ABSTRACT
p-Hydroxybenzoic acid can be oxidized by hydroxyl radicals ( · OH) to produce electroactive 3,4-dihydroxybenzoic acid (3,4-DHBA). Therefore, it can be used as a probe to detect ·OH. In this work, 3,4-DHBA/ PPy / TiO2 molecularly imprinted polymer film was prepared for indirect determination of ·OH based on its recognition ability for 3,4-DHBA. The sensor was constructed by using pyrrole as the functional monomer and 3, 4-DHBA as the template molecule. The sensor was characterized by scanning electron microscope and different electrochemical methods. The preparation and determination conditions, such as the electropolymerization cycle number, pH value in the electropolymerization process, and elution time, were optimized. Under the optimal conditions, a linear range of 1. 0×10-8-1. 0×10-6 mol/ L was obtained for 3,4-DHBA and the detection limit was down to 4. 2×10-9 mol/ L (S / N = 3). This new approach was of low cost and convenience, and was successfully applied to measure the concentration of ·OH in the atmosphere.
ABSTRACT
<p><b>OBJECTIVE</b>To study the risk factors for neonatal ventilator-associated pneumonia (VAP) and the changes of isolated pathogens in the last eight years.</p><p><b>METHODS</b>The clinical data of 230 neonates who were admitted into the neonatal intensive care unit (NICU) and received mechanical ventilation for equal to or longer than 48 hrs in 2008 were retrospectively reviewed. The isolated pathogens were compared with those of eight years ago.</p><p><b>RESULTS</b>The incidence of VAP (25.2%) in the year 2008 was lower than that of eight years ago (36.1%; P<0.05). The development of VAP was negatively correlated with the gestational age and the birth weight, but positively correlated with the duration of mechanical ventilation, intubation times, duration of hospitalization, presence of gastrointestinal bleeding and need for blood products transfusion. The main isolated pathogens were opportunistic antibiotics resistant bacteria, and the majority was gram negative bacilli (77%). The most frequently detected gram negative bacilli were Klebsiella (20%), Stenotrophomonas maltophilia (18%) and Acinetobacter (13%). Streptococcus mitis was the most frequently detected gram positive bacilli (14%). The distribution pattern of pathogens isolated in the same NICU eight years ago was somewhat different: Klebsiella (23%), Pseudomonas aeruginosa (17%), Acinetobacter (16%), Streptococcus mitis (11%), Fungi (1%) and Candida albicans (1%).</p><p><b>CONCLUSIONS</b>The incidence of VAP is correlated with gestational age, birth weight, duration of mechanical ventilation and hospitalization, intubation times, presence of gastrointestinal bleeding and need for blood products transfusion. The main isolated pathogens are usually antibiotic resistant opportunistic bacteria. The detection rate of Stenotrophomonas maltophilia increased and that of Pseudomonas aeruginosa decreased when compared with eight years ago.</p>