Plasmid-mediated bacteriocin production by Shigella flexneri isolated from dysenteric diarrhoea and their transformation into Escherichia coli.

AIMS: To determine the production of bacteriocin by Shigella flexneri strains, to relate their production to the presence of dysenteric diarrhoea and to asses the genetic determination of the bacteriocin. METHODS AND RESULTS: One hundred and sixteen strains of Sh. flexneri were isolated from patients with diarrhoea and 49 of them produced bacteriocin active against several Escherichia coli and abacteriocinogenic Sh. flexneri strains. The extrachromosomal DNA isolated from bacteriocinogenic Sh. flexneri strains were used as a substrate to transform E. coli HB-101 cells by means of electroporation. CONCLUSIONS: Only the Sh. flexneri strains isolated from dysenteric diarrhoea produced bacteriocin. It was demonstrated that a plasmid of approx. 3 kb was responsible for the genetic determination of these anti-bacterial substances. SIGNIFICANCE AND IMPACT OF THE STUDY: A 3-kb plasmid that harboured information for the production of bacteriocin by Sh. flexneri strains was described. The production of this bacteriocin may be related to dysenteric diarrhoea produced by these bacterial strains.

Actividad in vitro de 5 antifúngicos contra aislados clínicos y ambientales de pichia anomala / In vitro activity of 5 antifungal against environmental and clinical isolates of pichia anomala

Las infecciones fúngicas han aumentado en el último tiempo, entre ellas, las infecciones por levaduras emergentes, cuyos patrones de sensibilidad no han sido estudiados debido a la inexistencia de patrones de temperatura y medios de cultivo apropiados para realizar test de sensibilidad. El presente trabajo, fue propuesto como un modelo experimental de Pichia anomala, aislada de pacientes con MICs superiores que los aislados ambientales, siendo la anfotericina B el antifúngico con la mejor actividad antifúngica.

In vitro antibacterial activity of the peptide PsVP-10 against antimicrobial-resistant Enterococcus faecalis isolated from clinical samples.

OBJECTIVE: To analyse the antimicrobial activity of the peptide PsVP-10 against 67 resistant Enterococcus faecalis strains isolated from clinical samples. METHODS: The qualitative disc diffusion method and MIC determinations were used. RESULTS: The presence of several multidrug-resistant phenotypes of E. faecalis was demonstrated, in which there were high MICs to chloramphenicol, tetracycline, vancomycin, cefaloridine, ampicillin and gentamicin. In comparison, the peptide PsVP-10 showed lower MICs against all the multidrug-resistant and susceptible E. faecalis. CONCLUSIONS: There is an urgent need for the development of novel antimicrobial agents against the highly resistant E. faecalis. The present study shows that the peptide PsVP-10 might make a contribution to the solution of this serious problem.

Production of antimicrobial substances, by hospital bacteria, active against other micro-organisms.

Fifty-nine clinical strains of bacteria, isolated from patients in the Regional Hospital of Talca, were studied. Seventy-four percent of these strains produced antibacterial substances, in comparison with 18% of the same bacterial species obtained from patients from a non-hospital habitat. Almost all the bacteria isolated from hospitalized patients demonstrated in vitro resistance to different antimicrobial agents. Pseudomonas aeruginosa was the most frequent species producing antibacterial substances and its products were of high potency, with a wide spectrum of antimicrobial activity. Cure of plasmid DNA, in most of the antibacterial-producer strains, resulted in the loss of their lethal activity and they also became susceptible in vitro to anti-microbials. These results indicated that such properties are encoded in extrachromosomal DNA. We believe that the knowledge of the antimicrobial activity and resistance to antimicrobials of bacteria from a hospital habitat can help explain the selection and persistence of such strains in this particular ecological niche.

Note: purification and characterization of the bacteriocin PsVP-10 produced by Pseudomonas sp.

A bacteriocin (bacteriocin PsVP-10) produced by Pseudomonas sp. R-10 was purified by a simple method that included an extraction of the bacteriocin with chloroform, followed by cation exchange chromatography. The purity of the bacteriocin was verified by RP-HPLC. It is a peptide of 2.4 kDa, very stable to heat, to proteolytic enzymes and to pH. It presents a very broad spectrum of antimicrobial activity against Gram-positive and Gram-negative bacteria.

Inhibition of the growth of enteropathogenic bacilli by bacteriocins produced by micro-organisms from the sediment of wells.

The bacterial flora of the sediment of 20 wells of water for human consumption in the rural area of the VII Region in Chile was examined. Fourteen strains of bacteria, from different wells, produced bacteriocins which inhibited the growth of Salmonella typhi, Salm. typhimurium, Shigella sonnei and enterotoxigenic Escherichia coli. About 50% of these strains contained plasmids of different molecular weight and a large number of these codified for bacteriocins. The results suggest what is required to implement an efficient, simple and economical biological system for the purification or control of the number of enteropathogenic bacilli of well water in the rural area.

[Uropathogenic Serratia marcescens of hospital origin: analysis of the adhesion mechanism of 2 strains]. / Serratia marcescens uropatogenicas de origen hospitalario. analisis del mecanismo adherente de dos cepas.

We isolated 2 Serratia marcescens strains, fim (0) and fim (-), from patients with urinary tract infection. Adhesion properties were studied by hemagglutination, response of uroepithelial cells and electron microscopy techniques. S marcescens fim (+) showed high adherence to uroepithelial cells, hemagglutination capacity and peculiar electron microscopy characteristics. All of these are absent in the fim (-) variety. The fim (+) strain was resistant to nitrofurantoin, nalidixic acid, tetracyclin, ampicillin, gentamycin, cefradine, cephotaxime and cotrimoxazole, whereas the fim (-) strain was sensitive to all. An absence of extrachromosomal DNA was demonstrated in S marcescens fim (+) suggesting that its characteristics are not coded in plasmids.