Carla Condò

Conjugation-Mediated Transfer of Antibiotic-Resistance Plasmids Between Enterobacteriaceae in the Digestive Tract of Blaberus craniifer (Blattodea: Blaberidae)

Abstract Cockroaches, insects of the order Blattodea, seem to play a crucial role in the possible conjugation-mediated genetic exchanges that occur among bacteria that harbor in the cockroach intestinal tract. The gut of these insects can be thought of as an effective in vivo model for the natural transfer of antimicrobial resistance plasmids among bacteria. In our study, we evaluated the conjugation-mediated horizontal transfer of resistance genes between Escherichia coli and other microorganisms of the same Enterobacteriaceae family within the intestinal tract of Blaberus craniifer Burmeister, 1838 (Blattodea: Blaberidae). Different in vivo mating experiments were performed using E. coli RP4 harboring the RP4 plasmid carrying ampicillin, kanamycin, and tetracycline resistance genes as the donor and E. coli K12 resistant to nalidixic acid or Salmonella enterica serovar Enteritidis IMM39 resistant to streptomycin as the recipients. The RP4 plasmid was successfully transferred to both recipients, producing E. coli K12-RP4 and S. Enteritidis IMM39-RP4 transconjugants. Conjugation frequencies in vivo were similar to those previously observed in vitro. The transfer of the RP4 plasmid in all transconjugants was confirmed by small-scale plasmid isolation and agar gel electrophoresis, suggesting that the intestinal tract of cockroaches is an effective in vivo model for natural gene transfer. Our results confirm that cockroaches allow for the exchange of antimicrobial resistance plasmids among bacteria and may represent a potential reservoir for the dissemination of antibiotic-resistant bacteria in different environments. These findings are particularly significant to human health in the context of health care settings such as hospitals.

Amoebicidal Effects of Three Bacteriocin like Substances from Lactic AcidBacteria against Acanthamoeba Polyphaga

We investigated the antiamoebic activity of three Bacteriocin Like Substances (BLS 39, BLS GS 54, BLS GS 16) produced by Lactic Acid Bacteria (LAB). The crude bacteriocins showed an amoebicidal effect against Acanthamoeba polyphaga, but with differences. BLS 39, produced by Lactobacillus pentosus, determined a prompt and progressive decrease of viable amoebal cell count, up to the end of the experiment (144 h), where the trophozoites were not detectable. A killing effect, but after a more prolonged contact time, was observed for BLS GS 54, produced by Lactobacillus paraplantarum, whereas the bacteriocin produced by Lactobacillus plantarum GS16 showed the lowest toxicity for A. polyphaga. For BLS GS 16 the maximum percentage of reduction in trophozoites count (45%) was obtained after 144 h, value much lower when compared to BLS GS54 and BLS 39, that showed values of 44,60% and 52,60% after only one hour of contact, with a maximum of 98% and 100% of non-viable cells, respectively, after 144 h. Morphological changes of the A. polyphaga cells as swollen cells, roundness and cellular lysis, were already observed after the first hours of contact with BLS and, at the end of the experiment, most of the cells were colored (blue), indicating their death. Currently there isn

Culture Compounds which are Able to Increase the Growth and the Production of Bacteriocins by Two Different LABS

prime;t evidence of BLS produced by LAB active against amoebas. In this study we have shown that all the three BLS secreted by the Lactic Acid Bacteria are endowed with amoebicidal effect against Acanthamoeba polyphaga, killing the protozoan with different effectiveness and at different times of contact.

Antimicrobial activity of spices essential oils and its effectiveness on mature biofilms of human pathogens

The exact composition of a culture medium used to grow bacteria and to provide the best conditions for the production of bacteriocins is very important. For this study two bacteriocins were used: enterocin 416 k1, produced by Enterococcus casselliflavus 416 K1, and nisin A, produced by Lactococcus lactis ATCC 11454; both Listeria monocytogenes inhibitors. The bacteriocin producers were cultured with various substances, including vitamins, salts, protein extracts and detergent, at three concentrations. In the first step, the individual substances were tested as additional nutrients, in order to evaluate their effects on the production of bacteriocins; subsequently the substances which were able to increase the production of bacteriocins were combined together, to investigate the presence of any synergism or antagonism. The most significant consideration that arises is the different behaviors of the microorganisms in response to the addition of the same substances. Furthermore, different results were seen depending on the concentrations of the substances. Bacteriocins have great potential in a variety of fields which means that large-scale production of these substances would be necessary. In this study we have tested different substances and combinations of substances which were able to increase the production of bacteriocins

In vitro evaluation of the amoebicidal activity of rosemary (Rosmarinus officinalis L.) and cloves (Syzygium aromaticum L. Merr. & Perry) essential oils against Acanthamoeba polyphaga trophozoites

Abstract The antibacterial activity of Pimpinella anisum L., Cinnamomum zeylanicum, Syzygium aromaticum, and Cuminum cyminum L. essential oils (EOs) against some common pathogenic microorganisms (Staphylococcus aureus ATCC 6538, Staphylococcus epidermidis ATCC 14990, Enterococcus faecalis ATCC 29212, Streptococcus pyogenes ATCC 1915, Escherichia coli ATCC 8739, Pseudomonas aeruginosa ATCC 27853, Aeromonas hydrophila ATCC 7966, Proteus mirabilis ATCC 10005, Klebsiella pneumoniae ATCC 13883, and Candida albicans ATCC 10231) and their biofilms was studied. The EOs inhibitory effects were evaluated by both Agar Well Diffusion assay and Minimum Inhibitory Concentration (MIC) determination. The most active EOs, cinnamon and cloves, were also tested on 18, 24, 48, 72 hours mature biofilms. Cinnamon and cloves exhibited the best results showing a significant activity against all the tested bacteria. Concerning biofilm, results suggest that Cinnamomum zeylanicum oil may be a useful approach to impair the biofilm produced by the tested Gram-negative bacteria. Graphical Abstract

Isolation of two lactobacilli, producers of two new bacteriocin-like substances (BLS) for potential food-preservative use

Abstract Several species of the genus Acanthamoeba cause human diseases. Treatment of infections involves various problems, emphasising the need to develop alternative antiprotozoal agents. We studied the anti-amoebic activity of Essential Oils (EOs), derived from rosemary (Rosmarinus officinalis L.) and cloves (Syzygium aromaticum L. Merr. & Perry), against Acanthamoeba polyphaga strain. The amoebicidal activity of cloves and rosemary EOs was preliminary demonstrated by the morphology change (modifications in the cell shape, the presence of precipitates in the cytoplasm, autophagic vesicles, membrane blends) of the treated trophozoites. The cell-counts, carried out after staining trophozoites with a Trypan blue solution, revealed that both EOs were active in a dose-dependent manner and in relation to the exposure time. This activity was evident after few hours, with encouraging results obtained in particular with cloves EO, able to act at the lower concentrations and after 1 h, probably for its high eugenol content (65.30%).

A bacteriocin-like substance produced from Lactobacillus pentosus 39 is a natural antagonist for the control of Aeromonas hydrophila and Listeria monocytogenes in fresh salmon fillets

The fermentation of meat by lactic acid bacteria (LAB) is a traditional practice in many countries of Europe. LAB are already used for probiotic use and/or their bacteriocins can be used as a food preservative. 21 LABs were isolated from ham samples and identified by PCR; in particular, L. plantarum-GS16 and L. paraplantarum-GS54 were identified as the best bacteriocin-like substance (BLS) producers, active against spoilage and pathogenic bacteria, Gram negative included. In these strains, the presence of virulence factors, antibiotic and gastrointestinal resistance was investigated. The kinetics of growth and the BLS biosynthesis was also evaluated at different pH values. Finally, both bacteriocin substances were partially characterized and included in the IIa class of Klaenhammer; as a potential application, both BLSs can be successfully used as food preservatives.