ABSTRACT
INTRODUCTION: Although therapeutic agents for methicillin-resistant Staphylococcus aureus (MRSA) are clinically available, MRSA infection is still a life-threatening disease. Bacterial attachment and biofilm formation contribute significantly to the initiation of MRSA infection. Controlling MRSA's attachment and biofilm formation might reduce the frequency of MRSA infection. According to recent data, some amino acids can reduce MRSA's attachment on plates; however, their precise inhibitory mechanisms remain unclear. Therefore, we explored the effect of the amino acids on bacterial adhesion and biofilm formation in vitro and in vivo MRSA infection models. METHODS: We tested the inhibitory effect of amino acids on MRSA and Escherichia coli (E. coli) in the attachment assay. Moreover, we evaluated the therapeutic potential of amino acids on the in vivo catheter infection model. RESULTS: Among the amino acids, D-Serine (D-Ser) was found to reduce MRSA's ability to attach on plate assay. The proliferation of MRSA was not affected by the addition of D-Ser; thus, D-Ser likely only played a role in preventing attachment and biofilm formation. Then, we analyzed the expression of genes related to attachment and biofilm formation. D-Ser was found to reduce the expressions of AgrA, SarS, IcaA, DltD, and SdrD. Moreover, the polyvinyl chloride catheters treated with D-Ser had fewer MRSA colonies. D-Ser treatment also reduced the severity of infection in the catheter-induced peritonitis model. Moreover, D-Ser reduced the attachment ability of E. coli. CONCLUSION: D-Ser inhibits the attachment and biofilm formation of MRSA by reducing the expression of the related genes. Also, the administration of D-Ser reduces the severity of catheter infection in the mouse model. Therefore, D-Ser may be a promising therapeutic option for MRSA as well as E. coli infection.
Subject(s)
Bacterial Adhesion/drug effects , Biofilms/drug effects , Methicillin-Resistant Staphylococcus aureus/physiology , Serine/pharmacology , Animals , Catheters/microbiology , Disease Models, Animal , Down-Regulation/drug effects , Down-Regulation/genetics , Gene Expression Regulation, Bacterial/drug effects , Methicillin-Resistant Staphylococcus aureus/drug effects , Methicillin-Resistant Staphylococcus aureus/genetics , Mice, Inbred BALB C , Peritonitis/microbiology , Peritonitis/pathology , Polyvinyl ChlorideABSTRACT
Methicillin-resistant Staphylococcus aureus (MRSA) causes severe infectious diseases and can be life-threatening in healthcare-settings. MRSA is classified into health-care associated (HA)-MRSA strains and community acquired (CA)-MRSA strains based on genotype and phenotype. CA-MRSA has been reported to show the lower minimal inhibitory concentration (MIC) of some antibiotics as compared to HA-MRSA. Recently, the prevalence of CA-MRSA has been increased in worldwide. CA-MRSA is isolated not only from the healthy individuals in a community but also from the patients in healthcare settings. However, the changing trend in frequency of HA-MRSA and CA-MRSA in the hospital setting is not clear. Therefore, we analyzed the trend of MIC to speculate the frequency of HA-MRSA and CA-MRSA in the facility. Moreover, gene mutations were evaluated on resistant gene loci with next generation sequencer. The frequency of strains with low MIC of beta-lactam antibiotics was gradually increased in isolated MRSA strains from the hospitalized patients. Whole genome analysis revealed the frequency of gene mutation was also decreased in some resistant loci, such as blaZ and blaR1. These findings highlight the changing trend of MRSA strains isolated from hospitalized patients.
Subject(s)
Bacterial Proteins/genetics , Drug Resistance, Multiple, Bacterial/genetics , Methicillin-Resistant Staphylococcus aureus/isolation & purification , beta-Lactamases/genetics , beta-Lactams/pharmacology , Anti-Bacterial Agents/pharmacology , Community-Acquired Infections/diagnosis , Community-Acquired Infections/microbiology , Cross Infection/diagnosis , Cross Infection/microbiology , DNA, Bacterial , Female , Genotype , Humans , Japan , Male , Microbial Sensitivity Tests/trends , Middle Aged , Mutation , Prevalence , Protein Structure, Tertiary/genetics , Staphylococcal Infections/diagnosis , Whole Genome SequencingABSTRACT
OBJECTIVES: Methicillin-resistant Staphylococcus aureus (MRSA) causes hospital- and community-acquired infections. It is not clear whether genetic characteristics of the bacteria contribute to disease pathogenesis in MRSA infection. We hypothesized that whole genome analysis of MRSA strains could reveal the key gene loci and/or the gene mutations that affect clinical manifestations of MRSA infection. METHODS: Whole genome sequences (WGS) of MRSA of 154 strains were analyzed with respect to clinical manifestations and data. Further, we evaluated the association between clinical manifestations in MRSA infection and genomic information. RESULTS: WGS revealed gene mutations that correlated with clinical manifestations of MRSA infection. Moreover, 12 mutations were selected as important mutations by Random Forest analysis. Cluster analysis revealed strains associated with a high frequency of bloodstream infection (BSI). Twenty seven out of 34 strains in this cluster caused BSI. These strains were all positive for collagen adhesion gene (cna) and have mutations in the locus, those were selected by Random Forest analysis. Univariate and multivariate analysis revealed that these gene mutations were the predictor for the incidence of BSI. Interestingly, mutant CNA protein showed lower attachment ability to collagen, suggesting that the mutant protein might contribute to the dissemination of bacteria. CONCLUSIONS: These findings suggest that the bacterial genotype affects the clinical characteristics of MRSA infection.
