Mechanisms underlying the resistance of Candida albicans to echinocandin antifungals / 中华皮肤科杂志

With the application of echinocandin antifungals, more and more resistant Candida albicans strains have been detected. It has been reported that mechanisms underlying the resistance of Candida albicans to echinocandin antifungals mainly involve FKS, MSH2 and ERG3 gene mutations, biofilm formation, cellular stress response, compensatory increases in chitin, sphingolipid synthesis, etc. This review focuses on echinocandin resistance-related genes and underlying mechanisms in Candida albicans, which will help to overcome and prevent echinocandin resistance in clinical practice, and explore new therapeutic targets and drugs for Candida albicans infection.

Mutations in BRCA1, BRCA2 and other breast and ovarian cancer susceptibility genes in Central and South American populations

Breast cancer (BC) is the most common malignancy among women worldwide. A major advance in the understanding of the genetic etiology of BC was the discovery of BRCA1 and BRCA2 (BRCA1/2) genes, which are considered high-penetrance BC genes. In non-carriers of BRCA1/2 mutations, disease susceptibility may be explained of a small number of mutations in BRCA1/2 and a much higher proportion of mutations in ethnicity-specific moderate- and/or low-penetrance genes. In Central and South American populations, studied have focused on analyzing the distribution and prevalence of BRCA1/2 mutations and other susceptibility genes that are scarce in Latin America as compared to North America, Europe, Australia, and Israel. Thus, the aim of this review is to present the current state of knowledge regarding pathogenic BRCA variants and other BC susceptibility genes. We conducted a comprehensive review of 47 studies from 12 countries in Central and South America published between 2002 and 2017 reporting the prevalence and/or spectrum of mutations and pathogenic variants in BRCA1/2 and other BC susceptibility genes. The studies on BRCA1/2 mutations screened a total of 5956 individuals, and studies on susceptibility genes analyzed a combined sample size of 11,578 individuals. To date, a total of 190 different BRCA1/2 pathogenic mutations in Central and South American populations have been reported in the literature. Pathogenic mutations or variants that increase BC risk have been reported in the following genes or genomic regions: ATM, BARD1, CHECK2, FGFR2, GSTM1, MAP3K1, MTHFR, PALB2, RAD51, TOX3, TP53, XRCC1, and 2q35.

Clinical significance of cytogenetic monitoring in chronic myeloid leukemia / 中华血液学杂志

Objective@#To analyze the association of cytogenetic abnormalities with the prognosis of chronic myeloid leukemia (CML) patients in tyrosine kinase inhibitors (TKI) era.@*Methods@#Karyotype analysis of chromosome G-banding was carried out in 387 newly diagnosed CML patients by short-term culture of bone marrow cells. The correlation of cytogenetic abnormalities and CML progression was explored in combination with ABL tyrosine point mutations.@*Result@#Of 387 patients with positive BCR-ABL fusion gene assayed by fluorescence in situ hybridization (FISH) technique, 94.1% (364/387) patients were Ph positive and 5.9% (23/387) Ph negative; 320 patients (87.9%) had a translocation t (9;22) (q34;q11) and 5 (1.4%) a variant translocation t (v;22) . Additional cytogenetic aberrations (ACA) at diagnosis were found in 10.7% (39/387) Ph+ patients, major route ACA in 22 (56.4%) cases and minor route ACA in 15 (38.5%) cases and 2 patients (5.1%) lacked the Y chromosome (−Y) ; 23.4% (71/303) patients occurred ACA during TKI treatment and the most frequent abnormalities were abnormal chromosome numbersd, which were likely associated with high proportion of disease progression (χ2=168.21, P<0.001) and ABL tyrosine point mutations (χ2=29.04, P<0.001) . Newly diagnosed CML-CP patients with t (9;22) (q34;q11) had a longer event-free survival (EFS) and disease-free survival (DFS) rates than that of patients with ACA (P=0.037; P=0.003) , while the overall survival (OS) had no significant differences (P=0.209) . As for CML-CP patients that occurred ACA during TKI therapy would have a marked low OS, EFS and DFS (all P<0.001) compared with no ACA occurred patients. Survival of advanced patients that occurred ACA were dramatically reduced.@*Conclusion@#ACA often emerged during the disease progress in CML patients, regular and timely detection of chromosomes karyotype and ABL tyrosine point mutations during TKI treatment was important for therapeutic evaluation, progress and prognosis of CML.

Study on the relationship between erythromyc in sensitivity and drug-resistance gene in Mycoplasma pneumoniae / 国际检验医学杂志

Objective To study the relationship between erythromycin sensitivity and drug-resistance gene in Mycoplasma pneu-moniae(Mp).Methods In 46 erythromycin-resistant MP clinical isolates,domain Ⅴ of 23S rRNA was amplified by polymerase chain reaction(PCR),followed by direct automatic sequencing method.The DNA sequences were compared to find molecular mecha-nisms of drug resistance.Results Among the 46 erythromycin-resistant Mp clinical isolates,44(95.65%)harbored an A-to-G tran-sition mutation at position 2063 in the 23S rRNA gene and 2(4.35%)harbored an A-to-G transition mutation at position 2064,but no A-to-C transition mutation at position 2063 and C-to-G/A transition mutation at position 2617 were detected.Conclusion E-rythromycin-resistant of Mp clinical isolates were closely related to A-to-G transition mutation at position 2063/2064 in domain Ⅴof 23S rRNA genes and the most important was the A2063G transition mutation.Rapid and accurate identification of the genetic mutations in domain Ⅴ of 23S rRNA may be help to diagnose the infection of Mycoplasma pneumoniae,provide the drug-resistant information,and instruct the application of antibiotics reasonably and effectively.

Report of rpoB mutation in clinically suspected cases of drug resistant leprosy: A study from Eastern India.

Background: The current strategy for leprosy control depends mainly on early case detection and providing the recommended multidrug therapy (MDT) dosage. Understanding the molecular mechanisms of drug resistance to each of these drugs is essential in providing effective treatment and preventing the spread of resistant strains in the community. The progress of molecular biology research provides a very effi cient opportunity for the diagnosis of drug resistance by in vitro method. Aim: We aimed to investigate the point mutations within the rpoB gene region of the Mycobacterium leprae genome, which are responsible for resistance to rifampicin, in order to determine the emergence of drug resistance in leprosy in the Kolkata region of West Bengal. Methods: A total of 50 patients with a relapse of leprosy were enrolled in the study. Skin smears were obtained for estimation of bacillary index and biopsies were obtained in 70% alcohol for extraction of DNA. The extracted DNA was amplifi ed by M. leprae-polymerase chain reaction (PCR) targeting rpoB gene region. Every single nucleotide base in the sequence is aligned to reference sequence and identity gaps were determined by NCBI – BLAST. Later in-silico analysis was done to identify the changes in the translated protein sequences. Results: A mutation at the base pair position 2275405 where G is replaced by C in the M. leprae genome, which corresponds to the coding region of rpoB gene (279 bp – 2275228 to2275506), was observed in two patients. This missense mutation in CAC codon brings about a glutamic acid to histidine change in the amino acid sequence of RNA polymerase beta subunit at the position 442 (Glu442His), a region specifi c for rifampicin interaction, which might be responsible for unresponsiveness to rifampicin by manifesting a stable bacteriological index in these 2 patients even after completion of 24 months of multibacillary multi-drug therapy (MB-MDT). Limitations: The major limitations of multipleprimer PCR amplifi cation refractory mutation system (MARS) assay is that it capable of detecting mutation at codon 425 and cannot distinguish any silent amino acid changes. Conclusion: The study indicates the existence of rifampicin drug resistance in Eastern India.

Mutaciones puntuales en el gen de la dihidropteroato sintetasa de Plasmodium falciparum en Bolívar, Colombia / Point mutations in the dihydropteroate synthetase gene of Plasmodium falciparum in Bolivar, Colombia

Introducción: la resistencia antimalárica dificulta el control del paludismo en Colombia. La vigilancia molecular de mutaciones puntuales en blancos terapéuticos es fundamental en el estudio de la resistencia a los antimaláricos. Objetivo: identificar mutaciones puntuales en el gen de la dihidropteroato sintetasa de Plasmodium falciparum (pfdhps), asociadas con resistencia in vitro a sulfadoxina. Métodos: la fuente de ADN de Plasmodium falciparum consistió en láminas de gota gruesa de 55 individuos con infección malárica, reportados en el departamento de Bolívar, Colombia. El ADN se extrajo con solución de Chelex-100 al 5 %. Las mutaciones se identificaron mediante PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) y secuenciación. Resultados: 17 muestras (31 %) amplificaron un fragmento de 438 pb de pfdhps. La PCR-RFLP mostró frecuencia del genotipo mutante G-437 en 65 % de los amplificados, el mixto A/G-437 en 29 % y el silvestre A-437 en 6 %. Los alelos mutantes G-437, F-436 y el alelo silvestre K-540 se identificaron en todas las muestras secuenciadas. Conclusiones: este es el primer reporte de mutaciones puntuales en el gen dhps de Plasmodium falciparum en el departamento de Bolívar, Colombia, lo cual contribuye al conocimiento de la resistencia a los antimaláricos en el Caribe colombiano.

Introduction: antimalarial drug resistance hinders the control of malaria in Colombia. The molecular surveillance of point mutations in therapeutic targets is essential in the study of antimalarial drugs. Objective: to identify point mutations at dihydropteroate synthetase gene of Plasmodium falciparum (pfdhps) associated with sulfadoxine resistance. Methods: source of P. falciparum DNA was blood thick smears of 55 individuals with malaria infection, reported in Bolivar, Colombia. The DNA was extracted with 5 %. Chelex-100 solution. The mutations were identified by PCR-RFLP and sequencing. Results: seventeen samples (31 %) amplified a 438 bp fragment of pfdhps. The PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) showed a frequency of mutant genotype (G-437) in 65 % of amplicons, mixed genotype (A/G-437) in 29 % and wild genotype (A/G-437) in 6 %. The mutant alleles G-437, F-436 and the wild allele K-540 were identified in all sequenced samples. Conclusions: this is the first report of point mutations in the P. falciparum dhps gene in Bolivar, Colombia. This result contributes to the knowledge of antimalarial drug resistance in the Colombian Caribbean region.

Molecular Mechanisms of Macrolide Resistance of Mycoplasma pneumoniae / 中华医院感染学杂志

OBJECTIVE To investigate macrolide resistance and main molecular mechanisms in Mycoplasma pneumoniae. METHODS Thirty two throat swabs from children infected with M. pneumoniae were cultured by modified Hayflick medium. Antibiotic susceptibility test was used to screen the macrolide-resistant M. pneumoniae. The 23S rRNA gene sequences of the strains were determined with polymerase chain reaction and sequencing. RESULTS Nineteen strains were isolated from 32 throat swabs successfully.Fifteen strains were resistant to macrolide antibiotics according to the results of antibiotic susceptibility test. Once the strain was resistant to one of macrolide antibiotics,it would be resistant to the others. Sequencing results of the sensitive strains and the standard strain FH were completely same. Fifteen resistant strains presented A2063G point mutation in 23 SrRNA region Ⅴ, in which 2 examples showed the coexistence of the sensitive strain and the resistant strain. CONCLUSIONS Macrolide-resistant M. pneumoniae is common and serious at present. The antibiotic resistant isolate carries point mutations of the 23S rRNA region Ⅴ.