Bacteriological characterization of wastewater samples obtained from a primary treatment system on a small scale swine farm.

This study was carried out in order to quantify enteric bacteria and identify the presence of Salmonella spp., Escherichiacoli, Clostridiumperfringens and Erysipelothixrhusiopathiae in the liquid fraction of excreta generated from a small scale swine farm by means of a primary treatment system, consisting of the separation of solids and the sedimentation of liquids. Samples were collected at the following stages of the treatment: collection basin (CB), liquid obtained from a solids separator (SLF) and liquid from the sedimentation basin (SB). In each sample, enteric bacteria (cfu/g wet weight) and E. coli were quantified, Salmonella spp. was isolated and typified, and C. perfringens, and E. rhusiopathiae were isolated. No significant differences (p>0.05) were found in the enteric bacteria and E. coli population levels at any treatment stage. S.choleraesuis was found in 20% of CB samples analyzed, 40% of SLF samples and 30% of SB samples. C. perfringens was isolated from SLF and SB. E. rhusiopathiae was not isolated (below the minimum detection limit). Results suggest that primary treatment does not reduce the amount of enteric bacteria, or eliminate Salmonella spp., E. coli and C. perfringens. Therefore, it is necessary to apply additional treatments to allow safe use of the liquid obtained in the farm.

Isolation of Salmonella spp. from liquid and solid excreta prior to and following ensilage in ten swine farms located in central Mexico.

A study was carried out to define selected bacteriological characteristics of residues from 10 swine farms, 5 with or without prior clinical enteric disease (PCED) and to determine the effect of ensilage on the bacteria present in the solid fraction. At each farm, samples were taken from the sedimentation basin (SB), the solid fraction (SF), and the liquid fraction (LF). For each sample, CFU/g for enteric bacteria were quantified; Salmonella spp. were isolated and typified. Solid phase samples from each farm were used to prepare the ensilage, with a mixture of solids (80%), sorghum (12%) and molasses (8%). The quantity of enteric bacteria was significantly greater in farms without PCED (P < 0.05). Salmonella enterica were isolated from 8/10 of the farms with and without PCED; in 8 from SB; in 6 from LF; and in 5 from SF. Enteric bacteria were not isolated from silage, therefore, ensilage may be an alternative treatment for excreta that allows the elimination of pathogens such as Salmonella spp.

Prevalence of Escherichia coli O157 in cattle and swine in central Mexico.

Escherichia coli O157:H7 is a foodborne pathogenic bacterium that can reside undetected in the gastrointestinal tract of cattle because colonization by this bacterium is asymptomatic. Recent research has indicated that swine can carry and transmit this pathogen as well. The development of more advanced and sensitive detection techniques has improved the limit of detection and increased sensitivity for this important pathogen. This study was undertaken to determine the prevalence of E. coli O157 in cattle and swine in Mexico with the more sensitive detection technique of immunomagnetic bead separation. Samples (n = 60 per farm) were taken from four cattle and four swine farms (n = 240 cattle samples, n = 240 swine samples) located throughout central Mexico in October 2001. The prevalence of E. coli O157 was found to be only 1.25% on cattle farms and 2.1% on swine farms. The prevalence in cattle in this study is lower than that reported in the United States and could be related to the lower reported prevalence of E. coli O157 in humans in Mexico. However, further research is needed to verify prevalence throughout other regions of Mexico, as well as prevalence during other seasons of the year.

Persistence of Escherichia coli, Salmonella choleraesuis, Aujeszky's Disease virus and Blue Eye Disease virus in ensilages based on the solid fraction of pig faeces.

AIMS: This study was carried out to determine the survival time of Escherichia coli, Salmonella choleraesuis, Aujeszky's Disease virus and Blue Eye Disease virus in ensilages based on the solid fraction of pig faeces. METHODS AND RESULTS: The four micro-organisms were inoculated into microsilos based on the solid fraction of pig faeces, sorghum and molasses. They were left for 0, 7, 14, 28 and 56 days, after which the state of each microsilo was evaluated, and isolation of the inoculated agents was attempted. The four inoculated agents were isolated only on day 0 of ensilage. The viral agents were identified through the cytopathic effect and fluorescence. CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY: It is concluded that ensilages based on the solid fraction of pig faeces appear to reduce the risk of the transmission of the agents inoculated in this study and help to reduce the environmental impact by using the solid in animal feed.