Evaluation of the relationship between quantitative PCR results and cell culturing of SARS2-CoV with respect to symptoms onset and Viral load - a systematic review

BackgroundViral culture is currently the most accurate method to demonstrate viability and infectivity of Severe acute respiratory syndrome Coronavirus (SARS-2 CoV). Routine clinical diagnosis, however, is mostly performed by PCR - based assays that do not discriminate between infectious and non-virus. Herein, we aimed to determine the correlation between positive viral cultures and either PCR positivity, the Cycle Threshold (Ct) or the number of viral copies. MethodsA systematic electronic literature search was performed and studies that reported both viral SARS-CoV-2 culture and PCR-based assays were included. A separate search for samples from blood, urine, stool, breast milk and tears were performed. To convert Ct values reported in the reviewed studies were to viral genomic copies, calibration experiments with four different reaction performed, using quantified RNA molecules. ResultsA total 540 articles were reviewed, and 38 studies were included in this review. Out of 276 positive-culture of non-severe patients, 272 (98.55%) were negative ten days after symptoms onset, while PCR assays remained positive for up to 67 days. In severely ill or immunocompromised patients positive-culture was obtained up to 32 days and out of 168 cultures, 31 (18.45%) stayed positive after day 10. In non-severe patients, in Ct value greater than 30 only 10.8% were still culture-positive while in Ct >35 it was nearly universally negative. The minimal calculated number of viral genome copies in culture-positive sample was 2.5 x 103 copies / mL. These findings were similar in immunocompromised patients. Recovering positive culture from non-respiratory samples was sporadically obtained in stool or urine samples. Conversion of Ct values to viral genome copies showed variability between different PCR assays and highlighted the need to standardize reports to correctly compare results obtained in different laboratories. ConclusionDuring the pandemic phase, non-severe COVID-19 patients who are recovering and are not immuno-suppressed, can be regarded as non-infectious, within 10 days from symptom onset, or with Ct value greater than 35 (or a calculated viral load lower than 1.2x103 copies / mL). These findings have important implications for recovering patients and asymptomatic patients, with respect to isolation criteria. The conversion of Cq values to viral genome copies described herein may be useful in future work, enabling a more standardized comparison between results reported in different studies from different laboratories.

The role of mouthwash sampling in SARS-CoV-2 diagnosis

BackgroundThe current practice of COVID-19 diagnosis worldwide is the use of oro-nasopharyngeal (ONP) swabs. Our study aim was to explore mouthwash (MW) as an alternative diagnostic method, in light of the disadvantages of ONP swabs. MethodsCovid-19 outpatients molecular-confirmed by ONP-swab were repeatedly examined with ONP-swab and MW with normal-saline (0.9%). Other types of fluids were compared to normal-saline. The Cq values obtained with each method were compared. ResultsAmong 137 pairs of ONP-swabs and MW samples, 84.6% (116/137) of ONP-swabs were positive by at least one of the genes (N, E, R). However MW detected 70.8% (97/137) of samples as positive, which means 83.6% (97/116) out of positive ONP-swabs, missing mainly Cq value>30. In both methods, the N gene was the most sensitive one. Therefore MW samples targeting N-gene, which was positive in 95/137 (69.3%), is comparable to ONP-swabs targeting E and R genes which gave equal results - 95/137 (69.3%) and 90/137 (65.7%) respectively. Comparing saline MW to distilled-water gave equal results, while commercial mouth-rinsing solutions were less sensitive. ConclusionsMW with normal-saline, especially when tested by N gene, can effectively detect COVID-19 patients. Furthermore, this method was not inferior when compared to R and E genes of ONP-swabs, which are common targets in many laboratories around the world.

Safety of measles, rubella and mumps vaccines in adults: a prospective cohort study.

BACKGROUND: In recent years, multiple outbreaks of measles associated with vaccine hesitancy occurred in high-income countries, where measles incidence had previously been low. Most safety data about the measles, mumps and rubella (MMR) vaccine are derived from studies conducted among children, whereas evidence regarding the safety profile of the vaccine in adults is scarce. METHODS: In 2017, during an outbreak of measles in Europe, Israeli travellers to high-risk locations who were incompletely vaccinated, were urged to complete the two MMR vaccination schedule before their travel. In this prospective cohort study, we analysed adverse events (AEs) of MMR and MMRV (measles, mumps, rubella and varicella) vaccines among these travellers. All participants were followed up using structured questionnaires 2-4 weeks after vaccination. RESULTS: Seven hundred and eighty-five adult travellers whose median age was 49.2 years were vaccinated and followed up. Any AEs were reported by 25.2% of all participants; 11.6% reported local AEs, and 18.6% reported systemic AEs, none of which were severe. In general, AEs were much more common among female travellers (19.4% of males vs 30.1% of females (P < 0.001)). Local AEs, overall systemic AEs, headache and arthralgia were much more common among females, whereas rates of general malaise and fever were not statistically different between genders. We did not observe any significant differences in the rates of total, local or systemic AEs between the MMR and MMRV vaccines. Higher rates of systemic AEs were observed among participants who were younger and probably immunized once with MMR compared to older vaccines immunized once to measles only and to those who were never immunized. CONCLUSIONS: The current study demonstrated low rates of systemic AEs and no serious AEs following either MMR or MMRV administration. More AEs were reported among females, and rates of AEs were similar after either MMR or MMRV.

Favorable outcome on viral load and culture viability using Ivermectin in early treatment of non-hospitalized patients with mild COVID-19, A double-blind, randomized placebo-controlled trial.

BackgroundIvermectin, an anti-parasitic agent, also has anti-viral properties. Our aim was to assess whether ivermectin can shorten the viral shedding in patients at an early-stage of COVID-19 infection. MethodsThe double-blinded trial compared patients receiving ivermectin 0{middle dot}2 mg/kg for 3 days vs. placebo in non-hospitalized COVID-19 patients. RT-PCR from a nasopharyngeal swab was obtained at recruitment and then every two days. Primary endpoint was reduction of viral-load on the 6th day (third day after termination of treatment) as reflected by Ct level>30 (non-infectious level). The primary outcome was supported by determination of viral culture viability. ResultsEighty-nine patients were eligible (47 in ivermectin and 42 in placebo arm). Their median age was 35 years. Females accounted for 21{middle dot}6%, and 16{middle dot}8% were asymptomatic at recruitment. Median time from symptom onset was 4 days. There were no statistical differences in these parameters between the two groups. On day 6, 34 out of 47 (72%) patients in the ivermectin arm reached the endpoint, compared to 21/ 42 (50%) in the placebo arm (OR 2{middle dot}62; 95% CI: 1{middle dot}09-6{middle dot}31). In a multivariable logistic-regression model, the odds of a negative test at day 6 was 2.62 time higher in the ivermectin group (95% CI: 1{middle dot}06-6{middle dot}45). Cultures at days 2 to 6 were positive in 3/23 (13{middle dot}0%) of ivermectin samples vs. 14/29 (48{middle dot}2%) in the placebo group (p=0{middle dot}008). ConclusionsThere were significantly lower viral loads and viable cultures in the ivermectin group, which could lead to shortening isolation time in these patients. The study is registered at ClinicalTrials.gov NCT 044297411.