Further increases in carbapenem-, amikacin-, and fluoroquinolone-resistant isolates of Acinetobacter spp. and P. aeruginosa in Korea: KONSAR study 2009

Abstract

Purpose: The increasing prevalence of antimicrobial resistant bacteria has become a serious worldwide problem. The aim of this study was to analyze antimicrobial resistance data generated in 2009 by hospitals and commercial laboratories participating in the Korean Nationwide Surveillance of Antimicrobial Resistance program.

Materials and methods: Susceptibility data were collected from 24 hospitals and two commercial laboratories. In the analysis, resistance did not include intermediate susceptibility. Duplicate isolates were excluded from the analysis of hospital isolates, but not from the commercial laboratory isolates.

Results: Among the hospital isolates, methicillin-resistant Staphylococcus aureus, penicillin G-nonsusceptible Streptococcus pneumoniae based on meningitis breakpoint, and ampicillin- resistant Enterococcus faecium remained highly prevalent. The proportion of vancomycin-resistant E. faecium gradually increased to 29%. Ceftazidime-resistant Escherichia coli and Klebsiella pneumoniae increased to 17% and 33%, respectively, and fluoroquinolone-resistant K. pneumoniae, Acinetobacter spp. and Pseudomonas aeruginosa increased to 33%, 67% and 39%, respectively. Amikacin-resistant Acinetobacter spp. increased to 48%. Imipenem-resistant Acinetobacter spp. and P. aeruginosa increased to 51% and 26%, respectively. Higher resistance rates were observed in intensive care unit (ICU) isolates than in non-ICU isolates among the isolates from hospitals. Resistance rates were higher in hospital isolates than in clinic isolates among the isolates from commercial laboratories.

Conclusion: Among the hospital isolates, ceftazidime-resistant K. pneumoniae and fluoroquinolone- resistant K. pneumoniae, Acinetobacter spp., and P. aeruginosa further increased. The increase in imipenem resistance was slight in P. aeruginosa, but drastic in Acinetobacter spp. The problematic antimicrobial-organism combinations were much more prevalent among ICU isolates.

Fig. 1

Resistance trends of gram-positive cocci isolated in 1997-2009 from the participating hospitals. Oxacillin-resistant S. aureus (OXA-R SAU), penicillin G-nonsusceptible S. pneumoniae (PEN-NS SPN), and ampicillin-resistant E. faecium (AMP-R EFM) remained highly prevalent. However, the proportion of vancomycin-resistant E. faecium (VAN-R EFM) gradually increased from 4% in 1997 to 29% in 2009.

Fig. 2

The resistance trends of K. pneumoniae isolated in 1997-2009 from the participating hospitals. The resistance rates to ceftazidime (CAZ-R), cefoxitin (FOX-R) gradually increased and reached 33% and 25%, respectively, in 2009, whereas the resistance rate to fluoroquinolone (FQN-R) increased rapidly from 8% in 1997 to 33% in 2009. The amikacin resistance rate (AMK-R) increased to 24% in 2005 and then decreased to 15% in 2009.

Fig. 3

The resistance trends of Acinetobacter spp. isolated in 1997-2009 from the participating hospitals. The high resistance rates in 1999 to fluoroquinolone (FQN-R), amikacin (AMK-R), and ceftazidime (CAZ-R) decreased by 2007, but the rates increased again in 2009 to 67%, 66%, and 48%, respectively. The proportion of imipenem-resistant (IPM-R) isolates steadily increased from 1% in 1997 to 22% in 2007, and after that the increase was drastic, reaching 51% in 2009.

Fig. 4

The resistance trends of P. aeruginosa isolated in 1997-2009 from the participating hospitals. The high fluoroquinolone (FQN-R) resistance rates fluctuated between 33% and 42% during the study period. The amikacin resistance rate (AMK-R) declined steadily from 33% in 1997 to 19% in 2009. The resistance rates to ceftazidime (CAZ-R) and imipenem (IPM-R) increased slowly from 16% to 23% and from 17% to 26%, respectively, during the study period.

Fig. 5

Comparison of resistance rates of ICU vs. non-ICU isolates from six hospitals with >1,000 beds. Cefotaxime-resistant E. coli (CTX-R ECO), ceftazidime-resistant K. pneumoniae (CAZ-R KPN), imipenem-resistant Acinetobacter spp. (IPM-R ACI), imipenem-resistant P. aeruginosa (IPM-R PAE), oxacillin-resistant S. aureus (OXA-R SAU), and vancomycin-resistant E. faecium (VAN-R EFM) were much more prevalent among ICU isolates than among non-ICU isolates. The imipenem-resistance rate of P. aeruginosa ICU isolates was almost two-fold higher (39%) than that of non-ICU isolates (20%).

Fig. 6

The high prevalence of four antimicrobial agent-organism combinations among commercial laboratory tested isolates from hospital patients compared to those from clinic patients. The isolates from hospital patients showed a 3-fold higher rate of ceftazidime-resistant (CAZ-R) E. coli, more than 2-fold higher rates of CAZ-R K. pneumoniae and imipenem-resistant (IPM-R) Acinetobacter spp., and nearly 2-fold higher rate of IPM-R P. aeruginosa. All numbers of isolates are shown in the bars, and the proportions (%) of antimicrobial-organism combinations are shown on the bars.