1.Fatro worldwide exclusive antibiotic Roberto Farina - Fatro

2. RIFAXIMIN Class: Rifamycins Subclass of the larger family Ansamycins Antibiotics produced by the Gram+ bacterium Amycolatopsis mediterranei Particularly potent against Multi-resistant Staph. Aureus Mycobacteria Rifaximin: semi-synthetic derivative of rifamycin SV 3. RIFAXIMIN Physiochemical Properties Zwitterion Pyrido nitrogen positively charged Imidazo nitrogen negatively charged Phenolic hydroxyls Strong tendency to self-associate Ionized at all pH values Additional pyridoimidazole moiety makes it NON-ABSORBABLE ion trapping Acts locally and does not pass into the circulation 4. RIFAXIMIN Mechanism Of Action Prevents transcription the process by which the information in DNA is copied into messenger RNA (mRNA) for protein production. Inhibits RNA and protein synthesis Binds to the subunit of prokaryotic DNA-dependent RNA polymerase TRANSCRIPTION ANIMATION 5. RIFAXIMIN Antimicrobial Activity Broad spectrum of antibacterial action: Gram+ and Gram- Both Aerobes and Anaerobes Susceptibility of resistant strains of Staph. aureus is particularly interesting Protozoa Cryptosporidium, Blastocystis Reverse transcriptase of certain RNA viruses (retrovirus) 6. RIFAXIMIN Antimicrobial killing activity Rapidly kills fast-dividing bacteria as well as persisters cells, which remain biologically inactive for long periods evading antibiotic activity [Pozniak 1999] Bactericidal Actually kills bacteria Image 7. RIFAXIMIN Not Absorbed Systemically Valuable for therapies applied locally to body surfaces Skin or mucosae High local bioavailability Localized targeting of pathogens Absence of residues in non-treated organs Reduced incidence of undesired side effects Scarpignato & Pelosini 2005 100% TOPICAL ANTIMICROBIAL 8. TOPICAL THERAPY & ANTIBIOTIC RESISTANCE A NOVEL APPROACH TO JUDICIOUS PRESCRIBING PRACTICE Limited selective pressure for the development of wide-spread bacterial resistance Preservation of critically important antimicrobials for systemic therapy Antimicrobial is sequestered in target organs Very high local concentrations Circumscribed antimicrobial activity 9. ANTIMICROBIAL RESISTANCE Resistance of a microorganism to an antimicrobial medicine to which it was previously sensitive (WHO) One of the main problems associated with antibiotics use Therapeutic failure Infections persist and may spread Impact on animal health and productivity Emergence of resistant microorganisms that can infect people (Superbugs) Great clinical, economic, political and environmental implications Possible impact on human health 10. PROPER ANTIMICROBIAL SELECTION FIGHTS RESISTANCE Ability to lead to the development of resistant mutants Spread of resistance Stability of the mutants Effect on the susceptibility of other antimicrobial agents Relevant factors that determine the therapeutic value of antibacterials ANTIMICROBIAL RESISTANCE 11. DEVELOPMENT OF RESISTANCE TO RIFAXIMIN Studied in detail on several Gram- and Gram+, aerobic and anaerobic strains Resistance to Rifaximin is rare [Hoover 1993; Ruiz 2008; Marchese 2000; Ouyang-Latimer 2011; Valentin 2011] More easily with sub-inhibitory concentrations Anaerobic atmosphere hinders the selection of rifaximin-resistant bacteria High concentrations in in an oxygen-deficient milieu: in-vivo occurrence of bacterial resistance with rifaximin is an infrequent phenomenon 12. Staph. aureus SUSCEPTIBILITY TO ANTIMICROBIALS 6% 31% 31% 8% 36% 77% 36% 84% 86% 89% 94% 92% 82% 93% 99% 0% 25% 50% 75% 100% Sulfa Penicillin Ampicillin Spectinomycin Streptomycin Tetracycline Spiramycin Erythromycin Kanamycin Tylosin Cloxacillin Nafcillin Cefoperazone Flumequine Rifaximin R % I % S % Bertocchi, Varisco, Farina 2000 Kirby-Bauer agar diffusion test Strains isolated from the milk of dairy cows with mastitis (IZS Brescia, Italy) 13. SPREAD OF RESISTANCE TO RIFAXIMIN Resistance due to a chromosomal alteration in the drug target, the DNA-RNA polymerase (rpoB gene) [Al-Orainey 1990] Different from the plasmid-mediated resistance common to other antibiotics [Smith 2002] The spread of resistance is less frequent than that due to plasmid-mediated transfer (transferred within the same generation, even between different bacterial species) [Collignon PJ 2002] Not disseminated by plasmids but mediated chromosomally Sulfa -lactamTetracycline Fenicol Aminoglicoside multi-R Plasmid 14. STABILITY OF RIFAXIMIN RESISTANT MUTANTS Resistance to rifaximin disappear after drug administration is terminated. Poorer viability of rifaximin-resistant mutants relative to nonresistant (wild-type) bacteria Resistance to rifaximin doesnt persist beyond a few weeks after cessation of therapy (specific time- dependent on species of bacteria) De Leo 1986 Disappearance of rifaximin-resistant bacteria after stopping the antibiotic treatment (week 0) RIFAXIMIN 15. ANNUAL VARIATION OF STAPH. AUREUS SENSITIVITY TO RIFAXIMIN From cows with mastitis IZS Tre Venezie Barberio 2000 Year Susceptible 1996 98.9 % 1997 93.4 % 1998 98.1 % 1999 98.7 % Carnevali Nocetti 2001 Year Susceptible 1996 96.95 % 1997 100.0 % 1998 99.49 % 1999 98.88 % 2000 98.28 % From cows with mastitis APA Modena 16. EFFECT ON THE SUSCEPTIBILITY LEVELS OF OTHER ANTIMICROBIAL AGENTS There is no evidence of cross-resistance to other non-rifamycin classes of antibiotics Herbert DuPont 2003 No-systemic involvement Preserves other antimicrobial agents, which are able to be used to treat systemic infections, diminishing their pressure on the microorganisms, favoring a lower selection of resistant strains It does not alter the microbiota population (other than those based in the treated compartment) 17. NON-ANTIBIOTIC EFFECTS OF RIFAXIMIN Rifaximin, besides acting against microorganisms, has also beneficial effects on Host Cells In addition to its antibacterial activity rifaximin exerts antiinflammatory and immunomodulatory effects Scarpignato 2005 BACTERIA ANIMAL CELLS 18. RIFAXIMIN MODULATES THE INFLAMMATORY RESPONSE Rifamycins are able to modulate neutrophil functions and display anti-inflammatory actions [Spisani 1997] Intra-articular rifamycin has been successfully used in chronic arthritis (juvenile rheumatoid arthritis and ankylosing spondylitis) [Caruso 1997] Rifaximin reduces overall inflammatory status modulating pro-inflammatory cytokine release IL-6, IL-1, IL-8, IL-12 and interferon-, TNF, chemokines [Brown 2010; Vitali 2009] 19. RIFAXIMIN MODULATES INFLAMMATION THROUGH PXR ACTIVATION Pregnane-X-Receptor mediates the anti-inflammatory activities of Rifaximin [Cheng 2010; Mencarelli 2011] PXR is a nuclear receptor (ligand- activated transcription factor) NR are sensing systems that govern the interactions between genome and internal environment PXR is activated by different xenobiotics and endobiotics RXR GENE TRANSCRIPTION XRE RFX PXR Expression of proteins involved in detoxification of foreign toxic substances 20. PREGNANE X RECEPTOR Master supervisor of detoxification of xenobiotics Orchestrate energy metabolism and immune responses to stresses caused by xenobiotic Inhibits nuclear factor NF-B signaling (nuclear factor kappa-light-chain- enhancer of activated B cells), a first responder to harmful cellular stimuli (DAMPs, PAMPs) PXR activation results in lower expression of proinflammatory cytokines and chemokines Wahli 2008; Mencarelli 2010 TLR NF-BPXR XENOBIOTIC RESPONSE PROINFLAMMATORY CYTOKINES CHEMOKINES Mutual negative crosstalk between NF-B and PXR DAMPs PAMPs HOST CELL ANTIINFLAMMATORYDETOXIFICATION 21. RIFAXIMIN REDUCES THE EXPRESSION OF INFLAMMATORY GENES IN EPITHELIAL CELLS ACTIVATED BY LIPOPOLISACCARIDES Rifaximin (100 M) was added to colon biopsies for 3 h, before LPS stimulation (100 g/ml) for 16 h. At the end of incubation the mRNA was extracted for the quantification *P