Migration histories of multidrug-resistant tuberculosis patients from the Thailand-Myanmar border, 2012-2014.

SETTING: Multidrug-resistant tuberculosis (MDR-TB) is a growing public health threat in South-East Asia. TB is typically a disease of poverty and can be spread by infectious humans who migrate from one region to another. DESIGN: We interviewed 20 MDR-TB patients on the Thailand-Myanmar border with regard to their migration histories. Migration origins and destinations were mapped. RESULTS: All but one participant had a history of migration, and maps of migration ranges revealed wide geographic dispersal. Most described living and work conditions that could contribute to the spread of drug-resistant TB, including numerous contacts and crowded living quarters. CONCLUSION: Our results show that at least some migrant workers in the region carry MDR-TB, and indicate that this subgroup of the population is important with regard to the transmission of MDR-TB throughout the region. Migrants in this region come into contact with high numbers of people and may be able to spread the disease across wide geographic ranges. Access to diagnosis and treatment and socio-economic development are at least as important as any TB control measures, meaning that innovative and bold approaches that extend across international borders are needed to address these problems.

A paradigm for the molecular identification of Mycobacterium species in a routine diagnostic laboratory.

The aim of this study was to improve the identification of Mycobacterium species in the context of a UK teaching hospital. Real-time PCR assays were established to enable the rapid differentiation between Mycobacterium tuberculosis (MTB) complex and Mycobacterium species other than tuberculosis (MOTT), followed by 16S rRNA gene sequencing for the speciation of MOTT. Real-time PCR assays gave comparable results to those from the reference laboratory. The implementation of these PCR assays using an improved bead extraction method has enhanced the mycobacterial diagnostic service at the Royal Free Hospital by providing a rapid means of differentiating between MTB complex and MOTT, and would be simple to implement in similar laboratories. Sequence analysis successfully identified a range of Mycobacterium spp. representative of those encountered in the clinical setting of the authors, including Mycobacterium avium complex, Mycobacterium fortuitum group, Mycobacterium chelonae-Mycobacterium abscessus group, Mycobacterium xenopi and Mycobacterium gordonae. It provides a useful tool for the identification of MOTT when clinically indicated.

Prospective evaluation of BDProbeTec strand displacement amplification (SDA) system for diagnosis of tuberculosis in non-respiratory and respiratory samples.

Nucleic acid amplification techniques (NAATs) have been demonstrated to make significant improvements in the diagnosis of tuberculosis (TB), particularly in the time to diagnosis and the diagnosis of smear-negative TB. The BD ProbeTec strand displacement amplification (SDA) system for the diagnosis of pulmonary and non-pulmonary tuberculosis was evaluated. A total of 689 samples were analysed from patients with clinically suspected TB. Compared with culture, the sensitivity and specificity for pulmonary samples were 98 and 89 %, and against final clinical diagnosis 93 and 92 %, respectively. This assay has undergone limited evaluation for non-respiratory samples and so 331 non-respiratory samples were tested, identifying those specimens that were likely to yield a useful result. These were CSF (n = 104), fine needle aspirates (n = 64) and pus (n = 41). Pleural fluid (n = 47) was identified as a poor specimen. A concern in using the SDA assay was that low-positive samples were difficult to interpret; 7.8 % of specimens fell into this category. Indeed, 64 % of the discrepant results, when compared to final clinical diagnosis, could be assigned as low-positive samples. Specimen type did not predict likelihood of a sample being in the low-positive zone. Although the manufacturers do not describe the concept of a low-positive zone, we have found that it aids clinical diagnosis.

Identification of different Borrelia burgdorferi genomic groups from Scottish ticks.

AIM: To characterise 12 Borrelia burgdorferi sensu lato isolates cultured from ticks collected in the Highlands of Scotland. METHODS: Three molecular methods were used: an outer surface membrane protein A (OSP A) gene polymerase chain reaction (PCR) designed to give different molecular weight products with different genomic groups, randomly amplified polymorphic DNA (RAPD) analysis, and ribosomal RNA (rRNA) gene PCRs using genomic group specific primers. RESULTS: All of the molecular methods used were quick and easy to perform and capable of differentiating between the different genomic groups of B burgdorferi sensu lato. All 12 tick isolates were characterised successfully with each method: five were characterised as B afzelii and seven were characterised as B burgdorferi sensu stricto. RAPD also identified differences within these genomic groups. CONCLUSIONS: From this study, it is now known that at least two different B burgdorferi sensu lato genomic groups are present in the Highlands of Scotland: B afzelii and B burgdorferi sensu stricto. This information can now be used to develop appropriate serological tests, which should improve the diagnosis and management of patients with Lyme disease in Scotland. The molecular methods chosen were found to be useful typing tools and will allow rapid identification of any future isolates.

Evidence-based diagnosis of Lyme disease.

The aim of this study was to make an evidence-based comparison of four commercial enzyme immunoassays (EIAs) (Serion Classics, Sigma Diagnostics, Cambridge Biotech and ICN Diagnostics) and an in-house enzyme immunoassay (EIA) in order to select the most appropriate screening assay for diagnosis of Lyme disease. Borrelia burgdorferi sensu stricto cultured in BSK-H medium was used to develop the in-house assay. Escherichia coli antigen (0.9 mg/ml) was included in the serum diluent to reduce non-specific background. Comparison of the number of tests needed to diagnose (i.e. to indicate a positive result) and the cost per positive diagnosis for the five assays was made using a panel of 176 Western blot-characterised sera. The Cambridge Biotech and Sigma assays had the highest sensitivity but poorer specificity, whereas the Serion and ICN assays had highest specificity but poorer sensitivity. The in-house assay had average sensitivity and specificity, the number of tests needed to diagnose being 2.32 compared to 1.92 for Serion, 2.17 for ICN, 2.5 for Sigma and 2.7 for Cambridge Biotech. In a diagnostic protocol that uses an EIA as screening test, with confirmation by Western blot, a good balance of sensitivity and specificity is essential. The in-house assay was the most cost-effective (lowest cost per positive diagnosis), and is probably the best option for specialist laboratories in Europe.

Isolation of Borrelia burgdorferi from ticks in the Highlands of Scotland.

Borrelia burgdorferi, the causative agent of Lyme disease, was first isolated in 1982 and since then has been regularly isolated from ticks and clinical material in both Continental Europe and the USA. However, only three isolations have been reported in Britain. During the summer of 1997, 128 ticks were collected from two sites in the Highlands of Scotland and examined by the polymerase chain reaction (PCR) and culture. Eleven fresh isolates were obtained from culture and passed up to 22 times. Seven of the tick emulsions were also positive by flagellin gene PCR, and a further one was positive by PCR but negative on culture. All 11 isolate cultures were positive by the flagellin gene PCR. Further studies on four of these isolates confirmed their identity by immunofluorescence, but also detected possible differences between them and B. burgdorferi ACA-1 by enzyme profiles and by PCR with OspA gene primers. Culture of these new strains provides antigens that should improve diagnostic serological tests in Britain.