Abstracts Respiratorio 2017

Less Neutrophil Extracellular Trap Formation in Term Newborns than in Adults.

Lipp, P.; Neonatology Vol. 111 Nr. 2 Página: 182 - 188 Fecha de publicación: 01/02/2017

BACKGROUND: Newborns are prone to infections, which are independent predictors of neonatal mortality and morbidity. Neutrophil extracellular traps (NETs) are structures composed of chromatin and antimicrobial molecules that capture and kill pathogens. NETs may play an important role in the innate immune system and, thus, might be associated with impaired neonatal immune function. OBJECTIVES: This study aimed to compare NET formation between term neonates and healthy adults. We additionally investigated the effects of gestational age, birth weight, mode of delivery, gender, and perinatal infections. METHODS: We collected cord blood from 57 term infants (mean gestational age, 39.1 weeks) and 9 late preterm infants (35 weeks), and peripheral blood from 18 healthy adult donors. Neutrophils were isolated, and then NET formation was induced using three different stimulants: N-formylmethionine-leucyl-phenylalanine, phorbol 12-myristate 13-acetate (PMA), or lipopolysaccharide. NETs were immunohistochemically stained and analyzed with regard to NET percentage and NET area. RESULTS: With all three stimuli, healthy term infants showed a lower NET percentage than the adult control group (p < 0.0001 each). The groups also differed in NET area, but the significance level was lower. Following PMA stimulation, we observed greater reductions in NET percentage and NET area in preterm than term infants. CONCLUSIONS: The lower NET formation observed in term infants compared to adults likely contributes to the reduced neonatal immune response. NET formation appeared to be even further decreased in late preterm neonates. There remains a need for further investigations of NET formation in more immature preterm infants.

Rapid Identification of Bacterial Antibiotic Resistance by qPCR in Infants with Gram-Negative Septicaemia: A Proof-of-Concept Study.

BACKGROUND: Neonatal sepsis remains an important cause of neonatal morbidity and mortality. Tools to rapidly predict antibiotic resistance in neonatal sepsis would be extremely valuable.

OBJECTIVES: To develop quantitative polymerase chain reaction (qPCR) primer/probe sets that can rapidly detect antibiotic resistance genes common to a neonatal unit, and to investigate the feasibility of direct detection of antibiotic resistance genes in whole blood of infants with Gram-negative septicaemia without first isolating the organism.

METHODS: Primer/probe sets were designed to detect genes that produce aminoglycoside-modifying enzymes or extended-spectrum ß-lactamase. In phase 1, Gram-negative organisms isolated from neonatal clinical specimens within a 12-month period were analysed by qPCR to detect preselected genes. In phase 2, blood specimens of infants with Gram-negative septicaemia were subjected to qPCR analysis to detect antibiotic resistance genes for comparison against conventional antibiotic resistance profile results.

RESULTS: Two primer/probe sets showed promising diagnostic utilities for the prediction of antibiotic resistance; the diagnostic utilities (sensitivity, specificity, positive predictive value and negative predictive value) were 90.9, 96.4, 92.6 and 95.5%, respectively, for AAC3-2 [aac(3')-IIa/aacC3/aacC2, aac(3')-IIc/aacC2] to detect gentamicin resistance, and 59.3, 99.3, 94.1 and 92.6%, respectively, for BLA-C1 (blaCTX-M-9, blaCTX-M-14, blaCTX-M-24, blaCTX-M-27) to detect cephalosporin resistance. Twenty-six infants were tested in phase 2, and both gentamicin and cephalosporin resistance patterns were predicted with 100% sensitivity and 100% specificity by AAC3-2 and BLA-C1, respectively.

CONCLUSIONS: qPCR with appropriately designed primer/probe sets can predict antibiotic resistance directly from neonatal blood, and it can substantially reduce the turnaround time for antibiotic resistance results.