Multicenter interlaboratory study of routine systems for the susceptibility testing of temocillin using a challenge panel of multidrug-resistant strains.

Accurate susceptibility result of temocillin (TMO) is important for treating infections caused by multidrug-resistant Enterobacterales. This multicenter study aimed to investigate the performance of routine temocillin testing assays against Enterobacterales challenging strains. Forty-seven selected clinical isolates were blindly analyzed by 12 Belgian laboratories using VITEK® 2 (n = 5) and BD Phoenix™ (n = 3) automated systems, ETEST® gradient strip (n = 3), and disk (3 brands) diffusion method (DD; n = 6) for temocillin susceptibility using standardized methodology. Results were interpreted using EUCAST 2023 criteria and compared to the broth microdilution (BMD; Sensititre™ panel) method used as gold standard. Methods' reproducibility was assessed by testing 3 reference strains in triplicate. A total of 702 organism-drug results were obtained against 33 TMO-susceptible and 14 TMO-resistant isolates. Excluding Proteae species (P. mirabilis and M. morganii), the essential agreement rates were excellent (91.5-100%) for all MIC-based methods. The highest category agreement was achieved by ETEST® (97.5%) followed by VITEK® 2 (93.2%), disk diffusion (91.6%), and BD Phoenix™ (88.5%). BD Phoenix™ and paper disk diffusion overcalled resistance (11.5% and 6.8% of major discrepancies, respectively), while ROSCO tablets diffusion and VITEK® 2 generated higher very major discrepancies (7.1% and 4.2% respectively). Inter-assay reproducibility was unsatisfactory using recommended E. coli ATCC 25922 strain but was excellent with E. coli ATCC 35218 and K. pneumoniae ATCC 700603 strains. This interlaboratory study suggests that routine testing methods provide accurate and reproducible TMO categorization results except for Proteae species.

Undisclosed interference in 25-OH-Vitamin D immunoassay on Liaison XL analyzer when using heparin plasma tubes.

This study investigates the impact of sample type on the measurement of 25-OH-vitamin D using the Liaison XL (Diasorin) and Cobas e801 (Roche). This investigation was motivated by the need to optimize sample volume usage, which led us to adopt the use of heparin plasma, an alternative proposed by Diasorin in their specification. Discordant and unexplainable results were observed, prompting us to evaluate the effect of sample type on the accuracy of the 25-OH-vitamin D measurements. We collected 34 different paired samples from a randomly selected patients who had two types of tubes taken simultaneously: serum-gel and lithium-heparin plasma tubes. The 25-OH-vitamin D levels were measured using Cobas e801 and Liaison. Statistical analysis was performed using the Mann-Whitney test to calculate the p-value. Biases were also calculated. When comparing the heparin matrix with the serum matrix on the Liaison XL analyzer, a higher proportion (p < .0001; 79% versus 64%) of patients were classified in the 'normal group', while fewer were classified in the 'insufficiency' or 'deficiency group'. The heparin tubes on the Liaison XL analyzer showed a mean bias of 57.5%) (p-value < .001; 95%CI: 37.6-77.4) compared to the serum tubes. On the other hand, the heparin tubes on the Cobas e801 analyzer showed a mean bias of -0.2% (95%CI: -4.8 to 4.5) compared to the serum tubes. It is imperative for laboratory professionals to be aware of this interference for an accurate measurement of 25-OH-vitamin D levels on the Liaison XL. Further research is needed to understand the mechanism of this interference.

Evaluation of the Bruker® MBT Sepsityper IVD module for the identification of polymicrobial blood cultures with MALDI-TOF MS.

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) considerably reduces timeframe required from initial blood culture positivity towards complete bacterial identification. However, rapid identification of polymicrobial blood cultures remains challenging. We evaluated the performances of the Bruker® MBT Sepsityper IVD module on MALDI-TOF MS for the direct identification of polymicrobial blood culture bottles. This module has the ability to give a strong indication that a sample contains a mixture of organisms and to identify two of them. Blood culture bottles considered as polymicrobial using routine subculture were collected and processed using the Sepsityper kit. MALDI-TOF MS identification was performed using the MBT Compass IVD software including the Sepsityper module. From 143 polymicrobial blood culture bottles tested, 34.3% (49/143) were completely identified by the module. Both microorganisms were more easily detected by the module in samples containing two pathogens than in samples containing two contaminants (36.8% vs 29.4%). Additionally, in more than half of the samples, the module detected 1 of the different microorganisms contained in the same vial. In these cases, with a pathogen and contaminant in the same sample, the module detected the pathogen in more than 80%. The Sepsityper module identified 14 microorganisms which were not recovered by conventional culture methods. The Bruker® MBT Sepsityper IVD module contributed to a valuable identification of polymicrobial blood cultures in more than a third of all cases. Conventional culture methods are still required to complete the results and to carry on susceptibility testing.

Implementation of the new VIRTUO blood culture system: evaluation and comparison to the 3D system using simulated blood cultures.

PURPOSE: To evaluate the performances of the newly approved BacT/ALERT VIRTUO blood culture system for the recovery of bloodstream pathogens and compare it to the BacT/ALERT 3D system. METHODS: Simulated blood cultures of eight clinically relevant microorganisms were used: Bacteroides fragilis (ATCC 25285), Escherichia coli (ATCC 25922), Haemophilus influenzae (ATCC 49247), Pseudomonas aeruginosa (ATCC 27853), Enterococcus faecalis (ATCC 29212), Staphylococcus aureus (ATCC 29213), Streptococcus pneumoniae (ATCC 49619) and Candida krusei (ATCC 6258). Criteria for comparison were culture positivity and time to detection (TTD). The effects of delayed entry on recovery and TTD were also evaluated. RESULTS: The VIRTUO exhibited around 3 h faster detection time compared to the 3D system. (p < 0.01) for aerobic and facultative microorganisms. The difference in TTD was greatest for the B. fragilis, with a median difference of 46.67 h. The anaerobic bottle of the VIRTUO (FN Plus) did not support the growth of obligate aerobes, whereas the 3D did so. Delayed entry (studied with an E. Coli isolate) had no effect on the recovery rate but proportionally reduced TTD. CONCLUSIONS: The VIRTUO performed better than the 3D in terms of TTD and hands-on-time. FN Plus vial appears to be more efficient than the SN bottle in the recovery of anaerobes.