Antibiotic Resistance Flashcards
What is intrinsic resistance?
Intrinsic resistance is a quality that a bacteria naturally has to prevent the drug from penetrating or acting on it
- Lack of drug targets or lack of access to drug targets
What is acquired resistance?
Genetic variability allows bacteria to become resistant to an antibiotic that used it to be sensitive to
What is constitutive resistance?
Bacterial mechanism is consistently present and usually essential to bacterial function
What is inducible resistance?
Resistance gene turned on in response to environmental stimuli (e.g. antibiotics) => Expanded-spectrum beta-lactamases in E. coli
What are examples of single nucleotide base pair mutations?
1) Quinolone resistance:
- Point-mutations in DNA gyrase or topoisomerase
2) Evolution of beta-lactamases in gram-negatives
- Families differ by many AA’s. Within families, isoenzymes differ from each other by single or several AA’s.
What is the mechanism behind larger DNA rearrangement (jumping genes) bacterial resistance?
Transposable DNA segments prone to rearrangement in bacterial chromosome or plasmid DNA
What is the mechanism behind acquisition of DNA from other bacteria as a means of bacterial resistance?
- Foreign DNA containing resistance genes can be acquired from plasmids, bacteriophages, and transposable genetic elements
- Conjugation, transduction, transformation allow genetic material to move within populations of bacteria and is perpetuated over time
How do bacteria survive antibiotic exposure?
1) Alter drug permeability
2) Alter drug targets
3) Inactivate of drug
4) Active efflux
What are the dominant resistance mechanisms to cell wall synthesis blocking antibiotics?
1) Altered penicillin-binding proteins (ie Streo Pneumonia)
2) Modified cell wall targets (Vancomycin resistant enterococcus)
What is the major resistance mechanism to quinolines?
1) Altered gyrase or topoisomerases
What are the major resistance issues of S. aureus?
1) Beta-lactamase
2) Altered PBPs (MRSA, mecA gene+)
What drug should be used for resistance S. aureus?
Vancomycin
What are the major resistance issues of Strep. pneumonia?
Altered PBPs
What drugs should be used for resistant Strep. pneumoniae?
1) Meningitis or Sepsis: Vancomycin/Ceftriaxone
2) Pneumonia: Ceftriaxone
What is the major resistance issue of Group A strep?
Erythromycin resistance
What drugs should be used for resistant Group A Strep?
Penicillin or cefazolin
What are the major resistance issues of N. meningitides?
- Beta-lactamase
- Altered PBPs
What drugs should be used for resistant N. meningitides?
Ceftriaxone
What are the major resistance issues of H. influenzae?
Beta-lactamase production
What drugs should be used for resistant H. influenzae?
Ceftriaxone or beta-lactam + beta-lactamase inhibitor combinations
What are 3 main ways of managing MRSA infections?
1) Incision and drainage
2) Use of cultures
3) Foreign body/device removal (if in place >30 days)
What are the common gram negative rods that carry a lot of drug resistance?
1) Enterobacteriaceae => E. coli, Klebsiella, Enterobacter, (Serratia, Proteus, Citrobacter, Salmonella)
2) Acinetobacter
3) Pseudomonas
What risks are associated with gram negative rod resistance?
> Hospital stay, ICU, longterm care facility, central lines and urinary catheters, abdominal surgery, prior antibiotics, ventilator, dialysis
Gram negative rods generally carry resistance to which drug group?
Beta lactams (Penicillinase and Cephalosporinases, Carbapenemases)
What populations are at increased risk of multi drug resistant acinetobacter?
1) Health-cares associated infections:
- Mostly VAP and bloodstream infections
- Common source outbreaks related to respiratory and ventilator equipment
2) Military personnel
3) Disasters
4) Community outbreaks
