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.

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.

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.

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.

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.

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.

[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.

Quantification of FITC-labelled probiotic Lactobacillus salivarius DSPV 001P during gastrointestinal transit in broilers

The knowledge related to the fate of probiotics in the complex environment of the intestinal microbiota in broilers is just beginning to be elucidated; however, it is not yet well understood. A good method to investigate the mechanisms by which probiotics mediate their effects is to mark probiotic bacteria and trace them. The aim of this research was to develop a new method to estimate in vivo fluorescein isothiocyanate (FITC)-labelled Lactobacillus salivarius DSPV 001P counts during passage through the gastrointestinal tract (GIT) of broilers. Forty-five, 1 d old Cobb broilers were used in this trial. Programmed necropsies were performed 30 min, 6 h, and 12 h after the administration of the probiotic bacterium, and samples of liver, crop, duodenum, caecum, and bursa of fabricius were collected. To determine the spatial and temporal transit of L. salivarius DSPV 001P in broilers, the number of bacteria as well as its respective fluorescent signal produced by FITC were measured. In order to observe the relationship between the variables, a logistic regression analysis was applied. The amount of fluorescence could be used as an indicator of fluorescent probiotic bacteria in the crop and duodenum 30 min after probiotic bacterium supplementation. In addition, the fluorescent signal could be used to estimate bacterial counts in caecum 6 and 12 h after L. salivarius DSPV 001P administration. To the best of our knowledge, this research is the first in vivo trial to employ the bacterial FITC-labelling technique in order to enumerate probiotic bacteria during gastrointestinal transit in broilers.

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.

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.

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.

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.

Dynamics of Moraxella bovis infection and humoral immune response to bovine herpes virus type 1 during a natural outbreak of infectious bovine keratoconjunctivitis in beef calves

Infectious bovine keratoconjunctivitis (IBK) is an acute disease caused by Moraxella bovis (Mb). Several factors may predispose animals to an IBK outbreak; one commonly observed is infection with bovine herpes virus type 1 (BHV-1). The aim of this study was to investigate the dynamics of BHV-1 virus infection and its relation with clinical cases of IBK in weaned calves from a beef herd with a high prevalence of lesions caused by Mb. Sampling was carried out in six stages and included conjunctival swabs for isolating Mb as well as blood samples for identifying antibodies specific for BHV-1. A score for IBK lesions after observing each eye was determined. The findings of this study showed a high prevalence of BHV-1 virus infection (100% of animals were infected at the end of the trial); 67% of animals were culture-positive for Mb, but low rates of clinical IBK (19% of calves affected) were detected at the end of the trial. These results suggest that infection with BHV-1 did not predispose these animals to IBK, and that Mb infection produced clinical and subclinical disease in the absence of BHV-1 co-infection.

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.