Increased Community-Associated Infections Caused by Panton-Valentine Leukocidin-Negative MRSA, Shanghai, 2005-2014.

During 2005-2014, community-associated methicillin-resistant Staphylococcus aureus infections increased in Shanghai, China. Most infections were caused by sequence type 59 S. aureus that lacked Panton-Valentine leukocidin. This finding challenges the notion that Panton-Valentine leukocidin is necessary for epidemiologic success of community-associated methicillin-resistant S. aureus.

Targeting surface protein SasX by active and passive vaccination to reduce Staphylococcus aureus colonization and infection.

SasX is a recently described surface protein of Staphylococcus aureus that is linked to the epidemic success of hospital-associated methicillin-resistant clones, in particular in Asia. It enhances nasal colonization and virulence in skin and lung infection models. Here, we evaluated the potential of SasX as a vaccine component in passive and active immunization efforts using mouse infection models. We found that SasX induced a specific immune response predominantly based on IgG1 antibodies. Active immunization with recombinant SasX or passive immunization with rabbit polyclonal anti-SasX IgG significantly decreased the size of lesions caused by S. aureus in a skin infection model. Furthermore, active immunization reduced acute lung injury in a lung infection model. Moreover, active or passive immunization significantly reduced S. aureus colonization in a nasal colonization model. Finally, anti-SasX IgG enhanced the susceptibility of S. aureus to killing by human neutrophils. We conclude that SasX is a potential target for therapeutics or vaccines designed to moderate colonization and infection by sasX-positive epidemic strains of S. aureus.

In-depth mapping carboxylic acid metabolome reveals the potential biomarkers in colorectal cancer through characteristic fragment ions and metabolic flux.

Carboxylic acid metabolome plays vital roles in the study of pathological mechanisms about cancer. This study aimed to find potential biomarkers for colorectal cancer (CRC) using carboxylic acids profiling. However, the identification of much more carboxylic acids was limited due to poor ionization efficiency and lack of characteristic fragment ions. Derivatization-liquid chromatography-mass spectrometry, which contains characteristic MS/MS fragments ions, were performed for carboxylic acid metabolomics analysis in CRC serum samples. 1054 carboxylic acids were quickly and selectively identified after extraction using three characteristic fragment ions and elucidation using the most suitable CE at 30 eV. Among them, 605 carboxylic acids exhibit discriminating levels between healthy and CRC patients in training cohort. Furthermore, the differential metabolites were found to be mainly enriched in amino acid metabolism, fatty acid biosynthesis and TCA cycle by MetaboAnalyst and iPath analysis. Finally, serine, glycine, and methionine were determined as the potential biomarkers after further confirmation using validation cohort and in vitro metabolic flux analysis. The above results collectively demonstrated that a new set of carboxylic acids can be quickly and selectively discovered using characteristic fragment ions.

Development of a Sensitive Escherichia coli Bioreporter Without Antibiotic Markers for Detecting Bioavailable Copper in Water Environments.

The whole-cell bioreporters based on the cop-operon sensing elements have been proven specifically useful in the assessment of bioavailable copper ions in water environments. In this study, a series of experiments was conducted to further improve the sensitivity and robustness of bioreporters. First, an Escherichia coli △copA△cueO△cusA mutant with three copper transport genes knocked out was constructed. Then, the copAp::gfpmut2 sensing element was inserted into the chromosome of E. coli △copA△cueO△cusA by gene knock-in method to obtain the bioreporter strain E. coli WMC-007. In optimized assay conditions, the linear detection range of Cu2+ was 0.025-5 mg/L (0.39-78.68 µM) after incubating E. coli WMC-007 in Luria-Bertani medium for 5 h. The limit of detection of Cu2+ was 0.0157 mg/L (0.25 µM). Moreover, fluorescence spectrometry and flow cytometry experiments showed more environmental robustness and lower background fluorescence signal than those of the sensor element based on plasmids. In addition, we found that the expression of GFPmut2 in E. coli WMC-007 was induced by free copper ions, rather than complex-bound copper, in a dose-dependent manner. Particularly, the addition of 40 mM 3-(N-Morpholino)propanesulfonic acid buffer to E. coli WMC-007 culture enabled accurate quantification of bioavailable copper content in aqueous solution samples within a pH range from 0.87 to 12.84. The copper recovery rate was about 95.88-113.40%. These results demonstrate potential applications of E. coli WMC-007 as a bioreporter to monitor copper contamination in acidic mine drainage, industrial wastewater, and drinking water. Since whole-cell bioreporters are relatively inexpensive and easy to operate, the combination of this method with other physicochemical techniques will in turn provide more specific information on the degree of toxicity in water environments.

Staphylococcal Protein A Promotes Colonization and Immune Evasion of the Epidemic Healthcare-Associated MRSA ST239.

The highly successful epidemic of healthcare-associated methicillin-resistant Staphylococcus aureus (HA-MRSA) ST239 is a growing concern worldwide, due to its progressive adaptation to the highly selective environment of the healthcare system. HA-MRSA ST239 display the reduced virulence and successfully colonize in hospital settings, while the emergent community-associated MRSA (CA-MRSA) maintain full virulence and cause infections in the community environment. Our aim was to investigate what enables S. aureus ST239 to be highly adaptive under hospital circumstances and gradually progress to a series of widespread invasive infections. We found that spa expression of HA-MRSA ST239 is much higher than that of CA-SA ST398. And we discovered that the highly production of staphylococcal protein A (SpA), having no concern with spa gene structure, enhances nasal colonization and cell adhesion in ST239. S. aureus ST239 defends against the adaptive immune response by resisting phagocytosis and inducing apoptosis of B cells through expression of surface-anchored and released protein A, facilitating its dissemination within the circulatory system to other organs. Protein A also plays another key role in subverting the host immune response through its ability to induce early shedding of TNF-α receptor 1 (TNFR1) from phagocytic cells. The increased levels of soluble TNFR1 present during experimental S. aureus ST239 infection may neutralize circulating TNF-α and impair the host inflammatory response. Protein A is also a virulence factor, as tested in our bacteremia model in mice, contributing to the durative tissue damage of abscess formation sites in ST239 infection. These functions of protein A eventually benefit to widespread infections of S. aureus ST239. We draw the conclusion that Staphylococcal Protein A may be a crucial determinant in the colonization and immune evasion of ST239 infections, contributing to persistent spread in the hospital settings. These results suggest that antibodies against protein A may provide insights into the development of novel treatments against S. aureus, especially HA-MRSA.

SNF2H promotes hepatocellular carcinoma proliferation by activating the Wnt/ß-catenin signaling pathway.

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide and has an extremely poor prognosis. Surgical resection is always inapplicable to HCC patients diagnosed at an advanced tumor stage. The mechanisms underlying HCC cell proliferation remain obscure. In the present study, SWItch/sucrose nonfermentable catalytic subunit SNF2 (SNF2H) expression was tested in HCC tissues and Wnt/ß-catenin pathway activation upon overexpression of SNF2H or knockdown of SNF2H expression was investigated in cultured HCC cells. It was demonstrated that SNF2H is a vital factor for HCC growth. The SNF2H expression level is increased in HCC tissues compared with paratumoral liver tissues. SNF2H promotes HCC cell proliferation and colony formation ability in vitro. SNF2H may increase the protein level of ß-catenin and enhance its nuclear accumulation in HCC cells, thereby leading to the activation of the Wnt/ß-catenin signaling pathway. In conclusion, the present results indicate that SNF2H plays a vital role in HCC cell growth, suggesting that SNF2H may be a promising therapeutic target for HCC treatment.

Virulence determinants associated with the Asian community-associated methicillin-resistant Staphylococcus aureus lineage ST59.

Understanding virulence is vital for the development of novel therapeutics to target infections with community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA), which cause an ongoing epidemic in the United States and are on a global rise. However, what defines virulence particularly of global CA-MRSA lineages is poorly understood. Threatening a vast population, the predominant Asian CA-MRSA lineage ST59 is of major epidemiological importance. However, there have been no molecular analyses using defined virulence gene deletion mutants in that lineage as of yet. Here, we compared virulence in skin, lung, and blood infection models of ST59 CA-MRSA isolates with geographically matched hospital-associated MRSA isolates. We selected a representative ST59 CA-MRSA isolate based on toxin expression and virulence characteristics, and produced isogenic gene deletion mutants of important CA-MRSA virulence determinants (α-toxin, PSM α, Agr) in that isolate for in-vitro and in-vivo analyses. Our results demonstrate strongly enhanced virulence of ST59 CA-MRSA over hospital-associated lineages, supporting the notion that enhanced virulence is characteristic for CA-MRSA. Furthermore, they show strong and significant contribution of Agr, α-toxin, and PSMα to pathogenesis of ST59 CA-MRSA skin, lung, and blood infection, emphasizing the value of drug development efforts targeted toward those virulence determinants.