The CIS-Required DNA Sequences for Bacteriophage Mu DNA Transposition and Maturation

Transposable elements are stretches of discrete DNA segments capable of rec-A independent translocation while maintaining their physical and functional integrityThe DNA of temperate bacteriophage Mu embodies the properties of both a tnasposable element and a phage. Its 37 kilobase linear double-stranded DNA is capable of catalysing and undergoing the full spectrum of DNA rearrangements characteristic of prokaryotic mobile elements. Mu DNA transposition requires the presence of the Mu encoded A and B gene products act upon sequences at the extremities of the Mu genome and catalyse the concerted nicking-ligation reactions inherent to most current models of DNA transposition. […]Les éléments de transposition sont des segments de DNA capables de translocation indépendante du gène recA et gardent leur integrité physique et fonctionnelle durant ces mouvements. Le bactériophage tempéré Mu accomplit les fonctions de phage ainsi que d'élément de transposition. Son DNA est linéaire, double-brin et est long d'environ 37 kilobase. Le DNA de Mu peut accomplir toute la gamme de réarrangements génétiques caracteristiques des éléments mobiles de transposition. Les produits des gènes A et B codés par Mu, des enzymes codés par des gènes de le région semi-essentielles du génome de Mu ainsi que des enzymes de la cellule hôte sont nécessaires pour que Mu transpose. Les enzymes de transposition interagissent avec des séquences aux extrémités du génome de Mu et ainsi catalysent des réactions de 'bris et ligations’ proposées dans plusieurs modèles de transposition. […

Relatedness of streptococcus suisSerotype 2 isolates from different geographic origins as evaluated by molecular fingerprinting and phenotyping

NRC publication: Ye

Associations between Antimicrobial Resistance Genes in Fecal Generic Escherichia coli Isolates from Cow-Calf Herds in Western Canada▿

The objective of this study was to examine associations among the genetic determinants of antimicrobial resistance (AMR) in 207 fecal generic Escherichia coli isolates obtained from 77 cow-calf herds in western Canada. Twenty-three resistance genes corresponding to six different antimicrobial families were assessed using DNA hybridization and PCR. The most common resistance genes in the study sample (207 isolates) were sul2 (48.3%), tet(B) (45.4%), and ant(3″)-Ia (aadA1) (19.3%). Several statistically significant associations between the examined resistance genes were detected. The strongest associations observed were those between genes for resistance to chloramphenicol (catI) and trimethoprim (dhfrI) (odds ratio [OR] = 214; P = 0.0001), sulfonamide (sul1) and chloramphenicol (catI) (OR = 96.9; P = 0.0001), streptomycin [ant(3″)-Ia (aadA1)] and trimethoprim (dhfrI) (OR = 96.2; P = 0.0001), sulfonamide (sul1) and streptomycin [ant(3″)-Ia (aadA1)] (OR = 79.3; P = 0.0001), and tetracycline [tet(B)] and sulfonamides (sul2) (OR = 25.7; P = 0.0001). At least one of the resistance genes corresponding to each nonaminoglycoside family of antimicrobials examined in this study was associated with the two aminoglycoside resistance genes ant(3″)-Ia (aadA1) and aph(3′)-Ia. The multiple, strong associations between genes and the diverse nature of the associations described in this study demonstrate the complexity of resistance gene selection in cow-calf herds and should be considered in the planning of AMR control practices for cow-calf operations

Phylogroup and lpfA influence epithelial invasion by mastitis associated Escherichia coli

Escherichia coli infection is one of the most common causes of bovine mastitis in well managed dairies. Although E. coli infections are usually transient, E. coli can also cause persistent intramammary infections. We sought to determine whether E. coli isolates recovered from either transient or persistent intramammary infections differed both genetically and in their ability to invade mammary epithelial cells. E. coli isolates from transient (ECtrans, n = 16) and persistent (ECpers, n = 12) mastitis cases were compared for differences in overall genotype, virulence genes, serotype, phylogroup (A, B1, B2, D), and invasion of bovine mammary epithelial cells, MAC-T by microarray analysis, suppressive subtractive hybridization, PCR and gentamicin protection assays. ECtrans and ECpers were diverse in overall genotype and serotype, and were predominantly of phylogroups A and B1. Both ECtrans and ECpers contained genes encoding type II, IV and VI secretion systems, long polar fimbriae (lpfA) and iron acquisition, and lacked genes associated with virulence in diarrheagenic E. coli. ECtrans had fewer virulence genes than ECpers (p < 0.05), but no individual virulence genes were unique to either group. In phylogroup A, ECpers were more invasive than ECtrans (p < 0.05), but no difference was observed between them in phylogroup B1. Enhanced epithelial cell invasion was associated with lpfA (p < 0.05). Our findings indicate that a genetically diverse group of E. coli is associated with transient and persistent mastitis. We did not identify a set of bacterial genes to account for phenotypic differences. However, we found that mastitis phenotype, phylogroup and presence of lpfA were associated with the ability to invade cultured bovine mammary epithelial cells.Peer reviewed: YesNRC publication: Ye

Biochemical analysis, cpn60 and 16S rDNA sequence data indicate that Streptococcus suis serotypes 32 and 34, isolated from pigs, are Streptococcus orisratti

NRC publication: Ye

Vitamin B12 Uptake by the gut commensal bacteria bacteroides thetaiotaomicron limits the production of shiga toxin by enterohemorrhagic escherichia coli

Enterohemorrhagic Escherichia coli (EHEC) are foodborne pathogens responsible for the development of bloody diarrhea and renal failure in humans. Many environmental factors have been shown to regulate the production of Shiga toxin 2 (Stx2), the main virulence factor of EHEC. Among them, soluble factors produced by human gut microbiota and in particular, by the predominant species Bacteroides thetaiotaomicron (B. thetaiotaomicron), inhibit Stx2 gene expression. In this study, we investigated the molecular mechanisms underlying the B. thetaiotaomicron-dependent inhibition of Stx2 production by EHEC. We determined that Stx2-regulating molecules are resistant to heat treatment but do not correspond to propionate and acetate, two short-chain fatty acids produced by B. thetaiotaomicron. Moreover, screening of a B. thetaiotaomicron mutant library identified seven mutants that do not inhibit Stx2 synthesis by EHEC. One mutant has impaired production of BtuB, an outer membrane receptor for vitamin B12. Together with restoration of Stx2 level after vitamin B12 supplementation, these data highlight vitamin B12 as a molecule produced by gut microbiota that modulates production of a key virulence factor of EHEC and consequently may affect the outcome of an infection

Immunization with Recombinant Sao Protein Confers Protection against Streptococcus suis Infection▿

Sao is a Streptococcus suis surface protein recently identified as a potential vaccine candidate. In this study, recombinant Sao in combination with Quil A provided cross-protection against S. suis serotype 2 disease in mouse and pig vaccination protocols. Subcutaneous immunization of mice elicited strong immunoglobulin G (IgG) antibody responses. All four IgG subclasses were induced, with the IgG2a titer being the highest, followed by those of IgG1, IgG2b, and IgG3. Challenge of the mice with S. suis strain 31533 resulted in a mortality rate of 80% for the control group, which received Quil A only. In contrast, all of the mice immunized with Sao survived. In a pig vaccination protocol, intramuscular immunization with Sao also elicited significant humoral antibody responses, and both the IgG1 and IgG2 subclasses were induced, with a predominance of IgG2 production. In vitro assay showed that Sao-induced antibodies significantly promoted the ability of porcine neutrophils in opsonophagocytic killing of S. suis. An aerosol challenge of the pigs with S. suis strain 166 resulted in clinical signs characteristic of S. suis infection in diseased pigs. The vaccine group showed significantly better survival, lower clinical scores, and less S. suis recovery from postmortem tissue samples than did the control group. Furthermore, this study also revealed that although challenge S. suis strains express Sao size variants, recombinant Sao conferred cross-protection. These data demonstrate that recombinant Sao formulated with Quil A triggers strong opsonizing antibody responses which confer efficient immunity against challenge infection with heterologous S. suis type 2