ABSTRACT
The detection of serum antibodies to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is emerging as a new tool for the coronavirus disease-2019 (COVID-19) diagnosis. Since many coronaviruses are sensitive to heat, heating inactivation of samples at 56 {degrees}C prior to testing is considered a possible method to reduce the risk of transmission, but the effect of heating on the measurement of SARS-CoV-2 antibodies is still unclear. By comparing the levels of SARS-CoV-2 antibodies before and after heat inactivation of serum at 56 {degrees}C for 30 minutes using a quantitative fluorescence immunochromatographic assay, we shown that heat inactivation significantly interferes with the levels of antibodies to SARS-CoV-2. The IgM levels of all the 34 serum samples (100%) from COVID-19 patients decreased by an average level of 53.56%. The IgG levels were decreased in 22 of 34 samples (64.71%) by an average level of 49.54%. Similar changes can also be observed in the non-COVID-19 diseases group (n=9). Of note, 44.12% of the detected IgM levels were dropped below the cut-off value after heating, suggesting heat inactivation can lead to false-negative results of these samples. Our results indicate that heat inactivation of serum at 56 {degrees}C for 30 minutes interferes with the immunoanalysis of antibodies to SARS-CoV-2. Heat inactivation prior to immunoanalysis is not recommended and the possibility of false-negative results should be considered if the sample was pre-inactivated by heating.
ABSTRACT
Objective To study the etiology and antibiotic resistance of bloodstream infections in low birth weight preterm infants .Methods A total of 95 cases of bloodstream infections in low birth weight preterm infants were treated in our hospital from January 2011 to April 2014 .The clinical data of these patients were analyzed retrospectively .Results A total of 96 pathogens were isolated ,including 57 strains of gram‐negative bacilli ,38 strains of gram‐positive cocci ,and 1 strains of Trichosporon asahii .The most frequently isolated pathogens were Klebsiella pneumoniae (40 strains)and coagulase‐negative Staphylococcus(31 strains).All gram‐negative bacilli were sensitive to carbapenems such as imipenem and panipenem . Streptococcus isolates were sensitive to most antibiotics .Most Staphylococcus isolates were methicillin‐resistant ,which were highly resistant to common antibiotics but all sensitive to linezolid , vancomycin and teicoplanin . Conclusions The most important pathogens responsible for bloodstream infections in low birth weight preterm infants in our hospital are K lebsiella pneumoniae and coagulase‐negative Staphylococcus . Early identification of responsible pathogen and rational antimicrobial therapy are critical for good prognosis of bloodstream infections in low birth weight preterm infants .
