Urinary antigen tests (UATs) are often used to diagnose Legionnaires’ disease as they are rapid and easy to perform on readily obtainable urine samples without the need for specialized skills compared to conventional methods. Recently developed automated readers for UATs may provide objective results interpretation, especially in cases of weak result bands. Using 53 defined patient urine samples, we evaluated the performance of the BinaxNOW Legionella Antigen Card (Abbott), ImmuView S. pneumoniae and Legionella (SSI Diagnostica), STANDARD F Legionella Ag FIA (SD Biosensor), and Sofia Legionella FIA (Quidel) simultaneously with their respective automated readers. Automatic and visual interpretation of result bands were also compared for the immunochromatography-based BinaxNOW and ImmuView UATs. Overall sensitivity and specificity of Legionella UATs were 53.9–61.5% and 90.0–94.9%, respectively. All four UATs successfully detected all samples from L. pneumophila serogroup 1-positive patients, but most failed to detect samples for Legionella spp., or other serogroups. Automatic results interpretation of results was found to be mostly concordant with visual results reading. In conclusion, the performance of the four UATs were similar to each other in the detection of Legionella urinary antigen with no major difference between automated or visual results reading.

Streptococcus pneumoniae urinary antigen tests (UATs) may be interpreted using automatic readers to potentially automate sample incubation and provide standardized results reading. Here, we evaluated four UATs the BinaxNOW S. pneumoniae Antigen Card (Abbott, Chicago, USA), ImmuView S. pneumoniae and Legionella (SSI Diagnostica, Hillerød, Denmark), STANDARD F S. pneumoniae Ag FIA (SD Biosensor, Gyeonggi, South Korea), and Sofia S. pneumoniae FIA (Quidel Corporation, San Diego, USA) with their respective benchtop readers for their ability to detect S. pneumoniae urinary antigen. We found that these assays had a sensitivity of 76.9–86.5%, and specificity of 84.2–89.7%, with no significant difference found among the four UATs. The assays had a high level of agreement with each other, with 84.5% of samples testing consistently across all four assays. The automatically and visually read test results from the two immunochromatographic assays, BinaxNOW and ImmuView, were compared and showed excellent agreement between the two types of reading. Immunofluorescent-based assays, Sofia and STANDARD F, had significantly less time to detect compared to the two immunochromatographic assays due to having less assay setup procedures and shorter sample incubation times. In conclusion, the four UATs performed similarly in the detection of S. pneumoniae urinary antigen, and readers can bring increased flexibility to running UATs in the clinical routine.

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Blood stream infection (BSI) is related to high mortality and morbidity. Early antimicrobial therapy is crucial in treating patients with BSI. The most common Gram-negative bacteria causing BSI is Escherichia coli. Targeted effective treatment of patients with BSI is only possible if it is based on antibiotic susceptibility testing (AST) data after blood culture positivity. However, there are very few methods available for rapid phenotypic AST and the fastest method takes 4 h. Here we analyzed the performance of a 30 min ultra-rapid method for AST of E. coli directly from positive blood cultures (BC). In total, 51 positive BC with E. coli were studied, and we evaluated the ultra-rapid method directly on positive BC as well as on E. coli colonies cultured on agar plates. The results obtained by the new method were compared with disk diffusion.The method provided accurate AST result in 30 min to Ciprofloxacin and Gentamicin for 92% and 84% of the positive BC samples, respectively. For E. coli isolates retrieved from agar plates, 86% and 96% of the AST results were accurate for Ciprofloxacin and Gentamicin, respectively, after 30 min of assay time. When time to result was modulated in-silico from 30 to 60 minutes for the agar plate samples, accuracy of AST results went up to 92% for Ciprofloxacin and to 100% for Gentamicin.The present study shows that the method is reliable and delivers ultra-rapid AST data in 30 minutes directly from positive BC and as well as from agar plates.

There is an utmost need for rapid antimicrobial susceptibility testing (AST) of bacteria causing bloodstream infections (BSI). The dRAST (QuantaMatrix Inc., Seoul) is a rapid AST method that can be performed directly from positive blood cultures.