Achromobacter buckle infection diagnosed by a 16S rDNA clone library analysis: a case report

Abstract

Background: In clinical settings, bacterial infections are usually diagnosed by isolation of colonies after laboratory cultivation followed by species identification with biochemical tests. However, biochemical tests result in misidentification due to similar phenotypes of closely related species. In such cases, 16S rDNA sequence analysis is useful. Herein, we report the first case of an Achromobacter-associated buckle infection that was diagnosed by 16S rDNA sequence analysis. This report highlights the significance of Achromobacter spp. in device-related ophthalmic infections.

Case presentation: A 56-year-old woman, who had received buckling surgery using a silicone solid tire for retinal detachment eighteen years prior to this study, presented purulent eye discharge and conjunctival hyperemia in her right eye. Buckle infection was suspected and the buckle material was removed. Isolates from cultures of preoperative discharge and from deposits on the operatively removed buckle material were initially identified as Alcaligenes and Corynebacterium species. However, sequence analysis of a 16S rDNA clone library using the DNA extracted from the deposits on the buckle material demonstrated that all of the 16S rDNA sequences most closely matched those of Achromobacter spp. We concluded that the initial misdiagnosis of this case as an Alcaligenes buckle infection was due to the unreliability of the biochemical test in discriminating Achromobacter and Alcaligenes species due to their close taxonomic positions and similar phenotypes. Corynebacterium species were found to be contaminants from the ocular surface.

Conclusions: Achromobacter spp. should be recognized as causative agents for device-related ophthalmic infections. Molecular species identification by 16S rDNA sequence analysis should be combined with conventional cultivation techniques to investigate the significance of Achromobacter spp. in ophthalmic infections.

Figure 1

Pre-operative anterior segments photograph. The patient is looking downward. Conjunctival fistula in the upper quadrants and large yellowish conjunctival follicles (black arrows) around the exposed buckle material (white arrowhead) can be observed.

Figure 2

Pictures of the buckle material. (A) Buckle material immediately after the extraction. Many yellowish-white deposits (arrows) on the surface of the buckle material can be observed. (B) Ruthenium red staining. Deposits were stained red by ruthenium red for scanning electron microscopy.

Figure 3

Phylogenetic relationship between the isolate from buckle material and other members of the family Alcaligenaceae . Only the most predominant ST1 sequence (indicated by red and asterisks) was analysed. The tree was constructed using the neighbour-joining algorithm. Numbers at nodes are bootstrap percentages based on 1,000 replications; only values >70% are shown. Bar, 0.01 substitutions per nucleotide position.

Figure 4

Scanning electron microscopic images of the buckle material. (A) Low magnification. Deposits attached after fixation by glutaraldehyde. (B) High magnification. Numerous rod-shaped bacteria surrounded by biofilm-like material are observed.