Enterobacter sakazakii: A New Species of "Enterobacteriaceae" Isolated from Clinical Specimens

Abstract

Enterobacter sakazakii is the name proposed for the organism previously known as "yellow-pigmented Enterobacter cloacae." The type strain (holotype) of this species is ATCC 29544. The proposed change in the classification of this organism is based on differences between E. cloacae and E. sakazakii in deoxyribonucleic acid (DNA) -DNA hybridization, biochemical reactions, pigment production, and antibiotic susceptibility. By DNA hybridization, E. sakazakii was about 50% related to E. cloacae, Citrobacter diversus ("Citrobacter intermedius" biotype b), and "Citro bacter amalonaticus" ("Citro bacter intermedius" biotype a). The new species was placed in Enterobacter rather than Citrobacter because of its closer phenotypic and DNA similarity to E. cloacae, the type species of the genus Enterobacter, and because it was only 41% related by DNA hybridization to Citrobacter freundii, the type species of Citrobacter. E. sakazakii had biochemical reactions very similar to those of E. cloacae but was D-sorbitol negative and positive for extracellular deoxyribonuclease at 2 to 7 days and produced yellow-pigmented colonies. E. sakazakii had larger zones of inhibition around ampicillin and cephalothin antibiotic disks, which also helps to differentiate it from E. cloacae. E. sakazakii grew on the nonselective (but differential) plating media commonly used in enteric bacteriology, but its plating efficiency was reduced on more inhibitory enteric plating media. It has been isolated from human clinical specimens such as sputum, feces, and wounds, where it is probably only a colonizer and not clinically sigruficant. However, it is also a documented, although rare, cause of neonatal meningitis. Other sources have included food, a physician's stethoscope, and an uninoculated blood culture bottle.As new knowledge accumulates, changes in the classification of members of the family "Entwo bacteriaceae" (scientific names in quotation marks were not included in the Approved Lists "241) become necessary (4,8,9, 12, 19,21,23). A few of these changes have involved consolidation of organisms previously thought to be distinct species. The four Shigella species and Escherichia coli although phenotypically distinct, are closely related by other criteria and could be considered as belonging to the m e species (7). Similarly, Klebsiella ozaenae and Klebsiella rhinoscleromatis are comprised of host-adapted strains p patho-bio-sero-geogroups") which belong in the same species with KlebsielZapneumoniae (11). Other changes have involved "splitting" rather than "lumping." New species previously thought to be biogroups (biotypes or biovars) within a recognized species have been proposed recently. Examples include Klebsiella oxytoca, previously thought to be an indole-positive biogroup of K. pneumoniae (19); Proteus tThe participants and their affiliations are listed in the Acknowledgments at the end of this paper.

Plasmid-Encoded MCP Is Involved in Virulence, Motility, and Biofilm Formation of Cronobacter sakazakii ATCC 29544

“…3C). Taken together, these results suggest that the putative MCP plays a crucial role in the pathogenesis of C. sakazakii ATCC 29544, which was originally isolated from throat culture of a patient with whooping cough (2).…”

hfq Plays Important Roles in Virulence and Stress Adaptation in Cronobacter sakazakii ATCC 29544

“…Based on the original 16 biogroups of Farmer et al, E. sakazakii has been reclassified into several Cronobacter spp. according to genotypic and phenotypic evaluations (1)(2)(3)(4). Cronobacter spp.…”

A Kluyvera cryocrescens strain from a gall-bladder infection

“…At the m o m e n t , we know that K l u v v e r a strains are encountered, though infrequently, in clinical specimens f r o m u p p e r respiratory tract (mixed cultures) and in urine, blood, and. stool samples (1,4,5).…”

“…The Api 20E numerical profile (1344153) was not mentioned in the Api 20E analytical catalogue. A statistical analysis of the results was therefore performed, as suggested by Lapage et al (7), using as a data base the positivity percentages reported by J.J. F a r m e r I I I et al (5). The identification likelihood (%id.)…”