ABSTRACT
A proof-of-concept aptamer-based optical assay is described for the determination of the immuno signalling molecule interleukin-6 (IL-6), a key marker of acute inflammation. The optical assay is based on the aggregation of gold nanoparticles (AuNP) coated in two complimentary "sandwich-style" aptamers, each with different IL-6 target moieties. IL-6 will recognise the complimentary aptamer pair and bind to it, thereby causing the aggregation of the corresponding functionalised nanoparticles. The aggregation of the AuNPs after exposure to IL-6 induces a visible colour change from red to pink, with a corresponding change in the absorption maximum from 520 to 540 nm. The change in the absorption maximum can be monitored visually, or by using a spectrophotometer or a plate reader. The optimal size and functionalisation of aptamer-coated AuNPs, and the potential assay formats were investigated using UV-vis spectrophotometry, transmission electron microscopy, and dynamic light scattering. The optical assay was applied for detecting mouse IL-6 in a mixed protein solution as a representative biological sample. The assay works in the 3.3 to 125 µg·mL-1 IL-6 concentration range, and the detection limit (at S/N = 3) is 1.95 µg·mL-1. This study was performed as a proof-of-concept demonstration of this versatile assay design, with a view to developing a similar assay for use in clinical samples in future. Graphical abstractSchematic representation of the aggregation of aptamer-functionalised nanoparticles in the presence of interleukin-6 (IL-6). The presence of mouse IL-6 in a mixed protein solution leads to a visible colour change, and a change in the absorption spectrum of the nanoparticles.
Subject(s)
Aptamers, Nucleotide/chemistry , Biosensing Techniques/methods , Gold/chemistry , Interleukin-6/analysis , Metal Nanoparticles/chemistry , Aptamers, Nucleotide/metabolism , Inflammation/diagnosis , Interleukin-6/metabolism , KineticsABSTRACT
In early 2017, a United Kingdom (UK)-born person in their 20s presented with a skin ulcer on the foot 3 weeks after returning from Ghana. The patient had last received a diphtheria-containing vaccine in 2013, completing the recommended course. MALDI-TOF of a cutaneous swab identified Corynebacterium diphtheriae. Real-time PCR ascertained the species and presence of the diphtheria toxin gene. An Elek test confirmed toxigenicity. The isolate was macrolide sensitive and penicillin resistant. The local Public Health England (PHE) Health Protection Team obtained the patient's clinical history and traced contacts to inform appropriate public health action. One close contact (in their early 80s with uncertain immunisation status who had not recently travelled) had a positive throat swab for toxigenic C. diphtheriae and reported a history of mild coryzal symptoms. Multilocus sequence typing revealed that strains from the index case and contact had Sequence Type 463. Diphtheria is extremely rare in the UK due to high vaccine coverage and this is the first documented transmission in 30 years. Clinicians and laboratory staff should remain highly suspicious of lesions in overseas travellers, even when patients are fully vaccinated. Older individuals who might not have completed a full immunisation course may have higher diphtheria susceptibility.
Subject(s)
Contact Tracing , Corynebacterium Infections/transmission , Corynebacterium diphtheriae/genetics , Corynebacterium diphtheriae/isolation & purification , Diphtheria/diagnosis , Travel , Corynebacterium Infections/diagnosis , Disease Notification , Ghana , Humans , Multilocus Sequence Typing , Real-Time Polymerase Chain Reaction , United KingdomABSTRACT
Introduction. Pneumonia is highly prevalent in intensive care units (ICUs), with high associated mortality. Empirical treatment prioritizes breadth of coverage while awaiting laboratory diagnosis, often at the expense of antimicrobial stewardship. Microarrays use multiple parallel polymerase chain reactions to enable a rapid syndromic approach to laboratory diagnosis.Aim. To evaluate the clinical and laboratory implications of introducing a bespoke 22-pathogen TaqMan Array Card (TAC) for rapid pathogen detection in deep respiratory samples from adult ICUs.Methodology. TAC results from all ICU patients prospectively tested over a 9-month period at Cambridge's Clinical Microbiology and Public Health Laboratory were compared to those of corresponding conventional microbiological assays (culture-, PCR- or serology-based) in terms of result agreement and time-to-result availability. Clinical impact was assessed by retrospective review of medical records.Results. Seventy-one patients were included [45 (63â%) male, median age 59). Overall result agreement was 94â%, with TAC detecting more pathogens than conventional methods. TAC detected Streptococcus pneumoniae more readily than culture (7 vs 0 cases; P=0.02). TAC did not detect Aspergillus spp. in eight culture- or galactomannan-positive cases. The median turnaround time (1 day) was significantly shorter than that of bacterial/fungal culture, Pneumocystis jirovecii PCR and galactomannan testing (each 3 days; P<0.001), atypical bacteria serology (13 days; P<0.001) and Mycobacterium tuberculosis culture (46 days; P<0.001). Earlier result availability prompted discontinuation of unnecessary antimicrobials in 15/71 (21â%) cases, but had no bearing on patient isolation/deisolation.Conclusion. TAC provided greater overall yield of pathogen detection and faster turnaround times, permitting earlier discontinuation of unnecessary antimicrobials.
Subject(s)
Molecular Diagnostic Techniques/methods , Pneumonia/diagnosis , Respiratory Tract Infections/diagnosis , Adult , Bacteria/isolation & purification , Critical Care/methods , Female , Fungi/isolation & purification , Humans , Intensive Care Units , Male , Middle Aged , Polymerase Chain Reaction/methods , Retrospective Studies , Sensitivity and Specificity , United KingdomABSTRACT
Anaerobic ventriculitis is rare, and usually seen in patients with predisposing factors such as otitis media, mastoiditis, sinusitis or recent neurosurgery. We report what we believe to be the first case of ventriculitis and brain abscess due to Fusobacterium nucleatum infection in a man with no significant predisposing factors. He was successfully treated with antibiotic therapy.
Subject(s)
Brain Abscess/microbiology , Cerebral Ventricles/microbiology , Encephalitis/microbiology , Fusobacterium Infections/microbiology , Fusobacterium nucleatum/isolation & purification , Anti-Bacterial Agents/therapeutic use , Brain Abscess/diagnosis , Brain Abscess/drug therapy , Brain Abscess/pathology , Cerebral Ventricles/pathology , Encephalitis/drug therapy , Encephalitis/pathology , Fusobacterium Infections/diagnosis , Fusobacterium Infections/drug therapy , Fusobacterium Infections/pathology , Humans , Male , Middle AgedABSTRACT
We questioned 62 dermatology outpatients with atopic eczema and Staphylococcus aureus colonisation regarding their use of topical preparations containing fusidic acid during the previous 6 months as well as the pattern of any such use. Recent exposure to topical fusidic acid was significantly correlated with the presence of fusidic acid-resistant S. aureus (FRSA) (P=0.04). There was also a significant trend towards increasing FRSA carriage with increased duration of use. Short courses of 2 weeks or less did not appear to change the FRSA profile compared with non-exposure, and intermittent usage appeared to be the most detrimental, although subgroup sizes were small. Our study cautions against prolonged or intermittent use of fusidic acid-containing products in patients with eczema.