ena-STUDY-National Institute of Public Health-20-11-2014-15:51:55:524-1618
Klebsiella variicola was very recently described as new bacterial species and is very closely related to Klebsiella pneumoniae.
The genus Klebsiella belongs to the Enterobacteriaceae family and comprises Gram-negative opportunistic non-motile pathogens with a mucoid aspect. The species that make up the genus Klebsiella are ubiquitous in nature; they are present in three common habitats: i) the environment, where they can be found in water, soil and plants; ii) the mucous surfaces of mammals, and iii) in symbiosis with insects. In plants, they are endophytic and diazotrophic bacteria; in other words, they associate with plants by colonizing their internal tissues and providing enough nitrogen so that the hosts mitigate their nitrogen deficiency. In mammals, these bacteria colonize the upper respiratory tract as well as the gastrointestinal tract. Most Klebsiella-related infections are associated to hospitalization. These pathogens are the causative agents of 7 to 10% of all the nosocomial infections reported in Europe, Latin-America and North America. K. variicola was described as a new bacterial species in 2004, this proposition was based on phylogenetic analysis of six housekeeping (rpoB, gyrA, nifH, infB, phoE and mdh) genes and DNA-DNA hybridizations. This work identified that 8% of the K. pneumoniae isolates corresponded to K. variicola, with both clinical isolates and environmental isolates. Subsequently, multidrug resistance phenotypes and extended-spectrum ß-lactamase-producers (ESBL) were identified for K. variicola in an intra-hospital outbreak in a pediatric hospital in Mexico. Additionally, this species has been recently reported as a symbiotic nitrogen-fixing bacteria, frequently isolated from the fungus gardens of leaf-cutter ant colonies collected in Central and South America. To date, the correct identification of the Klebsiella species has not been easily achieved in microbiological laboratories, since several species of this genus share similar biochemical profiles. Commercial kits, both manual and automated, do not include some of the organisms in their databases or the necessary substrates to differentiate species. Some studies have been expressly designed to identify biochemical markers that are able to differentiate K. variicola from K. pneumoniae. For instance the inability to ferment adonitol, which was one of the characteristics used by Rosenblueth et al. A recent study rejected this proposal since it was determined that this biochemical characteristic is variable among different isolates. Currently, the differentiation of K. variicola and K. pneumoniae by means of biochemical tests is not possible. To date, K. variicola is one of the species of the genus Klebsiella that is not even included in commercial kits and it has been described in several environments.
The genus Klebsiella belongs to the Enterobacteriaceae family and comprises Gram-negative opportunistic non-motile pathogens with a mucoid aspect. The species that make up the genus Klebsiella are ubiquitous in nature; they are present in three common habitats: i) the environment, where they can be found in water, soil and plants; ii) the mucous surfaces of mammals, and iii) in symbiosis with insects. In plants, they are endophytic and diazotrophic bacteria; in other words, they associate with plants by colonizing their internal tissues and providing enough nitrogen so that the hosts mitigate their nitrogen deficiency. In mammals, these bacteria colonize the upper respiratory tract as well as the gastrointestinal tract. Most Klebsiella-related infections are associated to hospitalization. These pathogens are the causative agents of 7 to 10% of all the nosocomial infections reported in Europe, Latin-America and North America. K. variicola was described as a new bacterial species in 2004, this proposition was based on phylogenetic analysis of six housekeeping (rpoB, gyrA, nifH, infB, phoE and mdh) genes and DNA-DNA hybridizations. This work identified that 8% of the K. pneumoniae isolates corresponded to K. variicola, with both clinical isolates and environmental isolates. Subsequently, multidrug resistance phenotypes and extended-spectrum ß-lactamase-producers (ESBL) were identified for K. variicola in an intra-hospital outbreak in a pediatric hospital in Mexico. Additionally, this species has been recently reported as a symbiotic nitrogen-fixing bacteria, frequently isolated from the fungus gardens of leaf-cutter ant colonies collected in Central and South America. To date, the correct identification of the Klebsiella species has not been easily achieved in microbiological laboratories, since several species of this genus share similar biochemical profiles. Commercial kits, both manual and automated, do not include some of the organisms in their databases or the necessary substrates to differentiate species. Some studies have been expressly designed to identify biochemical markers that are able to differentiate K. variicola from K. pneumoniae. For instance the inability to ferment adonitol, which was one of the characteristics used by Rosenblueth et al. A recent study rejected this proposal since it was determined that this biochemical characteristic is variable among different isolates. Currently, the differentiation of K. variicola and K. pneumoniae by means of biochemical tests is not possible. To date, K. variicola is one of the species of the genus Klebsiella that is not even included in commercial kits and it has been described in several environments.