A novel intracellular pathogen morphologically similar to the ehrlichiae has been isolated in cell culture and identified as the cause of an epizootic disease of salmonid fish. Like the ehrlichiae, the salmonid pathogen, designated strain LF-89, replicates within membrane-bound cytoplasmic vacuoles in host cells. This agent is the first with characteristics of this type to be isolated from a fish. Analysis of the LF-89 16s rRNA indicated that, unlike the ehrlichiae, LF-89 is a gamma proteobacterium distantly related to Coxiella burnetii and perhaps WoZbuchiu persica. A new genus and species (Piscin'ckettsia sahonis gen. nov., sp. nov.) are proposed for this organism, with ATCC(R) VR 1361 as the type strain.

Variegated cutworms were exposed to bean plants in microcosms sprayed with pBR322-carrying strains of Enterobacter cloacae, Klebsiella planticola, and Erwinia herbicola. The three bacterial species exhibited differential survival on leaves, in soil, and in guts and fecal pellets (frass) of the insects. High numbers of Enterobacter cloacae(pBR322) were detected in all samples, while the other species were unable to establish residence in the insect. To assess the impact of this colonization on site-to-site transport of microorganisms, larvae were fed plants that had been sprayed with the bacteria and then were transferred to uninoculated plants. Cutworms were efficient carriers of Enterobacter cloacae(pBR322), as indicated by its rapid appearance on uninoculated leaves and continued persistence in the insects for 3 days after transfer. Few Erwinia herbicola(pBR322) and K. planticola(pBR322) were obtained from larvae after transfer, although up to 103 CFU/g were detected in soil and on plants. Differences in bacterial survival and growth were confirmed by incubating frass overnight and observing the change in population numbers. The proportion of total samples showing at least a 25-fold increase during incubation was 68% for Enterobacter cloacae(pBR322), 39% for K. planticola(pBR322), and 0% for Erwinia herbicola(pBR322). Our results emphasize the role that cutworms and possibly other insects have in persistence and growth of microorganisms in the environment.

Transconjugants arising from transfer of plasmid R388::Tn1721 between donor and recipient strains of Enterobacter cloacae were detected in samples from the digestive tracts and fecal pellets of variegated cutworms (Peridroma saucia).

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