Erwinia Species: An Emerging Human Pathogen

Thirty-eight isolates of the genus Erwinia, ordinarily considered a plant pathogen, were obtained during the course of a year from a variety of human clinical sources including blood, bone marrow, spinal fluid and pleura. Identification characteristics included microscopic morphology of short, motile, Gram-negative rods with round ends, yellow colonial pigmentation, presence of colonial spindle-shaped biconvex bodies, aggregation of organisms in elongated spheroidal masses (“symplasmata”), fermentative capability, and lack of lysine and ornithine decarboxylase and arginine dihydrolase activity. Recovered strains proved universally susceptible to gentamicin and neomycin, and were generally resistant to ampicillin, cephalothin, erythromycin, and tetracycline. They were variably susceptible to chloramphenicol and colistin sulfate. Repeated isolation in pure culture from systemic sites, concomitant clinical symptomatology, demonstration of specific agglutinins in an infected patient against his own Erwinia isolate, responses in a number of patients to therapy with antibiotics to which the isolates proved susceptible in vitro, and experimental pathogenicity in mice all provide evidence for the pathogenic significance of Erwinia species for humans.