Phylogenetic grouping, epidemiological typing, analysis of virulence genes, and antimicrobial susceptibility of Escherichia coli isolated from healthy broilers in Japan.

BACKGROUND: The aim of our study was to investigate the possible etiology of avian colibacillosis by examining Escherichia coli isolates from fecal samples of healthy broilers. FINDINGS: Seventy-eight E. coli isolates from fecal samples of healthy broilers in Japan were subjected to analysis of phylogenetic background, virulence-associated gene profiling, multi-locus sequence typing (MLST), and antimicrobial resistance profiling. Phylogenetic analysis demonstrated that 35 of the 78 isolates belonged to group A, 28 to group B1, one to group B2, and 14 to group D. Virulence-associated genes iutA, iss, cvaC, tsh, iroN, ompT, and hlyF were found in 23 isolates (29.5%), 16 isolates (20.5%), nine isolates (11.5%), five isolates (6.4%), 19 isolates (24.4%), 23 isolates (29.5%), and 22 isolates (28.2%) respectively. Although the genetic diversity of group D isolates was revealed by MLST, the group D isolates harbored iutA (10 isolates, 71.4%), iss (6 isolates, 42.9%), cvaC (5 isolates, 35.7%), tsh (3 isolates, 21.4%), hlyF (9 isolates, 64.3%), iroN (7 isolates, 50.0%), and ompT (9 isolates, 64.3%). CONCLUSIONS: Our results indicated that E. coli isolates inhabiting the intestines of healthy broilers pose a potential risk of causing avian colibacillosis.

Dioctatin A is a strong inhibitor of aflatoxin production by Aspergillus parasiticus.

Dioctatin A (DotA), a metabolite of Streptomyces, is known to be an inhibitor of human dipeptidyl aminopeptidase II. Here, it was found that DotA strongly inhibited aflatoxin production by Aspergillus parasiticus, with an IC50 value of 4.0 microM. The mycelial growth of the fungus was not affected by the addition of DotA at a concentration of 50 microM, but inhibition of conidiation was observed at the same concentration. DotA inhibited production of norsolorinic acid, an early biosynthetic intermediate of aflatoxin, and it strongly reduced the mRNA levels of genes encoding aflatoxin biosynthetic enzymes, and significantly decreased the mRNA level of aflR, which encodes a key regulatory protein for aflatoxin biosynthesis. In addition to these genes, the mRNA level of brlA, which encodes a conidiation-specific transcription factor, was also reduced by the addition of DotA. It was also found that DotA dramatically enhanced kojic acid production by the fungus. Furthermore, DotA inhibited production of sterigmatocystin, which is a toxic aflatoxin biosynthetic intermediate, and it also inhibited conidiation in Aspergillus nidulans. These results indicate that DotA has pleiotropic effects on regulatory mechanisms of fungal secondary metabolite production and differentiation, leading to inhibition of aflatoxin production.

Synthesis and biological activity of sulphostin analogues, novel dipeptidyl peptidase IV inhibitors.

The structure of sulphostin (1), a novel dipeptidyl peptidase IV (DPP-IV) inhibitor, is consisted of three key functional groups, including a characteristic amino(sulfoamino)phosphinyl group, on a piperidine ring. To examine the relationship between its structure and the inhibitory activity against DPP-IV, various analogues were synthesized and their activities were investigated. These results indicated that all of the functional groups on the piperidine ring were crucial to the DPP-IV inhibitory activity of sulphostin, and that the sulfonic acid group, which constructed the amino(sulfoamino)phosphinyl group, contributed to the stability of the compound. Moreover, those functional groups should be adjoined on the piperidine ring for the inhibitory activity. The size of the nitrogen-containing heterocyclic ring including piperidine appeared to scarcely affect the activity. In the present study, the sulfonic acid-deficient five-membered ring analogue 27a showed the strongest inhibitory activity (IC50=11 nM).

First synthesis and determination of the absolute configuration of sulphostin, a novel inhibitor of dipeptidyl peptidase IV.

Sulphostin, a novel dipeptidyl peptidase IV (DPP-IV) inhibitor, was isolated from the culture broth of Streptomyces sp. MK251-43F3. Determination of the absolute configurations of two asymmetric atoms using the natural product was not achieved due to the small amount of the compound obtained. We synthesized four possible stereoisomers of sulphostin from D- or L-ornithine and compared their physicochemical and biological data to naturally isolated sulphostin. As a result, the absolute configurations at C-3 and the phosphorus atom of sulphostin were determined to be S and R, respectively, by X-ray crystallography. Synthetic sulphostin and its C-3 epimer have strong inhibitory activities against DPP-IV, IC50 values of which are 6.0 and 8.9 ng/mL, respectively. Thus it appears that the configuration of the phosphorus atom is primarily responsible for the activity; in contrast, the configuration of C-3 does not appear to affect the activity.