BACKGROUND: MRSA remains endemic in Hong Kong hospitals. The epidemics of community- (CA-) and healthcare-associated (HA-) methicillin-resistant Staphylococcus aureus have been driven by a small number of lineages/clonal complexes. However, sequence-based analysis are often required to identify these lineages, before further detailed analyses with other tools such as whole genome sequencing.
OBJECTIVES:
A rapid, inexpensive method for MRSA sequence type detection was employed to update the lineages of CA- and HA-MRSA in hospitalized patients in Hong Kong hospitals.
METHODS:
Staphylococcus aureus isolates from blood and pus/tissue specimens from three of seven clusters of hospitals within the Hospital Authority hospitals were included. Over 500 isolates of MRSA strains from 2014 to 2016 have been examined. A previously validated typing assay involving multiplex PCRs based on a minimal set of ten genes that inferred 15 predominant locally prevalent ST types inc. HA-MRSA clones ST45, ST1774, ST239, and CA-MRSA clones ST30 ,ST59, ST338 were used. A binary score that corresponded to previously validated Multilocus sequence (MLST) ST types are inferred. New binary scores were further analyzed using spa-typing and conventional MLST.
RESULTS:
Of 233 MRSA bacteremic strains from 2014 - 2015, the most common MRSA inferred mPCR-ST strain type remain as ST45. Other predominant types include ST22, ST1048, ST1774, ST5. Among isolates from pus/tissue specimens, mPCR-ST types were similar to those in blood, with additional mPCR-ST types of ST30, ST398, ST772. The M-PCR assay incorporated detection of the mecA gene and of important virulence factors, such as PVL, ACME, chp genes.
CONCLUSION:
New predominant lineages of MRSA types are observed in hospitalized patients with MRSA infections. The M-PCR assay enables rapid ST type identification, and simultaneous detection of important virulence factors to facilitate rapid epidemiological typing and infection control of MRSA in hospitals.