Chapter 11: How Bacteria Became Resistant to Antibiotics

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Department
Microbiology and Immun (Sci)
Course
MIMM 465
Professor
Albert Berghuis
Semester
Fall

Description
Chapter 11 How Bacteria Became Resistant to Antibiotics Costs of Antibiotic Resistance y There were many MRSA in the US where they were common nosocomial infection causes y They could be known as multiply resistant S aureus with the way that they were resistant to everything y Only vancomycin was effective against it and there is some resistance building up against it too y Studies were done and found the 21 of all S aureus infections were from MRSA and that the cost to treat each of these patients was 2500 and even 3700 if they had to be hospitalized It was expensive because y Vancomycin is more expensive y Necessary to isolate patients y MRSA patients stay longer in the hospital y The death rate was very high at 21 25 times higher than normal y They are not actually more virulent but it is just more difficult to treat them therefore the deaths are largely because of antibiotic resistance y There are also costs associated with the patient because they do not work and businesses get disruptedOverview of Resistance Mechanisms y Mechanisms can be grouped into 4 categories y Restricted access of antibiotic to target o Porins of grambacteria that restrict diffusion of antibiotics access OM and pump antibiotics out of bacterial cytoplasm o Can be divided into groupsOuter Membrane Porins y In Gram negative bacteria OM functions as barrier to antibiotic entry this is the reason why vancomycin cannot work against gram negative bacteriabecause it is too bulky y This advantage can be increased by having porins which are located on the OM that further limit diffusion where a single mutation can confer resistance to more than more type of antibiotic y Although less effective than other methods the increase in resistance can be very disastrousReduced Uptake across Cytoplasmic Membrane y Prevents entry of antibiotics into cytosol where it has to act y It is quite a rare mechanismy However sometimes the antibiotics use a transporters as is the case for aminoglycosides y The transporter is actually very important for the bacteria so the bacteria cannot mutate it so no resistance develops unless it can find an alternative y Some are more resistant to aminoglycosides in anaerobic conditions where E coli is 10 times more resistant to aminoglycosides when growing anaerobically y This is probably because of less uptake of the antibiotic o Can also have active efflux mechanismsResistance to tetracyclines y Some proteins pump antibiotics out through efflux pumps y Was an energy dependent transporter of tetracycline out of the bacterium
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