Abstract

BackgroundMethicillin-resistant Staphylococcus aureus (MRSA) is an important pathogen for human infection. Hospital-acquired (HA) and community-acquired (CA) MRSA infections are serious clinical problems worldwide. In this study, we selected typical HA-MRSA strain and CA-MRSA isolates from our previous research and compared their phenotypic and pathogenic abilities both in vitro and in vivo.ResultsST59-t437-SCCmecIVa (YNSA7) and ST59-t437-SCCmecVb (YNSA53) belonged to two prevalent subclones of CA-MRSA, while ST239-t030-SCCmecIII (YNSA163) was an HA-MRSA epidemic clone in Southwest China. ST59-t437 strains demonstrated faster growth ability, higher survival rate resistance to human blood, and more toxin secretion levels and cytotoxicity than ST239-t030. The virulence and regulatory genes of hld, psm-α, RNAIII, agrA, and crtN were highly expressed on CA-MRSA isolates, especially the ST59-t437-SCCmecIVa subclone. However, the ST239-t030 strain had the strongest adhesion and biofilm ability among these MRSA bacteria. Animal experiments revealed the most serious lethal effect on BALB/c mice caused by the YNSA7 strain infection. The survival rates of BALB/c mice infected with the three MRSA strains were 16.7, 50.0 and 100.0% for YNSA7, YNSA53 and YNSA163, respectively. Histopathological analyses of infected animals indicated that the lungs were the most seriously damaged organs, especially for ST59-t437 MRSA. Severe inflammatory reactions, tissue destruction, and massive exudation of inflammatory mediators and cells could be identified in ST59-t437 strain-infected animals.ConclusionsIn general, ST59-t437 strains showed higher pathogenic ability than the ST239-t030 isolate, while ST239-t030 MRSA revealed the features prevalent in hospital settings, specifically for adhesion and biofilm ability.

Highlights

  • Methicillin-resistant Staphylococcus aureus (MRSA) is an important pathogen for human infection

  • Since 1959, different MRSA clones have emerged in different regions, and the most frequently reported clones are clonal complexes (CCs) 5, CC8, CC22, CC30 and CC45 [9]

  • The most prevalent clone of CA-MRSA in Asia is ST59, it is not the epidemic clone in other parts of the world [4]

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Summary

Introduction

Methicillin-resistant Staphylococcus aureus (MRSA) is an important pathogen for human infection. Hospital-acquired (HA) and community-acquired (CA) MRSA infections are serious clinical problems worldwide. The incidence of methicillin-resistant Staphylococcus aureus (MRSA) has increased globally [1]; MRSA has become the most important pathogen of hospitalacquired (HA) or community-acquired (CA) infections. MLST (ST type) is suitable for analysing the evolutionary relationship and clonal complexes of strains. Since 1959, different MRSA clones have emerged in different regions, and the most frequently reported clones are clonal complexes (CCs) 5, CC8, CC22, CC30 and CC45 [9]. The most prevalent clone of CA-MRSA in Asia is ST59, it is not the epidemic clone in other parts of the world [4]

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