Bacterial flora of biofilm in the endotracheal tube of mechanically ventilated neonates and its relationship with ventilator-associated pneumonia / 中华传染病杂志

ABSTRACT

Objective:To explore the relationship between endotracheal tube-bacterial biofilm (ETT-BF) in mechanically ventilated neonates and ventilator-associated pneumonia (VAP).Methods:A total of 30 mechanically ventilated neonates whose mechanical ventilation time were ≥48 h in the Department of Neonatology in The Second Affiliated Hospital of Wenzhou Medical University from January 2019 to January 2020 were included.According to the indwelling time of endotracheal tube, all cases were divided into three groups including group A(two to six days), group B(seven to 14 days) and group C (over 14 days). The morphological results of ETT-BF were scanned by scanning electron microscope (SEM). The incidence of VAP, the positive rates of strains isolated from endotracheal tube surface and lower respiratory tract secretion, the detection of strains and drug resistance were analyzed. Chi-squared test were used for statistical analysis.Results:The results of SEM showed that sheet matrix could be observed on the surface of the inner cavity of endotracheal tube in three days of tracheal catheter retention, and cocci adhered to it in four days. With prolonged indwelling time of endotracheal tube, the structure of bacterial biofilm (BF) had improved.The positive rate of strains isolated from the secretion of lower respiratory tract in 30 neonates was 23.3%(7/30) and all of them were Gram-negative bacteria. There was no patient developed VAP in group A, while there were two patients with VAP in group B, and five patients with VAP in group C. The incidences of VAP in the three groups were statistically significant ( χ2=10.82, P=0.004). There was no significant difference in the positive rate of strains isolated from the surface of endotracheal tube under different indwelling time in 30 cases ( χ2=1.03, P=0.598). Among of 13 neonates in group A, there were seven strains isolated from ETT-BF, mainly Gram-positive bacteria which turned out to be mainly Gram-negative bacteria with the prolongation of endotracheal tube indwelling time. Of the seven VAP cases, strains isolated from the lower respiratory tract secretion were consistent with the strains isolated from the surface of the corresponding endotracheal tube in five cases, which were Serratia liquefaciens, Klebsiella acidogenes, Serratia marcescens, Flavobacterium meningosepticum and Stenotrophomonas maltophilia, and the drug resistance was consistent. Conclusions:The colonization bacteria of early ETT-BF may come from the upper respiratory tract, with less migration which rarely causes VAP. With the prolongation of endotracheal tube indwelling time, the incidence of VAP in neonates increases. The same pathogen can be found in the ETT-BF and lower respiratory tract secretion. The source of pathogen needs further study.