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CLSI Blog Articles

Read the latest articles about CLSI and laboratory standards in the official CLSI Blog. Browse our most recent blog articles below.

The Cefazolin Inoculum Effect for MSSA

Infections due to methicillin-sensitive Staphylococcus aureus (MSSA) continue to be a significant source of morbidity and mortality. While antistaphylococcal penicillins, such as nafcillin, have been the mainstay of therapy for MSSA, the use of cefazolin has grown increasingly popular. Indeed, recent data from observational clinical studies suggest that cefazolin is as efficacious as nafcillin, with less toxicity, has a more favorable dosing schedule, and possibly improves survival. Thus, cefazolin has become first line therapy for the treatment of MSSA infections.

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Differences in Disk Content Recommended by CLSI and EUCAST for Disk Diffusion Testing

Disk diffusion testing is used by a variety of laboratories throughout the world. Disk diffusion breakpoints are dependent on the concentration of antimicrobial impregnated into the disk, otherwise known as the disk content. This disk content in microgram concentrations is printed on each disk and is listed in both CLSI’s M100 and M45 and European Committee on Antimicrobial Susceptibility Testing (EUCAST ) breakpoint tables.

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CLSI's Guidelines on Clinical Method Validation & Verification

Interferents in medical laboratory measurement pose a danger to patients. Although performance is routinely monitored by internal QC and external quality assessment procedures, laboratories cannot easily detect error caused by interferents. Therefore, manufacturers of in vitro diagnostic measuring systems need to include evaluation of potential interferents’ effects in their risk analyses at the product design stage.

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Automation Advances Within the Clinical Microbiology Laboratory

Microbiology specimen processing and culture workup remain mostly manual tasks with few recent changes to methods used. However, automation in the microbiology laboratory through the use of antimicrobial susceptibility testing systems is becoming more prevalent in the lab. Automated microbial identification is performed with MALDI-TOF MS, which stands for matrix-assisted laser de-ionization time-of-flight mass spectrometry.

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PK/PD Workshop Presented at CLSI Committees Week

Last week at CLSI’s first 2019 Committees Week in St. Augustine, Florida, we presented an education session on Recent Advances in Pharmacokinetics/Pharmacodynamics (PK/PD) and Its Use in Setting Breakpoints. Participants in the education session earned continuing education credits.

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Digging Deeper into Understanding Cefazolin Reporting for Enterobacteriaceae

In the Spring 2018 CLSI AST News Update, we provided a case study illustrating various ways by which to report cefazolin as a surrogate for oral cephalosporins for applicable Gram-negative organisms isolated from the urine. The cases concentrated solely on testing and reporting of cefazolin as a surrogate. However, cefazolin, which is administered intramuscularly (IM) or intravenously (IV) may also be used itself for the treatment of complicated urinary tract infections. Additionally, cefazolin may be used in treatment of systemic infections due to susceptible isolates of Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis.

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CLSI’s M100 Annual Updates Webinar

On February 20 and 21, CLSI will host its annual M100 updates webinar. This webinar will be moderated by Janet Hindler, MCLS, MT(ASCP), F(AAM) and presented by Romney M. Humphries, PhD, D(ABMM) and Audrey Schuetz, MD, MPH, FCAP. The material presented will be the same on both days and will help your lab staff identify the major changes found in the updated edition of CLSI document M100.

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Applying Fluoroquinolone Pharmacokinetics, Pharmacodynamics, and Updated Clinical Breakpoints for Gram-Negative Pathogens to Determine Optimal Dosing

Antimicrobial-resistant bacteria are responsible for significant morbidity, mortality, and excess healthcare costs, and their prevalence is increasing at a rate faster than the antimicrobial development pipeline. FDA-approved antimicrobial doses represent estimates across a patient population in order to maximize generalizability and probability of clinical effect as it would apply to “most” patients. Unfortunately, the increase in bacterial resistance and medical complexity of our patients means that these population estimates no longer apply to “most” patients, or at least not to the patients in whom optimizing antimicrobial doses matters the most. Fortunately, the principles of antimicrobial pharmacokinetics (PK) and pharmacodynamics (PD) can help optimize dosing regimens and tailor therapy for each patient individually.

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