Prevalence and resistance of Pseudomonas aeruginosa in severely burned patients: a 10-year retrospective study

Infection complications caused by gram-negative bacteria nowadays constitute the dominant mortality cause in severely burned patients. Pseudomonas aeruginosa is the most feared nosocomial pathogen among burn centers worldwide, with the highest mortality.

The study involved adult patients hospitalized at the Intensive Care Unit at the Department of Burns and Reconstructive Surgery, University Hospital Brno, between the years 2000 and 2009. These patients were hospitalized for thermal injuries. Retrospectively we have evaluated the extent of the burned areas, ages, depth of injury at admission and at discharge or in dissection (histology) and length of hospitalization on the Intensive Care Unit. By completing regular swabs we monitored and evaluated the microbiological situation not only at the burned areas but also in the lower respiratory system, in the urinary tract and in the blood stream.

The study involved a total of 640 adults hospitalized at the Intensive Care Unit at the Department of Burns and Reconstructive Surgery, University Hospital Brno, for burn trauma between the years 2000 and 2009. The average extent of the burned area in patients was 36.2% TBSA (2-97% TBSA), average age was 36.7% years (18-92 years), average length of hospitalization at the Intensive Care Unit was 27.1 days (1-151 days). We isolated a total of 2,958 strains of Pseudomonas aeruginosa (including repeated isolation of pseudomonas strains in the same patients) in these patients. The most frequently found of these was Pseudomonas aeruginosa isolated from the burned area (1,301 strains), from the lower respiratory system (651) and from the urinary tract (592 strains). During the monitored period the number of strains isolated in our patients increased (146 strains in 2000, 521 strains in 2009). Furthermore, we noticed increased resistance to all available antibiotics except Polymyxins. All of the Pseudomonas aeruginosa strains in the monitored years maintained 100% sensitivity to Colistin. Of the routinely used antibiotics Meropenem showed the greatest increase of resistance (in 2000 this comprised a total of 18% of the resistant Pseudomonas aeruginosa strains, and in 2009 58% of the strains). Ceftazidime shows similar results (in 2000 12%, in 2009 39% of resistant strains). Amikacin displayed a relatively good effect against pseudomonas infections; in 2009 we registered total of 34% of the resistant strains of Pseudomonas aeruginosa to this aminoglycoside. In 2000 there were 13 multiresistant strains (i.e. 8.9%) of Pseudomonas aeruginosa, in 2009 the figure was 171 strains (i.e. 32.82%).

In our study we point to the increasing trend not only in the prevalence but also in the resistance of Pseudomonas aeruginosa strains. This limits our choices for suitable antibiotic therapy. This is why infection complications play such a significant role in morbidity and mortality in severely burned patients.