Comparison of real-time PCR and nested PCR based on the HlyA gene for the detection of Listeria monocytogenes. Application on cheese samples

The aim of the present study was to compare the performance of a nested polymerase chain reaction (nPCR) and a real-time PCR based on the amplification of the HlyA gene from Listeria monocytogenes using a plasmid DNA standard. Nested PCR was developed with an internal amplification control (IAC). Both techniques were validated in soft cheese samples by comparing their results with the results of the microbiological reference method ISO 11290-1:2017. Cheese samples artificially contaminated with 3.5 to 3,500 UFC/25 g were processed by ISO 11290-1:2017 and, at several times of culture, DNA samples were extracted. All cheeses contaminated with L. monocytogenes were positive for the microbiological method 96 h post contamination and for nPCR and real-time PCR 48 h post contamination. At this time, the HlyA gene was amplified in all contaminated samples. Both molecular techniques showed the same sensitivity, 30 copies/reaction or 3.5 UFC/25 g, when plasmid DNA standard or artificially contaminated cheese samples were used. Finally, eighty soft cheese samples obtained from local retail stores and tested by three methods were negative, indicating a 100% concordance in results. The development of an nPCR with IAC reinforces the reliability of the negative results without increasing the costs of the reaction. Besides, nPCR showed less sensitivity to the presence of inhibitory substances in the reaction. The use of one of these molecular techniques could be easily coupled to the microbiological method, serving as a screening method in the food industry for hygiene monitoring and early identification of contaminated foods.

Inhibitor activity of Lactiplantibacillus plantarum LP5 on thermotolerant campylobacter with different biofilm-forming capacities

AIMS

To evaluate the biofilm-forming capacity of thermotolerant Campylobacter (TC) strains from poultry production and to analyse the inhibitory capacity of Lactiplantibacillus plantarum LP5 against TC on different materials.

METHODS AND RESULTS

Biofilm-forming capacity by Campylobacter jejuni and Campylobacter coli was analysed by cell adhesion in polystyrene plates. TC were classified as non-biofilm-forming (NBF, 1.3%), weak biofilm-forming (WBF, 68.4%), moderate biofilm-forming (MBF, 27.6%), and strong biofilm-forming (SBF, 2.7%). The inhibitory capacity of L. plantarum LP5 against TC was tested on stainless-steel, nylon, aluminium, and glass disks (treated group) and compared with biofilm-forming TC (control group). Lactiplantibacillus plantarum LP5 was inoculated, and then TC. Biofilm was removed in both experimental groups and TC and LP5 bacterial counts were performed. The L. plantarum LP5 presence reduced the formation of TC biofilm (P < 0.001). The material type and strain category influenced biofilm formation, with stainless-steel and the SBF strain being the material and TC having the highest adhesion (P < 0.001). Lactiplantibacillus plantarum LP5 formed a similar biofilm on all materials (P = 0.823).

CONCLUSIONS

This trial showed very promising results; L. plantarum LP5 could be incorporated as a bio-protector of TC on different surfaces.

Lactic acid bacteria viability in different refrigerated food matrices: a systematic review and Meta‑analysis

The aim of this systematic review and meta-analysis was to determine which variables affect the viability of lactic acid bacteria (LAB) added to different types of refrigerated foods during the first 28 days. Scopus, ScienceDirect, PubMed and Cochrane Central Register of Reviews databases were searched from 1997 to April 2022. A total of 278 studies, which showed randomized and controlled experiments published in peer reviewed journals, were included. The viability of LAB in different moments during the storage process was synthesized as mean point estimate (MPE) via random-effects meta-analyses and the effect of multiple factors on the LAB´s viability was evaluated by multiple meta-regression. The meta-analysis showed that the decrease in LAB viability will be more abrupt the greater the initial dose. The physical structure of food may influence bacterial viability. Fruit was the type of product that most quickly lost viability. Co-culture of two or more species did not affect viability. Preservation methods had an unfavorable effect and prebiotics had a beneficial effect on bacterial viability. Viability was genus dependent. The data obtained in this study provide an overview of the factors to be taken into account for the design of new foods.

Quantitative risk assessment of FMDV introduction in a FMD free country through bone-in beef and offal importation from a FMD free with vaccination country/zone

Quantitative risk assessment was used to estimate the risk of introducing foot-and-mouth disease (FMD) through bone-in beef from Argentina (FMD-free with vaccination status) into other FMD-free countries. A stochastic model was built to characterize all the steps from primary production to bone-in beef export and introduction into an FMD-free country. The probability that bone-in beef from at least one animal infected with the FMD virus (FMDV) was exported during a year was 5.27 × 10-3 (95% CI <10-10 - 5.19 x 10-2) or in other words one case in 190 years. The risk of FMDV introduction was sensitive to the probability of an outbreak occurring in Argentina (r [Spearman´s rank correlation] = 0.99) and the number of herds affected during an outbreak (r = 0.10). Additionally, the probability that susceptible animals in the importing country came into contact with infective material (bones) and generated an outbreak was 6.16 × 10-4 (95% CI <10-10 - 6.20 ×10-3) or one FMD outbreak every 1623 years on average. Based on the quantitative risk assessment results, the probability of FMDV introduction into a FMD-free country where vaccination is not practiced from a FMD-free country where vaccination is practiced associated with bone-in beef trade from Argentina was negligible. The risk of an FMD outbreak caused by the potential introduction of the FMDV was associated with the existing conditions in the country. Thus, maintaining the FMD-free status with or without vaccination would not be relevant.

Migration of Rhipicephalus microplus ticks among cattle

The aim of this work was to quantitatively analyse the magnitude of the migration of Rhipicephalus microplus ticks among cattle under field conditions, in groups of bovines with different stocking rates. The role of this phenomenon in the epidemiology of Anaplasma marginale has been discussed. Cattle naturally infested with R. microplus (donors) and cattle non-infested with R. microplus (recipients) were clustered for 13 days into two groups with low and high stocking rates (G1 and G2 respectively). The initial prevalence of infestation (infested cattle / total cattle) was 20% in both groups. Adult migratory ticks from donor to recipient cattle were recorded by examination of the recipient cattle on days 2, 6, 9, and 13. The tick infestation rate, calculated using the Kaplan-Meier survival test, was higher in G2 (p = 0.05). The cumulative incidence on day 13 was 25% in G1 and 65% in G2, with no significant differences. The results demonstrate that migration of adults of R. microplus under field conditions occurs, in accordance with previous studies, and that its magnitude is associated with the stocking rate. These results highlight the relevance of R. microplus in the epidemiology of A. marginale through its role as a vector in the intrastadial transmission of this pathogen of cattle.

Association between heat stress during intrauterine development and the expression and regulation of ovarian steroid hormone receptors in adult Holstein cows

CONTEXT

Dairy cattle experience stressful environmental situations that affect production. Heat stress during gestation can influence the intrauterine development of offspring, resulting in long-term damage that can affect the reproductive life of the adult offspring.

AIM

The aim of the present study was to evaluate changes in the expression and regulation of steroid hormone receptors in the ovary of Holstein cows gestated under different temperature-humidity index (THI) during their in utero development.

METHODS

Animals were classified by their exposure to temperature-humidity index (THI) ≥72 during their development in utero according to date of birth or date of effective service of their mother. This study was not carried out under controlled conditions, but the conditions to which the cows were naturally exposed during their development were considered retrospectively, controlling the variables in the statistical analyses (age as a covariate, dairy farm as a random factor). Gestation was divided into two periods (P1=days 0-150; and P2=day 151 to calving) and three trimesters (T1=days 0-90; T2=days 91-180; and T3=day 181 to calving), and the exposure to THI ≥72 was calculated in each one. The following characteristics were evaluated: gene expression of estrogen receptor (ESR) 1, ESR2 and progesterone receptor (PGR), CpG methylation in the 5'UTR of ESR1 and ESR2, and protein expression of ESR1, ESR2, PGR and coregulatory proteins in the dominant follicles of daughter cows in adulthood.

KEY RESULTS

We found associations between heat stress variables during gestation and the methylation status of CpG sites in the 5'UTR of ESR1 and ESR2 in dominant follicles. Results also showed association between exposure to high THI values during intrauterine development and expression of ESR1, ESR2 and PGR and coregulatory proteins in dominant follicles of adult cows.

CONCLUSIONS

These results provide novel information about the impact of prenatal heat stress on molecular aspects at the ovary level in the offspring, during their adult life, which probably impacts the reproductive aspects of the herd.

Protective effect of Lactiplantibacillus plantarum LP5 in a murine model of colonisation by Campylobacter coli DSPV458

Thermotolerant Campylobacter species are the leading cause of foodborne bacterial diarrheal disease worldwide. Campylobacter coli, abundant in pigs and pork products, have been identified as a source of human infection. In this study, we propose the use of Lactiplantibacillus plantarum LP5 as a probiotic to reduce colonisation of this intestinal pathogen in a murine colonisation model of C. coli DSPV458. Six-week-old adult female Balb/cCmedc mice were housed in groups: Control, Campy and Pro-Campy. Control and Pro-Campy groups received antibiotics for 5 days and the Campy group for 12 days. Pro-Campy group was inoculated for 7 days with 8.78 log₁₀ cfu total of L. plantarum LP5 suspended in De Man, Rogosa and Sharpe broth. All groups were inoculated with 6.72 log₁₀ cfu of C. coli DSPV458 suspended in brain heart infusion broth. L. plantarum LP5 was recovered only in the Pro- Campy group. C. coli DSPV458 was recovered at higher levels in the Control and Campy groups. The differences with the Pro-Campy group were significant. As regards faeces, Control and Campy groups reached 7.41 and 7.84 log₁₀ cfu/g, respectively, and the Pro-Campy group only 4.62 log₁₀ cfu/g. In the caecum, Control and Campy groups reached 8.01 and 9.26 log₁₀cfu/g, respectively, and the Pro-Campy group only 4.51 log₁₀ cfu/g. In the ileum, Control and Campy groups reached 3.43 and 3.26 log₁₀ cfu/g, respectively, and the Pro-Campy group did not show detectable levels. The reduction of C. coli DSPV458 in the Pro-Campy group compared to the Control group in faeces, caecum and ileum was 99.55, 99.98 and 100%, respectively. Animals were maintained under normal health conditions, and haematological parameters were within the standard values for Balb/cCmedc. The incorporation of a probiotic generated a protective effect in the mice colonisation model. The protective effect would also apply to intestinal colonisation by indigenous enterobacteria. Therefore, the strategy used in this study is of great importance to understand the protection mechanisms in a murine model, as well as its application in food-producing animals.

Effect of probiotic Lactiplantibacillus plantarum and chestnut flour (Castanea sativa mill) on microbiological and physicochemical characteristics of dry-cured sausages during storage

The effect of chestnut flour (Castanea sativa Mill) on L. plantarum viability and physicochemical characteristics in a dry-cured sausage (Longaniza de Pascua) during storage is discussed. Four batches were prepared: CL with 3% chestnut flour added; CPL with 3% chestnut flour and 8.5 log CFU/g L. plantarum added; PL with 8.5 log CFU/g L. plantarum added and L, the batch control. The sausages were stored at 4 °C and 20 °C, and vacuum packed for 43 d. L. plantarum viability was affected by storage time (P < 0.001). However, higher L. plantarum counts at the final of storage were reached due to chestnut flour addition (P < 0.001). At room storage, chestnut flour caused a higher increase in TBARS values (P = 0.022). Nevertheless, all lipid oxidation treatments were in the range of accepted values at the sensory detection level. In conclusion, Longaniza de Pascua can be kept at 4 °C or 20 °C for 43 d without causing any rancidity problems.

Murine colonization model by Campylobacter coli DSPV458

AIMS

To generate a murine experimental model of colonization by Campylobacter coli DSPV458.

METHODS AND RESULTS

Twelve adult Balb/cCmedc female mice were housed in a treated group (T-G) and a control group (C-G) for 4 weeks. Both experimental groups received antibiotics for 5 days during the first week. The T-G was administered with 6.68log₁₀ CFU of C. coli DSPV458 by oesophageal gavage. Necropsies were performed weekly to evaluate translocation and intestinal colonization in the spleen and liver and in the ileum and cecum respectively. Samples were cultured to quantify intestinal microbiota members. Faeces were cultured weekly for a C. coli DSPV458 count. Campylobacter coli DSPV458 was isolated from all the inoculated mice. The recovered level of C. coli DSPV458 was, on average, 6.9 log₁₀ CFUg^-1 , 8.0 log₁₀ CFUg^-1 and 1.6 log₁₀ CFUg^-1 in faeces, cecum and ileum respectively. Colonization by C. coli DSPV458 does not alter the normal clinical and physiological status.

CONCLUSIONS

Campylobacter coli DSPV458 does not have an invasive capacity, and the model is suitable for evaluating strategies to reduce intestinal loads.

SIGNIFICANCE AND IMPACT OF STUDY

Farm animals have an important impact on thermotolerant Campylobacter transmission to humans. Extremely few colonization models by C. coli have been reported to date. In food-producing animals, infection is mild or absent and thermotolerant Campylobacter colonize the intestines of animals. Colonization models are specific models that do not cause infection as they do not generally result in diarrhoea or other signs of disease. Therefore, this model will allow to evaluate the evolution of colonization by thermotolerant Campylobacter and the alternative tools development to antibiotics that limit their colonization in food-producing animals.

Association between phagocytic activity of monocytes and days to conception after parturition in dairy cows when considering the hormonal and metabolic milieu

The nutritional conditions and immune status of dairy cows affect reproductive performance. This study was conducted with the aim to analyze the phagocytic activity (PA) and phagocytic capacity (PC) of circulating monocytes after the period of transition from pregnancy to lactation, to evaluate possible associations with duration of time period to conception following parturition. Results indicated PA was not associated with duration of time period to conception following parturition. In contrast, cows with a lesser PC conceived earlier (98 ± 9 days in milk, DIM) than those with a greater PC (168 ± 15 DIM). Based on these results, to analyze the association of the hormonal and metabolic milieu with the PA and PC, the animals were grouped considering the days to conception following parturition. In the group with the greater number of days to conception (>168 DIM), the PA was associated with concentrations of progesterone and beta-hydroxybutyrate (BHB) at 90 DIM and glucose at 120 DIM, whereas PC was associated with the concentrations of progesterone, cortisol and glucose at 90 DIM, non-esterified fatty acids (NEFA) at 120 DIM, 17β-estradiol at 150 DIM, and 17β-estradiol and BHB at 180 DIM. Overall, these results represent a new perspective related to the reproductive performance of dairy cows. The modifications of cellular functions may be useful for predicting the onset of health complications in dairy cows and to manage cows in ways that result in an enhanced fertility during the subsequent lactational period.

In vitro screening and in vivo colonization pilot model of Lactobacillus plantarum LP5 and Campylobacter coli DSPV 458 in mice

The objective of this work was to determine the antibacterial effect of Lactobacillus plantarum strains of pork origin against Campylobacter coli strains, and to conduct experimental colonization pilot models in mice for both microorganisms. Inhibition assays allowed evaluation and selection of L. plantarum LP5 as the strain with the highest antagonistic activity against C. coli and with the best potential to be used in in vivo study. Adult 6-week-old female Balb/cCmedc mice were lodged in two groups. The treated group was administered with 9.4 log₁₀CFU/2 times/wk of L. plantarum LP5. L. plantarum LP5 was recovered from the feces and cecum of the inoculated mice. However, when bacteria stopped being administered, probiotic counts decreased. Experimental colonization with C. coli was carried out in five groups of mice. All animals were treated with antibiotics in their drinking water to weaken the indigenous microbiota and to allow colonization of C. coli. Four groups were administered once with different C. coli strains (DSPV458: 8.49 log₁₀CFU; DSPV567: 8.09 log₁₀CFU; DSPV570: 8.46 log₁₀CFU; DSPV541: 8.86 log₁₀CFU, respectively). After 8 h, mice inoculated with different C. coli strains were colonized because the pathogen was detected in their feces. L. plantarum LP5 tolerated the gastrointestinal conditions of murine model without generating adverse effects on the animals. C. coli DSPV458 colonized the mice without causing infection by lodging in their digestive tract, thus generating a reproducible colonization model. Both models combined could be used as protection murine models against pathogens to test alternative control tools to antibiotics.

Association between heat stress during intrauterine development and the calving-to-conception and calving-to-first-service intervals in Holstein cows

Heat stress has been widely studied in relation to its effects on the production and reproduction of dairy cattle. However, the long-term effects of heat stress during intrauterine development on adult cows have been scarcely considered. Thus, the aim of this study was to evaluate possible changes in the reproductive performance of Holstein cows gestated under different values of the Temperature-Humidity Index (THI) during their intrauterine development. Data collected from a database of reproductive and productive records of 10,790 Holstein cows from the central region of Argentina and the THI data from the agrometeorological station of the Instituto Nacional de Tecnología Agropecuaria (INTA) EEA Rafaela, Santa Fe, Argentina, were used. The gestation of the cows evaluated was divided into trimesters, in which the highest THI cycles (sum of three or more consecutive days of exposure to a THI ≥72 during each trimester) and number of days with a THI ≥ 72 were calculated. The calving-to-conception and calving-to-first-service intervals of the cows evaluated were considered as reproductive variables associated with their first lactation. Generalized Linear Mixed Models were used, considering the cow's dairy farm as a random factor within the model. The exposure of the animals to environments with a THI ≥72 during the first trimester of gestation had a negative impact on the reproductive efficiency parameters analyzed. The results obtained indicate that the exposure of pregnant females to high THI values has a long-term impact on their daughters, which may contribute to a decrease in their reproductive performance, possibly through inherited epigenetic characteristics that remain in later generations through fetal programming.

Possible reservoirs of thermotolerant Campylobacter at the farm between rearing periods and after the use of enrofloxacin as a therapeutic treatment

Campylobacteriosis is a zoonosis and the most frequent cause of food-borne bacterial enteritis in humans. C. jejuni and C. coli are the most common species implicated in campylobacteriosis. Broilers and their products are considered the most important food sources of human infections. The aim of the present study was to evaluate the presence of thermotolerant Campylobacter in different reservoirs at the farm, and the permanence of this pathogen during four consecutive rearing periods. The samples were taken from the same house farm in the downtime period and during the last week of broiler rearing, prior to their slaughter during four consecutive cycles. Different reservoirs as potential sources of Campylobacter were analysed. The prevalence of Campylobacter in vectors was 23% in A. diaperinus larvae, 20% in wild birds, 13% in A. diaperinus adults, and 9% in flies; as regards fomites, the prevalence was 50% in workers' boots, 27% in litter, and 21% in feed, while in broilers it was 80%. Campylobacter jejuni was the most detected species (51%) in the samples analysed. In addition, some Campylobacter genotypes persisted in the house farm throughout consecutive rearing periods, indicating that those strains remain during downtime periods. However, our study could not identify the Campylobacter sources in the downtime periods because all the samples were negative for Campylobacter isolation. In addition, a remarkable finding was the effect of the use of enrofloxacin (as a necessary clinical intervention for flock health) in cycle 3 on the Campylobacter population. No Campylobacter could be isolated after that clinic treatment. Afterwards, we found a greater proportion of C. coli isolates, and the genotypes of those isolates were different from the genotypes found in the previous rearing periods. In conclusion, the effect of the use of enrofloxacin during the rearing period changed the Campylobacter species proportion, and this finding is particularly interesting for further evaluation. Furthermore, more studies should be conducted with the aim of detecting the Campylobacter sources between rearing periods.

Quantitative risk assessment of haemolytic uremic syndrome associated with beef consumption in Argentina

We developed a quantitative microbiological risk assessment (QMRA) of haemolytic uremic syndrome (HUS) associated with Shiga toxin-producing Escherichia coli (STEC)-contaminated beef (intact beef cuts, ground beef and commercial hamburgers) in children under 15 years of age from Argentina. The QMRA was used to characterize STEC prevalence and concentration levels in each product through the Argentinean beef supply chain, including cattle primary production, cattle transport, processing and storage in the abattoir, retail and home preparation, and consumption. Median HUS probability from beef cut, ground beef and commercial hamburger consumption was <10-15, 5.4x10-8 and 3.5x10-8, respectively. The expected average annual number of HUS cases was 0, 28 and 4, respectively. Risk of infection and HUS probability were sensitive to the type of abattoir, the application or not of Hazard Analysis and Critical Control Points (HACCP) for STEC (HACCP-STEC), stx prevalence in carcasses and trimmings, storage conditions from the abattoir to retailers and home, the joint consumption of salads and beef products, and cooking preference. The QMRA results showed that the probability of HUS was higher if beef cuts (1.7x) and ground beef (1.2x) were from carcasses provided by abattoirs not applying HACCP-STEC. Thus, the use of a single sanitary standard that included the application of HACCP-STEC in all Argentinean abattoirs would greatly reduce HUS incidence. The average number of annual HUS cases estimated by the QMRA (n = 32) would explain about 10.0% of cases in children under 15 years per year in Argentina. Since other routes of contamination can be involved, including those not related to food, further research on the beef production chain, other food chains, person-to-person transmission and outbreak studies should be conducted to reduce the impact of HUS on the child population of Argentina.

Worldwide meta-analysis of the prevalence of Campylobacter in animal food products

The objective of this meta-analysis was to summarize available information on the prevalence of thermotolerant Campylobacter in different animal food products. A number of multilevel random-effect meta-analysis models were fitted to estimate mean prevalence of thermotolerant Campylobacter and to compare them among animal food products (cattle, pigs, broiler, hen, goat, sheep). The mean prevalence of Campylobacter spp. in animal food products was 29.6% (95% CI 27.6%-31%), and the mean prevalence of C. jejuni and C. coli were 19.3% and 9.7%, respectively. The prevalence of Campylobacter spp. was higher in products whose sources were broiler meat (p-estimate = 47.8%; 95% CI 44.9%-50.6%). C. jejuni was mainly observed in broiler meat where prevalence estimate (p-estimate) was 33.7% (95% CI 30.7%-36.8%). On the other hand, C. coli was observed in broiler meat (p-estimate = 14.1%; 95% CI 12.3%-16.1%) and sheep meat (p-estimate = 11.0%; 95% CI 3.6%-29.1%). The animal food products with the lowest prevalence of Campylobacter spp. were milk and dairy products (p-estimate = 3.5%; 95% CI 1.8%-6.5%), eggs (p-estimate = 4.0%; 95% CI 1.4%-10.7%), sausage (p-estimate = 9.4%; 95% CI 3.3%-24.0%), This meta-analysis concluding that C. jejuni is the most prevalent species worldwide and broiler meat is the main contamination source for human. The prevalence of Campylobacter species has public health importance and national authorities must monitor the situation in each country with the aim to establish the appropriate risk management measures.

A vaccine using Anaplasma marginale subdominant type IV secretion system recombinant proteins was not protective against a virulent challenge

Anaplasma marginale is the most prevalent tick-borne livestock pathogen with worldwide distribution. Bovine anaplasmosis is a significant threat to cattle industry. Anaplasmosis outbreaks in endemic areas are prevented via vaccination with live A. centrale produced in splenectomized calves. Since A. centrale live vaccine can carry other pathogens and cause disease in adult cattle, research efforts are directed to develop safe recombinant subunit vaccines. Previous work found that the subdominant proteins of A. marginale type IV secretion system (T4SS) and the subdominant elongation factor-Tu (Ef-Tu) were involved in the protective immunity against the experimental challenge in cattle immunized with the A. marginale outer membrane (OM). This study evaluated the immunogenicity and protection conferred by recombinant VirB9.1, VirB9.2, VirB10, VirB11, and Ef-Tu proteins cloned and expressed in E. coli. Twenty steers were randomly clustered into four groups (G) of five animals each. Cattle from G1 and G2 were immunized with a mixture of 50 μg of each recombinant protein with Quil A® or Montanide™ adjuvants, respectively. Cattle from G3 and G4 (controls) were immunized with Quil A and Montanide adjuvants, respectively. Cattle received four immunizations at three-week intervals and were challenged with 107 A. marginale-parasitized erythrocytes 42 days after the fourth immunization. After challenge, all cattle showed clinical signs, with a significant drop of packed cell volume and a significant increase of parasitized erythrocytes (p<0.05), requiring treatment with oxytetracycline to prevent death. The levels of IgG2 induced in the immunized groups did not correlate with the observed lack of protection. Additional strategies are required to evaluate the role of these proteins and their potential utility in the development of effective vaccines.

Risks of cattle babesiosis (Babesia bovis) outbreaks in a semi-arid region of Argentina

The epidemiology of Babesia bovis was studied in terms of enzootic stability/instability and husbandry and abiotic factors influencing B. bovis transmission rate in northeastern Santiago del Estero province, Argentina. The area is of limited suitability for its only vector in Argentina, the tick Rhipicephalus microplus. The proportion of calf herds in a state of enzootic stability/instability to B. bovis was determined and husbandry practices and abiotic factors associated with variations in B. bovis transmission rates were explored using a cross-sectional observational study design. Daily probability of infection (inoculation rate, h) with B. bovis was calculated from age-specific seroprevalence via ELISAi in 58 herds of 4.5-8.5-month-old calves. Herds were considered to be in enzootic instability (EI) when h < 0.005, and therefore inferred to be at risk of babesiosis outbreaks. Husbandry practices associated with differences in B. bovis transmission were analyzed using generalized linear models. Sixty-two percent of herds were found to be in an EI situation for B. bovis. Calves raised exclusively on permanent pastures -where higher cattle density is achieved- were exposed to higher B. bovis inoculation rates (h = 0.0063, 95% CI 0.0032-0.0123) than those reared under forage combinations (h = 0.0024, 95% CI 0.0011-0.0051) (P =  0.05). In addition, calves from herds located in the area of intermediate suitability for R. microplus development were more likely to become infected with B. bovis (h = 0.0067, 95% CI 0.0037-0.0121) than those reared in the ecologically unfavorable area for the vector (h = 0.0023, 95% CI 0.0010-0.0049) (P =  0.02). Neither the frequency of treatment with acaricides nor the use of long-acting acaricides to control R. microplus influenced the inoculation rate (P =  0.99 and P =  0.26, respectively). This result indicates that current R. microplus control schemes are not effective in reducing B. bovis transmission. Enzootic instability still prevails in the study area despite the drastic changes occurred in cattle production system. However, 38% of herds did reach enzootic stability; therefore, a specific epidemiological status cannot be assumed at a regional level. Yearly determination of the immunological status of each calf cohort is considered a proper approach to decision-making in vaccination against B. bovis.

Quantification of aflatoxin M1 carry-over rate from feed to soft cheese

•

The levels of AFM₁ in milk produced in Argentina are relatively low.

•

Milk production, fiber particle size and AFB₁ level affected the carry-over rate.

•

The greatest proportion of AFM₁ in milk is detected in whey during cheese. production.

From January to December 2016, samples of milk and feeds of dairy cattle were monthly collected. The concentration of mycotoxins in all matrices was determined using the enzymatic immunoassay technique. The average concentration of aflatoxin B₁ (AFB₁), deoxynivalenol (DON) and zearalenone (ZEA) in feed was 3.01, 218.5 and 467 ug/kg, respectively. The average AFB₁ carry-over rate was 0.84% with a variation between 0.05 to 5.93%. Particle size of the feed (P = 0.030) and individual milk production (P = 0.001) affected this rate. Mini-soft cheeses were produced using milk naturally contaminated with aflatoxin M₁ (AFM₁) as raw material to study its distribution both in whey and in cheese. The average level of AFM₁ in milk was 0.014 μg/l. None of milk samples exceeded the maximum level accepted for AFB₁ by the Southern Common Market (MERCOSUR) legislation (0.5 μg/l) and only 5.5% of samples exceeded the European Union (UE) regulations (0.05 μg/l). After the cheese elaboration, the concentration of AFM₁ was determined in whey and in cheese. The greatest proportion (60%) was detected in whey while 40% AFM₁ remained in the cheese. However, the concentration of AFM₁ was higher in the cheese compared to the original milk.

A meta-analysis on the effectiveness of homofermentative and heterofermentative lactic acid bacteria for corn silage

AIMS

This meta-analysis aims to assess the effect of lactic acid bacteria (LAB) inoculation on fermentation parameters, microbiological composition and aerobic stability of corn silage.

METHODS AND RESULTS

Databases (PubMed, ScienceDirect and Scopus) were searched from 1980 to 2017. The criteria for inclusion were: randomized and controlled experiments using corn silage and published in peer-reviewed journals. The meta-analysis showed that LAB supplementation increased pH, acetate and propionate concentrations, and decreased acid detergent fibre, water-soluble carbohydrates and ammoniacal nitrogen (NH3 -N) compared to controls in the pooled raw mean difference random effect model. In addition, inoculation reduced counts of yeasts and moulds, increased LAB counts and markedly improved aerobic stability in corn silage. However, results indicated that the effect of inoculants may differ depending on the administration of homofermentative or heterofermentative LAB.

CONCLUSIONS

For the development of functional bacterial inoculants, both types of LAB should be used.

SIGNIFICANCE AND IMPACT OF THE STUDY

To our knowledge, this is the first meta-analysis to compare the application of homofermentative and heterofermentative LAB for corn silage.

National short-term dietary exposure assessment of a selected group of pesticides in Argentina

An evaluation of acute dietary exposure to pesticide residues, applying deterministic and stochastic methods, was performed for a selected group of pesticides in two representative age groups from Argentina. Thus, 28 active ingredients (a.i.) and 75 food items were evaluated for the group of 2-5-year-old children, while 9 a.i. and 59 food items were considered for the 10-49-year-old women group. A deterministic assessment was conducting following the Food and Agriculture Organization (FAO) and World Health Organization (WHO) procedure but using the national maximum residue limits (MRLs) as pesticide residue concentration data, while in the stochastic approach, a theoretical distribution modeled with the available information was used. Food consumption data were obtained from the 2004-2005 comprehensive national nutrition and health survey. The risk was estimated by comparing the short-term dietary exposure with the acute reference dose (ARfD) values for each pesticide-food combination evaluated. In the deterministic assessment, 173 (39.1%) and 40 (31.3%) combinations exceeded the ARfD thresholds for the 2-5-year-old children and 10-49-year-old women groups, respectively. This conservative study generated relevant information as a first stage of acute dietary risk assessment in Argentina.

Antimicrobial Resistance of Thermotolerant Campylobacter Species Isolated from Humans, Food-Producing Animals, and Products of Animal Origin: A Worldwide Meta-Analysis

The objective of this meta-analysis was to summarize available information on the prevalence of antimicrobial-resistant Campylobacter species in humans, food-producing animals, and products of animal origin. A number of multilevel random-effect meta-analysis models were fitted to estimate mean occurrence rate of antimicrobial-resistant thermotolerant Campylobacter and to compare them throughout the years and among the species, food-producing animals (i.e., bovine, pigs, broilers, hen, goat, and sheep), country of origin, sample type, methodology to determine the antimicrobial susceptibility, and the species of Campylobacter. Among the considered antibiotics, thermotolerant Campylobacter showed the highest resistance to tetracycline (pool estimate [PE] = 0.493; 95% CI 0.466-0.519), nalidixic acid (PE = 0.385; 95% CI 0.348-0.423), and ciprofloxacin (PE = 0.376; 95% CI 0.339-0.415). In general, the prevalence of antimicrobial-resistant Campylobacter spp. was higher in hen, broilers, and swine. Campylobacter coli showed a higher prevalence of antimicrobial resistance than Campylobacter jejuni. Independent of the antimicrobial evaluated, the disk diffusion method showed higher prevalence of antimicrobial-resistant Campylobacter than the methods based on the minimum inhibitory concentration estimation. The meta-analysis showed that the prevalence of antimicrobial-resistant Campylobacter is relevant essentially in foods derived from hens and broilers, and it was observed worldwide. The prevalence of this pathogen is of public health importance and the increase in the prevalence of Campylobacter strains resistant to the antimicrobial of choice worsens the situation, hence, national authorities must monitor the situation in each country with the aim to establish the appropriate risk management measures.

Development and storage studies of high density macrocapsules containing Lactobacillus spp. strains as nutritional supplement in young calves

The aim of this study was to evaluate different production methodologies of probiotic macrocapsules with high bacterial densities destined to lactating calves. Three types of capsules containing Lactobacillus casei DSPV318T and Lactobacillus plantarum DSPV354T were prepared from an overnight culture in whey medium: (1) mixing the culture with calcium alginate and then, reincubating the capsules in whey (RC); (2) concentrating the biomass by centrifugation and mixing the pellet with calcium alginate (CC) at different concentrations with respect to the initial culture (5X and 12.5X); (3) CC with cryoprotectants: whey permeate (Per) and glycerol (Gly). Chitosan coating was evaluated. Capsules were freeze-dried and viability was assessed before freezing, after freeze-drying and every two weeks for 84 days of storage at room temperature, 4°C and -20°C. CC showed higher cell densities than RC. Storage temperature affected viability: greater viability at lower temperature. Moreover, the effect of temperature was influenced by other factors, such as capsule coating, culture neutralization and cryoprotectants. Coating improved viability at room temperature; however no effect was observed at 4°C. Culture neutralization allowed greater survival during storage. Cryoprotectants improved viability during freezing, but they also generated a positive or negative effect depending on storage temperature. The best results were: at refrigeration Gly12.5X exhibited counts above 10⁹CFU/capsule until day 70 and Per12.5X until day 56 of storage and at -20°C Gly12.5X showed counts above 10⁹CFU/capsule until the end of the study (84 days). A 10⁹CFU capsule is the daily dose per calf which would facilitate the administration of this probiotic inoculum to field animals.

Impact of lyophilized Lactobacillus salivarius DSPV 001P administration on growth performance, microbial translocation, and gastrointestinal microbiota of broilers reared under low ambient temperature

This study was undertaken with the aim of investigating the effects of dietary supplementation of probiotic strain Lactobacillus salivarius DSPV 001P on growth performance, microbial translocation, and gastrointestinal microbiota of broilers reared under low ambient temperature. Two hundred and forty, one-day-old male Cobb broilers were randomly distributed into two treatment groups, a probiotic group and a control group, with four replicates per treatment and 30 broilers per replicate. The temperature of the broiler house was maintained at 18-22°C during the first three weeks, after which the temperature was at range of 8°C to 12°C. The results showed that probiotic treatment significantly improved body weight of broilers when compared with the control group. After 42days, the weight means were 2905±365.4g and 2724±427.0g, respectively. Although there were no significant differences, dietary inclusion of L. salivarius tended to increase feed intake and to reduce feed conversion ratio during the six-week experimental period. Similarly, supplementation tended to reduce the rate of mortality, with 12 deaths occurring in the probiotic group, and 20 in the control group. However, no differences were observed in intestinal bacterial concentrations of Enterobacteriaceae, E.coli, and lactic acid bacteria in both crop and caecum among treatments. Through our study, it appears that L. salivarius DSPV 001P was non-pathogenic, safe and beneficial to broilers, which implies that it could be a promising feed additive, thus enhancing the growth performance of broilers and improving their health.

Genetic diversity of thermotolerant Campylobacter spp. isolates from different stages of the poultry meat supply chain in Argentina

The objective of this study was to investigate a clonal relationship among thermotolerant Campylobacter spp. isolates from different stages of the poultry meat supply chain in Argentina. A total of 128 thermotolerant Campylobacter spp. (89 C. jejuni and 39 C. coli) isolates from six poultry meat chains were examined. These isolates were from: a) hens from breeder flocks, b) chickens on the farm (at ages 1 wk and 5 wk), c) chicken carcasses in the slaughterhouse, and d) chicken carcasses in the retail market. Chickens sampled along each food chain were from the same batch. Campylobacter spp. isolates were analyzed using pulsed-field gel electrophoresis to compare different profiles according to the source. Clustering of C. jejuni isolates resulted in 17 profiles, with four predominant genotypes and many small profiles with just a few isolates or unique patterns, showing a very high degree of heterogeneity among the C. jejuni isolates. Some clusters included isolates from different stages within the same chain, which would indicate a spread of strains along the same poultry meat chain. Moreover, twenty-two strains of C. coli clustered in seven groups and the remaining 17 isolates exhibited unique profiles. Evidence for transmission of thermotolerant Campylobacter spp. through the food chain and cross contamination in the slaughterhouses were obtained. This collective evidence should be considered as the scientific basis to implement risk management measures to protect the public health.

Prevalence of honey bee (Apis mellifera) viruses in temperate and subtropical regions from Argentina

In Argentina, bee virus studies are still incipient, and there are no studies regarding the climatic effect. The aim of this study was to assess and compare the presence of honeybee viruses in different climatic regions from Argentina. A total of 385 colonies distributed in five Argentinean eco-regions were examined to evaluate the percentage of infestation with Varroa destructor and the presence of seven virus species (Deformed wing virus, DWV; Acute bee paralysis virus, ABPV; Chronic bee paralysis virus, CBPV; Black queen cell virus, BQCV; Kashmer bee virus, KBV; Israeli acute bee paralysis virus, IAPV; and Sacbrood bee virus, SBV) after honey yield. Two viruses, KBV and IAPV, were not detected. The other five viruses were found in different prevalences: DWV (35%), ABPV (21.5%), BQCV (8.0%), CBPV (2.2%), and SBV (1.1%). We found double and triple viral associations in approximately 25% of the sampled colonies. The mean V. destructor infestation in the colonies prior to the acaricide treatment was 7.12%±8.7%. The knowledge of the prevalence of these viruses in the region and their relation with the mite and other possible influencing factors is important for preventing colony losses. Further studies are necessary to identify the risk factors associated with virus presence and its relationship with other pathogens such as V. destructor.

[Campylobacter jejuni O:19 serotype in Argentine poultry meat supply chain]

Thermotolerant species of Campylobacter have been focus of attention in the last years because they are the major agent causing zoonotic foodborne diseases. In addition, Campylobacter jejuni O:19 serotype was associated with Guillain Barré syndrome. The aim of this study was to determine the proportion of C. jejuni O:19 serotype isolated at different stages of three poultry meat supply chain in Santa Fe, Argentina. The analysis showed that 18% of isolated C. jejuni belong to serotype O:19. It was also determined that the presence of these strains is given in almost all production stages. These results reflect a significant risk to public health of consumers. Epidemiological studies of Campylobacter should be considered to establish a risk manager policy.

Comprehensive estimate of the theoretical maximum daily intake of pesticide residues for chronic dietary risk assessment in Argentina

A chronic dietary risk assessment for pesticide residues was conducted for four age groups of the Argentinian population following the procedure recommended by the WHO. The National Theoretical Maximum Daily Intake (NTMDI) for 308 pesticides was calculated for the first time, using the Maximum Residue Limits (MRLs) from several Argentinean regulations and food consumption data from a comprehensive National Nutrition and Health Survey. The risk was estimated by comparing the TMDI with the Acceptable Daily Intakes (ADI) identified by various sources. Furthermore, for each of the compounds with a TMDI >65% of the ADI, a probabilistic analysis was conducted to quantify the probability of exceeding the ADI. In this study 27, 22, 10, and 6 active ingredients (a.i.) were estimated to exceed the 100% of the ADI for the different population groups: 6-23 month-old children, 2-5 year-old children, pregnant women, and 10-49 year-old women, respectively. Some of these ADI-exceeding compounds (carbofuran, diazinon, dichlorvos, dimethoate, oxydemeton-methyl and methyl bromide) were found in all four of these groups. Milk, apples, potatoes, and tomatoes were the foods that contributed most to the intake of these pesticides. The study is of primary importance for the improvement of risk assessment, regulations, and monitoring activities.

Poultry blood from slaughterhouses: development of a biopreservation system to improve microbiological quality prior to transforming blood into by-products

The aim of this study was to investigate the use of indigenous lactic acid bacteria (LAB) with specific additives as a Biopreservation System (BS) for poultry blood during its storage in slaughterhouses. The BS consisted of two LAB (Enterococcus faecalis DSPV 008SA or Lactobacillus salivarius DSPV 032SA) with 4 additives (lactose 2 g/l, yeast extract 0.4 g/l, ammonium citrate 0.4 g/l and NaCl 1 g/l). After 24 h storage at 30ºC, lower counts of enterobacteria, coliforms, Pseudomonas spp. and Staphylococcus aureus were evident in blood treated with the BS than in untreated blood. The ability of LAB to prevent haemolysis was evident. A decrease in pH was associated with control of spoilage microorganisms but it needed to be regulated to prevent coagulation of proteins. On the basis of these results it is recommended to supplement blood with a BS to avoid undesirable changes during blood storage before processing.

Varroa destructor and viruses association in honey bee colonies under different climatic conditions

Honey bee colonies are threatened by multiple factors including complex interactions between environmental and diseases such as parasitic mites and viruses. We compared the presence of honeybee-pathogenic viruses and Varroa infestation rate in four apiaries: commercial colonies that received treatment against Varroa and non-treated colonies that did not received any treatment for the last 4 years located in temperate and subtropical climate. In addition, we evaluated the effect of climate and Varroa treatment on deformed wing virus (DWV) amounts. In both climates, DWV was the most prevalent virus, being the only present virus in subtropical colonies. Moreover, colonies from subtropical climate also showed reduced DWV amounts and lower Varroa infestation rates than colonies from temperate climate. Nevertheless, non-treated colonies in both climate conditions are able to survive several years. Environment appears as a key factor interacting with local bee populations and influencing colony survival beyond Varroa and virus presence.

Quantitative Risk Assessment of Human Trichinellosis Caused by Consumption of Pork Meat Sausages in Argentina

In Argentina, there are three known species of genus Trichinella; however, Trichinella spiralis is most commonly associated with domestic pigs and it is recognized as the main cause of human trichinellosis by the consumption of products made with raw or insufficiently cooked pork meat. In some areas of Argentina, this disease is endemic and it is thus necessary to develop a more effective programme of prevention and control. Here, we developed a quantitative risk assessment of human trichinellosis following pork meat sausage consumption, which may be used to identify the stages with greater impact on the probability of acquiring the disease. The quantitative model was designed to describe the conditions in which the meat is produced, processed, transported, stored, sold and consumed in Argentina. The model predicted a risk of human trichinellosis of 4.88 × 10(-6) and an estimated annual number of trichinellosis cases of 109. The risk of human trichinellosis was sensitive to the number of Trichinella larvae that effectively survived the storage period (r = 0.89), the average probability of infection (PPinf ) (r = 0.44) and the storage time (Storage) (r = 0.08). This model allowed assessing the impact of different factors influencing the risk of acquiring trichinellosis. The model may thus help to select possible strategies to reduce the risk in the chain of by-products of pork production.

Risk factors for work-related injury among farm workers: a 1-year study

A 1-year prospective study was carried out to look for risk factors of farm-related injuries in Egusquiza, Santa Fe (Argentina). Information on demographic characteristics and occupational accidents was collected on (N=110, n=78) farm workers by means of personal interviews using a structured questionnaire. Monthly telephone contact was then maintained with the workers for 1 year to document all farm-related injuries. Data analysis included incidence rate, χ2 and logistic regression. Sixty-nine farm-related injuries were reported during the study period, six injuries being the maximum number affecting one worker. A total of 46.3% of the workers suffered at least one injury during the year. The incidence rate was 7.5 injuries/100 individual-month at risk. Medical assistance was needed in 26.8% of the cases and 5.8% of the injuries caused at least 1 day off work. Hospitalization for at least 1 day was required for 2.9% of the injured workers. Previous work-related injury in the family (p=0.005) (odds ratio (OR)=4.6, 95% confidence interval (CI)=1.6-13.3) and worker's activity (p=0.021) (OR=3.7, 95%CI=1.2-11.6) were associated with the dependent variable work injury. Agricultural and livestock farming are of great importance for the national economy. Workers' training on farm safety may play a key role to prevent work-related injuries and diseases.

Probiotics and broiler growth performance: a meta-analysis of randomised controlled trials

1. The aim of this meta-analysis was to investigate the effects of probiotics on the growth performance of broilers. PubMed, Scopus and Scholar Google databases were searched in all languages from 1980 to 2012. The studies in the meta-analysis were only selected if they were randomised and controlled experiments using broilers without apparent disease and the results were published in peer-reviewed journals. 2. A total of 48 and 46 studies were included to assess probiotic effects on body weight gain (BWG) and feed efficiency (FE), respectively. Probiotics increased BWG compared to controls (SMD = 0.661, 95% CI 0.499 to 0.822) and improved FE (SMD = - 0.281, 95% CI -0.404 to -0.157) in the pooled standardised mean difference random effect model, considering the source of heterogeneity and publication biases. However, there are evidences of publication bias and heterogeneity, so the results of this meta-analysis should be considered with caution. Applying the Duval and Tweedie's trim-and-fill methods, the adjusted value for BWG was 0.0594 (95% CI -0.122 to 0.242), and the adjusted value for FE did not show any modifications. 3. The meta-analysis showed that application of probiotics via water resulted in greater BGW and FE than administration through the feed. The effect was not related to the use of mono-strain or multi-strain probiotics, although it may depend on the strain used. The number of broilers and the duration of the experiments had an impact on the outcomes. 4. Additional studies should be conducted with the aim to identify the covariates which can explain the differences in the estimated effect sizes.

Zoonoses in rural veterinarians in the central region of Argentina

OBJECTIVE

To estimate the frequency of zoonoses in rural veterinarians and to search for risk factors.

DESIGN

Cross-sectional study based on an anonymously answered structured questionnaire.

SETTING

The interviewees participated in mandatory continuing education classes scheduled throughout the province by the College of Veterinary Surgeons.

PARTICIPANTS

Overall, 741 professionals were surveyed, and 75.8% (n = 562) of them completed the structured questionnaire.

MAIN OUTCOME MEASURES

Cumulative incidence (CIR) and incidence density (IDR) rates, standardised rates, χ(2) , Student's t-test, Pearson's correlation coefficient and logistic regression.

RESULTS

The CIR for all zoonoses was 34.1% (brucellosis, 29.1%; toxoplasmosis, 2.1%; leptospirosis, 0.6%; tuberculosis, 0.6%; anthrax, 0.6%; ringworm, 0.4%; other, 0.6%). The IDR for the period 1964-2008 was estimated to be 20.7% (19.5% for brucellosis). The brucellosis IDR decreased between 1964 and 2008 and was higher during early post-graduation. The risk of brucellosis was associated with the number of years of practice and the geographical area. Sixty-nine respondents had at least one day of absence from work (24.0 ± 27.8 days).

CONCLUSIONS

A high frequency of zoonoses was reported by veterinarians with a large animal practice. Although the rate of zoonoses may be decreasing, further studies are needed to confirm this finding. A joint effort of all institutions is needed to prevent zoonoses among private practitioners.

Pathogen translocation and histopathological lesions in an experimental model of Salmonella Dublin infection in calves receiving lactic acid bacteria and lactose supplements

The purpose of this study was to evaluate the capacity of a lactic acid bacteria (LAB) inoculum to protect calves with or without lactose supplements against Salmonella Dublin infection by evaluating histopathological lesions and pathogen translocation. Fifteen calves were divided into three groups [control group (C-G), a group inoculated with LAB (LAB-G), and a group inoculated with LAB and given lactose supplements (L-LAB-G)] with five, six, and four animals, respectively. The inoculum, composed of Lactobacillus (L.) casei DSPV 318T, L. salivarius DSPV 315T, and Pediococcus acidilactici DSPV 006T, was administered with milk replacer. The LAB-G and L-LAB-G received a daily dose of 10⁹ CFU/kg body weight of each strain throughout the experiment. Lactose was provided to the L-LAB-G in doses of 100 g/day. Salmonella Dublin (2 × 10¹⁰ CFU) was orally administered to all animals on day 11 of the experiment. The microscopic lesion index values in target organs were 83%, 70%, and 64.3% (p < 0.05) for the C-G, LAB-G, and L-LAB-G, respectively. Administration of the probiotic inoculum was not fully effective against infection caused by Salmonella. Although probiotic treatment was unable to delay the arrival of pathogen to target organs, it was evident that the inoculum altered the response of animals against pathogen infection.

Quantitative risk assessment of human campylobacteriosis by consumption of salad cross-contaminated with thermophilic Campylobacter spp. from broiler meat in Argentina

Here, we developed a quantitative risk assessment for thermophilic Campylobacter spp. related to the consumption of salad prepared alongside broiler meat. The assessment considered initial contamination levels, cross-contamination and decontamination events during the broiler slaughter process and distribution, and storage and consumption patterns in Argentina and other Latin American countries. The model predicted an infection risk of 3.32×10(-4) per serving. This estimation was variable according to the dose-response model used. Considering the number of chickens slaughtered annually in Argentina, the estimated number of people who could suffer campylobacteriosis related to poultry meat consumption was, on average, 484,304. The risk of human campylobacteriosis was most sensitive to the probability of infection from a Campylobacter (r=0.72), the number of Campylobacter spp. per serving (r=0.40), the frequency of washing the cutting board (r=-0.31), the preparation of raw poultry before salad using the same cutting board (r=0.14), and the frequency of hand washing (r=-0.14). The most sensitive stages of the process identified through the risk assessment can be used as a basis for measures of risk management. Public campaigns on hygiene habits during food preparation at home should focus on the importance of washing the cutting board before preparing raw and ready-to-eat foods and of washing the hands during food preparation.

Association between milking practices and psychrotrophic bacterial counts in bulk tank milk

The objective of this work was to determine on-farm risk factors for psychrotrophic bacterial counts in bulk tank milk from dairy farms in Argentina. Raw milk samples from bulk tanks of 27 dairy farms were examined for total psychrotrophic counts (TPC), proteolytic psychrotrophic counts (PPC) and lipolytic psychrotrophic counts (LPC) (dependent or outcome variables). A survey recording infrastructure conditions, milking equipment and milking management (independent variables) was performed. Bivariate association proofs and logistic regression analyses were used to determine association between independent variables and psychrotrophic bacterial counts. Milk cooled in plate heat exchangers or barrel tanks were 16.39 and 10.52 times more likely to yield TPC and PPC above the standard established for high quality milk compared with milk cooled in bulk tanks, respectively. Periodic cleaning of cooling tanks (3 times a week or daily) was associated with lower TPC (approximately 1.5 log CFU/ml) than weekly cleaning frequency and farms where milkers did not wash their hands during milking time were 7.81 times more likely to have higher PPC. No association was found between LPC and any of the independent variables. The only variable associated with TPC and PPC in a logistic regression model was the refrigeration system used on the farm. Dairy farms that possessed bulk milk cooling tanks yielded the lowest bacterial counts. Results of this study highlight the importance of both the type of cooling system used on the farm and its adequate hygienic maintenance for obtaining low pshychrotrophic counts at dairy farm.

Exposure assessment of mycotoxins in cow's milk in Argentina

A stochastic simulation model was developed to carry out the first quantitative risk exposure assessment of the mycotoxin level in cow's milk produced in Argentina. The prevalence and concentration of aflatoxin M1 (AFM1), deoxynivalenol (DON) and zearalenone (ZEA) were modeled at various stages through milk processes complying with Argentinean practices. Concentration of AFM1 (0.059ppb), DON (0.338ppb) and ZEA (0.125ppb) in dairy milk were estimated. The proportion of feed samples that exceeded the maximum level accepted by European regulations for AFB1, DON and ZEA were estimated at 25.07%, 0.0% and 8.9%, respectively. The percentage of milk samples that exceeded the maximum level accepted for AFB1 by the MERCOSUR (0.5ppb) and the European Union regulations (0.05ppb) were 0.81 and 32.65, respectively. The probability distribution of AFM1 concentration in milk was affected by the carry-over rate equations applied in the model. Mycotoxin levels in corn silage and concentrated feeds were the factors most correlated with mycotoxin concentrations in milk. Therefore, agricultural practices, crop management and feed production require prompt attention regarding mycotoxin issues.

Impact of probiotic administration on the health and fecal microbiota of young calves: a meta-analysis of randomized controlled trials of lactic acid bacteria

Before weaning, dairy calves are susceptible to many pathogens which can affect their subsequent performance. The use of lactic acid bacteria (LAB) has been identified as a tool to maintain the intestinal microbial balance and to prevent the establishment of opportunistic pathogenic bacterial populations. However, a consensus has not been reached as to whether probiotics may be effective in reducing the prevalence of gastrointestinal diseases in young calves. The aim of this meta-analysis was to assess the effect of probiotics on diarrhea incidence and the intestinal microbial balance. LAB supplementation has been shown to exert a protective effect and to reduce the incidence of diarrhea (relative risk, RR=0.437, 95% confidence interval (CI) 0.251-0.761). In the subanalysis, this protective effect of the probiotics against diarrhea was observed only in trials that used whole milk (RR=0.154, 95% CI 0.079-0.301) and trials that used multistrain inocula (RR=0.415, 95% CI 0.227-0.759). Probiotics did not improve the fecal characteristics (standardized mean difference, SMD=-0.4904, 95% CI -1.011-0.035) and were unable to change the LAB:coliforms ratio (SMD=0.016, 95% CI -0.701-0.733). Probiotics showed a beneficial impact on the LAB:coliforms ratio in the subanalysis that included trials that used whole milk (SMD=0.780, 95% CI 0.141-1.418) and monostrain inocula (SMD=0.990, 95% CI 0.340-1.641). The probability of significant effects (probiotic positive effect) in a new study was >0.70 for diarrhea and fecal consistency. Whole milk feeding improved the action of the probiotic effect on the incidence of diarrhea and LAB:coliforms ratio. The probability to find significant effects in the diarrhea frequency and LAB:coliforms ratio was higher (P>0.85) if the new studies were conducted using whole milk to feed calves. This paper defines the guidelines to standardize the experimental designs of future trials. LAB can be used as growth promoters in calves instead of antibiotics to counteract the negative effects of their widespread use.

[Quantitative risk model for verocytotoxigenic Escherichia coli cross-contamination during homemade hamburger preparation]

The objective of this study was to develop a quantitative risk model for verocytotoxigenic Escherichia coil (VTEC) cross-contamination during hamburger preparation at home. Published scientific information about the disease was considered for the elaboration of the model, which included a number of routines performed during food preparation in kitchens. The associated probabilities of bacterial transference between food items and kitchen utensils which best described each stage of the process were incorporated into the model by using @Risk software. Handling raw meat before preparing ready-to-eat foods (Odds ratio, OR, 6.57), as well as hand (OR = 12.02) and cutting board (OR = 5.02) washing habits were the major risk factors of VTEC cross-contamination from meat to vegetables. The information provided by this model should be considered when designing public information campaigns on hemolytic uremic syndrome risk directed to food handlers, in order to stress the importance of the above mentioned factors in disease transmission.

[Hamburger consumption patterns and exposure assessment for verocytotoxigenic Escherichia coli (VTEC): simulation model]

A quantitative risk assessment was developed for verocytotoxigenic Escherichia coli (VTEC) associated with hamburger consumption. The assessment (simulation model) considers the distribution, storage and consumption patterns of hamburgers. The prevalence and concentration of VTEC were modelled at various stages along the agri-food beef production system using input derived from Argentinean data, whenever possible. The model predicted an infection risk of 4.45 x 10(-4) per meal for adults. The risk values obtained for children were 2.6 x 10(-4), 1.38 x 10(-5) and 4.54 x 10(-7) for infection, Hemolytic Uremic Syndrome (HUS) and mortality, respectively. The risk of infection and HUS was positively correlated with bacterial concentration in meat (r = 0.664). There was a negative association between homemade hamburgers (r = -0.116) and the risk of illness; however this association has been considered due to differences between retail and domiciliary storage systems (r = -0.567) and not because of the intrinsic characteristics of the product. The most sensitive points of the production system were identified through the risk assessment, therefore, these can be utilized as a basis to apply different risk management policies in public health.