Bacterial infection in patients who have undergone liver transplantation is a major complication of the procedure. Leuconostoc spp. are important pathogenic bacteria in individuals with poor immune function, especially transplant patients. In this report, we describe the case of a 45-yearold Asian male liver transplant recipient who was initially preliminarily diagnosed with infection with Leuconostoc pseudomesenteroides by using the microbial tests of the VITEK 2 system and the aesculin hydrolysis test, and with vancomycin-resistant Enterococcus. Subsequently, the Leuconostoc isolate was identified as Leuconostoc lactis by 16S rRNA gene partial sequencing. In this paper, we discuss our identification of L. lactis based on physiological characteristics and molecular methodology. Accurate identification of these infections is important for the outcome; use of 16S rRNA gene sequence analysis offers a rapid and precise diagnostic approach. Administration of the drug linezolid may be useful for the treatment of both Leuconostoc spp. and vancomycin-resistant Enterococcus infections. We suggest that clinical analysts should use molecular methods in addition to biochemical tests in order to identify Leuconostoc at the species level more accurately.
IntroductionBacterial infection is a major complication after liver transplantation and the incidence is around 48 %. Vancomycin prophylaxis against Gram-positive bacteraemia following transplantation may prevent infection. However, with the increasing use of vancomycin in clinical practice, new vancomycin-resistant pathogenic bacteria are likely to appear.Leuconostoc spp. are Gram-positive, catalase-negative bacteria and are intrinsically resistant to vancomycin (Facklam & Elliott, 1995;Bernaldo de Quiró s et al., 1991). As a consequence of their irregular coccoid morphology, they used to be listed as members of the Streptococcaceae, but are now recognized as Leuconostocaceae and are placed within the order Lactobacillales. These bacteria are found in the environment, e.g. on vegetables and in dairy and other fermented products, but are known to occasionally cause infection in humans. Subsequent to 1985, several infections that resulted from Leuconostoc spp., namely Leuconostoc mesenteroides and Leuconostoc pseudomesenteroides, have been reported (Handwerger et al., 1990;Bernaldo de Quiró s et al., 1991;Dhodapkar & Henry, 1996). Most reported cases were bloodstream infections; however, these bacteria are also a cause of meningitis, pneumonia, endocarditis, pleural empyema, osteomyelitis or urinary tract infections. However, to date, no deaths related to Leuconostoc spp. infection have been reported (Facklam & Elliott, 1995;Bernaldo de Quiró s et al., 1991;Montejo et al., 2000;Espinoza et al., 1997;Giraud et al., 1993;Yamazaki et al., 2009). Some Enterococcus spp. are commensal organisms in the intestine. Furthermore, vancomycin-resistant enterococci (VRE) are recognized as some of the most significant nosocomial pathogens in the world because of their rapid spread, high mor...