Impact of EUCAST rapid antimicrobial susceptibility testing (RAST) on management of Gram-negative bloodstream infection.

OBJECTIVES: During bloodstream infections, reducing the time to antimicrobial susceptibility testing is crucial to initiation of early appropriate antibiotic therapy. For Gram-negative infections, a phenotypic approach remains necessary. Rapid antimicrobial testing (RAST) is a recently developed phenotypic EUCAST method. The goal of this study was to evaluate the accuracy and clinical impact of RAST. PATIENTS AND METHODS: From September 2020 to August 2021, Gram-negative episodes with positive blood culture detected in the morning were included in the RAST group. Categorical agreement of RAST with conventional antimicrobial testing on strains was determined. To assess antibiotic management and patient outcomes, the RAST group was compared with a control group (CG) with positive blood culture detected in the afternoon for which overnight antimicrobial testing was performed. RESULTS: The RAST group included 61 episodes from 61 patients, while the CG group included 49 episodes from 48 patients. While RAST performed on 41 E. coli, 11 K. pneumoniae and 9 P. aeruginosa strains highlighted 99.3 % of categorical agreement, 7.4 % of unreadable zones and 9.4 % of technical uncertainty area at 4 h incubation were also reported. For the RAST group, effective antibiotic therapy was prescribed in 100 % of patients on the day of positive blood culture (day 1) vs 88 % in CG (p = 0,007). As for beta-lactams on day 1, RAST led to 9 escalations and 6 de-escalations. Mortality and length of hospital stay did not significantly differ between the two groups. CONCLUSION: RAST improves management of antibiotic therapy in patients with Gram-negative sepsis.

Distribution of Achromobacter Species in 12 French Cystic Fibrosis Centers in 2020 by a Retrospective MALDI-TOF MS Spectrum Analysis.

Achromobacter spp. are nonfermenting Gram-negative bacilli mainly studied among cystic fibrosis (CF) patients. The identification of the 19 species within the genus is time-consuming (nrdA-sequencing), thus data concerning the distribution of the species are limited to specific studies. Recently, we built a database using MALDI-TOF mass spectrometry (MS) (Bruker) that allows rapid and accurate species identification and detection of the multiresistant epidemic clones: A. xylosoxidans ST137 spreading among CF patients in various French and Belgium centers, and A. ruhlandii DES in Denmark. Here, we first assessed whether species identification could be achieved with our database solely by analysis of MS spectra without availability of isolates. Then, we conducted a multicentric study describing the distribution of Achromobacter species and of the clone ST137 among French CF centers. We collected and analyzed with our local database the spectra of Achromobacter isolates from 193 patients (528 samples) from 12 centers during 2020. In total, our approach enabled to conclude for 502/528 samples (95.1%), corresponding to 181 patients. Eleven species were detected, only five being involved in chronic colonization, A. xylosoxidans (86.4%), A. insuavis (9.1%), A. mucicolens (2.3%), A. marplatensis (1.1%) and A. genogroup 3 (1.1%). This study confirmed the high prevalence of A. xylosoxidans in chronic colonizations and the circulation of the clone A. xylosoxidans ST137 in France: four patients in two centers. The present study is the first to report the distribution of Achromobacter species from CF patients samples using retrospective MALDI-TOF/MS data. This easy approach could enable future large-scale epidemiological studies.

Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry for Rapid Detection of Isolates Belonging to the Epidemic Clones Achromobacter xylosoxidans ST137 and Achromobacter ruhlandii DES from Cystic Fibrosis Patients.

Achromobacter spp. are increasingly reported among cystic fibrosis patients. Genotyping requires time-consuming methods such as multilocus sequence typing or pulsed-field gel electrophoresis. Therefore, data on the prevalence of multiresistant epidemic clones, especially A. xylosoxidans ST137 (AxST137) and the Danish epidemic strain A. ruhlandii (DES), are lacking. We recently developed and published a database for Achromobacter species identification by matrix-assisted laser desorption-ionization-time of flight mass spectrometry (MALDI-TOF MS; Bruker Daltonics). The aim of this study was to evaluate the ability of the MALDI-TOF MS to distinguish these multiresistant epidemic clones within Achromobacter species. All the spectra of A. xylosoxidans (n = 1,571) and A. ruhlandii (n = 174) used to build the local database were analyzed by ClinProTools, MALDI Biotyper PCA, MALDI Biotyper dendrogram, and flexAnalysis software for biomarker peak detection. Two hundred two isolates (including 48 isolates of AxST137 and 7 of DES) were tested. Specific biomarker peaks were identified: absent peak at m/z 6,651 for AxST137 isolates and present peak at m/z 9,438 for DES isolates. All tested isolates were well typed by our local database and clustered within distinct groups (ST137 or non-ST137 and DES or non-DES) no matter the MALDI-TOF software or only by simple visual inspection of the spectra by any user. The use of MALDI-TOF MS allowed us to identify isolates of A. xylosoxidans belonging to the AxST137 clone that spread in France and Belgium (the Belgian epidemic clone) and of A. ruhlandii belonging to the DES clone. This tool will help the implementation of segregation measures to avoid interpatient transmission of these resistant clones.

Sputum versus nasopharyngeal samples for the molecular diagnosis of respiratory viral infection in cystic fibrosis: A pilot study.

Viruses are important agents in lung function deterioration in Cystic Fibrosis (CF). To date, no standard operating procedures (SOPs) have been established to determine which sampling method is the most effective for an optimal virological diagnosis of respiratory viral infections in CF. Here we investigated the performances of two sampling sites, sputum samples versus nasopharyngeal (NP) swabs, for thirty participants from three CF centres presenting an acute respiratory infection. Sputum and NP samples were simultaneously collected and multiplex PCR targeting 16 to 18 viruses were performed. Viruses were detected for 18/30 patients (60%). A high concordance between the sputum and NP samples was observed in 25 (83%) paired samples of which 13 tested positive and 12 tested negative. These results highlighted the relevance of sputum sampling for diagnostic of respiratory viruses in CF, which is less invasive and better accepted by CF patients than NP, and allows accurate bacterial detection.

Rapid identification of fungi from respiratory samples by Bruker Biotyper matrix-assisted laser desorption/ionisation time-of-flight using ID-FUNGI plates.

Identification of moulds is crucial for the clinical management of patients. The goal of this study was to evaluate the new ID-FUNGI plate (IDFP) for the identification of moulds by MALDI Biotyper. IDFP was compared with Sabouraud with gentamicin and chloramphenicol plate (SAB) for the identification of 80 moulds from respiratory samples and eight reference strains. With the direct transfer method, species identification rose from 6% with SAB to 68% with IDFP using score cut-off 2 and from 20 to 75% using cut-off 1.7 (p < 0.001). Our study highlights that the new IDFP improves mycological diagnostic and workflow in laboratories.

[Contribution and evolution of blood culture quality indicators]. / Apports et perspectives d'évolution des indicateurs qualité de l'hémoculture.

The monitoring of quality indicators, combined with a detailed risk analysis, validates the process of automated blood culture. Here we report the methodology of 5 years monitoring for 5 indicators at the Biology Department of Foch Hospital: volume sampled, proportion of contaminants, proportion of positive blood cultures in each instrument and drawer, epidemiological indicator and proportion of false-positive instrument signals. The results obtained were outside the expected target for the volume sampled and were acceptable for the other indicators. The analysis of these results leads us to discuss the evolution of quality indicators and more particularly the implementation of corrective measures, their periodicity, their relevance as well as the need to refine their results to carry out targeted actions.