Gold conjugated nanobodies in a signal-enhanced lateral flow test strip for rapid detection of SARS-CoV-2 S1 antigen in saliva samples.

Despite the transfer of COVID-19 from the pandemic to control, we are still in a state of uncertainty about long-term success. Therefore, there is a great need for rapid and sensitive diagnostics to sustain the control status. After several optimization trials, we developed lateral flow test (LFT) strips for rapid detection of SARS-CoV-2 spike 1 (S1) antigen in saliva samples. For signal enhancement of our developed strips, we applied dual gold conjugates. Gold-labeled anti-S1 nanobodies (Nbs) were employed as S1 detector conjugate, while gold-labeled angiotensin-converting enzyme 2 (ACE2) was used as S1 capturing conjugate. In a parallel strip design, we used an anti-S1 monoclonal antibody (mAb) as an antigen detector instead of anti-S1 Nbs. Saliva samples were collected from 320 symptomatic subjects (180 RT-PCR confirmed positive cases and 140 confirmed negative cases) and were tested with the developed strips. In early detection for positive samples with cycle threshold (Ct ≤ 30), Nbs-based LFT strips showed higher sensitivity (97.14%) and specificity (98.57%) than mAb-based strips which gave 90.04% sensitivity and 97.86% specificity. Moreover, the limit of detection (LoD) for virus particles was lower for Nbs-based LFT (0.4 × 104 copies/ml) than for the mAb-based test (1.6 × 104 copies/ml). Our results are in favor of the use of dual gold Nbs and ACE2 conjugates in LFT strips. These signal-enhanced strips offer a sensitive diagnostic tool for rapid screening of SARS-CoV-2 S1 antigen in the easily collected saliva samples.

Non-Invasive Detection of SARS-CoV-2 Antigen in Saliva versus Nasopharyngeal Swabs Using Nanobodies Conjugated Gold Nanoparticles.

The development of sensitive, non-invasive tests for the detection of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) antigens is imperative, and it is still challenging to manage the extent of infection throughout the population. Here, we designed and optimized a sandwich enzyme-linked immunosorbent assay (ELISA) protocol for SARS-CoV-2 S1 antigen detection in saliva. Both saliva samples and nasopharyngeal swabs were collected from 220 real-time quantitative polymerase chain reaction (RT-qPCR)-confirmed positive and negative cases. S1 protein receptor-binding domain (RBD) nanobodies were efficiently conjugated with 40 nm gold nanoparticles (AuNPs) and employed as antigen detection probes in the developed system, while recombinant S1 monoclonal antibodies (S1mAbs) were employed as antigen capture probes. After checkerboard assays and system optimization, the clinical samples were tested. In saliva, the developed ELISA system showed the highest sensitivity (93.3) for samples with cycle threshold (Ct) values ≤ 30; interestingly, high sensitivity (87.5 and 86%) was also achieved for samples with Ct values ≤ 35 and ≤40, respectively, compared with 90, 80 and 88% sensitivity rates for nasopharyngeal swabs with the same categorized Ct values. However, the specificity was 100%, and no cross-reactions were detected with Middle East respiratory syndrome coronavirus (MERS-CoV) or SARS-CoV antigens. These results reveal that our protocol could be established as an efficient and sensitive, non-invasive diagnostic tool for the early detection of SARS-CoV-2 infection using easily collectable saliva samples.

Epidemiology of Carbapenem-resistant Enterobacteriaceae in Egyptian intensive care units using National Healthcare-associated Infections Surveillance Data, 2011-2017.

Objective: To describe the epidemiology of carbapenem-resistant Enterobacteriaceae (CRE) healthcare-associated infections (HAI) in Egyptian hospitals reporting to the national HAI surveillance system. Methods: Design: Descriptive analysis of CRE HAIs and retrospective observational cohort study using national HAI surveillance data. Setting: Egyptian hospitals participating in the HAI surveillance system. The patient population included patients admitted to the intensive care unit (ICU) in participating hospitals. Enterobacteriaceae HAI cases were Klebsiella, Escherichia coli, and Enterobacter isolates from blood, urine, wound or respiratory specimen collected on or after day 3 of ICU admission. CRE HAI cases were those resistant to at least one carbapenem. For CRE HAI cases reported during 2011-2017, a hospital-level and patient-level analysis were conducted using only the first CRE isolate by pathogen and specimen type for each patient. For facility, microbiology, and clinical characteristics, frequencies and means were calculated among CRE HAI cases and compared with carbapenem-susceptible Enterobacteriaceae HAI cases through univariate and multivariate logistic regression using STATA 13. Results: There were 1598 Enterobacteriaceae HAI cases, of which 871 (54.1%) were carbapenem resistant. The multivariate regression analysis demonstrated that carbapenem resistance was associated with specimen type, pathogen, location prior to admission, and length of ICU stay. Between 2011 and 2017, there was an increase in the proportion of Enterobacteriaceae HAI cases due to CRE (p-value = 0.003) and the incidence of CRE HAIs (p-value = 0.09). Conclusions: This analysis demonstrated a high and increasing burden of CRE in Egyptian hospitals, highlighting the importance of enhancing infection prevention and control (IPC) programs and antimicrobial stewardship activities and guiding the implementation of targeted IPC measures to contain CRE in Egyptian ICU's .