Susceptibility Testing System Research Articles

P-2102. Performance of the VITEK®2 Advanced Expert System (AES) as a Rapid Aid for Reporting Antimicrobial Susceptibility Testing in Pseudomonas aeruginosa and Acinetobacter spp

Abstract Background The VITEK®2 Advanced Expert System (AES) is an automated antibiotic susceptibility testing (AST) system which provides rapid AST data by interpreting and checking each MIC against a database of phenotypes and MIC distributions and infers a resistance mechanism. AES provides a level of confidence for auto-releasing reports of green (consistent), yellow (consistent with correction), and red (inconsistent, MIC pattern not matching any phenotype). This study evaluated VITEK®2 AES reports compared to broth microdilution (BMD) on a set of Pseudomonas aeruginosa (PA) and Acinetobacter spp. (ABC). Methods A total 148 PA and 150 ABC were tested. Susceptibility was tested by VITEK®2 (N802 and XN15 AST cards) and CLSI reference BMD against 13 antimicrobials for PA and 17 antimicrobials for ABC applying 2021 CLSI breakpoints. Molecular characterization of isolates was based on WGS or PCR of β-lactamase genes. Permeability and gene expression were not evaluated. Results Among 143 ABC, AES reports were green for 131 (91.6%), and yellow for 12 (8.4%) isolates. Green reports agreed with BMD for 131 isolates (100%) and could have been automatically reported without further review. Among yellow reports, AES corrections were acceptable for 11 isolates (91.7%). Among 40 carbapenem-producing ABC, AES reports were green for 39 isolates (97.5%) and yellow for one isolate (2.5%). Green reports agreed with BMD for 37 isolates (94.9%) and could have been automatically reported. Of 148 PA, AES reports were green for 125 (84.5%), yellow for 18 (12.2%), and red for 5 (3.4%) isolates. Of 112 PA with molecular data, 64 (57.1%), 38 (33.9%), 6 (5.4%), 3 (2.7%), and one (0.9%) contained genes for intrinsic β-lactamases only (WT), MBL, GES carbapenemase, KPC, and ESBL genes only, respectively. Overall, the AES accurately reported phenotypes for 97/112 PA (86.6%). Among the MBL-positive PA, 37/38 (97.4%) were reported as green and all showed AES phenotype agreement with the genotype. Among the WT PA, 51/64 (79.7%) were reported as green and 82.4% showed AES phenotype agreement with the genotype. Conclusion The use of VITEK®2 AES for the confident release of AST results without additional review could have a positive impact on time savings in the laboratory and aid in antimicrobial stewardship. Disclosures All Authors: No reported disclosures

Comparative performances of the Qvella FAST system and conventional methods for rapid identification and antibiotic susceptibility testing on monomicrobial positive blood cultures.

Rapid and accurate diagnosis of sepsis is of paramount importance to reduce associated morbidity and mortality. The Qvella FAST System is a new instrument that concentrates and purifies bacteria from positive-flagged blood culture bottles (PFBCBs) to produce a "liquid" colony comparable to a subcultured colony in less than 40 min for rapid ID and calibrated antibiotic susceptibility testing (AST). In this study, we evaluated performances of the FAST System workflow and our rapid routine manual workflow (bacterial pellet obtained after lysis, cleaning, washing, and centrifugation for ID; AST by disc diffusion by direct inoculation after dilution) by comparison to the reference method based on 24-h bacterial subcultures. Two panels of PFBCBs were studied: panel A (including 107 prospective BCs from septic patients, October-November 2022) and panel B (including 102 BCs spiked with difficult-to-identify bacteria [mostly streptococci] and multidrug-resistant isolates), resulting in a total of 209 evaluable samples. The FAST System provided a correct ID to the species level in 178/209 (85.2%) of cases. For AST, the categorical agreement (CA) of the FAST System was 99.4%, with rates of very major (VME), major (ME), and minor (mE) errors of 0.59%, 0.20%, and 0.26%, respectively. Our rapid routine workflow based on manual methods show similar results for ID (86.2%) and AST (CA, 99.6%; VME, 0.50%; ME, 0.16%; mE, 0.13%). In conclusion, the Qvella FAST system, a promising tool that can reduce diagnostic time by approximately 1 day, shows excellent performances for rapid ID and AST.

Performance evaluation of the Specific Reveal system for rapid antibiotic susceptibility testing from positive blood cultures containing Gram-negative pathogens.

Rapid antimicrobial drug administration is crucial for the efficient treatment of sepsis or septic shock, but empirical therapy is limited by the increasing prevalence of multidrug-resistant bacteria. Thus, rapid and reliable antimicrobial susceptibility testing (AST) is needed to start appropriate antimicrobial drug administration as quickly as possible. In the present study, we evaluated the performance of the Reveal rapid AST system. From February to April 2021, 102 positive blood culture bottles (BCBs) from hospitalized patients with bacteremia caused by Gram-negative bacteria were included in the study. All isolates were tested by the Reveal system directly from the positive BCBs in comparison to the DxM MicroScan WalkAway. Essential agreement (EA) and category agreement (CA) were high with 98.5% and 97.1%, respectively. We also determined the susceptibility of 10 highly resistant CDC & FDA AR strains in duplicate. Here, EA was 99.6% and CA 97.9%. The average time to result by Reveal was 5.4 h ± 1.2 h compared to an average of 16 h by DxM MicroScan WalkAway for clinical strains and 3.8 h ± 1.2 h for more resistant CDC & FDA AR strains. Susceptibility determination with the Reveal rapid AST system directly from positive BCBs is for the frequently represented bug-drug combinations a reliable and accurate approach, meeting the European ISO guideline for the performance of AST systems. Moreover, AST directly from blood cultures performed with the Reveal system saves time when compared to the conventional AST, as no subculturing is needed and time to result is very short.

A comparative study of a rapid phenotypic antimicrobial susceptibility testing system directly from positive blood cultures to the disk diffusion and VITEK 2 methods

Sepsis is a life-threatening condition that impacts 49 million people annually and causes 11 million deaths worldwide. Surviving bloodstream infections (BSIs) depends on the rapid administration of effective antimicrobial treatment, underscoring a need for rapid antimicrobial susceptibility testing (AST). To evaluate the performance of Quantamatrix's dRAST v2.5 system (Seoul, South Korea) for AST directly from positive blood cultures as compared to the Disk-Diffusion (DD) and VITEK 2 methods. The study included 191 positive blood cultures from clinical samples and spiked blood culture bottles. Following Gram staining and species-level identification, AST was performed by VITEK 2 and standard DD methods using CLSI (2021) interpretation. dRAST demonstrated very good AST performance for a Gram-negative isolate, and good performance for Gram-positive isolates, meeting CLSI criteria for the acceptance of a new method. Antimicrobials that were not considered verified compared to VITEK 2 and DD were cefazolin, ceftazidime, meropenem, and trimethoprim/sulfamethoxazole for Gram-negatives and clindamycin, erythromycin, penicillin, and oxacillin for Gram-positives. dRAST ESBL detection results were strongly correlated with the ESBL phenotypes obtained with other methods. Additional resistance mechanisms were in concordance with traditional tests. dRAST demonstrated good AST performance, meeting CLSI criteria for most relevant antibiotics. dRAST was associated with a significant reduction in time-to-results, labor, and the subjectivity of result analyses, making it a valuable addition to efforts supporting the treatment of patients with bacteremia. AST (antimicrobial susceptibility test), blood culture, dRAST, rapid methods, sepsis, turnaround time (TAT).

Performance evaluation of cefoxitin screen test on two different automated antimicrobial susceptibility test systems: a comparative study.

Reliable detection of mecA and mecC-mediated beta-lactam resistance using automated antimicrobial susceptibility test systems is critical for patient care. The aim of this study was to compare the performance of the new cefoxitin screen test (oxsf02n) on the Vitek 2 card (Vitek 2) and BD Phoenix PMC-100 Gram-Positive AST Panel (Phoenix) against the reference method for the detection of mecA (and mecC)-mediated beta-lactam resistance. Two hundred fifty clinical fresh and stock Staphylococcus spp. isolates were included. There were 120 mecA-positive, 10 mecC-positive, and 120 mecA and mecC-negative isolates. Cefoxitin screen and oxacillin tests were performed on Vitek 2 and Phoenix and by their respective reference methods (disk diffusion for the cefoxitin screen test and broth microdilution for oxacillin) for all isolates. PCR testing was also performed to confirm the presence of mecA and/or mecC genes. Results from each system were compared to the reference methods. Statistical hypotheses were evaluated both for Vitek 2 compared to the reference methods and Vitek 2 compared to the Phoenix. Compared to the reference method, the Vitek 2 cefoxitin screen test had 100% sensitivity/98% specificity and the Phoenix cefoxitin screen test had 84% sensitivity/100% specificity for the detection of mecA (and mecC)-mediated beta-lactam resistance. When the oxacillin test was combined with the cefoxitin screen for Vitek 2, the sensitivity and specificity were unchanged. However, when the oxacillin and cefoxitin screen tests were combined for the Phoenix, the sensitivity increased to 100% and the specificity remained unchanged (100%). When considering cefoxitin alone, the Vitek 2 screen test showed a higher sensitivity than the Phoenix for the detection of mecA and mecC-mediated beta-lactam resistance. However, currently, both systems use a combination of the cefoxitin and oxacillin tests to interpret the final result, and both reached a high level of performance when cefoxitin and oxacillin results were combined.IMPORTANCEThis research marks the inaugural evaluation of the revamped cefoxitin screen test version in Vitek 2, juxtaposing it against reference methods and a primary competitor BD Phoenix.

Evaluation of the Vitek® Reveal™ system for rapid antimicrobial susceptibility testing of Gram-negative pathogens, including ESBL, CRE and CRAB, from positive blood cultures

Blood culture (BC) remains the reference diagnostic tool for bloodstream infections but is hampered by long turn-around time (TAT). This study evaluated the Vitek® Reveal™ (VR) system for rapid antimicrobial susceptibility testing (AST) with 72 cases of monomicrobial BCs (55 Enterobacterales, 12 Pseudomonas aeruginosa and 5 Acinetobacter baumannii), including isolates producing carbapenemases and/or extended-spectrum β-lactamases. VR returned AST results with a mean TAT of 5.4 h. Compared to a conventional workflow based on broth microdilution, VR exhibited essential agreement (EA) and category agreement (CA) >90 % in most cases, except with meropenem for Enterobacterales (CA, 85.5 %), piperacillin/tazobactam for P. aeruginosa (EA, 83.3 %), and trimethoprim/sulfamethoxazole for A. baumannii (CA and EA, 80 %). Bias exhibited an underestimation trend with ceftazidime/avibactam (-78.9 %) and ceftazidime (-50 %) for Enterobacterales and P. aeruginosa, respectively. Overall, VR appears an interesting tool to decrease TAT of the BC workflow, although further evaluation with some antibiotic-pathogen combinations would be warranted.

Surveillance of In Vitro Activity of Cefiderocol Against Carbapenem-Resistant Gram-Negative Clinical Isolates in a Tertiary Care Hospital.

Antibiotic resistance among Gram-negative bacterial isolates is increasingly observed. With the emergence of carbapenem-resistant and pan-resistant pathogens, treating these resistant infections is becoming more challenging due to the limited number of effective drugs. There is a desperate need for the discovery of new antibiotics with novel mechanisms of action. Cefiderocol is one such novel antibiotic with a unique siderophore-based mechanism of action, which has been recently approved for clinical use against drug-resistant pathogens. The present study aims to identify the in vitro activity of cefiderocol against major carbapenem-resistant clinical isolates, including those resistant to colistin. One hundred and one carbapenem-resistant clinical isolates were included in the study. Identification and antibiotic susceptibility testing were performed using the automated VITEK® 2 Compact (bioMérieux SA, Marcy-l'Étoile, France) identification and susceptibility testing system, except for colistin and cefiderocol. Colistin resistance in Enterobacterales and Pseudomonas aeruginosa was assessed using the agar dilution minimum inhibitory concentration method, while for Acinetobacter baumannii, broth microdilution method was employed. Cefiderocol susceptibility testing was conducted using the Kirby-Bauer disc diffusion method with 30 µg discs on standard Mueller-Hinton agar plates. For selected isolates, cefiderocol minimum inhibitory concentration detection was performed using broth microdilution with iron-depleted cation-adjusted Mueller-Hinton broth. Of the total 101 isolates, the majority (75, 74.25%) were Enterobacterales which includedKlebsiella pneumonia (42, 41.58%) and Escherichia coli (33, 32.67%), followed by Pseudomonas aeruginosa (13, 12.87%) and Acinetobacter baumannii (10, 9.9%). Only three (2.97%)of the isolates were Stenotrophomonas maltophilia. Most of the isolates were susceptible to cefiderocol, with only four (3.96%) isolates showing resistance. Colistin resistance was observed in six (6.12%) of the isolates. There was a good correlation between disc diffusion testing and broth microdilution testing for the detection of cefiderocol-resistant isolates. No cross-resistance with colistin was observed, as all colistin-resistant isolates were uniformly susceptible to cefiderocol Conclusion: Cefiderocol is highly effective with good in vitro activity against the majority of carbapenem-resistant pathogens. While some isolates do show resistance, it is relatively uncommon. Given its safety profile compared to colistin, cefiderocol can serve as an alternative to colistin to treat carbapenem-resistant infections and it may be considered even for the management of colistin-resistant cases. Disc diffusion testing is a reliable method for identifying cefiderocol-resistant isolates in routine clinical and diagnostic laboratories, especially in resource-limited settings.

Pyuria, bacteriuria and empirical antibiotic selection in pregnant women

Aims: In pregnancy, early diagnosis and proper treatment of urinary tract infections are crucial in preventing maternal and fetal comorbidities. Therefore, pregnant women should be screened for asymptomatic bacteriuria. This study aimed to evaluate the relationship between pyuria and bacteriuria and the susceptibility of uropathogens, as well as to review the empiric drug options for pregnant women. Methods: The presence of pyuria and bacteriuria in urine samples obtained from the pregnant outpatient clinic between January 2023 and December 2023 at Kırıkkale University Faculty of Medicine Hospital’s Infectious Diseases and Clinical Microbiology Laboratory was investigated. Uropathogens were identified and typed using the BD Phoenix™ M50 automated system for bacterial identification and antibiotic susceptibility testing, and antibiotic susceptibility was interpreted according to the European Committee on Antimicrobial Susceptibility Testing criteria. Results: A total of 1457 urine samples were evaluated in this retrospective study. Uropathogens were detected in 235 patients, while 301 samples were considered contaminated. Uropathogens were found to be susceptible to amoxicillin-clavulanate, trimethoprim-sulfamethoxazole, nitrofurantoin, and fosfomycin, in that order, for use in pregnant women. High resistance rates to third-generation cephalosporins were observed. Conclusion: According to the results of this study, local resistance rates against urinary pathogens in pregnant women should be determined at specific intervals, and empirical antibiotic therapy should be planned based on these data.

What's old is new: leveraging existing antimicrobial susceptibility test methods for rapid results in patients with bloodstream infections.

The use of rapid disk diffusion or modified automated antimicrobial susceptibility testing (AST) system approaches demonstrates excellent performance for gram-negative organisms directly from blood cultures. In a recent study, S. Khan, A. Das, A. Mishra, A. Vidyarthi, et al. (Microbiol Spectr 12:e03081-23, 2024, https://doi.org/10.1128/spectrum.03081-23) compared the performance of three direct-from-blood AST methods against standard of care disk diffusion and automated AST. The results demonstrated high categorical agreements and low error rates across three protocols. The study suggests that locally validated direct-from-blood AST protocols offer reliable and fast results, particularly for resource-limited settings. However, local context and workflows should be considered prior to implementing rapid AST protocols, and more research is needed on the performance of rapid AST protocols for gram-positive organisms.

Evaluation of Quantamatrix dRASTTM system for rapid antimicrobial susceptibility testing of bacterial isolates from positive blood cultures, in comparison with commercial Micronaut broth microdilution system

Antimicrobial susceptibility testing (AST) from blood culture (BC) may take several days, limiting the eventual impact on antimicrobial stewardship. Hence, rapid AST systems represent a valuable support in shorting the time-to-response. In this work, the Quantamatrix dRASTTM system (dRAST) was evaluated for rapid AST on 100 monomicrobial BCs (50 Gram-negatives and 50 Gram-positives), including several isolates with clinically relevant resistance mechanisms. AST results were provided in 6-hours, on average. Compared to Micronaut (Merlin) system based on broth microdilution, dRAST exhibited an overall categorical agreement of 92.5 %, essential agreement of 89.0 %, and mean bias of 15.9 %. Category overestimation (potentially leading to unnecessary high-dosage treatment or to exclude active agents) and category underestimation (potentially leading to underdosing or using ineffective agents) were observed in 4.3 % and 3.1 % of cases, respectively. Even though several issues were reported, results confirmed the potential contribution of dRAST to shorten the BCs clinical microbiology workflow and management.

Pathogenomics analysis of high-risk clone ST147 multidrug-resistant Klebsiella pneumoniae isolated from a patient in Egypt

BackgroundThe emergence of multi-drug-resistant Klebsiella pneumoniae (MDR-KP) represents a serious clinical health concern. Antibiotic resistance and virulence interactions play a significant role in the pathogenesis of K. pneumoniae infections. Therefore, tracking the clinical resistome and virulome through monitoring antibiotic resistance genes (ARG) and virulence factors in the bacterial genome using computational analysis tools is critical for predicting the next epidemic.MethodsIn the current study, one hundred extended spectrum β-lactamase (ESBL)-producing clinical isolates were collected from Mansoura University Hospital, Egypt, in a six-month period from January to June 2022. One isolate was selected due to the high resistance phenotype, and the genetic features of MDR-KP recovered from hospitalized patient were investigated. Otherwise, the susceptibility to 25 antimicrobials was determined using the DL Antimicrobial Susceptibility Testing (AST) system. Whole genome sequencing (WGS) using Illumina NovaSeq 6000 was employed to provide genomic insights into K. pneumoniae WSF99 clinical isolate.ResultsThe isolate K. pneumoniae WSF99 was phenotypically resistant to the antibiotics under investigation via antibiotic susceptibility testing. WGS analysis revealed that WSF99 total genome length was 5.7 Mb with an estimated 5,718 protein-coding genes and a G + C content of 56.98 mol%. Additionally, the allelic profile of the WSF99 isolate was allocated to the high-risk clone ST147. Furthermore, diverse antibiotic resistance genes were determined in the genome that explain the high-level resistance phenotypes. Several β-lactamase genes, including blaCTX−M−15, blaTEM−1, blaTEM−12, blaSHV−11, blaSHV−67, and blaOXA−9, were detected in the WSF99 isolate. Moreover, a single carbapenemase gene, blaNDM−5, was predicted in the genome, positioned within a mobile cassette. In addition, other resistance genes were predicted in the genome including, aac(6’)-Ib, aph(3’)-VI, sul1, sul2, fosA, aadA, arr-2, qnrS1, tetA and tetC. Four plasmid replicons CoIRNAI, IncFIB(K), IncFIB(pQil), and IncR were predicted in the genome. The draft genome analysis revealed the occurrence of genetic mobile elements positioned around the ARGs, suggesting the ease of dissemination via horizontal gene transfer.ConclusionsThis study reports a comprehensive pathogenomic analysis of MDR-KP isolated from a hospitalized patient. These findings could be relevant for future studies investigating the diversity of antimicrobial resistance and virulence in Egypt.

Vitek 2 system for identification and susceptibility testing of Candida species with detection of fluconazole resistant genes

Vitek 2 system for identification and susceptibility testing of Candida species with detection of fluconazole resistant genes

ACURAT: Advancing tuberculosis detection through assembled PCR & CRISPR for ultra-sensitive Rifampin-resistant analysis testing

ACURAT: Advancing tuberculosis detection through assembled PCR & CRISPR for ultra-sensitive Rifampin-resistant analysis testing

Exploiting Image Processing and Artificial Intelligence Techniques for the Determination of Antimicrobial Susceptibility

Antimicrobial susceptibility tests, achieved through the use of antibiotic-impregnated disks in a suitable laboratory environment, are conducted to determine which antibiotics are effective against the bacteria present in the body of an infected patient. The Kirby–Bauer method, a type of disk diffusion antimicrobial susceptibility test, is currently widely applied in microbiology laboratories due to its proven effectiveness. In our study, we developed an algorithm that utilizes image processing techniques to detect the inhibition zones of bacteria. A certain color depth acts as the threshold for the inhibition zone, with its radius determined according to the size of the reference object. This approach facilitates the measurement of inhibition zones and employs machine learning and deep learning to categorize antibiograms, followed by determination of whether a bacterium on the disk is sensitive or resistant to the antibiotics applied. The focus of this research is creating an automated interpretation system for antimicrobial susceptibility testing using the disk diffusion technique, thus simplifying the measurement and interpretation of inhibition zone sizes.

Evaluation of the Vitek 2 system for antifungal susceptibility testing of Candida auris using a representative international panel of clinical isolates: overestimation of amphotericin B resistance and underestimation of fluconazole resistance.

Although the Vitek 2 system is broadly used for antifungal susceptibility testing of Candida spp., its performance against Candida auris has been assessed using limited number of isolates recovered from restricted geographic areas. We therefore compared Vitek 2 system with the reference Clinical and Laboratory Standards Institute (CLSI) broth microdilution method using an international collection of 100 C. auris isolates belonging to different clades. The agreement ±1 twofold dilution between the two methods and the categorical agreement (CA) based on the Centers for Disease Control and Prevention's (CDC's) tentative resistance breakpoints and Vitek 2-specific wild-type upper limit values (WT-ULVs) were determined. The CLSI-Vitek 2 agreement was poor for 5-flucytosine (0%), fluconazole (16%), and amphotericin B (29%), and moderate for voriconazole (61%), micafungin (67%), and caspofungin (81%). Significant interpretation errors were recorded using the CDC breakpoints for amphotericin B (31% CA, 69% major errors; MaEs) and fluconazole (69% CA, 31% very major errors; VmEs), but not for echinocandins (99% CA, 1% MaEs for both micafungin and caspofungin) for which the Vitek 2 allowed correct categorization of echinocandin-resistant FKS1 mutant isolates. Discrepancies were reduced when the Vitek 2 WT-ULV of 16 mg/L for amphotericin B (98% CA, 2% MaEs) and of 4 mg/L for fluconazole (96% CA, 1% MaEs, 3% VmEs) were used. In conclusion, the Vitek 2 system performed well for echinocandin susceptibility testing of C .auris. Resistance to fluconazole was underestimated whereas resistance to amphotericin B was overestimated using the CDC breakpoints of ≥32 and ≥2 mg/L, respectively. Vitek 2 minimun inhibitory concentrations (MICs) >4 mg/L indicated resistance to fluconazole and Vitek 2 MICs ≤16 mg/L indicated non-resistance to amphotericin B.

Novel automated antifungal susceptibility testing system for yeasts based on dual-detection algorithm of turbidimetry and colorimetry.

Introduction. The increasing prevalence and growing resistance of fungi present a significant peril to public health. There are only four classes of antifungal medicines available today, and few candidates are in clinical trials.Hypothesis/Gap Statement. Rapid and sensitive diagnostic techniques are lacking for most fungal pathogens, and those that do exist are expensive or hard to obtain.Aim. This study aimed to evaluate the feasibility of a novel automated antifungal susceptibility testing system, Fungus AST, in comparison to the broth microdilution method (BMD) recommended by the Clinical and Laboratory Standards Institute (CLSI).Methodology. A total of 101 clinical Candida spp. isolates were collected from the Zengcheng Branch of Nanfang Hospital and subjected to antifungal susceptibility testing. Antifungal susceptibility was assessed using the Fungus AST method and the BMD.Results. In this study, we introduce a novel automated antifungal susceptibility testing system, Fungus AST, which detects the turbidity and/or colour intensity of microdilution wells using a four-wavelength detection technology in real time and is designed to match the growth characteristics of strains over time. Based on our analysis, all reportable ranges of Fungus AST were suitable for clinical fungal isolates in PR China. Within ±twofold dilutions, reproducibility was 100 %. Considering the BMD as a referenced method, ten antifungal agents (anidulafungin, caspofungin, micafungin, fluconazole, voriconazole, posaconazole, itraconazole, amphotericin B, 5-flucytosine and nystatin) showed an essential agreement of >95 %. The category agreement of five antifungal agents (anidulafungin, caspofungin, micafungin, fluconazole and voriconazole) was excellent at >90 %. One Candida albicans isolate and voriconazole showed a major error (ME) (1.7 %), and no other ME or very ME agents were found.Conclusion. Given the above, it can be argued that the utilization of Fungus AST is a discretionary automated approach. More improvements are needed in Fungus AST compared to the BMD system for a wider range of clinical isolates, including different types of fungi.

Evaluation of two commercial broth microdilution systems for dalbavancin susceptibility testing of methicillin-resistant Staphylococcus aureus and other resistant Gram-positive cocci

This study aims to evaluate two commercial broth microdilution (BMD) systems, E1-185-100 (Merlin) and FDANDPF (ThermoFisher), for dalbavancin susceptibility testing in comparison with reference BMD assay. Study collection was composed of 200 non-replicate multidrug-resistant Gram-positive cocci of clinical origin, including 180 methicillin-resistant Staphylococcus aureus, 10 vancomycin-resistant enterococci, seven linezolid-resistant Staphylococcus epidermidis, and three methicillin-resistant coagulase-negative staphylococci. S.aureus ATCC 29213 and Enterococcus faecalis ATCC 29212 reference strains were also included as controls. Testing was performed according to the ISO 20776-1 standard, starting from the same bacterial inoculum, and results were compared according to the ISO 20776-2 standard. Reference BMD showed that 92.6% (187/202) of the strains were susceptible to dalbavancin, whereas few staphylococci and all VanA-producing enterococci showed a resistant phenotype. In comparison with the reference method, Category Agreement and Essential Agreement were 98% (198/202; 95% CI, 95.4-99.3%) and 98% (198/202; 95% CI, 95.4-99.3%) for both Merlin and ThermoFisher panels. A few false susceptibilities were observed, for both commercial systems, with dalbavancin-resistant staphylococci. BIAS values of 11% and 3% were calculated for the Merlin and ThermoFisher systems, respectively. This study, reporting the first evaluation of the two commercially available BMD assays for dalbavancin susceptibility testing, revealed an overall good correlation with reference BMD, although with some underestimation tendency of MIC values by both commercial systems. Further studies involving a higher number of resistant isolates will be necessary to better evaluate this issue.

Correction for Göransson et al., "Performance of a System for Rapid Phenotypic Antimicrobial Susceptibility Testing of Gram-Negative Bacteria Directly From Positive Blood Culture Bottles".

Correction for Göransson et al., "Performance of a System for Rapid Phenotypic Antimicrobial Susceptibility Testing of Gram-Negative Bacteria Directly From Positive Blood Culture Bottles".

Photonic Si microwell architectures for rapid antifungal susceptibility determination of Candida auris.

We present the application of a photonic silicon chip-based optical sensor system for expeditious and phenotypic antifungal susceptibility testing. This label-free diagnostic assay optically monitors the growth of Candida auris at varying antifungal concentrations on a microwell-structured silicon chip in real-time, and antifungal susceptibility is detected within 6 h, four times faster than in the current gold standard method.

Evaluating Quality Management and Diagnostics Microbiology Performance Within an International External Quality Assessment (EQA) Program Serving National One Health Sector Reference Laboratories Across Asia: Experience Amid the Coronavirus Disease 2019 (COVID-19) Pandemic.

Strengthening external quality assessment (EQA) services across the One Health sector supports implementation of effective antimicrobial resistance (AMR) control strategies. Here we describe and compare 2 different approaches for conducting virtual laboratory follow-up assessments within an EQA program to evaluate quality management system (QMS) and procedures for pathogen identification and antimicrobial susceptibility testing (AST). During the coronavirus disease 2019 (COVID-19) pandemic in 2021 and 2022, 2 laboratory assessment approaches were introduced: virtual-based and survey-based methodologies. The evaluation of 2 underperforming Animal Health laboratories through a virtual-based approach occurred between May and August 2021. This evaluation encompassed the utilization of 3 online meetings and document reviews, performed subsequent to the execution of EQA procedures. Within a distinct group of laboratories, the survey-based assessment was implemented from December 2021 to February 2022, also following EQA procedures. This phase encompassed the dissemination of an online survey to 31 participating laboratories, alongside a sole online consultation meeting involving 4 specific underperforming laboratories. The virtual-based assessment post-EQA aimed to identify gaps and areas for improvement in the laboratory's practices for pathogen identification and AST. This approach was, however, time-intensive, and, hence, only 2 laboratories were assessed. In addition, limited interactions in virtual platforms compromised the assessment quality. The survey-based post-EQA assessment enabled evaluation of 31 laboratories. Despite limitations for in-depth analysis of each procedure, gaps in QMS across multiple laboratories were identified and tailored laboratory-specific recommendations were provided. Reliable internet and plans for efficient time management, post-EQA virtual laboratory follow-up assessments are an effective alternative when conducting onsite evaluation is infeasible as observed during the COVID-19 pandemic, although the successful implementation of remediation plans will likely require in person assessments. We advocate application of hybrid approaches (both onsite and virtual) for targeted capacity building of AMR procedures with the ability to implement and oversee the process.