Multiple strain infection of Mycobacterium leprae in a family having 4 patients: A study employing short tandem repeats

Molecular epidemiology of leprosy: An update

Molecular epidemiology investigations are notoriously challenging in the leprosy field mainly because the inherent characteristics of the disease as well as its yet uncultivated causative agents, Mycobacterium leprae and M. lepromatosis. Despite significant developments in understanding the biology of leprosy bacilli through genomic approaches, the exact mechanisms of transmission is still unclear and the factors underlying pathological variation of the disease in different patients remain as major gaps in our knowledge about leprosy. Despite these difficulties, the last two decades have seen the development of genotyping procedures based on PCR-sequencing of target loci as well as by the genome-wide analysis of an increasing number of geographically diverse isolates of leprosy bacilli. This has provided a foundation for molecular epidemiology studies that are bringing a better understanding of strain evolution associated with ancient human migrations, and phylogeographical insights about the spread of disease globally. This review discusses the advantages and drawbacks of the main tools available for molecular epidemiological investigations of leprosy and summarizes various methods ranging from PCR-based genotyping to genome-typing techniques. We also describe their main applications in analyzing the short-range and long-range transmission of the disease. Finally, we summarise the current gaps and challenges that remain in the field of molecular epidemiology of leprosy.

The role of an active surveillance strategy of targeting household and neighborhood contacts related to leprosy cases released from treatment in a low-endemic area of China

Objective

Early diagnosis remains the primary goal for leprosy management programs. This study aims to determine whether active surveillance of patients with leprosy and their contact individuals increased identification of latent leprosy cases in the low-endemic areas.

Methods

This cross-sectional survey was carried out between October 2014 and August 2016 in 21 counties throughout Shandong Province. The survey was conducted among patients with leprosy released from treatment (RFT) and their contacts from both household and neighbors.

Results

A total of 2,210 RFT patients and 9,742 contacts comprising 7877 household contacts (HHCs), including 5,844 genetic related family members (GRFMs) and 2033 non-genetic related family members and 1,865 contacts living in neighboring houses (neighbor contacts, NCs), were recruited. Among identified individuals, one relapsed and 13 were newly diagnosed, giving a detection rate of 0.12%, corresponding to 120 times the passive case detection rate. Detection rates were similar for HHCs and NCs (0.114% vs. 0.214%, P = 0.287). Analysis of the family history of leprosy patients revealed clustering of newly diagnosed cases and association with residential coordinates of previously-diagnosed multibacillary leprosy cases.

Conclusion

Active case-finding programs are feasible and contributes to early case detection by tracking HHCs and NCs in low-endemic areas.

Leprosy has been eliminated as a public health problem in 1994 in Shandong Province. However, the district continues to report a relatively high number of cases of leprosy infection involving deformity. Several studies have shown that individuals in contact with people infected with leprosy are at high risk of developing the disease. Subclinical infections among such individuals are important in the chain of M. leprae transmission. Some hyperendemic areas show growing interest in active case finding (ACF). Recent data from the World Health Organization (WHO) show that high rates of relapsed patients, grade 2 disability (G2D) since 2011, and the extensive family history of leprosy among people in Shandong Province P.R. China, indicate a need to reconsider the current approach to leprosy prevention. Active case finding was conducted in 21 counties of Shandong Province among patients with leprosy released from treatment (RFT) and their contacts. We achieved a detection rate of 0.12%, which was much higher than the rate for passive case finding. Our ACF program confirmed the need to implement this strategy among families and neighbors of RFT patients in historically high-endemic areas of leprosy. The program could reduce the risk of G2D by facilitating early detection and treatment, thereby reducing the disease burden.

Structures and stability of simple DNA repeats from bacteria

DNA is a fundamentally important molecule for all cellular organisms due to its biological role as the store of hereditary, genetic information. On the one hand, genomic DNA is very stable, both in chemical and biological contexts, and this assists its genetic functions. On the other hand, it is also a dynamic molecule, and constant changes in its structure and sequence drive many biological processes, including adaptation and evolution of organisms. DNA genomes contain significant amounts of repetitive sequences, which have divergent functions in the complex processes that involve DNA, including replication, recombination, repair, and transcription. Through their involvement in these processes, repetitive DNA sequences influence the genetic instability and evolution of DNA molecules and they are located non-randomly in all genomes. Mechanisms that influence such genetic instability have been studied in many organisms, including within human genomes where they are linked to various human diseases. Here, we review our understanding of short, simple DNA repeats across a diverse range of bacteria, comparing the prevalence of repetitive DNA sequences in different genomes. We describe the range of DNA structures that have been observed in such repeats, focusing on their propensity to form local, non-B-DNA structures. Finally, we discuss the biological significance of such unusual DNA structures and relate this to studies where the impacts of DNA metabolism on genetic stability are linked to human diseases. Overall, we show that simple DNA repeats in bacteria serve as excellent and tractable experimental models for biochemical studies of their cellular functions and influences.