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Abstract
An increasing prevalence of infections caused by multidrug-resistant (MDR) Pseudomonas aeruginosa (P. aeruginosa) causes a serious therapeutic problem in clinical setting. This study investigated the antimicrobial susceptibility, resistance mechanisms against aminoglycosides, and molecular epidemiology of 76 blood isolates of P. aeruginosa from two Korean hospitals. Thirty-four isolates were susceptible to all 13 antimicrobial agents tested, whereas 28 isolates showed a MDR or extensively drug-resistant phenotype. There was a significant difference in resistance rates of P. aeruginosa isolates against aztreonam, piperacillin-tazobactam, imipenem, meropenem, ciprofloxacin, and norfloxacin between two hospitals. Genes for aminoglycoside-modifying enzymes (AMEs), including aphA6 (n = 14), aadB (n = 11), aacA4 (n = 8), and aphA1 (n = 1), and 16S rRNA methylase armA (n = 6) were detected in 26 P. aeruginosa isolates resistant to aminoglycosides. There was no significant difference in carriage of genes for AME and 16S rRNA methylase between two hospitals, but aacA4 and aphA1 were specifically detected in P. aeruginosa isolates from one hospital. Seventy-six P. aeruginosa isolates were classified into 55 pulsotypes at similarity value of 0.85, and 31 and 24 pulsotypes were specifically detected in each hospital. This study demonstrates that differences in antimicrobial susceptibility of P. aeruginosa isolates between two hospitals are possibly due to the presence of diverse clones specific in each hospital.
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Figure 1.
Pulsed-field gel electrophoresis analysis of 76 P. aeruginosa isolates from two Korean hospitals. Dendrogram showing a clustering of Spe Igenerated PFGE patterns from P. aeruginosa isolates. Abbreviations: KNUH, Hospital A; CNUH, hospital B.
Table 1.
PCR primers used in this study
Table 2.
Antimicrobial susceptibility of P. aeruginosa isolates from two Korean hospitals
Table 3.
Antimicrobial susceptibility profiles that fit MDR, XDR, and PDR for 76 P. aeruginosa isolates
| Antimicrobial susceptibility profilesa | No. of isolates (%) | ||
|---|---|---|---|
| Total (n = 76) | Hospital A (n = 39) | Hospital B (n = 37) | |
| Susceptible to antimicrobial agents | 34 (44.7) | 20 (51.3) | 14 (37.8) |
| Resistant to 1 or 2 antimicrobial categories | 14 (18.4) | 9 (23.1) | 5 (13.5) |
| Multidrug-resistant | 14 (18.4) | 6 (15.4) | 8 (21.6) |
| Extensively drug-resistant | 14 (18.4) | 4 (10.3) | 10 (27.0) |
| Pandrug-resistant | 0 | 0 | 0 |
a Multidrug-resistant (MDR), the isolate is non-susceptible to at least 1 agent in ≥ 3 antimicrobial classes; extensively drug-resistant (XDR), the isolate is non-susceptible to at least 1 agent in all but 2 or fewer antimicrobial classes; pandrug-resistant (PDR), nonsusceptibility to all agents in all antimicrobial classes for each bacterium.
Table 4.
Detection of resistant determinants for aminoglycosides in P. aeruginosa isolates from two Korean hospitals
| Resistant pattern of aminoglycosidesa | No. of isolates | Genes | No. of isolates | |
|---|---|---|---|---|
| Hospital A | Hospital B | |||
| aadB, armA | 1 | 4 | ||
| aphA6, aadB | – | 4 | ||
| Amk, Gem, Tob, Ntl | 13 | aacA4, aphA6, aadB | 2 | – |
| aacA4, aphA6, armA | 1 | – | ||
| Not detected | – | 1 | ||
| Gem, Tob, Ntl | 11 | aacA4 | 4 | – |
| aphA6 | – | 7 | ||
| Amk, Gem | 1 | Not detected | 1 | – |
| Gem, Ntl | 1 | aphA1 | 1 | – |
| Ntl, Tob | 1 | aacA4 | 1 | – |
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