Relationship between indole production and differentiation of Klebsiella species: indole-positive and -negative isolates of Klebsiella determined to be clonal

Abstract

Klebsiellae are an important cause of nosocomial infections. The two clinically relevant species, Klebsiella pneumoniae and KlebsieUla oxytoca, are differentiated by the ability to produce indole from tryptophan, K. oxytoca being indole positive. We report here the detailed biochemical and molecular analysis of two isolates of KiebsieUla, cultured from the same urine specimen, that differed only in their ability to produce indole. The two isolates were identical as determined by ribotyping and pulsed-field gel electrophoresis, and they differed from 10 epidemiologically unrelated strains. Probing with the Escherichia coli tryptophanase operon, tna, revealed seven restriction fragment length polymorphisms (RFLP) among the 12 strains. The two index strains had identical RFLP; no single RFLP could account for all of the indole-positive or-negative strains. Thus, the identification of epidemiologically related strains ofKlebsieUla differing only in indole production may warrant further examination to determine whether the strains are clonal. Klebsiellae are an important cause of nosocomial infections and have been responsible for epidemic infections, particularly in intensive care units (6, 11). In this context, the accurate identification of organisms is critical in defining nosocomial spread among patients. Within the genus Klebsiella, Klebsiella pneumoniae and Klebsiella oxytoca account for the majority of clinical isolates, differing biochemically in that K oxytoca is able to produce indole from tryptophan. We describe here the analysis of two isolates of Klebsiella that differed phenotypically only in their ability to produce indole from tryptophan. The genetic relationship between the isolates was determined by pulsed-field gel electrophoresis (PFGE) and Southern blot analysis after probing with the Escherichia coli ribosomal operon (ribotype). In addition, polymorphisms of the tryptophanase locus were evaluated by probing with the E. coli tryptophanase operon (4).

Epidemiological study by pulsed-field gel electrophoresis of an outbreak of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae in a geriatric hospital

“…PFGE has recently been shown to be useful for the study of genomic relatedness among non-ESBIa-producing K pneumoniae strains (12). Results of the present study confirm that it is also an excellent tool for typing ESBIaproducing K pneumoniae strains.…”

SIDEROPHORE PRODUCTION, SERUM RESISTANCE, HEMOLYTIC ACTIVITY AND EXTENDED‐SPECTRUM β‐LACTAMASE‐PRODUCING KLEBSIELLA SPECIES ISOLATED FROM MILK AND MILK PRODUCTS

“…Klebsiella pneumoniae was isolated from mastitic cows, particularly from those kept in the bedding of wood products (Carter 1995). In humans, K. pneumoniae is an important cause of nosocomial infections, such as pneumonia, septicemia, and urinary tract and soft‐tissue infections (Maslow et al . 1993; Podschun and Ullmann 1998).…”

“…1993; Podschun and Ullmann 1998). The indole‐producing Klebsiella oxytoca (Maslow et al . 1993) was reported as an enterotoxigenic microorganism and causes an antibiotic‐associated hemorrhagic colitis (Minami et al .…”

Molecular epidemiology of Klebsiella pneumoniae strains that produce SHV-4 beta-lactamase and which were isolated in 14 French hospitals

“…Similar observations were reported by de Champs et al (10) for K pneumoniae producing CAZ-5 ,B-lactamase (an enzyme very similar to SHV-4) in another French hospital. The diffusion of TEM-3 ,-lactamase is mainly the result of the dissemination of plasmids (7,10,19,23,29,34). In contrast, the interhospital diffusion of the SHV-4 P-lactamase seems to be due to the propagation of a single bacterial strain.…”