Search results for "bacteria."
showing 10 items of 4757 documents
Influence of nitroreductase and O-acetyltransferase on the mutagenicity of substituted nitrobenzothiophenamines in Salmonella typhimurium.
1999
The mutagenic activity of 17 substituted (aryl)(2-nitrobenzo[b]thiophen-3yl)amines has been evaluated in the Ames test with different isogenic strains of Salmonella typhimurium, that varied in their expression of nitroreductase and O-acetyltransferase. Active derivatives induced frameshift mutations in TA98 strain, and differences in the chemical structure resulted in up to 15-fold changes in mutagenic activity. The non-mutagenic compounds are the unsubstituted parent compound and derivatives with para-chloro, para-fluoro, para-diethylamino, meta-bromo and para-dimethylamino groups. They do not show any activity even in strains with higher level of nitroreductase or O-acetyltransferase. The…
Mutagenicity of N-substituted phenanthrene 9,10-imines in Salmonella typhimurium and Chinese hamster V79 cells.
1986
We previously showed that some (nonsubstituted) aziridines derived from polycyclic aromatic hydrocarbons (arene imines) elicit various mutagenic and genotoxic effects in bacteria and mammalian cells and that these arene imines are active at much lower concentrations than the corresponding epoxide analogues. In the present study, N-substituted derivatives of phenanthrene 9,10-imine were investigated. All 10 derivatives studied showed direct mutagenicity in Salmonella typhimurium TA100. Some of the compounds additionally exhibited weak effects in the strains TA98 and TA1537. Most N-substituted derivatives were weaker mutagens than unsubstituted phenanthrene 9,10-imine but stronger mutagens th…
Bacteriophage selection against a plasmid-encoded sex apparatus leads to the loss of antibiotic-resistance plasmids.
2011
Antibiotic-resistance genes are often carried by conjugative plasmids, which spread within and between bacterial species. It has long been recognized that some viruses of bacteria (bacteriophage; phage) have evolved to infect and kill plasmid-harbouring cells. This raises a question: can phages cause the loss of plasmid-associated antibiotic resistance by selecting for plasmid-free bacteria, or can bacteria or plasmids evolve resistance to phages in other ways? Here, we show that multiple antibiotic-resistance genes containing plasmids are stably maintained in bothEscherichia coliandSalmonella entericain the absence of phages, while plasmid-dependent phage PRD1 causes a dramatic reduction i…
Antibacterial effects of enniatins J1 and J3 on pathogenic and lactic acid bacteria
2011
Abstract Enniatins (ENs) are N -methylated cyclohexadepsipeptides, secondary metabolites produced by various species of the genus Fusarium . They are known to act as antifungal, antiyeast and antibacterial and to possess antiinsecticidal and phytotoxic properties. In this study we evaluated for the first time the antibiotic effect of pure fractions of EN J 1 and J 3 on several pathogenic strains and lactic acid bacteria. The ENs J 1 and J 3 were purified from the fermentation extract of Fusarium solani growth on solid medium of wheat kamut, using the technique of the low pressure liquid chromatography (LPLC) followed by a semipreparative liquid chromatography (LC). The purity and the struct…
Assessment of Salmonella and Listeria monocytogenes level in ready-to-cook poultry meat: Effect of various high pressure treatments and potassium lac…
2014
International audience; The objective of this study was to develop a probabilistic model in order to determine the contamination level of Salmonella and Listeria monocytogenes in ready-to-cook poultry meat, after a high pressure (HP) treatment. The model included four steps: i) Reception of raw meat materials, mincing and mixing meat, ii) Partitioning and packaging into 200-g modified atmosphere packs, iii) High pressure treatment of the meat, and iv) Storage in chilled conditions until the end of the shelf-life. The model excluded the cooking step and consumption at consumer's home as cooking practices and heating times are highly variable. The initial contamination level of Salmonella and…
Drug resistances in salmonella isolates from animal foods, Italy 1998–2000
2002
We investigated the distribution of serotypes and patterns of drug resistance of 206 strains of salmonella isolated in southern Italy in the years 1998–2000 from raw food of animal origin, faeces of food animals and animal feed. To improve knowledge of mobile genetic elements carrying the resistance genes, some molecular features were also investigated within isolates resistant to three or more antibiotics. A high proportion of isolates, 52.2% and 37.7%, respectively, belonging to both Typhimurium and other serotypes of animal origin, proved to be multidrug resistant. The DT104 complex specific multidrug pattern of resistance was quite infrequent among isolates other than Typhimurium, but r…
Chemical Composition and in Vitro Antimicrobial and Mutagenic Activities of Seven Lamiaceae Essential Oils
2009
Deeper knowledge of the potentiality of aromatic plants can provide results of economic importance for food and pharmacological industry. The essential oils of seven Lamiaceae species were analyzed by gas chromatography-mass spectrometry and assayed for their antibacterial, antifungal and mutagenic activities. Monoterpenes in the oils ranged between 82.47% (hyssop oil) and 97.48% (thyme oil), being mainly represented by oxygenated compounds. The antibacterial activity was evaluated against six pathogenic and five non-pathogenic bacterial strains. Oregano and thyme oils showed the strongest antibacterial activity against the pathogenic ones. The antifungal activity was evaluated against six …
Microbial contamination of milk and dairy products from restaurants in Spain
2009
This study was carried out to evaluate the microbiological quality of milk and some dairy products, including 95 lots of warm milk, 95 lots of milk conserved at room temperature, and 75 lots of dairy products collected from restaurants in Spain. According to the European microbiological criteria (92/46/EEC, 93/43/EEC, and Commission Regulation No. 2073/2005), 31% and 35% of the total examined lots exceed the adopted limits of mesophilic aerobic counts and Enterobacteriaceae, respectively. This may be due to incorrect handling of milk and dairy products and inadequate cleaning and sanitization of milk container. Further, 2% of all the lots examined were positive for the presence of Escherich…
Microbial evaluation of Spanish potato omelette and cooked meat samples in University restaurants.
2000
The focus of this study was to evaluate the microbial quality of Spanish potato omelette and cooked meat samples including pork loin, chicken croquettes, long pork sausage, chicken breast, and meatballs from University restaurants. Microbiological analyses of Spanish potato omelette and cooked meat samples resulted in aerobic plate counts from1.00 to 2.90 and from1.00 to 6.04 log10 CFU g(-1), respectively. Total coliforms ranged from3 to 43 most probable number (MPN) g(-1) and from3 to2,400 MPN g(-1) for Spanish potato omelette and meat products, respectively. Escherichia coli, coagulase-positive staphylococci, and Lancefield group-D streptococci were detected in 1.7%, 3.5%, and 12.9% of Sp…
Inhibition of foodborne pathogen bacteria by essential oils extracted from citrus fruits cultivated in Sicily
2012
Abstract The antagonistic activity of the essential oils (EOs) extracted by hydrodistillation from the fruit peel of several citrus genotypes (pummelo, grapefruit, orange, kumquat, mandarin and lemon) was evaluated against foodborne pathogen bacteria (43 strains of Listeria monocytogenes , 35 strains of Staphylococcus aureus and 14 strains of Salmonella enterica ). Five commercial EOs were used for comparison. Most of the EOs were more effective against the Gram-positive bacteria rather than Salmonella . EOs of lemon genotypes 14 and 15 showed the best results in terms of number of strains inhibited and width of the inhibition zone. The most susceptible strain of each species ( L. monocytog…