A simple scoring system to differentiate between relapse and re-infection in patients with recurrent melioidosis

BACKGROUND

Melioidosis is an important cause of morbidity and mortality in East Asia. Recurrent melioidosis occurs in around 10% of patients following treatment either because of relapse with the same strain or re-infection with a new strain of Burkholderia pseudomallei. Distinguishing between the two is important but requires bacterial genotyping. The aim of this study was to develop a simple scoring system to distinguish re-infection from relapse.

METHODS

In a prospective study of 2,804 consecutive adult patients with melioidosis presenting to Sappasithiprasong Hospital, NE Thailand, between 1986 and 2005, there were 141 patients with recurrent melioidosis with paired strains available for genotyping. Of these, 92 patients had relapse and 49 patients had re-infection. Variables associated with relapse or re-infection were identified by multivariable logistic regression and used to develop a predictive model. Performance of the scoring system was quantified with respect to discrimination (area under receiver operating characteristic curves, AUC) and categorization (graphically). Bootstrap resampling was used to internally validate the predictors and adjust for over-optimism.

FINDINGS

Duration of oral antimicrobial treatment, interval between the primary episode and recurrence, season, and renal function at recurrence were independent predictors of relapse or re-infection. A score of < 5 correctly identified relapse in 76 of 89 patients (85%), whereas a score > or = 5 correctly identified re-infection in 36 of 52 patients (69%). The scoring index had good discriminative power, with a bootstrap bias-corrected AUC of 0.80 (95%CI: 0.73-0.87).

CONCLUSIONS

A simple scoring index to predict the cause of recurrent melioidosis has been developed to provide important bedside information where rapid bacterial genotyping is unavailable.

Simultaneous infection with more than one strain of Burkholderia pseudomallei is uncommon in human melioidosis

A prospective study was performed to determine the rate at which patients with melioidosis are infected with more than one strain of Burkholderia pseudomallei. Genotyping of 2,058 bacterial colonies isolated from 215 samples taken from 133 patients demonstrated that mixed infection is uncommon (2/133 cases [1.5%; 95% confidence interval, 0.2 to 5.3%]).

Identification of clinical isolates of Leptospira spp by pulsed field gel-electrophoresis and microscopic agglutination test

Twenty-five clinical isolates of Leptospira spp were characterized by microscopic agglutination test (MAT) and pulsed field gel-electrophoresis (PFGE) in comparison with 23 reference Leptospira serovars and with the saprophytic L. biflexa serovar Patoc. PFGE DNA profiling was more specific and reliable than MAT.

Comparison of leptospiral serovars identification by serology and cultivation in northeastern region, Thailand

Blood from patients suspected of leptospirosis 148 specimens were cultured for leptospira. Twenty two specimens were positive (15%). The isolated leptospira were tested against the 24 serovars of standard antisera by Microscopic Agglutination Test (MAT). It was found that all 22 leptospira isolates reacted strongly against L. autumnalis, except 1 isolate that also reacted against serovar djasiman. The patient's sera were collected from only 14 cases. When the sera of the 14 patients were tested with the 24 reference serovars by MAT it was found that sera reacted the most against L. australis and in decreasing order against L. bratislava, L. autumnalis, L. rachmati, L. copenhageni, L. javanica. There had some cross reactions against several serovars in a single patient. The present study showed inconsistency between culture results and serum assays. Since sera showed cross reactivities against several serovars, it was not possible to determine which serovar was etiologic. Therefore, the isolation of leptospira though time consuming is specific in the identification of the serovar.