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Journal of Clinical Microbiology, July 2008, p. 2435-2437, Vol. 46, No. 7
0095-1137/08/$08.00+0 doi:10.1128/JCM.00337-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Division of Infectious Disease, Department of Medical Microbiology, McGill University Health Center, Montreal, Quebec, Canada,1 Laboratoire de Santé Publique du Québec, Institut National de Santé Publique du Québec, Sainte-Anne-de-Bellevue, Québec, Canada,2 Department of Medical Microbiology, Hôpital du Haut Richelieu, Saint-Jean-sur-Richelieu, Québec, Canada,3 Department of Pediatrics, Children's and Women's Health Centre of British Columbia, Vancouver, British Columbia, Canada,4 Department of Pathology and Laboratory Medicine, Children's and Women's Health Centre of British Columbia, Vancouver, British Columbia, Canada,5 Special Bacteriology Section, National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada6
Received 18 February 2008/ Returned for modification 23 April 2008/ Accepted 15 May 2008
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During 2006 and 2007, strains of A. altamirensis were isolated from three different patients in two Canadian provinces. The first isolate was cultured from a contact lens and the lens cleansing solution from a patient with keratitis (case 1). The second isolate was recovered from a corneal culture from a patient who suffered a penetrating eye injury while sharpening a metal tool. Despite treatment with trifluridine, tobramycin-dexamethasone, and fluconazole eye drops, the infection progressed to form a dendritic corneal ulcer with perforation. The culture of corneal scrapings subsequently revealed Alternaria sp. and a gram-negative bacillus (case 2). The third isolate was recovered from the sputum of a cystic fibrosis patient who had recently received a 2-week course of tobramycin and piperacillin-tazobactam to treat the exacerbation of the respiratory condition by Staphylococcus aureus and Pseudomonas aeruginosa. Upon discharge, a regimen of ciprofloxacin for 3 weeks and daily inhaled colistin was instituted. Surveillance culture 3 weeks later yielded 2+ growth of S. aureus (as assessed using a scoring system in which 0 represents no growth, 1+ represents minimal growth, 2+ represents moderate growth, 3+ represents extensive growth, and 4+ represents maximal growth), as well as one colony of a gram-negative bacillus. The organism was left untreated, and the patient remained well (case 3).
The identification of patient strains at the primary-care level by using commercial identification kits (API 20NE and Vitek [both from bioMérieux, Inc.] and RapID NF [Remel]) gave rise to conflicting results. API 20NE strip identifications included Ochrobactrum anthropi and Sphingomonas paucimobilis, or the test could not provide adequate identification. The RapID NF strip (Remel) showed 99.9% agreement with the identification of Shewanella putrefaciens. The Vitek identification system (bioMérieux, Inc) could not provide adequate identification. Such ambiguities prompted clinicians to forward the isolates to a reference center for further characterization.
The three strains were identified by nearly full 16S rRNA gene sequencing in the Laboratoire de Santé Publique du Québec, Sainte-Anne-de-Bellevue, and the National Microbiology Laboratory, Winnipeg, Canada (1, 2). The strains were designated NML 070723 (the case 1 isolate), NML 070722 (the case 2 isolate), and NML 060898 (the case 3 isolate). Alignment was done using Clustal X (11), and phylogenetic relationships were inferred using the neighbor-joining method in MEGA 4.0 (12). The strains were found to have >99% identity to one another and 99.4% or greater identity to the A. altamirensis type strain (GenBank accession no. DQ372921) (Fig. 1). Pairwise analysis of 16S rRNA gene sequences from recently described species A. frigidaquae, which is closely related to, but discernible from, A. altamirensis (10), demonstrated 98.5% identity to the clinical isolates as well as the type strain of A. altamirensis (Fig. 1).
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FIG. 1. Phylogenetic relationships inferred using the neighbor-joining method with 16S rRNA gene sequence data for species in the genus Aurantimonas and clinically derived isolates. The scale represents percentages of substitutions. Escherichia coli was used as a distant outlier, and Fulvimarina pegali was used as a family-level outlier.
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TABLE 1. API CH50 substrates which were reactive with clinically derived Aurantimonas strains and the type strain of A. altamirensisa
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8c (2%), C17:1
6c (2%), C17:0 (3%), C18:1
7c (71%), C18:0 (2%), and C19:0 cyc
8c (6%), with trace to small amounts of C15:0, C18:1
9c, 2-OH C18:1, 3-OH C18:0, and C20:1
7c and summed features 2, 3, and 5. These data were deemed to be highly consistent with those for members of the genus Aurantimonas (9, 10, 13). Antimicrobial susceptibilities were determined by broth microdilution using Sensititre GN2F panels and cation-adjusted Mueller-Hinton broth (Nova Century Scientific Inc., Burlington, ON) according to the instructions of the panel manufacturer (Trek Diagnostics Inc.) and the CLSI guidelines for Pseudomonas aeruginosa and other non-Enterobacteriaceae (6). Antibiotic susceptibilities of the three strains are shown in Table 2.
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TABLE 2. Results of antimicrobial susceptibility testing for A. altamirensisa
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Because the recovery of this organism from humans has not been described previously, the clinical contribution to disease appears to be variable. It is possible that the organism was simply a contaminant derived from environmental and/or water sources (e.g., lens cleansing solution, medicated ocular solutions, or nebulized aerosols and related equipment). Contact lens cases can harbor organisms, such as gram-negative bacilli, that are not the causative organism of keratitis (5). Aerosols and nebulizing equipment can also act as reservoirs for microorganisms (4). In case 1, the simultaneous isolation from two related sources, in the absence of other organisms, from a patient with clinical disease is suggestive of an etiological role. In case 2, the concomitant recovery of Alternaria (a known ocular pathogen) from the corneal scrapings obscures the clinical relevance of the isolated Aurantimonas. Case 3 supports the possibility that the organism has no or low-level pathogenicity in certain clinical settings. These three cases illustrate the spectrum of clinical significance of A. altamirensis and provide guidance to clinical microbiologists on its accurate identification. Further studies are required to elucidate its clinical relevance.
This report also highlights the difficulty of correctly identifying this organism by phenotypically based laboratory methods alone. This agent gave rise to ambiguous identifications depending on which rapid identification method was used, and in such situations, microbiologists and clinicians should consider further characterization by 16S rRNA sequencing.
Nucleotide sequence accession numbers. Sequences obtained for NML 070723 (the case 1 isolate), NML 070722 (the case 2 isolate), and NML 060898 (the case 3 isolate) have been deposited in GenBank under accession no. EU442517, EU442518, and EF595814, respectively.
Published ahead of print on 21 May 2008. ![]()
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