Presentation on theme: "Quinolones: mechanisms of resistance"— Presentation transcript:
1Quinolones: mechanisms of resistance Niels Frimodt-MøllerNational Center of Antimicrobials and Infection ControlStatens Serum InstitutCopenhagen, Denmark
2Quinolone mechanisms of resistance Change in receptorMutations in genes for gyrases/topoisomerases2) Change in penetrationEfflux-mechanisms: Proton-pumps with active transport of quinolone out of cell3) Enzymatic degradationAlways (almost) chromosomal(plasmid carried transfer found in Klebsiella, mechanism?)
3Gram negativ bakterie kinolonresistensmekanismer. DNA + gyrasekomplexEffluxpumperPorer
4DNAStructure of the Topo I/DNA complex. During replication, the unwinding of DNA may cause the formation of tangling structures, such as supercoils or catenanes. The major role of topoisomerases is to prevent DNA tangling.
5The structure of supercoils The structure of supercoils. (a) Positive supercoils - the front segment of a DNA molecule cross over the back segment from left to right. (b) Negative supercoils. (c) The positive supercoil in bacteria during DNA replication.
6There are two types of topoisomerases: type I produces transient single-strand breaks in DNA:The topo I of both prokaryotes and eukaryotesandtypes II produces transient double-strand breaks:The eukaryotic topo II, bacterial gyrase, and bacterial topo IV belong to the type IIThe gyrase has two functions: (1) to remove the positive supercoils during DNA replication, (2) to introduce negative supercoils (one supercoil for turns of the DNA helix) so that the DNA molecule can be packed into the cell. During replication, these negative supercoils are removed by topo I.Malfunction in topoiomerases causes cell death. .
7The function of topo II: (a) To remove supercoils The function of topo II: (a) To remove supercoils. This involves a double-strand break (indicated by a short line), allowing the tangled segment to pass through. The break is then resealed. (b) To remove catenanes. The topo II makes a double-strand break in one DNA molecule (the blue one), allowing the other molecule to pass through. The break is then resealed.
9Quinolone resistance mechanism Mutations in gyrA QRDR resistance in Gram-negativesMutations in parC QRDRresistance in Gram-positives
10Gram negativ bakterie kinolonresistensmekanismer. DNA + gyrasekomplexEffluxpumperPorer
11Accumulation of moxifloxacin in P Accumulation of moxifloxacin in P. aeruginosa +/- CCCP (efflux inhibitor)Ng mox./mg dry cellMinutes
12Accumulation of ciprofloxacin and lomefloxacin in fluoroquinolone-resistant strains of Escherichia coli XIA Peiyuan et al. Chin Med J 2002; 115:31-5.Accumulation of LMLX in E. coli strains. Each curve indicates the accumulated concentration of LMLX in one strain at diffe rent time point.JF701 and JF703: control strains; Ecs: susceptible strain. R 2 and R256: the in vitro selected resistant strains; R5 and R6: the clinical res istant strains.
13Involvement of Topoisomerase IV and Gyrase as Ciprofloxacin targets in S. pneumoniae StrainMutations in QRDR of:ParC GyrA GyrB ParECiproMICD51B10Ser-79Phe4D11Glu-87> Lys64E4Arg-95CysPan et al. Antimicrob Ag Chemother 1996, 40:
14Quinolone resistance types in E. coli StrainMutation in gyrAMutation in parCRedu-ced accum.CiproMICMoxifloxATCC259220.0080.03WT-4S80I0.25MIS830.51WT-3S83+D872WT-3-M46432MII+4MIII256128Schedletzky et al. JAC, 1999, 43 suppl.B: 31-7
15Effect of fluoroquinolone concentration on the recovery of single-step, resistant mutants Moxifloxacin (open circles) or levofloxacin (solid circles) Unlabeled arrows indicate MIC The triangle indicates no colony recove-red at that drug concentration and bac-terial load. The dashed line indicates one colony recovered per 1010 cells tested. Three strains were tested: wild-type strain ATCC (A); strain KD2138, a ParC (Ser-79 to Tyr) variant (B); and strain KD2139, a GyrA (Ser-81 to Phe) variant (C) Two double mutants were recovered from each point indicated by an arrow.Li et al. Antimicrob Ag Chemother 2002, 46:
16Changes in the susceptibility of S Changes in the susceptibility of S. aureus 201 during and after 3-day treatments with four fluoroquinolones at different AUC24/MIC ratios.Firsov et al. Antimicrob Ag Chemother 2003, 47:
17Relationship of pharmacokinetics and MPC Mutant Prevention Concentrations of Fluoroquinolones for Clinical Isolates of Streptococcus pneumoniaeBlondeau et al., Antimicrob Ag Chemother 2001, 45:Relationship of pharmacokinetics and MPCFluoroquinoloneMPCpr90 (µg/ml)Dose (mg)Cmax (µg/ml)t1/2 (h)Moxifloxacin24004.512Gatifloxacin44.28Trovafloxacin2003.1Grepafloxacin600<2.714Levofloxacin5005.7
18Combination therapy resulted in lower rates of resistance. Thomas JK, et al. Antimicrob Agents Chemother 1998; 42: Pharmacodynamic evaluation of factors associated with the development of bacterial resistance in acutely ill patients during therapy.Five different regimes in ICU could be avaluated for resistance developments in different bacterial species (total of 128 patogenes in 107 ptt.).cirofloxacin aloneciprofloxacin + piperacillinceftazidime aloneceftazidime +tobramycincefmenoxime aloneThe overall predictor for development of resistance was AUC/MIC < 100.Combination therapy resulted in lower rates of resistance.
19Thomas JK et al. Antimicrob Ag Chemother 1998; 42: 521-7. Resistance developed in -lactamase-type-I Gram-neg. rods even when AUC/MIC > 100 after -lactam monotherapy.Median time to resistance:6 days if AUC/MIC < 100.AUC/MIC > 100AUC/MIC < 100
20Quinolone resistance: Summary Mutations in genes for topoisomerases (gyr, par): MIC increases with no. of mutations; rate ~ 1 in 10-7Changes in efflux mechanisms: Pumps out drug; NB: inhibitors; Can be first step in development of resistanceBoth 1 and 2 can be present in same strain – leads to high MIC´sMajority of R-genes chromosomal – plasmid transported gene reported