Comparative in vitro activity of five cathelicidin-derived synthetic peptides against Leptospira, Borrelia and Treponema pallidum.
OBJECTIVE
The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of five different cathelicidin-derived synthetic peptides (SMAP-29, LL-37, PG-1, CRAMP and BMAP-28) for Leptospira interrogans, Borrelia spp. and Treponema pallidum subsp. pallidum were investigated in vitro.


METHODS
The MIC of individual peptides was defined as the lowest concentration able to inhibit the motility of spirochaetes after 2 h of incubation, as detected by dark-field microscopy. The MBC of individual peptides was defined as the lowest concentration at which no spirochaetes were subcultured either in cathelicidin-free medium (leptospires and borreliae) or in hamsters (T. pallidum).


RESULTS
The MIC values of peptides for leptospires were highly variable, depending on the compound and the strain used. Of the five cathelicidin-derived peptides, SMAP-29 from sheep and BMAP-28 from cattle were the most active against L. interrogans serovars, with MIC values varying between 3 and 51 mg/L, depending on the strains. The MICs of the remaining synthetic peptides ranged between 4.3 and 224 mg/L. The MIC values of synthetic peptides for T. pallidum ranged between 32.3 mg/L for PG-1 and 449.4 mg/L for LL-37. The MICs of all cathelicidin-derived peptides tested for Borrelia strains ranged between 307 and 449.4 mg/L. The activity of the peptides on the motility of spirochaetes was both dose- and time-dependent. The MBC values of the peptides were the same as the MIC values.


CONCLUSIONS
The results of this study demonstrate that the activity of cathelicidin-derived peptides against spirochaetes is fast and highly variable, depending on the species and the strain.
Sambri
Vittorio
V
Sezione di Microbiologia, DMCSS, Ospedale Policlinico S.Orsola, University of Bologna, Via Massarenti 9, 40138 Bologna.
Marangoni
Antonella
A
Giacani
Lorenzo
L
Gennaro
Renato
R
Murgia
Rossella
R
Cevenini
Roberto
R
Cinco
Marina
M
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology*; D001798:Blood Proteins / Q000494:pharmacology; D001898:Borrelia / Q000187:drug effects* / Q000302:isolation & purification; D054804:Cathelicidins; D002417:Cattle; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D006224:Cricetinae; D006801:Humans; D007919:Leptospira / Q000187:drug effects* / Q000302:isolation & purification; D008297:Male; D008647:Mesocricetus; D051379:Mice; D008826:Microbial Sensitivity Tests / Q000706:statistics & numerical data; D011506:Proteins / Q000494:pharmacology; D011817:Rabbits; D012756:Sheep; D013552:Swine; D014210:Treponema pallidum / Q000187:drug effects* / Q000302:isolation & purification
D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; C102360:BMAP-28; D001798:Blood Proteins; D054804:Cathelicidins; D011506:Proteins; C403305:SMAP29 protein, Ovis aries; C094880:protegrin-1