Antibiotic resistance Flashcards
Types of resistance
Intrinsic or acquires
Constitutive or inducible
Intrinsic resistance
Lack of drug target or access to drug
Acquired resistance
Genetic variability
Real time clinical decision making
Constitutive resistance
Always present - pseudomonas
Inducible resistance
Stimuli triggers gene expression
Expanded-spectrum beta-lactamases in E. coli
Resistance from single nucleotide base pair mutations
Quinolone resistance
Evolution of beta lactamases in gram -
Mechanism for resistance
Altered drug permeability
Altered drug targets
Inactivation of drug
Active efflux
MIC
in microbiology, the lowest concentration of an antimicrobial that will inhibit growth of a microorganism in liquid culture
MBC
s the lowest concentration of an antibacterial agent required to kill a particular bacterium on solid medium
Sensitive
Serum concentration at least 4X MIC
Kirby-Bauer plate
AB discs placed on agar
Bacterium that develops resistance by altered penicillin binding proteins
Streptococcus pneumoniae
Bacteria that uses modified cell wall targets for resistane
Vancomycin resistant enterococus (VRE)
Altered RNA polymerase binding
MTB to rifampin
Ribosomal RNA methylation
Group A streptococcus - erythrpmycin or clindamycin
Efflux pump
Salmonella & coagulase negetive stahylococci to doxycycline in gentamicin
Drug insensitive dihydrofolate reductase
E coli to TMP-SMX
Drug for resistant coagulase-negetive staphylococci & enterococcus
Vancomycib
Drug for resistant p. aeruginosa
Antipseudomonal penicillin or cephalosporin (i.e. piperacillin or ceftazidime) or carbapenem + aminoglycoside or quinolone
Drug for resistant enteric gram 0
Extended-spectrum cephalosporin or carbapenem + aminoglycoside or quinolone
Drug for resistant anerobes
Metronidazole> meropenem >beta-lactam + beta-lactamase inhibitors> cefotetan>clindamycin
Resistant s. aureus
vancomycin
Resistant s. pneumoniae
Meningitis or Sepsis: Vancomycin/Ceftriaxone
Pneumonia: Ceftriaxone
Resistant group A streptoccus
Penicillin or cefazolin
Resistant Neisseria meningitidis
Ceftriaxone
Resistant H. influenza
Ceftriaxone or beta-lactam + beta-lactamase inhibitor combinations
Management of MRSA infection
Cutaneous abcess:
- Incision and drainage
Hospitalized patients with complicated skin and soft tissue infections:
- Incision and drainage
Adjunctive measures
- Use of cultures
- Foreign body or device removal (if in place >30 d)
GNR resistant to beta lactams
Often inducible
Penicillinase and Cephalosporinases
Extended spectrum beta-lactamases” (ESBL): Historically a specific reference to genetically related families of beta-lactamases that conferred resistance against the majority of penicillins and cephalosporins
Carbapenemases
GNR with Pan resitant
Resistance to antipseudomonal cephalosporins, antipseudomonal carbapenems, piperacillin/tazobactam, ciprofloxacin and levofloxacin
GNR with XDR or extreme drug resistance
Resistance to antipseudomonal cephalosporins, antipseudomonal carbapenems, piperacillin/tazobactam, ciprofloxacin and levofloxacin
AND
Resistance to aminoglycosides (including amikacin), tigecycline, polymixins (colistin)
Multidrug-resistant Acinetobacter
Health-cares associated infections:
- Mostly VAP and bloodstream infections
- Common source outbreaks related to respiratory and ventilator equipment
Military personnel
Disasters
Community outbreaks (rare0
