Molecular epidemiology of tuberculosis in London 1995-7 showing low rate of active transmission.

BACKGROUND: Tuberculosis notification rates for London have risen dramatically in recent years. Molecular typing of Mycobacterium tuberculosis has contributed to our understanding of the epidemiology of tuberculosis throughout the world. This study aimed to assess the degree of recent transmission of M tuberculosis in London and subpopulations of the community with high rates of recent transmission. METHODS: M tuberculosis isolates from all persons from Greater London diagnosed with culture positive tuberculosis between 1 July 1995 and 31 December 1997 were genetically fingerprinted using IS6110 restriction fragment length polymorphism (RFLP) typing. A structured proforma was used during record review of cases of culture confirmed tuberculosis. Cluster analysis was performed and risk factors for clustering were examined in a univariate analysis followed by a logistic regression analysis with membership of a cluster as the outcome variable. RESULTS: RFLP patterns were obtained for 2042 isolates with more than four copies of IS6110; 463 (22.7%) belonged to 169 molecular clusters, which ranged in size from two (65% of clusters) to 12 persons. The estimated rate of recent transmission was 14.4%. Young age (0-19 years) (odds ratio (OR) 2.65, 95% confidence interval (CI) 1.59 to 4.44), birth in the UK (OR 1.55, 95% CI 1.04 to 2.03), black Caribbean ethnic group (OR 2.19, 95% CI 1.15 to 4.16), alcohol dependence (OR 2.33, 95% CI 1.46 to 3.72), and streptomycin resistance (OR 1.82, 95% CI 1.15 to 2.88) were independently associated with an increased risk of clustering. CONCLUSIONS: Tuberculosis in London is largely caused by reactivation or importation of infection by recent immigrants. Newly acquired infection is also common among people with recognised risk factors. Preventative interventions and early diagnosis of immigrants from areas with a high incidence of tuberculosis, together with thorough contact tracing and monitoring of treatment outcome among all cases of tuberculosis (especially in groups at higher risk of recent infection), remains most important.

Whole genome comparison of Campylobacter jejuni human isolates using a low-cost microarray reveals extensive genetic diversity.

Campylobacter jejuni is the leading cause of bacterial food-borne diarrhoeal disease throughout the world, and yet is still a poorly understood pathogen. Whole genome microarray comparisons of 11 C. jejuni strains of diverse origin identified genes in up to 30 NCTC 11168 loci ranging from 0.7 to 18.7 kb that are either absent or highly divergent in these isolates. Many of these regions are associated with the biosynthesis of surface structures including flagella, lipo-oligosaccharide, and the newly identified capsule. Other strain-variable genes of known function include those responsible for iron acquisition, DNA restriction/modification, and sialylation. In fact, at least 21% of genes in the sequenced strain appear dispensable as they are absent or highly divergent in one or more of the isolates tested, thus defining 1300 C. jejuni core genes. Such core genes contribute mainly to metabolic, biosynthetic, cellular, and regulatory processes, but many virulence determinants are also conserved. Comparison of the capsule biosynthesis locus revealed conservation of all the genes in this region in strains with the same Penner serotype as strain NCTC 11168. By contrast, between 5 and 17 NCTC 11168 genes in this region are either absent or highly divergent in strains of a different serotype from the sequenced strain, providing further evidence that the capsule accounts for Penner serotype specificity. These studies reveal extensive genetic diversity among C. jejuni strains and pave the way toward identifying correlates of pathogenicity and developing improved epidemiological tools for this problematic pathogen.

Pulmonary tuberculosis in Kumasi, Ghana: presentation, drug resistance, molecular epidemiology and outcome of treatment.

To assist implementation of tuberculosis (TB) control measures, knowledge of the disease characteristics in a community is essential. This study in Kumasi, Ghana, correlates the clinical presentation, microbiology, molecular epidemiology and clinical outcome of thirty consecutively diagnosed patients with new smear-positive pulmonary TB. Several important factors that potentially promote disease transmission in the community were identified: patients had prolonged duration of productive cough prior to diagnosis (mean=4.1 months; SD=2.1); the disease was typically advanced at presentation and Ziehl-Neelson sputum smears indicated a high bacterial load (80% graded > AFB++); home accommodation was overcrowded with a mean of 3.3 other persons sleeping in the same room as the patients at night. IS6110 restriction fragment length polymorphism (RFLP) fingerprinting of 25 isolated (23 Mycobacterium tuberculosis and 2 Mycobacterium africanum) from epidemiologically unrelated cases identified 3 identical strains and 3 clusters containing 2, 4 and 8 isolates of > or =80% similarity, suggesting high rates of disease transmission. A high prevalence of primary resistance to isoniazid was found (6 out 26; 23%) but resistance to rifampicin, pyrazinamide, ethambutol, streptomycin and ciprofloxacin was not detected. Smear coversion at 2 months and final outcome of treatment with short courses chemotherapy were independent of isoniazid resistance, but the rate of treatment default was unacceptably high (37%). High rates of disease transmission, primary isoniazid resistance and treatment default all indicate poor TB control. The use of rifampicin-containing short-course chemotherapy in this community must be accompanied by adequate resources and infrastructure to ensure very stringent treatment supervision to improve case-holding and reduce the risk of multi-drug resistance.

Rifapentine and isoniazid in the continuation phase of a 6-month regimen. Interim report: no activity of isoniazid in the continuation phase.

SETTING: Clinical trial amongst 762 patients with newly diagnosed pulmonary tuberculosis in Hong Kong. After an initial 2 months of a four-drug intensive phase consisting of streptomycin, isoniazid, rifampicin and pyrazinamide (SHRZ), a random allocation in continuation to once-weekly rifapentine + isoniazid (HRp1), HRp1 given in 2 of every 3 weeks (HRp1.2/3), or to three times weekly isoniazid + rifampicin (HR3). OBJECTIVE: Interim report evaluating progress of study and the role of isoniazid in the continuation phase. METHODS: Kaplan-Meier analysis and response of patients related to susceptibility of pretreatment organisms to isoniazid and to rate of isoniazid acetylation determined by NAT2 genotyping. RESULTS: In the 30-month follow-up, rates for adverse treatment events (failure and relapse) were 4.2% in the HR3, 10.2% in the HRp1 and 11.2% in the HRp1.2/3 series (P = 0.02 for HR3 vs HRp1 and P = 0.01 for HR3 vs HRp1.2/3). Occurrence of adverse events was not related to initial susceptibility to isoniazid nor to the rate of acetylation of isoniazid. CONCLUSIONS: The two rifapentine regimens had similar final rates of adverse events which were unsatisfactory. Isoniazid had little or no activity in the continuation phase, indicating that no improvement of the continuation regimen is likely to be obtained by alteration of the isoniazid dosage.

Chemically synthesised human immunodeficiency virus P7 nucleocapsid protein can self-assemble into particles and binds to a specific site on the tRNA(Lys,3) primer.

The zinc-bound form of the human immunodeficiency virus type 1 (HIV-1) nucleocapsid protein, p7, aggregates into particles visible by electron microscopy. The HIV primer tRNA(Lys,3) forms similar high molecular weight complexes with p7 that are also detected by gel mobility shift assays. RNA oligonucleotides of the three stem-loop structures in tRNA(Lys,3) were assayed for the competitive inhibition of p7-tRNA(Lys,3) binding by the intensities of free tRNA(Lys,3) bands on native gels. This reveals that the p7 binds specifically to the central domain of tRNA(Lys,3) where the D and T psi C loops come together, but not the anticodon stem-loop.

Overproduction and purification of Mycobacterium tuberculosis chaperonin 10.

The overexpression of the Mycobacterium tuberculosis chaperonin 10 (Cpn10)-encoding gene was accomplished using baculovirus expression vectors. The product was immunoreactive with a Cpn10 monoclonal antibody (mAb) and had an electrophoretic mobility identical to authentic Cpn10. The baculovirus system was most successful in terms of reaching nearly the full expression potential of the system. Recombinant Cpn10 was purified from recombinant baculovirus-infected Spodoptera frugiperda cells by isoelectrofocussing and size-exclusion chromatography. The baculovirus vector and purification methodology described represent a very powerful system for the large-scale production of the M. tuberculosis Cpn10 which may allow us to undertake structure-function analysis.