Search

Aims: To investigate the prevalence of Clostridium difficile encountered during sewage treatment and in water sources into which treated effluent was directly or indirectly discharged. Methods and Results: Samples from wastewater treatment plants (WWTPs) and rivers were collected and then enriched for Cl. difficile. Each of the isolates was subjected to toxinotyping and DNA typing using ribotyping, in addition to pulse-field gel electrophoresis. Cl. difficile was isolated from 92% (108/117) of the raw sludge and 96% (106/110) of the anaerobic digested sludge samples from two Ontario WWTPs. The pathogen was recovered from 73% (43/59) of dewatered biosolids and effluent discharge, in addition to river sediments 39% (25/64). Ribotype 078 (commonly associated with Community Acquired infections) was recovered from raw sewage (19%; 21/108), digested sludge (8%; 8/106), biosolids (35%; 15/43) and river sediments (60%; 15/25). Conclusions: Clostridium difficile is commonly encountered in raw sewage and survives the wastewater treatment process. The pathogen can then be disseminated into the wider environment via effluent and land application of biosolids. Significance and Impact of the Study: The study has illustrated the wide distribution of toxigenic Cl. difficile in WWTPs and river sediments although the clinical significance still requires to be elucidated. [ABSTRACT FROM AUTHOR]

Background: There is interest in applying bacteriophages to control Salmonella in pig production and pork processing. The following reports on the prevalence of Salmonella infecting bacteriophages within Ontario pig farms and associated with the holding area of a pork slaughterhouse., Results: Salmonella infecting bacteriophages were present in 30 and 28 of the effluent manure samples collected from 36 farms using S. Typhimurium DT104 or S. Heidelberg as host cell respectively. Bacteriophages were recovered in 95-100% of the 48 samples taken from holding pens within a high capacity slaughterhouse over a 12 month period. Bacteriophages isolated from farms exhibited similar host ranges which differed to that of slaughterhouse isolates. Salmonella (n = 21) from the slaughterhouse were susceptible to the endogenous bacteriophages. Despite being susceptible to the resident phages, the Salmonella populations were found to be genetically stable with the same genotypes being recovered over successive visits. Salmonella isolated from the farms were frequently resistant to the endogenous phages., Conclusions: Bacteriophages are prevalent in the pig slaughterhouse environment although they do not have a significant impact on the genetic structure of Salmonella populations. However, there was evidence that the Salmonella population structure on farms is influenced by the presence of infecting phages., (Copyright © 2010 Society of Chemical Industry.)

The objective of this study was to determine whether the shedding and antibody titre to Salmonella was lower for pig herds provided liquid-feed compared to those on traditional dry rations. Twenty liquid-feeding farms and 61 dry-feeding farms were selected. The amount of antibodies to Salmonella in sera from 15 finisher pigs on each of 80 Ontario swine farms was analyzed by means of enzyme-linked immunosorbent assay (ELISA). In addition, the presence of Salmonella on the 20 liquid-feeding farms and 21 of the dry-feeding farms was assessed by culture of 15 fecal samples taken directly from finisher pigs and five pooled pen-fecal samples at each farm. A cut-off of OD% 10 was used. The Salmonella sero-prevalence differed between the two groups of farms. At least one pig tested sero-positive on 98% of the dry-feeding farms and 84% of the liquid-feeding farms (P<0.05). A multi-variable mixed linear regression model with the farm as a random variable and farm factors as the fixed effects was fitted. Crude optical density (OD) of the individual pig was considered as the continuous dependent variable. Dry-feeding and antimicrobial daily usage was associated with crude OD (P<0.05). In addition, crude OD increased with increasing herd size (P<0.05). Salmonella was isolated from 25 out of 420 fecal samples (6%) from dry-feeding farms compared to three out of 400 samples (0.8%) from liquid-feeding farms. Eight of the dry-feeding farms (38%) tested positive compared to only three of the liquid-feeding farms (15%). Salmonella was also recovered from the pen environment on five dry-feeding farms but were not isolated from the facilities using liquid-feeding. Salmonella Typhimurium was isolated from four farms in the dry-feed group and on one farm with liquid-feeding. The one S. Typhimurium isolate from the liquid-feeding farm exhibited no antimicrobial resistance, but those from dry-feeding farms were resistant to four or more antimicrobial agents. The results of the logistic regression, with farm as a random effect showed that dry-feeding [OR=2.7 (1.1-15.1)] and continuous flow system [OR=2.3 (1.2-12.7)] increased risk of finding Salmonella in the individual pig. These findings indicate that liquid-feeding and all-in all-out management of the grower-finisher barns can reduce the Salmonella prevalence.