Clinical Study On Formation And Prevention Of Bacterial Biofilm On Endotracheal Tubes In Ventilated Children

PARTⅠTHE FORMATION AND ANALYSIS OF PATHOGENS OF BACTERIAL BIOFILM ON ENDOTRACHEAL TUBES IN VENTILATED CHILDRENObjective To observe the distribution of bacteria and morphologic features of biofilms(BFs) on the surface of endotracheal tubes (ETT) in PICU.Methods 35 children undergoing mechanical ventilation (MV) were involved in this study. ETTs were collected at the first time of extubation. After staining with PI and FITC-ConA, the distribution of the bacteria and extracellular polymeric substances (EPS) was observed by confocal laser scanning microscopy (CLSM). Meanwhile, bacteria in BF and the secretions of lower respiratory tract were isolated, cultured and identified, respectively.Results (1) Of 35 ETTs,31 tubes were detected bacteria (88.57%). And 17 samples had the same pathogen both in the ETTs and secretions of lower respiratory tract,which accounted for 54.83% of the positive cultures from ETTs. Staphylococcus aureu, Klebsiella pneumoniae, Escherichia coli and Enterobacter cloacae were the main pathogens in BF and the secretions of lower respiratory tract.(2) Observation by CLSM showed that the bacteria were adhered on the surface of the ETTs in 12 hours after intubation; After 48 hours, lots of Spherical or clubbed bacteria adhered into clusters, EPS also increased, the initial BF was formed; After 72 hours, bacteria which encased in mass of EPS aggregated mutually into clumps, and formed mature BF; more than 7 days bacteria adhered into lamellars, and there were some microcolonies around mature BF.(3) Of 35 mechanical ventilated children,19 cases had VAP, including 10 in orotracheal intubation(62.5%) and 9 in nasotracheal intubation(100%).Conclusion Bacterial biofilm can form on the surface of ETTs when ventilated. There may be correlation between microbial colonization and BF formation on the surface of ETTs and VAP in children who were intubated and ventilated for a long period. PART IIEFFECT OF MECHANICAL CLEANING METHOD WITH STERILE URETHRAL CATHETER ON THE FORMATION OF BIOFILM OF ENDOTRACHEAL TUBESObjective To investigate the intervention of mechanical cleaning method with sterile urethral catheter on the formation of biofilm of endotracheal tubes.Methods With a prospective, randomized controlled trial,90 children expected to need more than 6 h of intubation were randomized to urethral catheter cleaning group for 3 times a day(A group),for 2 times a day (B group) and control group(C group). Plate colony count was used to calculate the bacterial colonies of ETT-BF. After staining with PI and FITC-ConA, the structural changes of ETT-BF as well as the biofilm thickness were observed by CLSM. The bacteria of ETT-BF and secretions of lower respiratory tract,the length of ICU stay,duration of mechanical ventilation and incidence of VAP among the three groups were compared.Results (1)Viable bacteria counts:①In the group of extracorporeal circulation, the quantities of viable bacteria adhered on the ETT in A group was sharply lower compared with C group (P<0.05) and after 3 days of intubation, the differences between B and C group were also significant (P<0.05).②In the group of pneumonia, the quantities of viable bacteria adhered on the ETT in A and B group was sharply lower compared with C group (P<0.05).(2) Rate of culture positive:①In A and B group of two diseases, the rate of culture positive of secretions of lower respiratory tract was sharply reduced (P<0.05), and the main pathogens in the secretions of lower respiratory tract were normal flora bacteria.②In A and B group of two diseases, the rate of culture positive of ETT was reduced, but the difference among A, B and C group were not significantly (P>0.05).(3) Observation by CLSM showed that the red bacteria were encased in mass of EPS which had green fluorescence and formed mature BF in C group; In A and B group, no biofilm or mature biofilm was seen. In the C group of extracorporeal circulation, the thickness of BF of 1d,3d,7d were 26.73±3.52μm,37.43±4.86μm,43.51±2.30μm, respectively. The thickness of BF was increased with time of MV, and the difference was significant (P<0.05). The thickness of BF in A and B group were significantly thinner than that of C group (P<0.05), A group was more obvious. The thickness of BF in pneumonia group was showed the same tendency as that in extracorporeal circulation group.(4) Difference of the incidence of VAP among A, B and C group was statistically significant. There were a decreasing trend in the length of ICU stay and duration of mechanical ventilation in A and B group though the difference was not significant.Conclusion The mechanical cleaning method with sterile urethral catheter 3 times a day could be more effective for preventing formation of ETT-BF and reducing the incidence of VAP and be safely used in clinical nursing.