Dr.T.V.Rao MD 1

HOSPITAL ANTIBIOGRAMS

principles interpretation and documentationDr.T.V.Rao MD

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Dr.T.V.Rao MD 2

Different methods to Test Antibiotic Sensitivity

patterns

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What is an antibiogram•An antibiogram is a laboratory test used to determine the sensitivity pattern of a given microorganism to a range of antibiotics.

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What is a Hospital Antibiogram •The hospital antibiogram is a periodic summary of antimicrobial susceptibilities of local bacterial isolates submitted to the hospital's clinical microbiology laboratory. Antibiograms are often used by clinicians to assess local susceptibility rates, as an aid in selecting empiric antibiotic therapy, and in monitoring resistance trends over time within an institution

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Helps in identifying the Antibiotic Resistance

patterns •Antibiograms can also used to compare susceptibility rates across institutions and track resistance trends

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Why we need An Antibiogram •Antimicrobial-resistant bacterial infections are a challenging problem in the hospital setting. Infections caused by resistant- and multidrug-resistant (MDR) bacteria not only increase morbidity and mortality, but also increase overall healthcare costs, primarily by prolonging hospital length of stay.

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Hospital Associated Infections can be Monitored with

Antibiograms • In situations when hospital-acquired infections do occur, the preponderance of MDR bacteria as the causative pathogen challenges clinicians in selecting appropriate therapy and treatment regimens.

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We need better methods to monitor Antibiotic

Therapy •Inappropriate therapy can have significant clinical and economic consequences

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Wrong Antibiograms add to MDR Strains

• Inappropriate antimicrobial selection also has the potential to increase the risk for resistance development.

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Antibiograms are also used to•Check if the causative agent belongs to a species capable of exhibiting resistance to commonly used antibiotics.•Study the epidemiology of resistance•Evaluate the efficacy of a new antibiotics

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Hospital Antibiograms are essential tools

• Hospital antibiograms can be an essential tool to monitor local epidemiology and emerging resistance trends. Antibiograms, if generated and utilized appropriately, can monitor resistance at healthcare facilities by reporting susceptibility rates of common pathogens over a period of time 03-08-2016

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Selecting an Appropriate Antibiotic a Priority

•They can, therefore, serve as an invaluable guide in selecting appropriate empiric therapy and influence institutional antimicrobial use policies

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Growing Importance of Antibiograms

•Over the last twenty years, new categories of antibiotics have entered the market and numerous forms of resistance have appeared and multiplied

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Antibiograms are also used to• Check if the causative agent

belongs to a species capable of exhibiting resistance to commonly used antibiotics.• Study the epidemiology of

resistance• Evaluate the efficacy of a

new antibiotic

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Why should you develop and use an antibiogram at your

Hospital facility?• Antibiograms encourage responsible use of antibiotics

throughout facilities. Prescribing clinicians—physicians, nurse practitioners, and physician assistants—can consult these tools before initiating empiric antibiotic therapy, which may improve outcomes among patients with infections.• Antibiograms are a good way to detect changes in resistance

patterns for an entire facility or for locations within a facility.• Antibiograms can be inexpensive to develop and maintain.

The results are easily accessible to health care providers.03-08-2016

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How to begin our Work with Antibiograms

• Isolation, identification of the pathological Microbe and antibiogram of a pathogenic agent are normally carried out when a bacterial disease has produced a problem•We have specific and

General methods to identify the pathogenic bacterial isolate

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Mechanism in Testing the Antibiograms

• The basic idea of diffusion assays is as follows: the tested antibiotics are impregnated in paper discs which are placed on plate of agar medium inoculated with the bacteria in question.

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Mechanism in Testing the Antibiograms

• Following diffusion of the compounds through the agar, a "halo" or zone of inhibition forms where a concentration of the specific diffused antibiotic is sufficient to inhibit that microbial growth

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Interpreting an antibiogram• The correct interpretation

of the antibiogram will be of interest to Microbiologists and laboratory technicians alike. Standardized methods are established and can be found in the WHO manuals.

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Still we have not Understood Problems with

Antibiograms • One of the most frequently asked

questions relates to in-vitro (in the lab)/in-vivo (in the field) relationships. Why is it that satisfactory in vitro or laboratory test results can translate into poor clinical efficacy In these situations, thought should be given to: clinical and laboratory coordination

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To have a better Understanding of Antibiograms

•a) Whether or not the diagnosis correct? •b) Whether the problem is really caused by the isolated

bacteria?• c) Whether the product was administered correctly, at

the right dose level, for the correct number of days? •d) Whether the activity level of the drug coincides with

label specifications

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Factors influencing the interpretation of an

antibiogram• Based on this reasoning, the

diffusion method is sometimes mistakenly interpreted as a quantitative method. The more potent an antimicrobial compound, the less concentrated it need be, and consequently at points further from the disc with consequently lower concentrations, microbial growth will still be inhibited

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Basic Interpretation of Zone Sizes

•Therefore, it is often assumed that the larger the diameter of the zone of inhibition, the more potent the antimicrobial

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Why Concentration of the Antibiotic matters

• A number of factors however, may interfere with this interpretation. Firstly, the concentration of the antibiotic in the disc must be taken into account. The higher the concentration in the disc, the more concentrated the compound will be at a given distance from the disc itself.

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Time too matters in optimal Reading of Antibiograms

• Also, the length of time allowed for the process to occur can greatly influence the diameter of the zone of inhibition as the longer diffusion is allowed to take place the higher the concentrations at any given point in the gradient will be.

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Zone sizes are Interpreted with consideration of many

factors • Related to this, the infusibility of

the antimicrobial compound through the agar can greatly impact on the observed zone of inhibition, such that a very potent inhibitor may produce a relatively small "halo" simply because it is unable to diffuse adequately through the medium. In addition, the extent of the growth of the microbe

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Outcome of Antibiograms depend on many factors

• In relation to the degree of diffusion, can influence the resulting zone of inhibition, such that the timing of both factors, microbial growth and diffusion, interplay.

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What are the Isolates to be Taken for Reporting

Antibiograms •Only the first isolate from the patient is to be included in the analysis. The analysis should be done on the basis of patient location and specimen type. The percentage susceptibility of the most frequently isolated bacteria should be presented in the antibiogram, preferably in a tabular form

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Basis of Choosing Antibiotic Discs

•The selection of the most appropriate antibiotics to test is a decision best made by each clinical laboratory in consultation with the field veterinarian. To avoid unnecessary duplication, only one antibiotic from each family should be used. Agents of the same family have similar clinical efficacy, show nearly the same spectrum of activity and have similar cross-resistance and cross-susceptibility.03-08-2016

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How to prepare the inoculum for Testing the Antibiograms

•At least three to five well-isolated colonies of the same morphological type bacteria are selected from a primary agar plate culture and transferred into a tube containing 4-5 ml of broth medium.

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Preparing inoculum for Testing Antibiograms

• This is incubated at 35°C for 2-6 hours and then applied with a sterile cotton swab on a dried surface of a Mueller-Hinton agar plate. Alternatively the inoculums can be prepared by making a direct broth or saline suspension of isolated colonies selected from a primary agar plate

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Placement of Antibiotic Discs for Optimal Antibiograms

• The predetermined battery of anti-microbial disks is dispensed onto the surface of the inoculated agar plate. Each disk must be pressed down to ensure complete contact with the agar surface. The disk must be distributed evenly no closer than 24mm from Center to centre. The plates are inverted and placed in an incubator at 35°C.

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Reading the Zones of Inhibition • After 16-18 hours of

incubation, each plate is examined. The resulting zones of inhibition (halo) will be uniformly circular and there will be a confluent lawn of growth. The diameters of the zone of complete inhibition are measured, including the diameter of the disk03-08-2016

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Measuring Zone Sizes in Antibiograms

• The measurement can be done using a sliding calliper, ruler or compass as demonstrated in picture . The zone margin should be taken as the area showing no obvious, visible growth that can be detected by the naked eye.

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Formulating the Concentration of Antibiotic and relevance of

zones depend on •Comparing zone diameters to

minimum inhibitory concentrations (MICs) of a large number of isolates, including those with known mechanisms of resistance relevant to the particular class of drug

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Pharmaco kinetics play a Major Role•Analysing the MICs and correlated zone sizes in relation to the pharmaco-kinetics of the drug from normal dose range schedules

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Choosing Antibiotics to the effectiveness of isolated

pathogens •Analysing whenever possible the tentative in vitro interpretive criteria in relation to studies of clinical efficacy in the treatment of specific pathogens

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What is Susceptible• This category implies that an

infection due to this bacterium may be appropriately treated with the dosage of antibiotic recommended for that type of infection and infecting species, unless otherwise contraindicated

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Intermediate• This category implies that an

infection due to this bacteria, may be treated when possible with higher than normal dosage of this antibiotic, or when the drug is physiologically concentrated in certain body sites, like Quinolones in urine03-08-2016

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Resistant•Resistant strain will

probably not respond to any treatment, as they are not inhibited by the usually achievable systemic concentrations of the antibiotic when normal dosage schedules are used.

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How we express the Results •Because of these

complexities in the diffusion method, it is perhaps best to consider the results of the diffusion assay as qualitative only, expressed as: Sensitive, Intermediate and Resistant03-08-2016

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Do not Process the specimens Directly for Antibiotic

Sensitivity testing •The practice of conducting susceptibility tests directly with clinical material should be avoided except in clinical emergencies when direct gram staining suggests the presence of a single pathogen03-08-2016

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Document Antibiograms with

WHONET • Some hospitals have adequate support from the computer department to be able to extract data from their reporting module. The WHONET software can be freely downloaded and used for analysis.

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WHONET AND CLSI HELPS IN ANALYSIS OF THE ANTIBIOGRAMS

Consensus guidelines have been developed by the Clinical and Laboratory Standards Institute (CLSI) to standardise methods used in constructing antibiograms. These guidelines can be incorporated into the WHONET software for analysis

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How to modernized Hospital Antibiograms

• The antibiogram must be printed or put up in the intranet for easy access to all clinicians. Antibiotic policy is one of the mandatory requirements for accreditation, and making an antibiogram is the first step before framing the antibiotic policy.

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Critical Thinking on Antibiograms

•Antibiograms only capture the aggregate proportion of susceptible isolates for a given organism-antibiotic combination. They do not provide the prevalence resistance to multiple antibiotics.

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Antibiograms helps for taking decisions on Empiric Antibiotics

•Antibiograms provide guidance for empiric antibiotic use in patients, but other factors including patient characteristics and prevalence of other risk factors should be incorporated when making therapeutic decisions

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Future of Antibiograms •The future of antibiograms would be the incorporation of patient related data to make information more reliable and for predicting outbreaks03-08-2016

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Mobile Application on Iphone and IPad

• Antibiograms help healthcare professionals and clinical microbiologists choose the most effective antibiotics to empirically treat infections, based on local susceptibility patterns. Now this valuable information can be available to them on iPhone/iPad mobile devices.

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Antibiogram app•With the Antibiograms app, you simply select a bacterium, select a patient group, and you are given the proportion of susceptible organisms for each antibiotic tested in your local laboratory.

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For Better Understanding on Antibiograms

• For more detailed information, look at the WHO's technical manual.

• Ref 1 The Facts about Antibiogram - Dr Yonatan Segal• 2 Hospital antibiogram: a necessity. Joshi PubMed . Indian J

Med Microbiol. 2010 Oct-Dec;28(4):277-80. doi: 10.4103/0255-0857.71802• 3 Concise Antibiogram Toolkit - EFwww.ahrq.gov/NH-ASP

Guide • May 2014 AHRQ Pub. No. 14-0012-1-EFwww

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• Program Created By Dr.T.V.Rao MD for basic understanding on Creation and Documentation of Hospital Antibiograms for New Generation of Medical Microbiologists practicing

World Wide for better health care • Email

•doctortvrao@gmail.com

03-08-2016