Expedited pathways to antimicrobial agent approval by the U.S. Food and Drug Administration (FDA) have led to increased delays between drug approval and the availability of FDA-cleared antimicrobial susceptibility testing (AST) devices. Antimicrobial disks for use with disk diffusion testing are among the first AST devices available to clinical laboratories. However, many laboratories are reluctant to implement disk diffusion testing for a variety of reasons, including dwindling proficiency with this method, interruptions of the laboratory workflow, uncertainty surrounding the quality and reliability of disk diffusion tests, and a perceived need to report MIC values to clinicians. This minireview provides a report from the Clinical and Laboratory Standards Institute Methods Development and Standardization Working Group on the current standards and clinical utility of disk diffusion testing.

There is an urgent need for rapid, accurate detection and classification of carbapenemases. The current study evaluated the automated BD Phoenix CPO Detect and the manual bioMérieux Rapidec Carba NP tests for meeting these needs. Both tests were challenged with 294 isolates of Enterobacteriaceae spp., Pseudomonas aeruginosa, and Acinetobacter baumannii chosen to provide extreme diagnostic difficulty. Carbapenemases such as KPC, NMC-A, IMI, SME, NDM, SPM, IMP, VIM, and OXA-23, 40, 48, 58, 72, 181, and 232 were produced by 243 isolates and 51 carbapenemase-negative isolates included porin mutants and producers of extended-spectrum β-lactamases (ESBLs), AmpCs, K1, and broad-spectrum β-lactamases. Both tests exhibited high sensitivity of carbapenemase detection (>97%). Due to the highly challenging carbapenemase-negative isolates, specificities were lower than typical for evaluations involving mostly routine clinical isolates. BD Phoenix CPO Detect was 68.6% specific and Rapidec Carba NP was 60.8% to 78.4% specific, depending on how borderline results were interpreted. Only BD Phoenix CPO Detect classified carbapenemases. It correctly classified 85.0% of class A, 72.4% of class B, and 88.6% of class D carbapenemases. Importantly with respect to empirical therapy with new β-lactamase inhibitor combinations such as ceftazidime/avibactam, no class B carbapenemases were misclassified as class A carbapenemases. Both tests offer advantages. Used alone, without initial susceptibility tests, Rapidec Carba NP can provide positive results for some isolates after only 10 to 30 min incubation. BD Phoenix CPO Detect provides novel advantages such as automated carbapenemase detection, inclusion in susceptibility panels to eliminate delays and subjectivity in initiating carbapenemase tests, and classification of most carbapenemases.

265words) 32 Background: 33 Limited treatment options contribute to high morbidity/mortality rates with carbapenem-resistant, 34 gram-negative bacterial infections. New approaches for carbapenemase-producing organism 35 (CPO) detection may help inform clinician decision-making on patient treatment and infection 36 control. BD Phoenix™ CPO detect ("CPO detect") detects and classifies carbapenemases in 37 Enterobacterales, Acinetobacter baumannii, and Pseudomonas aeruginosa during susceptibility 38 testing. The clinical performance for CPO detect is reported here. 40Methods: 41 Enterobacterales, Acinetobacter baumannii, and Pseudomonas aeruginosa isolates were 42 evaluated across three sites using CPO detect and a composite reference method (RM); the latter 43 comprised of the modified carbapenem inactivation method and minimal inhibitory 44 concentration (MIC) screen for ertapenem, imipenem, and meropenem. Multiplex PCR testing 45 was also utilized for Ambler class determination. Positive/negative percent agreements (PPA and 46 NPA) between CPO detect and RM were determined. 47 48 Results: 49 PPA and NPA for Enterobacterales were 98.5% [96.6, 99.4] and 97.2% [95.8, 98.2], 50 respectively. A. baumannii PPA and NPA, respectively, were 97.1% [90.2, 99.2] and 97.1% 51 [89.9, 99.2]. P. aeruginosa PPA and NPA, respectively, were 95.9% [88.6, 98.6] and 92.3% 52 [86.7, 95.6]. PPA for carbapenemase class designation for all organisms combined and 53 Enterobacterales alone, respectively, were 95.3% [90.2, 97.8] and 94.6% [88.8, 97.5] for Class 54 on July 4, 2020 by guest http://jcm.asm.org/ Downloaded from Clinical performance for CPO detection-Whitley et al., 2020-JCM 3 A, 94.0% [88.7, 96.6] and 96.4% [90.0, 98.8] for Class B, and 95.0% [90.1, 97.6] and 99.0% 55 [94.4, 99.8] for Class D. NPA values for all organisms, and Enterobacterales alone, ranged from 56 98.5% to 100%. 57 58 Conclusions: 59 CPO detect provided accurate detection and classification of CPOs for the majority of isolates of 60 Enterobacterales, Acinetobacter baumannii, and Pseudomonas aeruginosa tested. 61 62 KEY WORDS: Carbapenem resistance; Carbapenemase-producing organisms; Ambler class 63 carbapenemase; Carbapenemase-resistant Enterobacterales; Phoenix CPO detect 64 on July 4, 2020 by guest http://jcm.asm.org/ Downloaded from Clinical performance for CPO detection-Whitley et al., 2020-JCM 65 Approximately 2.8 million people are infected with antibiotic-resistant bacteria each year in the 66 USA; at least 35,000 die as a result of antibiotic resistance.(1) A large number of these 67 mortalities are caused by multidrug-resistant (MDR), gram-negative organisms,(2, 3) which 68 continue to represent a major health concern-especially in hospital settings,(4-6) where 69 mortality rates due to MDR range from 30-70%. (7, 8) Recent data suggest that anywhere from 5-70 60% of infections involve antibiotic resistant organisms.(9, 10) Carbapenems are among a 71 diminishing list of effective antibiotic classes for the treatment of MDR in...

BBL CHROMagar Staph aureus (CSA) medium was evaluated internally and externally for the isolation and enumeration of Staphylococcus aureus in cooked roast beef, smoked salmon, and shell eggs. All food matrixes were processed according to the AOAC Official Method 975.55 and ISO 6888-1:1999. Bacterial counts of S. aureus were compared on CSA to the reference media, Baird-Parker, at low, medium, and high contamination levels. Colony counts were converted to log10 for statistical analysis. Based on the paired t-test and one-way analysis of variance, no statistical difference was noted with the CSA method compared to the AOAC Official Method for the recovery of S. aureus for all food types and contamination levels. Compared to the ISO reference method, no statistical difference was found with the CSA method for any food type or contamination level, with the exception of low-level smoked salmon. A statistical difference was seen in the internal testing with the low-level contaminated smoked salmon where CSA recovered more colonies. The external testing showed no statistical difference with smoked salmon at the low level. The correlation coefficients ranged from 92.6 to 99.4, demonstrating good correlation for overall levels in all food types and methods. The sensitivity and specificity of the CSA method using known isolates was 100. The results of this study demonstrate that CSA is an effective medium for the isolation, enumeration, and presumptive identification of S. aureus in cooked roast beef, smoked salmon, and shell eggs in 24 h using ISO and AOAC official methods.

No abstract