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AbstractBackgroundLiquid chromatography-tandem mass spectrometry (LC-MS/MS) offers advantages over immunoassay due to its increased specificity and ability to multiplex metabolites within a single run. Wide scale adoption of LC-MS/MS in routine clinical laboratories is restricted in part due to the high level of technical expertise required. The Thermo Scientific™ Cascadion™ SM Clinical Analyzer is the first fully automated, random access clinical analyser that utilises LC-MS/MS technology. We report an analytical validation of the 25-hydroxy vitamin D2 and D3 assays on the Cascadion Analyzer and an assessment of its performance within a routine clinical laboratory.MethodsAnalyser usability was assessed by staff with no previous experience of LC-MS/MS. An analytical validation included analysis of 154 patient samples on two different Cascadion Analyzers and a four-way method comparison of 146 patient samples on Roche and Siemens immunoassays and an in-house LC-MS/MS method. Accuracy was assessed using external quality assurance and reference materials. Seven third party IQC materials were tested on Cascadion.ResultsCascadion proved easy to use by scientific and non-scientific staff. The assay passed all validation criteria. Excellent agreement was demonstrated between two different Cascadions (y = 0.97x + 3.9 nmol/L, r2 > 0.99). A method comparison demonstrated no significant difference (p > 0.05) between the Cascadion and the Roche immunoassay. A significant difference (p < 0.0001) was observed between the Cascadion and an LC-MS/MS and Siemens methods. Results obtained from EQA and reference material showed a mean bias of +3.09% and all samples were within ±10% of assigned concentrations. All third party IQC samples tested were compatible for use with Cascadion.ConclusionsThe Cascadion Analyzer is a fully automated LC-MS/MS system that requires no prior LC-MS/MS expertise. The vitamin D assays demonstrated excellent performance with high levels of accuracy.

A prominent feature of severe streptococcal infections is the profound inflammatory response that contributes to systemic toxicity. In sepsis the dysregulated host response involves both immunological and nonimmunological pathways. Here, we report a fatal case of an immunocompetent healthy female presenting with toxic shock and purpura fulminans caused by group B streptococcus (GBS; serotype III, CC19). The strain (LUMC16) was pigmented and hyperhemolytic. Stimulation of human primary cells with hyperhemolytic LUMC16 and STSS/NF-HH strains and pigment toxin resulted in a release of proinflammatory mediators, including tumor necrosis factor, interleukin (IL)-1β, and IL-6. In addition, LUMC16 induced blood clotting and showed factor XII activity on its surface, which was linked to the presence of the pigment. The expression of pigment was not linked to a mutation within the CovR/S region. In conclusion, our study shows that the hemolytic lipid toxin contributes to the ability of GBS to cause systemic hyperinflammation and interferes with the coagulation system.

These in vitro investigations show activity of 12.5 mg/L gentamicin, alone or as an adjunct to penicillin, against four strains of biofilm GBS. This concentration cannot be achieved in bone with systemic administration, but can be reached if administered locally. The combination of systemic penicillin plus local gentamicin indicates a potential application in orthopaedic-device-associated GBS infections. Studies with a larger number of strains are required to confirm our results.

Group B Streptococcus (GBS) is increasingly causing invasive infections in non-pregnant adults. Elderly patients and those with comorbidities are at increased risk. On the basis of previous studies focusing on neonatal infections, penicillin plus gentamicin is recommended for infective endocarditis (IE) and periprosthetic joint infections (PJI) in adults. The purpose of this study was to investigate whether a synergism with penicillin and gentamicin is present in GBS isolates that caused IE and PJI. We used 5 GBS isolates, two clinical strains and three control strains, including one displaying high-level gentamicin resistance (HLGR). The results from the checkerboard and time-kill assays (TKAs) were compared. For TKAs, antibiotic concentrations for penicillin were 0.048 and 0.2 mg/L, and for gentamicin 4 mg/L or 12.5 mg/L. In the checkerboard assay, the median fractional inhibitory concentration indices (FICIs) of all isolates indicated indifference. TKAs for all isolates failed to demonstrate synergism with penicillin 0.048 or 0.2 mg/L, irrespective of gentamicin concentrations used. Rapid killing was seen with penicillin 0.048 mg/L plus either 4 mg/L or 12.5 mg/L gentamicin, from 2 h up to 8 h hours after antibiotic exposure. TKAs with penicillin 0.2 mg/L decreased the starting inoculum below the limit of quantification within 4–6 h, irrespective of the addition of gentamicin. Fast killing was seen with penicillin 0.2 mg/L plus 12.5 mg/L gentamicin within the first 2 h. Our in vitro results indicate that the addition of gentamicin to penicillin contributes to faster killing at low penicillin concentrations, but only within the first few hours. Twenty-four hours after antibiotic exposure, PEN alone was bactericidal and synergism was not seen.