Project description:In this work we describe a robust fosfomycin collateral sensitivity phenotype of Pseudomonas aeruginosa resistant mutants selected by antibiotics from different structural families. The underlying mechanism was the reduced expression of the genes encoding the peptidoglycan-recycling pathway, which preserves the peptidoglycan synthesis in situations where the de novo synthesis is blocked, and of fosA, encoding a fosfomycin-inactivating enzyme.
Project description:Fosfomycin is a bactericidal antibiotic, analogous to phosphoenolpyruvate (PEP) that exerts its activity by inhibiting the activity of MurA. This enzyme catalyzes the first step of peptidoglycan biosynthesis, the transfer of enolpyruvate from PEP to uridine- diphosphate-N-acetylglucosamine. Fosfomycin is increasingly used in the last years, mainly for treating infections caused by Gram-negative multidrug resistant bacteria as Stenotrophomonas maltophilia, an opportunistic pathogen characterized by its low susceptibility to antibiotics of common use. The mechanisms of mutational resistance to fosfomycin in Stenotrophomonas maltophilia were studied in the current work. None of the mechanisms so far described for other organisms, which include the production of fosfomycin inactivating enzymes, target modification, induction of alternative peptidoglycan biosynthesis pathway and the impaired entrance of the antibiotic, are involved in the acquisition of such resistance by this bacterial species. Rather the unique cause of resistance in the studied mutants is the mutational inactivation of different enzymes belonging to the Embden-Meyerhof-Parnas central metabolism pathway. The amount of intracellular fosfomycin accumulation did not change in any of these mutants showing that neither the inactivation nor the transport of the antibiotic were involved. Transcriptomic analysis also showed that the mutants did not present changes in the expression level of putative alternative peptidoglycan biosynthesis pathway genes neither any related enzyme. Finally, the mutants did not present an increased PEP concentration that might compete with fosfomycin for its binding to MurA. Based on these results, we describe a completely novel mechanism of antibiotic resistance based on the remodeling of S. maltophilia metabolism.
Project description:The antibiotic fosfomycin is widely recognized for treatment of lower urinary tract infections caused by Escherichia coli and lately gained importance as a therapeutic option to combat multidrug resistant bacteria. Still, resistance to fosfomycin frequently develops through mutations reducing its uptake. Whereas the inner membrane transport of fosfomycin has been extensively studied in E. coli, its outer membrane (OM) transport remains insufficiently understood. While evaluating minimal inhibitory concentrations in OM porin-deficient mutants, we observed that the E. coli ΔompCΔompF strain is five times more resistant to fosfomycin than the wild type and the respective single mutants. Continuous monitoring of cell lysis of porin-deficient strains in response to fosfomycin additionally indicated the relevance of LamB. Furthermore, the physiological relevance of OmpF, OmpC and LamB for fosfomycin uptake was confirmed by electrophysiological and transcriptional analysis. This study expands the knowledge of how fosfomycin crosses the OM of E. coli.
Project description:Colonizing commensal bacteria after birth are required for the proper development of the gastrointestinal tract. It is believed that bacterial colonization pattern in neonatal gut affects gut barrier function and immune system maturation. Studies on the development of faecal flora microbiota in infants on various formula feeds showed that the neonatal gut was first colonized with enterococci followed by other flora microbiota such as Bifidobacterium in breast feeding infants. Intriguingly, Bjorksten group Other studies showed that Bbabies who developed allergy were less often colonized with Enterococcus during the first month of life as compared to healthy infants. A lot of Many studies have been done on conducted to elucidate how bifidobacteria or lactobacilli, some of which are considered probiotic, regulate infant gut immunity. However, much fewer studies have been focused on enterococi. In our study, we demonstrate that E. faecalis, isolated from healthy newborns, suppress inflammatory responses activated in vivo and in vitro. We found E. faecalis attenuates proinflammatory cytokine secretions, especially IL-8, through JNK and p38 signaling pathways. This finding shed light on how the first colonizer, E.faecalis, regulate inflammatory responses in the host. Samples are analysed using web-based GEArray Expression Analysis Suite
Project description:Anaerobic bacteria in the oral cavity can cause respiratory infections. However, their precise mechanisms of action remain elusive. Unexpectedly, bacterial flora analysis using 16s rRNA revealed ‘hidden’ mixed infections of anaerobic bacteria and commensal oral Streptococcus species in community-acquired pneumonia. The purpose of this study is to elucidate the mechanisms by which Prevotella intermedia exacerbates oral streptococcal pneumonia.
Project description:<p>Intestinal inflammation and the related gut microbiome dysbiosis are becoming prevalent worldwide. Overgrowth of Enterobacteriaceae exacerbates intestinal inflammation and gut microbiome dysbiosis. Enterobacteriaceae secrets siderophore to acquire iron and survive in the iron-limited gut. Therefore, inhibiting the dysbiotic expansion of Enterobacteriaceae to restore gut microbiome homeostasis and alleviate intestinal inflammation by disrupting siderophore-mediated iron acquisition necessitate further investigation. We revealed that siderophore enterobactin is vital for Enterobacteriaceae-induced intestinal inflammation and gut microbiome dysbiosis. Furthermore, we found that commensal bacterium Clostridium bolteae (C. bolteae), a member of Lachnospiraceae, disrupts siderophore-mediated iron acquisition in Enterobacteriaceae and suppresses Enterobacteriaceae expansion. This strategy induces compensatory enterobactin synthesis, leading to the accumulation of enterobactin and energy depletion in Enterobacteriaceae. This work suggests that targeting siderophore-mediated iron acquisition pathway by commensal bacteria represents a promising strategy to suppress Enterobacteriaceae expansion and restore gut microbiome homeostasis.</p>