Interpretative reading of the antibiogram Luis Martínez-Martínez Service of Microbiology University Hospital Marqués de Valdecilla Santander, Spain
ANTIBIOGRAM RESISTANCE SUSCEPTIBILITY ANTIMICROBIAL AGENT TOXICITY PK/PD MICRO- ORGANISM VIRULENCE MECHANISMS OF DEFENSE PATIENT
Description of mechanisms of resistance Introduction into clinical practice Relationship between resistance and therapeutic failure Susceptibility testing standardization Automation and expert systems Interpretative reading Interpretative criteria Discovery of antimicrobial agents 1920 1930 1940 1950 1960 1970 1980 1990 2000
Antibiogram Reading Ø Inh. zone (mm) MIC (mg/l) S-I-R
Clinical Categories CLSI (NCCLS): Clinical and Laboratory Standards Institute EUCAST: European Committee on Antimicrobial Susceptibility Testing SFM: Société Française de Microbiologie BSAC: British Society for Antimicrobial Chemotherapy MENSURA: Mesa Española de Normalización de la Sensibilidad y Resistencia a los Antimicrobianos...
Patrice Courvalin. Interpretative reading of antimicrobial susceptibility test. ASM News 1992, 58:368-375.
ANTIBIOGRAM Interpreative reading of the antibiogram Phenotype - Resistance Susceptibility testing results for a concrete microorganism considering a GROUP of antimicrobial agents (usually of the same family)
ANTIBIOGRAM Interpreative reading of the antibiogram 1.- Define Phenotype of susceptibility and Resistance 2.- Deduce the possible mechanism of resistence 3.- Adequate Clinical Categories to the inferred mechanism of resistance, and change phenotype if necessary
ANTIBIOGRAM Interpreative reading of the antibiogram S-I-R Microbiological Knowldge CLINCAL REPORT OF RESULTS
AES S-I-R SOFTWARE (Expert system) CLINCAL REPORT OF RESULTS
INTERPRETATION
[Not available in English!]
[Not available in English!]
Interpreative reading Identification of the microorganism (To species level)) Analysis of susceptibility/resistance Phenotype - Groups (families) of antimicrobial agents - Antimicrobial indicators of resistance Define Phenotype - Common Phenotypes - Unusual Phenotypes - Impossible Phenotypes Deduce biochemical mechanism of resistance Clinical Relevance of the inferred resistance Re-define Clinical Categories
Requirements of Interpretative reading of the antibiogram Identification of the microorganism Analysis of S/I/R phenotype Use of indicator agents Study antibiotic-inhibitor combinations Quantitative study of susceptibility Use of high inocula (in some occasions) Local epidemiology information Availability of reference methods R. Cantón. Enferm Infecc Microbiol Clin 2002; 20: 176-186
Microorganism Identification + antibiogram Antibiogram Interpretation Clinical Relevance of the mechanism of resistance Deduce Phenotype of Resistance Deduce Biochemical Mechanism of Resistance Re-Define Clinical Categories, if necessary REPORT Deduce susceptibility/resistance to non tested antimicrobial agents
Livermore D et al JAC 12001, 48 Suppl 1, 87-102
Livermore D et al JAC 12001, 48 Suppl 1, 87-102
Livermore D et al JAC 12001, 48 Suppl 1, 87-102
Livermore D et al JAC 12001, 48 Suppl 1, 87-102
Livermore D et al JAC 12001, 48 Suppl 1, 87-102
Livermore D et al JAC 12001, 48 Suppl 1, 87-102
Livermore D et al JAC 12001, 48 Suppl 1, 87-102
K. pneumoniae K. pneumoniae ESBL (+)
CPM CPM CTX IMP CAZ CTX IMP CAZ AMP AMP Enterobacter cloacae
SHV-12 IN Enterobacter
Klebsiella pneumoniae CMY-2 Mueller- Hinton Cloxacillin 250 mg/l Mueller-Hinton
MβL
Staphylococcus aureus P E E OX erm AK Macrolides-14 R -15 R -16? PBP2a CN APH(2 )-AAC(6 ) ß-lactam R Aminoglicosyde R
S. aureus E DA DA E DA E erm Inducible methylase erm constitutive methylase msra-b Active efflux
qnrs-producing Enterobacter cloacae REP-PCR REP-PCR pattern A B C D E Isolates number 14 4 2 1 1 MIC nalidixic acid (mg/l) >256 (R) 8 (S) 8-16 (S) >256 (R) 32 (R) MIC ciprofloxacin (mg/l) >32 (R) 0.38 (S) 2-4 (I/R) 3 (R) 1.5 (I) Mutations in gyra Ser83Ile (14) Asp87Asn (1) None None Ser83Phe None Mutations in parc Ser80Ile (2) Not done (12) Not done None Not done None Cano ME et al, submitted
Enterobacteriaceae COLISTIN RESISTANCE Calvo J et al unpublished results
Limitations to interpretative reading of the antibiogram High complexity of resistance mechanisms Limited information about some mechanisms of resistance Low level resistance Multifactorial multiresistance Oversimplification of interrpetative reading Mistakes when deducing mechanisms of resistance Modified from: R. Cantón. Enferm Infecc Microbiol Clin 2002; 20:176-186
Benefits of the interpretative reading of the antibiogram Adequacy of antimicrobial therapy Detection of new mechanisms of resistence Analysis of epidmeiology of resistance Antimicrobial policy Improved quality in laboratory testing Modified from: R. Cantón. Enferm Infecc Microbiol Clin 2002; 20:176-186