JAC Advance Access originally published online on August 13, 2003
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Journal of Antimicrobial Chemotherapy (2003) 52, 375-381
© 2003 The British Society for Antimicrobial Chemotherapy
Antimicrobial activity of SMAP-29 against the Bacteroides fragilis group and clostridia
1 Institute of Microbiology, 2 Department of Biomedical Sciences and Technology, Udine Medical School, University of Udine, p.zza S.M. Misericordia 1, 33100 Udine; 3 National Laboratory CIB, AREA Science Park, Padriciano-Trieste; 4 Department of Biochemistry, Biophysics and Macromolecular Chemistry, University of Trieste, Italy
Received 20 January 2003, returned 24 February 2003; revised 11 June 2003; accepted 18 June 2003
Objectives: The cathelicidin-derived peptide SMAP-29 exerts rapid and broad-spectrum antimicrobial activity against aerobic bacteria and fungi. In this study, the effects of the peptide against the Bacteroides fragilis group, including antibiotic-resistant isolates, Clostridium perfringens and Clostridium difficile reference and clinical isolates, were investigated.
Methods: The microbicidal activity of SMAP-29 against eight reference and 100 clinical anaerobic strains from a national collection was assessed using a microdilution susceptibility assay, and by determining the killing kinetics on selected strains. The killing mechanism was investigated further by means of a two-colour fluorescent permeabilization assay, and by scanning electron microscopy (SEM).
Results: The Bacteroides fragilis group, Clostridium reference strains and most clinical isolates were inhibited in vitro by 1–2 µM (3.2–6.4 mg/L) SMAP-29, and killed by 1.5- to 2-fold higher peptide concentrations. The anaerobic bacterial cells were 90%–100% permeabilized within 2 h of exposure to bactericidal concentrations of the peptide. The SEM images of bacteria exposed to SMAP-29 provide morphological evidence that the envelope is an important target of the bactericidal activity of this peptide. These results are consistent with earlier studies indicating that SMAP-29 kills aerobic bacteria with a membranolytic mechanism, and suggest that both aerobic and anaerobic bacteria share surface features that are targeted by this peptide.
Conclusions: These studies demonstrate that the spectrum of antibacterial activity of SMAP-29 includes the B. fragilis group and Clostridium species, and encourage further investigations of the therapeutic potential of this peptide.
Keywords: antimicrobial peptide, cathelicidin, anaerobic bacteria, membrane permeabilization
* Corresponding author. Tel/Fax: +39-0432-559228; E-mail: alessandra.arzese{at}drmm.uniud.it
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