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Journal of Clinical Microbiology, November 2004, p. 5427-5428, Vol. 42, No. 11
0095-1137/04/$08.00+0 DOI: 10.1128/JCM.42.11.5427-5428.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
| CASE REPORT |
Stephane Tercian,2
Michel Drancourt,1,3* and
Didier Raoult1,3
Fédération de Microbiologie Clinique,1 Service de Chirurgie Pédiatrique, AP-HM Timone,2 Unité des Rickettsies, CNRS UMR 6020, IFR 48, Faculté de Médecine, Marseille, France3
Received 26 April 2004/ Returned for modification 9 June 2004/ Accepted 8 August 2004
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The microbiological result confirmed a urinary tract infection due to Aeromonas sp., with intermediate susceptibility to amoxicillin and amoxicillin-clavulanate and susceptibility to ceftriaxone, ciprofloxacin, gentamicin, and cotrimoxazole. Treatment was changed to orally administered cotrimoxazole (800/160 mg twice per day), with a favorable clinical evolution later.
Urine was cultured aerobically on Trypticase soy agar (bio-Mérieux, Marcy l'Etoile, France) at 37°C. After 48 h, 3-mm whitish colonies with irregular edges were observed. Gram staining revealed gram-negative, straight motile rods. Catalase and oxidase were positive, with resistance to vibriostatic agent O/129. The API-20 NE (bioMérieux) profile was 7 477 745, corresponding to a low level of discrimination between Aeromonas hydrophila or Aeromonas caviae (percentage of identification, 91.5%; T index, 0.76) and Vibrio parahaemolyticus (8.3% identical; T index, 0.58) (profile book, 6th ed., 1997).
The antibiotic susceptibility profile was studied on sheep blood Mueller-Hinton agar plates by the disk diffusion method according to NCCLS recommendations (10). The MICs were 2 µg/ml for amoxicillin, 0.25 µg/ml for ceftriaxone, 4 µg/ml for imipenem, 0.5 µg/ml for amikacin, 0.75 µg/ml for ciprofloxacin, and 0.25 µg/ml for cotrimoxazole.
Further identification of the isolate was done by 16S rRNA gene sequence analysis. DNA of a single colony was extracted by using the Fast-prep DNA extraction kit and the Fast-prep DNA device as described by the supplier (Bio 101 Inc., La Jolla, Calif.) (5). The 16S rRNA gene was amplified by using the primers FD1 (5'AGAGTTTGATCCTGGCTGAG 3') and RP2 (5'ACGGCTACCTTGTTACGACTT 3'). The PCRs were performed with a Perkin-Elmer 9600 thermocycler under the following conditions: after an initial denaturation step (95°C for 2 min), a three-step cycle of 94°C for 30 s, 50°C for 30 s, and 72°C for 1 min was repeated 35 times. The sequence determination was performed as previously described (3, 4). The partial 1,377-bp sequence was aligned and compared with all eubacterial 16S ribosomal DNA (rDNA) gene sequences available in the GenBank and EMBL databases by using the multisequence advanced BLAST National Center for Biotechnology Information comparison software (2). This sequence shared 99.9% similarity with that of Aeromonas popoffii LMG 317541 (GenBank accession number AJ224308) (6, 7). After initial alignment with CLUSTAL W (14), neighbor-joining analysis was performed by using PAUP 4.0b1 software (Sinauer, Sunderland, Mass.). Figure 1 shows the dendrogram we obtained. V. parahaemolyticus was the most closely related Vibrio species and was used as an outgroup. Our isolate, strain 1, is close to A. popoffii strain LMG 17543 and belongs to a cluster encompassing A. popoffii strains LMG 317543 and LMG 17542. The most closely related species is Aeromonas encheleia, clustering with Aeromonas salmonicida subsp. masoucida (99% similarity). The third cluster is formed by Aeromonas veronii biotype sobria, Aeromonas eucrenophila, and Aeromonas bestiarum. The farthest Aeromonas species is A. hydrophila.
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FIG. 1. The dendrogram was obtained with 16S rDNA sequences. V. parahaemolyticus was used as an outgroup. Strain 1 is the strain from our patient.
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Classification of the genus Aeromonas has changed continuously over the last decade, with the description of new species and the reclassification of known species. Aeromonas spp. are not frequently involved in urinary tract infections. However, in 1998, Hsueh et al. reported isolation of A. veronii biotype veronii, responsible for urinary tract infection in a 69-year-old male patient suffering from diabetes mellitus and chronic hepatitis. The urinary tract infection was also related to an indwelling device (8). The Aeromonas species mostly implicated in human infections are A. hydrophila, A. caviae, and A. veronii biotype sobria (1).
In 1997, Huys and colleagues described a new species, A. popoffii, isolated from Flemish drinking water production plants and Scottish drinking water supplies (9). Although the clinical origin of some A. popoffii isolates was noted by Huys et al. in 1997, there has been no clinical description of human A. popoffii infection.
The niche of A. popoffii is probably freshwater. However, this bacterium is able to produce some virulence factors, conferring a pathogenic role. These genes were present in all A. popoffii strains studied by Soler et al. (11, 12). For the isolate described here, we demonstrated the presence of genes coding for aerolysin/hemolysin and serine protease. These facts suggest that this isolate was neither a contaminant nor a simple colonization. This description could be relevant for infectious disease consulting.
The 16S rDNA sequences offer a reliable and straightforward tool for identification of A. popoffii strains (13), and routine use of this method should increase our knowledge regarding the clinical spectrum of A. popoffii infections in humans.
Nucleotide sequence accession number. The partial 1,377-bp sequence of the A. popoffii strain isolated in this study has been submitted to GenBank under accession number AY534350.
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