Detection of dapsone resistant Mycobacterium leprae by DNA sequence analysis from a Turkish relapsed leprosy patient

Mycobacterium leprae obtained from the relapsed case after 43-year dapsone monotherapy was submitted to sequence analysis of the genes associated with resistance to antileprosy drugs for drug susceptibility testing. Single nucleotide substitution was revealed at the codon 55 of the folP gene, which had been reported to confer resistance to dapsone. No mutations in the rpoB and gyrA genes indicated this isolate was susceptible to rifampicin and fluoroquino-les respectively. Drug susceptibility was conducted easily and rapidly by the sequence analysis compared with that by mouse footpad method

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

Molecular signatures identify a candidate target of balancing selection in an arcD-Like gene of Staphylococcus epidermidis

A comparative population genetics study revealed high levels of nucleotide polymorphism and intermediate-frequency alleles in an arcC gene of Staphylococcus epidermidis, but not in a homologous gene of the more aggressive human pathogen, Staphylococcus aureus. Further investigation showed that the arcC genes used in the multilocus sequence typing schemes of these two species were paralogs. Phylogenetic analyses of arcC-containing loci, including the arginine catabolic mobile element, from both species, suggested that these loci had an eventful history involving gene duplications, rearrangements, deletions, and horizontal transfers. The peak signatures in the polymorphic S. epidermidis locus were traced to an arcD-like gene adjacent to arcC; these signatures consisted of unusually elevated Tajima’s D and π/K ratios, which were robust to assumptions about recombination and species divergence time and among the most elevated in the S. epidermidis genome. Amino acid polymorphisms, including one that differed in polarity and hydropathy, were located in the peak signatures and defined two allelic lineages. Recombination events were detected between these allelic lineages and potential donors and recipients of S. epidermidis were identified in each case. By comparison, the orthologous gene of S. aureus showed no unusual signatures. The ArcD-like protein belonged to the unknown ion transporter 3 family and appeared to be unrelated to ArcD from the arginine deiminase pathway. These studies report the first comparative population genetics results for staphylococci and the first statistical evidence for a candidate target of balancing selection in S. epidermidis

Electrochemical Evaluation of Tumor Development via Cellular Interface Supported CRISPR/Cas Trans-Cleavage

Evaluating tumor development is of great importance for clinic treatment and therapy. It has been known that the amounts of sialic acids on tumor cell membrane surface are closely associated with the degree of cancerization of the cell. So, in this work, cellular interface supported CRISPR/Cas trans-cleavage has been explored for electrochemical simultaneous detection of two types of sialic acids, i.e., N-glycolylneuraminic acid (Neu5Gc) and N-acetylneuraminic acid (Neu5Ac). Specifically, PbS quantum dot-labeled DNA modified by Neu5Gc antibody is prepared to specifically recognize Neu5Gc on the cell surface, followed by the binding of Neu5Ac through our fabricated CdS quantum dot-labeled DNA modified by Sambucus nigra agglutinin. Subsequently, the activated Cas12a indiscriminately cleaves DNA, resulting in the release of PbS and CdS quantum dots, both of which can be simultaneously detected by anodic stripping voltammetry. Consequently, Neu5Gc and Neu5Ac on cell surface can be quantitatively analyzed with the lowest detection limits of 1.12 cells/mL and 1.25 cells/mL, respectively. Therefore, a ratiometric electrochemical method can be constructed for kinetic study of the expression and hydrolysis of Neu5Gc and Neu5Ac on cell surface, which can be further used as a tool to identify bladder cancer cells at different development stages. Our method to evaluate tumor development is simple and easy to be operated, so it can be potentially applied for the detection of tumor occurrence and development in the future

Multilocus Sequence Typing and Further Genetic Characterization of the Enigmatic Pathogen, <i>Staphylococcus hominis</i>

<div><p><i>Staphylococcus hominis</i> is a commensal resident of human skin and an opportunistic pathogen. The species is subdivided into two subspecies, <i>S. hominis</i> subsp. <i>hominis</i> and <i>S. hominis</i> subsp. <i>novobiosepticus</i>, which are difficult to distinguish. To investigate the evolution and epidemiology of <i>S. hominis</i>, a total of 108 isolates collected from 10 countries over 40 years were characterized by classical phenotypic methods and genetic methods. One nonsynonymous mutation in <i>gyrB</i>, scored with a novel SNP typing assay, had a perfect association with the novobiocin-resistant phenotype. A multilocus sequence typing (MLST) scheme was developed from six housekeeping gene fragments, and revealed relatively high levels of genetic diversity and a significant impact of recombination on <i>S. hominis</i> population structure. Among the 40 sequence types (STs) identified by MLST, three STs (ST2, ST16 and ST23) were <i>S. hominis</i> subsp. <i>novobiosepticus</i>, and they distinguished between isolates from different outbreaks, whereas 37 other STs were <i>S. hominis</i> subsp. <i>hominis</i>, one of which was widely disseminated (ST1). A modified PCR assay was developed to detect the presence of <i>ccrAB4</i> from the SCC<i>mec</i> genetic element. <i>S. hominis</i> subsp. <i>novobiosepticus</i> isolates were oxacillin-resistant and carriers of specific components of SCC<i>mec</i> (<i>mecA</i> class A, <i>ccrAB3</i>, <i>ccrAB4</i>, <i>ccrC</i>), whereas <i>S. hominis</i> subsp. <i>hominis</i> included both oxacillin-sensitive and -resistant isolates and a more diverse array of SCC<i>mec</i> components. Surprisingly, phylogenetic analyses indicated that <i>S. hominis</i> subsp. <i>novobiosepticus</i> may be a polyphyletic and, hence, artificial taxon. In summary, these results revealed the genetic diversity of <i>S. hominis</i>, the identities of outbreak-causing clones, and the evolutionary relationships between subspecies and clones. The pathogenic lifestyle attributed to <i>S. hominis</i> subsp. <i>novobiosepticus</i> may have originated on more than one occasion.</p></div

Phenotypic and genetic characteristics of <i>S. hominis</i> subspecies.

a<p>SHN is S. hominis subsp. novobiosepticus, SHH is S. hominis subsp. Hominis.</p