The Study Of The Etiology Of Hospital Acquired Pneumonia

Objectives: To investigate the etiology and the etiological bacteria resistance of HAP in our hospital, impact of duration of hospitalization on etiology, the influence of prior antimicrobial exposure and severity of pneumonia to etiological bacteria resistance.Methods: By the way of investigation of three times a week rounds, identify the eligible patients with HAP from September 1, 2005 to December 31, 2005. Record relevant clinical data, including age, gender, underlying disease, clinical diagnosis, duration of hospitalization, prior exposure to antimicrobials or glucocorticoid, immunodeficiency , artificial airway or mechanical ventilation. Collect respiratory tract secretion to culture and analysis the susceptibility of antimicrobials, identify the etiology and resistance of HAP in our hospital. T test or x₂ test was used to analysis the patients' characters between early-onset and late-onset HAP, impact of onset time, prior antibiotics exposure and severity of HAP to drug resistant bacteria. Results: During the 4 months there were 77 cases suffering from HAP, it occurred at a rate of 1.04%. There were 22 cases of early-onset HAP(25.97%) and 57 cases of late-onset HAP(74.03%), including 13 cases of ventilator associated pneumonia and 17 cases of severe HAP. Among these patients, 54 cases were males and 23 cases were females, age ranged from 9 to 95 years, at a average age of 64.5 ± 19.9 years. The rate of prior antibiotics use increased from 75% in early-onset HAP group to85.96% and 88.24% in late-onset HAP and severe HAP group.82 strains of bacteria were isolated from respiratory tract secretion culture. The positive rate was 71.43%, and that of early-onset HAP and Late-onset HAP were 55% and 77.19%. In the 82 strains of etiologic agents, there were 32 strains of G+ cocci(39.02%) and 50 strains of G" bacterium(60.98%).The most common pathogens associated with HAP were Pseudomonas aeruginosa(\5.%5%), Acinetobacter baumanii(l3A\%), Klebsiellapneumonia(\2.20%), Enterococcus (12.20%), MRSA(9.76%). Early-onset HAP were commonly saused by G+ cocci such as MSSA and Streptococcus penumoniae. While the main agents of late-onset HAP were G' bacilli including Pseudomonas aeruginosa, Acinetobacter baumanii, Klebsiella pneumonia and Enterococcus, Staphylococcus aureus.A total of 40 strains of drug resistant bacteria were isolated during this study period, including MRSA(8 strains, 61.54%), MRSCoN(8 strains,85.71%), multidrug resistant Pseudomonas aeruginosa(% strains), Acinetobacter baumanii(7 strains), Stenotrophomonas Maltophilia(4 strains,), Escherichia coli with ESBLs(3strains,60%), Klebsiella pneumonia with ESBLs(2 strains, 20%). The resistant stains isolated rate was 21.43% in Early-onset HAP, while that of late-onset HAP was 54.41%(P<0.05). Compared with not using antimicrobials, prior antimicrobials exposure increases the resistant bacteria rate(P<0.05). The isolated resistant bacteria rate of severe HAP was 72.22% , more than that of mild-to-moderate HAP(P<0.05).External susceptibility test showed, most of the HAP pathogens were resistantto the antimicrobials commonly used in clinic. Vancomycin was sensitive to all of the isolated G+ cocci at a rate of 100%, Carbepenem was sensitive to most of the G' bacilli except Stenotrophomonas Maltophilia .Cefoperazone-Sulbactam and Piperaclillin-tazobactam had high antibiotic activity to most of the G" bacilli.The prognosis of HAP was poor. The crude mortality was 16.88%, it was 8.33% in mild-to moderate HAP group, and 47.06% in severe HAP(P<0.05). The crude mortality was 15% in early-onset HAP, while Late-onset HAP mortality was 17.24%.CONCLUSIONS: HAP occurred at a rate of 1.04% in our hospital. Most of the patients were old with several underlying diseases and prior broad-spectrum antibiotics exposure . The core pathogens of HAP in our hospital are Pseudomonas aeruginosa, Acinetobacter baumanii , Klebsiella pneumonia, Enterococcus and MRSA. Non-fermenters and drug resistant pathogens isolation rate were higher, prolongation of hospital stay, the broad-spectrum antibiotics, and severe HAP were risk factors for drug resistant bacteria. The prognosis of HAP was poor. The crude mortality was 16.88% , it was 8.33% in mild-to moderate HAP group, and 47.06% in severe HAP. The crude mortality was 15% in early-onset HAP, while Late-onset HAP mortality was 17.24%.