1 Laboratorio de Investigación Microbiológica and 2 Instituto de Biología Vegetal y Biotecnología, Universidad de Talca, Talca, Chile
Received 25 July 2003; returned 26 August 2003; revised 30 September 2003; accepted 12 November 2003
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Abstract |
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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.
Keywords: antibiotics, multiresistance and human infections
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Introduction |
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In the 1970s and 1980s, enterococci became clearly established as major nosocomial pathogens. They are now the fourth leading cause of hospital-acquired infection and the third leading cause of bacteraemia in the USA.2
The intrinsic resistance of enterococci to many commonly used antimicrobial agents may have given them an advantage for the further acquisition of genes encoding high levels of resistance to aminoglycosides, penicillins, tetracycline, chloramphenicol and vancomycin.3 The mechanisms of this resistance are mediated by mobile resistance genes on plasmids and transposons, which have the capacity to transfer resistance.4 Given this scenario, it is important to assess other possibilities for the control and treatment of E. faecalis infections.
During the last few years, we have investigated bacteriocins produced by bacteria isolated from the sediment of well water.5 In these studies, one Pseudomonas sp. strain was selected that is capable of inhibiting several Gram-positive and -negative bacterial strains. This microorganism produces a peptide called PsVP-10, of 2.4 kDa, which is very heat stable, resistant to proteolytic enzymes and tolerant to pH.
The principal aim of this study was to determine the activity of peptide PsVP-10 against several antimicrobial-resistant E. faecalis strains isolated from different clinical origins.
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Material and methods |
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The following antimicrobial compounds were used in the study: ampicillin, cefaloridine, gentamicin, tetracycline, chloramphenicol and vancomycin. The susceptibility tests for the E. faecalis strains were carried out by the qualitative diffusion method described by Bauer et al.8 The antimicrobial compounds were prepared according to NCCLS guidelines or the manufacturers recommendations. All the MICs were performed in duplicate following NCCLS guidelines, using the broth microdilution method.9
Results and discussion
Of the 85 E. faecalis strains, 67 (78.8%) were resistant to one or more antimicrobials (see Table 1). Only 18 strains (21.1%) were susceptible to all the antimicrobials studied. The antimicrobial-resistant E. faecalis strains were isolated from three different types of clinical samples (urinary tract infection, the bloodstream and soft tissues) and no difference in resistance was observed between them. Table 1 shows the various resistance phenotypes. Fourteen of the strains studied were resistant to three antibacterial drugs and two were resistant to two. It is possible that the resistance was encoded on a plasmid, as has been found previously in E. faecalis.4 Table 1 shows that chloramphenicol is the drug with the lowest antibacterial activity, whereas vancomycin is the most active compound. From the results it is important to note that in this area of Chile the proportion of vancomycin-resistant E. faecalis is currently low.
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In conclusion, the peptide PsVP-10 has been shown here to have good in vitro activity against all the sensitive and resistant E. faecalis isolates examined, and so presents an interesting possibility for the future. However, the peptide needs investigating further, and more in vitro and in vivo experiments are necessary to provide detailed information on the potential of this peptide as an antimicrobial drug.
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Acknowledgements |
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Footnotes |
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References |
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