ABSTRACT
Objective To explore the effect and its possible mechanism of human umbilical cord mesenchymal stem cells (hUCMSCs) on bacterial growth in bronchoalveolar lavage fluid (BALF) of newborns with ventilator associated pneumonia (VAP).Methods Newborns admitted to neonatal intensive care unit (NICU) in Guangdong Women and Children Hospital Affiliated to Guangzhou Medical University from June 1,2012 to December 31,2012 were reviewed.The inclusion criteria were:(1)Positive BALF culture results.(2) Requirement of mechanical ventilation with tracheal intubation.(3) Diagnosed as ventilator-associated pneumonia.Two pieces of BALF samples of newborn were collected and randornaly divided into experimental and control group.hUCMSCs were added into the experimental group,while the same volume of conditioned medium was added into the control group.Both groups were incubated for six hours in humidified CO2 incubator at 37 ℃,then,bacterial growth was assessed by colony forming unit (CFU) counts.Levels of the antimicrobial peptides (Cathelicidin/LL-37 and human HBD-2) were determined by enzyme-linked immunosorbent assay and Western blot.Paired t-test was used for statistical analysis.Results Among the culture results of 31 newborns,there were Klebsiella pneumoniae (6 cases,19.3％),Stenotrophomonas narrow food aeromonas (6 cases,19.3％),Hemolytic staphylococci (5 cases,16.1％),Escherichia coli (3 cases,9.7％),Bacterial meningitis septicemia Elizabeth Platinum (3 cases,9.7％),Acinetobacter baumannii (3 cases,9.7％),Pseudomonas putida (2 cases,6.4％),Pseudomonas aeruginosa (1 case,3.2％),Staphylococcus aureus (1 case,3.2％) and Enterobacter cloacae (1 ease,3.2％).The CFU counts in experimental group were much less than those in control group [(2.60±0.67) ×104] CFU/ml vs [(1.18±0.32) ×105] CFU/ml,(t=-20.19,P＜0.01).Levels of Cathelicidin/LL-37 and HBD-2 in experimental group were higher than those in control group [Cathelicidin/LL-37:(8.98 ± 3.22) ng/ml vs (3.18 ± 1.57) ng/ml,t =17.79,P ＜ 0.01 ;HBD-2:(379.87±11.74) pg/ml vs (39.89±2.86) pg/ml,t=37.62,P＜0.01].Conclusions hUCMSCs had antimicrobial effect on bacterial growth in BALFs from ventilator associated pneumonia possibly by the secretion of antimicrobial peptides (Cathelicidin/LL-37 and HBD-2).