Project description:A scarlet fever outbreak occurred in Hong Kong in 2011. The majority of cases resulted in the isolation of Streptococcus pyogenes emm12 with multiple antibiotic resistances. Phylogenetic analysis of 22 emm12 scarlet fever outbreak isolates, 7 temporally and geographically matched emm12 non-scarlet fever isolates, and 18 emm12 strains isolated during 2005-2010 indicated the outbreak was multiclonal. Genome sequencing of 2 nonclonal scarlet fever isolates (HKU16 and HKU30), coupled with diagnostic polymerase chain reaction assays, identified 2 mobile genetic elements distributed across the major lineages: a 64.9-kb integrative and conjugative element encoding tetracycline and macrolide resistance and a 46.4-kb prophage encoding superantigens SSA and SpeC and the DNase Spd1. Phenotypic comparison of HKU16 and HKU30 with the S. pyogenes M1T1 strain 5448 revealed that HKU16 displays increased adherence to HEp-2 human epithelial cells, whereas HKU16, HKU30, and 5448 exhibit equivalent resistance to neutrophils and virulence in a humanized plasminogen murine model. However, in contrast to M1T1, the virulence of HKU16 and HKU30 was not associated with covRS mutation. The multiclonal nature of the emm12 scarlet fever isolates suggests that factors such as mobile genetic elements, environmental factors, and host immune status may have contributed to the 2011 scarlet fever outbreak.
Project description:The project aim is to evaluate the role of whole-genome aCGH for prenatal diagnosis in Hong Kong. Array CGH was performed on 220 samples recruited prospectively as the first-tier test study; and on 150 samples with abnormal ultrasound findings and normal karyotypes as a further-test study using NimbleGen CGX-135K oligonucleotide arrays. After the exclusion of common aneuploidies in the first-tier study, clinically significant CNVs are detected in 23/220 samples. In the further test study, clinically significant CNVs are detected in 9/150 samples, which showed CGX array has an increased diagnostic yield of about 6% compared with conventional cytogenetic methods. CNVs of unclear clinical significance are detected in only 10/370 (2.7%) samples. Only data from sample with positive findings are included in this experiment submission (the samples with normal results are not included here).