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  • Image not available. Familiarity with normal host flora and typical pathogens will help to determine whether a patient is truly infected or merely colonized.
  • Image not available. Direct examination of tissue and body fluids by Gram stain provides simple and rapid information about the causative pathogen.
  • Image not available. Isolation of the offending organism by culture assists in the diagnosis of infection and allows for more definitive directed treatment.
  • Image not available. The development of molecular testing systems has improved our ability to diagnose infection and determine the antimicrobial susceptibilities for numerous fastidious or slow growing pathogens, such as mycobacteria and viruses.
  • Image not available. Although highly standardized, in vitro antimicrobial susceptibility testing has limitations and often cannot truly mimic the conditions found at the site of an infection. This can cause discordance between in vitro susceptibility results and in vivo response to therapy.
  • Image not available. The laboratory evaluation of antimicrobial activity is an important component of the pharmacotherapeutic management of infectious diseases.
  • Image not available. Antimicrobial pharmacodynamics have become a crucial consideration the selection of both empirical and pathogen-directed therapy in the current era of antimicrobial resistance.
  • Image not available. When used appropriately, rapid automated susceptibility test systems appear to improve therapeutic outcomes of patients with infection, especially when they are linked with other clinical information systems.
  • Image not available. Laboratory tests such as minimal bactericidal concentration tests, time-kill tests, post-antibiotic effect tests, and antimicrobial combination testing are important for the clinician to understand because they help to determine antimicrobial pharmacodynamic properties.
  • Image not available. Routine monitoring of serum concentrations is currently used for a select few antimicrobials (e.g., aminoglycosides, chloramphenicol, and vancomycin) in an attempt to minimize toxicity and maximize efficacy.
  • Image not available. Appropriate timing for the collection of serum samples when measuring antimicrobial serum concentrations is crucial to ensure that proper data are generated on the pharmacokinetics of antimicrobials.
  • Image not available. The monitoring of aminoglycoside serum concentrations and the use of extended-interval doses can help to maximize the probability of therapeutic success and minimize the probability of aminoglycoside-related toxicity.
  • Image not available. Vancomycin and aminoglycoside serum concentration monitoring should be routinely done to ensure adequate serum concentrations, minimize toxicity, and avoid the potential for resistance.
  • Image not available. Optimization of antimicrobial pharmacodynamic parameters such as the ratio of the peak serum concentration to minimum inhibitory concentration or the time that the serum concentration remains above the minimum inhibitory concentration and area above the curve over minimum inhibitory concentration can improve infection treatment outcomes.

Upon completion of the chapter, the reader will be able to:

  • 1. Define the Minimal Inhibitory Concentration (MIC) and describe the various methodologies used to determine MICs in the clinical microbiology laboratory.
  • 2. Contrast the methods and results of the disk-diffusion antimicrobial susceptibility test (the Kirby-Bauer test) with those of the MIC test.
  • 3. Identify at least two limitations associated with each of the three types of MIC testing.
  • 4. Identify key considerations for qualitative and quantitative antimicrobial susceptibility tests.
  • 5. Explain how patients may fail antimicrobial therapy even when the infecting pathogen appears to be susceptible to the antimicrobial via conventional test methods.
  • 6. Describe two commonly used tests for detecting antimicrobial resistance.
  • ...

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