ABSTRACT
Background@#Staphylococcus aureus is one of the main microorganisms that causes bovine mastitis, and its well-known virulence characteristics and interactions with the environment are used to aid the design of more efficient therapies. @*Objectives@#To determine whether the virulence traits, such as antibiotic resistance and biofilm-forming and internalization abilities, of S. aureus isolated from bovine mastitis are related to dairy production system types. @*Methods@#The study was performed in the Mexican states of Guanajuato and Michoacan.Semi-intensive dairy farms (SIDFs) and family dairy farms (FDFs) (454 and 363 cows, respectively) were included. The 194 milk samples from mastitis affected quarters were collected and 92 strains of S. aureus were isolated and identified by biochemical and molecular tests. Antibiotic resistance, biofilm and internalization assays were performed on 30 randomly selected isolated strains to determine virulence traits, and these strains were equally allocated to the 2 dairy production systems. @*Results@#All 30 selected strains displayed a high degree of resistance (50%–91.7%) to the antibiotics tested, but no significant difference was found between SIDF and FDF isolates. S.aureus strains from SIDFs had an average biofilm forming capacity of up to 36% (18.9%–53.1%), while S. aureus strains from FDFs registered an average of up to 53% (31.5%–77.8%) (p > 0.05).Internalization assays revealed a higher frequency of internalization capacity for strains isolated from FDFs (33.3%) than for those isolated from SIDFs (6.7%) (p > 0.05). fnbpA gen was detected in 46.6% of FDF strains and 33.3% of SIDF strains, and this difference was significant (p < 0.05). @*Conclusions@#Our findings show that the virulence traits of S. aureus isolates analyzed in this study, depend significantly on several factors, such as phenotype, genotype, and environmental conditions, which are significantly related to dairy production system type and daily management practices.
ABSTRACT
El objetivo de este trabajo fue construir y presentar evidencia preliminar sobre la validez y confiabilidad de una escala para medir la actitud frente a las personas en situación de discapacidad, tanto física como mental, en instituciones de educación superior. A partir de una muestra de 100 participantes, se validó una escala de 10 ítems con formato Likert, con una consistencia interna evidenciada a partir de un coeficiente alfa de Cronbach de 0,805 y 2 factores que explican un 51,024% de la varianza total y presentaron una interpretación coherente con la definición del constructo. Los resultados muestran que el instrumento propuesto tiene características psicométricas suficientes como para continuar con el estudio de su validación.
The objective of this investigation was construct and present preliminary evidence of the validity and reliability of an attitude scale towards people in situation of disability in higher educational institutions. From a sample of 100 participants, was validated a scale of 10 items in a Likert format, with an internal consistency evidenced from an alpha of Cronbach coefficient of 0,805 and 2 factors explaining an 51,024% of the total variance that presented a consistent interpretation with the definition of the construct. The results show that the proposed instrument has enough psychometric characteristics to continue the study of validation.
ABSTRACT
A site evaluation was made for a low-lying property in an old river levee/marsh association, used marginally for cattle raising, which was contaminated due to historical practices. Contamination was related to geomorphology: the lowest areas contained 79% of the contaminated samples. Other contaminated samples were all rear access roads [probable intentional dumping]. There were no samples in the higher, levee areas away from roads with hydrocarbon concentrations above 3,000 mg/kg. Medium and high impact levels, corresponding to average hydrocarbon concentrations of 13,400 mg/kg and 109,700 mg/kg, respectively, were found in 28% and 27% of the property area. The medium impact level was predicted to have a reduced pasture production potential of- 50% while at the high impact level practically no pasture production was predicted. Toxicological risk to cattle is present in only 12% of the sample points although almost all of these are in very marshy areas not apt for cattle raising. Because the hydrocarbons at this tropical site are very weathered, acute toxicity was not related to hydrocarbon concentration. Although slightly more than half of the property has hydrocarbon concentrations above the permissible limit, only about one-third of the contaminated area is apt for cattle raising. This study, based on hydrocarbon distribution related to site geomorphology, soil toxicity bioassay, risk assessment to cattle and evaluation of pasture production allowed to made a more accurate assessment and definition of future use of the site. These criteria could be used for diagnostic studies of sites with similar tropical conditions
Subject(s)
Hydrocarbons , Cattle , Petroleum , Risk AssessmentABSTRACT
Conventional and experimental methods were studied for the remediation of petroleum contaminated sediments from a dam previously used to collect acid run-off from a sulfur mine. The man-made lake had been neutralized, but bentonite rich sediments remained contaminated with very weathered hydrocarbons [sediments with 50,000-60,000 mg/kg Total Petroleum Hydrocarbons were used in this study]. Biostimulation, bioaugmentation [with native microorganisms] and chemico-biological stabilization, all resulted in similar reductions [14-16%] in the TPH concentration over a three month period. The land farming treatments resulted in variable reductions in toxicity, ranging from nil to complete, while the chemico-biological stabilization treatment, not only eliminated acute toxicity but also resulted in a slight stimulation [103-109%] of the test organism in the bioassay [Microtox]. All three treatments reduced polyaromatic hydrocarbons of probable carcinogenicity to below or nearly below the Mexican norms, reduced Toxic Characteristic Leaching Proceedure leachates to <1 mg/L, and left the material in a pH range of 7.0-7.8. The chemico-biological stabilization has the advantage of only requiring initial mixing of the chemical and organic reagents instead of daily aeration, thereby reducing operating costs. This method is also able to treat very difficult sites at low cost, relying on biological humification processes which are accelerated in a humid tropical and semitropical environment. The total unit cost of the chemico-biological stabilization treatment was estimated to be 60% of that for land farming in the southern Gulf of Mexico region
Subject(s)
Biodegradation, Environmental , Petroleum , Hydrocarbons , Soil , Tropical ClimateABSTRACT
Two sites from a humid tropical environment were studied with respect to soil water repellency caused by hydrocarbon contamination. Samples were analyzed for water repellency [molarity ethanol droplet method], total petroleum hydrocarbons, acute toxicity [Microtox] and field capacity. At both sites, water absorption times were logarithmically related to the molarity ethanol drop value [R > 0.95]. In a sandy soil collected from an old separation battery which had been bioremediated, field capacity was strongly related to hydrocarbon concentration [R = 0.998]; and at 10,000 mg/kg the calculated field capacity was only 75% of the baseline. Water repellency was related to hydrocarbon concentration asymptotically and plant growth limiting values [severity > 3.0] were observed at low concentrations [2,400 mg/kg], even though toxicity was at, or below background levels. Bioremediated soil at this site had hydrocarbon concentrations only 1,300 ppm above background, but had extreme water repellency [severity = 4.6 - 4.7]. Soil water repellency was also measured in a clayey, organic rich floodable soil, in a multiple pipeline right-of-way colonized by water tolerant pasture and cattails. Water repellency was associated with total petroleum hydrocarbon concentration [R = 0.962], but was not related to field capacity or toxicity. In this low-lying site, the water repellency observed in the laboratory is probably not representative of field conditions: samples taken at the end of the ten week dry season [and only four days before the first rains] showed ample moisture [> 80% field capacity]