Objective The rapid multiplex PCR (MPCR) system for detection of genes encoding aminoglycoside resistance in Staphylococcus aureus was developed. The distribution of antibiotic resistant genes acc(6')-Ie+aph(2″), aph(3')-Ⅲa and ant(4')-Ia in Guangzhou was analyzed using the established system.Methods S. aureus strains were identified and susceptibility tests were performed using VITEK-60 or PHOENIX-100 system as recommended by the manufacturer. Aminoglycoside resistance was determined by disk diffusion method. MPCR system for detection of antibiotic resistance genes was optimized.Results The MPCR assay was established successfully. The prevalence of acc(6')-Ie+aph(2″), aph(3')-Ⅲa and ant(4')-Ia in the 124 clinical S. aureus isolates was 62.1%, 32.3% and 1.6%, respectively as analyzed by MPCR. Good correlation between antibiotic resistance phenotypes and genotypes was observed. One or more of the genes encoding aminoglycoside modifying enzymes could be detected in all gentamicin- or netilmicin- or amikacin-resistant isolates. The acc(6')-Ie+aph(2″) gene was identified in 72 of 74 mecA-positive isolates.Conclusions This MPCR system could be used for rapid and reliable analysis of the antibiotic-resistant genotypes of clinical S. aureus isolates. The gene acc(6')-Ie+aph(2″) may be the predominant determinant of aminoglycoside resistance, followed by gene aph(3')-Ⅲa. The prevalence of ant(4')-Ia gene is relatively low.

Objective To identify one umbilical blood sample with abnonnal gap-PCR products of three bands of α2,-α3.7 and-SEA.further family pedigree were analyzed for the source of genetic variations,Methods One fetal umbilical blood sample was drawn from a woman of 24-weeks pregnancy.Gap-PCR for α-thalassemia was routinely conducted and abnornlal three bands of α2.-α3.7 and-SEA were observed.which could not be interpreted according to the kit manual and suspected as rare variation.With informed consen,DNA samples from the parents and grandparents were obtained for further study.Singleplex andnested PCR techniques were utilized to analyze the molecular characteristics of DNA samples from this fetus and its parents and grand-parents.Results Hematological phenotype study showed that fetal Hb Ban's was 7.6%,and its mother and maternal grandfather were both with typical α-thalassemia.while its father,grandfather and grandmother and maternal grandmother are without abnormal hematological change.Molecular study showed that fetal blood DNA was a heterozygosity for HKaa and-SEA.its father and grandfather are both HKαα/αα,its mother and maternal grandfather are both-SEA/aa,its grandmother and maternal grandmother are with both normal alleles of αα/αα.Then after genetic counseling the fetas was saved and iS a she baby now.Conclusion ThroUgh careful molecular tests one case of prenatal heterozygosity of HKαα/-SEA was identified,and the fetus is kept successfully through careful clinical counseling.

Objective To analyze a rare genotype with β-thalassemia intermadia.Methods Phenotypic analysis was performed using routine hematological tests to measure red blood cell parameters and high performance liquid chromatography (HPLC)was used to measure hemoglobin fractions.The β-globin gene mutations were conducted using reverse-dot-blot and DNA sequencing of the breakpoint region were characterized with gap-PCR.Results The proband had a trait of thalassemia intermedia with reduced hemoglobin (86 g/L).The proband's father had a trait of microcytic hypochromic with reduced mean corpuscular volume(MCV),mean corpuscular hemoglobin (MCH) (63.7 fl and 20.4 pg,respectively) and an elevated level of HbA2.He had the phenotype of heterozygosity for β-thalassemia.The preband's mother,grandmother and sister had a trait of heterezygote for hereditary persistence of fetal hemoglobin (HPFH) with elevated level of HbF,which were 28.3%,21.1% and 33.7%,respectively.After molecular characterization of the family members,the proband was identified as a patient with β-thalassemia intermedia caused by co-existence of β-thalassemia(β41-42) and HPFH-6.The father was heterozygoas for β-thaiassemia (β41-42/βN) and the mother,grandmother and sister were all heterozygons for HPFH-6.Condusions A rare β-thalassemia intermedia case resulting from compound heterezygote of β41-42 with HPFH-6 is found.This study may provide clinical experiences for antenatal diagnosis.