Seroprevalence of infection-induced SARS-CoV-2 antibodies among health care users of Northern Italy: results from two serosurveys (October-November 2019 and September-October 2021)

OBJECTIVES: The objective was to estimate the seroprevalence of SARS-CoV-2 in autumn 2019 (before case zero was identified in Italy) and 2021 among residual sera samples from health care users in the Piedmont region of northwestern Italy. METHODS: Two serosurveys were conducted. Using a semiquantitative method, samples were tested for the presence of immunoglobulin G (IgG) antibodies against the S1 domain of the spike protein. Samples with positive test results from the 2019 survey were independently retested using a multiplex panel to detect IgG antibodies against the receptor binding domain, S1 and S2 domains, and nucleocapsid. Samples with positive test results from the 2021 survey underwent repeat testing with enzyme-linked immunosorbent assay to detect anti-nucleocapsid IgG antibodies. Prevalence rates according to gender and age groups, together with their respective 95% confidence intervals (CIs), were calculated. RESULTS: Overall, the proportion of samples with positive test results was 2/353 in 2019 and 22/363 in 2021, with an estimated seroprevalence of 0.27% (95% CI 0-1.86) and 6.21% (95% CI 3.9-9.31) in 2019 and 2021 respectively. CONCLUSION: Results of this study support the hypothesis that the virus was circulating in Italy as early as autumn 2019. The role of these early cases in broader transmission dynamics remains to be determined

High Risk of Secondary Infections Following Thrombotic Complications in Patients With COVID-19

Background. This study’s primary aim was to evaluate the impact of thrombotic complications on the development of secondary infections. The secondary aim was to compare the etiology of secondary infections in patients with and without thrombotic complications. Methods. This was a cohort study (NCT04318366) of coronavirus disease 2019 (COVID-19) patients hospitalized at IRCCS San Raffaele Hospital between February 25 and June 30, 2020. Incidence rates (IRs) were calculated by univariable Poisson regression as the number of cases per 1000 person-days of follow-up (PDFU) with 95% confidence intervals. The cumulative incidence functions of secondary infections according to thrombotic complications were compared with Gray’s method accounting for competing risk of death. A multivariable Fine-Gray model was applied to assess factors associated with risk of secondary infections. Results. Overall, 109/904 patients had 176 secondary infections (IR, 10.0; 95% CI, 8.8–11.5; per 1000-PDFU). The IRs of secondary infections among patients with or without thrombotic complications were 15.0 (95% CI, 10.7–21.0) and 9.3 (95% CI, 7.9–11.0) per 1000-PDFU, respectively (P = .017). At multivariable analysis, thrombotic complications were associated with the development of secondary infections (subdistribution hazard ratio, 1.788; 95% CI, 1.018–3.140; P = .043). The etiology of secondary infections was similar in patients with and without thrombotic complications. Conclusions. In patients with COVID-19, thrombotic complications were associated with a high risk of secondary infections

A New Culture Method for the Detection of Non-Tuberculous Mycobacteria in Water Samples from Heater–Cooler Units and Extracorporeal Membrane Oxygenation Machines

The isolation of non-tuberculous mycobacteria (NTM) from cultures is particularly laborious due to the potential overgrowth of coexisting non-acid fast bacilli. To reduce the overgrowth of these non-mycobacterial organisms, a decontamination step with NaOH or cetylpyridinium chloride is highly recommended before plating the samples on the culture medium. However, due to their toxicity, decontamination solutions tend to decrease NTM recovery from clinical and environmental samples. Here, we tested an alternative method for NTM recovery based on the use of NTM Elite agar, a selective medium that does not require a decontamination step. Using NTM Elite agar, we were able to detect non-tuberculous mycobacteria in 27.7% (30/108) of water samples analyzed. The average time to NTM detection was 18 days, but some strains required longer to grow, perhaps due to the stressful environmental conditions (periodical disinfection of devices). NTM Elite agar’s effectiveness in inhibiting background flora was proven by the isolation of NTM from samples with and without background flora, showing no statistically significant differences in detection rates for different total viable counts of background flora (p = 0.4989). In conclusion, our findings indicate that effective NTM recovery from HCU- and ECMO-derived water samples can be achieved via filtration and direct culture of the filters on NTM Elite agar. This simple procedure can speed up laboratory work and provide an improved method, successfully resulting in low contamination and high detection rate, in addition to being less time-consuming. Its sensitivity and lack of a decontamination step make this protocol particularly useful for monitoring the effectiveness of device disinfection in hospital settings, even in the presence of low NTM loads. Reading timeframes should probably be extended to 7 weeks (i.e., well beyond the standard 4 weeks advised by the manufacturer), in order to isolate even the slow-growing mycobacteria. However, an extended incubation period is not necessary for exclusion of M. chimaera contamination of the devices, as M. chimaera isolation times do not generally exceed 3 weeks

Antibody responses to BNT162b2 SARS‐CoV‐2 mRNA vaccine among healthcare workers and residents of long‐term care facilities: A cohort study in Northern Italy

Abstract Background and Aims Long‐term care facilities (LTCFs) have been severely impacted by COVID‐19, with a disproportionate amount of SARS‐CoV‐2 infections and related deaths occurring among residents. Methods This study is part of an ongoing multicenter, prospective cohort study conducted among healthcare workers (HCWs) and residents of 13 LTCFs in Northern Italy designed to evaluate SARS‐CoV‐2 specific immunoglobulin class G (IgG) titers before and following vaccination with Pfizer/BNT162b2 SARS‐CoV‐2 mRNA vaccine (two doses of vaccine, 21 days apart). Serum samples were obtained from participants (t0) before vaccination, and (t1) 2 weeks after and analyzed to determine anti‐S1 IgG antibodies. Results Five hundred and thirty‐four participants were enrolled (404 subjects participated in both blood draws). Seropositivity was 50.19% at t0 and 99% at t1, with a significant difference in IgG titers. A higher proportion of residents were seropositive at t0 compared with HCWs, with significantly higher IgG titers among residents at both t0 and t1. Pre‐existing immunity also had a significant effect on postvaccination IgG titers. However, a significant difference in titers at t1 between HCWs and residents considering only participants seropositive at t0 was found, with higher median titers among previously seropositive residents. Conclusion Findings of this study provide scientific evidence endorsing the policy of universal vaccination in LTCFs