Diagnostic performance of the time to positivity of blood cultures to distinguish true bacteremia from contaminants based on an automated system. / Utilidad diagnóstica de los tiempos de positividad de hemocultivos para distinguir verdaderas bacteriemias de contaminantes en base a un sistema automatizado.

OBJECTIVE.: To determine the diagnostic performance of blood culture positivity times for distinguishing true bacteremia from contaminants in the automated "BACT/ALERT®" system. MATERIALS AND METHODS.: A cross-sectional, diagnostic test-type study was conducted from a database of blood culture samples processed between January 2016 and August 2021. All blood culture samples from patients with suspected bacteremia were included; blood culture samples were entered into the "BACT/ALERT®" system to differentiate true bacteremia from contaminants. RESULTS.: We obtained 33,951 blood cultures samples, of which 3875 were positive. Of the total number of positive blood cultures, 75.2% (n=2913) were true bacteremia and 24.8% (n=962) were contaminants. The median time to positivity in blood cultures with true bacteremia was significantly shorter (16.3 hours; IQR: 11.2 - 24.9) than the median time to positivity of blood cultures with contaminants (22.5 hours; IQR: 18.4 - 31.8; p<0.001). The positivity time showed the capacity to differentiate true bacteremia from contaminants, with an AUC-ROC of 0.73 (95%CI: 0.71 - 0.75), with 85% and 63% sensitivity and specificity respectively for the diagnosis of contaminants when the positivity time exceeds 16.5 hours. The use of antibiotics prior to sampling delayed the time to positivity, while having fever before sampling shortened the time to positivity. CONCLUSIONS.: Our results show good diagnostic performance of blood culture positivity times to differentiate true bacteremia from contaminants using the "BACT/ALERT®" system when the positivity time was longer than 16.5 hours.

OBJETIVO.: Determinar la utilidad diagnóstica de los tiempos de positividad de hemocultivos para distinguir verdaderas bacteriemias de contaminantes en el sistema automatizado «BACT/ALERT®¼. MATERIALES Y MÉTODOS.: Se realizó un estudio transversal de tipo pruebas diagnósticas, a partir de una base de datos de muestras de hemocultivos procesadas entre enero del 2016 y agosto del 2021. Se incluyeron todas las muestras de hemocultivos de pacientes con sospecha de bacteriemia, las muestras de hemocultivos fueron ingresadas al sistema «BACT/ALERT®¼ para diferenciar verdaderas bacteriemias de contaminantes. RESULTADOS.: Se analizó un total de 33 951 frascos de hemocultivos y se obtuvieron 3875 frascos positivos. El 75,2% (n=2913) del total de hemocultivos positivos fueron verdaderas bacteriemias y 24,8% (n=962) fueron contaminantes. La mediana de tiempo de positividad en los hemocultivos con verdaderas bacteriemias fue significativamente menor (16,3 horas; RIC: 11,2 - 24,9) que la mediana de tiempo de positividad de hemocultivos con contaminantes (22,5 horas; RIC: 18,4 - 31,8; p<0,001). El tiempo de positividad demostró capacidad discriminante para diferenciar verdaderas bacteriemias de contaminantes, con un AUC-ROC de 0,73 (IC95%: 0,71 - 0,75), con 85% y 63% de sensibilidad y especificidad respectivamente para el diagnóstico de contaminantes cuando el tiempo de positividad supera las 16,5 horas. La administración de antibióticos previos a la toma retrasó el tiempo de positividad, en cambio, haber presentado fiebre antes de la toma de muestra acortó el tiempo de positividad. CONCLUSIONES.: Nuestros resultados muestran un buen desempeño de los tiempos de positividad de hemocultivos para diferenciar verdaderas bacteriemias de contaminantes utilizando el sistema «BACT/ALERT®¼ cuando el tiempo de positividad fue superior a 16,5 horas.

Evaluation of the Humoral Immune Response of a Heterologous Vaccination between BBIBP-CorV and BNT162b2 with a Temporal Separation of 7 Months, in Peruvian Healthcare Workers with and without a History of SARS-CoV-2 Infection.

Information on the effects of a heterologous booster in adult patients first vaccinated with the BBIBP-CorV vaccine is limited. This prospective cohort study evaluated the humoral response of 152 healthcare workers (HCWs) from a private laboratory in Lima (Peru) before and after receiving the BNT162b2 vaccine, with a seven-month interval since the BBIBP-CorV doses. We employed the Elecsys® anti-SARS-CoV-2 S and the cPass™ SARS-CoV-2 Neutralization Antibody (NAbs) assays to evaluate anti-S-RBD IgG and NAbs, respectively. Of the 152 HCWs, 79 (51.98%) were previously infected (PI) with SARS-CoV-2 and 73 (48.02%) were not previously infected (NPI). The proportion of HCWs with positive NAbs, seven months after the BBIBP-CorV immunization, was 49.31% in NPI and 92.40% in PI. After the booster, this ratio increased to 100% in both groups. The anti-S-RBD IgG and NAbs in the HCWs' NPI increased by 32.7 and 3.95 times more, respectively. In HCWs' PI, this increment was 5 and 1.42 times more, respectively. There was no statistical association between the history of previous SARS-CoV-2 infection and the titer of anti-S-RBD IgG and NAbs after the booster. The humoral immunity presented a robust increase after receiving the BNT162b2 booster and was more pronounced in NPI.