No abstract

This study described a group of strains obtained from a slaughter house in Mendoza, in terms of their pathogenic factors, serotype, antibiotype and molecular profile. Ninety one rectal swabs and one hundred eight plating samples taken from carcasses of healthy cattle intended for meat consumption were analyzed. Both the swab and the plate samples were processed to analyze the samples for the presence of virulence genes by PCR: stx1, stx2, eae and astA. The Stx positive strains were confirmed by citotoxicity assay in Vero cells. The isolates were subsequently investigated for their O:H serotype, antimicrobial susceptibility and molecular profile by Random Amplification of Polymorphic DNA (RAPD). Twelve E.coli strains were identified by their pathogenicity. Nine were from fecal origin and three from carcasses. Three strains carried the stx1 gene, three the stx2 gene, two carried eae and four the astA gene. The detected serotypes were: O172:H-; O150:H8; O91:H21; O178:H19 and O2:H5. The strains showed a similarity around 70% by RAPD. Some of the E.coli strains belonged to serogroups known for certain life-threatening diseases in humans. Their presence in carcasses indicates the high probability of bacterial spread during slaughter and processing.

Acacia aroma, native plant from San Luis, Argentina, is commonly used as antiseptic and for healing of wounds. The present study was conducted to investigate the in vitro cytotoxicity and genotoxicity of hot aqueous extract (HAE) and ethanolic extract (EE) of A. aroma. The cytotoxic activity was assayed by neutral red uptake assay on Vero cell. Cell treatment with a range from 100 to 5000 μg/mL of HAE and EE showed that 500 μg/mL and 100 μg/mL were the maximum noncytotoxic concentrations, respectively. The CC50 was 658 μg/mL for EE and 1020 μg/mL for HAE. The genotoxicity was tested by the single-cell gel electrophoresis comet assay. The results obtained in the evaluation of DNA cellular damage exposed to varied concentrations of the HAE showed no significant genotoxic effect at range of 1–20 mg/mL. The EE at 20 mg/mL showed moderate genotoxic effect related to the increase of the DNA percentage contained in tail of the comet; DNA was classified in category 2. At concentrations below 5 mg/mL, the results of cytotoxicity and genotoxicity of aqueous and ethanolic extracts of Acacia aroma guarantee the safety at cell and genomic level. However further studies are needed for longer periods including animal models to confirm the findings.

Central nervous system infections caused by Listeria monocytogenes produce a wide range of clinical symptoms which include cerebral abscesses, meningitis and nonmeningitic parenchymal cerebritis. A case study is presented of early listeriosis with signs of meningitis accompanied with septicemia and complicated with severe hydrocephalus.

The natural products derived from medicinal plants have proven to be an abundant source of compounds with antibacterial activity. The antibacterial activity of extracts of Azorella trifurcata and M. echegarayii was evaluated against strains of Staphylococcus aureus ATCC 43300, Pseudomonas aeruginosa ATCC 27853, Listeria monocytogenes CLIP 74902 and Escherichia coli ATCC 35218. Organic extracts were prepared using n-hexane, mixtures of n-hexane and ethyl acetate of increasing polarity and a mixture of ethyl acetate and methanol on flash chromatography. All the extracts of A. trifurcata showed antibacterial effects against grampositive bacteria (CIM between 0.5 and 2 mg/ml). Four extracts (100% n-hexane, 40:60/50:50 acetate: nhexane, 70:30 ethyl acetate: n-hexane and 2:98 methanol: ethyl acetate) of A. trifurcata showed antibacterial activity against gram-negative bacteria. M. echegarayii 2:98 methanol: ethyl acetate was active against all gram-negative and gram-positive bacteria (CIM between 1 and 2 mg/ml). The values of MBC of the extracts assayed were one or two times higher than corresponding MIC values. The discovery of organics extracts with antibacterial properties could contribute to the treatment of bacterial infections.