| Objective: Nosocomial infections are more susceptible to occur in intensive-care units(ICU).Several risk factors have been identified, especially ventilator associated pneumonia( VAP) has been identified as an independent risk factor for death of patients with mechanical ventilation and are associated with substantial morbidity and mortality.Pseudomonas aeruginosa and Acinetobacter baumannii have become the most frequent gram-negative pathogen isolated from hospital acquired pneumonia.Most of these showed multi-drug resistance (MDR).There is no universally agreed-upon approach to the management of identifying colonization or infection of the muti-drug resistant bacterial in panties.The empiric antibiotic therapy and antibiotic abused maybe lead to a higher rate of VAP and excessive mortality.We prospectively evaluated the diagnosis and assessment of bronchial mucosa biopsy and quantitative culture of bacterial in 50 Patients who had muti-drug resistant bacterial associated with invasive ventilation, so as to identify characteristics of Non-fermentative gram-negative bacterial colonization and infection, reduce the unnecessary use of antibiotics and prevent the occurrence of VAP.Methods: A prospective observational cohort survey on MDR Pseudomonas aeruginosa and Acinetobacter baumannii was carried out in intubed or tracheotomied patients in RICU( Respiratory intensive care unite ). A total of 50 ICU patients were followed for the detection of MDR pathogen colonization or infection from Jun. 2008 to Oct.2009.All subjects were divided into two groups :infection group and colonization group according to the outcome of patients discharged from the RICU. Data, including basic information, APACHEⅡscores, CPIS scores, the incidence of ventilator- associated pneumonia and so on, were recorded on individual forms for each patient until discharge or death. Bronchial mucosa biopsy was conducted in an appropriate time to identity whether the patient was conformed as infection. Microbiological diagnosis was performed with use of quantitative culture.When patients with mechanical ventilation 5 ~14d in relatively stable conditions signed informed consent ,acrossing bronchoscopy protective brushed lower respiratory tract secretions and biopsied bronchial mucosa conferring to the patients lung CT to choice obvious inflammation location. Collected specimens were put immediately to the homogenized tubes with sterile saline 1ml , and the solution were made through homogenating, in 30 minutes senting to the bacteria room for microbiologic quantitative cultures.The other bronchial mucosa set to the sterile bottle containing formaldehyde was sent to pathology department, followed by observation of pathological changes and count inflammatory cell through histological section(taking the mean number of inflammatory cells from five high-power field of view).At the same time specimens from endotracheal aspirate was collected, for reference.Differences in different groups values were evaluated using t or Chi-square tests. All statistical analyses were performed using SPSS software (version 11.0). P value less than 0.05 was considered to be statistically significant.Results:1. Fifty patients were enrolled in this study,of which infected with 23 cases and colonizated of 27 cases .The time of invasive mechanical ventilation, length of stay, catheter indwelling time, and the kinds of disease, between the two groups, showed a significant difference(p < 0.05).The kinds of using antibiotic before onset of muti-drug resistance of bacteria showed that cefoxitin / cefmetazole and mezlocillin also had significant difference between infection and colonization group. In addition, the incidence of VAP from colonization group is significantly lower than the infected group (respectively 18.5%, 47.8%), which showed a statistically significant difference(χ2= 4.903, p<0.05). However, the incidence of death from colonization group although slightly higher than the infected group, but statistical analysis showed no statistically significant difference.2 The results of dynamic CPIS score (intubation 24h, intubation 5 ~ 7 days and intubation 14 days) showed that scores during three periods of infection group were higher than that in the colonization group. However, the results of t-test showed that there was higher score in infection than that in coloniazation group at the point of intubation 14 days(p<0.05).3 The bronchial mucosa biopsy showed inflammation in infected group was detected in 19 cases (82.6%) and planting group was 9 cases (33.3%).So detection rate about inflammation in infection group was significantly higher than colonization group,and the difference was statistically significance(p<0.05).The traditional threshold of 103 cfu/ml for PSB during quantitative bacterial culture,the positive rate from infection and colonization group were 55.6% and 25.0%,and positive rate of infection was significantly higher than planting group, and the difference was statistically significance(Χ2=5.748, p=0.017<0.05).And the study about joint of bronchial mucosa biopsy and microorganism quantitative cultures found positive rate of diagnosis from infection group as high as 91.3%, far higher than colonization group, and the difference was statistically significant.4 Pathological morphous and counting inflammatory cell , which showed that infection patients with airway inflammation had typical pathological changes, and some colonization group had not typical pathological changes of inflammation.To further assess whether total number of inflammatory cells was changed between the two groups,the results showed that there was more inflammatory cells in patients with drug- resistant pathogens infection(41 / HPF) than that in the patients without nosocomial infection (17 / HPF),furthermore, neutrophil, the predominant inflammatory cells,revealed a significant increase in infection patientsgroup than that in colonization group (p<0.05).Infected group with airway inflammation comparing to the colonization group without airway inflammationin showed the number of eosinophils, neutrophils, and inflammatory cells were statistically significant differences .And the colonization group with airway inflammation and the colonization group without airway inflammationin had not significant difference in number of inflammatory cells .5 Diagnosis evaluation of the three methods showed that joint of bronchial mucosa biopsy and microorganism quantitative cultures had the highest sensitivity and specificity(70.0%, 90.0%)and lower false- positive rate and false-negative rates ,so had the highest diagnostic accuracy(Youden index is 0.6).The method of joint was better than individual pathology or microorganism quantitative cultures and the difference was statistically significant.6 Results of pathogen resistant test showed that 24 were found in Pseudomonas aeruginosa, Acinetobacter baumannii 26,and each bacteria had shown the rate of drug-resistant from colonization group was significantly higher than the infected group, and Acinetobacter baumannii resistance rates were higher than P. Aeruginosa for the same antimicrobial agents (except minocycline).Conclusions: Bronchial mucosa biopsy combining microorganism quantitative cultures is feasible in identifying colonizated or infected multidrug-resistant bacteria and clinically is superior to common method of bacteria quantitative cultures from this preliminary studies , but limits to the operation higher, requiring medical skilled operator and patient tolerance and so on. It can be further promoted to be a large sample in-depth study.We also finds that invasive mechanical ventilation time, ICU length of stay and the catheter indwelling time extending are risk factors for bacterial colonization. And so it is essential to strengthen prevention , reducing the incidence of bacterial colonization. Multidrug-resistant bacteria and cross-resistance phenomenon are prevalent in our RICU .It is necessary to explore drug resistance mechanisms and regularity, and thus guide clinical practice.
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