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Journal of Clinical Microbiology, February 2007, p. 680-681, Vol. 45, No. 2
0095-1137/07/$08.00+0     doi:10.1128/JCM.01974-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

LETTER TO THE EDITOR

Recurrent Melioidosis: Possible Role of Infection with Multiple Strains of Burkholderia pseudomallei

	LETTER

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Eighteen patients with culture-positive melioidosis seen in Ubon Ratchathani, northeastern Thailand, were studied. Fourteen patients yielded the organism from blood, three presented with localized abscesses with no systemic spread, and one had a urinary tract infection. Sets of 10 to 40 colonies (dependent on the total number of colonies per plate) were selected from primary culture plates of specimens from multiple body sites or from subculture of blood culture broths. Isolates were assigned to a BamHI ribotype pattern, and pulsed-field gel electrophoresis (PFGE) of XbaI DNA digests was used to discriminate further within a ribotype (4). Strains were then allocated a ribotype number or PFGE letter as part of a larger study (3). This showed that 13 of 18 patients were infected with a single strain. In contrast, five patients harbored more than one genotype (Table 1). Four patients had two distinct genotypes detected, while one (A/C 383) had three. Different genotypes were detected both within a single specimen and from the same patient in samples collected on different days. Figure 1 illustrates the DNA profiles of the isolates from patient U1128. All of the 10 colonies from blood cultures were homogeneous, and the same strain was one of two recovered from a swab of a toe wound in this patient.

View larger version (66K): [in this window] [in a new window]   FIG. 1. (A) BamHI ribotype patterns of B. pseudomallei isolates. Lanes 1 and 4, toe wound; lanes 2, 3, and 5, blood. (B) XbaI restriction patterns obtained by PFGE.

Infection with B. pseudomallei is thought to result from exposure to organisms in the environment. Relatively little is known about the occurrence of different genotypes of B. pseudomallei in the environment, but it is not unreasonable to propose that several different strains may coexist within the complex ecosystem represented by paddy field mud, for example. If so, then concurrent infection with more than one strain might thus be expected to occur on occasion. Infection with multiple strains of the same species is not unknown and was previously described in melioidosis by Sexton et al. (2), who reported the presence of two different ribotypes at different body sites of a single patient. The fact that the proportion of cases of recurrent melioidosis caused by strains with a genotype different from that of the primary isolate increases as the time between episodes increases, as reported by Maharjan et al. (1), does indeed support their suggestion that such cases represent reinfection rather than relapse. However, the finding here that 27% of patients harbored different strains concurrently accords with the frequency of reinfection (25%) reported by Maharjan et al. (1) and might provide an alternative explanation for the appearance of apparently new strains over time.

	FOOTNOTES

 
Published ahead of print on 20 December 2006.

	REFERENCES

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1. Maharjan, B., N. Chantratita, M. Vesaratchavest, A. Cheng, V. Wuthiekanun, W. Chierakul, W. Chaowagul, N. P. Day, and S. J. Peacock. 2005. Recurrent melioidosis in patients in northeast Thailand is frequently due to reinfection rather than relapse. J. Clin. Microbiol. 43:6032-6034.[Abstract/Free Full Text]
2. Sexton, M. M., L. A. Goebel, A. J. Godfrey, W. Choawagul, N. J. White, and D. E. Woods. 1993. Ribotype analysis of Pseudomonas pseudomallei isolates. J. Clin. Microbiol. 31:238-243.[Abstract/Free Full Text]
3. Trakulsomboon, S. 1995. Strain identification and clinical epidemiology of Burkholderia pseudomallei. Ph.D. thesis. University of London, London, United Kingdom.
4. Vadivelu, J., S. D. Puthucheary, A. Mifsud, B. S. Drasar, D. A. Dance, and T. L. Pitt. 1997. Ribotyping and DNA macrorestriction analysis of isolates of Burkholderia pseudomallei from cases of melioidosis in Malaysia. Trans. R. Soc. Trop. Med. Hyg. 91:358-360.[CrossRef][Medline]

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This Article Full Text (PDF) Other Versions of this Article: JCM.01974-06v1 45/2/680    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Pitt, T. L. Articles by Dance, D. A. B. Search for Related Content PubMed PubMed Citation Articles by Pitt, T. L. Articles by Dance, D. A. B.