Abstract： Objective To investigate the pathogens, their drug sensitivities and molecular typing in patients suffering from acute irritant and suffocating gas poisoning under mechanical ventilation. Methods Samples from lower respiratory tracts and breathing circuits of 15 gas poisoning patients and those from hand swabs and fiberoptic bronchoscopies were collected. Pathogens were isolated and drug sensitivity tests and pulsed field gel electrophoresis (PFGE) analysis were performed for those with high isolation rates. Results There were average 3. 86 kinds of isolates in the lower respiratory tracts per patient. Stenotrophomonas maltophilia ranked first, and followed by Enterococcus faecalis, Acinetobacter baumannii, Staphylococcus epidermidis and Candida albicans. Stenotrophomonas maltophilia was resistant to most antibiotics with the resistant rates above 60%. PFGE analysis showed that the isolates from patients and those from hand swabs and fiberoptic bronchoscopies were of the same type. Conclusions It suggests that multi-pathogen infections exit in the lower respiratory tracts of patients who suffered from acute irritant and suffocating gas poisoning with mechanical ventilation. The pathogens are resistant to most antibiotics and their clones may be transmitted among the patients.