Evaluation of the natural virucidal activity of teas for use in the phage amplification assay.

Many natural products have intrinsic antimicrobial activity. In this study we have examined infusions from nine types of loose-leaf tea for their ability to inactivate bacteriophage, for use as an alternative to plant extract in a phage-based Salmonella detection assay. The results demonstrated that tea infusions, either freshly prepared or stored at 4 degrees C had virucidal action against two phages, Felix 01 and P22. Crucially, for use in the detection assay, there was no antibacterial effect of the virucide on the target bacteria. Therefore, tea was a good candidate to replace pomegranate as the virucidal agent in the phage amplification assay.

A comparison of three modelling approaches for quantitative risk assessment using the case study of Salmonella spp. in poultry meat.

A comprehensive review of both the scientific literature and industry practices was undertaken to identify and quantify all sources of contamination throughout the entire poultry meat production chain by Salmonella spp. This information was used to develop a quantitative risk assessment (QRA) model for Salmonella in the production chain from the breeder farm to the chilled carcass. This was subsequently used as the basis on which to compare the merits of three approaches to QRA modelling in such systems. The original model used a Bayesian Network (BN). The second method was a Markov chain Monte Carlo (MCMC) approach, a numerical Bayesian technique which retained a similar network structure but allowed further development, such as the separation of variability and uncertainty. The third method was a more detailed simulation model. The BN responds immediately to changes, such as entering evidence, because it does not use simulation and can propagate information from any point in the network to all others by Bayesian inference. However, it requires all the variables to be discrete, which introduces errors if continuous variables have to be discretized. These errors can accumulate. The MCMC approach does not require discrete variables while retaining some of the properties of the BN model, such as the ability to draw inferences from evidence. Finally, the simulation offers greater flexibility, such as consideration of the individual carcass, but may be more complex to implement as a result and sacrifices the ability to propagate evidence.

Effect of a single dose of Saccharomyces cerevisiae var. boulardii on the occurrence of porcine neonatal diarrhoea.

Piglet neonatal diarrhoea is an important issue in modern pig production and is linked to increased mortality and poor growth rates, affecting long-term pig health, increasing use of medication and cost of production. Saccharomyces cerevisiae var. boulardii (SB) is a probiotic yeast with documented clinical efficacy in the prevention and treatment of diarrhoeal diseases in humans. The objectives of the current study were to evaluate the effect of SB on occurrence and severity of neonatal diarrhoea in piglets, mortality and growth rate. Forty-six litters (606 piglets) were randomly allocated to a control or SB treatment (n=23 per treatment). Within 24 h of farrowing, piglets assigned to the SB treatment received a single oral dose of a paste containing 3.3×10(9) CFU of SB CNCM I-107(9). Piglets from the control litters received a placebo paste. Piglet weight, mortality and diarrhoea were recorded up to day 7 of age. It was shown that numbers of diarrhoea days were significantly correlated with increased mortality rate and reduced weight gain (P<0.05). SB treatment had no effect on growth or mortality in diarrhoeic litters. However, SB-supplemented litters had significantly lower faecal scores, indicating firmer faeces (P<0.01) and fewer numbers of diarrhoeic days (P<0.01) during the 1(st) week of life. Reduction in the number of diarrhoeic litters compared with the control group was observed following the probiotic administration (P<0.05). These results highlight the detrimental effects of neonatal diarrhoea on pre-weaning performance and suggest that SB, by reducing diarrhoea duration and severity, has the potential of improving enteric health in the early stages of life in pigs.

Inclusion of detergent in a cleaning regime and effect on microbial load in livestock housing.

Determining effective cleaning and disinfection regimes of livestock housing is vital to improving the health of resident animals and reducing zoonotic disease. A cleaning regime consisting of scraping, soaking with or without detergent (treatment and control), pressure washing, disinfection and natural drying was applied to multiple pig pens. After each cleaning stage, samples were taken from different materials and enumerated for total aerobic count (TAC) and Enterobacteriaceae (ENT). Soaking with detergent (Blast-Off, Biolink) caused significantly greater reductions of TAC and ENT on metal, and TAC on concrete, compared with control. Disinfection effect (Virkon S, DuPont) was not significantly associated with prior detergent treatment. Disinfection significantly reduced TAC and ENT on concrete and stock board but not on metal. Twenty-four hours after disinfection TAC and ENT on metal and stock board were significantly reduced, but no significant reductions occurred in the subsequent 96 hours. Counts on concrete did not significantly reduce during the entire drying period (120 hours). Detergent and disinfectant have varying bactericidal effects according to the surface and bacterial target; however, both can significantly reduce microbial numbers so should be used during cleaning, with a minimum drying period of 24 hours, to lower bacterial counts effectively.

Characterization of dominant microbiota of a Ghanaian fermented milk product, nyarmie, by culture- and nonculture-based methods.

AIMS: To characterize the predominant micro-organisms in a Ghanaian traditional fermented dairy product, nyarmie, made from cows' milk, using both culture- and nonculture-based methods. METHODS AND RESULTS: Samples of nyarmie were analysed from three production sites in Accra, by determining the counts on selective culture media. The microbial diversity occurring in nyarmie was also evaluated by 16S/18S ribosomal DNA PCR amplification and denaturing gradient gel electrophoresis. Results showed that nyarmie contained lactococci and lactobacilli in the range of 10(8) and 10(10) CFU ml(-1), respectively, and yeasts at around 10(7) CFU ml(-1). The pH ranged between 3.49 and 4.25. The predominant lactic acid bacteria (LAB) in nyarmie were Leuconostocmesenteroides ssp. mesenteroides, Streptococcus thermophilus, Lactobacillus delbrueckii ssp. bulgaricus, Lact.helveticus, Lact. delbrueckii ssp. lactis and Lactococcus lactis, while Saccharomyces cerevisiae was the predominant yeast species. Lactobacillus delbrueckii ssp. delbrueckii was not detected by cultivation but its predominance was revealed by PCR-DGGE analysis. CONCLUSIONS: The flora in products from different producers varied in the LAB composition present and may result in variations in product quality. SIGNIFICANCE AND IMPACT OF THE STUDY: Development and use of starter cultures for nyarmie may be beneficial in improving the consistency of product quality.

Correlation of Campylobacter bacteriophage with reduced presence of hosts in broiler chicken ceca.

Campylobacter jejuni and Campylobacter-specific bacteriophage were enumerated from broiler chicken ceca selected from 90 United Kingdom flocks (n = 205). C. jejuni counts in the presence of bacteriophage (mean log(10) 5.1 CFU/g) were associated with a significant (P < 0.001) reduction compared to samples with Campylobacter alone (mean log(10) 6.9 CFU/g).

Enzymes from isolates of Pseudomonas fluorescens involved in food spoilage.

AIMS: Psychrotrophic Gram-negative bacteria, such as Pseudomonas species, pose a significant spoilage problem in refrigerated meat and dairy products due to secretion of hydrolytic enzymes, especially lipases and proteases. This study characterized the enzymes produced by strains of Pseudomonas fluorescens isolated from pasteurized milk. METHODS AND RESULTS: Thirty-seven isolates of Ps. fluorescens from skimmed, semiskimmed and whole milk were all shown to be proteolytic and lipolytic on casein and tributyrin agar, respectively. The highest level of protease production by one isolate, SMD 31, from skimmed milk was in minimal salts medium containing 1 mmol x l(-1) calcium chloride at 20 degrees C. The proteases belonged to the class of metallo-proteases, as there was no residual activity with 10 mmol x l(-1) EDTA. They were heat stable and retained activity even after treatment at 121 degrees C for 20 min. One protease of 45-48 kDa was detected in unconcentrated supernatant fluid samples but, in three isolates from different milk sources, five proteases with molecular masses between 28 and 48 kDa were detected on a 12% zymogram casein gel following ultrafiltration. Attempts to purify the lipases proved unsuccessful. CONCLUSIONS: The characteristics of the major protease of 45-48 kDa correspond to those of proteases described for other Pseudomonas species isolated from a range of environments. However, the smaller proteases have not been described previously. SIGNIFICANCE AND IMPACT OF THE STUDY: In the absence of ultrafiltration the presence of the minor protease species may be missed and they may act as contaminants of the major protease in unpurified or semipurified samples.

Cross-contamination of carcasses and equipment during pork processing.

AIMS: The cross-contamination events within a commercial pork processing line were examined by a combination of ERIC-PCR DNA fingerprinting of Escherichia coli and plate counts. METHODS AND RESULTS: Sponge sampling of environmental surfaces and carcasses was performed over an 8-h processing period. Prior to the start of processing the scraper and dry polisher blades were found to harbour substantial Enterobacteriaceae and Escherichia coli populations. From plate count data the key cross-contamination site for the transfer of bacteria between carcasses occurred during evisceration. However, DNA fingerprints of representative E. coli isolates identified that genotypes initially present on the scraper/dry polisher became distributed on wet polisher blades, band-saw and butcher's hands despite a singeing step being performed post dry polishing. A high proportion of E. coli on post-eviscerated carcasses could be traced to down-stream (pre-singe) environmental contact surfaces. CONCLUSIONS: DNA fingerprinting has demonstrated that E. coli and potential enteric pathogens can be transferred between pork carcasses throughout the processing line. In this respect scalding and singeing cannot be relied upon to control cross-contamination of enteric bacteria between carcasses. SIGNIFICANCE AND IMPACT OF THE STUDY: Sole reliance on indicator organism counts to identify cross-contamination events as currently advocated is limited.

Longitudinal study of Campylobacter jejuni bacteriophages and their hosts from broiler chickens.

A longitudinal study of bacteriophages and their hosts was carried out at a broiler house that had been identified as having a population of Campylobacter-specific bacteriophages. Cloacal and excreta samples were collected from three successive broiler flocks reared in the same barn. Campylobacter jejuni was isolated from each flock, whereas bacteriophages could be isolated from flocks 1 and 2 but were not isolated from flock 3. The bacteriophages isolated from flocks 1 and 2 were closely related to each other in terms of host range, morphology, genome size, and genetic content. All Campylobacter isolates from flock 1 were genotypically indistinguishable by pulsed-field gel electrophoresis (PFGE). PFGE and multilocus sequence typing indicated that this C. jejuni type was maintained from flock 1 to flock 2 but was largely superseded by three genetically distinct C. jejuni types insensitive to the resident bacteriophages. All isolates from the third batch of birds were insensitive to bacteriophages and genotypically distinct. These results are significant because this is the first study of an environmental population of C. jejuni bacteriophages and their influence on the Campylobacter populations of broiler house chickens. The role of developing bacteriophage resistance was investigated as this is a possible obstacle to the use of bacteriophage therapy to reduce the numbers of campylobacters in chickens. In this broiler house succession was largely due to incursion of new genotypes rather than to de novo development of resistance.