No abstract

SummaryIdentification of the novel PE multigene family was an unexpected finding of the genomic sequencing of Mycobacterium tuberculosis . Presently, the biological role of the PE and PE_PGRS proteins encoded by this unique family of mycobacterial genes remains unknown. In this report, a representative PE_PGRS gene (Rv1818c/ PE_PGRS33 ) was selected to investigate the role of these proteins. Cell fractionation studies and fluorescence analysis of recombinant strains of Mycobacterium smegmatis and M. tuberculosis expressing green fluorescent protein (GFP)-tagged proteins indicated that the Rv1818c gene product localized in the mycobacterial cell wall, mostly at the bacterial cell poles, where it is exposed to the extracellular milieu. Further analysis of this PE_PGRS protein showed that the PE domain is necessary for subcellular localization. In addition, the PGRS domain, but not PE, affects bacterial shape and colony morphology when Rv1818c is overexpressed in M. smegmatis and M. tuberculosis . Taken together, the results indicate that PE_PGRS and PE proteins can be associated with the mycobacterial cell wall and influence cellular structure as well as the formation of mycobacterial colonies. Regulated expression of PE genes could have implications for the survival and pathogenesis of mycobacteria within the human host and in other environmental niches.

Mycobacterium avium subspecies paratuberculosis was detected in the majority of Sardinian Crohn's disease patients. The finding of the organism colonizing a proportion of people without Crohn's disease is consistent with what occurs in other conditions caused by a primary bacterial pathogen in susceptible hosts.

Aims: To evaluate the antimicrobial effect of the ozonized sun¯ower oil (Oleozon) on different bacterial species isolated from different sites. Methods and Results: The effect of Oleozon on Mycobacteria, staphylococci, streptococci, enterococci, Pseudomonas and Escherichia coli was tested. The sun¯ower oil was ozonized at the Centro de Investigaciones del Ozone (CENIC, Havana, Cuba) by an ozone generator. MICs were determined by the agar dilution method. For Mycobacteria, the MIC of Oleozon was determined on solid medium by a microdrop agar proportion test. Oleozon showed antimicrobial activity against all strains analysed, with an MIC ranging from 1á18 to 9á5 mg ml )1 . Conclusions: Oleozon showed a valuable antimicrobial activity against all micro-organisms tested. Results suggest that Mycobacteria are more susceptible to Oleozon than the other bacteria tested. Signi®cance and Impact of the Study: The wide availability of sun¯ower oil makes Oleozon a competitive antimicrobial agent. These results should prompt the setting up of some clinical trials to compare Oleozon with other antimicrobial agents.

Enterococci are widely distributed in the environment; within the human body, they are normal commensals of the oral cavity, gastrointestinal tract and vagina. In recent years, enterococci have become one of the most frequent causes of acquired nosocomial infections worldwide. The molecular mechanism of virulence of these bacteria is still not completely understood. The aims of this work were to characterize phenotypically 47 isolates of Enterococcus faecalis and Enterococcus faecium collected in Sardinia (Italy) by their abilities to adhere to different epithelial cell lines (Vero and Caco-2 cells) and to associate their phenotypes with the presence of known virulence genes detected within their genomes by PCR. The following genes were amplified: AS (aggregation substance), esp (surface protein gene), ace (accessory colonization factor), efaA (E. faecalis endocarditis antigen) and gelE (gelatinase). The virulence genes were detected in E. faecalis isolates only, with the exception of esp, which was found in both species. The phenotypic and genotypic results were also compared with the susceptibility of isolates to various antibiotics.