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With the increase in antimicrobial resistance, fast reporting of antimicrobial susceptibility testing (AST) results is becoming increasingly important. EUCAST developed a method for rapid AST (RAST) directly from the broth of positive blood cultures (BC). Inhibition zones are read after 4, 6, and 8 h, with specific breakpoints per time point. We evaluated the RAST method based on EUCAST disk diffusion methodology with inoculation of BC broth using WASPLab® (inclusive Colibrí™ and Radian®). Forty-nine non-duplicate strains were tested: Escherichia coli n = 17, Klebsiella pneumoniae n = 7, Pseudomonas aeruginosa n = 4, Acinetobacter baumannii n = 2, Staphylococcus aureus n = 10, Enterococcus faecalis n = 6, and Enterococcus faecium n = 3. Results were compared to direct AST and standardized AST. Good categorical agreement was obtained at all time points for all groups, except P. aeruginosa. RAST cut-offs for extended-spectrum β-lactamase (ESBL)-producing Enterobacterales enabled the detection of all included ESBL isolates (n = 5) at all time points, except for 1 E. coli ESBL after 4 h. RAST cut-offs for carbapenemase-producing Enterobacterales enabled the detection of only one carbapenemase after 6 h. However, all carbapenemases (n = 3) were correctly detected after 8 h. Two methicillin-resistant S. aureus were included; both were correctly categorized as cefoxitin-resistant at 6 and 8 h. At 4 h, there was insufficient growth for inhibition zone interpretation. EUCAST RAST is a fast supplementary tool for direct AST of positive BC. WASPLab® provides a significant advantage as pictures are made automatically implicating that we are not strictly bound to the time points for inhibition zone interpretation. [ABSTRACT FROM AUTHOR]

Urinary tract infection diagnosis and management generally involves a 48-h microbiological delay to obtain the antibiotic susceptibility test (AST) results. In the context of multidrug resistance, reducing the time to obtain AST results is an essential factor, allowing for more timely appropriate treatment. We conducted a single-centre prospective study on urinary samples meeting two criteria: significant leukocyturia > 50/mm3 and exclusive presence of Gram-negative bacilli on direct examination. AST were performed by direct inoculation on Mueller-Hinton Rapid-SIR (MHR-SIR) agar. We evaluated the time to antibiotic adaptation by the antimicrobial stewardship team according to rapid AST results. Patients were subsequently excluded from the study if asymptomatic bacteria were confirmed, or in the absence of clinical data. Seventy patients were included. Mean age of patients was 68.8 years (± 21.3). Empirical antibiotic treatment were mainly based on third generation cephalosporins (n = 33), fluoroquinolones (n = 15), beta-lactamin/beta-lactamase inhibitors (n = 7), fosfomycin and nitrofurantoin (n = 5, each). The average time to obtain results was 7.2 h (± 1.6 h). Adaptation of therapy following MHR-SIR was performed for 29 patients (41%) with early switch to oral antibiotics, de-escalation or escalation in respectively 72.3%, 30%, and 11% of cases. Time saving of MHR-SIR compared with the standard technique was 42.6 (± 16.7) h. This study showed that rapid antibiotic susceptibility test results, using MHR-SIR method directly from urine, can be obtained 40 h earlier than conventional AST. The study also demonstrated significant clinical impact on the selection and reduction of the antibiotic therapy spectrum. [ABSTRACT FROM AUTHOR]

The standard method for the diagnosis of urinary tract infections is urine culture that requires 18-48 h for the identification of the bacteria and an additional 24 h until the results of antimicrobial susceptibility testing (AST) are available. We evaluated here a rapid AST method by disc diffusion performed directly on urine samples with a delay of 8 h. A total of 245 urine samples with monobacterial Gram negative observed on microscopy were tested in parallel by two AST methods. Rapid AST method was performed directly on urine samples using Rapid Mueller-Hinton (MHR-SIR) with 8-h incubation before reading and standard method was performed as usual. We compared the categorical agreement and the correlation between the diameters obtained by standard method and by MHR-SIR directly on urine samples. Over the 5285 tested combinations, we observed 5172 (97.9%) categorical agreement, 82 (1.5%) minor errors, 17 (0.3%) major errors, and 14 (0.3%) very major errors. Our results showed an excellent categorical agreement and correlations between diameters for MHR-SIR and standard methods. MHR-SIR performed directly on urine samples with monomicrobial Enterobacteriacae can predict the result of overall AST profile in 8 h with reliable results. The main advantage of MHR-SIR is that it offers the possibility of obtaining results 40 h earlier than conventional AST. The cost is estimated for less than 6 USD for 16 antibiotics, chosen by the microbiologist. [ABSTRACT FROM AUTHOR]