Changes in antibiotic resistance of the most common Gram-negative bacteria isolated in intensive care units

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Summary

We studied the changes in antibiotic resistance of the most common Gram-negative bacteria isolated in the intensive care units at our hospital in 2000 and 2002. Bacterial identification was performed by use of the VITEK 60 analyser, and antibiotic susceptibilities were tested by the VITEK 60 analyser and the disk diffusion agar method. The bacteria isolated most frequently were Pseudomonas aeruginosa (132 strains in 2000 and 106 in 2002), Acinetobacter calcoaceticus (98 and 109 strains, respectively) and Klebsiella pneumoniae (53 and 83 strains, respectively). Acinetobacters presented the highest percentage resistance, with significant increases in resistance to imipenem (15% in 2000 and 67% in 2002) and piperacillin/tazobactam (41% and 72%, respectively). P. aeruginosa presented a significant increase in resistance to all antibiotics, except ceftazidime. A large increase was observed in the resistance of K. pneumoniae to amikacin (from 10% to 50%), ceftazidime (from 80% to 90%) and tobramycin (from 80% to 90%). No imipenem-resistant strains of K. pneumoniae were found.

Introduction

Patients in intensive care units (ICUs) experience high rates of infection,1, 2 and resistance to antimicrobial agents is an increasing problem in ICUs. In surgical ICUs, increased resistance to antimicrobial agents has been attributed to frequent use of broad-spectrum antibiotics.3 The aim of the present study was to investigate the changes in antibiotic resistance of the most common Gram-negative pathogens isolated from patients in the ICUs at a university hospital and to compare the resistance profiles between 2000 and 2002.

Section snippets

Materials and methods

AHEPA Hospital is a public university hospital with 637 beds. It has four surgical ICUs, totalling 48 beds. Around 36 000 patients are admitted each year.

In the surgical ICUs, approximately 2600 patients were hospitalized in the two study years (1100 and 1500 patients in 2000 and 2002, respectively). A total of 283 and 298 Gram-negative isolates, representing 258 and 264 patients of the surgical ICUs, were collected during these two years, respectively. The clinical specimens consisted of:

Results

The most common bacteria isolates were: Pseudomonas aeruginosa (132 strains in 2000 and 106 in 2002), Acinetobacter calcoaceticus (98 and 109 strains, respectively) and Klebsiella pneumoniae (53 and 83 strains, respectively).

Discussion

The three Gram-negative bacteria reported here are common causes of ICU-acquired infections.5, 6, 7, 8, 9, 10, 11, 12

P. aeruginosa showed a significant increase in resistance rates for most of the antimicrobial agents between 2000 and 2002. Although P. aeruginosa may sometimes acquire antimicrobial resistance genes by plasmid transfer, most acquired resistance to aminoglycosides, carbapenems, fluoroquinolones and newer cephalosporins is due to mutation.13, 14, 15, 16, 17, 18, 19 Carriage of

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    Copyright © 2005 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved.