Changes in bacterial flora and antibiotic resistance in clinical samples isolated from patients hospitalized in the Military Institute of Medicine in Warsaw, Poland, between 2005-2012

Hospital infections have become an important problem. Knowledge of microbiological situations both helps in ensuring that the optimal choice of antibacterial treatment is made, and in improving the results of the selected therapy.In this paper, both the changes in the bacterial flora of patients hospitalized in the Military Institute of Medicine, and the bacterial resistance to antimicrobials were analyzed.Data were collected between 2005 and 2012. The identification and testing of pathogens, susceptibility tests, and analysis of bacterial resistance mechanisms to antibiotics were performed according to current guidelines.A total number of 28,066 bacterial strains were isolated. The most frequently isolated pathogens were Gram-negative bacteria (n=18,021; 64% of all isolated bacteria), including Enterobacteriaceae (71%) and non-Enterobacteriaceae (29%). The total number of isolated Gram-positive bacteria (n=10,045; 36% of all isolates) included Staphylococcus spp. (65%) and Enterococcus spp. (35%). The highest increase in the number of infections was caused by Enterobacteriaceae. The number of Staphylococcus aureus and coagulase negative Staphylococcus resistant to methicillin decreased. Analyzed alert pathogens with resistance phenotypes were highly susceptible to a single type of antibiotic. All multidrug resistant Gram-negative bacteria (except those naturally resistant to colistin) were susceptible to colistin. All methicillin resistant S. aureus and methicillin resistant coagulase negative Staphylococci were susceptible to vancomycin and linezolid. All MSSA strains were susceptible to cloxacillin, all Enterococcus faecium strains to ampicillin, and all VRE strains were susceptible to linezolid and tigecycline.