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Methicillin-resistant Staphylococcus aureus (MRSA) has become the most important pathogen of hospital-acquired (HA) or community-acquired (CA) infections. However, it is unclear of the cytokines responsible for pathological hyper-inflammation in sepsis related cytokine storm for MRSA infection. In this study, we selected typical HA-MRSA strain (YNSA163: ST239-t030-SCCmecⅢ) and two CA-MRSA isolates (YNSA7: ST59-t439-SCCmecⅣa and YNSA53: ST59-t437-SCCmecⅤb) from our previous research, infected on BALB/c mice, and analyzed the cytokine storm patterns during infection process. The animal experiments revealed the most serious lethal effect on BALB/c mice caused by YNSA7 strain infection, followed by YNSA53, and no BALB/c mice died for YNSA163 infection. Histopathological analyses revealed that lung was the most seriously damaged organs, followed by spleen and kidney, especially for CA-MRSA infection. The severe inflammatory reactions, tissue destruction, and massive exudation of inflammatory mediators and cells could be identified in CA-MRSA strains infected mice. Interleukin-6 (IL-6) and IL-10 were both highly expressed in spleen and lung of YNSA7 and YNSA53 dead cases compared with YNSA53 survived and YNSA163 cases, which demonstrated cytokine storm pattern for CA-MRSA strains infection. The results of IL-6 intervention experiment verified that the enhanced IL-6 secretion was responsible for the host lethality of YNSA7 infection. RNA-sequencing results among three MRSA isolates indicated most of the differentially expressed genes referred to cellular process, metabolism and genetic information processing of bacteria. Specifically, clpP, chp chemotaxis inhibit, fnbB, pathogencity island protein and virulence associated protein E were highly expressed in YNSA7 strain. In general, CA-MRSA strains provoked cytokine storm on BALB/c mice led to severe infection and lethality, the up-regulated of some virulence genes might play important role in pathogenesis., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Background: 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. 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., Results: ST59-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., Conclusions: In 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., (© 2021. The Author(s).)

Background: Currently, Staphylococcus aureus is one of the most important pathogens worldwide, especially for methicillin-resistant S. aureus (MRSA) infection. However, few reports referred to patients' MRSA infections in Yunnan province, southwest China., Methods: In this study, we selected representative MRSA strains from patients' systemic surveillance in Yunnan province of China, performed the genomic sequencing and compared their features, together with some food derived strains., Results: Among sixty selective isolates, forty strains were isolated from patients, and twenty isolated from food. Among the patients' strains, sixteen were recognized as community-acquired (CA), compared with 24 for hospital-acquired (HA). ST6-t701, ST59-t437 and ST239-t030 were the three major genotype profiles. ST6-t701 was predominated in food strains, while ST59-t437 and ST239-t030 were the primary clones in patients. The clinical features between CA and HA-MRSA of patients were statistical different. Compared the antibiotic resistant results between patients and food indicated that higher antibiotic resistant rates were found in patients' strains. Totally, the average genome sizes of 60 isolates were 2.79 ± 0.05 Mbp, with GC content 33% and 84.50 ± 0.20% of coding rate. The core genomes of these isolates were 1593 genes. Phylogenetic analysis based on pan-genome and SNP of strains showed that five clustering groups were generated. Clustering ST239-t030 contained all the HA-MRSA cases in this study; clustering ST6-t701 referred to food and CA-MRSA infections in community; clustering ST59-t437 showed the heterogeneity for provoking different clinical diseases in both community and hospital. Phylogenetic tree, incorporating 24 isolates from different regions, indicated ST239-t030 strains in this study were more closely related to T0131 isolate from Tianjin, China, belonged to 'Turkish clade' from Eastern Europe; two groups of ST59-t437 clones of MRSA in Yunnan province were generated, belonged to the 'Asian-Pacific' clone (AP) and 'Taiwan' clone (TW) respectively., Conclusions: ST239-t030, ST59-t437 and ST6-t701 were the three major MRSA clones in Yunnan province of China. ST239-t030 clonal Yunnan isolates demonstrated the local endemic of clone establishment for a number of years, whereas ST59-t437 strains revealed the multi-origins of this clone. In general, genomic study on epidemic clones of MRSA in southwest China provided the features and evolution of this pathogen.

Background: Staphylococcal food poisoning (SFP) is one of the most common food-borne diseases in the world. Pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST) and spa typing methods were used to characterize Staphylococcus aureus isolates from food surveillance during 2013–2015 in southwest China, and Staphylococcal cassette chromosome mec (SCCmec) typing was used for methicillin-resistant S. aureus (MRSA). Isolates were also examined for their antibiotic resistance and carriage of virulence genes. Results: Isolation rate of S. aureus was 2.60% during the three years’ surveillance and 29.50% of them were MRSA. All the S. aureus had hla genes (100%), 14.34% of the strains had tst, and 16.73% had PVL. 163 PFGE-SmaI patterns, 41 ST types and 36 spa types were obtained for all the S. aureus. Among them, ST6-t701 (13.15%), ST7-t091 (12.75%), ST59-t437 (9.96%) and ST5-t002 (7.57%) were the prevalent genotypes. Most of MRSA in this study belonged to SCCmec IV and V, accounted for 74.32% and 20.27% respectively. ST6-SCCmec IV-t701 (36.50%) was the most prevalent clone among isolates from food, followed by ST59-SCCmec V-t437 (20.30%), ST5-SCCmec IV-t002 (12.20%) and ST59-SCCmec IV-t437 (12.20%). Some strains had the identical PFGE patterns, ST and spa types with isolates from patients. Conclusions: S. aureus isolated from food in southwest China displayed heterogeneity. Isolates had the same genotype profiles with isolates from patients, indicating high homology. [ABSTRACT FROM AUTHOR]