Osteomyelitis caused by Burkholderia pseudomallei: relapse six years after pulmonary infection.

BACKGROUND: Burkholderia pseudomallei is highly endemic in Southeast Asia, whereas in Europe usually only few imported cases of melioidosis occur. CASE REPORT: In 2006, a 52-year-old male patient had been admitted to hospital with pneumonia after returning from a trip to Thailand. A blood culture isolate had been identified as Pseudomonas fluorescens and the patient had been treated with Piperacillin according to the antibiogram. Six years later the patient developed osteomyelitis of the leg and Burkholderia pseudomallei was identified as the causative agent. CONCLUSIONS: Misidentification of the cultural isolate in 2006 had led to inadequate therapy and to an unusually late relapse of melioidosis six years later.

Evaluation of the Merlin MICRONAUT system for rapid direct susceptibility testing of gram-positive cocci and gram-negative bacilli from positive blood cultures.

Bloodstream infections are life-threatening conditions which require the timely initiation of appropriate antimicrobial therapy. We evaluated the automated Merlin MICRONAUT system for rapid direct microtiter broth antimicrobial susceptibility testing (AST) of gram-positive cocci and gram-negative bacilli from BACTEC 9240 bottles with positive blood cultures in comparison to the standard method for the Merlin MICRONAUT system. This prospective study was conducted under routine working conditions during a 9-month period. Altogether, 504 isolates from 409 patients and 11,819 organism-antibiotic combinations were evaluated for comparison of direct and standard AST methods. For gram-negative bacilli, direct and standard AST of 110 isolates was evaluated and MIC agreement was found for 98.1% of 2,637 organism-antibiotic combinations. Category (susceptible, intermediate susceptible, resistant [SIR]) agreement was found for 99.0%, with results for 0.04% of combinations showing very major errors, those for 0.2% showing major errors, and those for 0.8% showing minor errors. For gram-positive cocci, 373 isolates were evaluated and MIC agreement was found for 95.6% of 8,951 organism-antibiotic combinations. SIR agreement was found for 98.8%, with results for 0.3% of combinations showing very major errors, those for 0.4% showing major errors, and those for 0.5% showing minor errors. Although the number of tested isolates was limited (n = 33), direct AST of streptococci was performed for the first time, yielding promising results with SIR agreement for 98.6% of 363 organism-antibiotic combinations. In conclusion, direct AST of gram-negative bacilli and gram-positive cocci from positive blood cultures with the MICRONAUT system is a reliable technique that allows for the omission of repeat testing of subcultured isolates. Thereby, it reduces the time to results of blood culture testing and may have a positive impact on patient care.

The response regulator LetA regulates the stationary-phase stress response in Legionella pneumophila and is required for efficient infection of Acanthamoeba castellanii.

In order to identify a potential regulator of virulence gene expression in Legionella pneumophila, the L. pneumophila homologue of the response regulator GacA, LetA, was identified and cloned, facilitating the generation of a L. pneumophila letA insertion mutant. The L. pneumophila letA insertion mutant was more sensitive to oxidative and acid stress than the wild-type. The letA mutant exhibited reduced infectivity and was defective for intracellular growth within Acanthamoeba castellanii. Transcription of the rpoS and dotA genes was reduced in the letA mutant. Our data indicate that the response regulator LetA functions as a regulator of the stationary-phase stress response in L. pneumophila and is required for efficient replication within A. castellanii.