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resistance to antibiotics in the environment.docx

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McMaster University
Life Sciences
Luc Bernier

March 28 , 2013 Life Sci 2H03: Environmental Life Sciences Resistance to Antibiotics in the Environment Resistance to Antibiotics in the Environment - environmental degradation increasing scale to human activities - different circles where the bacteria are not resistant to the antibiotic What is an Antibiotic? - refers only to drugs that kill or inhibit, fungi or viruses (very few as they are more complicated) - first antibiotics were of natural origin - penicillin: relatively small molecules - streptomycin - 1000Da - isolated from different types of microorganisms - in this case from fungi - now produced - variants from natural ones - antibiotics can be grouped by either their chemical structure or mechanism of action - often complex molecules which may posses different functionalities - different classes have different targets - ex.: tetracyclins affecting translation - we eventually see mechanisms of resistance - e.g. Penicillin, by a combination of all these classes multiple functions of cells can be targeted and impaired, getting rid of the pathogenic agents - microbes are diverse and have been able to adapt to chemicals The Emergence of Antibiotic Resistance - if we look at the dark ages: when infections occurred, there were no antibiotics that could releave or cure these microbial infections - discovery of penicillin lead to understanding the modes of action and the potential of other antibiotics - 1950s golden age of antibiotics - 1960s more efforts to use appropriate dosage for the treatment - office in order to approve antibiotics - purposely designed antibiotics are introduced targeting specifics of the cell - increasing antibiotic resistance, also in terms of doses or the diversity of microbes showing signs of resistance - since the start of the current century, most classes of antibiotics are useless as there is a trend of increasing resistance Antibiotic Resistance: A Growing Problem - Beta-lactamase enzymes identified - Same class of penicillin - Degrade this class of antibiotics - Number of different enzymes documented has increased since the 1970s - Almost 1000 different types of enzymes able to resist to this class of antibiotics Antibiotic Resistance is Found Worldwide - beta-lactamases - different sub-categories identified - widely distributed worldwide - genetic screening to see if there are genes coding for this antibiotic resistance - appropriate sub-categories of antibiotic to be affective to respond to treatment What are the Mechanisms of Antibiotic Resistance? - Pathogens have used their genetic variation to protect themselves - mechanisms existed naturally and were subject to exchange: long before the antibiotic era - pressure created by antibiotic, the exchange rate has increased over the year - changing chemistry of the cell membrane or the cell wall - pumps expelling the antibiotics out of the cell, not able to affect enzymatic machinery - prevalence of mutations of antibiotics affecting the synthesis of messenger RNA or proteins - enzymes that have emerged that breakdown antibiotics, membrane bound enzymes that can breakdown these compounds How Old is Antibiotic Resistance? - compares level of relatedness - shows that these genes B-lactamases: over 2 billion years old - also true for genes leading to resistance of tetracycline using phylogenetic analysis What is the Ecological Role of Antibiotic Resistance? - ecological examples of antibiotic functions for microbial products in nature are rare - leaf cutting ants have ingested fungi that produces an antibiotic that eliminates on of the parasites that would lead to the spoiling of one of their food sources - actinomycete - hormone sensing: alert other members of potential food sources - prior to large scale sequences a lot of the studies were based on cultivation - studies with soils from Alaska, we expect to see a lot of antibiotic resistance - able to discover resistant genes for ampicillin, tetracycline and vancomycin - found in natu
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