What's New in Antibiograms? Updating CLSI M39 Guidance with Current Trends.

A vast amount of antimicrobial susceptibility test (AST) data is generated from routine testing in diagnostic laboratories for the primary purpose of guiding clinicians in antimicrobial therapy decisions for their patients. However, there is additional value for these data when they are compiled at the local, regional, national, and global levels. Cumulative AST data can be used to prepare antibiograms at the individual health care facility level. These reports can be used to gain insight into appropriate empirical therapy options prior to the availability of AST results on an individual patient's isolate. Different types of cumulative AST data reports can also be compiled at the regional, national, and global levels to estimate susceptibility rates in geographic regions, document trends in evolving microbial populations, and recognize the appearance and spread of emerging antimicrobial resistance threats. The first CLSI M39 Guideline for Analysis and Presentation of Cumulative AST Data was published in 2000. Since that time, there have been changes to AST and reporting recommendations as well as the introduction of advanced informatics technologies to analyze and present data. The 5th edition of M39 has taken into consideration these changes to assist those who analyze, present, and utilize routine antibiograms and other types of cumulative AST data reports as well as those who design information systems for the capturing and analyzing of AST data. Furthermore, antimicrobial stewardship programs (ASPs) have expanded considerably, and uses of the antibiogram by ASPs have been addressed. This minireview will remind users of the basic recommendations for analysis and presentation of antibiograms and provide new suggestions to enhance these reports.

Absence of TetB identifies minocycline-susceptible isolates of Acinetobacter baumannii.

Minocycline is one of the few options available to treat infections caused by Acinetobacter baumannii. Acquired resistance to minocycline in A. baumannii is associated with presence of the TetB efflux pump. Previous studies suggested that the absence of tetB may predict minocycline minimum inhibitory concentrations (MICs) of ≤4 µg/mL. In this study, a collection of 258 A. baumannii isolates was used to generate MIC frequency distributions for the tetB-positive and -negative sets of isolates. Of the 93 tetB-negative strains, all had minocycline MICs ≤ 4 µg/mL, resulting in a negative predictive value of 100%. Of the 165 tetB-positive strains, 154 had minocycline MICs > 4 µg/mL, resulting in a positive predictive value of 93.3%. In conclusion, this study shows that tetB is highly associated with MICs above the current US Food and Drug Administration (FDA) and Clinical and Laboratory Standards Institute (CLSI) susceptible breakpoint of 4 µg/mL.