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Relationships among Pseudomonas pseudomallei isolates from patients with recurrent melioidosis
P M Desmarchelier1, D A Dance, W Chaowagul
1Tropical Health Program, University of Queensland, Brisbane, Australia.
Abstract:
Patients with melioidosis may present with recurrent infections after clinical resolution of their primary illness. Because there has been no satisfactory typing scheme for Pseudomonas pseudomallei, recrudescence could not be distinguished from reinfection. We determined the strain identity of primary and relapse isolates of P. pseudomallei from 25 patients with culture-proven melioidosis to answer whether secondary infections were due to the initial infecting strain or to the acquisition of a new strain. Fifty-four isolates were compared by the patterns of BamHI restriction digests produced after hybridization with a cDNA copy of Escherichia coli rRNA. Twenty-three patients had primary and relapse isolates with identical or highly similar ribotype patterns. The patterns of isolates from two patients were different; the primary and relapse isolates differed by a single fragment for one, and the other had identical primary and first-relapse isolates while the second-relapse isolate was markedly different. The results indicated that recurrent infection probably resulted from endogenous relapse in most of the melioidosis patients studied, although reinfection from an exogenous source was also possible in two cases.
Insights
Recurrent melioidosis infections are often caused by the original Pseudomonas pseudomallei strain relapsing internally. Distinguishing relapse from reinfection is crucial for effective treatment of this serious bacterial disease.
Area of Science:
- Infectious Diseases
- Microbiology
- Genetics
Background:
- Melioidosis, caused by Pseudomonas pseudomallei, can recur after initial treatment.
- Previous typing methods for P. pseudomallei were insufficient to differentiate relapse from reinfection.
Purpose of the Study:
- To determine if recurrent melioidosis is due to the initial infecting strain or a new infection.
- To establish a reliable method for strain typing of P. pseudomallei.
Main Methods:
- Compared BamHI restriction digest patterns of P. pseudomallei isolates from primary and relapse infections.
- Utilized hybridization with an Escherichia coli rRNA cDNA probe for ribotyping.
Main Results:
- Twenty-three of 25 patients showed identical or highly similar ribotype patterns between primary and relapse isolates.
- Two patients had differing patterns, suggesting possible reinfection.
Conclusions:
- Recurrent melioidosis is most often caused by endogenous relapse of the initial P. pseudomallei infection.
- Exogenous reinfection is possible in a minority of cases.