Presentation on theme: "Pierre-Louis Toutain National veterinary School Toulouse France"— Presentation transcript:
1Pierre-Louis Toutain National veterinary School Toulouse France Are we over-rating the risk of low-dose drug exposure on the selection of resistant strains?Pierre-Louis ToutainNational veterinary SchoolToulouseFrance
2But of what resistance are we speaking? The question: Are we over-rating the risk of low-dose drug exposure on the selection of resistant strainsBut of what resistance are we speaking?
3Prevent emergence of resistance: but of what resistance?
4The priorities of a sustainable veterinary antimicrobial therapy is related to public health issues, not to animal health issues
5The question: Are we over-rating the risk of low-dose drug exposure on the selection of resistant strains?The public health issues being critical , we have to investigate both:The case of target pathogensThe case of non-target pathogensZoonoticCommensal floraAnd also acknowledge possible conflict of interest
7Traditional hypothesis on emergence of AMR ConcentrationCMISelective pressure for antibiotic concentration lower than the MICTime
8Current view for the emergence and selection of resistance for the target pathogen: The selective window
9Current view for the emergence and selection of resistance No antibioticsMutation rate10-8Mutant popMutation rate10-8Wild popWith antibioticsMutation rate10-8eradicationMutants populationrésistantsusceptible
10Eradication of all bacteria Current view for the emergence and selection of resistance: with antibioticLow inoculum sizeNo mutantsWild populationUsual MICMutant MIC=MPCLarge inoculumMIC<[AB]<MPC i.e.within the selective windowLarge inoculumAB>MPCLarge inoculum with ABfew mutantsEradication of all bacteria
11Current view for the emergence and selection of resistance: The selective windowAntibiotic concentrationGrowth RGrowth SRSelectionof RSSelectiveWindow(SW)MIC mutant=MPCMICWild populationTime in SW
12MICs estimated with different inoculmum densities, relative to that MIC at 2x105 CiprofloxacinGentamicinLinezolidDaptomycinOxacillinVancomycin
13MIC & MPC for the main veterinary quinolones for E. coli & S. aureus
15Comparative MIC and MPC values for 285 M Comparative MIC and MPC values for 285 M. haemolytica strains collected from cattleMIC50MIC90MPC50MPC90MPC/MICCeftiofur0.01612125Enrofloxacine0.1250.258Florfenicol4Tilmicosine16>32≈8Tulathromycine
16Consequences of a selective window associated to an inoculum effect for a rational treatment for veterinary medicine
18The different uses of antibiotics in veterinary medicine DiseasehealthAntibiotic consumptionMetaphylaxis(Control)Prophylaxis(prevention)Growth promotionTherapyHighPathogen loadOnly a risk factorNoSmallNA
19The inoculum effect and Very Early Treatment (VET) Tested hypothesisEfficacious dosage regimen is different when the pathogen load is large, low or nullTreatment should start as early as possible
21Materials and methods Model of pulmonary infection Inoculation of Pasteurella multocida1500 CFU/lungA strain of Pasteurella multocida isolated from the trachea of a pig with clinical symptoms of a bacterial lung infection
22Materials and methods Model of pulmonary infection Inoculation of Pasteurella multocida1500 CFU/lungBacteria counts per lung (CFU/lung)Progression of infection100102104106108101018 control mice were used to assess the natural growth of Pasteurella multocida in the lungs.1020304050Time after infection (h)
23Materials and methods Late (32h) Administration anorexia lethargy dehydrationno clinical signs of infection1001021041061081010Progression of infectionBacteria counts per lung (CFU/lung)Inoculation of Pasteurella multocida1500 CFU/lung1020304050Time (h)Late (32h)Administrationearly (10h)Administration
24Materials and methods A single administration of marbofloxacin 10 hours after the infection (n=14)A single administration of marbofloxacinTwo doses tested for each group1 mg/kg and 40 mg/kg32 hours after the infection (n=14)Inoculation of Pasteurella multocida1500 CFU/lung
25Pourcentages of mice alive 1-Clinical outcome (survival) A low early dose better than a late high doseMarbofloxacin administrationsearlylate100 %8060Pourcentages of mice alive4020control1 mg/kg40 mg/kgMarbofloxacin doses
262-Bacterial eradication Early low dose= late high dose Marbofloxacin administrationsEarlyLate100 %80% of mice with bacterial eradication604020control1 mg/kg40 mg/kgMarbofloxacin doses
273-Selection of resistant target bacteria An early 1 mg/kg marbofloxacin dose has no more impact on resistance than a high late treatment while this low dose is selecting resistance when administered laterMarbofloxacin administrations50 %Earlylate40% of mice with resistant bacteriaobservation 16 hours after marbofloxacin administration= 48 hours after the infection = like early administration3020+38h101 mg/kg40 mg/kgcontrol1 mg/kg40 mg/kg+38hMarbofloxacin doses
28Metaphylaxis vs. curative Pulmonary infectious model by inhalation (P multocida)Amoxicillin & et cefquinomeTreatment during the prepatent (incubation) period (24h) vs. when symptoms are presentM V. Vasseur, A A. Ferran, M Z. Lacroix, PL Toutain and A Bousquet-Mélou,
29Effect of amoxicillin (clinical cure ) metaphylaxis vs. curative Dose mg/kg
30Effect of amoxicillin (bacteriological cure) metaphylaxis vs. curative Dose mg/kg
31Effect of cefquinome (clinical cure ) metaphylaxis vs. curative Dose mg/kg
32Effect of cefquinome (bacteriological cure) metaphylaxis vs. curative Dose mg/kg
33An early/low dose treatment is better for bacteriological cure than a late/high dose for three antibiotics: marbofloxacin, amoxicillin & cefquinome
34Q:Are we over-rating the risk of low-dose drug exposure on the selection of resistant strains? A: Apparently not for the target pathogen when an early treatment is initiated i.e when antibiotic only a low inoculum is exposed to an antibioticBut what about other non-targeted bacteria?
35The question: Are we over-rating the risk of low-dose drug exposure on the selection of resistant strains?The public health issues being critical , we have to investigate both:The case of target pathogensThe case of non-target pathogensZoonoticsCommensal floraAnd acknowledge possible conflict of interest
36Example of conflict of interest the antimicrobial treatments should not only aim at curing the diseased animals but also at limiting the resistance on non target flora.Optimal dosing for treatment ≠ optimal to prevent resistance!
37For AR, what are the critical veterinary ecosystems in terms of public health (commensals)
38The critical animal ecosystems in terms of emergence and spreading of resistance Open and large ecosystemsDigestive tractSkinOpen but small ecosystemRespiratory tractClosed and small ecosystemMammary gland
39Bacterial load exposed to antibiotics during a treatment InfectedLungsDigestivetractTesttubeManurewaste1µg1 mgSeveral KgSeveral tonsFood chainSoil, plant….
40Duration of exposure of bacteria exposed to antibiotics InfectedLungsDigestivetractManureSludgewasteTesttubeFew days24hSeveral weeks/monthsFood chainSoil, plant….
41Biophases & antibiorésistance G.I.TProximalDistalAB: oral route1-F%Gut floraZoonotic (salmonella, campylobactercommensal ( enterococcus)Résistance = public health concernFood chainEnvironmental exposureF%BloodTarget biophaseBug of vet interestRésistance = lack of efficacy
42Bioavailability of oral tetracyclins Chlortetracycline:Chickens:1%Pigs Fasted or fed: 18 to 19%Turkeys:6%Doxycycline:Chickens:41.3% .Pigs :23%Oxytetracycline:Pigs:4.8%Piglets, weaned, 10 weeks of age: by drench: 9%;in medicated feed for 3 days: 3.7% .Turkeys: Fasted: 47.6% ;. Fed: 9.4%Tetracycline:Pigs fasted:23% .
44Fluoroquinolone impact on E. coli in pig intestinal flora (From P Fluoroquinolone impact on E. coli in pig intestinal flora (From P. sanders, Anses, Fougères)IM 3 daysIVBefore treatment : E. coli R (0.01 to 0.1%)After IV. :Decrease of total E coli , slight increase of E. coli R (4 to 8 %)Back to initial levelAfter repeated IM (3d) : Decrease below LoD E. coli (2 days), fast growth (~ ufc/g 1 d). E. coli R followed to a slow decrease back to initial level after 12 days
45Genotypic evaluation of ampicillin resistance: copy of blaTEM genes per gram of feces This graph shows the average amount of fecal blaTEM genes for each mode of treatment.Treatment had a significant effect on the excretion of blaTEM genes, and oral administration to fed pigs led to a higher excretion of blaTEM genes than the intramuscular administration.treatment=“tritment”led=“laide”A significant effect of route of administration on blaTEM fecal elimination (p<0.001).
46Performance-enhancing antibiotics (old antibiotics) chlortetracycline, sulfamethazine, and penicillin (known as ASP250)]phylogenetic, metagenomic, and quantitative PCR-based approaches to address the impact of antibiotics on the swine gut microbiota
47It was shown that antibiotic resistance genes increased in abundance and diversity in the medicated swine microbiome despite a high background of resistance genes in nonmedicated swine.Some enriched genes, demonstrated the potential for indirect selection of resistance to classes of antibiotics not fed.
48Ecological consequences of the commensal flora exposure by antibiotic
49one world, one healthTransmissible genetic elements allow antibiotic resistance genes to spread both to commensal bacteria and to strains that cause disease.Vet ABCommensal floraZoonotic pathogensGene of resistanceResistance is contagious!It will continue to spread even after infection has been cleared
50One world, one health Greening our AB Commensal flora Environment Genes of resistance(zoonotic pathogens)EnvironmentFood chainAMR should be viewed as a global ecological problem with commensal flora as the turntable of the system
51Selectivity of antimicrobial drugs in veterinary medicine PDNarrow spectrumPKSelective distribution of the AB to its biophase
52Innovation: PK selectivity of antibiotics ProximalDistal1-F=90%OralGut floraZoonotic (salmonella, campylobactercommensal ( enterococcus)EffluxF=10%Food chainQuinolones, macrolidesenvironmentIMBloodKidneyBiophaseRésistance = public health concernAnimal health
53Currently no veterinary antibiotic is selective of target pathogens and our hypothesis was that a low dose would be more selective than a high, regular, dose
54In vitro assessment of the selectivity of antibiotics on the target pathogen vs. commensal flora: eradication of a low vs. high inoculum size of P multocida
55Selectivity of amoxicillin & cefquinome Using killing curves selectivity was tested using E.coli, as a commensal bacterium in condition for which the two tested antibiotics were able to eradicate a low or a large inoculum of P.multocida,
57P. Multocida (105 or 107 CFU/ml) Selectivity of amoxicillin to eradicate a low a or a high inoculum size of P. multocidaLow: 105 CFU/mLHigh:107 CFU/mLSI=51SI=5.54P. Multocida (105 or 107 CFU/ml)E coli (107 CFU/mL)
58P. Multocida (105 or 107 CFU/ml) Selectivity of cefquinome to eradicate a low a or a high inoculum size of P. multocidaLow:105 CFU/mLHigh:107 CFU/mLSI=2.9SI=0.66P. Multocida (105 or 107 CFU/ml)E coli (107 CFU/mL)
59I there a selective window for the commensal flora
60All macrolides are not equals The normal flora is disturbed more or less according to the pharmacokinetic profiles of the respective macrolides.85% of patients treated with azithromycin were colonized by macrolide-resistant organisms 6 weeks after therapy, compared to 17% treated with clarithromycin
61Effect of Elimination Kinetics on Bacterial Resistance 10.001.000.10.010.001ClarithromycinAzithromycinSelective WindowConcentration ( ug/ml )MICMACWeeksLonger half-life antibiotics may create a greater windowof opportunity for the development of resistanceGuggenbichler JP, Kastner H Infect Med 14 Suppl C: (1997)
62Selective window can be longer and delayed in the GIT GIT/commensalPlasma/Lung
63A formulation property A long half-life is desirable for convenience in vet medicine: two possible optionsLong HLA substance propertyLow clearanceHigh MWlipophilicLikely lower degradabilityExcretion by the GITLarge volume of distributionLarge diffusionA formulation propertySlow absorption(flip-flop)High clearancehydrophilicLikely higher degradabilityExcretion by the kidneyMacrolides/FQBeta-lactams/sulfonamides
64Longer half-life antibiotics may create a greater window of opportunity for the development of resistance
65One size does NOT fit all! ConclusionsOne size does NOT fit all!We need to broaden the concept of selection of resistance when devising optimal dosing strategies – both for guidelines for future and existing antibiotics
66When to finish a treatment? ASAPShould be determined in clinicsShould be when clinical cure is actually achievedShould not be a hidden prophylactic treatment for a possible next infectious episode
67ConclusionFor a same dose of marbofloxacin, early treatments (10 hours after the infection) were associated tomore frequent clinical curemore frequent bacteriological cureless frequent selection of resistant bacteriathan late treatments (32 hours after the infection)Early administrations were more favourable than late administrations
68Normal flora: Consequences Treatment exerts selection on innocent bacteriaMost of the harm done by use of a drug may be on species OTHER than the target of treatmentMost of the exposure of a givenspecies to a given drug may bedue to treatment of OTHERinfections
69One world, one health Commensal flora Vet AB Hazard Environment Genes of resistancezoonotic pathogensEnvironmentFood chainAMR should be viewed as a global ecological problem with commensal flora as the turntable of the system
70New Eco-Evo drugs and strategies should be considered in vet medicine
72Innovation: PK selectivity of antibiotics Trapping or destruction of the antibioticG.I.TProximalDistalEfflux90%0%Gut floraZoonotic (salmonella, campylobactercommensal ( enterococcus)Food chainQuinolones, macrolidesenvironmentIMBloodKidneyBiophaseRésistance = public health concernAnimal health
73My view of an ideal antibiotic for vet medicine High plasma clearanceRapidly metabolized (in vivo, environment) to inactive metabolite(s)High renal clearanceElimination by non-GIT route (not bile or enterocyte efflux)volume of distribution not too highPathogens are extracellular; half-life rather short; not too short to compensate a relatively high clearanceHigh bioavailability by oral routeTo avoid to expose distal GIT to active ABLow binding to plasma proteinOnly free antibiotic is active; to reduce the possible nominal dosage regimen and environmental loadHigh binding to cellulosisTo inactivate AB in large GITHigh potencyTo be able to select a low doseHigh PK selectivity (biophase)To distribute only to target biophase
74Innovation pour une voie systémique Tractus digestifProximalDistalfloreZoonotiques (salmonella, campylobacter )commensaux ( enterococcus)Elimination par efflux ou biliaire=0%Chaîne alimentaireAdministrationEnvironmentsangBiophasePathogène viséElimination rénale=100%
75Renal clearance of different quinolones Drugs% of total clearanceOfloxacin70Levofloxacin65Ciprofloxacin50Sparfloxacin13Grepafloxacin10Trovafloxacin5-10Hooper DC CID 2000;30:
76ConclusionsAppropriate use of antibiotics should not only include knowledge of the pathogen and its susceptibility, but also the spectrum and pharmacokinetic properties of the respective antimicrobial drug.