Fast-track identification of CTX-M-extended-spectrum-ß-lactamase- and carbapenemase-producing Enterobacterales in bloodstream infections: implications on the likelihood of deduction of antibiotic susceptibility in emergency and internal medicine departments.

This study aims at presenting a reliable fast-track diagnostics for the detection of CTX-M ESBL- (CTX-M-p) and carbapenemase-producers (CA-p) directly from blood cultures (BCs) of patients with Enterobacterales (EB) bloodstream infections (BSIs) admitted in emergency and internal medicine departments and its contribution in estimation of in vitro antibiotic susceptibility. A fast-track workflow including MALDI-TOF species identification and two lateral flow immunochromatographic assays for the detection of CTX-M-p and CA-p directly from BCs was performed in parallel with conventional routine, and results were compared. A total of 236 BCs of patients suffering from EB BSI were included. Accuracy of the fast-track workflow ranged from 99.6 to 100%. Among E. coli isolates, CTX-M-p (20.5%) were susceptible to ceftolozane-tazobactam (C/T, 97%), ceftazidime-avibactam (CZA, 100%), and piperacillin-tazobactam (TZP, 84.8%), whereas CTX-M-and-main-carbapenemases-non-producer (CTX-M-CA-np, 79.5%) isolates were susceptible to all the antibiotics tested. Among K. pneumoniae isolates, CTX-M-p (23.3%) were poorly susceptible to TZP (40%) but widely susceptible to C/T (90%), CZA (100%), and amikacin (90%), whereas CTX-M-CA-np (55.8%) were also susceptible to cefepime. CA-p K. pneumoniae (20.9%) were susceptible to CZA (88.9%). All the species other than E. coli and K. pneumoniae were CTX-M-CA-np and were widely susceptible to the antibiotics tested except for isolates of the inducible and derepressed AmpC- or AmpC/ESBL-p species. Rapid identification of species and phenotype together with knowledge of local epidemiology may be crucial to determine the likelihood of deduction of in vitro antibiotic susceptibility on the same day of positive BC processing.

Impact of NG-Test CTX-M MULTI Immunochromatographic Assay on Antimicrobial Management of Escherichia coli Bloodstream Infections.

Rapid detection of extended-spectrum-ß-lactamase (ESBL) is of paramount importance to accelerate clinical decision-making, optimize antibiotic treatment, and implement adequate infection control measures. This study was aimed at assessing the impact of direct detection of CTX-M ESBL-producers on antimicrobial management of Escherichia coli bloodstream infections over a 2-year period. This study included all E. coli bloodstream infection (BSI) events that were serially processed through a rapid workflow with communication to the clinicians of direct detection of CTX-M ESBL-producers and conventional culture-based workflow. Antimicrobial management was retrospectively analyzed to assess the contribution of the rapid test result. A total of 199 E. coli BSI events with a report of direct detection of CTX-M ESBL production results were included. Of these, 33.7% (n = 67) and 66.3% (n = 132) were reported as positive and negative CTX-M producers, respectively. Detection of CTX-M positive results induced more antibiotic therapy modifications (mainly towards carbapenem-containing regimens, p < 0.01), and antimicrobial susceptibility testing results of CTX-M ESBL-producing E. coli isolates induced more antibiotic escalations towards carbapenem-containing regimens (p < 0.01). Direct detection of CTX-M ESBL-producing E. coli resulted in a remarkable rate of antibiotic optimizations on the same day of blood culture processing. Observing antibiotic management following the availability of antimicrobial susceptibility testing results, additional early optimizations in escalation could probably have been made if the rapid test data had been used. Detection of CTX-M negative results resulted in few therapeutic changes, which could have probably been higher, integrating epidemiological and clinical data.

Light Scattering Technology and MALDI-TOF MS in the microbiological fast-track of bloodstream infections: potential impact on antimicrobial treatment choices in a real-life setting.

Introduction. Rapid identification (ID) and antimicrobial susceptibility testing (AST) of bloodstream infections (BSI) pathogens are fundamental to switch from empirical to targeted antibiotic therapy improving patients outcome and reducing antimicrobial resistance spreading.Hypothesis. The adoption of a rapid microbiological protocol (RP) based on Matrix-Assisted Laser Desorption Ionization-Time Of Flight Mass Spectrometry (MALDI-TOF MS) and Light Scattering Technology (LST) for rapid diagnosis of BSI could positively impact on patients' antimicrobial management.Aim. The study aim was to evaluate a RP for BSI microbiological diagnosis in terms of accuracy, turnaround time (TAT) and potential therapeutic impact.Methodology. A prospective observational study was conducted: monomicrobial bacterial blood cultures of septic patients were analysed in parallel by RP and standard protocol (SP). In RP the combination of MALDI-TOF MS and LST was used for rapid ID and AST assessments, respectively. To determine the potential impact of RP on antimicrobial therapy management, clinicians were interviewed on therapeutic decisions based on RP and SP results. RP accuracy, TAT and impact were evaluated in comparison to SP results.Results. A total of 97 patients were enrolled. ID and AST concordance between RP and SP were 96.9 and 94.7 %, respectively. RP technical and real-life TAT were lower than SP (6.4 h vs. 18.4 h; 9.5 vs. 27.1 h). The agreement between RP- and SP-based therapeutic decisions was 90.7 (90 % CI 84.4-95.1). RP results could produce 24/97 correct antibiotic changes with 18/97 possible de-escalations and 25/97 prompt applications of infection control precautions.Conclusion. With the application of RP in BSI management, about one-fourth of patients may safely benefit from early targeted antibiotic therapy and infection control policies with one working day in advance in comparison to conventional methods. This protocol is feasible for clinical use in microbiology laboratories and potentially helpful for Antimicrobial Stewardship.

Application of FT-IR Spectroscopy for Mycobacterium abscessus complex subspecies differentiation.

Mycobacterium abscessus complex (MABSC) subspecies differentiation improves patients' therapy and outcome. Fourier-Transform-Infrared Spectroscopy (FT-IRS) was applied for subspecies discrimination of 15 strains on different media: Löwenstein-Jensen showed the best resolution power; Linear Discriminant Analysis model differentiated M. abscessus susbsp. abscessus from M. abscessus subsp. massiliense. FT-IRS has a potential role in rapidly MABSC subspecies identification.

Evaluation of BD Phoenix and Microscan WalkAway for determination of fosfomycin susceptibility in Staphylococcus aureus.

We evaluate the performance of BD Phoenix (BD Diagnostic; Hunt Valley, MD) and MiscroScan WalkAway (Beckman Coulter Inc; Carlsbad, CA) systems versus reference agar dilution method for fosfomycin susceptibility determination in 200 Staphylococcus aureus clinical isolates. Both methods exhibit ≤89.0% of categorica agreement and ≥63.3% of very major error. All commercial antimicrobial susceptibility systems show poor concordance with reference method.

Carbapenemase detection testing in the era of ceftazidime/avibactam-resistant KPC-producing Enterobacterales: A 2-year experience.

OBJECTIVES: The aim of this study was to investigate the prevalence of ceftazidime/avibactam (CZA) resistance among carbapenemase-producing Enterobacterales (CPE) blood culture isolates as well as the performance of the main carbapenemase phenotypic detection methods to identify KPC variants associated with CZA resistance. METHODS: Non-duplicate CPE strains isolated from blood cultures during 2018-2020 were tested for antimicrobial susceptibility. Molecular testing was used to identify carbapenemase-producers. Strains harbouring blaKPC and with a CZA minimum inhibitory concentration (MIC) ≥8 mg/L were investigated by sequencing. Subsequentially, five phenotypic carbapenemase detection methods were evaluated on these strains, namely the modified carbapenem inactivation method (mCIM), Rapidec® Carba NP, the disk diffusion synergy test, NG-Test CARBA® 5 and RESIST-5 O.O.K.N.V. RESULTS: Overall, the CZA resistance rate was high (13.7%) and remained relevant (5.9%) excluding metallo-ß-lactamases-producers. All isolates harbouringblaKPC mutants (n = 8) were associated with reduced carbapenem MICs and negative results by all detection methods based on revelation of enzyme activity. Lateral flow immunoassays failed to detect KPC-31 (n = 4) and KPC-33 (n = 2) but correctly identified KPC-14 (n = 2). Conversely, isolates harbouring wild-type KPC genes (n = 3) were associated with high-level CZA resistance and carbapenem resistance and tested positive by all of the evaluated methods. CONCLUSION: In the era of CZA-based therapies, molecular blaKPC identification followed by a carbapenem hydrolysis-based phenotypic assay could be the most reasonable diagnostic algorithm to detect all KPC-producers and to identify mutants associated with impaired carbapenemase activity and CZA resistance.