Evaluation of 16SpathDB 2.0, an automated 16S rRNA gene sequence database, using 689 complete bacterial genomes.

Interpretation of 16S rRNA sequences is a difficult problem faced by clinical microbiologists and technicians. In this study, we evaluated the updated 16SpathDB 2.0 database, using 689 16S rRNA sequences from 689 complete genomes of medically important bacteria. Among these 689 16S rRNA sequences, none was wrongly identified, with 35.8% reported as a single bacterial species having >98% identity with the query sequence (category 1), 63.9% reported as more than 1 bacterial species having >98% identity with the query sequence (category 2), 0.3% reported to the genus level (category 3), and none reported as no match (category 4). For the 16S rRNA sequences of non-duplicated bacterial species reported as category 1 or 2, the percentage of bacterial species reported as category 1 was significantly higher for anaerobic Gram-positive/Gram-negative bacteria than aerobic/facultative anaerobic Gram-positive/Gram-negative bacteria. 16SpathDB 2.0 is a user-friendly and accurate database for 16S rRNA sequence interpretation in clinical laboratories.

Molecular characterization of the 2011 Hong Kong scarlet fever outbreak.

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.