Microbiology Exam 3; bacterial response to antibiotics (2/3)

antibiotic resistance

the ability of bacteria to withstand the effects of antibiotics, making them ineffective in treating infections; more antibiotics are needed to treat infections than before, so the dosage given is increased

• is a “gradient”; i.e. pre-antibiotic resistance 1-2 would result in death of the bacteria, not 7-8 is needed. if at a 10 w/out effect, there is full resistance

full resistance

when a bacteria is unaffected by an antibiotics, even when the dosage is increased; a “cocktail” of antibiotics or more than one antibiotic are given to treat disease

examples of antibiotic resistance in Staphylococcus aureus

• VISA - strain that is slightly resistant to vancomyosin

• VRSA - strain that is fully resistant of vancomyosin

the more —- of antibiotics the —- antibiotics resistance will continue to grow

usage, more

How is there an evolutionary basis to antibiotic resistance

• most antibiotics are derived from the soil (streptomyces) and release antibiotics to kill of or inhibit competing microorganisms to get more nutrients to grow. -→ bacteria also has evolutionary drive, so coevolution occurs

• bacteria and antibiotics are evolving together, and using one another as “inspiration” on how to evolve and better compete

• as a result, bacteria has survived pressure in an environment and why we’re entering the end of the age of antibiotics

efflux pumps

• strategy of bacteria to counteract antibiotics

• will pump out antibiotics from the cells

• antibiotics will not be effective because the antibiotics are not inside of the bacterial cell

• use energy from ATP

biofilm

• strategy of bacteria to counteract antibiotics

• film the forms and protects the “bottom” layer of bacteria from antibiotics due to the top layer acting as a cushion → as a result, it is difficult for antibiotics to reach the bottom levels

• ex: pseudpmonas aeruginosa (water borne bacteria) and cystic fibrosis (occurs when the protein channel mutates so mucous is unable to receive ions and becomes thick, allowing bacteria to get trapped)

  • P. aeru can form in the mucous of those with c. fibrosis and form biofilms

overproduction of targets in bacterial cells

• bacteria will produce more of the cellular components that are being targeted by the antibiotic

• method of bacteria to counteract antibiotics

• ex: if you have 50 bullets and must hit 2-3 targets, you have a higher chance of landing some bullets. if you have 50 bullets but 3000 targets, theres no way of hitting every single one

  • bullets are the antibiotics and the targets are bacterial cells

• explains why increasing the dosage can be effective

produce enzymes that target antibiotics

the bacteria will produce specific enzymes that breakup the specific structure of the antibiotic so that it is ineffective; method of bacteria to counteract antibiotics

• ex: Beta lactamase - enzyme made by bacteria (common in S. aureus); will break up the rings (chemical makeup) of the Beta lactum structure (antibiotic)

• the enzyme produced by the bacteria must correspond with the antibiotic structure (ex: an enzyme that breaks up the structure of beta lactums would not be able to breakup the structure of vancomyosin)

• inhibitors are added to antibiotics as supplements to prevent the bacterial enzyme from working

Beta lactamase inhibitors

sylvanic acid that is added as a supplement to antibiotics to inhibit Beta lactamase and prevent it from breaking apart the structure of antibiotics

• ex: MRSA - methicillin resistant s. Aureus → modified antibiotics so that the antibiotic is not being effected by the enzyme produced by A. aureus

• Augmentin - mix of amoxicillin and sylvanic acid

Modify the target

• method of bacteria to counteract antibiotics

• ex: vancomyosin targets the alanine-alanine cross bridges of bacteria; bacteria modifies the target (the cell wall), by changing one of the alanines to another base, so that the antibiotic is rendered useless

Modify the pathway

• method of bacteria to counteract antibiotics

• ex: sulfa drugs; sulfa drugs prevent the bacteria from making folic acid, which makes nucleic acids; the bacteria could change its pathway so that it would be able to make nucleic acid bases from something other than folic acid