144 research outputs found
Antibacterial activity of wood distillate from residual virgin chestnut biomass
No full textThe antibacterial properties of a wood distillate obtained from residual virgin chestnut biomass were investigated by means of quantitative MIC (minimum inhibitory concentration) test and a whole-cell assay that specifically responds to different classes of antimicrobials on the basis of the mode of action. Results indicate that wood distillate is active against gram-positive and gram-negative bacteria related to human and/or fish diseases with a mechanism, which could mainly affect wall components and plasma membrane of the bacterial cells. These findings highlight the possible sustainable use of chestnut residues as a source of bioactive natural compounds with antibacterial properties
Ceratotoxins, antibacterial sex-specific peptides from the medfly Ceratitis capitata.
No full textCtxs are a family of α-helical, cationic, 3 kDa antibacterial peptides secreted by the female reproductive accessory glands of the Mediterranean fruit fly Ceratitis capitata. These peptides were found to display strong antibacterial activity and weak hemolytic activity. When reconstituted into planar lipid bilayers chemically synthesized Ctxs formed voltage-dependent ion channels according to the barrel-stave model. A synthetic truncated CtxA molecule resulted to permeabilize the outer and inner membranes of Escherichia coli cells
Dominant symbiotic bacteria associated with wild medfly populations reveal a bacteriocin-like killing phenotype: A 'cold-case' study
No full textThe gut of the agricultural pest Ceratitis capitata hosts a varied community of bacteria, mainly Enterobacteriaceae, that were implicated in several processes that increase the fitness of the insect. In this study, we investigated the antagonistic activity in vitro of Klebsiella oxytoca strains isolated in the 1990s from the alimentary tract of wild medflies collected from different varieties of fruit trees at diverse localities. Assays were carried out against reference strains (representative of Gram-negative and -positive bacterial species) of the American Type Culture Collection (ATCC). Eight Klebsiella, out of 11, expressed a killing activity against Escherichia coli ATCC 23739, and Enterobacter cloacae ATCC 13047; among the eight strains, at least one showed activity against Salmonella typhimurium ATCC 23853. Genomic DNA derived from all Klebsiella strains was then subjected to PCR amplification using specific primer pairs designed from each of the four bacteriocin (KlebB, C, D, CCL) sequences found so far in Klebsiella. KlebD primer pairs were the only to produce a single product for all strains expressing the killing phenotype in vitro. One of the amplicons was cloned and sequenced; the DNA sequence shows 93% identity with a plasmid-carried colicin-D gene of a strain of Klebsiella michiganensis, and 86% identity with the sequence encoding for the klebicin D activity protein in K. oxytoca. Our work provides the first evidence that dominant symbiotic bacteria associated with wild medfly populations express a killing phenotype that may mediate inter and intraspecies competition among bacterial populations in the insect gut in vivo
Isolation of Aeromonas spp. strains from animals.
No full textThe isolation of Aeromonas strains from slaughtered pigs is reported. Among a total of 20 strains isolated after cold enrichment, 15 were identified as Aeromonas hydrophila and five as A. caviae. Cytotoxic activity was detected on HEp-2 cells for all A. hydrophila isolates. Two A. hydrophila strains from different animals produced an enterotoxin detected with the suckling-mouse test while the A. caviae did not exhibit either cytotoxicity or enterotoxicity
The novel antibacterial peptide ceratotoxin A alters the outer and the inner membranes of Escherichia coli K-12.
No full textCeratotoxins are antibacterial 3-kDa amphiphilic peptides isolated from the female reproductive apparatus of the medfly Ceratitis capitata. The antibacterial activity of a chemically synthesized ceratotoxin A (ctx A) has been investigated. Ctx A was mainly active against Gram negative organisms, and it had a lytic effect on nongrowing Escherichia coli K-12. Data showed that ctxA alters both the outer and the inner membrane of E. coli K-12 cells
RICERCA DI FAGI lN CAMPYLOBACTER TERMOFILI: DATI PRELIMINARI
No full textEighty Campylobacter jejuni/coli strains were screened for phage by induction with mitomycin C. After treatment of culturès with mitomycin C (1 μg/ml for 18 h), cells were removed by centrifugation and supernatants examined by electron microscopy Phage paiticles were recovered from one strain of C. ieiuni; electron micrographs showed that the phage head is isometric, 53 nm in diameter, and that the sheathed tail is about 113 nm long. The morphological feature of this phage qppears to be simiilar to that described by Rittchie et al. for a phage detected from C. jeiuni isolates
Detection of replicon-specific regions in DNAs derived lrom antarctic microbial community
No full textDifferenziazione di campylobacter termofili isolati da casi di gastroenterite infantile.
No full textEighty Campylobacter thermophilic group strains were isolated from 79/813 (9.7%) fecal specimens obtained from infantile gastroenteritis cases in the period January 1981-December 1982. Sixty C. jejuni biotype 1, 1 C. jejuni biotype 2, 19 C. coli strains were identified on the basis of the schema proposed by Skirrow and Benjamin (8,9). Using the schema outlined by Hebert et al. (3) 4 biotypes were identified among the 60 C. jejuni biotype 1 strains: biotype 3 with 27 strains, biotype 4 with 14 strains, biotype 1 with 13 strains, biotype 2 with 6 strains. Four biotypes were also identified among the 19 C. coli strains: biotype 8 with 14 strains, biotype 5 and 7 with 2 strains, biotype 6 with 1 strain. Of the 80 strains isolated, 64 (51 C. jejuni and 13 C. coli) were assayed for typing. Data obtained with a passive hemagglutination technique showed a great variety of serotypes, the most common of which were serotypes 1 (12.5%) and 2 (10.9%), found in the species C. jejuni biotype 1 only. Seventeen strains could not be typed, the greatest percentage of them having being found among biotype 8 (7 out of 10 tested). This study has thus revealed a wide variety of species, biotypes and serotypes among the thermophilic campylobacters isolated in the Sienese Area
Chemoresistances among 80 Campylobacter strains isolated from childhood gastroenteritis cases
No full textThe antimicrobial susceptibility of 80 thermophilic Campylobacter strains, 61 C. jejuni and 19 C. coli, isolated from childhood gastroenteritis cases has been studied. Gentamicin and chloramphenicol were effective against all strains; beta-lactams, except carbenicillin and ticarcillin, had on the whole little activity. 26.2% of strains proved to be resistant to tetracycline and 7.5% to erythromycin; erythromycin-resistance was found significantly more often in the species C. coli and always associated to clindamycin-resistance. The high prevalence of strains resistant to erythromycin suggests chloramphenicol and gentamicin as possible alternative drugs in the treatment of life-threatening Campylobacter infections
Isolamento e caratterizzazione dei batteri del bulbo esofageo della mosca mediterranea della frutta Ceratitis capitata
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