Project description:The epidemic community-acquired methicillin-resistant S. aureus (CA-MRSA) clone USA300 has recently become a leading cause of hospital-associated bloodstream infections (BSI). Leveraging this recent introduction into hospitals and the limited genetic variation across the USA300 strains, we combined microbial comparative genomics with phenotypic analyses to discover adaptive mutations. USA300 isolates from BSI were found to have independently evolved single nucleotide variants in the transcriptional regulator sarZ. sarZ inactivation lead to altered expression of virulence factors, resulting in increased lethality in a murine model of BSI. Thus, USA300 strains can optimize their fitness in hospitals through evolution of higher virulence.
Project description:Methicillin-resistant Staphylococcus aureus is one of the major causative agents associated to infections with a high morbidity and mortality in hospitals worldwide. In previous studies, we reported that lignan 3'-demethoxy-6-O-demethylisoguaiacin isolated and characterized from Larrea tridentata showed the best activity towards methicillin-resistant S. aureus. Understanding of mechanism of action of drugs allows design drugs in a better way. Therefore, we employed microarray to obtain gene expression profile of methicillin-resistant S. aureus after exposure to 3'-demethoxy-6-O-demethylisoguaiacin. The results showed that lignan had an effect on cell membrane affecting proteins of the ATP-binding cassette (ABC) transport system causing bacteria death.
Project description:Methicillin-resistant Staphylococcus aureus is one of the major causative agents associated to infections with a high morbidity and mortality in hospitals worldwide. In previous studies, we reported that lignan 3'-demethoxy-6-O-demethylisoguaiacin isolated and characterized from Larrea tridentata showed the best activity towards methicillin-resistant S. aureus. Understanding of mechanism of action of drugs allows design drugs in a better way. Therefore, we employed microarray to obtain gene expression profile of methicillin-resistant S. aureus after exposure to 3'-demethoxy-6-O-demethylisoguaiacin. The results showed that lignan had an effect on cell membrane affecting proteins of the ATP-binding cassette (ABC) transport system causing bacteria death. This study consisted of comparison of isolated RNA of MRSA not treated and MRSA treated with lignan 3'-demethoxy-6-O-demethylisoguaiacin. Both RNAs samples were differentially dyed with Cy3 and Cy5 during cDNA synthesis and hybridized on DNA chip. Afterwards, the chip was scanned in a GenePix 4000B scanner. The resulting gene expression profile was analyzed in databases for functional annotations to find a potential mechanism of the lignan in MRSA.
Project description:Methicillin-resistant Staphylococcus aureus (MRSA) is the causative agent of serious hospital- and community-associated infections. Due to the global rise in community-associated MRSA, the respective lineages are increasingly introduced into hospitals. This raises the question whether and, if so, how they adapt to this new environment. The present study was aimed at investigating how MRSA isolates of the USA300 lineage, infamous for causing infections in the general population, have adapted to the hospital environment. To this end, a collection of community- and hospital-associated USA300 isolates was compared by RNA-sequencing. Here we report that merely 460 genes were differentially expressed between these two epidemiologically distinct groups, including genes for virulence factors, oxidative stress responses and the purine, pyrimidine and fatty acid biosynthetic pathways. Differentially regulated virulence factors included leukotoxins and phenol-soluble modulins, implicated in staphylococcal escape from immune cells. We therefore investigated the ability of the studied isolates to survive internalization by human neutrophils. This showed that the community-associated isolates have the highest neutrophil-killing activity, while the hospital-associated isolates are better adapted to intra-neutrophil survival. Importantly, the latter trait protects internalized staphylococci against a challenge with antibiotics. We therefore conclude that prolonged intra-neutrophil survival serves as a relatively simple early adaptation of S. aureus USA300 to the hospital environment where antibiotic pressure is high.