[Ventilator-associated pneumonia among premature infants <34 weeks' gestational age in neonatal intensive care unit in China: a multicenter study].

Objective: To investigate the incidence and pathogen distribution of ventilator-associated pneumonia (VAP) among preterm infants admitted to level Ⅲ neonatal intensive care units (NICU) in China. Method: A prospective study was conducted in 25 level Ⅲ NICU, enrolling all preterm infants <34 weeks gestational age admitted to the participating NICU within the first 7 days of life from May 2015 to April 2016. Chi-square test, t test and Mann-Whitney U test were used for statistical analysis. Result: A total of 7 918 patients were enrolled, within whom 4 623(58.4%) were males. The birth weight was (1 639±415) g and the gestational age was (31.4±2.0) weeks; 4 654(58.8%) infants required non-invasive mechanical ventilation and 2 154(27.2%) required intubation. Of all the mechanically ventilated patients, VAP occurred in 95 patients. The overall VAP rate was 7.0 episodes per 1 000 ventilator days, varying from 0 to 34.4 episodes per 1 000 ventilator days in different centers. The incidence of VAP was 9.6 and 6.0 per 1 000 ventilator days in children's hospitals and maternity-infant hospitals respectively, without significant differences (t=1.002, P=0.327). Gram-negative bacilli (76 strains, 91.6%) were the primary VAP microorganisms, mainly Acinetobacter baumannii (24 strains, 28.9%), Klebsiella pneumonia (23 strains, 27.7%), and Pseudomonas aeruginosa (10 strains, 12.0%). Conclusion: The incidence of VAP in China is similar to that in developed counties, with substantial variability in different NICU settings. More efforts are needed to monitor and evaluate the preventable factors associated with VAP and conduct interventions that could effectively reduce the occurrence of VAP.

Collagen gene expression in radiation interstitial pneumonitis.

By using type I and type III collagen cDNA probe and cDNA-mRNA in situ hybridization, we observed the changes of rat lung alpha 1(I) and alpha 1(III) collagen gene expression in radiation interstitial pneumonitis. The results showed that the expressed cell of type I and type III collagen were scattered within the fibroblasts in the thickened interalveolar walls. The type I and type III collagen mRNA content in irradiated animals were higher than those in the controls at 0.5, 1, 2, 3, 6, and 12 months.

Apoptosis of lymphocytes in canine peripheral blood induced by shock vibration and its mechanism.

We investigated the mechanism of apoptosis induced by shock vibration in canine peripheral lymphocytes, the T-lymphocyte changes, and the expression of p53 and bax gene products related to apoptosis using the techniques of immuno- and enzyme cytochemistry. We noted obvious apoptosis after delivery of 80, 100, and 200 acceleration of gravity values (G values). The percentage of apoptotic lymphocytes was directly proportional to the G value. On the 3rd day after injury, the number of apoptotic lymphocytes reached the peak value, which was about 5 to 8 times the amount in the control group. On the contrary, on day 3 after injury, T lymphocytes decreased and were about 50% of the control group. On the other hand, we found that the percentage of p53 and bax-positive lymphocytes distinctly increased and, on the 3rd day after injury, their number was, respectively, about 2.3 and 1.8 times that in the control groups, suggesting that they may play an important role in lymphocyte apoptosis. The above-mentioned results provide an important basis for further study of the mechanism of shock-vibration injury, its prevention, and treatment.

Apoptosis of circulating lymphocytes induced by whole body gamma-irradiation and its mechanism.

We studied the apoptosis of mousecirculating lymphocytes and its mechanism induced by 2, 4, 6, and 8 Gy of whole-body gamma-irradiation and the expression of bax and bcl-2 gene products as related to apoptosis. We found that, in the early stage after irradiation (4th-7th day), the percentage of lymphocyte apoptosis increased rapidly. Four hours after 2, 4, 6, and 8 Gy of gamma-irradiation, the apoptotic lymphocytes were 2.6, 3.8, 5.5, and 10.4 times those in the controls, respectively. A good correlation was found between the intensity of apoptosis and the radiation dose. As the radiation dose increased, the absolute counts of peripheral lymphocytes decreased sharply; 4 hours after 2, 4, 6, and 8 Gy of gamma-irradiation, the lymphocyte counts were 82, 63, 47, and 22% of the controls, respectively. The peak value of lymphocyte apoptosis was observed on the 7th day after irradiation using the in situ terminal labeling method, and the apoptotic lymphocytes were found to be 16 times the number in the controls. These results were in accordance with those obtained by the May-Grünwald-Giemsa staining method. The absolute counts of peripheral lymphocytes dropped to their lowest value on the 7th day after irradiation, suggesting that lymphocyte apoptosis might be the major cause of lymphocytopenia in the early stage after irradiation. The abnormal expression of bax and bcl-2 gene products in irradiated lymphocytes was closely related to apoptosis in peripheral lymphocytes.