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Flashcards in Antibiotics 3 Deck (15)
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1
Q

When does a bacterial superinfection occur?

A
  • when resistant bacteria are allowed to grow and thrive, leading to the super infection of resistant bacteria
2
Q

What are the most common causes of antibiotic resistance?

A
  • overuse of antibiotics in humans
  • overuse of antibiotics in non-humans
  • use in developing countries
  • world travel
  • critically ill patients
  • promotion of antibiotics
3
Q

What increases the risk of antibiotic resistant infections?

A
  • patient related factors (increasing age, increasing severity of underlying disease)
  • hospital related factors (increased length of stay, admission to the ICU, proximity of infected patients)
  • treatment related factors (prolonged use of broad spectrum antibiotics, contaminated devices or procedures)
4
Q

How is antibiotic use in developing countries contributing to resistance?

A
  • antibiotics are available OTC
  • poor patient compliance
  • cost (take sub therapeutic course)
  • antibiotic quality is low, with a lot of counterfeit and poor quality Abs
5
Q

What are the different ways that a bacteria can become resistant? (genetics of mutation)

A
    • spontaneous mutation
  • -acquisition of new DNA
  • via transformation: DNA comes from the environment after being released by another cell (plasmid DNA)
  • transduction: virus transfers DNA between bacteria
  • Conjugation: contact between cells as DNA crosses from donor to the recipient
6
Q

What are the two general mechanisms of antibiotic resistance?

A
  • alteration of the target site

- decreased uptake by bacteria

7
Q

What strategies could we use to overcome the problem with beta lactamases?

A
  • can develop inhibitors of beta lactamases (clavulanic acid)
  • combine the penicillin with the use of other antibiotics
  • can add bulkier side chains to the penicillin structure, hindering the access of the Beta lactamase enzyme
8
Q

By using a beta lactam antibiotic along with a beta lactamase inhibitor, you get a _____ effect

A

synergistic

9
Q

What is the resistance to tetracyclines caused by?

A
  • resistance is due to decreased uptake or increased extrusion of the Ab
  • widespread resistance to tetracyclines limits clinical use
  • bacteria have cross resistance
  • Mg dependent active efflux is mediated by the TetA gene is the most common resistance mechanism
  • other mechanisms of bacterial resistance
  • — bacterial enzymes that inactivate tetracyclines
  • — expression of bacterial proteins that inhibit binding of tetracycline to the ribosome
10
Q

What is the bacterial resistance mechanisms against aminoglycosides?

A
  • decreased uptake of the drug
  • – absence of porin channels
  • – absence of oxygen dependent transport system
  • enzymes that inactivate aminoglycosides
  • – acetyltransferases
  • – nucleotidyltransferases
  • – phsophotransferases
  • cross resistance is rare
11
Q

What is the bacterial resistance mechanisms to macrolides?

A
  • decreased uptake of the drug
  • increased efflux of the drug
  • reduced affinity for the 50S ribosomal subunit
  • – methylation of an adenine in the 23 S bacterial ribosomal RNA
  • enzymes that inactivate macrolides
  • – erythromycin esterase
  • cross resistance is common
12
Q

What is the resistance mechanism against fluorquinolones?

A
  • alterations to DNA gyrase
  • decreased uptake
  • increased efflux
  • cross resistance amount quinolone is common
13
Q

Describe resistance to ciprofloxacin?

A
  • widespread resistance by S aureus, S pyogenes, enterococcus and K pneumonia
  • once considered a powerful Ab of last resort
  • widespread use to eat minor infections and unapproved used promoted resistance
  • – ear infections
  • – acute respiratory illness
  • – widespread veterinary usage
14
Q

Describe bacterial resistance to sulfonamides and trimethoprim

A
  • bacteria that obtain folate from the environment are inherently resistant to sulfonamides
  • resistance is due to mutations that alter key functions in bacteria
  • – sulfonamides: altered dihydropteroate synthase
  • — trimethoprim: altered dihydrofolate reductase
  • — reduced cellular permeability to the drugs
  • — enhanced production of folates
15
Q

Describe bacterial resistance to cotrimoxazole?

A
  • bacteria that obtain folate from the environment are inherently resistance to sulfonamides
  • cotrimoxazole resistance is rare since bacteria must have simultaneous resistance to both the sulfonamide and trimethoprim drug
  • emergence of antibiotic resistant bacteria has recently renewed interest in cotrimoxazole