Antimicrobial Susceptibility Systems HiMediaLaboratories™ himedialabs.com HiCrome™ Mueller Hinton Agar (M2010) With dual advantage Chromogenic Identification + Antimicrobial Susceptibility » Chromogenic differentiation of significant urinary tract pathogens » Simultaneous detection of susceptibility to antimicrobials » Rapid and reliable results in 24 hours as compared to traditional method which takes 48 hours for organism identification and antimicrobial susceptibility F o r A ty nt ili iba tib cterial Suscep Index Introduction ........................................................................................................................ 2 Parameters Affecting Performance of Susceptibility Disc .................................... 3 Technique ............................................................................................................................. 4 Single Disc (SD) ................................................................................................................... 5 Multi Discs ............................................................................................................................. 21 Hexa Discs (HX) .................................................................................................................... 22 Octo Discs (OD) .................................................................................................................... 28 Dodeca Discs (DE) ............................................................................................................... 36 Icosa Discs (IC) ..................................................................................................................... 42 HiComb™ MIC Test Strips (MD) ....................................................................................... 44 Quality Control ................................................................................................................... 49 Guidelines/Notes / Precautions .................................................................................... 50 Applicator ............................................................................................................................. 51 Disc Dispenser .................................................................................................................... 52 Antibiotic Zone Scale ........................................................................................................ 53 Zone Size Interpretation Chart ...................................................................................... 54 HiComb™ Interpretation Chart ...................................................................................... 65 Ezy MIC™ Strips (EM) .......................................................................................................... 70 Abbreviations : CLSI - Clinical & Laboratory Standards Institute NCCLS - National Committee for Clinical Laboratory Standards EUCAST - European Committee on Antimicrobial Susceptibility Testing 1 Introduction Antimicrobial Susceptibility – Guidelines for Testing Introduction discrete concentration of the antimicrobial agents. The main objective of antimicrobial susceptibility testing is to forecast the success or Observation by Fleming in 1928 led to the discovery of a strain of failure of antibiotic therapy. Tests are performed In vitro and measure Penicillium that produced a substance, lytic to staphylococci cells. the growth response of an isolated organism to a particular drug or Over eight decades have passed since the discovery of this “miracle drugs. The trials are carried out under standardized conditions to have drug” referred to as antibiotics or antimicrobials. These drugs are still reproducible results and the test results are used to guide appropriate used for control and treatment of various diseases caused by microbes. antibiotic selection. The results of antimicrobial susceptibility testing Therapy with antimicrobial agents is a relatively young aspect of should be combined with clinical information and experience when medical practice, which has undergone enormous growth in the past selecting the most appropriate antibiotic for your patient. Currently, few decades. The advent of antibiotics has had an enormous impact these methods are based on dilution or diffusion procedures. Of on the treatment of infectious diseases; but also with an adverse side, these, the disc method is best suited to routine use for most purposes partly due to indiscriminate use of these drugs. Though an exhaustive as compared to the traditional broth-based techniques4. number of antibiotics are discovered, this line of treatment also faces severe setbacks due to the emergence of single or multiple drug resistant microorganisms. Despite antibiotics’ extraordinary The need for rapid testing methods value, the overuse of these miracle drugs in medicine and agriculture The principles of determining the effectivity of an antimicrobial agent jeopardizes their continued effectiveness. To counter these problems to a bacterium were well enumerated by Rideal, Walker and others. antimicrobial susceptibility testing methods were developed and The discovery of antibiotics made these tests too cumbersome for the carried out in large scale as a guide to antibiotic therapy. large numbers of tests necessary to be put up as a routine. The ditch plate method of agar diffusion used by Alexander Fleming and variety Importance of antimicrobial susceptibility of agar diffusion methods were devised by workers in this field. With the introduction of a variety of antimicrobials, it became necessary testing to perform the antimicrobial susceptibility test as a routine. For Antimicrobial susceptibility testing of bacterial and fungal isolates is this, different types of reservoirs containing antimicrobials are used, a common and important technique in most clinical laboratories. The however, the antimicrobial impregnated absorbent paper disc is the results of these tests are used for selection of the most appropriate most common type used so far. The disc diffusion method of AST is antimicrobial agent(s) for treatment against the infectious organisms. the most practical method and is still the method of choice for the Antimicrobial susceptibility testing is carried out in large scale average laboratory. as a guide to antibiotic therapy. From the earliest studies with HiMedia has adopted this system in form of Antimicrobial sensitivity chemotherapeutic substances, it was clear that obtaining an accurate discs (SD), Multidiscs like Hexa (HX), Octo (OD), Dodeca (DE) and lcosa assessment of susceptibility was not a simple task and many factors (IC) Discs. influence the results of testing. A lot of independent research and However, the disc diffusion method cannot determine the exact innovative technologies like Ezy MIC™ have helped in determining the Minimum Inhibitory concentration (MIC) of the antibiotics. Hence susceptibility on a better scale of accuracy. Currently, antimicrobial HiMedia has adopted MIC determination systems like Ezy MIC™ Strip susceptibility testing emphasizes on antimicrobial resistance testing & HiComb™ MIC Strips. and is able to quantify the endpoint, which can be directly related to a 2 Minimum Inhibitory Concentration The MIC is the lowest concentration of an antimicrobial agent that the therapy for the individual patient. Selection of the most effective visually inhibits the growth of a microorganism under defined antimicrobial agent and dosing regimen for serious infection will help experimental conditions. MIC values lower than the breakpoint are in eliminating the pathogens and minimize resistance selection and interpreted as susceptible results and those higher as resistant for decrease mortality. treatment guidance. MIC breakpoint values are vital in categorizing HiMedia has adopted this system in the form of HiComb™ (MD), which susceptibility group for In vitro antimicrobial susceptibility testing is based on innovative disc diffusion and gradient-based technique, and clinical interpretation. Understanding the concept of MIC and its essentially with a wide choice of antibiotics. This system is developed relations to the interpretive breakpoint is one of the major hassles using dry chemistry technology and consists of two comb-shaped to microbiologists and clinicians. Since the pharmacokinetics of strips made of an inert material with antibiotic discs at the ends and the antimicrobial agents can be different two agents with the same Ezy MIC™ Strip is based on gradient technology and the combination MIC value for a pathogen may have totally different interpretations of dilution & diffusion principles for Testing of Susceptibility. This because they have different breakpoints. MIC testing is a very valuable method generates the MIC values of a given antibiotic in µg/ml, quantitative assay tool for evaluating the pathogenic microorganism’s which will inhibit the growth of a particular microorganism under the degree of susceptibility and to detect the specific resistance specified set of experimental conditions. The MIC value obtained from mechanism. Today clinical microbiology laboratories can provide this method can be compared to the standardized CLSI procedure. MIC testing services and in many cases exact values for determining Parameters Affecting the Performance of Susceptibility Discs 1) The first and most important parameter affecting the performance and thus false negative results may be interpreted. Variation in ionic