Bacterial population and antibiotic resistance in an ICU during a 4-year period

Introduction

Nosocomial infections are responsible for significant morbidity and mortality in ICU patients. This is particularly important considering the emergence of multidrug-resistant bacteria. Our aim was to retrospectively study the bacterial population responsible for colonization and infection of patients hospitalized in a multidisciplinary seven-bed ICU in a general hospital, as well as antibiotic resistance, during a 4-year period.

Methods

Nine hundred and forty-eight patients were admitted to the ICU from September 2003 to September 2007. Blood, bronchial aspirates, urine, pus, drainage fluid (trauma, pleural, ascitic) and central venous catheter (CVC) tips were cultured for diagnostic purposes as well as for colonization surveillance.

Results

Gram-negative bacteria were most commonly isolated (59%). The most frequent isolates were Acinetobacter baumannii (35%) and coagulase-negative Staphylococci (CNS) (30%) followed by Klebsiella pneumoniae (12%) and Pseudomonas aeruginosa (12%). Enterococci (6%) and Staphylococcus aureus (4.6%) were rarely isolated.

Seventy-five percent of S. aureus strains were methicillin resistant, but all were sensitive to linezolid, teicoplanin and vancomycin. Ninety percent of CNS strains were methicillin resistant, 1.1% was resistant to linezolid, 3.3% were resistant to teicoplanin, but all strains were sensitive to vancomycin. Four percent of Enterococcus strains were resistant to linezolid, while teicoplanin and vancomycin resistance was 32.6% and 35.8%, respectively.

Ninety-seven percent and 68% of A. baumannii strains were resistant to aminoglycosides and carbapenemes, respectively, while resistance to colimycin showed a significant increase during the last 2 years (from 5% to 16%). K. pneumaniae strains were resistant to aminoglycosides in 40%, aztreonam in 57%, and carbapenemes in 52%, while they were found to have an increasing resistance to colimycin with time (18% in 2006 to 34% in 2007). Finally, only one P. aeruginosa strain was found to be colimycin resistant.

Conclusion

Gram-negative resistant strains predominate among our ICU bacterial population. During the 4-year study period the overall bacterial resistance, although high, remains relatively stable. Emerging Gram-negative bacterial resistance to colimycin poses a potential therapeutic problem for the future.