Antimicrobial susceptibility of Gram-negative bacteria causing nosocomial infections from 2003–2005 in a university hospital in Turkey

Abstract number: P1182

Kibar F., Kurtaran B., Candevir A., Inal A.S., Bicer A., Oksun E., Tasova Y., Yaman A.

Objective: The aim of this study was to determine about antibiotic susceptibilities of Gram-negative bacteria isolated from nosocomial infections.

Methods: The activity of eight broad-spectrum antimicrobial agents were assessed against 397 Gram-negative aerobic bacteria isolates collected from nosocomial infections during 2003, 2004 and 2005 in an university hospital in Turkey. Gram-negative bacteria were including E. coli(22.6%), K. pneumoniae (21.9%), P. aeruginosa (20.9%), Acinetobacter spp. (20.1%), Enterobacter spp. (7.3%), Proteus spp. (3.2%), Morganella spp. (1.2%), Providencia spp. (1.0%), Serratia spp. (0.7%) and Citrobacter spp. (0.5%). Antimicrobial susceptibility was investigated using E-test. Extended-spectrum b-lactamase (ESBL) production was determined using ceftazidime and ceftazidime/clavulanic acid E-test strips.

Results: Overall, meropenem and imipenem were the most effective antibiotics against Gram-negative organisms, respectively (77.5% susceptible, MIC50 = 0.125, MIC90  32 mg/L; 75.8% susceptible, MIC50 = 0.5, MIC90  32 mg/L); these were followed by piperacillin/tazobactam (56.4% susceptible; MIC50 = 16, MIC90  256 mg/L), ciprofloxacin (44.8% susceptible; MIC50 = 3, MIC90  32 mg/L), cefepime (42.8% susceptible; MIC50 = 24, MIC90  256 mg/L), tobramycin (39.2% susceptible; MIC50 = 16, MIC90  256 mg/L), ceftazidime (38.5% susceptible; MIC50 = 24, MIC90  256 mg/L) and cefotaxime (25.4% susceptible; MIC50  32, MIC90  32 mg/L). When these were compared with data between 2000–2002, the antibiotic susceptibilities were determined approximately lower 10% for imipenem, meropenem, piperacillin/tazobactam; 15% for cephotaxime; 20% for ceftazidime, cefepime, ciprofloxacin and tobramycin in 2003–2005. The rates of production of ESBL were 77% in K. pneumoniae and 61% in E. coli. These ESBL positive isolates were sensitive 100%, 98% to meropenem; 98.5% and 98% to imipenem, respectively. Multi-drug resistance (MDR) rates were 76% in Acinetobacter spp., 66% in P. aeruginosa. Only piperacillin/tazobactam were more susceptible than 50% against P. aeruginosa. Carbapenems were the most active agents against Acinetobacter spp. (meropenem 57.5%, imipenem 55% susceptible) AmpC b-lactamase was produced by 31.4% of Enterobacter spp., Citrobacter spp. and S. marcescens. All of these were sensitive to meropenem; 77%, to imipenem and ciprofloxacin.

Conclusion: Antimicrobial resistance has reached very high levels in hospital. Solving of this problem depends primarily on to prevention of the development of antimicrobial resistance.