Biomedical subjects

Liangfen Zhang

Publications and source records attributed to Liangfen Zhang.

7 recordsLinked to original sources

PubMed2005

Polymorphism in the rpoT gene in Mycobacterium leprae isolates obtained from Latin American countries and its possible correlation with the spread of leprosy.

The genotypes of Mycobacterium leprae isolates originating from Mexico, Peru and Paraguay were analysed for the polymorphism of short tandem repeats in the rpoT gene. The genotype with four copies of the six-base tandem repeats in the rpoT gene was prominently predominant in Mexico, but the genotype of all isolates from Peru and Paraguay contained three copies of the six-base tandem repeats. These obvious different distributions might reflect the spread of leprosy by the different strains of M. leprae harboured by the various human races that moved to the American continent, as has been demonstrated in other infectious diseases.

Bacterial Proteins↗

PubMed2005

Diversity of potential short tandem repeats in Mycobacterium leprae and application for molecular typing.

A recent advance in molecular typing for tracing the transmission of leprosy is the discovery of short tandem repeats (STRs) in Mycobacterium leprae. To substantiate polymorphic loci from STR as promising candidates for molecular typing tools in leprosy epidemiology, 44 STR loci including 33 microsatellites and 11 minisatellites were investigated among 27 laboratory strains by sequencing PCR products. Not all STRs were necessarily polymorphic. Thirty-two out of the 44 loci were polymorphic. Nine polymorphic loci were suitable for identifying genotypes according to the discriminatory capacity, stability, and reproducibility. All the strains were classified into independent genotypes by the selected nine loci. Three multi-case households were subjected to molecular typing. M. leprae obtained from household cases showed identical copy numbers by TTC triplet alone, but the isolates from one family contact case were divided into different genotypes by adding eight other polymorphic loci. The combination of information from multiple loci allows increasing levels of discrimination and it is likely that the generation and documentation of data will result in the choice of a potential molecular typing tool for leprosy epidemiology.

Animals↗

PubMed2004

Genotyping of Mycobacterium leprae on the basis of the polymorphism of TTC repeats for analysis of leprosy transmission.

The polymorphism of TTC repeats in Mycobacterium leprae was examined using the bacilli obtained from residents in villages at North Maluku where M. leprae infections are highly endemic (as well as from patients at North Sulawesi of Indonesia) to elucidate the possible mode of leprosy transmission. TTC genotypes are stable for several generations of passages in nude mice footpads and, hence, are feasible for the genotyping of isolates and epidemiological analysis of leprosy transmission. It was found that bacilli with different TTC genotypes were distributed among residents at the same dwelling in villages in which leprosy is endemic and that some household contacts harbored bacilli with a different genotype from that harbored by the patient. Investigations of a father-and-son pair of patients indicated that infections of bacilli with 10 and 18 copies, respectively, had occurred. Genotypes of TTC repeats were found to differ between a son under treatment and two brothers. These results reveal the possibility that in addition to exposure via the presence of a leprosy patient with a multibacillary infection who was living with family members, there might have been some infectious sources to which the residents had been commonly exposed outside the dwellings. A limited discriminative capacity of the TTC polymorphism in the epidemiological analysis implies the need of searching other useful polymorphic loci for detailed subdivision of clinical isolates.

Animals↗

PubMed2004

A mutation at codon 516 in the rpoB gene of Mycobacterium leprae confers resistance to rifampin.

A missense mutation at codon 516 in the rpoB gene of Mycobacterium leprae conferring rifampin resistance was confirmed by the correlation between sequencing results and mouse footpad assay. The isolate was obtained from a relapsed lepromatous leprosy patient. This is the first report on the complete concordance between the mutation located at codon 516 in the rpoB gene and the corresponding resistance to rifampin in leprosy. The novel profile of mutation in the rpoB gene will contribute to the comprehensive understanding of rifampin resistant patterns and offer a useful tool for developing simple and rapid drug susceptibility testing approaches, which would promise more effective and successful control of leprosy.

Aged↗

PubMed2004

[Molecular epidemiology of the leprosy].

Application of molecular biological techniques to the epidemiological study of leprosy is described. Studies of detecting Mycobacterium leprae DNA in samples of the nasal mucus are discussed in terms of the epidemiology and the significance of high prevalence. Epidemiological studies on the transmission of leprosy and correlation between geographic distribution of different M. leprae rpoT genotypes and prehistoric spread of the leprosy by genotyping based on the genomic polymorphism are introduced.

Animals↗

PubMed2003

Leprosy in China.

Leprosy has definitely been present in China for at least 2,000 years. Through painstaking efforts over the past half century, China has put leprosy under control and reached the WHO's target at elimination of leprosy at the national and subnational level. But difficulties as well as problems like disabilities, discrimination, drug-resistance and dismissing of research still remain in the control of leprosy. Highly attention should be continuously paid on to attain the prevalence rate of less than 0.1/10,000 and the incidence rate below 0.5/100,000 in all counties (cities) throughout the country by the year 2010.

China↗

PubMed2002

A study on a possibility of predicting early relapse in leprosy using a ND-O-BSA based ELISA.

Serological methods have been used for detecting infection with Mycobacterium leprae. We have applied a serological test to explore the possibility it could detect a bacterial relapse among patients who have been cured with chemotherapy. More specifically we used an indirect enzyme-linked immunosorbant assay (ELISA) using the natural disaccharide (ND) of the phenolic glycolipid antigen of M. leprae linked to bovine serum albumin as antigen. Antibody levels were measured in sera from normal controls, active leprosy cases, cured leprosy patients, and relapsing leprosy patients. We correlated antibody levels with the type of leprosy, the bacterial index, and with relapse among cured leprosy patients. In our hands, the ND-ELISA, when applied to screening for infection with M. leprae, had excellent sensitivity, specificity, positive and negative predictive values, and both a low false positive rate and a low false negative rate. Antibody levels gradually increased among active patients from the tuberculoid to the lepromatous end of the leprosy spectrum. There was a year-by-year fall in antibody levels in patients responding to chemotherapy. Antibody levels and the bacterial index were correlated using the Spearman's rank correlation method. Serial antibody levels were measured in 666 leprosy patients after being cured with dapsone monotherapy. Over a three year follow up, 95 multibacillary patients became antibody positive and 12 of them had bacterial relapses of their disease. In contrast, among 335 cases that remained antibody negative, only one relapse was seen. Among 44 paucibacillary cured patients who became antibody positive, there was one relapse. There were 192 such patients who remained antibody negative and one relapsed. The risk of relapse is 6.7 times higher among cured multibacillary patients compared to cured paucibacillary patients. Overall, the cumulative relapse rate among antibody positive cases was 13.7%, compared to 0.4% among antibody negative patients. We conclude that the ND-ELISA is a useful tool both for screening for early infection with M. leprae and for predicting a relapse in cured patients, particularly in cured multibacillary patients.

Antibodies, Bacterial↗