EEB214H1 Lecture 18: Staphylococcus aureus

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Ecology & Evolutionary Biology
Jennifer Carpenter

EEB214 Lecture 18 Staphylococcus aureus • bacteria to get resistance to anti-biotics • misused by people • anti-biotics only kill bacteria, not fungus, viruses etc., • Use of antibiotics will lead to resistance and we use them a lot o 80% of students got non-prescribed antibiotic for diarrhea • you might be sick from a resistance bacteria • we only know it works is by taking a sample and test to see which antibiotic is correct for each patient o which we do not have time to do • antibiotic half the time kills all bacteria, which can cause more problems o you’re selecting for good bacteria to be resistance • Resistance is often conferred by plasmids o most antibiotic genes are not part of the main genome bacteria • These plasmids can be transferred between cells and species through a sex-like process • sex is favoured when there is variation in the environment o patchy environment, you’re going to favour a lot of sex like things that mix up genotypes • most plasmids exist in the environment, resistance bacteria for every antibiotic o protein we get from other organisms o as soon as we start using fungus defence, that allele started spreading o overusing can create selective pressure for the resistance Pesticide • We select for pesticide resistance • used by US army in WWII • lots of use of these things create a very strong selective force for resistance • some insects evolve behaviour to evolve being near crops where pesticide is being sprayed o some species where they can resist to chemicals • Mosquito mortality when exposed to DDT o variation in certain populations o low mortality = near farms where there’s a lot of DDT in the environment o resistance allele Is associated with the DDT • Populations with lots of the allele are more resistance to the pesticide o the resistance alleles have increase in frequency over time o these alleles are point mutations where one allele changes o also duplication can help spread resistance o selection when we use pestici
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