Pulsed-field gel electrophoresis for the analysis of Listeria monocytogenes infection clusters after kidney transplantation

Listeria monocytogenes causes a rare, life-threatening infection in recipie nts of transplanted organs. We used cultures of blood and cerebrospinal flu id to characterize isolates and to distinguish cases in dusters from what m ight have been sporadic cases. From December 1994 to November 1995, six sys temic L.monocytogens infections occurred at our transportation unit. We con firmed the clinical diagnosis with blood and cerebrospinal fluid cultures a nd characterized the isolates retrospectively with pulsed-field gel electro phoresis (PFGE), phage-typing, and serotyping. We also performed an environ mental investigation (food, drug, and stool). We took samples after the fir st two L. monocytogenes infections and then after cases three and four occu rred. All patients recovered completely, and no graft was lost. Four patien ts had identical or genetically related L. monocytogenes isolates in PFGE ( type A) and serotyping (type 1/2b). The other two had PFGE type B and G. L. monocytogens was not detected in food or drug samples from patients on the renal- transplantation ward or in stool samples from the ward staff. It wa s concluded that PFGE allows sporadic cases and cluster cases of L. monocyt ogenes infection to be distinguished.