Etiological Factors Causing Lower Respiratory Tract Infections Isolated from Hospitalized Patients

Lower respiratory tract infections (LRTI) account for 20-30 % of all hospital-acquired contagions. They are characterized by high mortality of hospitalized patients. The most serious form of LRTI is pneumonia, and the most common etiological factors in such cases are bacteria. The article gives the analysis of bacterial flora samples obtained from lower respiratory tract of hospitalized patients. In vitro susceptibility of pathogens to selected antibiotics has also been assessed. We carried out a retrospective analysis of 1,171 bacterial strains isolated from 1,171 patients treated in clinics of the Military Institute of Medicine in Warsaw, Poland. In most cases the samples were collected from an endotracheal or tracheostomic tube (71.5 %) and from bronchoalveolar lavage (21.7 %). The most commonly isolated pathogens included Acinetobacter baumannii (35.8 %), Staphylococcus aureus (27.6 %), Klebsiella pneumoniae (19.4 %), and Pseudomonas aeruginosa (16.2 %). Multidrug-resistant gram-negative bacteria exhibited 100 % susceptibility to colistin only. Klebsiella pneumoniae ESBL+ and Acinetobacter baumannii were most susceptible to carbapenems, while Pseudomonas aeruginosa strains to ceftazidime. Methicillin-resistant Staphylococcus aureus were 100 % susceptible to vancomycin, linezolid, and tigecycline. In conclusion, identifying the etiological factors causing infections of the lower respiratory tract and determining their drug-susceptibility is of key importance in empirical treatment.