Risk factors for Salmonella persistence after cleansing and disinfection in French broiler-chicken houses

Salmonella Infantis outbreak on six broiler units in Great Britain: investigation, epidemiology, and control

AIMS

To describe the analysis, epidemiology, and control of six contemporaneous and linked outbreaks of Salmonella enterica subsp. enterica serovar Infantis on British broiler farms. Salmonella Infantis is a potentially multidrug-resistant foodborne zoonosis and can persistently colonize poultry flocks and farms.

METHODS AND RESULTS

Routine monitoring initially identified the organism, which was tracked to six farms associated with a single company. Extensive, repeat sampling identified widespread and, in some cases, persistent contamination. Salmonella Infantis was also isolated from three associated processing factories and catching crew equipment, but not from associated hatcheries and feed mills. Whole genome sequencing and resistance phenotyping revealed one strain was present in the processing plants and on five farms. However, on one of those farms, several highly genetically distinct strains were also detected, including one also found in one of the processing plants. The sixth farm had a strain that was genetically unrelated to strains collected from the other premises and which exhibited an extended spectrum beta-lactamase phenotype. Cleaning and disinfection were enhanced, and the organism was eventually cleared from all farms.

CONCLUSIONS

There were multiple incursions of varied strains, with a possible link to processing factories. Elimination of S. Infantis from premises can be challenging but achievable.

Making the invisible visible: Effectiveness of a training program to increase awareness and biosecurity compliance in poultry barn anterooms, using glowing substances

Biosecurity is the cornerstone of prevention strategies to limit infectious pathogen spread between poultry farms. However, poor compliance of biosecurity measures is often observed when entering or exiting barns. The lack of knowledge, understanding, risk perception or technical skill are often described for anteroom-related biosecurity errors (i.e., not respecting anteroom zoning in relation to changing boots, clothing, and hand sanitation). In this study, we designed and assessed the efficacy of an intervention aiming at improving biosecurity compliance in anterooms, using substances glowing under ultraviolet light, which mimic microbiological contamination. Training exercises offered in a single session were proposed to 145 participants with an interest in animal farming (veterinary students, agricultural students, poultry farmers and poultry farm advisors). The exercises' efficacy was assessed by measuring the change in attitude and intentions of participants about specific biosecurity measures. The participants' attitudes and intentions were quantified using a questionnaire before and after training. The change in score was assessed in a multivariate linear regression model to measure the effect of various parameters on this change. The attitudes and intentions of participants were statistically improved (p < 0.05) and were affected by the initial attitude and intention score, the gender of the participants and the status of the participant (type of student or activity in the poultry industry). The use of this exercise material, perceived as playful and engaging, could be included in the framework of biosecurity training for all stakeholders of the poultry industry.

Prevalence, Molecular Detection, and Antimicrobial Resistance of Salmonella Isolates from Poultry Farms across Central Ethiopia: A Cross-Sectional Study in Urban and Peri-Urban Areas

A cross-sectional study was conducted to assess the prevalence, molecular detection, and antimicrobial resistance of Salmonella isolates within 162 poultry farms in selected urban and peri-urban areas of central Ethiopia. A total of 1515 samples, including cloacal swabs (n = 763), fresh fecal droppings (n = 188), litter (n = 188), feed (n = 188), and water (n = 188), were bacteriologically tested. The molecular detection of some culture-positive isolates was performed via polymerase chain reaction (PCR) by targeting spy and sdfl genes for Salmonella Typhimurium and Salmonella Enteritidis, respectively. Risk factors for the occurrence of the bacterial isolates were assessed. Antimicrobial susceptibility testing of PCR-confirmed Salmonella isolates was conducted using 12 antibiotics. In this study, it was observed that 50.6% of the farms were positive for Salmonella. The overall sample-level prevalence of Salmonella was 14.4%. Among the analyzed risk factors, the type of production, breed, and sample type demonstrated a statistically significant association (p < 0.05) with the bacteriological prevalence of Salmonella. The PCR test disclosed that 45.5% (15/33) and 23.3% (10/43) of the isolates were positive for genes of Salmonella Typhimurium and Salmonella Enteritidis, respectively. The antimicrobial susceptibility test disclosed multi-drug resistance to ten of the tested antibiotics that belong to different classes. Substantial isolation of Salmonella Typhimurium and Salmonella Enteritidis in poultry and on poultry farms, along with the existence of multi-drug resistant isolates, poses an alarming risk of zoonotic and food safety issues. Hence, routine flock testing, farm surveillance, biosecurity intervention, stringent antimicrobial use regulations, and policy support for the sector are highly needed.

Genetic Characteristics of Salmonella Isolates Recovered From Reused Broiler Litter Over Three Successive Flocks

Salmonella infections are a leading cause of bacterial food-borne illness worldwide. Infections are highly associated with the consumption of contaminated food, and in particular, chicken meat. The severity of Salmonella infections depends on the presence of antimicrobial resistance genes and virulence factors. While there are many studies which have investigated Salmonella strains isolated from postharvest chicken samples, there is a gap in our understanding of the genetic properties that influence the persistence of Salmonella in preharvest and in particular their makeup of antimicrobial resistance genes and virulence factors. We used whole genome sequencing and hierarchical clustering to characterize and classify the genetic diversity of Salmonella enterica isolates (n = 55) recovered from the litter of commercial broiler chicken raised in four colocated broiler houses of one integrated farm over three consecutive flocks. The chicken were raised under a newly adopted "No Antibiotics Ever" program, and copper sulfate was administered via drinking water. In-silico serovar prediction identified three S. enterica serovars: Enteritidis (n = 12), Kentucky (n = 40), and Senftenberg (n = 3). Antimicrobial susceptibility testing revealed that only one S. Kentucky isolate was resistant to streptomycin, while the remaining isolates were susceptible to all antibiotics tested. Metal resistance operons, including copper and silver, were identified chromosomally and on plasmids in serovar Senftenberg and Kentucky isolates, respectively, while serovar Enteritidis carried several virulence factors on plasmids. Serovar Kentucky isolates harboring metal resistance operons were the only Salmonella isolates recovered from the litter of third flock cohort. These results suggest that there might be environmental selection for Salmonella strains carrying plasmid-associated metal resistance and virulence genes, which could play a role in their persistence in litter.

Survival persistence of the 3 common Salmonella enterica serotypes isolated from broilers' in different matrices

Broiler meat is the predominant source of Salmonella as a foodborne pathogen. Several control strategies have focused on the reduction of Salmonella spp. levels at different production stages. However, the persistence of Salmonella between consecutive flocks is still of great concern. This study was designed to understand the cause of reinfection in broiler flocks due to survival of Salmonella in feeding lines of related matrices. Salmonella (S.) Enteritidis, S. Infantis, and S. Typhimurium isolated from broiler farms in North-West Germany were used. Four types of matrices (phosphate buffer saline (PBS), dietary plant fat, fat with feed mixture, and feed) were applied to evaluate Salmonella survival (with the initial dose about 8.0 log10 CFU/mL) during a simulation of 4 production cycles. To evaluate the growth and survival status of Salmonella ISO 6579-1:2017 were performed (quantitatively by plate count method (PCM) and most probable number method (MPN)) and qualitatively) at 5 defined time points (-7, 0, 4, 7, and 35 d). In all matrices and for the 3 serovars, the Salmonella count decreased at the end of the fourth cycle in comparison to the beginning of the experimental infection, and was still cultivated except for fat matrix. The PBS matrices showed the highest survival level of Salmonella and did not decline drastically by the end of the fourth cycle (5.93 ± 0.00, 5.87 ± 0.02, 5.73 ± 0.05 log10 CFU/mL, respectively). However, the fat matrices showed the lowest survival level for the 3 isolates at d 35 since the first cycle (0 log10 CFU/mL using PCM). Regarding the fat-feed mixture, and feed matrices, there was a fluctuation in the survival rate of Salmonella (all serovars) within each cycle. For the qualitative method, the 3 serovars persisted in all matrices until the end of the fourth cycle except for fat matrices. The present study highlights the ability of Salmonella to survive for a long time in different temperatures and matrices despite efficient cleaning and disinfection processes in the feeding lines, which may influence reinfection with Salmonella in poultry houses.

Biosecurity and Hygiene Procedures in Pig Farms: Effects of a Tailor-Made Approach as Monitored by Environmental Samples

In livestock, the importance of hygiene management is gaining importance within the context of biosecurity. The aim of this study was to monitor the implementation of biosecurity and hygiene procedures in 20 swine herds over a 12-month period, as driven by tailor-made plans, including training on-farm. The measure of adenosine triphosphate (ATP) environmental contents was used as an output biomarker. The presence of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) and extended-spectrum β-lactamase producing Escherichia coli (ESBL-E. coli) was also investigated as sentinels of antibiotic resistance. A significant biosecurity improvement (p = 0.006) and a reduction in the ATP content in the sanitised environment (p = 0.039) were observed. A cluster including 6/20 farms greatly improved both biosecurity and ATP contents, while the remaining 14/20 farms ameliorated them only slightly. Even if the ESBL-E. coli prevalence (30.0%) after the hygiene procedures significantly decreased, the prevalence of LA-MRSA (22.5%) was unaffected. Despite the promising results supporting the adoption of tailor-made biosecurity plans and the measure of environmental ATP as an output biomarker, the high LA-MRSA prevalence still detected at the end of the study underlines the importance of improving even more biosecurity and farm hygiene in a one-health approach aimed to preserve also the pig workers health.

Antibiotic Resistance of Bacterial Isolates from Smallholder Poultry Droppings in the Guinea Savanna Zone of Nigeria

There is a growing risk of antibiotic resistance (AR) in smallholder poultry (SP). This study, therefore, aimed to investigate AR pattern of bacterial isolates from SP in the Guinea Savanna agro-ecological zone of Nigeria. A total of 120 fresh poultry droppings were aseptically collected, randomly, from two tropically adapted (FUNAAB Alpha and Noiler) and local chickens. The chickens were raised either using ethnoveterinary medicines (n = 60) or antibiotics (n = 60). Bacterial isolates were characterized and analyzed using standard protocols, and appropriate statistical tools. Compared to Pseudomonas spp. (2.5%) and Klebsiella spp. (5.8%), Salmonella spp. (57.5%) and Escherichia coli (34.2%) were the most prevalent (χ2 = 96.67; p < 0.001). Prevalence of bacterial species was significantly (p = 0.024; Odds Ratio = 2.552) influenced by antibiotics usage. All four species were multi-drug resistant. In total, 30% of the isolates had a multiple AR index ≥ 0.2. Bacterial isolates from FUNAAB Alpha (58.0%) and Noiler (44.0%) were highly resistant to quinolones, while isolates from the local chickens (22.6%) were most resistant to aminoglycosides. Bacterial species isolated from FUNAAB Alpha and local chickens exhibited the lowest and highest percentage of AR, respectively. Clustering of isolates with similar antibiogram revealed inter-species dependence with possibility for inter-species gene transfer. These findings provide a background to investigate the metagenomics of local and improved chickens for AR.

Isolation, identification and antimicrobial susceptibility profile of Salmonella isolated from poultry farms in Addis Ababa, Ethiopia

Background

Salmonella has been found to be the major cause of foodborne diseases and a serious public health problem in the world, with an increasing concern for the emergence and spread of antimicrobial‐resistant strains.

Method

A cross‐sectional study was conducted on poultry and poultry farms in Addis Ababa from February 2016 to April 2016 to determine the occurrence and evaluate the antimicrobial susceptibility profile of Salmonella isolates. A total of 200 samples consisting of the cloacal swab (n = 168), pooled litter (n = 12), hand swab (n = 8), pooled feed and water (n = 12) were collected separately from six poultry farms. The samples were examined for the presence of Salmonella through culturing on bacteriological media. Descriptive statistics, Pearson's Chi‐square (X²) and bivariate logistic regression were used in the analysis of the data. Accordingly, out of 200 samples, 23 (11.50%) were Salmonella positive, of which 21(12.50%) were in cloacal swab and 2(16.67%) in the pooled litter. There was no statistical association between the bacteriological status of sample type and Salmonella positivity (X² = 3.07, P = 0.545). However, there was a statistical association between farms and the rate of Salmonella isolation (X² = 22.21, P ≤ 0.00). The antimicrobial susceptibility testing for Salmonella isolates was conducted following the Kirby–Bauer disc diffusion method (1961).

Results

Out of 23 samples tested, 95.65% of them were resistant to at least one or more antimicrobials. Multiple drug resistances were observed for 69.56% of Salmonella isolates. The highest resistance (73.9%) was observed in kanamycin followed by tetracycline (65.2%) and streptomycin (56.3%). gentamycin was the most effective antibiotic (95.7%; sensitivity) followed by ciprofloxacin (78.3% sensitivity) and ampicillin (69.6% sensitivity.

Conclusion

This current study finding indicated that further detailed epidemiological and molecular studies are essential on the frequency and sources of acquisition of resistant genes.

Salmonellosis is an infectious and economically important disease of humans and animals caused by different Salmonella species.

In-depth farm investigations and an exploratory risk factor analysis for the presence of Salmonella on broiler farms in Great Britain

Salmonella is a major cause of foodborne illness across Europe but there has been little recent research on its control in broiler production in Great Britain. Investigations of Salmonella presence on 20 broiler farms and a separate exploratory risk factor analysis involving 36 Salmonella-positive farms and 22 Salmonella-negative farms were carried out to investigate Salmonella contamination and control on broiler farms in Great Britain. Sources of Salmonella persistence on farm and potential risk factors for on-farm contamination were identified, enabling provision of up-to-date advice on Salmonella control to farmers. Twenty broiler farms across England and Wales were intensively sampled over time. Most farms were included in the study after routine testing as part of the Salmonella National Control Programmes (NCPs) identified regulated Salmonella serovars or potential associations with outbreak cases of significance for human health. Across all farms and visits, the highest proportion of Salmonella-positive samples were from areas exterior to broiler houses compared to anterooms or house interiors. Exterior Salmonella-positive samples were primarily collected from the immediate areas around the houses, with the highest proportions being from drainage, farm tracks/driveways, and pooled water. Elimination of Salmonella was variable but was most successful inside affected houses (compared to exterior areas) and for regulated Salmonella serovars under the Salmonella NCPs and high priority Salmonella strains with multi-drug resistances. It is likely that the financial and reputational concerns associated with regulated Salmonella serovars and those of greater public health significance underlie the reason that these serovars were more effectively controlled at farm level, as effective elimination of Salmonella can involve a considerable investment in infrastructure, time and resources. Without perceived direct benefits in eliminating non-regulated Salmonella serovars at farm level it can be challenging to maintain the required motivation and investment. A separate farm-level risk factor analysis was carried out using data collected from 58 broiler farms representing six GB broiler companies. Risk of testing positive for Salmonella via NCP sampling in the previous year was greater in the absence of house-specific anterooms and if at least some poultry houses were surrounded by soil/grass compared to if all were surrounded by concrete or a mixture of concrete and stones/gravel. Odds of testing positive for Salmonella in the previous year was also greater for farms whose maximum holding capacity was >100,000 birds, and farms where the usual number of visitors per day was 0-1 compared to 2-3. The analysis was exploratory and caution is required with interpretation, but results provide preliminary insight into aspects of farm management that may be important, practicable targets for Salmonella control on broiler farms in GB.

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.

Risk factors for Salmonella enterica subsp. enterica persistence in broiler-chicken flocks on Reunion Island

This study was conducted to identify the main risk factors for Salmonella spp. persistence in broiler flocks in Reunion Island. Seventy broiler farms were surveyed from March 2016 to June 2018. Samples of fresh droppings were collected using gauze socks, and a questionnaire was completed with the farmers. Persistence was defined as an infection with the same serovar before and after cleaning and disinfection (C/D) of poultry houses. Salmonella spp. was found to persist on 27% of the farms. Cleaning concrete surrounding areas (OR = 0.23) and disinfecting silos (OR = 0.17) reduced the risk of pathogen persistence. An analysis of infections of pests found in the vicinity of the farms confirmed their role in the persistence of Salmonella spp. Fifteen percent of the pests were infected and the presence of mealworms in poultry litter (OR = 6.69) was found to increase the risk of Salmonella spp. persistence. We conclude that improved cleaning-disinfection, sanitary preventive measures and pest control in the poultry sector are needed to avoid the persistence of Salmonella spp. on broiler farms.

Modeling Salmonella Spread in Broiler Production: Identifying Determinants and Control Strategies

The presence of Salmonella spp. in broiler production is a food safety concern as the bacterium can be transmitted to humans via contaminated meat and derived products. Salmonella detection in litter at the pre-slaughter period has been linked to increased odds of contaminated broiler carcasses and meat derived products. To determine risk factors related to farm and broiler house characteristics and management practices, this study uses a unique longitudinal data set from a Brazilian integrated broiler enterprise, which contains official results of Salmonella spp. isolation from drag swabs collected at the end of the grow-out period. A Bayesian hierarchical spatio-temporal model found significant spatial and time influence on the odds of isolating Salmonella spp. from litter as well as significant effects from the size of a broiler house, total housing area per farm, type of broiler house, and number of litter recycles. Results indicate that recycling litter beyond 6 rearing cycles significantly increased the odds of isolating Salmonella before slaughter, and the bacterium was more likely to persist in conventional broiler houses, compared to broiler houses with controlled environment. Evidence of a potential principal-agent problem was also found in setting strategies to control the bacterium from litter, which suggests strong incentives to adopt the strategies aiming to reduce prevalence of the bacterium in the integrated enterprise. Our findings could be used to develop alternative measures to reduce the risk of persistence of the bacterium in the broiler production chain.

Individual training for farmers based on results from protein and ATP rapid tests and microbiological conventional cultural methods improves hygiene in pig fattening pens

Optimal hygiene management is an essential part of maintaining a high standard of health in conventional pig production systems and for the successful interruption of infection chains. Currently, efficiency assessments on cleaning and disinfection are only performed by visual inspection or are neglected completely. The aim of this study was to evaluate the available methods for on farm monitoring of hygiene, identify critical points in pig pens and use the data obtained for training purposes. In addition to visual inspection by assessing the cleanliness, microbiological swab samples, i.e., aerobic total viable count (TVC), total coliform count, methicillin-resistant Staphylococcus aureus (MRSA), and extended-spectrum β-lactamases-producing bacteria (ESBL), swab samples for ATP as well as protein residues and agar contact plates combined with 3 different culture media, were applied and ranked according to their suitability for livestock farming. Samples were collected on at least 15 critical points from one representative pen on 6 pig fattening farms with various hygiene management practices after cleaning and disinfection. After the first sampling, farmers were trained with their individual results, and sampling was repeated 6 mo after training. Nipple drinkers, feeding tubes (external and inner surface), and troughs (external and inner surface) showed the greatest bacterial loads (TVC: 4.5-6.7 log10 cfu cm-2) and values for ATP and protein residues; therefore, these surfaces could be identified as the most important critical points. Spearman rank correlations (P < 0.01) were found between the different assessment methods, especially for the TVC and ATP (r = 0.82, P < 0.001). For rapid assessment on farms, ATP tests represented an accurate and cost-efficient alternative to microbiological techniques. Training improved cleaning performance as indicated by a lower rating for visual inspection, TVC, ATP, MRSA, and ESBL in the second assessment. The monitoring of cleaning efficiency in pig pens followed by training of the staff constitutes a valuable strategy to limit the spread of infectious diseases and antibiotic-resistant bacteria. Special attention should be paid to the sufficient hygiene of drinkers and feeders.

Persistent contamination ofSalmonella,Campylobacter,Escherichia coli, andStaphylococcus aureusat a broiler farm in New Zealand

Intensive poultry production due to public demand raises the risk of contamination, creating potential foodborne hazards to consumers. The prevalence and microbial load of the pathogens Campylobacter, Salmonella, Staphylococcus aureus, and Escherichia coli was determined by standard methods at the farm level. After disinfection, swab samples collected from wall crevices, drinkers, and vents were heavily contaminated, as accumulated organic matter and dust likely protected the pathogens from the disinfectants used. The annex floor also showed high microbial concentrations, suggesting the introduction of pathogens from external environments, highlighting the importance of erecting hygiene barriers at the entrance of the main shed. Therefore, pathogen control measures and proper application of disinfectants are recommended as intervention strategies. Additionally, quantitative polymerase chain reaction (qPCR) was evaluated as a quantification tool. qPCR showed limitations with samples containing low microbial counts because of the low detection limit of the method. Thus, bacterial pre-enrichment of test samples may be necessary to improve the detection of pathogens by qPCR.

Prevalence and related factors of Salmonella spp. and Salmonella Typhimurium contamination among broiler farms in Kerman province, Iran

Salmonella is one of the most important pathogens in the poultry industry that not only causes financial and economic damage, but also, some serovars of this bacterium, including the S. Typhimurium, can infect humans through poultry-to-human transmission. The purpose of this study was to investigate the prevalence of this pathogen among broiler poultry houses in the Kerman region, southeast of Iran and to identify factors which could increase the risk for Salmonella contamination in the chickens. In a cross-sectional study, 110 poultry houses were surveyed from June to October 2018. Twenty-eight variables related to the prevalence of Salmonella contamination were considered by a questionnaire template with farmers' and laborers' help. Also, the prevalence of Salmonella in poultry manure was determined based on fecal sampling, microbiological tests and polymerase chain reaction (PCR) technique. A multivariable logistic regression model was developed to measure the influence of independent variables on Salmonella contamination. Results showed that a time interval less than one month between the two breeding periods (OR = 6.530), the number of fans less than 5 in each poultry house (OR = 4.094) and the number of houses less than 4 in each farm significantly increased the probability of infection with Salmonella spp. (ORs were respectively 9.650, 29.427 and 7.140 for one, two and three houses). Also, the results of multivariable logistic regression showed that the use of a bell drinking system (OR = 4.379) and the presence of fewer than 5 fans in each poultry house (OR = 2.512) increased significantly the risk of infection with Salmonella Typhimurium.

Longitudinal study reveals persistent environmental Salmonella Heidelberg in Brazilian broiler farms

The vast capacity for maintenance and dissemination in the environment are major challenges for the control of Salmonella spp. in poultry farms. The aim of this study was to assess environmental contamination by non-typhoidal Salmonella in successive broiler flocks in nine commercial broiler farms integrated with three companies in the south of Brazil, for a twelve-month production period. Recycled broiler litter, feed and swabs from the evaporative cooling system pads were analyzed, and the total enterobacteria count in the litter samples was ascertained. Positive broiler houses were identified in two of the three broiler companies studied, in which non-typhoidal Salmonella were detected for the first time in the first or second flock, and recurred in the recycled litter of subsequent flocks. Feed and evaporative cooling pad swab samples were also positive in at least one of the assessed flocks. The majority of the isolates (87.5%) originating from different flocks, broiler houses and companies that were sampled were identified as S. Heidelberg, with the prevalence of one single genotype. The total enterobacteria levels in the litter diminished as the flocks progressed, but the presence of Salmonella spp. was constant over the course of time, indicating that the litter management procedures were not capable of interrupting the cycle of residual contamination. The predominance of S. Heidelberg highlights its emergence and dissemination in this region, as well as its resistance and maintenance in the environment, and reinforces the need to improve prevention and recycled litter management measures.

Occurrence, genotypes and antimicrobial susceptibility of Salmonella collected from the broiler production chain within an integrated poultry company

Salmonella is a common foodborne pathogen in the poultry production systems. Its presence in this food industry is determined by the fact that it can survive and pass throughout the different steps in the poultry production. In this study we aimed to study the occurrence, genotypes and antimicrobial resistance of Salmonella collected from the broiler production chain within an integrated poultry company. Three hundred fourteen samples were collected in the feeding plant, farms and the slaughterhouse. Samples were cultured for Salmonella isolation according to the ISO6579/Amd 1. Isolates were further typed by Kauffmann-White scheme and pulse field gel electrophoresis (PFGE). Antimicrobial resistance to 11 antimicrobials was studied by disk diffusion tests and sequencing of ESBL genes. From the collected samples 70 (22%) were found to be Salmonella positive. The lowest Salmonella rates were found in feed samples while in farm and slaughterhouse samples Salmonella presence ranged from 5% to 88%. S. Infantis was the most common serotype (94%, 66/70). PFGE demonstrated that isolates belonged to 11 genotypes. Some genotypes were continuously identified throughout the production chain. 97% of the isolates showed resistance to at least one antimicrobial. Moreover, all S. Infantis isolates and one auto-agglutinable isolate showed resistance to at least 6 antimicrobials. 30 and 8 isolates were positive to bla_CTX-M-65 and bla_CTX-M-14 genes respectively. No bla_KPC resistance genes were identified in any isolate. This study highlights the predominance of S. Infantis in the integrated poultry company. Genotypes showed that cross-contamination between stages of poultry production can occur, stressing the importance of implementing good hygiene practices in every level of the production. Moreover, multidrug resistance patterns and the presence of important ESBL genes have public health implications that need to be deeply discussed with a one health approach.

Salmonella control in poultry flocks and its public health impact

An increase in confirmed human salmonellosis cases in the EU after 2014 triggered investigation of contributory factors and control options in poultry production. Reconsideration of the five current target serovars for breeding hens showed that there is justification for retaining Salmonella Enteritidis, Salmonella Typhimurium (including monophasic variants) and Salmonella Infantis, while Salmonella Virchow and Salmonella Hadar could be replaced by Salmonella Kentucky and either Salmonella Heidelberg, Salmonella Thompson or a variable serovar in national prevalence targets. However, a target that incorporates all serovars is expected to be more effective as the most relevant serovars in breeding flocks vary between Member State (MS) and over time. Achievement of a 1% target for the current target serovars in laying hen flocks is estimated to be reduced by 254,400 CrI95[98,540; 602,700] compared to the situation in 2016. This translates to a reduction of 53.4% CrI95[39.1; 65.7] considering the layer-associated human salmonellosis true cases and 6.2% considering the overall human salmonellosis true cases in the 23 MSs included in attribution modelling. A review of risk factors for Salmonella in laying hens revealed that overall evidence points to a lower occurrence in non-cage compared to cage systems. A conclusion on the effect of outdoor access or impact of the shift from conventional to enriched cages could not be reached. A similar review for broiler chickens concluded that the evidence that outdoor access affects the occurrence of Salmonella is inconclusive. There is conclusive evidence that an increased stocking density, larger farms and stress result in increased occurrence, persistence and spread of Salmonella in laying hen flocks. Based on scientific evidence, an impact of Salmonella control programmes, apart from general hygiene procedures, on the prevalence of Campylobacter in broiler flocks at the holding and on broiler meat at the end of the slaughter process is not expected.

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.

Observations on Salmonella contamination of commercial duck farms before and after cleaning and disinfection

In the European Union, statutory control of Salmonella is in place in the chicken and turkey sectors, but not in the duck sector. In this study, 14 Salmonella-positive duck farms were sampled before and after cleaning and disinfection, and once the houses had been restocked with a new flock. The cleaning and disinfection programmes used were subdivided into two main categories: ones in which a final formaldehyde disinfection step was included (1) and ones in which it was not included (2). Several types of samples were collected during the study, and faecal samples were those more frequently positive (62% of faecal samples were positive for Salmonella in comparison to 2-23% of samples from all the other sample categories) (P < 0.001). Independently of the cleaning and disinfection programme used, there was a statistically significant (P < 0.001) reduction in the percentage of Salmonella-positive samples between before cleaning and disinfection (41.1%) and after cleaning and disinfection (3.1%). After restocking, the number of Salmonella-positive samples increased significantly (P < 0.001), with 65.3% of the samples tested being positive for Salmonella. Farms in which disinfection programme 1 was used were 5.34 times less likely to have samples positive for Salmonella after cleaning and disinfection than farms which implemented programme 2. Formaldehyde acts effectively against Salmonella even in the presence of some residual organic matter. Limited residual contamination on farms after cleaning and disinfection represents a risk of infection for young ducklings, and thorough cleaning and disinfection procedures should be implemented to reduce the carry-over of infection between flocks.

Wild fauna as a carrier of Salmonella in Reunion Island: Impact on pig farms

Salmonellosis is an economic burden to the livestock industry in Reunion Island. In this study, we wanted to improve our understanding of Salmonella epidemiology by studying the wild fauna of Reunion Island. We assessed Salmonella diversity in small non-flying mammals, birds and cockroaches in order to evaluate their potential role in the epidemiology of Salmonella. A total of 268 samples were collected from cockroaches, small mammals and birds. The bacteriological analyses revealed that 11.7% of non-flying mammals and 25% of cockroaches tested were Salmonella infected; two wild bird species were also detected positive. The 128 Salmonella isolates were distributed in fifteen serotypes and the most predominant were S. 4,[5],12:i:- (21.9% of positive samples) followed by S. Enteritidis (15.6%), S. Typhimurium (15.6%), S. Infantis (12.5%) and S. Weltevreden (12.5%). A total of 27 XbaI profiles were identified using pulsed-field gel electrophoresis. Comparison of these Salmonella strains with our collection of Salmonella isolated from pigs and pig farm environments at the same period revealed 14 strains in common between wild fauna and pigs, especially for cockroaches. Our results suggest that wild fauna of Reunion Island could be infected by strains of Salmonella also isolated from pigs or pig environment. They may play a role in both persistence and spreading of Salmonella and therefore, could be a source of infection in pig farms. Pest control against cockroaches could be a helpful tool in the reduction of Salmonella infection of pigs, limiting contacts between wild fauna and both pigs and pig environment. Special attention should be paid to S. 4,[5],12:i:- since it was predominant in Reunion Island's wild fauna and pigs and was the third most frequently reported serotype in human salmonellosis in Europe.

Litter aeration and spread of Salmonella in broilers

Litter quality in the poultry sector is one of the main parameters of health, productivity, and animal welfare. Therefore, innovative management methods have been developed to improve the quality of litter. One of them is litter aeration (LA) by tumbling. However, there is little information related to the effect of this technique on the spreading of pathogens of public health importance such as Salmonella. In this context, the objective of this study was to determine the epidemiology of Salmonella in poultry farms, when serial LA were implemented during the rearing cycle of broilers. For this purpose, an experimental broiler farm with 3 identical rooms was used in the study. Two rooms were assigned to the LA treatment, and the other one served as the control room. Environmental samples were taken in poultry houses after LA in 4 consecutive weeks at the end of the cycle. All samples collected were analyzed according to the standards of the International Organization for Standardization (ISO 6579:2002, Annex D). The results of this study showed that in the control and treated rooms, the percentage of positive samples for Salmonella decreased in the first 3 LA sessions (LA 1, LA 2, and LA 3). However, in the last LA session of rearing (LA 4), the percentage of positive samples increased from 8.2 to 33.2% in the control room instead the treated rooms where the positive samples decreased (P = 0.017). Thus, the aeration of the litter as litter management technique in poultry broiler production does not increase the shedding or the spread of Salmonella throughout broiler houses. In addition, it could be an effective technique to reduce the infective pressure of this bacterium in several areas of the farm or in certain moments of the rearing period with more risk of multiplication and spreading of Salmonella.

Multiblock modelling to assess the overall risk factors for a composite outcome

Research in epidemiology may be concerned with assessing risk factors for complex health issues described by several variables. Moreover, epidemiological data are usually organized in several blocks of variables, consisting of a block of variables to be explained and a large number of explanatory variables organized in meaningful blocks. Usual statistical procedures such as generalized linear models do not allow the explanation of a multivariate outcome, such as a complex disease described by several variables, with a single model. Moreover, it is not easy to take account of the organization of explanatory variables into blocks. Here we propose an innovative method in the multiblock modelling framework, called multiblock redundancy analysis, which is designed to handle most specificities of complex epidemiological data. Overall indices and graphical displays associated with different interpretation levels are proposed. The interest and relevance of multiblock redundancy analysis is illustrated using a dataset pertaining to veterinary epidemiology.

A comparison of the efficacy of cleaning and disinfection methods in eliminating Salmonella spp. from commercial egg laying houses

Effective terminal cleaning and disinfection (C&D) is regarded as a necessary step for the elimination of Salmonella spp. from laying houses. A total of 60 commercial laying houses that had housed laying flocks infected with Salmonella enterica serovar Enteritidis or Salmonella enterica serovar Typhimurium that were representative of all production systems (cage, barn, free-range) were intensively sampled immediately after C&D as well as in the follow-on flock. The procedures investigated were: (1) a compound disinfectant consisting of a mixture of formaldehyde, glutaraldehyde and quarternary ammonium applied at the recommended concentration; (2) a 10% (vol/vol) dilution of the standard 37% commercial formalin, applied by a contractor; and (3) other disinfection procedures selected and applied by the farmer. The recovery of Salmonella in the cleaned and disinfected houses was variable, with samples from floor and dropping boards/belts (cage houses) and scratching areas (non-cage houses) being the most likely to remain contaminated. In cage houses, the use of the 10% formalin dilution led to a statistically greater reduction in the sample prevalence than using any of the other C&D methods. A negative post-C&D result predicted clearance of Salmonella in 52% of cases, although the isolation of Salmonella from the houses immediately after C&D was not a perfect predictor of carry-over of infection.

Salmonella detection in feces during broiler rearing and after live transport to the slaughterhouse

Eggs and poultry meat are a common source of human salmonellosis. Contamination of poultry or poultry meat may occur throughout the production chain. Nevertheless, in Spain, noncontaminated broiler meat may be sold for human consumption from 2011. The aims of this study were as follows: (i) assess Salmonella detection from feces samples during the rearing and (ii) assess the influence of live transport to the slaughterhouse on Salmonella detection. During this study, 65 flocks were sampled at weekly intervals from the first day of rearing until slaughter. Samples of feces were taken from the litter using 5 pairs of cellulose sock swabs attached to boots and applied over the length of the house. To assess Salmonella detection rates before and after live transport to the slaughterhouse, feces samples were collected. Before loading, feces with 5 pairs of cellulose sock swabs were taken as described above. After transport, 2 pooled feces samples were taken directly from the truck (200 to 300 g each). All samples were analyzed in accordance with ISO 6579:2002 (Annex D). Results showed that regardless of whether broiler flocks arrived at the farm already shedding the bacteria in feces or they were infected during rearing, both groups described the same detection pattern, with the highest detection in feces at 14th day of rearing (50.5 and 34.5%, respectively). Moreover, Salmonella Enteritidis was the most prevalent serotype isolated during rearing (66.7%), followed by Salmonella Virchow (13.7%), Salmonella Hadar (9.4%), and Salmonella Ohio (2.8%). On the other hand, before loading and after transport to the slaughterhouse, 15.4 and 41.2% of feces samples collected were determined positive, respectively. In addition, a change in the serotype pattern was also observed. Salmonella Enteritidis remains the most prevalent serotype isolated (54.5%). Salmonella Hadar doubled the excretion rates (39.3%), and Salmonella Virchow and Salmonella Ohio were not isolated after transport.

Salmonella in broiler litter and properties of soil at farm location

Contamination of litter in a broiler grow-out house with Salmonella prior to placement of a new flock has been shown to be a precursor of the flock's Salmonella contamination further down the production continuum. In the southern USA, broiler grow-out houses are primarily built on dirt pad foundations that are placed directly on top of the native soil surface. Broiler litter is placed directly on the dirt pad. Multiple grow-out flocks are reared on a single litter batch, and the litter is kept in the houses during downtime between flocks. The effects of environmental determinants on conditions in broiler litter, hence Salmonella ecology within it, has received limited attention. In a field study that included broiler farms in the states of Alabama, Mississippi and Texas we assessed Salmonella in broiler litter at the end of downtime between flocks, i.e. at the time of placement of a new flock for rearing. Here we utilized these results and the U.S. General Soil Map (STATSGO) data to test if properties of soil at farm location impacted the probability of Salmonella detection in the litter. The significance of soil properties as risk factors was tested in multilevel regression models after accounting for possible confounding differences among the farms, the participating broiler complexes and companies, and the farms' geographical positioning. Significant associations were observed between infiltration and drainage capabilities of soil at farm location and probability of Salmonella detection in the litter.

The risk and control of Salmonella outbreaks in calf-raising operations: a mathematical modeling approach

Salmonellosis in calves has economic and welfare implications, and serves as a potential source of human infections. Our objectives were to assess the risk of Salmonella spread following its introduction into a herd of pre-weaned calves and to evaluate the efficacy of control strategies to prevent and control outbreaks. To meet these objectives, we developed a model of Salmonella transmission within a pre-weaned group of calves based on a well documented outbreak of salmonellosis in a calf-raising operation and other literature. Intervention scenarios were evaluated in both deterministic and stochastic versions of the model. While the basic reproduction number (R0) was estimated to be 2.4, simulation analysis showed that more than 60% of the invasions failed after the introduction of a single index case. With repeated introduction of index cases, the probability of Salmonella spread was close to 1, and the tested control strategies were insufficient to prevent transmission within the group. The most effective strategies to control ongoing outbreaks were to completely close the rearing operation to incoming calves, to increase the proportion of admitted calves that were immunized (>75%), and to assign personnel and equipment to groups of calves.

Observations related to the Salmonella EU layer baseline survey in the United Kingdom: follow-up of positive flocks and sensitivity issues

A follow-on study was carried out on 23 holdings identified as Salmonella positive in the 2004/2005 European Union (EU) baseline survey of Salmonella in laying hens. Eleven of 13 cage and 4/7 floor houses remained positive for Salmonella when the new flock was tested, and from 10/13 cage and 3/7 floor houses a Salmonella of the same serovar/phage type as found in the EU survey was isolated. There was a high correlation between the level of contamination in the houses at the time of the EU survey and in the follow-on flock. On seven occasions the house identified as positive in the EU survey was sampled after cleaning and disinfection but before a new flock was placed, and in all of them Salmonella could be isolated from the houses. The observed number of infected houses in infected holdings suggests that the holding-level prevalence in the United Kingdom would be about 21% higher than the results obtained in the EU survey.

Contamination of carcasses with Salmonella during poultry slaughter

Successively slaughtered poultry flocks were sampled for Salmonella to study the relationship between gastrointestinal colonization of the birds and contamination of the carcasses after slaughter. Samples from 56 broiler flocks and 16 spent layer and breeder flocks were collected in six slaughterhouses. Salmonella isolates were serotyped and further characterized by pulsed-field gel electrophoresis (PFGE). Although only 7 (13%) broiler flocks were colonized with Salmonella at slaughter, carcasses of 31 (55%) broiler flocks were contaminated after slaughter. Concerning the layer and breeder flocks, 11 (69%) flocks were colonized in the gastrointestinal tract, but after slaughter, carcasses of all flocks were contaminated. The Salmonella status determined at the farm did not always correlate to the status at slaughter. On the other hand, the slaughter of Salmonella-colonized flocks did not always result in the contamination of the carcasses with the same PFGE types isolated from the gastrointestinal tract. When only uncolonized flocks were slaughtered, the carcasses of flocks were on some occasions still contaminated with Salmonella. This indicates possible cross-contamination from the slaughter equipment or transport crates. These observations show that it is difficult to reach the benefits of logistic slaughter in commercial poultry slaughterhouses.

Colonization and organ invasion in chicks experimentally infected with Dermanyssus gallinae contaminated by Salmonella Enteritidis

The poultry red mite (Dermanyssus gallinae) is the most important and common ectoparasite of laying hens in Europe. This haematophagous mite has been experimentally demonstrated to be a vector of Salmonella Enteritidis by acquiring bacteria through the blood meal or cuticular contact. We have evaluated another route of infection by orally inoculating chicks with mites previously infected by S. Enteritidis. Two methods of infecting the mites were tested: mites contaminated by cuticular contact or during the blood meal. After the washing of mites with paraformaldehyde, groups of 10 Salmonella-contaminated mites were inoculated individually into 1-day-old chicks. The titre of the inoculum suspension was evaluated by crushing mites and followed by bacteriological counting. It was 3x10(4) colony-forming units/chick and 2.7x10(6) colony-forming units/chick, respectively, for cuticular contact and orally mediated contamination of mites. Each bird was found to be positive 12 days post-inoculation. Salmonella colonized the intestinal tracts and invaded the livers and spleens. The caecal content concentration reached a mean level of S. Enteritidis of 8.5x10(4) most probable number (MPN) Salmonella/g. This experiment demonstrated the ability of mites to orally infect 1-day-old chicks with subsequent colonization and multiplication of Salmonella. Consequently, mites infected by S. Enteritidis constitute potential reservoir hosts of this bacterium, allowing it to persist in the poultry house as a source of infection for newly introduced animals. If contaminated mites are found in poultry facilities, effective red mite control should be performed before new batches are introduced into the facility.

Impact of the slaughter line contamination on the presence of Salmonella on broiler carcasses

AIMS

The aim of the study was to assess the impact of Salmonella present on the slaughter line before processing on broiler carcass contamination during processing.

METHODS AND RESULTS

Three Belgian broiler slaughterhouses were each visited twice. Samples were taken from the slaughter line after the cleaning and the disinfection process and before slaughter of the first flock. During the slaughter of the first flock, feathers and neck skins were collected at various points of the slaughter process. Swab samples were also taken from the crates in which the birds were transported. In two slaughterhouses, the slaughter line was contaminated with Salmonella before the onset of slaughter, especially the shackles, conveyer belt and the plucking machine in the dirty zone. During slaughter, the carcasses of the first Salmonella-free flock became contaminated with the same strains as isolated previously from the slaughter line.

CONCLUSION

Contamination of the slaughter line with Salmonella leads to carcass contamination.

SIGNIFICANCE AND IMPACT OF THE STUDY

Implementation of logistic slaughter is only successful when the cleaning and disinfection process completely eliminates the Salmonella contamination of the slaughter line. Only if this is achieved, will the slaughter of Salmonella-free flocks result in the absence of Salmonella on the carcasses after slaughter.

Comparison of Salmonella enterica serotype Infantis isolates from a veterinary teaching hospital

AIMS

To compare Salmonella enterica serotype Infantis isolates obtained from patients or the environment of a veterinary teaching hospital over a period of 9 years following a nosocomial outbreak to determine whether isolates were epidemiologically related or represented unrelated introductions into the hospital environment.

METHODS AND RESULTS

Fifty-six S. Infantis isolates were compared based on their phenotypic (antimicrobial drug [AMD] susceptibility pattern) and genotypic (pulsed-field gel electrophoresis [PFGE] pattern and presence of integrons) characteristics. Epidemiologically unrelated S. Infantis isolates clustered separately from all but two of the hospital isolates, and several isolates from different years and various sources were indistinguishable from each other in cluster analysis of two-enzyme PFGE results. A high percentage of isolates (80.3%) were resistant to at least one AMD, with 67.8% showing resistance to >5 AMD. The majority (74.1%) of isolates tested contained type 1 integrons.

CONCLUSION

Results strongly suggest that there was nosocomial transmission of S. Infantis during the initial outbreak, and that contamination arising from this outbreak persisted across years despite rigorous hygiene and biosecurity precautions and may have led to subsequent nosocomial infections.

SIGNIFICANCE AND IMPACT OF THE STUDY

Evidence of persistence and transmission of Salmonella clones across years, even in the face of rigorous preventive measures, has important implications for other facilities that have experienced outbreaks of Salmonella infections.