Intermediate la boratory manual

If such strains should arise, it is recommended that the species identification and resistance testing should be rechecked and the strain should be sent to a reference laboratory. Since clinical experience in how to treat these strains is currently lacking they should be classified as resistant, in accordance with the threshold value in bold. The DIN subcommittee has actively followed these developments and will act in accordance with the new determinations.

Some important changes will come about in Germany as a result. All organisms have been assessed until now according to uniform breakpoint criteria. This has often caused problems because, for many antibiotic drugs, the two peaks of the bimodal distribution of MIC values are found at different concentrations for different species of infectious microorganism.

Now, breakpoints have been set for individual classes of microorganism, e. This allows the breakpoints for individual classes of microorganism to be adjusted so that contiguous clusters of infectious organisms e.

The changes in relation to the breakpoints that were applicable until now according to DIN , Supplement 1, affect the cephalosporins in particular. In this area, the breakpoint between "susceptible" and "intermediate" for the Enterobacteriaceae had to be lowered so that organisms with clinically relevant extended spectrum beta-lactamases ESBL would not be incorrectly classified as susceptible.

Clinical experience has shown that infections with strains possessing ESBLs cannot be treated very effectively with cephalosporins, or cannot be treated with them at all Aside from this case, the changes relative to the previously applicable DIN breakpoints are slight. Nonetheless, any comparison of old and new resistance rates will be unreasonable, because spurious trends will arise that will be due solely to changed breakpoints rather than to changes in the antibiotic susceptibility of the infectious organisms.

The differences between the European and American breakpoints are particularly striking see the example of cefotaxime illustrated in table 3. Regrettably, practicing clinicians are usually unaware which of the two standards was used in reporting the microbiological findings and how large the differences between them actually are for many organism-drug combinations.

In extreme cases, e. The same holds for published epidemiological data. Often, it is not even stated which breakpoints were used.

It thus seems more reasonable to present MIC distributions, as in the figure shown in this paper, because otherwise there may be no basis for comparison of the microbiological data obtained by different research groups. The manufacturers of automatized testing systems state that they will provide test kits meeting the EUCAST specifications. It will be difficult to implement the new breakpoints for other derived testing procedures, particularly the agar diffusion test. Because the MIC breakpoints have changed, the corresponding breakpoint diameters for zones of inhibition must be changed as well.

Regrettably, many of the correlations underlying the DIN breakpoints that have been in use up to the present were established many years ago and are inadequately documented. Therefore, if the EUCAST breakpoints are to be implemented, extensive new studies are required in order to correlate the MIC values with inhibitory zone diameters for each and every antibiotic.

In addition, the requirements of the new ISO standard must be met as well. In view of the likelihood that the agar diffusion test will also be standardized across Europe in the near future, particularly with respect to the inoculum that should be used, it would seem inadvisable to go to this great effort at present for the procedure that has been standardized according to DIN This, in turn, will cause problems with accreditation with external quality control systems. Nor does it seem reasonable to go back to the CLSI breakpoints, because this would only heighten the differences that are already present.

EUCAST is now attempting to establish a European standard for the agar diffusion test, including breakpoints for inhibitory zone diameters. The results are not expected until late For a number of drugs, however, the indications for which the drug is approved will have an influence on the breakpoints. Thus, an antibiotic that has been approved solely for the treatment of urinary tract infections should be assessed differently from one that is also used to treat respiratory tract infections.

When the breakpoints were set for Neisseria meningitidis, for example, account was taken of the fact that this organism usually causes an infection in the central nervous system. On the other hand, for a number of organism-drug combinations, no breakpoints were determined. In some cases, this was because the organism did not belong to the spectrum of efficacy of the drug; in other cases, no breakpoint was set because of the lack of adequate published clinical data on the particular combination in question.

The newly standardized breakpoints across Europe will, however, improve the reliability of categorization as "susceptible," "intermediate," and "resistant. Conflict of interest statement. PD Dr. Bauer, Professor Ewig, and Professor Kujath declare that they have no conflict of interest as defined by the guidelines of the International Committee of Medical Journal editors. National Center for Biotechnology Information , U.

Journal List Dtsch Arztebl Int v. Dtsch Arztebl Int. Published online Sep Arne Rodloff , Prof. Author information Article notes Copyright and License information Disclaimer. Received Nov 16; Accepted May Copyright notice. This article has been cited by other articles in PMC. Abstract Introduction To date, the resistance of infectious agents has been assessed by widely varying criteria in different countries.

Methods Selective literature review and evaluation of committee reports. Results The new ISO standard for determination of the resistance of infectious agents and the harmonized evaluation system of the European Society for Clinical Microbiology and Infectious Diseases provide a new basis for susceptibility testing.

Discussion For a number of antibiotics, the criteria for evaluation of infectious agents as "susceptible," "intermediate", or "resistant" will change. Keywords: resistance testing, antibiotic, pharmakokinetics, in-vitro diagnostic agent, bacteriological testing.

The determination of microbial sensitivity An important task of medical microbiology is the phenotypic in vitro testing of antimicrobial substances for their effectiveness against infectious organisms. Table 1 Schematic representation of a microtitration plate for the determination of minimal inhibitory concentrations MICs.

Open in a separate window. Breakpoint determination Thresholds are determined on the basis of a large amount of data. For each substance, at least the following information must be taken into account: Indications Dosage Pharmacokinetics Pharmacodynamics Concentration-dependent toxicity, if any Results of clinical testing Analysis of cases of therapeutic failure.

The important elements of pharmocodynamics include the following: The MIC distributions for the infectious organisms within the area of indication of the drug MIC compared to minimal bactericidal concentration Microbial death kinetics Inoculum effects Data from animal experiments. Catarrhalis 3,4 N.

Differences between Europe and the USA The differences between the European and American breakpoints are particularly striking see the example of cefotaxime illustrated in table 3. References 1. Rello J, Diaz E. Pneumonia in the intensive care unit. Crit Care Med. Using local microbiologic data to develop institution-specific guidelines for the treatment of hospital-acquired pneumonia. Kiem S, Schentag JJ. Relationship of minimal inhibitory concentration and bactericidal activity to efficacy of antibiotics for treatment of ventilator-associated pneumonia.

Semin Respir Crit Care Med. Speed of bacterial kill with a fluoroquinolone compared with nonfluoroquinolones: clinical implications and a review of kinetics of kill studies. Adv Ther. Gould IM. Determinants of response to antibiotic therapy. J Chemother. Eliopoulos GM. Antimicrobial agents for treatment of serious infections caused by resistant Staphylococcus aureus and enterococci.

Two decades of imipenem therapy. J Antimicrob Chemother. Clin Ther. Every year the school education department is updated their syllabus and makes some changes in the textbooks completely or chapter-wise, and the SCERT AP has published the AP 1st and 2nd Year Textbooks and distributed them to all government high schools of the state. Download Subject wise and chapter-wise announcements AP Intermediate Textbook and e-Books from the official website of the APSCERT, and we have also provided the direct link to download in Pdf file format, follow the link to download and follow the latest announcements.

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