Xpert(®) MTB/RIF assay in the diagnosis of tuberculosis (TB) among child contacts. DESIGN: In this prospective study, one induced sputum sample was obtained from TB contacts aged <15 years and tested using fluorescent microscopy, culture and Xpert. The diagnostic accuracy of the microbiological tests was evaluated against culture and 'all TB diagnosis and treatment' as separate reference standards. RESULTS: Using culture as a reference standard, Xpert was positive for Mycobacterium tuberculosis in 6/14 culture-positive and 6/473 culture-negative children, giving a sensitivity and specificity of respectively 42.9% (95%CI 17.7-71.1) and 98.7% (95%CI 97.2-99.5). With 'all TB diagnosis and treatment' as a composite reference standard, combined Xpert and culture tests were positive for M. tuberculosis in 20/62 children with TB disease (32.3%, 95%CI 20.9-45.3), which was comparable to the yield from microscopy, culture and Xpert combined (33.9%, 95%CI 22.3-47.0), but significantly higher than individual yields from each test. CONCLUSION: The sensitivity of Xpert is low in actively traced child contacts, but a combination of Xpert and mycobacterial culture has incremental benefits for the bacteriological confirmation of TB disease.

Surveillance of drug-resistant Mycobacterium tuberculosis in The Gambia.

To determine the rates of drug-resistant tuberculosis in The Gambia, Mycobacterium tuberculosis isolates obtained from 225 patients during a nationwide survey were tested against isoniazid, rifampicin, ethambutol and streptomycin using the resistance ratio method. Only nine (4%) of the patients had strains that were resistant to one or more drugs. None of the patients with drug-resistant M. tuberculosis had previously been treated for tuberculosis. Drug-resistant tuberculosis is, as yet, not common in The Gambia. Periodic surveys for drug-resistant tuberculosis are recommended to monitor changes that may emerge over time.

High frequency volume coils for clinical NMR imaging and spectroscopy.

A tuned transmission line resonator has been developed in theory and in practical design for the clinical NMR volume coil application at 4.1 tesla. The distributed circuit transmission line resonator was designed for high frequency, large conductive volume applications where conventional lumped element coil designs perform less efficiently. The resonator design has made use of a resonant coaxial cavity, which could be variably tuned to the Larmor frequency of interest by tunable transmission line elements. Large head- and body-sized volumes, high efficiencies, and broad tuning ranges have been shown to be characteristic of the transmission line resonator to frequencies of 500 MHz. The B1 homogeneity of the resonator has been demonstrated to be a function of the electromagnetic properties of the load itself. By numerically solving Maxwell's equations for the fully time-dependent B1 field, coil homogeneity was predicted with finite-element models of anatomic structure, and inhomogeneities corrected for. A how-to exposition of coil design and construction has been included. Simple methods of quadrature driving and double tuning the transmission line resonator have also been presented. Human head images obtained with a tuned transmission line resonator at 175 MHz have clearly demonstrated uncompromised high field advantages of signal-to-noise and spatial resolution.