Extremely Drug-resistant organisms: Synergy Testing

Transcription

1 Extremely Drug-resistant organisms: Synergy Testing Background Acinetobacter baumannii& Pseudomonas aeruginosa Emerging Gram-negative bacilli Part of the ESKAPE group of organisms 1 Enterococcus faecium Staphylcoccus aureus Klebsiella pneumoniae Acinetobacter baumannii LIM TZE PENG Principal Pharmacist Singapore General Hospital Pseudomonas aerugionosa Enterobacter spp. 1. Helen W. Boucher, Bad Bugs, No Drugs: No ESKAPE! An Update from the Infectious Diseases Society of America. Clin Infect Dis 2009; 48:1-12 Definitions Definitions What is the difference between MDR XDR What is the difference between Synergistic PDR Bactericidal Inhibitory Antagonistic 1. Magiorakos, A. P., A. Srinivasan, et al. (2011). "Multidrug-resistant, extensively drug-resistant and pandrug-resistant bacteria: an international expert proposal for interim standard definitions for acquired resistance." Clin Microbiol Infect.

2 Typical MIC profile Potential solutions Strain Antibiotic Ampicillin/Sulbactam 32/16 32/16 64/32 32/16 32/16 Ciprofloxacin Gentamicin Imipenem Meropenem Aztreonam Piperacillin/Tazobactam Polymyxin B Tigecycline Ceftazidime Amikacin Cefepime Rifampicin Decreasing new antibacterials approved for use Only 2 new antibacterialsin the last 6 years Doripenem (2007), Ceftaroline(2013) Multi-pronged approach Judicious use of existing agents Efficient infection control Antimicrobial Stewardship Program Combination therapy Combination therapy Often used in clinical practice TB & HIV Increasingly used in MDR A. baumannii& P. aeruginosa Enhanced pharmacodynamic effect (synergism) Enhanced bactericidal effect Suppress emergence of resistance 1. Maragakis LL, Perl TM. Acinetobacter baumannii: epidemiology, antimicrobial resistance, and treatment options. Clin Infect Dis Apr 15;46(8):

3 Types of combination studies Fractional Inhibitory Concentration Index Various methodologies Checkerboard method Time-kill studies In-vitro pharmacodynamic models Synergy: FIC index < 0.5 Additive: FIC index = 1 Antagonism: FIC index > 4 1. Hsieh MH, Yu CM, Yu VL, Chow JW. Synergy assessed by checkerboard. A critical analysis. Diagn Microbiol Infect Dis May- Jun;16(4): Limitations of FIC index Time-kill studies (TKS) Based on Loewe additivity Assume similar & linear concentration-time relationship Subjective endpoints Cloudy vs Clear wells Antibiotic synergy: 2 log decrease in cfu/ml 1. National Committee for Clinical Laboratory Standards Methods for Determining Bactericidal Activity of Antimicrobial Agents. Approved Guideline M26-A., vol. 19. NCCLS, Wayne, PA, USA

4 Limitations of TKS Clinical relevance Hollow-Fiber System Drug 24 hour endpoint At least one of the drugs must be present in a concentration which does not affect the growth curve of the test organism when used alone. 1 Pharmacokinetic factors ignored Distribution bacteria Elimination Resource management Labour & Time intensive 1. Antimicrobial Agents & Chemotherapy: Instructions to Authors Hollow-fiber infection model allowing simulation of human PK in vitro. (Tam, JID 2007) Aims To elucidate efficacious antibiotic combinations against PDR A. baumannii Methods Time-kill studies (TKS) Maximal clinically achievable concentrations Hollow Fiber Infection Model (HFIM) In-vivo environment simulation

5 Susceptibility results Antimicrobial TTSH 112 (mg/l) TTSH 105 (mg/l) SGH 8879 (mg/l) Meropenem 32 (R) 64 (R) >32 (R) Polymyxin B 1 (S) 1 (S) 2 (S) Rifampicin Tigecycline 4 (I) 0.5 (S) 2 (S) 1 There are currently no international standards for rifampicin and susceptibility testing against Acinetobacter baumannii Pharmacokinetic Data Antimicrobial Simulated FREE drug conc (mg/l) Maximum clinical achievable FREE drug conc (mg/l) Corresponding maximum clinical dose TKS SGH AB 8879 Meropenem (plasma) 2g q8h over 3h infusion Polymyxin B 2 2 (plasma) At least 1 MU q12h Microbiological responses of AB against various antibiotics Microbiological responses of AB against various antibiotic combinations Rifampicin 2 2 (plasma) PO 600mg q12h Tigecycline 2 2 (tissues) 100mg q12h 1. Jaruratanasirikul S, et al. Comparison of the pharmacodynamics of meropenem in patients with ventilator-associated pneumonia following administration by 3-hour infusion or bolus injection. Antimicrob Agents Chemother Apr;49(4): Kwa AL, Lim TP, Low JG, Hou J, Kurup A, Prince RA, Tam VH. Pharmacokinetics of polymyxin B1 in patients with multidrug-resistant Gramnegative bacterial infections. Diagn Microbiol Infect Dis Feb;60(2): Epub 2007 Oct Gumbo T, Louie A, Deziel MR, Liu W, Parsons LM, Salfinger M, Drusano GL. Concentration-dependent Mycobacterium tuberculosis killing and prevention of resistance by rifampin. Antimicrob Agents Chemother Nov;51(11): Epub 2007 Aug Rodvold KA, Gotfried MH, Cwik M, Korth-Bradley JM, Dukart G, Ellis-Grosse EJ. Serum, tissue and body fluid concentrations of tigecycline after a single 100 mg dose. J Antimicrob Chemother Dec;58(6):

6 Objective To evaluate the efficacy of : Polymyxin B and Rifampicin or PolymyxinB and Tigecycline or Tigecycline and Rifampicin combined against PDR AB from our local hospitals. Methods Bacteria 361 AB strains collected from National Antimicrobial Resistance, Singapore MIC testing (microtitre) 31 PDR AB with OXA-23, OXA-51 b-lactamases & ISAba1 OXA complex Time-kill studies performed with the 31 PDR AB strains Baseline inoculums of 5 log 10 CFU/ml Pharmacokinetic Data Antimicrobial Simulated FREE drug conc (mg/l) Polymyxin B 2 (serum trough) Corresponding maximum clinical dose At least 1 MU q12h Rifampicin 2 (serum peak) PO 600mg q12h Tigecycline 2 (tissue peak) 100mg q12h Kwa AL, Lim TP, Low JG, Hou J, Kurup A, Prince RA, Tam VH. Pharmacokinetics of polymyxin B1 in patients with multidrug-resistant Gram-negative bacterial infections. Diagn Microbiol Infect Dis Feb;60(2): Epub 2007 Oct 4. Gumbo T, Louie A, Deziel MR, Liu W, Parsons LM, Salfinger M, Drusano GL. Concentration-dependent Mycobacterium tuberculosis killing and prevention of resistance by rifampin. Antimicrob Agents Chemother Nov;51(11): Epub 2007 Aug 27. Rodvold KA, Gotfried MH, Cwik M, Korth-Bradley JM, Dukart G, Ellis-Grosse EJ. Serum, tissue and body fluid concentrations of tigecycline after a single 100 mg dose. J Antimicrob Chemother Dec;58(6):

7 Combination timekill MIC results (31 PDR AB strains) Susceptibility (%) Antibiotics MIC 50 (mg/l) MIC 90 (mg/l) Range (mg/l) R I S 2 log decrease in cfu/ml from original inoculum Antibiotic synergy: 2 log decrease in cfu/ml Polymyxin B Rifampicin Tigecycline Resistant to all antibiotics Single TKS results 24 hour mean bacteria burden after exposure to various antibiotics alone (1-2 log reductions strains denoted in red) AB strain Starting inocula Tigecycline Polymyxin B Rifampicin Mean Mean Mean Single TKS results (continued) 24 hour mean bacteria burden after exposure to various antibiotics alone (1-2 log reductionstrains denoted in red) AB strain Starting inocula Tigecycline Polymyxin B Rifampicin Mean Mean Mean

8 Combination TKS results 24 hour mean bacteria burden after exposure to various antibiotic combinations (modifiedbactericidal combinations denoted in red, 1-2 log10 reduction in yellow) AB strain Starting inocula Tigecycline + Rifampicin Polymyxin B + Rifampicin Polymyxin B + Tigecycline Mean Mean Mean Combination TKS results (continued) 24 hour mean bacteria burden after exposure to various antibiotic combinations (modifiedbactericidalcombinations denoted in red, 1-2 log 10 reduction in yellow) AB strain Starting inocula Tigecycline + Rifampicin Polymyxin B + Rifampicin Polymyxin B + Tigecycline Mean Mean Mean Time-Kill Results Polymyxin B alone 6 out of 31 strains showed a reduction of 1-2 log 10 CFU/ml in bacterial density compared to baseline at 24 hrs 25 out of 31 strains show insignificant reduction (< 1 log 10 CFU/ml)or higher inoculums (approx 8 log 10 CFU/ml) at 24 hrs Tigecycline or rifampicin alone Either < 2 log 10 CFU/mldrop at 24 hrs from baseline inoculums for 2 & 1 strain(s) in tigecycline & rifampicin respectively Or increase of > 2 log 10 CFU/mlat 24 hrs from baseline inoculums Combination Time-Kill Results Polymyxin B+ rifampicin 14 out of 31 strains achieve >2 log10 CFU/ml decrease from baseline inoculum, at 24 hrs Polymyxin B + tigecycline 10 out of 31 strains Tigecycline + rifampicin 8 out of 31 strains

9 Time-Kill Results None of the antibiotics combinations demonstrated modified bactericidal activity against 14 out of 31 strains Polymyxin + rifampicin, polymyxin +tigecycline demonstrated 1-2 log 10 CFU/ml reduction in 5 & 4 strains respectively from baseline at 24hr. Total 6 (28,59, 69, 70, 138, 170) Tigecycline + rifampicin is at least additive in 7 strains (23, 104, 174, 14101, 3160, 13631, 48038) Polymyxin + rifampicin is additive to 1 strain (41) Polymyxin alone demonstrated the lowest bacteria burden for 5 strains (23, 174, 3160, 13631, 48038) at 24 hr ~ log 10 CFU/ml TKS results 24 hour mean bacteria burden after exposure to various antibiotic combinations (modifiedbactericidalcombinations denoted in red, 1-2 log 10 reduction in yellow) AB strain Tigecycline + Rifampicin Polymyxin B + Rifampicin Polymyxin B + Tigecycline Mean Mean Mean HFIM Pharmacokinetic/Pharmacodynamic Modelling of Polymyxin B, Rifampicin and Tigecycline against Pandrug-resistant Acinetobacter baumannii in an In-vitro Model T.P. Lim 1, T.Y. Tan 2, W. Lee 1, Sasikala. S. 2, T.T. Tan 1, L.Y. Hsu 3, A.L. Kwa 1 1 Singapore General Hospital, 2 Changi General Hospital. 3 National University Hospital 2 representative strains used to validate the results in hollow-fiber infection model (HFIM) TTSH AB 112 SGH AB 8879 ECCMID 2010, Vienna, Austria

10 HFIM results HFIM results Polymyxin B regimen simulated Polymyxin B resistant isolates plated on drug-supplemented media at 3X MIC Placebo Polymyxin B 1MU q12h Log CFU/ml Days Rifampicin 600mg q12h Tigecycline 100mg q12h Polymyxin B 1MU q12h + Rifampicin 600mg q12h Polymyxin B 1MU q12h + Tigecycline 100mg q12h Tigecycline 100mg q12h + Rifampicin 600mg q12h Antibiotic Combinations against MDR Bacteria Trial and Error Countless permutations Different combinations effective for different strains 1 Certain combinations may lead to antagonism 2,3 Guided by in-vitro Testing Avoid use of antagonistic combinations Identify effective combinations 1. Lim TP et al. (2009) I Antibiot (Tokyo). 2. Aaron SD et al, (2000). Am J RespirCrit Care Med 161: Lang BJ et. al (2000). Am J Respir Crit Care Med 162:

11 Methodology Advantages Limitations MCBT method TK method Time-kill(TK) method Multiple Combination Bactericidal Testing (MCBT) method Gold-standard Measures bactericidal activity Describes extent of kill over 24 hours Fast turn-around time Large no. of antibiotic combinations tested Time-consuming Limits no. of combinations tested Need for repetitive sampling Results likely retrospective in nature Novel method Limitations not fully elucidated Preparation of microtiter Preparation plates of Addition of one or two microtiter antibiotic(s) to well plates Prepared in bulk and stored till required Inoculation of bacteria Inoculation of Bacteria at standard bacteria concentration added More than 80 combinations tested Sampling and plating of bacteria Sampling and Preliminary results plating (based of bacteria on turbid wells) Contents of wells sampled and plated Day -1 Day 0 Isolates received Day 1 Preparation of drugs /Inoculating bacteria Addition of one/two Preparation antibiotics of drugs/ to flasks Inoculating bacteria Standard concentration of bacteria added Up to 20 flasks tested Sampling and plating of Sampling bacteria and plating Contents of flasks sampled of bacteria and plated Bacteria Counts Counts enumerated Bacteria based Counts on growth on plates Day 2 Bacteria Counts Counts enumerated Bacteria based on Counts growth on plates TIME-LINE POLYMYXIN + RIFAMPICIN POLYMYXIN + TIGECYCLINE POLYMYXIN + AZTREONAM RIFAMPICIN + TIGECYCLINE MEROPENEM +AZTREONAM AZTREONAM + LEVOFLOXA CIN POLYMYXIN + MEROPENEM MEROPENEM + AZTREONAM RIFAMPICIN + MEROPENEM LEVOFLOXACIN + TIGECYCLINE ACI BAUMAN Thank You! Legend At least inhibitory No utility