Natural selection in the chicken host identifies 3-deoxy-D-manno-octulosonic acid kinase residues essential for phosphorylation of Pasteurella multocida lipopolysaccharide

Remodelling of the Gram-negative bacterial Kdo2-lipid A and its functional implications

The lipopolysaccharide (LPS) is a characteristic molecule of the outer leaflet of the Gram-negative bacterial outer membrane, which consists of lipid A, core oligosaccharide, and O antigen. The lipid A is embedded in outer membrane and provides an efficient permeability barrier, which is particularly important to reduce the permeability of antibiotics, toxic cationic metals, and antimicrobial peptides. LPS, an important modulator of innate immune responses ranging from localized inflammation to disseminated sepsis, displays a high level of structural and functional heterogeneity, which arise due to regulated differences in the acylation of the lipid A and the incorporation of non-stoichiometric modifications in lipid A and the core oligosaccharide. This review focuses on the current mechanistic understanding of the synthesis and assembly of the lipid A molecule and its most salient non-stoichiometric modifications.

Antibacterial potential and mechanism of action of dithiocyano-methane as a bactericidal agent for farm disinfection

AIMS

This study aimed to investigate the antibacterial ability and action mechanism of dithiocyano-methane against Aeromonas hydrophila, so as to provide a reference for its application in farm disinfection.

METHODS AND RESULTS

After exposing the bacteria to dithiocyano-methane, the minimum inhibitory concentration (MIC), minimum bactericide concentration (MBC), activities of alkaline phosphatase, aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase and electric conductivity in bacterial suspensions were determined, transmission electron microscope images on cellular structure and SDS-PAGE profile of bacterial proteins were analysed and the expression of genes related to the above experimental observations was confirmed by real-time quantitative PCR. The MIC and MBC of dithiocyano-methane against three tested strains was 1·46 and 2·93 mg l^-1 respectively. The results showed that dithiocyano-methane significantly damaged bacterial cell structure, inhibited the biosynthesis of bacterial proteins and changed the integrity and permeability of bacterial cell wall and cell membrane.

CONCLUSIONS

Dithiocyano-methane showed remarkable antibacterial ability against three tested strains, indicating it is a potential effective bactericidal agent for preventing animal diseases resulted from Aer. hydrophila.

SIGNIFICANCE AND IMPACT OF THE STUDY

To our best knowledge, this is the first report to examine the antibacterial ability and action mechanism of dithiocyano-methane against bacteria. The results demonstrate the great potential of dithiocyano-methane as a disinfectant against Aer. hydrophila in settings such as aquaculture ponds and livestock farms.

Comparative Genomic Analysis of Asian Haemorrhagic Septicaemia-Associated Strains of Pasteurella multocida Identifies More than 90 Haemorrhagic Septicaemia-Specific Genes

Pasteurella multocida is the primary causative agent of a range of economically important diseases in animals, including haemorrhagic septicaemia (HS), a rapidly fatal disease of ungulates. There is limited information available on the diversity of P. multocida strains that cause HS. Therefore, we determined draft genome sequences of ten disease-causing isolates and two vaccine strains and compared these genomes using a range of bioinformatic analyses. The draft genomes of the 12 HS strains were between 2,298,035 and 2,410,300 bp in length. Comparison of these genomes with the North American HS strain, M1404, and other available P. multocida genomes (Pm70, 3480, 36950 and HN06) identified a core set of 1,824 genes. A set of 96 genes was present in all HS isolates and vaccine strains examined in this study, but absent from Pm70, 3480, 36950 and HN06. Moreover, 59 genes were shared only by the Asian B:2 strains. In two Pakistani isolates, genes with high similarity to genes in the integrative and conjugative element, ICEPmu1 from strain 36950 were identified along with a range of other antimicrobial resistance genes. Phylogenetic analysis indicated that the HS strains formed clades based on their country of isolation. Future analysis of the 96 genes unique to the HS isolates will aid the identification of HS-specific virulence attributes and facilitate the development of disease-specific diagnostic tests.

Pasteurella multocida: from zoonosis to cellular microbiology

In a world where most emerging and reemerging infectious diseases are zoonotic in nature and our contacts with both domestic and wild animals abound, there is growing awareness of the potential for human acquisition of animal diseases. Like other Pasteurellaceae, Pasteurella species are highly prevalent among animal populations, where they are often found as part of the normal microbiota of the oral, nasopharyngeal, and upper respiratory tracts. Many Pasteurella species are opportunistic pathogens that can cause endemic disease and are associated increasingly with epizootic outbreaks. Zoonotic transmission to humans usually occurs through animal bites or contact with nasal secretions, with P. multocida being the most prevalent isolate observed in human infections. Here we review recent comparative genomics and molecular pathogenesis studies that have advanced our understanding of the multiple virulence mechanisms employed by Pasteurella species to establish acute and chronic infections. We also summarize efforts being explored to enhance our ability to rapidly and accurately identify and distinguish among clinical isolates and to control pasteurellosis by improved development of new vaccines and treatment regimens.

The key surface components of Pasteurella multocida: capsule and lipopolysaccharide

The capsule and lipopolysaccharide (LPS) of Pasteurella multocida constitute the major components of the bacterial cell surface. As well as forming the basis for the most widely used classification systems, they play key roles in a range of interactions between the bacteria and the hosts they colonize or infect. Both polysaccharides are involved in the avoidance of host innate immune mechanisms, such as resistance to phagocytosis, complement-mediated killing, and the bactericidal activity of antimicrobial peptides; they are therefore essential for virulence. In addition, LPS is a major antigen in the stimulation of adaptive immune responses to infection.