Contribution of MALDI-TOF mass spectrometry and machine learning including deep learning techniques for the detection of virulence factors of Clostridioides difficile strains.

Clostridioides difficile (CD) infections are defined by toxins A (TcdA) and B (TcdB) along with the binary toxin (CDT). The emergence of the 'hypervirulent' (Hv) strain PR 027, along with PR 176 and 181, two decades ago, reshaped CD infection epidemiology in Europe. This study assessed MALDI-TOF mass spectrometry (MALDI-TOF MS) combined with machine learning (ML) and Deep Learning (DL) to identify toxigenic strains (producing TcdA, TcdB with or without CDT) and Hv strains. In total, 201 CD strains were analysed, comprising 151 toxigenic (24 ToxA+B+CDT+, 22 ToxA+B+CDT+ Hv+ and 105 ToxA+B+CDT-) and 50 non-toxigenic (ToxA-B-) strains. The DL-based classifier exhibited a 0.95 negative predictive value for excluding ToxA-B- strains, showcasing accuracy in identifying this strain category. Sensitivity in correctly identifying ToxA+B+CDT- strains ranged from 0.68 to 0.91. Additionally, all classifiers consistently demonstrated high specificity (>0.96) in detecting ToxA+B+CDT+ strains. The classifiers' performances for Hv strain detection were linked to high specificity (≥0.96). This study highlights MALDI-TOF MS enhanced by ML techniques as a rapid and cost-effective tool for identifying CD strain virulence factors. Our results brought a proof-of-concept concerning the ability of MALDI-TOF MS coupled with ML techniques to detect virulence factor and potentially improve the outbreak's management.

Evaluation of ceftolozane-tazobactam susceptibility on a French nationwide collection of Enterobacterales.

OBJECTIVES: Ceftolozane-tazobactam (C/T) proved its efficacy for the treatment of infections caused by non-carbapenemase producing Pseudomonas aeruginosa and Enterobacterales. Here, we aimed to provide susceptibility data on a large series of Enterobacterales since the revision of EUCAST categorization breakpoints in 2020. METHODS: First, C/T susceptibility was determined on characterized Enterobacterales resistant to third generation cephalosporins (3GCs) (extended spectrum ß-lactamase [ESBL] production or different levels of AmpC overexpression) (n = 213) and carbapenem-resistant Enterobacterales (CRE) (n = 259), including 170 carbapenemase producers (CPE). Then, 1632 consecutive clinical Enterobacterales responsible for infection were prospectively collected in 23 French hospitals. C/T susceptibility was determined by E-test® (biomérieux) and broth microdilution (BMD) (Sensititre™, Thermo Scientific) to perform method comparison. RESULTS: Within the collection isolates, 88% of 3GC resistant strains were susceptible to C/T, with important variation depending on the resistance mechanism: 93% vs. 13% susceptibility for CTX-M and SHV-ESBL producers, respectively. Only 20% of the CRE were susceptible to C/T. Among CPE, 80% of OXA-48-like producers were susceptible to C/T, whereas all metallo-ß-lactamase producers were resistant. The prospective study revealed that 95.6% of clinical isolates were susceptible to C/T. Method comparison performed on these 1632 clinical isolates demonstrated 99% of categorization agreement between MIC to C/T determined by E-test® in comparison with the BMD (reference) and only 74% of essential agreement. CONCLUSION: Overall, C/T showed good activity against wild-type Enterobacterales, AmpC producers, and ESBL-producing Escherichia coli but is less active against ESBL-producing Klebsiella pneumoniae, and CRE. E-test® led to an underestimation of the MICs in comparison to the BMD reference.

Decreased Sensitivity of Rapid Antigen Test Is Associated with a Lower Viral Load of Omicron than Delta SARS-CoV-2 Variant.

Large-scale screening for SARS-CoV-2 infection is an important tool for epidemic prevention and control. The appearance of new variants associated with specific mutations can call into question the effectiveness of rapid diagnostic tests (RDTs) deployed massively at national and international levels. We compared the clinical and virological characteristics of individuals infected by Delta or Omicron variants to assess which factors were associated with a reduced performance of RDT. A commercially available RDT as well as the evaluation of the viral load (VL) and the detection of replicate intermediates (RIs) were carried out retrospectively on positive SARS-CoV-2 nasopharyngeal specimens from health care workers of the Pitié-Salpêtrière Hospital infected by the Delta or Omicron variant between July 2021 and January 2022. Of the 205 samples analyzed (104 from individuals infected with Delta and 101 with Omicron), 176 were analyzed by RDT and 200 by RT-PCR for VL and RIs. The sensitivity of the TDR for Omicron was significantly lower than that observed for Delta (53.8% versus 74.7%, respectively, P < 0.01). Moreover, the Delta VL was significantly higher than that measured for Omicron (median Ct 21.2 versus 24.1, respectively, P < 0.01) and associated with the positivity of the RDT in multivariate analysis. We demonstrate a lower RDT sensitivity associated with a lower VL at the time of diagnosis on Omicron-infected individuals in comparison to those infected with the Delta variant. This RDT lower sensitivity should be taken into account in the large-scale screening strategy and in particular in case of strong suspicion of infection where testing should be repeated. IMPORTANCE Previous reports have shown a variability in the diagnostic performance of RDTs. In the era of SARS-CoV-2 variants and the use of RDT, mutation associated with these variants could affect the test performance. We evaluate the sensitivity of the RDT Panbio COVID-19 Ag (Abbott) with two variants of concern (VOC), the Delta and Omicron variants. In order to investigate whether clinical characteristics or virological characteristics can affect this sensitivity, we collected clinical information and performed a specific RT-PCR that detected the RIs as a marker of the viral replication and viral cycle stage. Our results showed that Omicron was less detected than the Delta variant. A lower viral load of Omicron variant in comparison to Delta variant explained this decreased sensitivity, even if they are at the same stage of the disease and the viral cycle and should be taken into account with the use of RDT as diagnostic tool.

Gene Panel Sequencing of Patients With Monogenic Diabetes Brings to Light Genes Typically Associated With Syndromic Presentations.

Gene panel sequencing (NGS) offers the possibility of analyzing rare forms of monogenic diabetes (MgD). To that end, 18 genes were analyzed in 1,676 patients referred for maturity-onset diabetes of the young genetic testing. Among the 307 patients with a molecular diagnosis of MgD, 55 (17.9%) had a mutation in a gene associated with a genetic syndrome. Of the patients with mutations, 8% (n = 25) carried the m.3243A>G variant associated with maternally inherited diabetes and deafness. At the time of referral very few had reported hearing loss or any other element of the typical syndromic presentation. Of the patients, 6% had mutation in HNF1B even though the typical extrapancreatic features were not known at the time of referral. Surprisingly, the third most prominent etiology in these rare forms was the WFS1 gene, accounting for 2.9% of the patients with pathogenic mutations (n = 9). None of them displayed a Wolfram syndrome presentation even though some features were reported in six of nine patients. To restrict the analysis of certain genes to patients with the respective specific phenotypes would be to miss those with partial presentations. These results therefore underlie the undisputable benefit of NGS strategies even though the situation implies cascade consequences both for the molecular biologist and for the clinician.

Assessment of the In Vitro Activities of Ceftolozane/Tazobactam and Ceftazidime/Avibactam in a Collection of Beta-Lactam-Resistant Enterobacteriaceae and Pseudomonas aeruginosa Clinical Isolates at Montpellier University Hospital, France.

Objective: To assess in vitro ceftolozane/tazobactam (C/T) and ceftazidime/avibactam (CZA) activity in beta-lactam-resistant Enterobacteriaceae and Pseudomonas aeruginosa clinical isolates from major carbapenem-using Departments at Montpellier University Hospital, France. Materials and Methods: We tested third-generation cephalosporin-resistant Enterobacteriaceae (by production of extended spectrum ß-lactamase or other mechanisms, mainly AmpC beta-lactamases) and ceftazidime- and/or carbapenem-resistant P. aeruginosa strains isolated from clinical samples of patients hospitalized from January 2017 to May 2017 and August 2016 to July 2017, respectively. We also included all OXA-48 beta-lactamase-producing Enterobacteriaceae strains isolated in the whole hospital from October 2015 to May 2017. We used the 2017 European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines for minimal inhibitory concentration interpretation. Results: Among the 62 cephalosporin-resistant Enterobacteriaceae strains, 60 (97%) were susceptible to CZA and 34 (65%) to C/T. The two CZA-resistant Klebsiella pneumoniae isolates produced (i) NDM-carbapenemase and extended-spectrum beta-lactamase (ESBL) and (ii) ESBL CTXM-15 and OXA-1 associated with impermeability. Moreover, 31 of the 42 P. aeruginosa strains (74%) were susceptible to CZA and 37 (88%) to C/T. Finally, 26/27 (96%) of OXA-48 beta-lactamase-producing Enterobacteriaceae were susceptible to CZA and 8/27 (30%) to C/T. Conclusions: At our hospital, CZA and C/T offer a carbapenem-sparing alternative for resistant gram-negative pathogens and could be a salvage therapy for carbapenem-resistant pathogens.