Evidence for local transmission and reactivation of tuberculosis in the Toronto Somali community

Increased risk of severe maternal morbidity (near-miss) among immigrant women in Sweden: a population register-based study

OBJECTIVE

To determine if immigrant women from low-, middle- and high-income countries have an increased risk of severe maternal morbidity (near-miss) when they deliver in Sweden.

DESIGN

Population register-based study.

SETTING

Nationwide study including all singleton deliveries (≥28 weeks of gestation) between 1998 and 2007.

POPULATION

Women with a near-miss event; all women with a singleton delivery ≥28 weeks of gestation during the same period acted as reference group.

METHODS

Near-miss was defined by a combined clinical and management approach with use of International Classification of Diseases, 10th revision codes for severe maternal morbidity. A woman's country of origin was designated as low-, middle- or high-income according to the World Bank Classification of 2009. Unconditional logistic regression models were used in the analysis.

MAIN OUTCOME MEASURES

Maternal near-miss frequencies per 1000 deliveries and odds ratios with 95% confidence intervals.

RESULTS

There were 914 474 deliveries during the study period and 2655 near-misses (2.9 per 1000 deliveries). In comparison to Swedish-born women, those from low-income countries had an increased risk of near-miss (odds ratio 2.3, 95% confidence interval 1.9-2.8) that was significant in all morbidity groups except for cardiovascular diseases and sepsis. Women from middle- and high-income countries showed no increased risk of near-miss.

CONCLUSIONS

Women from low-income countries have an increased risk of maternal near-miss morbidity compared with women born in Sweden. Although the rate is low it should alert healthcare providers.

Potential of rapid diagnosis for controlling drug-susceptible and drug-resistant tuberculosis in communities where Mycobacterium tuberculosis infections are highly prevalent

The long-term persistence of Mycobacterium tuberculosis in communities with high tuberculosis prevalence is a serious problem aggravated by the presence of drug-resistant tuberculosis strains. Drug resistance in an individual patient is often discovered only after a long delay, particularly if the diagnosis is based on current culture-based drug sensitivity testing methods. During such delays, the patient may transmit tuberculosis to his or her contacts. Rapid diagnosis of drug resistance would be expected to reduce this transmission and hence to decrease the prevalence of drug-resistant strains. To investigate this quantitatively, a mathematical model was constructed, assuming a homogeneous population structure typical of communities in South Africa where tuberculosis incidence is high. Computer simulations performed with this model showed that current control strategies will not halt the spread of multidrug-resistant tuberculosis in such communities. The simulations showed that the rapid diagnosis of drug resistance can be expected to reduce the incidence of drug-resistant cases provided the additional measure of screening within the community is implemented.

DNA restriction fragment length polymorphism analysis of Mycobacterium tuberculosis isolates from HIV-seropositive and HIV-seronegative patients in Kampala, Uganda

BACKGROUND

The identification and differentiation of strains of Mycobacterium tuberculosis by DNA fingerprinting has provided a better understanding of the epidemiology and tracing the transmission of tuberculosis. We set out to determine if there was a relationship between the risk of belonging to a group of tuberculosis patients with identical mycobacterial DNA fingerprint patterns and the HIV sero-status of the individuals in a high TB incidence peri-urban setting of Kampala, Uganda.

METHODS

One hundred eighty three isolates of Mycobacterium tuberculosis from 80 HIV seropositive and 103 HIV seronegative patients were fingerprinted by standard IS6110-RFLP. Using the BioNumerics software, strains were considered to be clustered if at least one other patient had an isolate with identical RFLP pattern.

RESULTS

One hundred and eighteen different fingerprint patterns were obtained from the 183 isolates. There were 34 clusters containing 54% (99/183) of the patients (average cluster size of 2.9), and a majority (96.2%) of the strains possessed a high copy number (> or = 5 copies) of the IS6110 element. When strains with <5 bands were excluded from the analysis, 50.3% (92/183) were clustered, and there was no difference in the level of diversity of DNA fingerprints observed in the two sero-groups (adjusted odds ratio [aOR] 0.85, 95%CI 0.46-1.56, P = 0.615), patients aged <40 years (aOR 0.53, 95%CI 0.25-1.12, P = 0.100), and sex (aOR 1.12, 95%CI 0.60-2.06, P = 0.715).

CONCLUSION

The sample showed evidence of a high prevalence of recent transmission with a high average cluster size, but infection with an isolate with a fingerprint found to be part of a cluster was not associated with any demographic or clinical characteristics, including HIV status.

Population-based molecular epidemiological study of tuberculosis in Malatya, Turkey

This investigation describes drug resistance patterns and genotyping data on a total of 145 Mycobacterium tuberculosis strains isolated between 2000 and 2004 in Malatya, Turkey. Drug susceptibility results indicated a total of 20% resistant and 4.8% of multidrug-resistant isolates. Spoligotyping resulted in 25 unique patterns and 120 strains in 19 clusters (2 to 33 strains per cluster). When the results were compared to an international spoligotyping database, 19 of 25 unique patterns matched existing shared spoligotype international types (SITs). This led to the description of 38 SITs with 139 strains and 6 orphan patterns (not previously reported). Five of the SITs (SIT759, SIT1936, SIT1937, SIT1938, and SIT2285) were newly created. The most prevalent spoligotype was SIT41 (LAM7-TUR) with 33 (23.9%) isolates. The repartition of strains according to major M. tuberculosis clades (in decreasing order) was as follows: ill-defined T clade (45.7%) > Latin American and Mediterranean (LAM; 29%) > Haarlem (15.9%). Strains belonging to Central Asian (CAS), East-African Indian (EAI), Beijing, and Africanum clades were absent in this setting. IS6110-restriction fragment length polymorphism (RFLP) resulted in 19 clusters (52 strains), with a final clustering rate of 35.9% and a recent transmission rate of 22.8%. Typing based on mycobacterial interspersed repetitive units (MIRUs) permitted us to identify 65 patterns (23 orphan patterns and 42 patterns that matched existing MIRU international types in an updated database). The combination of the three typing methods allowed us to calculate a final clustering rate of 22% and a significantly lower transmission rate of 13.1%. The discrimination achieved by IS6110-RFLP/MIRUs was not significantly improved by adding spoligotyping results (1.4%). We conclude that our patient population is infected by diverse M. tuberculosis populations; however, the majority of the ongoing transmission is due to "evolutionary recent" tuberculosis lineages belonging to principal genetic group 2 (PGG2; Haarlem and LAM) and PGG3 (ill-defined T clade), and most of it is attributable to the LAM7-TUR sublineage with an enhanced phylogeographical specificity for Turkey. An absence of lineages belonging to PGG1 clones (EAI, CAS, and Beijing, essentially found in Central, South, and Southeast Asia), is noteworthy.

Immunogenicity of eight dormancy regulon-encoded proteins of Mycobacterium tuberculosis in DNA-vaccinated and tuberculosis-infected mice

Hypoxia and low concentrations of nitric oxide have been reported to upregulate in vitro gene expression of 48 proteins of the dormancy (DosR) regulon of Mycobacterium tuberculosis. These proteins are thought to be essential for the survival of bacteria during persistence in vivo and are targeted by the immune system during latent infection in humans. Here we have analyzed the immunogenicity of eight DosR regulon-encoded antigens by plasmid DNA vaccination of BALB/c and C57BL/6 mice, i.e., Rv1733c, Rv1738, Rv2029c (pfkB), Rv2031c/hspX (acr), Rv2032 (acg), Rv2626c, Rv2627c, and Rv2628. Strong humoral and/or cellular Th1-type (interleukin-2 and gamma interferon) immune responses could be induced against all but one (Rv1738) of these antigens. The strongest Th1 responses were measured following vaccination with DNA encoding Rv2031c and Rv2626c. Using synthetic 20-mer overlapping peptides, 11 immunodominant, predicted major histocompatibility complex class II-restricted epitopes and one K(d)-restricted T-cell epitope could be identified. BALB/c and (B6D2)F(1) mice persistently infected with M. tuberculosis developed immune responses against Rv1733c, Rv2031c, and Rv2626c. These findings have implications for proof-of-concept studies in mice mimicking tuberculosis (TB) latency models and their extrapolation to humans for potential new vaccination strategies against TB.