Prevalence and characterization of extended-spectrum beta-lactamase-producing Enterobacteriaceae in food-producing animals in Northern Italy

The aim of this study was to assess the production of extended spectrum beta-lactamases (ESBL) in 56 strains of Enterobacteriaceae, obtained from 100 rectal swabs of farm animals, and to evaluate the horizontal transfer capacity of the genetic determinants of resistance. The ESBL-positive strains were confirmed by phenotypic testing, confirmed by PCR and DNA sequence analysis. The localization of beta-lactamase genes was established by conjugation experiments. Of the 56 analyzed strains, 20 (36%) resulted positive for ESBL production by the double-disk synergy test, and belonged to Escherichia coli 15 (75%) and Klebsiella ozaenae 5 (25%) species. Molecular analysis showed that all ESBL-producing isolates possessed genes encoding for TEM-type enzymes and/or CTX-M. The conjugation assays yielded positive results, thus denoting a plasmidic localization of the genes. This study highlights the high percentage of ESBL-positive Enterobacteriaceae and the mobility of the responsible genes. Gene mobility implies highly negative consequences in terms of drug therapy because of the spread of antibiotic resistance

Antibacterial activity of tymol-doped acrylic coatings for bioactive food packaging.

This study is devoted to investigate the possibility to prepare thymol-doped antibacterial coatings. For this purpose, thymol has been dissolved in different amounts into a liquid photo-crosslinkable diacrylic resin, and the antibacterial activity of thymol-containing plastic discs has been evaluated against Listeria monocytogenes, Escherichia coli (gram-negative) and Staphylococcus aureus (gram-positive) by qualitative modified agar diffusion assays. The antibacterial activity of thymol-containing coatings is expected to depend on the ability of thymol to move to the surface and to be released in the surrounding medium. In order to investigate this aspect, after photo-curing, release tests have been performed by putting thymol-containing plastic discs in contact with different liquid simulating fat (n-hexane), acqueous (water) and intermediate polarity (MeOH and EtOH) media

Thymol-doped antibacterial coatings for food active packaging.

Thymol can be easily derived from plants (thyme and oregano) and is a FDA approved food additive commercially available at low price. It has been recognized to have antibacterial and antioxidant properties, and is registered in the list of flavourings that do not present risks to the health of the consumers. This interesting properties can in principle be exploited also to prepare functional coatings, which in turn can be applied to packaging materials to obtain antibacterial and antifungi packagings. This study is devoted to investigate the possibility to prepare thymol-doped antibacterial coatings. For this purpose, thymol has been dissolved in different amounts into a liquid photo-crosslinkable diacrylic resin and the antibacterial activity has been evaluated against gram-positive and gram-negative bacterias by qualitative modified agar diffusion assays. The rate of diffusion of thymol from the doped-resins have been performed with different liquid simulating fat (n-hexane), acqueous (water) and intermediate polarity (MeOH, Ethyl Acetate and EtOH) media

Valutazione dell\u2019attivit\ue0 antagonista nei confronti di L.monocytogenes di un coating ibrido applicato su polietilene ottenuto mediante incorporazione di Enterocina 416K1

Viene studiata e descritta l\u2019attivit\ue0 antagonista nei confronti di L.monocytogenes, di ricoprimenti per film di polietilene costituiti da un materiale ibrido organico-inorganico nanostrutturato preparato mediante tecnologia sol-gel e contenente Enterocina 416K1

Anti-listerial activity of coatings entrapping living bacteria.

Polyvinyl alcohol (PVOH) based coatings entrapping either living bacteriocin-producer Enterococcus casseliflavus IM 416K1 bacteria or Enterocin 416K1 have been prepared and applied to poly(ethylene terephthalate) (PET) films. The antimicrobial activity of coated PET films was evaluated against Listeria monocytogenes NCTC 10888 by qualitative agar diffusion assays and by direct contact with artificially contaminated food samples (w\ufcrstel and seasoned cheese) stored at 4 \ub0C and 22 \ub0C. Anti-listerial activity of both coatings was observed for both tests. However, the live-enterococcus doped coatings showed a much more remarkable anti-listerial activity than enterocin doped ones. Interestingly, live-enterococcus doped coatings lead to a strong decrease of L. monocytogenes viable counts even at 22 \ub0C, indicating that they are able to contrast efficiently the fast L. monocytogenes growth occurring at this temperature in w\ufcrstel samples. In this respect, they can be considered smart coatings, being able to be responsive towards an accidental rise of temperature during food storage. The capability of bacteria to survive for a long time can also assure a long lasting antibacterial activity. Coatings entrapping living Enterococcus casseliflavus IM 416K1 can produce Enterocin 416K1, a bacteriocin having a strong antibacterial activity towards Listeria monocytogenes . Such a kind of coating shows a long lasting antimicrobial activity and can behave like a smart coating, being able to be responsive to an accidental rise of temperature during food storage

Detection and partial characterization of a bacteriocin-like substance produced by Lactobacillus fermentum CS57 isolated from human vaginal secretions

Lactobacilli (150) from human vaginal secretions were tested for the production of antimicrobial substances which can provide a physiological defense against the pathogenic microorganisms in the vaginal area. Sixteen of the isolates (10.6%) showed antibacterial activity against one or several closely related microorganisms used as indicators. Lactobacillus fermentum CS57 was the best producer and secretes a bacteriocin-like substance (BLS) with antagonistic activity against Streptococcus agalactiae and Candida albicans. The compound was susceptible to the proteolytic enzymes and was heat labile. The mode of action was identified as bactericidal. The crude activity of the L. fermentum CS57 BLS was linked to a substance with a molecular weight larger than 30 kDa. Plasmid analysis of L. fermentum CS57 revealed the presence of a plasmid band with molecular weight of 54.7 kb. All L. fermentum CS57 non-producer variants (BLS) obtained by curing experiments, showed loss of plasmid band and were susceptible to the BLS of the original strain. Therefore antimicrobial activity and immunity production seem to be linked to genes located on that same plasmid. Taking into account our results, L. fermentum CS57 could be considered a candidate for potential use as probiotic for the prophylaxis of vaginal human infection