Evaluación de una técnica de PCR en tiempo real para determinar colonización por Streptococcus agalactiae en mujeres gestantes de Medellín que consultan en Dinamica IPS

Abstract

Objective: To evaluate a real-time qPCR technique to determine colonization by Streptococcus agalactiae in pregnant women from Medellín. Materials and Methods: A prospective and descriptive study was conducted in 150 pregnant women, randomly selected, at an IPS between January and July 2016. Inclusion criteria: gestation period week 35-37, voluntary declaration of participation in the study. Exclusion criteria: the use of antibiotics. Samples were taken from the vaginal introitus and the anal region using a hyssop and processed for qPCR as well as the gold standard test [selective broth culture with subsequent culture in blood agar and chromogenic medium for S. agalactiae STRB (ChromIDTMStrepto, BioMérieux SA)]. Results: The prevalence of colonization by S. agalactiae in pregnant women was 20.9% and 22.3% in blood agar and chromogenic agar STRB respectively, whereas using qPCR the prevalence was 36.0%. The time required using the culture was 24-48h compared to 6h for qPCR. Our data comparing qPCR with the gold standard test showed: sensitivity 79.31% (95% CI: 0.61-0.90), specificity 75.45% (95% CI: 0.66-0.82), positive predictive value 46.0% (95% CI: 0.32-0.59) and negative 93.2% (95% CI: 0.86-0.96). Discussion: The use of the qPCR increased the sensitivity and the diagnostic opportunity (4x to 8x faster using qPCR), which can lead to a decrease in the risk of neonatal transmission of S. agalactiae and result in a reduction in the length of hospital stay and costs induced by a preventable infection.