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Control of Microbial Growth

Control of Microbial Growth. Tim Ho University of Alberta, Canada * The materials are mostly based on Dr. Brian Lanoil’s Microb 265. Part III. Objectives. Physical agents Mechanical removal methods Chemical agents. Know 3 methods of microbial control

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Control of Microbial Growth

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  1. Control of Microbial Growth Tim Ho University of Alberta, Canada * The materials are mostly based on Dr. Brian Lanoil’s Microb 265 Part III tim3@ualberta.ca

  2. Objectives • Physical agents • Mechanical removal methods • Chemical agents tim3@ualberta.ca Know 3 methods of microbial control Know the strategies on how drugs control the growth of microorganisms. Understand how do bacteria become resistant to antibiotics.

  3. Antibiotic resistance • It is always the serious problem • Plasmid transfer, the horizontal gene transfer, is the main cause of resistance • Nosocomial infection: an infection occurs in a hospital environment tim3@ualberta.ca Image: Reacher M H et al. BMJ 2000;320:213-216

  4. Bacterial mechanisms of Antibiotic resistance Exclusion: active efflux from the cell Enzymatic inactivation: enzyme is produced to inactivate antibiotic molecule tim3@ualberta.ca Modification of antibiotic or target 4 Image: http://textbookofbacteriology.net/resantimicrobial_3.html

  5. 3 Sources of resistance genes • Bacterial chromosomes: • Spontaneous mutations cause • drug target sites change • Plasmids: • R plasmids: resistance • can be transferred to other • cells by horizontal gene • transfer • - Can carry multiple genes tim3@ualberta.ca • Mobile genetic elements: • Transposons, integrons • can be freely exchanged • between bacteria 5

  6. Horizontal gene transfer in bacterial cell • Transformation: transfer of free DNA from environment • Conjugation: require contact • Transduction: transfer gene by viral delivery tim3@ualberta.ca 6 Image: http://textbookofbacteriology.net/resantimicrobial_3.html

  7. How to prevent drug resistance • Drug should be given in high concentration • Give two or more drugs at the same time • Use drugs ONLY when necessary • Future solutions: develop new drugs, use bacteriophages to treat bacterial disease… tim3@ualberta.ca WHY: make sure the drug kill all bacteria otherwise it is high possibility that few resistant bacteria remain in body and starts to grow. 7

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