Evaluation of commonly-used farm disinfectants in wet and dry models of Salmonella farm contamination

Effect of implementing an effective farrowing accommodation hygiene routine on clinical cases of disease, medication usage, and growth in suckling and weaned pigs

The few studies that have evaluated hygiene routines in farrowing accommodation to date have focused on pathogen elimination from pens, with little attention paid to pig growth and no information provided on pig health or medication usage. This study aimed to determine if implementation of an optimized farrowing accommodation hygiene routine could improve pig health and growth and reduce medication usage pre- and post-weaning (PW). Forty seven sows were blocked on parity, previous litter size and body weight and assigned to two treatments: T1) Basic hygiene: cold water washing only with minimal drying time; T2) Optimized hygiene: use of detergent and a chlorocresol-based disinfectant with a 6-d drying time. Total bacterial counts (TBC), Enterobacteriaceae counts and adenosine triphosphate (ATP) swabs were obtained from different areas within the farrowing pens. Pig growth and medication usage were monitored from birth to slaughter and carcass data were obtained at slaughter. On entry of sows to the farrowing pens, TBC and Enterobacteriaceae counts and ATP concentrations were lower on pen surfaces subjected to the optimized compared to the basic hygiene routine (P < 0.05). Pre-weaning diarrhea prevalence was lower in pigs born into optimal compared to basic hygiene pens (0 vs. 22%; P < 0.001). The number of clinical cases of disease and injections administered to piglets per litter was 75% and 79% less for the optimized compared to the basic hygiene routine, respectively (P < 0.001). This led to reductions of 77% (P < 0.001) and 75% (P < 0.01), respectively in the volume of antibiotics and anti-inflammatories administered per litter in the optimized hygiene group. Pigs from the optimized hygiene treatment were also heavier at weaning (P < 0.01) and their average daily gain (ADG) was higher from day 21 to weaning and days 22 to 49 PW (P < 0.05). However, these growth improvements did not carry through to the finisher period. In conclusion, implementation of an optimized hygiene routine reduced the bacterial load in farrowing pens, leading to a reduction in diarrhea and clinical cases of disease and therefore, medication usage, in suckling pigs. Pig growth was also improved during the suckling and early PW periods. Based on the results, an easily implementable farrowing room hygiene protocol with demonstrable benefits for pig health, growth, and welfare can be provided to farmers.

Study of Salmonella spp. from Cage Papers Belonging to Pet Birds in an Argentinean Canary Breeder Championship

Birds, including canaries and other birds, have become increasingly popular as pets. Bird fairs, where breeders gather and show their production in a championship setting, present a setting for possible Salmonella spp. contamination and transmission. Therefore, this study estimated the rate of Salmonella spp. isolation from cage papers, located in the bottom of cages of exotic pet birds, including canaries. Collected Salmonella isolates were used to determine the antimicrobial resistance profile to 52 antibiotics and 17 commercial disinfectants, based on pure or a mixture of acids, alcohols, aldehydes, alkalis, halogens, peroxygen, and quaternary ammonium compounds. The samples consisted of 774 cage papers taken in the 2015 Argentinean canary breeder championship, pooling three cage papers into one sterile sampling bag. Only one pool of the cage papers was positive for Salmonella spp. (0.4%), which belonged to the sample from three frill canary cages. Two strains of Salmonella serotype Glostrup were isolated, which were only resistant to sulfonamides and erythromycin and sensitive to alkali-based product PL301 AS. Although the rate of Salmonella spp. isolation from cage papers in an Argentinean canary breeder championship is low, it should not be discounted because Salmonella ser. Glostrup can be a source of human Salmonella outbreaks and they show high resistance to disinfecting products.

Variations in the Physical Properties and Microbial Community of Dairy Cow Manure-Implications for Testing and Efficacy of Footbathing Products

Footbaths containing disinfectants are used on dairy farms to reduce the spread of digital dermatitis; however, they commonly become contaminated with manure. This trial investigated the physical properties and microbial composition of dairy cow manure from two production systems and examined whether the source of manure impacted the efficacy of footbathing disinfectants. Manure was collected from eighteen dairy cows, nine housed and fed grass silage (HOUSED) and nine at pasture (PASTURE). The pH and dry matter content was determined, total DNA was extracted and the region v3-v4 of the 16s rRNA gene sequenced. The efficacy of formalin and two trial products (TP1: peracetic acid and hydrogen peroxide; TP2: chlorocresol and triamine) was evaluated when mixed with manure from the two production systems. Production system differences were found in manure dry matter content, bacterial microbiome and the efficacy of both trial footbathing products but not formalin. The properties of manure affected the results of laboratory testing and therefore have the potential to influence footbathing disinfectant efficacy when footbaths are contaminated with manure. Further research into the impact of organic contaminants on the efficacy of disinfectants could facilitate the development of improved testing programmes and disinfectant products.

Antimicrobial and Antibiofilm Effect of Commonly Used Disinfectants on Salmonella Infantis Isolates

Salmonella enterica subsp. enterica serovar Infantis is the most prevalent serovar in broilers and broiler meat in the European Union. The aim of our study was to test the biofilm formation and antimicrobial effect of disinfectants on genetically characterized S. Infantis isolates from poultry, food, and humans. For the biofilm formation under various temperature conditions (8 °C, 20 °C, and 28 °C) and incubation times (72 h and 168 h), the crystal violet staining method was used. The evaluation of the in vitro antimicrobial effect of Ecocid^® S, ethanol, and hydrogen peroxide was determined using the broth microdilution method. The antibiofilm effect of subinhibitory concentration (1/8 MIC) of disinfectants was then tested on S. Infantis 323/19 strain that had the highest biofilm formation potential. Our results showed that the biofilm formation was strain-specific; however, it was higher at 20 °C and prolonged incubation time. Moreover, strains carrying a pESI plasmid showed higher biofilm formation potential. The antibiofilm potential of disinfectants on S. Infantis 323/19 strain at 20 °C was effective after a shorter incubation time. As shown in our study, more effective precautionary measures should be implemented to ensure biofilm prevention and removal in order to control the S. Infantis occurrence.

Efficacy of Five Disinfectant Products Commonly Used in Pig Herds against a Panel of Bacteria Sensitive and Resistant to Selected Antimicrobials

The growing threat of antimicrobial resistance worldwide has led to an increasing concern in the human, veterinary, and environmental fields, highlighting the need for strategies to effectively control bacterial contamination. Correct biosecurity practices, including the appropriate use of disinfectants, play a crucial role in controlling bacterial contamination. This study aimed to verify whether the recommended concentrations defined according to the Defra General Orders concentration (GO, published by the UK Department for Environment, Food and Rural Affairs' disinfectant-approval scheme) of five commercial disinfectant preparations (peroxygen-based, phenol-based, two halogen-releasing agents, and glutaraldehyde/quaternary ammonium compound-based; disinfectants A to E, respectively) were sufficient to inhibit growth and inactivate selected bacterial strains, including some that carry known phenotypic patterns of multidrug resistance. The effectiveness of each disinfectant was expressed as the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values, determined by the broth-microdilution method. The results indicate that the type of disinfectant and its concentration influence the inhibitory and bactericidal efficacy. The glutaraldehyde/quaternary ammonium compound-based (disinfectant D) and chlorocresol-based products (disinfectant B) were the most effective, and the GO concentration was bactericidal in all the strains tested. The efficacy of the other compounds varied, depending on the bacterial species tested. The GO concentrations were at least able to inhibit the bacterial growth in all the products and bacterial strains tested. A greater tolerance to the compounds was observed in the strains of E. coli with multidrug-resistance profiles compared to the strains that were sensitive to the same antimicrobials.

Disinfectant testing for veterinary and agricultural applications: A review

Disinfectants for veterinary and livestock use, plus skin antiseptics, are critical elements for the control of infectious agents, including zoonotic and antimicrobial-resistant micro-organisms, in managed animal species. Such agents impact animal welfare, economic performance and human health. Testing of disinfectants is needed for safety, efficacy and quality control. The present review examines the principal types of test (carrier, suspension, surface and field) that have been developed or attempted, plus the features inherent in the respective tests, particularly with respect to variability. Elements of testing that have to be controlled, or which can be manipulated, are discussed in the context of real-world scenarios and anticipated applications. Current national and international testing regimes are considered, with an emphasis on the UK, continental Europe and North America, and with further detail provided in the Supporting Information. Challenges to disinfectant efficacy include: the nature of the biological targets (bacteria, fungi, yeasts, spores, viruses and prions), the need for economical and safe working concentrations, the physical and chemical nature of contaminated surfaces, constraints on contact times and temperatures, the presence of organic soil and other barrier or neutralising substances (including biofilms), and thoroughness of pre-cleaning and disinfectant application. The principal challenges with veterinary disinfectant testing are the control of test variability, and relating test results to likely performance in variable field conditions. Despite some ambitions to develop standardised field tests for disinfectants, aside from skin antiseptic trials the myriad problems such tests pose with respect to cost, reproducibility and generalisability remain intractable.

Factors associated with Salmonella enterica and Escherichia coli during downtime in commercial broiler chicken barns in Ontario

Salmonella enterica and Escherichia coli are bacteria of concern to veterinary public health and poultry health. Our research aimed to determine the factors associated with S. enterica and E. coli in commercial broiler chicken barns during the rest period between flocks to identify the best methods of sanitation for bacterial load reduction. This involved collecting samples from September 2015 to July 2016 from the floors of 36 barns before sanitation (baseline) and at 2 time intervals after sanitation, followed by microbiological and molecular analysis. A priori variables of interest included sanitation procedure (dry cleaning, wet cleaning, disinfection), sampling point (baseline, 2 d after sanitation, 6 d after sanitation), and flooring type (concrete, wood). The odds of detecting S. enterica were higher on wooden floors that were wet-cleaned than on concrete floors that were dry-cleaned, lower in the winter and spring than in the fall, and lower when samples were collected 2 d and 6 d after sanitation than at baseline. For E. coli, the concentration was higher on wooden floors than on concrete floors and in the summer than in the fall, and it was lower in postsanitation samples from disinfected barns than in presanitation samples from dry-cleaned barns and in the winter than in the fall. Among E. coli isolates, factors associated with the presence of qacEΔ1, a gene associated with resistance to quaternary ammonium compounds, included sanitation procedure, flooring type, cycle length, and the number of times per yr the barn is disinfected. Our findings highlight the importance of cleaning after litter removal, although the sanitation procedure chosen might differ depending on which pathogen is present and causing disease issues; dry cleaning appears to be preferable for S. enterica control, especially in barns with wooden floors, whereas disinfection appears to be preferable for E. coli reduction.

Poisoning of glutaraldehyde-containing products: clinical characteristics and outcomes

OBJECTIVE

This study describes the clinical characteristics, outcomes, and factors at presentation associated with death of cases poisoned by glutaraldehyde (GA)-containing products.

METHODS

We performed a 5-year retrospective cohort study (July 2013-June 2018) using data from the Ramathibodi Poison Center.

RESULTS

There were 244 cases included in this study. Most were men with a median age of 37 years. The GA-containing products were mainly used as farm disinfectants (99.2%), with a median concentration of 15%. Most products (76.2%) contained co-formulants such as cationic detergents and formaldehyde.Most circumstances were accidental (56.9%). The others were suicide attempts by ingestion, except one patient who intentionally injected GA subcutaneously. The most common route of exposure was ingestion (95.0%). Local symptoms in areas of exposure were common. Ingestion resulted in more severe local effects than other routes, and corrosive effects occurred in 23 cases (9.4%). Systemic signs and symptoms occurred in 149 patients (61.1%). Systemic effects included abnormal vital signs, desaturation, altered mental status, hypo/hypernatremia, hypokalemia, low bicarbonate/metabolic acidosis, acute kidney injury (AKI), hepatitis, and rhabdomyolysis. Systemic effects mostly resulted from ingestion. Most patients had mild severity, received only supportive treatment, and fully recovered. The median length of hospital stay was 2 days. The one case of subcutaneous injection developed both local and systemic effects but survived. The mortality rate was 3.7%. Multivariate analysis indicated that either neurological symptoms or AKI at presentation were associated with death.

CONCLUSIONS

In our study, patients were exposed to GA-containing products that were mainly used as farm disinfectants and were generally co-formulated with other substances. Poisoning with these products commonly resulted in mild local irritative symptoms. However, some cases developed corrosive symptoms, systemic effects, or even died. As neurological symptoms or AKI could prognosticate deaths; physicians should look for these factors in patients with GA exposure at presentation for close monitoring and aggressive treatment.

In-vitro testing of bacteriostatic and bactericidal efficacy of commercial disinfectants against Salmonella Infantis reveals substantial differences between products and bacterial strains

Salmonella (S.) Infantis is currently the most common serovar in broilers and boiler meat in the European Union. In the field, eradication of S. Infantis in affected poultry flocks is considered extremely difficult. Despite stringent cleaning and disinfection measures between the placement of flocks, recurrent infections are often reported. So far, the efficacy of disinfectants on S. Infantis has rarely been studied. Therefore, in the present in-vitro study the bacteriostatic and bactericidal efficacy of ten commercial disinfectants were tested against seven S. Infantis field isolates. Combinations of aldehyde and quarternary ammonium were the active compounds of five, peroxygen of three, cresol and alkylamines of one disinfectant, respectively. Investigations were performed according to standard protocols and regulations. Different concentrations of disinfectants were used to test the bacteriostatic efficacy. Different temperatures and low and high protein exposures were applied as variables to investigate the bactericidal efficacy. Following neutralization of the disinfectants an additional incubation step was introduced to investigate the revitalisation potential of S. Infantis. The bacteriostatic efficacy could be assessed for seven disinfectants. For three disinfectants a bacteriostatic effect was observed when the recommended concentration was used, whereas with four disinfectants only increased concentrations led to this effect. The bactericidal efficacy was not influenced by temperature, whereas high protein exposure decreased the efficacy of nine disinfectants. Furthermore, reactivation of S. Infantis was revealed after application of disinfectants for the majority of products. Interestingly, the strain of S. Infantis influenced the efficacy of the disinfectants. Overall, products based on aldehydes and quarternary ammonium compounds proved most efficient, followed by peroxgen, cresol and alkylamines.

Antimicrobial and Disinfectant Susceptibility of Salmonella Serotypes Isolated from Swine Slaughterhouses

Salmonella remains one of the most common foodborne pathogens worldwide, and its resistance to antimicrobials and disinfectants has increased considerably over the years. Thus, monitoring its resistance to products commonly used in swine production is indispensable for the development of strategies to reduce the occurrence of bacterial resistance. In this context, our aim was to detect Salmonella at different points in swine slaughterhouses, identify the main serotypes, and evaluate their resistance to disinfectants and antimicrobials used in swine production. Salmonella at the processing plants was detected by conventional microbiology. Salmonella strains were tested for susceptibility to peracetic acid (0.5% and 1%), quaternary ammonium (0.5%), and seven antimicrobials. Twenty-eight percent of the samples were positive for Salmonella, with the most identified serotypes being Salmonella Derby, Salmonella Typhimurium, and monophasic Salmonella Typhimurium. All tested strains were susceptible to both concentrations of peracetic acid, but only 28% were susceptible to quaternary ammonium. Sixteen percent of the strains were susceptible to all tested antimicrobials. Only enrofloxacin was efficient in inhibiting the growth of all strains. The highest number of non-susceptible strains was to amoxicillin, followed by chloramphenicol, florfenicol, and doxycycline. Thirty-six percent of the strains were classified as multidrug-resistant. Salmonella were detected in all slaughtering processes, and important serotypes were recovered, including Salmonella Typhimurium, Salmonella Derby, monophasic Salmonella Typhimurium, and Salmonella Infantis. We observed high rates of resistance to quaternary ammonium and to important antimicrobial agents. Salmonella Typhimurium and Salmonella Infantis were the most resistant serotypes.

ESTABLISHMENT OF THE EFFICIENCY OF ANIMAL BREEDING PREMISES DISINFECTION BY MODERN DISINFECTANTS

The technological complex of veterinary-sanitary and organization-economic arrangements, conducted for prophylaxis and fight against infectious diseases inevitably includes disinfection, directed on inactivation of pathogenic agents in the environment. At applying new disinfectants in practice in the whole structure of the technological process of animal husbandry products, it is necessary to determine their sensitivity to the circulating microflora. The aim of the study was to establish the effectiveness of using new disinfecting preparations of different chemical groups and to determine regimes of their application in the whole complex of anti-epizootic prophylactic arrangements. Disinfecting preparations “Hermicidan FF plus”, “Peroxan forte”, “Viro-xal” were used in experiments. The quality of the conducted disinfection was controlled by separation of sanitary-representative microorganisms – bacteria of the colon bacillus group. It has been established, that the disinfecting preparations “Hermicidan FF plus”, “Peroxan forte”, “Viro-xal” have bactericidal properties relative to the sanitary-representative microorganisms and can be used in the general complex of sanitary-hygienic arrangements. The disinfectant “Hermicidan FF plus” has bactericidal properties in concentration 0,5 % at exposition 1 hour, preparation “Peroxan Forte” is effective at using in concentration 1,0 % at exposition 1 hour, and the disinfecting means “Viro xal” acts bactericidially in concentration 1,0 % at exposition 3 hours. For today the question of search for new technological, high-effective disinfecting preparations that correspond to existent requirements of biological safety and protection remains urgent.

Outer Membrane Proteins of Salmonella as Potential Markers of Resistance to Serum, Antibiotics and Biocides

Salmonellosis continues to be a significant worldwide health problem. Despite rapid progress in identifying mechanisms of Salmonella virulence and resistance to chemicals, our knowledge of these mechanisms remains limited. Furthermore, it appears that the resistance to antibiotics can be amplified by ubiquitous usage of the disinfectants (biocides), both by industry and by ordinary households. Salmonella, as other Gram-negative bacteria possess outer membrane proteins (OMPs), which participate in maintaining cell integrity, adapting to environment, and interacting with infected host. Moreover, the OMPs may also contribute to resistance to antibacterials. This review summarizes the role of OMPs in Salmonella serum resistance, antibiotics resistance and cross-resistance to biocides. Although collected data do not allow to assign OMPs as markers of the Salmonella susceptibility to the above-mentioned factors, some of these proteins retain a dominant presence in certain types of resistance.

Antimicrobial Resistance on Farms: A Review Including Biosecurity and the Potential Role of Disinfectants in Resistance Selection

Resistance to therapeutic antimicrobial agents is recognized as a growing problem for both human and veterinary medicine, and the need to address the issue in both of these linked domains is a current priority in public policy. Efforts to limit antimicrobial resistance (AMR) on farms have so far focused on control of the supply and use of antimicrobial drugs, plus husbandry measures to reduce infectious disease. In the United Kingdom and some other countries, substantial progress has been made recently against targets on agricultural antimicrobial drug use. However, evidence suggests that resistant pathogenic and commensal bacteria can persist and spread within and between premises despite declining or zero antimicrobial drug use. Reasons for this are likely complex and varied but may include: bacterial adaptations to ameliorate fitness costs associated with maintenance and replication of resistance genes and associated proteins, horizontal transmission of genetic resistance determinants between bacteria, physical transfer of bacteria via movement (of animals, workers, and equipment), ineffective cleaning and disinfection, and co-selection of resistance to certain drugs by use of other antimicrobials, heavy metals, or biocides. Areas of particular concern for public health include extended-spectrum cephalosporinases and fluoroquinolone resistance among Enterobacteriaceae, livestock-associated methicillin-resistant Staphylococcus aureus, and the emergence of transmissible colistin resistance. Aspects of biosecurity have repeatedly been identified as risk factors for the presence of AMR on farm premises, but there are large gaps in our understanding of the most important risk factors and the most effective interventions. The present review aims to summarize the present state of knowledge in this area, from a European perspective.

Ingestion of bedding material as a cause of acute copper sulfate poisoning in turkey poults

The article reports a case of acute copper sulfate (CuSO4) poisoning in 2-day-old turkeys. The first incidences were noticed 2 h after placing the animals in the poultry house, where turkeys were provided with wood shaving bedding. Post-mortem examination showed wood shavings present in gastric and intestinal contents and numerous lesions in the alimentary tract: dark green color of the koilin lining, and surface erosions, deep ulceration, and severe congestion of the gizzard. The copper (Cu) concentration in samples of the liver, kidney, heart, gizzard content, gizzard muscle, gizzard lining, and wood shavings from the bedding was determined. Our results showed that the level of Cu in the livers of affected birds was more than sevenfold higher than the recommended value and the Cu content in bedding material was above the value considered to be toxic to turkeys. Our investigation identified the bedding disinfected using a CuSO4 solution as a possible cause of turkey fatalities.

Evaluation of the hygienogram scores and related data obtained after cleaning and disinfection of poultry houses in Flanders during the period 2007 to 2014

Cleaning and disinfection (C&D) of poultry houses is an essential aspect in farm hygiene management. Adequate performance of the different steps of a C&D protocol and the use of suitable products are key to prevent and control zoonoses and animal diseases. Hygiene monitoring on total aerobic flora through sampling with agar contact plates at different locations of the poultry house results in a hygienogram score that is used to evaluate the proper execution of C&D.This study analyzed the hygienogram scores of 19,739 poultry flocks in Flanders after C&D. Data relating to the C&D protocol, i.e., year, season, husbandry system, production type, cleaning product, sampler, active components of the disinfectant, disinfection time, disinfection temperature, and disinfection responsible, were collected.The average hygienogram score decreased significantly over time, suggesting a general improvement between 2007 and 2014. Differences in scores were found among the husbandry systems, with the barn/aviary system having a significantly better hygienogram score compared to the floor house, furnished cage, and battery. Significantly better scores also were found when a cleaning product was used in the C&D protocol. Disinfection with a peracetic acid and hydrogen peroxide combination or formaldehyde gave the best scores. In addition, C&D protocols using ≥2 different disinfectants showed improved results compared to the use of one single disinfectant. Finally, disinfection applied by a specialist contractor resulted in a better score compared to disinfection by the farmer.In conclusion, analysis of the hygienogram scores and related data allowed identifying several factors, resulting in an improvement, which may reduce the total bacterial load in poultry stables and, consequently, the number of zoonotic and pathogenic micro-organisms.

Efficacy evaluation of commercial disinfectants by using Salmonella enterica serovar Typhimurium as a test organism

The efficacies of six commercial disinfectants were evaluated by using Salmonella enterica serovar Typhimurium under simulated natural conditions such as sub-zero temperature, short disinfecting time, and surface type (uneven or smooth). We used a suspensionmodel test to determine the disinfecting efficacy under varying contact times (1, 5, 10, and 30 min) and temperatures (25°C, 4°C, 0°C, and -10°C). The bactericidal effect according to surface structure was measured by using a carriermodel test at 25°C and -10°C. The effective concentrations of each disinfectant were fixed to give a disinfecting effect within a short time (< 1 min) at 25°C and -10°C. The suspension model results revealed that bactericidal efficacy significantly dropped at low temperature for most of the disinfectants used; a sodium dichloroisocyanurate product showed the strongest efficacy. In the carrier test, bacterial load on a wooden surface was more difficult to remove than that on a stainless-steel surface. The results show that commercial disinfectant products vary in their disinfecting efficacy, which is affected by several field factors including temperature, contact time, and carrier material. Environmental conditions and surface type for disinfection should be considered prior to selecting an optimal disinfectant in the field.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): Salmonella infection in poultry with serotypes of animal health relevance (S. Pullorum, S. Gallinarum and S. arizonae)

Salmonella infection in poultry (Salmonella Pullorum, Salmonella Gallinarum and Salmonella arizonae) has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on the eligibility of Salmonella to be listed, Article 9 for the categorisation of Salmonella according to disease prevention and control rules as in Annex IV and Article 8 on the list of animal species related to Salmonella. The assessment has been performed following a methodology composed of information collection and compilation, expert judgement on each criterion at individual and, if no consensus was reached before, also at collective level. The output is composed of the categorical answer, and for the questions where no consensus was reached, the different supporting views are reported. Details on the methodology used for this assessment are explained in a separate opinion. According to the assessment performed, Salmonella can be considered eligible to be listed for Union intervention as laid down in Article 5(3) of the AHL. The disease would comply with the criteria as in Sections 4 and 5 of Annex IV of the AHL, for the application of the disease prevention and control rules referred to in points (d) and (e) of Article 9(1). The assessment here performed on compliance with the criteria as in Section 1 of Annex IV referred to in point (a) of Article 9(1) is inconclusive. The main animal species to be listed for Salmonella according to Article 8(3) criteria are all species of domestic poultry and wild species of mainly Anseriformes and Galliformes, as indicated in the present opinion.

Evaluation of an enhanced cleaning and disinfection protocol in Salmonella contaminated pig holdings in the United Kingdom

Salmonella is the second most commonly reported zoonotic gastrointestinal pathogen in the European Union, and a significant proportion of the cases are linked to the consumption of contaminated pork. Reduction of Salmonella at the farm level helps to mininimise the contamination pressure at the slaughterhouse, and therefore the number of Salmonella bacteria entering the food chain. Cleaning and disinfection (C&D) between batches of pigs is an intervention measure that has potential to reduce the transmission of Salmonella contamination within farms. In this study, two pig finisher buildings in each of 10 Salmonella positive farms were sampled pre-C&D, post-C&D, post-restocking with the following batch of pigs, and shortly before these pigs were sent to slaughter. The incoming batch of pigs was also sampled before it reached the study building (pre-restocking). At each visit, pooled and individual faecal samples were collected and Salmonella isolation was carried out according to an ISO 6579:2002 Annex D-based method. One building on each farm (intervention) was cleaned and disinfected according to a rigorous protocol consisting of several steps and a Defra-approved disinfectant used at the General Orders concentration, whilst the other building (control) was cleaned and disinfected as per normal farm routine. At the post-C&D visit, Enterobacteriaceae and total bacterial counts were determined to evaluate residual faecal contamination and general hygiene levels. Rodent specialists visited the farms before and after C&D and rodent carcasses were collected for Salmonella testing. The intervention buildings were significantly less likely (p = 0.004) to be positive for Salmonella after C&D. The pre-restocking pigs had the highest likelihood (p<0.001) of being Salmonella positive (often with multiple serovars) and there was no significant difference between intervention and control buildings in Salmonella prevalence at the post-restocking visit (p = 0.199). However, the pigs housed in the intervention buildings were significantly less likely (p = 0.004) to be positive for Salmonella at slaughter age. Multivariable analysis suggested that cleaning all fixtures of buildings, leaving the pens empty for 2-3 days and using an effective disinfectant are factors significantly improving the likelihood of removing Salmonella contamination during C&D. Signs of rodents were recorded in all farms, but rodent activity and harbourage availability decreased between visits. All the rats tested were Salmonella negative. S. Typhimurium or its monophasic variants were isolated from 6 mouse carcasses in 3 farms where the same serovars were isolated from pigs. This study demonstrates that an appropriate C&D programme significantly reduces the likelihood of residual contamination in Salmonella positive pig buildings, and suggests a significant reduction in the prevalence of Salmonella in the pigs in appropriately cleaned and disinfected buildings when sampled before slaughter. Due to a high prevalence of infection in replacement pigs, control of Salmonella in pig farms is challenging. Rodents may also contribute to the carry-over of infection between batches. C&D is a useful measure to help reduce the number of infected pigs going to the slaughterhouse, but should be supplemented by other control measures along the pig breeding and production chain.

Salmonella Vaccination in Pigs: A Review

The control of Salmonella enterica in pig production is necessary for both public and animal health. The persistent and frequently asymptomatic nature of porcine Salmonella infection and the organism's abilities to colonize other animal species and to survive in the environment mean that effective control generally requires multiple measures. Vaccination is one such measure, and the present review considers its role and its future, drawing on studies in pigs from the 1950s to the present day. Once established in the body as an intracellular infectious agent, Salmonella can evade humoral immunity, which goes some way to explaining the often disappointing performance of inactivated Salmonella vaccines. More recent approaches, using mucosal presentation of antigens, live vaccines and adjuvants to enhance cell-mediated immunity, have met with more success. Vaccination strategies that involve stimulating both passive immunity from the dam plus active immunity in offspring appear to be most efficacious, although either approach alone can yield significant control of Salmonella. Problems that remain include relatively poor control of Salmonella serovars that are dissimilar to the vaccine antigen mix, and difficulties in measuring and predicting the performance of candidate vaccines in ways that are highly relevant to their likely use in commercial production.

Assessment of anti-Salmonella activity of boot dip samples

The introduction of pathogens from the external environment into poultry houses via the boots of farm workers and visitors presents a significant risk. The use of boot dips containing disinfectant to help prevent this from happening is common practice, but the effectiveness of these boot dips as a preventive measure can vary. The aim of this study was to assess the anti-Salmonella activity of boot dips that are being used on poultry farms. Boot dip samples were collected from commercial laying hen farms in the UK and tested within 24 hours of receipt at the laboratory to assess their anti-Salmonella activity. All boot dip samples were tested against a field strain of Salmonella enterica serovar Enteritidis using three test models: pure culture, paper disc surface matrix and yeast suspension model. Of the 112 boot dip samples tested 83.6% were effective against Salmonella in pure culture, 37.3% in paper disc surface matrix and 44.5% in yeast suspension model. Numerous factors may influence the efficacy of the disinfectants. Disinfectants used in the dips may not always be fully active against surface or organic matter contamination; they may be inaccurately measured or diluted to a concentration other than that specified or recommended; dips may not be changed regularly or may have been exposed to rain and other environmental elements. This study showed that boot dips in use on poultry farms are frequently ineffective.

Co-Selection of Resistance to Antibiotics, Biocides and Heavy Metals, and Its Relevance to Foodborne Pathogens

Concerns have been raised in recent years regarding co-selection for antibiotic resistance among bacteria exposed to biocides used as disinfectants, antiseptics and preservatives, and to heavy metals (particularly copper and zinc) used as growth promoters and therapeutic agents for some livestock species. There is indeed experimental and observational evidence that exposure to these non-antibiotic antimicrobial agents can induce or select for bacterial adaptations that result in decreased susceptibility to one or more antibiotics. This may occur via cellular mechanisms that are protective across multiple classes of antimicrobial agents or by selection of genetic determinants for resistance to non-antibiotic agents that are linked to genes for antibiotic resistance. There may also be relevant effects of these antimicrobial agents on bacterial community structure and via non-specific mechanisms such as mobilization of genetic elements or mutagenesis. Notably, some co-selective adaptations have adverse effects on fitness in the absence of a continued selective pressure. The present review examines the evidence for the significance of these phenomena, particularly in respect of bacterial zoonotic agents that commonly occur in livestock and that may be transmitted, directly or via the food chain, to human populations.

A review of the official sampling of flocks of laying hens in the Salmonella National Control Programme in Great Britain

In line with European legislation and the UK National Control Programme for Salmonella, poultry farms are sampled to establish their Salmonella status. Regular samples are collected by the farmer (operator), with annual routine (official) samples being collected by the competent authority to verify achievement of the Salmonella programme reduction target. To confirm sampling was being carried out effectively, a questionnaire-based survey was conducted. The aim was to identify any complicating factors the samplers encountered and the decisions made in these circumstances. There was good compliance with the official sampling visits, with few delays reported. However, farm-specific clothing/separate boots for non-caged houses were rarely provided by the operator, whereas boot dips and hand washing facilities were usually available. The collection of dust was often a problem for official samplers, operator boot swabs were not always moistened before sampling and both sampler groups did not always follow the recommended method for the collection of faeces from belts and scrapers. Overall, there was a good application of the sampling protocol, although a few areas for improvement were identified.

In vitro and in vivo investigation on genomic stability of Salmonella enterica Typhimurium DT41 obtained from broiler breeders in Denmark

Salmonella enterica serovar Typhimurium phage type DT41 has previously been identified from salmonella-positive broiler breeder flocks in Denmark and isolates obtained from different flocks have demonstrated major diversity by multiple-locus variable-number tandem-repeats analysis (MLVA) typing. To elucidate whether the high diversity observed by MLVA was related to multiple independent introductions at farm level or genetic instability of markers, we investigated the genomic stability of different clones of S. Typhimurium DT41. In the in vitro genomic stability experiment, feed pellet- and dust samples inoculated with four strains of DT41 were kept at three different temperatures. The in vitro genomic stability was also assessed by conducting a serial passage experiment. In a subsequent in vivo experiment, broiler breeders of three different age groups were challenged with a strain of poultry and human origin, respectively. The in vitro experiment demonstrated that DT41 survived more than 6 months in feed-pellets at 20 °C whereas the survival in dust was less than 4 weeks. Infection pattern and excretion varied for the poultry and human strain and birds of different age groups as revealed by the in vivo experiment. Genetic stability of cultures obtained from the in vitro and in vivo survival/passage was investigated by plasmid profiling, pulsed-field gel electrophoresis (PFGE) and MLVA. The results of plasmid profiling and PFGE demonstrated genomic stability of all but one strain kept in dust at 20 °C for 3 weeks. Minor genetic changes were observed in isolates from the in vitro experiment as revealed by MLVA. The epidemiological impact of these findings is briefly discussed.

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

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

Salmonella control in live pigs and at slaughter

As European Union legislation sets reduction targets to lower the incidence of human salmonellosis, Member States are obliged to take effective measures to control Salmonella infection and contamination along the pig production chain. This review considers the most important control measures in the primary phase of pig production as well as during transport, lairage and along the slaughter line. Pig feed should be free of Salmonella, and contamination after feed processing must be prevented. Cleaning and disinfection procedures should be improved, although this can be complicated by the development of biofilms and the interaction between Salmonella and protozoa. Further research is required on the acid tolerance response of Salmonella strains regarding the use of organic acids in feed and/or drinking water. Vaccination of sows and piglets can be helpful but can interfere with current serosurveillance as no differentiation can yet be made between naturally infected and vaccinated animals. Fasting, transport and lairage conditions should be critically evaluated and improved. Slaughterhouses must avoid contamination and cross-contamination during all stages of the slaughter process. Scalding by steam and implementing a second singeing step after polishing are beneficial. Attention should be paid to the cleaning and disinfection procedures along the slaughter line. Carcass decontamination is a promising approach, but needs to be considered as a tool to add to good hygiene practices.

Producing Salmonella-free pigs: a review focusing on interventions at weaning

Salmonella infection in pig production is typically endemic and largely asymptomatic. It is a cause of substantial concern among food safety bodies, prompting voluntary and legislative responses aimed at monitoring and reducing the number of Salmonella-infected animals entering the human food chain. Elimination of the problem at an early stage of production is highly desirable, and to this end the present review examines published evidence on the carriage of Salmonella by piglets before and after weaning, as well as evidence on the dynamics of Salmonella infection in the weaner and grower stages of pig production, the effects of maternal immunity, and risk factors for Salmonella excretion after weaning. Various interventions to reduce or eliminate Salmonella infection in young pigs have been tried, such as vaccination, competitive exclusion, treatments in feed and water, antibiotic administration, disinfection of animals, and segregated weaning to clean accommodation. The evidence on the effectiveness of these is considered, and the last is examined in some detail, as it appears currently to offer the best chance of eliminating Salmonella from growing stock.