A Twistor Formulation of the Non-Heterotic Superstring with Manifest Worldsheet Supersymmetry

We propose a new formulation of the $D=3$ type II superstring which is manifestly invariant under both target-space $N=2$ supersymmetry and worldsheet $N=(1,1)$ super reparametrizations. This gives rise to a set of twistor (commuting spinor) variables, which provide a solution to the two Virasoro constraints. The worldsheet supergravity fields are shown to play the r\^ole of auxiliary fields.Comment: 21p., LaTe

A twistor-like D=10 superparticle action with manifest N=8 world-line supersymmetry

We propose a new formulation of the $D=10$ Brink-Schwarz superparticle which is manifestly invariant under both the target-space super-Poincar\'e group and the world-line local $N=8$ superconformal group. This twistor-like construction naturally involves the sphere $S^8$ as a coset space of the $D=10$ Lorentz group. The action contains only a finite set of auxiliary fields, but they appear in unusual trilinear combinations. The origin of the on-shell $D=10$ fermionic $\kappa$ symmetry of the standard Brink-Schwarz formulation is explained. The coupling to a $D=10$ super-Maxwell background requires a new mechanism, in which the electric charge appears only on shell as an integration constant.Comment: 22pages, standard LATEX fil

Nonradioactive DNA probe for detection of gene for methicillin resistance in Staphylococcus aureus.

A DNA probe was developed by inserting, in the SmaI site of pBluescript sK, a 528-bp fragment of the gene responsible for intrinsic resistance to beta-lactam antibiotics in Staphylococcus aureus (mec determinant). The mec probe provided a useful tool for the rapid identification of the intrinsic resistance trait and for establishing guidelines for testing the in vitro susceptibility of S. aureus to beta-lactams

Characterization of integrons in Burkholderia cepacia clinical isolates

Burkholderia cepacia is an opportunistic pathogen able to colonize the airways of Cystic Fibrosis (CF) patients, frequently developing chronic infections. In 20% of cases these infections cause severe and poorly controlled pathological situations because of the intrinsic antibiotic resistance expressed by the microorganism. CF patients are often subjected to antibiotic therapy: this facilitates the acquisition of antibiotic resistance determinants by the infecting bacteria. Integrons are mobile genetic elements that are widespread in bacterial populations and favor the acquisition of gene cassettes coding for these determinants.The presence of class 1 integrons was investigated by PCR with primers specific for the 5’ and 3’ ends in Burkholderia isolates recovered from patients in treatment at the CF center of Friuli Venezia Giulia. The same integron, carrying an uncommon allelic form (Ib) of the aacA4 gene in its cassette array and conferring resistance to some aminoglycosides, was found in two independent isolates (different RAPD profiles) infecting two different patients. In both isolates the integron was carried by plasmids and was still present 3 and 6 years later the first finding. Despite the exchange of integrons between bacterial pathogens is fully described, these items were not frequently found in Burkholderia isolates. Although the clinical relevance of the integron we identified is low (a single gene cassette encoding a widespread resistance),we feel concerned that these genetic elements begin to circulate in this bacterial species, as this could make more and more troublesome the treatment of infections notoriously difficult to eradicate

Metallo-\u3b2-lactamase expression confers an advantage to Pseudomonas aeruginosa isolates compared with other \u3b2-lactam resistance mechanisms, favoring the prevalence of metallo-\u3b2-lactamase producers in a clinical environment.

The Pseudomonas aeruginosa isolate TS-832035 exhibited a high level resistance to carbapenems for the contemporary presence of two independent mechanisms: the production of a carbapenemase, coded by a blaVIM-1 determinant carried by a class 1 integron In70.2 and the lack of the OprD porin. We compared TS-832035 with a strictly related isolate, TS-103 that didn\u2019t carry In70.2. These experiments highlighted a significant in vitro fitness cost associated with the integron. On the contrary, none of the resistance determinants other than the blaVIM-1seemed to confer a real selective advantage to its host. Comparison of these results with the in vivo behaviour, showing that the In70.2-carrying isolates largely prevailed over the In70.2-lacking ones, evidence the need to investigate accurately the causes of their large distribution, as possible soft spots could exist in the ability of their hosts to adapt to the hospital settings