OBJECTIVE To investigate the pathogens of HAP and their drug resistance in our hospital,the impact of duration of hospitalization on etiology,and the risk factors for the resistant pathogens.METHODS The respiratory tract secretion was collected from HAP patients to culture and analyze the susceptibility of antimicrobials,compare the etiology of early-onset and late-onset HAP including prior antibiotics exposure and severity of HAP to drug resistant bacteria.RESULTS During the period of study,there were 1.04% of patients suffering from HAP.Early-onset HAP was commonly caused by G+ cocci while the main agents of late-onset HAP were G-bacilli.Most of the HAP pathogens were resistant to the antimicrobials commonly used in clinic with the prior antimicrobials exposure and the severe HAP increased the resistant bacteria rate(P