Anti SARS-CoV-2 antibodies monitoring in a group of residents in a long term care facility during COVID-19 pandemic peak.

Objectives Clinical laboratories plays a key role in screening, diagnosis and containment of the Coronavirus 2019 infection epidemic. The etiological diagnosis presupposes the isolation of virus genetic material in the patient's biological sample but laboratory diagnostics also make use of searching possibility for immunoglobulin (Ig)G, IgM classes antibodies. The characteristics of the antibody response are not yet completely clear. Methods This study describes a serological monitoring of subjects, elderly nursing care residence guests, interested by a very large infection outbreak. After first nasopharyngeal swab, all the positive subjects (43) were monitored for the persistence of the virus infection through nasopharyngeal swab after 20 days (16-24), 32 days (28-36) and after 49 days (47-50). At the same time, during the second (day 32) and third (day 49) follow up, all the guests were investigated for IgM and IgG anti SARS-CoV-2 antibodies, by using a quantitative chemiluminescence method. Results Thirty two days after performing the first diagnostic swab, 39 of 43 patients (90%) had IgG higher than the cut off value. After 49 days the four patients with negative IgG were still negative. The comparison of the levels of IgG-Ab between the controls shows a significant decrease in concentrations (-10%). Conclusions Our study confirms that in most patients affected by COVID-19 there is a typical antibody response with IgG-Ab present in 90% of nursing care COVID-19 positive residence guests. For IgM-Ab only 23% of tested subjects were positive on the 32nd and 49th day of illness, always in parallel with the IgG-Ab positivity.

Co-infection by two linezolid-resistant coagulase-negative staphylococci with two different resistance determinants.

Linezolid resistance among Gram-positive pathogens is being reported with increasing frequency. We examined 14 linezolid-resistant coagulase-negative staphylococci (CoNS) isolated from blood cultures obtained from patients admitted to the Intensive Care Unit of Vicenza General Hospital, Italy. The species identification yielded 10 Staphylococcus epidermidis, 3 Staphylococcus hominis, and 1 Staphylococcus capitis. Minimal inhibitory concentrations of linezolid ranged between 16 and 32 mg/l. By sequencing domain V of the 23S rRNA gene, 4 isolates were found to harbour a G2576T mutation and 10 isolates a G2447T mutation. None of the strains under study presented either the cfr gene or cardinal mutations in the L3, L4, or L22 riboproteins. In this clinical collection of linezolid-resistant CoNS the G2447T mutation was dominantly associated with S. epidermidis, while the G2576T mutation was found in other CoNS species. Two different CoNS species endowed with either mutation were isolated from 2 patients.

Vancomycin-resistant Enterococcus faecium isolates causing hospital outbreaks in northern Italy belong to the multilocus sequence typing C1 lineage.

Multilocus sequence typing (MLST) was used to obtain insights into the genetic relationships between 14 vancomycin-resistant Enterococcus faecium (VREF) isolates from humans (hospitalized patients, 5 strains) and nonhuman sources (meat and poultry, 9 strains) in northern Italy over the period 1993-2001. The typing scheme (Homan et al., 2002, J. Clin. Microb., 40:1963-1971) based on seven housekeeping genes--adk (adenylate kinase), atpA (ATP synthase, alpha subunit), ddl (D-alanine-D-alanine ligase), gyd (glyceraldehyde-3-phosphate dehydrogenase), gdh (glucose-6-phosphate dehydrogenase), purK (phosphoribosylaminoimidazole carboxylase ATPase subunit), and pstS (phosphate ATP-binding cassette transporter)--was used. In the 14 VREF analyzed, the number of unique alleles ranged from 1 (gyd) to 8 (atpA). Isolates from hospitalized patients were defined by the unique allele purK 1. Nine sequence types (STs) were identified. All of the epidemic strains isolated over the period 2000-2001 showed identical or closely related pulsed-field gel electrophoresis (PFGE) patterns and clustered in the same ST78. These strains shared six of the seven alleles with the strain CA20 representative of the 1993-1999 outbreaks, which PFGE indicated as being unrelated to those of the recent outbreaks. MLST confirmed the unrelatedness of human and nonhuman strains already detected by PFGE. All isolates clustered in three main genetic lineages: group A comprised two of the three isolates from meat; group C the human strains of all outbreaks and one poultry strain; and group B four of the five poultry strains and one meat strain. All human strains carried the esp gene and clustered in the C1 sublineage that has been described as having emerged recently worldwide.