Etiological Analysis Of Mechanical Ventilation Associated Lower Respiratory Tract Infection

Objective:To analyze the etiological characteristics and bacterial resistance in patients with mechanical ventilation associated lower respiratory tract infection of two consecutive time stage , and the development trend. To analyze etiological characteristics in different clinical condition.Methods : A retrospective study was conducted on mechanical ventilation more than three days patients who had lower respiratory tract infection in the RICU and ICU of the second affiliated hospital of Chongqing medicine university from January 2004 to January 2008. Totally 176 patients were enrolled in the study,whose sputum culture result of strain and bacterial resistance were to add up and analysis,contrast the difference between the two consecutive time stage (2004.1-2005.12 and 2006.1-2008.1),and the sputum came from lower respiratory tract through endotracheal catheter. the univariate analysis method was used to analyze the etiological characteristics in different clinical condition,including:age,sex,basic disease,method of cannula and the time of mechanical ventilation,and so on.Results:585 strain were identifed from 176 patients,Gram-negative bacteria was common,had 68.2%,and Gram-positive bacteria had 22.4%,mycetes had 9.4%. In all of the strain,the most common in order were:Pseudomonas aeruginosa,Staphylococcus aureus,baumanii,Bacillus coli and Stenotrophomonas maltophilia.Isolating rate between Gram-negative bacteria and Gram-positive bacteria and mycetes had statistics difference,mycetes was less yet,and the most common mycetes was Monilia,the second was Aspergillus.Look to the development trend of pathogens, the Bacillus Serratia marcescens's obviously increasing was the most obvious characteristics , from rare bacterial to ranked as the fifth major strains in recent two years; followed by ,Staphylococcus aureus and Stenotrophomonas maltophilia aeruginosa were increased significantly, indole Flavobacterium,Meningeal septic Flavobacterium and other rare bacteria were also increased; moreover, the ratio of enterococci in gram-positive bacteria was increased, the proportion of Candida albicans in fungus was declined, corresponding , other Candida and Aspergillus were increased .The drug resistance of Gram-negative bacteria was quite generally,especially on conventional antibiotics such as cephalosporins and penicillin, and in recent years showed increasing trend. The resistance to imipenem rate was also increased, Stenotrophomonas maltophilia Pseudomonas resistant to imipenem 100%; ESBLs increasingly high production rate, E. coli up to 73.7 %; some rare Bacterial resistance was gradually increasing, such as Serratia marcescens bacteria Bacillus . The drug resistance of Gram-positive bacteria was also very serious,staphylococci in the MRS between 52.9% -100% ,one case of vancomycin-resistant strains was discovered in Enterococcus faecalis . The resistance was significantly more severe and views.Analyze the etiological characteristics in different clinical condition found that:Gram-negative bacteria had higher and higher incidence rate with the time prolong of mechanical ventilation. Gram-positive bacteria has lower incidence rate in nasal intubation patients,and had lower and lower incidence rate with the time prolong of mechanical ventilation,and had higher incidence rate in elder patients,especially more than 80 years old. mycetes had higher incidence rate in COPD,nasal intubation and bad prognosis patients. Gender had no apparent impact on distribution of pathogens .Conclusion: strain in invasive mechanical ventilation associated lower respiratory infection remained obviously of Gram-negative bacteria,and Pseudomonas aeruginosa was most common Gram-negative bacteria. Rare opportunistic pathogen especially Serratia marcescens was increasing rapidly in recent two years. Nomatter Gram-negative bacteria or Gram-positive bacteria ,resistance phenomenon was quite Severity, had high ESBLs and MRS masculine rate,the increase of the drug resistance was obvious. Gram-negative bacteria had higher and higher incidence rate with the time prolong of mechanical ventilation. Gram-positive bacteria had lower incidence rate in nasal intubation patients,and had lower and lower incidence rate with the time prolong of mechanical ventilation,and had higher incidence rate in elder patients,especially more than 80 years old. mycetes had higher incidence rate in COPD,nasal intubation and bad prognosis patients.