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Abstract
A total of 90 Acinetobacter isolates from freshwater and seawater in Gangjin Bay of Korea was investigated for the distribution of genomic species, antimicrobial resistance patterns and clonal relatedness. By amplified ribosomal DNA restriction analysis, eighty-nine Acinetobacter isolates were classified into 11 Acinetobacter genomic species. A. johnsonii (n=23) was the most prevalent, followed by A. baumannii (n=13), A. calcoaceticus (n=13), Acinetobacter genomic species 11 (n=10), A. phenon 6/ct13TU (n=9), A. junii (n=5), A. venetianus (n=5), Acinetobacter genomic species 17 (n=4), 14BJ (n=3), A. phenon 10/1271 (n=2), Acinetobacter genomic species 3 (n=1), and ungrouped (n=1). The majority of Acinetobacter genomic species were isolated from the site A and B, and some known nosocomial pathogens in the clinical environment were observed among them. Of the 11 antimicrobial drugs tested, several A. johnsonii isolates exhibited high-frequency resistance to a wide variety of antimicrobial agents, including ampicillin-sulbactam, piperacillin, ceftazidime, cefotaxime, and sulfamethoxazole (p < 0.001). Some Acinetobacter genomic species were resistant to currently used antibiotics but all isolates were susceptible to imipenem, amikacin, and tetracycline. Based on the results of antimicrobial resistance pattern and phylogenetic analysis, 23 A. johnsonii isolates were classified into 19 pulsotypes. In conclusion, there was a significant difference in the distribution of Acinetobacter species between freshwater and seawater. Predominance of A. johnsonii strains was probably due to their ability to proliferate in the contaminated aquatic environment originated from local geographic features. Therefore, the waste effluent from animals and humans plays an important role in the distribution of Acinetobacter species in aquatic environment.
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Figure 1.
Phylogenetic analysis of 23 A. johnsonii isolates from the Gangjin Bay of Korea. CHEF electrophoresis of ApaI-digested genomic DNAs. The dendrogram is based on cluster analysis by the unweighted-pair group method with average linkages.
Table 1.
Physicochemical characteristics of sampled water at survey sites
Table 2.
Distribution of Acinetobacter genomic species in Gangjin Bay in Korea
Table 3.
MICs and the percentages of resistance (%R) of 90 Acinetobacter isolates from Gangjin Bay of Korea
| Acinetobacter genomic species (n=90) | MIC90 and %R of a | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| AMSb | PIP | CAZ | CTX | IP | CS | GM | AMK | CIP | TET | SMX | |
| A. johnsonii (n=23) | >128 / 4.4 | ≥512 / 5.6 | 128 / 10.0 | 128 / 4.4 | <1 / 0 | <1 / 0 | <4 / 1.1 | 2 / 0 | 0.5 / 2.2 | 4 / 0 | ≥1,024 / 7.8 |
| A. calcoaceticus (n=13) | 4 / 0 | ≥512 / 2.2 | 4 / 1.1 | 16 / 0 | <1 / 0 | <1 / 0 | <4 / 0 | 4 / 0 | <0.25 / 0 | 2 / 0 | 32 / 0 |
| A. baumannii (n=13) | 4 / 0 | ≥512 / 2.2 | 8 / 0 | 16 / 0 | <1 / 0 | 4 / 0 | <4 / 0 | 8 / 0 | <0.25 / 0 | 4 / 0 | 16 / 0 |
| 11 (n=10) | 2 / 0 | 64 / 1.1 | 8 / 1.1 | 16 / 0 | <1 / 0 | 8 / 5.6 | <4 / 0 | 4 / 0 | 8 / 4.4 | 4 / 0 | 16 / 0 |
| A. phenon 6ct:13TU (n=9) | 4 / 0 | ≥512 / 3.3 | 8 / 0 | 16 / 0 | <1 / 0 | <1 / 0 | <4 / 0 | 4 / 0 | <0.25 / 0 | 2 / 0 | <8 / 0 |
| A. junii (n=6) | <0.5 / 0 | 32 / 1.1 | 4 / 0 | 8 / 0 | 4 / 0 | 8 / 3.3 | <4 / 0 | 4 / 0 | 0.5 / 0 | 4 / 0 | 64 / 1.1 |
| A. venetianus (n=5) | <0.5 / 0 | 16 / 0 | 4 / 0 | 8 / 0 | <1 / 0 | 4 / 0 | <4 / 0 | 8 / 0 | <0.25 / 0 | 2 / 0 | <8 / 0 |
| 17 (n=4) | 2 / 0 | 8 / 0 | <2 / 0 | <2 / 0 | <1 / 0 | 4 / 0 | <4 / 0 | 2 / 0 | <0.25 / 0 | 4 / 0 | 16 / 0 |
| 14BJ (n=3) | 2 / 0 | 32 / 0 | 8 / 0 | 16 / 0 | <1 / 0 | 4 / 0 | <4 / 0 | 4 / 0 | 8 / 1.1 | 2 / 0 | <8 / 0 |
| A. phenon 10/1271 (n=2) | 4 / 0 | 8 / 0 | <2 / 0 | 4 / 0 | <1 / 0 | <1 / 0 | <4 / 0 | 4 / 0 | <0.25 / 0 | 2 / 0 | <8 / 0 |
| 3 (n=1) | 1 / 0 | 32 / 0 | 4 / 0 | 16 / 0 | <1 / 0 | <1 / 0 | <4 / 0 | 2 / 0 | <0.25 / 0 | 2 / 0 | <8 / 0 |
| Ungrouped (n=1) | 4 / 0 | <4 / 0 | <2 / 0 | 4 / 0 | <1 / 0 | 8 / 1.1 | <4 / 0 | 2 / 0 | <0.25 / 0 | 4 / 0 | <8 / 0 |
a AMS, ampicillin-sulbactam (MIC range, 0.5 to 128 μg/ml); PIP, piperacillin (4 to 512 μg/ml); CAZ, ceftazidime (2 to 128 μg/ml); CTX; cefotaxime (2 to 256 μg/ml); CS; colistin (1 to 32 μg/ml); AMK, amikacin (1 to 64 μg/ml); GM, gentamicin (4 to 256 μg/ml); TET, tetracycline (1 to 16 μg/ml); CIP, ciprofloxacin (0.25 to 32 μg/ml); SMX, sulfamethoxazole (8 to 1,024 μg/ml).
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