Background:Secondary bacterial co-infections are not common in patients with COVID19.However ,the rate of bacterial pneumonia is high in critically ill patients with COVID19 and there is increased risk of joining bacterial infection by increasing of severity of COVID19 and achieving maximal rate in intubated patients.And there is increased rate of overuse of broad-spectrum antibiotics in patients admitted to the intensive care unit(ICU) department.Objective:The aim of our investigation was to evaluate the rate of secondary bacterial co-infection in critically ill patients with COVID19 and its impact to the mortality rate in such patients.Method and measurements:Of 129 COVID-19 patients admitted in our ICU from 21 April 2020 to 15 August 2020,93 have been mechanically ventilated.BALF was performed in 68 patients during ICU stay and all were suspected of bacterial pneumonia.Bacterial cultures of BALF positively defined in case of grew with significant amount of bacteria(ie,>_10 4 colony-forming units/ml).All pneumonia cases in intubated patients was assessed as Ventilator -associated pneumonia(VAP) and was defined as eraly-onset and late onset as pneumonia diagnosed before and after 5 days of mechanical ventilation,respectively.Results:In 51% (n=35) of 78 patients was obtained bacterial cultires and just in 5(7.4%) of 68 patients was evaluated the early-onset VAP and in remaining 63 patients (92%) of patients was detected late-onset VAP.VAP in patients commonly was associated with ARDS compared to non-VAP patients(OR 3.57[0.89-7.92]CI 95%;p=0.001) and although late -onset VAP in patients significantly often was associated with kidney failure (OR 2.95[075-6.32]CI 95%;p=0.003) and septic shock 3.68[1.05-8.21] CI95%;p=0.001).In all early -onset pneumonia patients ,bacterial pathogens were most commonly gram positive bacteria(100%) and 80%(4/5) were susceptible to cefotaxime,cefepime,piperacillin-tazobactam,and meropenem.Conversely,in late-onset VAP,most bacterial pathogens were gram-negative bacteria(29/30) and muti-drug resistant (MDR)pathogens(14/30).Among MDR gram-negative bacteria causing late-onset VAP,most commonly was obtained Acinotebacter baumannii(9/30),followed Pseudomonas aeruginosa(6/30),folowed Klebsiella pneumoniae (5/30) and Escherichia coli(5/30) and Aspergillus fumigates(5/30).And just 13% of patients with late-onset VAP were susceptible to piperacillin-tazobactam,17% were susceptible to cefepime and 34% were susceptible to meropenem.Late-onset VAP was associated with high mortality rate among intubated compared to early-onset VAP and non-VAP patients ( OR 4.87[1,] CI95%;p=0.001;OR 6.33[1.58-14.25] CI 95%;p=0.0008).Conclusions:Secondary bacterial co-infection is common in intubated critically ill patients with COVID19 and most commonly presentation of bacterial infection is late-onset VAP causing by multi-drug resitant pathogens which are associated commonly with ARDS,kidney failure and septic shock.In patients with late-onset VAP MDR pathogens may predict high mortality rate