[Risk factors and clinical prognosis analysis of carbapenem-resistant Enterobacterales bacteria nosocomial infection]

Objective: To explore the risk factors for carbapenem-resistant Enterobacterales (CRE) infection and death. Methods: A case-control analysis of 482 inpatients in 18 secondary or tertiary hospitals in Beijing in 2018 was conducted. Patients infected by CRE were selected as the case group (n=247), and infected by carbapenem susceptible Enterobacterales (CSE) as the control group (n=235). The risk factors and clinical prognosis of CRE infection were analyzed by single factor analysis and multivariate logistic regression analysis. Results: CRE were resistant to most antimicrobials, but were highly sensitive to colistin and tigecycline, with sensitivity of 94.0% and 99.5%, respectively. Multivariate analysis showed that prior 30-day tracheal intubation (OR=2.607, 95%CI: 1.655-4.108, P<0.001), empirical treatment using third or fourth generation cephalosporins (OR=2.339, 95%CI: 1.438-3.803, P=0.001), carbapenems (OR=2.468, 95%CI: 1.610-3.782, P<0.001) and quinolones (OR=2.042, 95%CI: 1.268-3.289, P=0.003) were independent risk factors for CRE infection. Mechanical ventilation (OR=3.390, 95%CI: 1.454-7.904, P=0.005), heart failure (OR=4.679, 95%CI: 1.975-11.083, P<0.001), moderate or severe liver disease (OR=3.057, 95%CI: 1.061-8.806, P=0.038), prior 30-day quinolones exposure (OR=2.882, 95%CI: 1.241-6.691, P=0.014) and septic shock (OR=7.772, 95%CI: 3.505-17.233, P<0.001) were independent risk factors for death after CRE infection. Conclusions: Reducing the use of antimicrobials and invasive procedures such as prior 30-day tracheal intubation may reduce the probability of CRE infection. Grading the severity of the underlying disease in patients with CRE infection, as well as predicting and preventing the occurrence of septic shock will help reduce the risk of death.

MvirDB--a microbial database of protein toxins, virulence factors and antibiotic resistance genes for bio-defence applications

Knowledge of toxins, virulence factors and antibiotic resistance genes is essential for bio-defense applications aimed at identifying ‘functional’ signatures for characterizing emerging or engineered pathogens. Whereas genetic signatures identify a pathogen, functional signatures identify what a pathogen is capable of. To facilitate rapid identification of sequences and characterization of genes for signature discovery, we have collected all publicly available (as of this writing), organized sequences representing known toxins, virulence factors, and antibiotic resistance genes in one convenient database, which we believe will be of use to the bio-defense research community. MvirDB integrates DNA and protein sequence information from Tox-Prot, SCORPION, the PRINTS virulence factors, VFDB, TVFac, Islander, ARGO and a subset of VIDA. Entries in MvirDB are hyperlinked back to their original sources. A blast tool allows the user to blast against all DNA or protein sequences in MvirDB, and a browser tool allows the user to search the database to retrieve virulence factor descriptions, sequences, and classifications, and to download sequences of interest. MvirDB has an automated weekly update mechanism. Each protein sequence in MvirDB is annotated using our fully automated protein annotation system and is linked to that system's browser tool. MvirDB can be accessed at .

Polyhedron-like inclusion body formation by a mutant nucleopolyhedrovirus expressing the granulin gene from a granulovirus

The polyhedrin gene in Bombyx mori nucleopolyhedrovirus (BmNPV) was replaced with the granulin gene of Trichoplusia ni granulovirus (TnGV). The substitution was verified by Southern hybridization, and expression of granulin by the mutant virus, BmGran, was demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by amino acid sequencing of the predominant protein of BmGran inclusion bodies (IBs). Light and electron microscopy examination of BmGran-infected B. mori and BmN cells revealed large, cuboidal, polyhedron-like IBs in the nucleus and cytoplasm, but granules were not seen. IBs contained small, parallel, electron-dense streaks, which defined the geometric pattern of crystallization. Geometric patterns of nuclear IBs were frequently disrupted by occlusion of polyhedron envelope fragments, resulting in IB instability and fracturing. Virions were not embedded in most of the polyhedron-like IBs, but accumulated with polyhedron envelope fragments. Some virions were coated with matrix protein and were partially wrapped by polyhedron envelope. These results suggested that (1) the amino acid sequence of granulin insufficient for determining IB morphology in TnGV-infected cells, and TnGV may have genes, not present in BmNPV, that control granule formation, and (2) interactions among the virion, the IB envelope, and the matrix protein may be important in virion occlusion and IB morphology and stability.

Deletion analysis of four of eighteen late gene expression factor gene homologues of the baculovirus, BmNPV

Nucleotide sequence analysis of the genome of the baculovirus Bombyx mori nuclear polyhedrosis virus (BmNPV) identified 18 homologues of the Autographa californica NPV (AcNPV) lefs (late expression factor genes). These BmNPV lefs showed high (73-98%) amino acid sequence identities to AcNPV lefs and were localized to similar positions in the genome. One lef, p35, was previously characterized in AcNPV and BmNPV deletion experiments. Functional deletion of each of the BmNPV lef homologues was attempted here by insertion of a beta-galactosidase gene cassette into the coding region of each lef. Four of 18 BmNPV lef (39K, ie-2, lef-7, and p35) deletion mutants were successfully isolated, indicating that the other 14 BmNPV lefs were likely essential for viral replication in cell culture. Further analysis showed that deletion of lef-7, p35, and ie-2 resulted in lower levels of viral DNA replication, indicating that the BmNPV lef-7, p35, and ie-2 products have stimulating effects on DNA replication. Deletion of 39K resulted in a significantly lower level of late gene transcription and extremely low (over 10(2)-fold less at 48-80 hr p.i.) production of progeny budded virus in BmN cells. In contrast, the deletion did not affect viral DNA replication, indicating that BmNPV 39K is involved in late gene transcription. Reduced late gene expression presumably affected production and/or release of progeny budded virus particles. This was corroborated by transmission electron microscopy, which showed that virus replication was abnormal in BmN cells infected with a BmNPV mutant lacking 39K and virion production was low. Even though 39K deletion resulted in a loss of oral infectivity, the 39K deletion mutant replicated in silkworm larvae when injected into the body cavity, as did the ie-2, lef7, and p35 deletion mutants. In addition, a BmNPV homologue of the baculovirus very late expression factor gene (vif-1) found in AcNPV was essential, implying an essential function of the BmNPV vif-1 homologue at a step before the onset of very late gene expression.