Should we test Clostridium difficile for antimicrobial resistance? Paola Mastrantonio Department of Infectious Diseases Istituto Superiore di Sanità, Rome,Italy
Clostridium difficile infection (CDI) (first steps leading to colonization) antibiotic use disturbance of the intestinal flora exogenous source colonization by C.difficile endogenous source
Main effects of antibiotics they kill or inhibit the targeted pathogen they affect the host microbiota endogenous microbiota microbiota antibiotic
Relationship between hospital exposure, intestinal microbiota and risk factors for CDI
Main antimicrobials inducing CDI Macrolides and lincosamides Broad-spectrum penicillins Third generation cephalosporins Fluoroquinolones **
Does the choice of drug for treatment of CDI matter? Which patients should be treated? Which antibiotic should be used?
Actions traditionally recommended Discontinue therapy with the inciting antimicrobial agent as soon as possible When severe or complicated CDI is suspected, initiate empirical treatment Metronidazole as the drug of choice for the first episode of mildto-moderate CDI Vancomycin as the drug of choice for a first episode of severe CDI Treatment of the first recurrence is usually with the same regimen as for the first episode but should be stratified by disease severity Treatment of the second or later recurrence with vancomycin using a tapered and or pulse regimen is the preferred strategy Suggested guidelines: M. P. Bauer, E. J. Kuijper and J. T. van Dissel. Clin.Microbiol Infect 2009; 15: 1067 1079
Antimicrobial therapy for the management of CDI is often empirical and culture results when available are reported to the clinician some time after the beginning of antimicrobial therapy low frequency of testing in the clinical laboratories is due in part to: the lack of expertise the lack of systematic culture in many labs the lack of appropriate clinical breakpoints results are unlikely to influence treatment
Current issues MZ and Vanco resistance was considered anedoctal for a long time but in the middle of 90s an alarm was sounded from Spain with 6% of MZ resistant strains A few reports underline the detection of isolates with an increased MIC value to metronidazole or showing heteroresistance, but the clinical significance is unknown For vancomycin, a very limited but persistent number of strains have been described with a reduced susceptibility
T. Pela ez,et al. Metronidazole Resistance in Clostridium difficile is Heterogeneous J. Clin Microbiol, 2008, 46,(9),3028 32 Presence of pinpoint colonies around a 5 μg MZ disk or Etest strip
By CLSI-recommended reference agar dilution method for anaerobes(m11-a7) MZ breakpoints are: < 8 μg/ml susceptible 16 μg/ml intermediate > 32 μg/ml resistant ----------------------------------------------------------------------------------------------- Vanco breakpoints are not provided for anaerobes but there is a wide consensus on the following MIC values: < 2 μg/ml susceptible 4 to 16 μg/ml intermediate > 16 μg/ml resistant
EUCAST MIC distribution for Clostridium difficile Agent 0.002 0.004 0.008 0.016 0.03 0.06 0.12 0.25 0.5 MIC (mg/l) Amoxicillin 0 0 0 0 11 14 37 53 148 328 69 12 0 1 1 1 0 0 0 Amoxicillinclavulanic acid 0 0 0 0 0 0 2 13 145 164 29 10 2 0 0 0 0 0 0 Cefuroxime 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 19 646 0 Ciprofloxacin 0 0 0 0 0 0 0 0 0 0 0 0 79 143 13 63 59 171 0 Clindamycin 0 0 0 1 4 7 11 19 47 88 420 618 462 79 9 13 7 382 23 Daptomycin 0 0 0 0 1 2 9 21 38 90 39 6 0 0 0 0 0 0 0 Ertapenem 0 0 0 0 0 0 0 0 0 0 12 154 103 7 0 0 0 0 0 Erythromycin 0 0 0 0 0 5 5 49 245 579 139 12 9 19 7 4 2 442 231 Fusidic acid 0 0 0 0 3 71 181 312 322 171 37 0 0 0 0 0 0 5 0 Imipenem 0 0 0 0 0 0 0 0 2 0 12 145 127 0 0 0 0 0 0 Linezolid 0 0 0 0 0 0 1 8 50 111 30 13 1 1 0 0 0 0 0 Meropenem 0 0 0 0 0 0 1 1 8 99 376 85 13 0 1 0 0 0 0 Metronidazole 0 0 0 2 72 374 592 455 329 46 31 1 0 0 0 1 0 0 0 Moxifloxacin 0 0 0 0 0 0 0 15 323 318 297 24 20 175 267 45 2 0 0 Piperacillin 0 0 0 1 1 0 0 0 1 0 17 225 393 173 72 22 3 22 0 Piperacillintazobactam 0 0 0 0 0 0 0 0 0 0 16 168 301 56 15 2 0 0 0 Rifampicin 337 2 0 0 1 0 0 0 4 1 0 0 0 0 7 5 9 0 0 Teicoplanin 0 0 0 1 29 204 147 18 2 0 0 0 0 0 0 0 0 0 0 Tetracycline 0 0 4 2 400 409 77 12 6 9 16 46 38 15 24 13 2 25 0 Tigecycline 0 0 0 17 216 278 33 8 0 0 0 0 0 0 0 0 0 0 0 Vancomycin 0 0 0 0 0 0 0 44 1229 653 76 9 3 1 0 0 0 0 0 Susceptible Resistant ECOFF (mg/l) (mg/l) (mg/l) Comment Metronidazole 2 >2 2 Breakpoint based on ECOFF. Vancomycin 2 >2 2 Breakpoint based on ECOFF. Fusidic acid - - 2 No clinical breakpoint. Resistance develops rapidly. May be tested for epidemiological purposes only. Moxifloxacin - - 4 No clinical breakpoint. May be tested for epidemiological purposes only. Rifampicin - - 0.004 No clinical breakpoint. May be tested for epidemiological purposes only. Tentative ECOFF as few MIC distributions Tigecycline - - 0.25 No clinical breakpoint. May be tested for epidemiological purposes only. 1 2 4 8 16 32 64 128 256 512
Agar dilution (CLSI) E test The methods Need to harmonise breakpoints between CLSI and EUCAST and standardize susceptibility testing methods http://www.eucast.org/mic_distributions/ (link to the website with MIC distributions)
T. Pelàez et al. 2002 Reassessment of C. difficile susceptibility to metronidazole and vancomycin Antimicrob. Agents Chemother. 46:1647-1650
S. D. Baines et al. 2008 Emergence of reduced susceptibility to metronidazole in C. difficile J. Antimicrob. Chemother.62:1046-1052 Changes in susceptibility pattern to MZ may be missed by some methods: 24.4% of PCR ribotype 001 isolates with a reduced susceptibility only by using the spiral gradient endpoint method 3.51 μg/ml for ribotype 001 1.11 μg/ml for ribotype 106 0.90 μg/ml for ribotype 027
MIC breakpoints for bacteria causing systemic infections are based upon levels of antibiotic in blood whereas in CDI MIC breakpoints should be based on faecal levels Increased MIC-values to metronidazole in vitro may be of clinical relevance as it is known that this drug may not achieve high concentrations in the gut lumen: mean concentrations range from 0.25 to 9.5 mg/l (Gut 1986,27:1169-72) Decreased vancomycin susceptibility is considered less of a clinical issue as high drug concentrations are normally achieved in the gut lumen after oral administration (BMC Infect. Dis 2010,10:363) **
1. Should we test Clostridium difficile for antimicrobial resistance? for the patient s therapy? to which antibiotics?
Antibiotics for therapy Metronidazole bactericidal Vancomycin bacteriostatic Rifaximin (nonabsorbable oral antibiotic used for primary and recurrent episodes) broad spectrum Fusidic acid ( a bacterial protein syntesis inhibitor) broad spectrum Tigecycline (a glycylcycline structurally related to minocycline) broad spectrum Ramoplanin (poorly absorbed glycolipodepsipeptide) broad spectrum Tinidazole (structural analogue of Mz ) broad spectrum Nitazoxanide (a thiazolide derivative) broad spectrum Fidaxomicin (an 18-membered macrocycle with a narrow spectrum of activity) bactericidal, narrow-spectrum
In vitro susceptibility to 17 antimicrobials of clinical C. difficile isolates collected in 1993-2007 in Sweden T. Norén et al. Clin. Microbiol. Infect 2010,16:1104-1110
Pros and Cons of susceptibility testing Increased circulation of strains with MIC to MZ above 2μg/ml Detection of strains with heteroresistance to MZ Increased failure rates with the standard metronidazole therapy Recognition of rifaximin resistance x Late answers from the labs (at least 72h) x Results of a list of antibiotics may be confounding for the choice by the clinician
Perform the test : suggestions When the CDI is severe and antibiotic other than vancomcyin are considered If the clinical course does not improve during treatment In presence of an outbreak In the recurrences In a select sample of C. difficile isolates to monitor year by year the trend of antibiotic susceptibility in the hospital & **
2. Should we test Clostridium difficile for antimicrobial resistance? to the main antibiotic inducers of CDI? to which aims?
Main Inciting Antibiotics MLSB antibiotics: - Erythromycin - Clindamycin β-lactam antibiotics : - Cephalosporins - Amoxicillin + clavulanic acid - Piperacillin/tazobactam - Penicillin Fluoroquinolones: - Ciprofloxacin - Moxifloxacin - Levofloxacin
Percentages of resistance in 354 C. difficile strains isolated from 38 different hospitals in 14 EU countries in the Prospective Study 2005-2006 (Barbut F et al. Clin Microbiol Infect 2007; 13: 1048 1057) 44,4 37.5 46.1 Breakpoints of resistance: EM, CM, MX >4 mg/l; TC > 8 mg/l 9.2
Antimicrobial susceptibility in Chinese C. difficile strains collected in the years 2008-2009 (Anaerobe 2010,16:633-35) **
Is there a role of antimicrobial resistance in the spread of epidemic PCR ribotypes of Clostridium difficile?
Table 3. Frequencies of resistance (%) in the 10 most common ribotypes and other rare ribotypes (1613 isolates tested). (Wiuff C. et al. J. Infect 2011. 62, 271-279) % Resistance clindamycin erythromycin levofloxacin moxifloxacin cefotaxime 106 (n = 475) 97.3 99.6 99.4 98.9 96.4 001 (n = 355) 96.6 96.9 96.3 96.3 93.8 027 (n = 204) 97.5 100 100 99.5 85.3 002 (n = 101) 95.0 1.0 1.0 1.0 71.3 015 (n = 57) 98.2 3.5 0 0 56.1 014 (n = 52) 96.2 1.9 1.9 0 57.7 078 (n = 46) 100 21.7 8.7 6.5 54.3 005 (n = 45) 100 6.7 6.7 6.7 84.4 023 (n = 39) 94.9 2.6 5.1 2.6 79.5 020 (n = 27) 100 3.7 3.7 0 63.0 Other (rare) (n = 212) 92.9 24.4 10.8 7.1 61.3 All isolates 96.6 67.6 65.3 64.4 83.1 (breakpoints of resistance: EM, CM, MX,LE >8 mg/l) **
suggestions monitor the resistance patterns of select samples of strains for the correlation with specific antibiotic policy in the hospital (antibiotic stewardship) perform the susceptibility tests time to time to detect changes in the circulation of specific genotypes
Conclusions on antibiotic susceptibility testing on C. difficile 1. The importance of culturing C. difficile 2. The need to apply standardized methods 3. Selection of those cases of CDI for which the susceptibility test is useful to choose the most appropriate treatment 4. Samples of strains to be tested to monitor the resistance trend should be representative of CDI throughout the hospital setting and over time