Revealing the latent mobilization capability of the staphylococcal bacteriocinogenic plasmid pRJ9

Plasmid pRJ9 is a non-self-mobilizable bacteriocinogenic plasmid from Staphylococcus aureus. Despite this feature, DNA sequencing and RT-PCR experiments showed that it presents a Mob region with three genes (mobCAB), transcribed as an operon. In silico analysis of the Mob proteins encoded by pRJ9 showed that they present all the conserved functional features reported until present as being essential for plasmid mobilization. Moreover, they showed a high identity to Mob proteins encoded by mobilizable plasmids from Staphylococcus spp., especially to those encoded by plasmid pRJ6, which presents four mob genes (mobCDAB). A putative oriT region was also found upstream of the pRJ9 mob operon. pRJ9 could only be successfully mobilized by pGO1 when pRJ6 was present in the same strain. Further experiments showed that the pRJ9 oriT can be recognized by the pRJ6 Mob proteins, confirming its functionality. As pRJ9 does not possess a mobD gene while pRJ6 does, the absence of this gene was believed to be responsible for its lack of mobilization. However, conjugation experiments with a donor strain carrying also mobD cloned into an S. aureus vector showed that pRJ9 does not become mobilized even in the presence of the protein MobD encoded by pRJ6. Therefore, the reasons for pRJ9 failure to be mobilized are presently unknown.     

Mobilization functions of the bacteriocinogenic plasmid pRJ6 of <Emphasis Type="Italic">Staphylococcus aureus</Emphasis>

Plasmid pRJ6 is the first known bacteriocinogenic mobilizable (Mob) plasmid of Staphylococcus aureus. Its Mob region is composed of four mob genes (mobCDAB) arranged as an operon, a genetic organization uncommon among S. aureus Mob plasmids. oriT _pRJ6 was detected in a region of 431 bp, positioned immediately upstream of mobC. This region, when cloned into pCN37, was able to confer mobilization to the re-combinant plasmid only in the presence of pRJ6. The entire Mob region, including oriT _pRJ6, is much more similar to Mob regions from several coagulase-negative staphylococci plasmids, although some remarkable similarities with S. aureus Mob plasmids can also be noted. These similarities include the presence within oriT _pRJ6 of the three mcb (MobC binding sites), firstly described in pC221 and pC223, an identical nick site also found in these same plasmids, and a nearly identical sra _pC223 site (sequence recognized by MobA). pRJ6 was successfully transferred to S. epidermidis by conjugation in the presence of the conjugative plasmid pGOl. Altogether these findings suggest that pRJ6 might have been originally a coagulase-negative staphylococci plasmid that had been transferred successfully to S. aureus.     

The issues of energy and carbon cycle: new perspectives for assessing the environmental impact of animal waste utilization

This paper focuses on the benefits of an efficient use of animal waste from the standpoint of curbing the rise of anthropogenic carbon dioxide (CO(2)) in the atmosphere. An effective use of animal waste resources might provide a partial, but still important, contribution in reducing net CO(2) emissions. In particular: the fulfillment of nutrient requirements of crop plants growing in non-limiting conditions and thus sequestering CO(2) at their potential level; the chance of diminishing the use of fossil energy, and related CO(2) emissions, required for manufacturing industrial fertilizers; the possibility of enhancing carbon sequestration in agricultural soils by the application of farmyard manure. The future success of agriculture in providing these ecosystem services can only be achieved with a changed social awareness of the links between sustainable land use and global environmental change.     

Dissemination of Periodontal Pathogens in the Bloodstream after Periodontal Procedures: A Systematic Review

Background

To date, there is no compilation of evidence-based information associating bacteremia and periodontal procedures. This systematic review aims to assess magnitude, duration, prevalence and nature of bacteremia caused by periodontal procedures.

Study Design

Systematic Review

Types of Studies Reviewed

MEDLINE, EMBASE and LILACS databases were searched in duplicate through August, 2013 without language restriction. Observational studies were included if blood samples were collected before, during or after periodontal procedures of patients with periodontitis. The methodological quality was assessed in duplicate using the modified Newcastle-Ottawa scale (NOS).

Results

Search strategy identified 509 potentially eligible articles and nine were included. Only four studies demonstrated high methodological quality, whereas five were of medium or low methodological quality. The study characteristics were considered too heterogeneous to conduct a meta-analysis. Among 219 analyzed patients, 106 (49.4%) had positive bacteremia. More frequent bacteria were S. viridans, A. actinomycetemcomitans P. gingivalis, M. micros and species Streptococcus and Actinomyces, although identification methods of microbiologic assays were different among studies.

Clinical Implications

Although half of the patients presented positive bacteremia after periodontal procedures, accurate results regarding the magnitude, duration and nature of bacteremia could not be confidentially assessed.     

Aureocin A70 production is disseminated amongst genetically unrelated Staphylococcus aureus involved in bovine mastitis

Aims: The main aim of this study was to analyse the genetic relationship amongst 46 Staphylococcus aureus Bac⁺ strains isolated in Brazil from 12 geographically distant dairy herds, including 34 isolates that produce the antimicrobial peptide aureocin A70. Methods and Results: The comparison of 46 Staph. aureus Bac⁺ strains was performed by pulsed‐field gel electrophoresis (PFGE). Thirteen different pulsotypes were identified, and the subtype A₁ was the most prevalent one. Nine strains belong to pulsotype F, the second most prevalent and mostly confined to a single herd. The PFGE patterns of the 34 Staph. aureus aureocin A70‐producers, isolated in Brazil, were also compared with those of strains isolated from bovine mastitis cases in Argentina and revealed that these strains are not genetically related. Conclusions: Although a previous study has suggested that a prevalent pulsotype of aureocin A70‐producer Staph. aureus involved in bovine mastitis is disseminated in Argentina, this does not occur in Brazil. Additionally, it was possible to demonstrate that closely related staphylococcal strains can produce distinct staphylococcins. Significance and Impact of the Study: This study corroborates the hypothesis of horizontal gene transfer of aureocin A70 genes amongst distinct staphylococcal strains involved in bovine mastitis, giving them a selective advantage when colonizing the mammary glands.