ABSTRACT
In the current COVID-19 crisis, many national healthcare systems are confronted with a huge demand for mass testing and an acute shortage of diagnostic resources. Considering group testing as a viable solution, this pilot study was carried out to find the maximum number of samples that can be pooled together to accurately detect one positive sample carrying the severe acute respiratory syndrome-coronavirus 2 viral RNA from different pools. We made different pool sizes ranging from 5 to 30 samples. Three positive samples, covering the common range of polymerase chain reaction (PCR) threshold cycle values (an indirect indicator of viral load) observed in our patients, were selected, and different pools were made with known negative samples. The pools underwent real-time qualitative PCR for the determination of effective maximum pool size. It was observed that up to 20-sample pools of all positive samples could accurately be detected in terms of both E gene and RdRp gene, leading to considerable conservation of resources, time and workforce. However, while deciding the optimal pool size, the infection level in that particular geographical area and sensitivity of the test assay used (limit of detection) have to be taken into account.
Subject(s)
Betacoronavirus/genetics , Coronavirus Infections/diagnosis , Mass Screening/methods , Pneumonia, Viral/diagnosis , Real-Time Polymerase Chain Reaction/methods , Viral Load/methods , Betacoronavirus/isolation & purification , COVID-19 , Clinical Laboratory Techniques/methods , Coronavirus Envelope Proteins , Coronavirus RNA-Dependent RNA Polymerase , Diagnostic Tests, Routine/methods , Humans , India , Pandemics , RNA, Viral/genetics , RNA-Dependent RNA Polymerase/genetics , SARS-CoV-2 , Specimen Handling , Viral Envelope Proteins/genetics , Viral Nonstructural Proteins/geneticsABSTRACT
BACKGROUND: Infectious Keratitis (Ik) Is A Potential Vision-Threatening Ocular Infection Caused By A Variety Of Microorganisms. AIM: To Explore Risk Factors And Etiological Agents Associated With Ik. DESIGN: A Prospective Cross-Sectional Study In Which Corneal Scrapings From 120 Suspected Cases Were Evaluated At A Tertiary Health Care Institute From January To December 2019. METHODS: Scrapings Were Subjected To Direct Microscopy, Culture, And Identification By Both Conventional Methods And Maldi-Tof-Ms. The Patient's Demographic Data And Predisposing Factors, If Any Were Recorded. RESULTS: The Mean Age Of Patients Was 48.9 Years And Predisposing Factors Were Documented In 46% (55/120) Of Cases. Overall, Infective Etiology Could Be Established In 51% (N = 61/120) Of Cases. Fungal Growth In 26% (N = 31/120) Of Cases And Bacterial Growth In 22% (N = 27/120) Of Cases Was Obtained. Growth Of More Than One Species Of Fungi Or Growth Of Bacteria Along With Fungus Were Observed In 2% (N = 3/120) Of Cases. Of All The Fungal Isolates Obtained (N = 34), The Most Common Isolate Was Fusarium (18/34) Followed By Aspergillus (8/34), Curvularia (4/34), Pseudallescheria Boydii (3/34), And Geotrichum (1/34). Among The Gram-Positive Bacterial Isolates (N = 16), Staphyloccus Species (15/16) Were Isolated In Maximum Number Followed By Streptococcus Pneumoniae (1/16). Among The Gram-Negative Isolates (N = 13), Pseudomonas Species (8/13) Were Isolated In Maximum Number Of Cases, Followed By Acinetobacter (3/13), Klebsiella Pneumoniae (1/13), And Escherichia Coli (1/13). CONCLUSION: For Initiating Appropriate Empirical Therapy, The Knowledge Of The Epidemiological Pattern Of Infectious Keratitis Of A Particular Geographical Region Is Crucial.
