The provision of procalcitonin assay results, along with instructions on their interpretation, to emergency department and hospital-based clinicians did not result in less use of antibiotics than did usual care among patients with suspected lower respiratory tract infection. (Funded by the National Institute of General Medical Sciences; ProACT ClinicalTrials.gov number, NCT02130986 .).

Peptide deformylase (PDF) is an essential bacterial metalloenzyme which deformylates the N-formylmethionine of newly synthesized polypeptides and as such represents a novel target for antibacterial chemotherapy. To identify novel PDF inhibitors, we screened a metalloenzyme inhibitor library and identified an N-formylhydroxylamine derivative, BB-3497, and a related natural hydroxamic acid antibiotic, actinonin, as potent and selective inhibitors of PDF. To elucidate the interactions that contribute to the binding affinity of these inhibitors, we determined the crystal structures of BB-3497 and actinonin bound to Escherichia coli PDF at resolutions of 2.1 and 1.75 Å, respectively. In both complexes, the active-site metal atom was pentacoordinated by the side chains of Cys 90, His 132, and His 136 and the two oxygen atoms of N-formyl-hydroxylamine or hydroxamate. BB-3497 had activity against gram-positive bacteria, including methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis, and activity against some gram-negative bacteria. Time-kill analysis showed that the mode of action of BB-3497 was primarily bacteriostatic. The mechanism of resistance was via mutations within the formyltransferase gene, as previously described for actinonin. While actinonin and its derivatives have not been used clinically because of their poor pharmacokinetic properties, BB-3497 was shown to be orally bioavailable. A single oral dose of BB-3497 given 1 h after intraperitoneal injection of S. aureus Smith or methicillin-resistant S. aureus protected mice from infection with median effective doses of 8 and 14 mg/kg of body weight, respectively. These data validate PDF as a novel target for the design of a new generation of antibacterial agents.Ribosome-mediated synthesis of proteins starts with a methionine residue. In prokaryotes, the amino group of the methionyl moiety carried by the initiator tRNA fMet is N formylated by formyltransferase prior to its incorporation into a polypeptide. Consequently, N-formylmethionine is always present at the N terminus of a nascent bacterial polypeptide. However, most mature proteins do not retain the N-formyl group or the terminal methionine residue. Following translation, the formyl group is hydrolyzed by peptide deformylase (PDF), which is necessary for further processing at the N terminus by methionine aminopeptidase (32). Deformylation is therefore a crucial step in bacterial protein biosynthesis, and PDF is essential for bacterial growth (23). The gene encoding PDF (def) is present in all sequenced pathogenic bacterial genomes and has no mammalian counterpart, making it an attractive target for antibacterial chemotherapy. Although the enzyme has been known for 30 years, it has proved difficult to isolate and characterize due to its apparent instability. Recently, two X-ray crystal structures and a solution structure of PDF have been determined (5, 9, 12), identifying PDF as a new class of metalloenzyme related in structure to the metalloproteinase superfamily. ...

Our study reveals high frequencies of RASs to nonstructural protein 5A inhibitors in gt3 HCV; the paired A30K + L31M substitutions occur in all patients with gt3b and gt3g virus, and in vitro analysis suggests that these subtypes may be inherently resistant to all approved nonstructural protein 5A inhibitors for gt3 HCV. (Hepatology 2018).

SUMMARYFoot-and-mouth disease virus (FMDV) A22 Iraq 24/64 adapted to grow in BHK monolayer cells induced antibodies which neutralized many isolates belonging to the A serotype. Plaque-purified virus isolated from this stock also induced broadly reactive antibodies, showing that this property is not due to the combined response to a mixture of variants in the original stock virus. However, viruses obtained by passage in suspension BHK cells of either the monolayer cell-adapted virus or a virus cloned from this stock resulted in the selection of virus which induced antibodies with highly specific neutralizing activity. In addition to their antigenic properties the monolayer and suspension cell-adapted viruses could be distinguished by plaque morphology, tendency to aggregate and ability to attach to BHK cells. Monoclonal antibodies (MAbs) induced with the plaque-purified monolayer-adapted virus had neutralizing activity almost as broad as polyclonal serum, showing that this property can be represented by a single epitope on the virus. These neutralizing MAbs recognize a trypsin-sensitive epitope on the virus. Surprisingly, sequence analysis of the structural protein-coding regions of the genomic RNAs of monolayer and suspension celladapted viruses showed no amino acid differences in VP1, the protein known to contain the major neutralization epitope in FMDV and to be the only protein susceptible to cleavage by trypsin in the virus particle. Although three coding differences were found in the capsid protein these were all located in VP2.

The nucleotide sequence of the 5' untranslated region of foot and mouth disease virus (FMDV), serotype A10 has been determined. This completes the first total genomic sequence for any one serotype of FMDV. Analysis of the sequence to the 3' side of the poly (C) tract reveals the presence of a 24 nucleotide repeated motif which has homologies with a sequence located upstream of the transcriptional initiation site from several mammalian fibrinogen genes. The function of this element in FMDV is unclear. However, computer analysis of this region predicts the presence of a high degree of secondary and tertiary structure in which these repeats form an important part. The implications of these predictions are discussed.