Evidence that certain clones of Campylobacter jejuni persist during successive broiler flock rotations

A Longitudinal Study on Campylobacter in Conventionally Reared Commercial Broiler Flocks in the United States: Prevalence and Genetic Diversity

Poultry meat contaminated with Campylobacter, a major bacterial cause of foodborne gastroenteritis worldwide, is considered the primary source of human campylobacteriosis. Thus, reduction or elimination of Campylobacter in poultry production will have a significant impact on food safety and public health. Despite the significant progress made over the last decades, many puzzles remain about the epidemiology of Campylobacter on poultry farms, hampering the development of an effective control strategy. This longitudinal study was conducted to determine the prevalence and genetic diversity of Campylobacter in a U.S. commercial broiler production farm system. Cecal contents (15 samples/flock) and boot swabs (3 samples/flock) were collected from approximately 6-wk-old birds from 406 conventional broiler flocks reared in 53 houses on 15 farms (located within a relatively close geographic proximity and managed by the same poultry integrator) for up to eight consecutive production cycles and cultured for Campylobacter. Pulsed-field gel electrophoresis was used to investigate the genetic diversity of the Campylobacter jejuni isolates recovered from the cecal contents. The prevalence of Campylobacter at the farm, house, and flock levels were found to be 93% (14/15), 79% (42/53), and 47% (192/406), respectively. Campylobacter prevalence varied remarkably among different farms and flocks, with some farms or houses testing consistently negative while others being positive all the time over the entire study period. Campylobacter isolation rate changed significantly by sample type (higher by cecal contents vs. boot swabs) and season/production cycle (higher in spring vs. other seasons). The majority (88%; 2364/2675) of the isolates were identified as C. jejuni, and almost all the rest (11%; 303/2675) were Campylobacter coli. Genotyping showed limited diversity within a flock and suggested persistence of some C. jejuni clones over multiple production cycles on the same farm. In conclusion, this study indicated that although Campylobacter prevalence was overall high, there were marked differences in the prevalence among the broiler flocks or farms tested. Future studies aimed at identification of potential risk factors associated with differential Campylobacter status are warranted in order to develop effective on-farm interventions.

Transmission pathways of campylobacter spp. at broiler farms and their environment in Brandenburg, Germany

Broiler meat is widely known as an important source of foodborne Campylobacter jejuni and Campylobacter coli infections in humans. In this study, we thoroughly investigated transmission pathways that may contribute to possible Campylobacter contamination inside and outside broiler houses. For this purpose we carried out a comprehensive longitudinal sampling approach, using a semi-quantitative cultivation method to identify and quantify transmissions and reservoirs of Campylobacter spp.. Three german broiler farms in Brandenburg and their surrounding areas were intensively sampled, from April 2018 until September 2020. Consecutive fattening cycles and intervening downtimes after cleaning and disinfection were systematically sampled in summer and winter. To display the potential phylogeny of barn and environmental isolates, whole genome sequencing (WGS) and bioinformatic analyses were performed. Results obtained in this study showed very high Campylobacter prevalence in 51/76 pooled feces (67.1%) and 49/76 boot swabs (64.5%). Average counts between 6.4 to 8.36 log10MPN/g were detected in pooled feces. In addition, levels of 4.7 and 4.1 log10MPN/g were detected in boot swabs and litter, respectively. Samples from the barn interior showed mean Campyloacter values in swabs from drinkers 2.6 log10MPN/g, walls 2.0 log10MPN/g, troughs 1.7 log10MPN/g, boards 1.6 log10MPN/g, ventilations 0.9 log10MPN/g and 0.7 log10MPN/g for air samples. However, Campylobacter was detected only in 7/456 (1.5%) of the environmental samples (water bodies, puddles or water-filled wheel tracks; average of 0.6 log10MPN/g). Furthermore, WGS showed recurring Campylobacter genotypes over several consecutive fattening periods, indicating that Campylobacter genotypes persist in the environment during downtime periods. However, after cleaning and disinfection of the barns, we were unable to identify potential sources in the broiler houses. Interestingly, alternating Campylobacter genotypes were observed after each fattening period, also indicating sources of contamination from the wider environment outside the farm. Therefore, the results of this study suggest that a potential risk of Campylobacter transmission may originate from present environmental sources (litter and water reservoirs). However, the sources of Campylobacter transmission may vary depending on the operation and farm environmental conditions.

Mapping foodborne pathogen contamination throughout the conventional and alternative poultry supply chains

Recently, there has been a consumer push for natural and organic food products. This has caused alternative poultry production, such as organic, pasture, and free-range systems, to grow in popularity. Due to the stricter rearing practices of alternative poultry production systems, different types of levels of microbiological risks might be present for these systems when compared to conventional production systems. Both conventional and alternative production systems have complex supply chains that present many different opportunities for flocks of birds or poultry meat to be contaminated with foodborne pathogens. As such, it is important to understand the risks involved during each step of production. The purpose of this review is to detail the potential routes of foodborne pathogen transmission throughout the conventional and alternative supply chains, with a special emphasis on the differences in risk between the two management systems, and to identify gaps in knowledge that could assist, if addressed, in poultry risk-based decision making.

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

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

Intrinsic and Extrinsic Aspects on Campylobacter jejuni Biofilms

Biofilm represents a way of life that allows greater survival of microorganisms in hostile habitats. Campylobacter jejuni is able to form biofilms in vitro and on surfaces at several points in the poultry production chain. Genetic determinants related to their formation are expressed differently between strains and external conditions are decisive in this respect. Our approach combines phylogenetic analysis and the presence of seven specific genes linked to biofilm formation in association with traditional microbiology techniques, using Mueller Hinton and chicken juice as substrates in order to quantify, classify, determine the composition and morphology of the biomass of simple and mixed biofilms of 30 C. jejuni strains. It also evaluates the inhibition of its formation by biocides commonly used in industry and also by zinc oxide nanoparticles. Genetic analysis showed high heterogeneity with the identification of 23 pulsotypes. Despite the diversity, the presence of flaA, cadF, luxS, dnaJ, htrA, cbrA, and sodB genes in all strains shows the high potential for biofilm formation. This ability was only expressed in chicken juice, where they presented phenotype of a strong biofilm producer, with a mean count of 7.37 log CFU/mL and an ultrastructure characteristic of mature biofilm. The composition of simple and mixed biofilms was predominantly composed by proteins. The exceptions were found in mixed biofilms with Pseudomonas aeruginosa, which includes a carbohydrate-rich matrix, lower ability to sessile form in chicken juice and compact architecture of the biofilm, this aspects are intrinsic to this species. Hypochlorite, chlorhexidine, and peracetic acid were more effective in controlling viable cells of C. jejuni in biofilm, but the existence of tolerant strains indicates exposure to sublethal concentrations and development of adaptation mechanisms. This study shows that in chicken juice C. jejuni presents greater potential in producing mature biofilms.

Reducing Foodborne Pathogen Persistence and Transmission in Animal Production Environments: Challenges and Opportunities

Preharvest strategies to reduce zoonotic pathogens in food animals are important components of the farm-to-table food safety continuum. The problem is complex; there are multiple pathogens of concern, multiple animal species under different production and management systems, and a variety of sources of pathogens, including other livestock and domestic animals, wild animals and birds, insects, water, and feed. Preharvest food safety research has identified a number of intervention strategies, including probiotics, direct-fed microbials, competitive exclusion cultures, vaccines, and bacteriophages, in addition to factors that can impact pathogens on-farm, such as seasonality, production systems, diet, and dietary additives. Moreover, this work has revealed both challenges and opportunities for reducing pathogens in food animals. Animals that shed high levels of pathogens and predominant pathogen strains that exhibit long-term persistence appear to play significant roles in maintaining the prevalence of pathogens in animals and their production environment. Continued investigation and advancements in sequencing and other technologies are expected to reveal the mechanisms that result in super-shedding and persistence, in addition to increasing the prospects for selection of pathogen-resistant food animals and understanding of the microbial ecology of the gastrointestinal tract with regard to zoonotic pathogen colonization. It is likely that this continued research will reveal other challenges, which may further indicate potential targets or critical control points for pathogen reduction in livestock. Additional benefits of the preharvest reduction of pathogens in food animals are the reduction of produce, water, and environmental contamination, and thereby lower risk for human illnesses linked to these sources.

Campylobacter in Poultry: Ecology and Potential Interventions

Avian hosts constitute a natural reservoir for thermophilic Campylobacter species, primarily Campylobacter jejuni and Campylobacter coli, and poultry flocks are frequently colonized in the intestinal tract with high numbers of the organisms. Prevalence rates in poultry, especially in slaughter-age broiler flocks, could reach as high as 100% on some farms. Despite the extensive colonization, Campylobacter is essentially a commensal in birds, although limited evidence has implicated the organism as a poultry pathogen. Although Campylobacter is insignificant for poultry health, it is a leading cause of food-borne gastroenteritis in humans worldwide, and contaminated poultry meat is recognized as the main source for human exposure. Therefore, considerable research efforts have been devoted to the development of interventions to diminish Campylobacter contamination in poultry, with the intention to reduce the burden of food-borne illnesses. During the past decade, significant advance has been made in understanding Campylobacter in poultry. This review summarizes the current knowledge with an emphasis on ecology, antibiotic resistance, and potential pre- and postharvest interventions.

Application of pulsed field gel electrophoresis to type Campylobacter jejuni

Pulsed field gel electrophoresis (PFGE) is generally accepted as one of the most discriminatory methods available for genotyping Campylobacter jejuni. PFGE has been extensively used in epidemiological studies, including outbreak investigation, persistence of genotypes in a human population, environmental diversity of sporadic infection isolates, dissemination of antibiotic-resistant strains, and comparison of genotypes within and between hosts. The main purpose of this chapter is to present a working PFGE protocol for those interested in incorporating this technique in their laboratories.

Comparative genotypic and antimicrobial susceptibility analysis of zoonotic Campylobacter species isolated from broilers in a nationwide survey, Portugal

Campylobacter is a major cause of human foodborne disease worldwide and has been associated with the consumption of contaminated poultry. The prevalence of Campylobacter species in broiler flocks from more than 200 producers widespread in mainland Portugal was assessed in 2008 in response to Commission Decision 2007/516/EC. Campylobacter isolates were obtained from 83.3% of 424 pooled cecal samples, with a higher prevalence of Campylobacter coli (61.2%) than Campylobacter jejuni (38.8%). Restriction fragment length polymorphism analysis of the flaA gene (flaA-RFLP) of 112 C. coli isolates and 67 C. jejuni isolates yielded 11 flaA-RFLP patterns with HinfI (Hunter Gaston diversity index [HGDI] = 0.62) and 48 flaA-RFLP patterns with DdeI (HGDI = 0.89), indicating a high level of genetic diversity. A wide geographic distribution of the most frequent restriction pattern was observed. MICs of five antimicrobials (ciprofloxacin, gentamicin, streptomycin, erythromycin, and tetracycline) were determined for 215 C. coli isolates and 136 C. jejuni isolates. The occurrence of non-wild-type isolates, exhibiting an acquired resistance phenotype, was higher for C. coli than C. jejuni for all antimicrobials tested. Sixty-three percent of C. jejuni and C. coli isolates were considered non-wild type based on their response to both ciprofloxacin and erythromycin, which are frequently used in the treatment of human infections. The high prevalence of antimicrobial-resistant Campylobacter strains detected supports the need for increased epidemiological surveillance and prevention in a country where large amounts of poultry meat are consumed.

Molecular epidemiology of Campylobacter isolates from poultry production units in southern Ireland

This study aimed to identify the sources and routes of transmission of Campylobacter in intensively reared poultry farms in the Republic of Ireland. Breeder flocks and their corresponding broilers housed in three growing facilities were screened for the presence of Campylobacter species from November 2006 through September 2007. All breeder flocks tested positive for Campylobacter species (with C. jejuni and C. coli being identified). Similarly, all broiler flocks also tested positive for Campylobacter by the end of the rearing period. Faecal and environmental samples were analyzed at regular intervals throughout the rearing period of each broiler flock. Campylobacter was not detected in the disinfected house, or in one-day old broiler chicks. Campylobacter jejuni was isolated from environmental samples including air, water puddles, adjacent broiler flocks and soil. A representative subset of isolates from each farm was selected for further characterization using flaA-SVR sub-typing and multi-locus sequence typing (MLST) to determine if same-species isolates from different sources were indistinguishable or not. Results obtained suggest that no evidence of vertical transmission existed and that adequate cleaning/disinfection of broiler houses contributed to the prevention of carryover and cross-contamination. Nonetheless, the environment appears to be a potential source of Campylobacter. The population structure of Campylobacter isolates from broiler farms in Southern Ireland was diverse and weakly clonal.

Molecular epidemiology and antimicrobial susceptibility of Campylobacter jejuni and Campylobacter coli isolates of poultry, swine, and cattle origin collected from slaughterhouses in Hungary

Campylobacter spp. are the most common cause of bacterial enteritis in Hungary, and the aim of this study was to identify the distribution, genotypes, and antimicrobial susceptibility of Campylobacter species in the most important food-producing animals at the time of slaughter during 2008 and 2009. Of 1,110 samples, 266 were identified as Campylobacter coli (23.9%) and 143 as C. jejuni (12.9%) by real-time PCR. Resistance to enrofloxacin-ciprofloxacin and nalidixic acid was significant, especially in C. jejuni (73.3%) and C. coli (77.2%) from broilers. Higher erythromycin (P = 0.043) and tetracycline (P = 1.865e-14) resistance rates were found among C. coli isolates (9.7 and 74.1%, respectively) than among C. jejuni isolates (3.1 and 36.6%, respectively). A total of 47 fla short variable region sequences were identified among 73 selected C. coli and C. jejuni isolates, with 35 fla types detected only once. At the nucleotide level, fla types A66 and A21 were the most common. Using the pulsed-field gel electrophoresis method, 66% of strains exhibited unique profiles after Sma I digestion. Forty-two isolates assigned to 18 Sma I clusters were further typed by Kpn I, and of these, 24 were assigned to 10 Kpn I clusters. For isolates in five Kpn I clusters, epidemiological links were observed. Stable C. jejuni and C. coli clones were detected, indicating that further studies involving broiler and human isolates need to be conducted to elucidate the importance of these stable clones in human infections.

Drinking water as the source of Campylobacter coli infection in grandparent heavy breeders

The aim of the present study was the molecular identification of a common source of infection of Campylobacter coli in two grandparent breeder farms. Campylobacter jejuni and C. coli were isolated from well water and cloacal swabs from grandparent chickens. Colonies were genotyped using restriction fragment length polymorphism-flaA gene, pulsed field gel electrophoresis and multi-locus sequence typing. The same genotype of C. coli was found in both farms and in the well from which drinking water was supplied to the farms. The well water was epidemiologically linked as the source of C. coli infection. The molecular identification for epidemiological source-tracking of C. coli in breeder farms could aid in combating the colonization of this pathogen and therefore to reduce their incidence in human campylobacteriosis.

Repeated therapeutic dosing selects macrolide-resistant Campylobacter spp. in a turkey facility

AIMS

This study assessed the effects of the therapeutic use of Tylan® in a large-scale turkey production facility on the selection of macrolide-resistant Campylobacter.

METHODS AND RESULTS

A flock of production turkeys (c. 30,000 birds) was followed from brooding to slaughter, and the effects of macrolide application was assessed in one half of the flock from finishing stage to final product and compared against the control barn where no macrolide was used. Overall, Campylobacter prevalence in turkeys was almost 100% by 4 weeks of age. When Campylobacter prevalence was assessed in relation to treatment, high levels of macrolide resistance were evident in this group following treatment, with Campylobacter coli becoming the dominant strain type. Over time, and in the absence of a selection agent, the population of resistant strains decreased suggesting that there was a fitness cost associated with macrolide resistance carriage and persistence. Macrolide resistance was detected in the control barn at a very low level (four isolates recovered during the study), suggesting that the creation or selection of macrolide-resistant Campylobacter was correlated with the treatment regime used. Molecular analysis of a selection of macrolide-resistant Campylobacter recovered was assessed using PCR, RFLP and sequence analysis of the 23S rRNA. The majority of isolates displaying high-level macrolide resistance (>256 μg ml(-1)) possessed an A2075G transition mutation in the 23S rRNA and the CmeABC efflux pump.

CONCLUSIONS

These studies suggest that macrolide resistance can be promoted through the application of treatment during the grow-out phase and once established in a production facility has the potential to persist and be transferred to final product.

SIGNIFICANCE AND IMPACT OF THE STUDY

The study highlights the prudent use of antimicrobials in treatment of disease in poultry. Of significance is the presence of macrolide-resistant Campylobacter in poultry production and finished product as a consequence of macrolide usage.

Clonal population structure and antimicrobial resistance of Campylobacter jejuni in chicken meat from Belgium

Campylobacter jejuni is one of the most important causes of human diarrhea worldwide. In the present work, multilocus sequence typing was used to study the genotypic diversity of 145 C. jejuni isolates from 135 chicken meat preparations sampled across Belgium. Isolates were further typed by pulsed-field gel electrophoresis, and their susceptibilities to six antimicrobials were determined. Fifty-seven sequence types (STs) were identified; 26.8% of the total typed isolates were ST-50, ST-45, or ST-257, belonging to clonal complex CC-21, CC-45, or CC-257, respectively. One clonal group comprised 22% (32/145) of all isolates, originating from five different companies and isolated over seven sampling months. Additionally, 53.1% of C. jejuni isolates were resistant to ciprofloxacin, and 48.2% were resistant to tetracycline; 28.9% (42/145) of all isolates were resistant to both ciprofloxacin and tetracycline. The correlation between certain C. jejuni clonal groups and resistance to ciprofloxacin and tetracycline was notable. C. jejuni isolates assigned to CC-21 (n = 35) were frequently resistant to ciprofloxacin (65.7%) and tetracycline (40%); however, 90% (18/20) of the isolates assigned to CC-45 were pansusceptible. The present study demonstrates that certain C. jejuni genotypes recur frequently in the chicken meat supply. The results of molecular typing, combined with data on sample sources, indicate a possible dissemination of C. jejuni clones with high resistance to ciprofloxacin and/or tetracycline. Whether certain clonal groups are common in the environment and repeatedly infect Belgian broiler flocks or whether they have the potential to persist on farms or in slaughterhouses needs further investigation.

Evidence of cross-contamination by Campylobacter spp. of broiler carcasses using genetic characterization of isolates

Campylobacter is recognized as one of the leading cause of gastroenteritis worldwide, and is frequently isolated from the small intestines and ceca microflora of chickens. Twenty-one out of 81 Campylobacter-positive poultry flocks were selected to evaluate the genetic diversity of Campylobacter isolates and to study the distribution of genotypes among flocks. Campylobacter isolates recovered from chicken carcasses and ceca were analyzed by pulsed-field gel electrophoresis (PFGE). Little diversity was found among Campylobacter strains isolated from a given carcass, with a maximum of 2 different genotypes being present. However, at flock level, as many as 4 different profiles were observed. Typing of strains showed that most strains isolated from ceca were similar to those isolated from corresponding broiler carcasses. A total of 39 different macrorestriction profiles were observed, with evidence of Campylobacter cross-contamination among broiler flocks in Quebec slaughterhouses. Surprisingly, some flocks shared related genotypes both with and without sharing similar rearing practices. Existence of such cross-contamination must be considered to in developing strategies to control Campylobacter in chickens, and to avoid bacteria contamination of noncolonized flocks. Further typing studies of Campylobacter found in hatcheries, farm environment, and crates or trucks in Quebec might be helpful in elucidating the kinetics of broiler chicken Campylobacter contamination.

Campylobacter infection of broiler chickens in a free-range environment

Campylobacter jejuni is the most common cause of bacterial gastroenteritis worldwide, with contaminated chicken meat considered to represent a major source of human infection. Biosecurity measures can reduce C. jejuni shedding rates of housed chickens, but the increasing popularity of free-range and organic meat raises the question of whether the welfare benefits of extensive production are compatible with food safety. The widespread assumption that the free-range environment contaminates extensively reared chickens has not been rigorously tested. A year-long survey of 64 free-range broiler flocks reared on two sites in Oxfordshire, UK, combining high-resolution genotyping with behavioural and environmental observations revealed: (i) no evidence of colonization of succeeding flocks by the C. jejuni genotypes shed by preceding flocks, (ii) a high degree of similarity between C. jejuni genotypes from both farm sites, (iii) no association of ranging behaviour with likelihood of Campylobacter shedding, and (iv) higher genetic differentiation between C. jejuni populations from chickens and wild birds on the same farm than between the chicken samples, human disease isolates from the same region and national samples of C. jejuni from chicken meat.

Has retail chicken played a role in the decline of human campylobacteriosis?

Between 2001 and 2006, the incidence of human Campylobacter infections decreased by 10 and 27% in Scotland and the Grampian region of Scotland, respectively. Contemporaneous collection and analyses of human and retail-chicken isolates from Grampian were carried out over a 10-week period in 2001 and again in 2006 in order to determine whether the fall in the incidence of human infections was related to the retail-chicken exposure route. Rates of carriage of Campylobacter on chicken carcasses from retail outlets in Grampian in 2001 and 2006 were estimated. Chicken-derived Campylobacter isolates from 2001 (n = 84) and 2006 (n = 105) and human-derived isolates from patients with clinical cases of infection in 2001 (n = 172) and 2006 (n = 119) were typed by multilocus sequence typing. We found no evidence for statistically significant changes in prevalence and counts per carcass. We found by rarefaction that although the degree of diversity in humans tended to be higher than that in chickens, these differences were not significant. The genetic distance between chicken and human isolates from 2001 according to sequence type, clonal complex (CC), or allele composition was not significant, whereas the distances between 2006 isolates at the CC and allele levels were significant. This difference was attributable to a lower proportion of CC-21's being found in retail-chicken isolates from 2006 than in chicken isolates from 2001. We conclude that human exposure to Campylobacter via retail chicken is important and that changes in the population structure of campylobacters in this reservoir need to be taken into account in investigating human infection.

House-level risk factors associated with the colonization of broiler flocks with Campylobacter spp. in Iceland, 2001 - 2004

BACKGROUND

The concurrent rise in consumption of fresh chicken meat and human campylobacteriosis in the late 1990's in Iceland led to a longitudinal study of the poultry industry to identify the means to decrease the frequency of broiler flock colonization with Campylobacter. Because horizontal transmission from the environment is thought to be the most likely source of Campylobacter to broilers, we aimed to identify broiler house characteristics and management practices associated with flock colonization. Between May 2001 and September 2004, pooled caecal samples were obtained from 1,425 flocks at slaughter and cultured for Campylobacter. Due to the strong seasonal variation in flock prevalence, analyses were restricted to a subset of 792 flocks raised during the four summer seasons. Logistic regression models with a farm random effect were used to analyse the association between flock Campylobacter status and house-level risk factors. A two-stage process was carried out. Variables were initially screened within major subsets: ventilation; roof and floor drainage; building quality, materials and repair; house structure; pest proofing; biosecurity; sanitation; and house size. Variables with p < or = 0.15 were then offered to a comprehensive model. Multivariable analyses were used in both the screening stage (i.e. within each subset) and in the comprehensive model.

RESULTS

217 out of 792 flocks (27.4%) tested positive. Four significant risk factors were identified. Campylobacter colonization was predicted to increase when the flock was raised in a house with vertical (OR = 2.7), or vertical and horizontal (OR = 3.2) ventilation shafts, when the producer's boots were cleaned and disinfected prior to entering the broiler house (OR = 2.2), and when the house was cleaned with geothermal water (OR = 3.3).

CONCLUSION

The increased risk associated with vertical ventilation shafts might be related to the height of the vents and the potential for vectors such as flies to gain access to the house, or, increased difficulty in accessing the vents for proper cleaning and disinfection. For newly constructed houses, horizontal ventilation systems could be considered. Boot dipping procedures should be examined on farms experiencing a high prevalence of Campylobacter. Although it remains unclear how geothermal water increases risk, further research is warranted to determine if it is a surrogate for environmental pressures or the microclimate of the farm and surrounding region.

Prevalence and risk factors for Salmonella spp. and Campylobacter spp. caecal colonization in broiler chicken and turkey flocks slaughtered in Quebec, Canada

We conducted an observational study to estimate prevalence and risk factors for Salmonella spp. and Campylobacter spp. caecal colonization in poultry. Eighty-one broiler chicken and 59 turkey flocks selected among flocks slaughtered in the province of Quebec, Canada, were included in the study. Flock status was evaluated by culturing pooled caecal contents from about 30 birds per flock. Exposure to potential risk factors was evaluated with a questionnaire. Odds ratios were computed using multivariable logistic regression. The prevalence of Salmonella-positive flocks was 50% (95% CI: 37, 64) for chickens and 54% (95% CI: 39, 70) for turkeys, respectively. Odds of Salmonella colonization were 2.6 times greater for chicken flocks which failed to lock the chicken house permanently. In turkeys, odds of Salmonella colonization were 4.8-7.7 times greater for flocks which failed to be raised by <or=2 producers with no other visitors allowed onto the premises, or origin from a hatchery. The prevalence of Campylobacter-positive flocks was 35% (95% CI: 22, 49) for chickens and 46% (95% CI: 30, 62) for turkeys. Odds of colonization were 4.1 times higher for chicken flocks raised on farms with professional rodent control and 5.2 times higher for flocks with manure heap >200m from the poultry house, and also increased with the number of birds raised per year on the farm and with the age at slaughter. For turkeys, odds of Campylobacter flock colonization were 3.2 times greater in flocks having a manure heap at </=200m from poultry house and 4.2 times greater in flocks drinking unchlorinated water.

The persistence of fluoroquinolone-resistant Campylobacter in poultry production

BACKGROUND

The use of antibiotics in food animal production has been associated with antibiotic-resistant infections in humans. In 2005, the Food and Drug Administration (FDA) banned fluoroquinolone use in U.S. poultry production in order to reduce the prevalence of fluoroquinolone-resistant Campylobacter. Little is known about the potential efficacy of this policy.

OBJECTIVES

Our primary objective was to follow temporal changes in the prevalence of fluoroquinolone-resistant Campylobacter among poultry products from two conventional producers who announced their cessation of fluoroquinolone use in 2002 (3 years before the FDA's ban). Our secondary objective was to compare, over time, the prevalence of fluoroquinolone-resistant Campylobacter in conventional poultry products to those from producers who claim to use no antibiotics.

METHODS

We collected poultry samples from two conventional producers and three antibiotic-free producers over the course of 20 weeks in 2004 (n = 198) and 15 weeks in 2006 (n = 210). We compared the rates of fluoroquinolone resistance among Campylobacter isolates from the different producers.

RESULTS

We found no significant change in the proportion of fluoroquinolone-resistant Campylobacter isolates from the two conventional producers over the study period. In addition, Campylobacter strains from the two conventional producers were significantly more likely to be fluoroquinolone resistant than those from the antibiotic-free producers.

CONCLUSIONS

The results from this study indicate that fluoroquinolone-resistant Campylobacter may be persistent contaminants of poultry products even after on-farm fluoroquinolone use has ceased. The FDA's ban on fluoroquinolones in poultry production may be insufficient to reduce resistant Campylobacter in poultry products.

Campylobacter in Finnish Organic Laying Hens in Autumn 2003 and Spring 2004

A total of 642 fecal samples and 360 table eggs from Finnish organic laying hens were collected in autumn 2003 (19 farms) and spring 2004 (17 farms) and studied for the presence of Campylobacter. In autumn, 84% of the farms were positive for Campylobacter and in spring, 76%. The percentage of positive samples within a flock varied between 5 and 100%. In addition, Campylobacter was isolated in a single eggshell sample. Campylobacter jejuni was the species isolated most often, although Campylobacter coli was detected on 3 farms in autumn and on 4 farms in spring. KpnI pulsed-field gel electrophoresis genotyping revealed a high level of diversity among the isolates; 47 different patterns were detected among a total of 162 isolates studied. On most of the farms, the genotypes identified in autumn and spring were different, also indicating temporal diversity among colonizing isolates. However, some predominant persistent genotypes were also detected among the isolates. These results suggest that the pool of colonizing isolates may include both variants with capability for persistent intestinal colonization in hens as well as variants with short-term colonization characteristics. In antimicrobial susceptibility testing, the majority of isolates were susceptible to ciprofloxacin, tetracycline, ampicillin, and nalidixic acid. On 2 farms, isolates resistant to nalidixic acid and to ciprofloxacin were detected. In conclusion, Finnish organic laying hens are often colonized by a diversity of Campylobacter pulsed-field gel electrophoresis genotypes.

Quantification of thermophilic Campylobacter spp. in broilers during meat processing

Campylobacter spp. is a common cause of gastrointestinal illness. Since animal products, especially poultry meat, are an important source of human outbreaks of campylobacteriosis, tracing back to processing and initial production is of great interest. Samples were collected at a German poultry slaughterhouse for the estimation of the prevalence of Campylobacter at different processing steps. Quantification of Campylobacter in each of the samples was also performed. Out of 99 samples examined, 51 (51.5%) were positive for Campylobacter, with bacterial counts ranging from log(10) 6.5 cfu sample(-1) for carcasses to log 3.6 cfu ml(-1) for scalding water. The Campylobacter isolates (n = 51) were subtyped by pulsed-field gel electrophoresis using SmaI and KpnI restriction enzymes. Molecular typing showed a multitude of strains with different molecular patterns. Strains found in cloacal swabs before processing could also be isolated from carcasses at different processing steps.

A longitudinal study of Salmonella and Campylobacter jejuni isolates from day of hatch through processing by automated ribotyping

Comparisons of bacterial populations over long periods of time allow researchers to identify clonal populations, perhaps those responsible for contamination of farms or humans. Salmonella and Campylobacter can cause human illness, and our objective was to use a library typing system to track strains that persist in the poultry house and through the processing plant. Two farms, over four consecutive flocks, were studied. Multiple samples were taken of the poultry house environment, feed mill, transport crates, and carcasses in the processing plant. Sample collection on the farm took place on chick placement day, midgrowout, and the day of harvest. This study found that 80.3% of isolates belonged to a single strain of Salmonella Kentucky that persisted in several environmental samples for all flocks at both farms, from chick placement day to the final product at the plant. Surgical shoe covers produced most isolates (n = 26), and processing day yielded the highest recovery (n = 68). Additional serotypes were recovered, but the Salmonella Kentucky-positive eggshells and chick mortality appeared to be the source of the organism for both farms. All Campylobacter isolates recovered were identified as C. jejuni. Most Campylobacter isolates (90.1%) belonged to one of three core strains. C. jejuni was not recovered on chick placement day. Cecal droppings yielded all nine strains. Most isolates (98.2%) were from one farm. Cluster analysis grouped C. jejuni and Salmonella isolates into four and six distinct clusters, respectively, on the basis of a similarity level of 80%.

Genetic characterization and antibiotic resistance of Campylobacter spp. isolated from poultry and humans in Senegal

AIMS

The main objectives of this study were to investigate the diversity of Campylobacter genotypes circulating in Senegal and to determine the frequency of antibiotic resistance.

METHODS AND RESULTS

Strains of Campylobacter jejuni isolated from poultry (n = 99) and from patients (n = 10) and Campylobacter coli isolated from poultry (n = 72) were subtyped by pulsed-field gel electrophoresis (PFGE). The pulsotypes obtained after digestion by SmaI and KpnI revealed a significant genetic diversity in both species, but without any predominant pulsotypes. However, farm-specific clones were identified in the majority of poultry houses (76.5%). Human and poultry isolates of C. jejuni had common PFGE patterns. High quinolone-resistance rates were observed for C. jejuni (43.4%) and C. coli (48.6%) isolates obtained from poultry.

CONCLUSIONS

The results showed a genetic diversity of Campylobacter between farms indicating multiple sources of infection; but specific clones had the ability to colonize the broiler farms. The antimicrobial resistance patterns were not related to any specific PFGE pattern suggesting that resistance was due to the selective pressure of antibiotic usage. Campylobacter with similar genotypes were circulating in both human and poultry.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study is important for the understanding of the epidemiology of Campylobacter in broiler farms in Senegal. It also emphasizes the need for a more stringent policy in the use of antimicrobial agents in food animals.

Risk factors for Campylobacter spp. colonization in broiler flocks in Iceland

We sampled 1,091 Icelandic broiler flocks at slaughter from May 2001 to December 2003 to determine the prevalence of, and investigate risk factors for the presence of, Campylobacter spp. at the flock level. Approximately 15% of the flocks were positive for Campylobacter spp.; most (95%) of the infected flocks being raised during the months of April-September. Based on the data from the latter months, and using multivariable logistic regression with random effects for herd, we found that the odds of a flock being positive for Campylobacter spp. increased with age and flock size. Additionally, vertical ventilation systems were strongly associated with positive flocks (OR=5.3). After controlling for these variables, we found no evidence of an effect of: year; company; Campylobacter being carried over from one flock to the next; time interval between flocks; using (at the hatcheries) eggs laid on the floor; density of bird housing, or the number of catch lots a flock was divided into for slaughtering purposes on the risk of a Campylobacter-positive flock.

Genetic diversity of Arcobacter and Campylobacter on broiler carcasses during processing

Broiler carcasses (n=325) were sampled at three sites along the processing line (prescalding, prechilling, and postchilling) in a commercial poultry processing plant during five plant visits from August to October 2004. Pulsed-field gel electrophoresis (PFGE) was used to determine the genomic fingerprints of Camospylobacter coli (n=27), Campylobacter jejuni (n=188), Arcobacter butzleri (n=138), Arcobacter cryaerophilus 1A (n=4), and A. cryaerophilus 1B (n=31) with the restriction enzymes SmaI and KpnI for Campylobacter and Arcobacter, respectively. Campylobacter species were subtyped by the Centers for Disease Control and Prevention PulseNet 24-h standardized protocol for C. jejuni. A modification of this protocol with a different restriction endonuclease (KpnI) and different electrophoresis running conditions produced the best separation of restriction fragment patterns for Arcobacter species. Both unique and common PFGE types of Arcobacter and Campylobacter strains were identified. A total of 32.8% (57 of 174) of the Arcobacter isolates had unique PFGE profiles, whereas only 2.3% (5 of 215) of the Campylobacter isolates belonged to this category. The remaining Arcobacter strains were distributed among 25 common PFGE types; only eight common Campylobacter PFGE types were observed. Cluster analysis showed no associations among the common PFGE types for either genus. Each of the eight common Campylobacter types consisted entirely of isolates from one sampling day, whereas more than half of the common Arcobacter types contained isolates from different sampling days. Our results demonstrate far greater genetic diversity for Arcobacter than for Campylobacter and suggest that the Campylobacter types are specific to individual flocks of birds processed on each sampling day.

Dynamics of Campylobacter spp. spread investigated in 14 broiler flocks in Switzerland

Ten conventional and four extensive outdoor broiler flocks, distributed over nine farms, were investigated twice per week during a 35-58-day rearing period to observe the dynamics of Campylobacter spp. spread within these flocks. Strains isolated during this period were genotyped by restriction fragment length polymorphism analysis of the flaA gene and macrorestriction profiling with pulsed field gel electrophoresis. A total of 4112 samples were collected; 157 (3.8%) of these samples were Campylobacter positive, with all C. jejuni. The positive samples were distributed over three conventional and two extensive outdoor flocks on five farms. These five positive flocks were colonized from the fifth to the seventh week of age and remained colonized until slaughter. Each of the flocks showed a flock-specific genotype of Campylobacter that predominated until slaughter. Presuming different ways of entry, a combination of this fact and the observed dynamics of C. jejuni spread within the flocks indicates that a single source from the environment may have been responsible for the colonization of each flock. These conclusions may serve to further develop combat strategies at farm level.

Campylobacter contamination during poultry slaughter in Belgium

The relation between internal carriage and surface contamination with thermophilic Campylobacter species in broilers was examined by molecular typing methods. Samples from 39 flocks were collected in three Belgian poultry slaughterhouses. From each flock, crop swabs before slaughter and intestines and neck skins during slaughter were collected. A total of 309 isolates were identified at species level and further characterized by flagellin gene A PCR/restriction fragment length polymorphism and pulsed-field gel electrophoresis. Isolates were identified as Campylobacter jejuni (90%), Campylobacter coli (8.7%), and Campylobacter lari (2.2%), and 27 genotypes could be distinguished by combining the two molecular methods. Seventy-two percent of the flocks arriving at the abattoir were colonized with campylobacters. After slaughter, 79% of the flocks had contaminated neck skins. In six flocks, genotypes isolated from the neck skins were also found in the alimentary tract from previously slaughtered flocks. Four of these flocks were initially free of Campylobacter. These four flocks might have had no contaminated carcasses after logistic slaughtering.

The Dynamics of Antimicrobial-Resistant Campylobacter jejuni on Japanese Broiler Farms

We investigated for dynamics of Campylobacter clones on 2 different managerial broiler farms. Campylobacter isolates were differentiated by resistance typing and molecular typing methods. On farm I, the same C. jejuni clones resistant to fluoroquinolone and oxytetracycline were isolated after one and half years again and another susceptible clone was invaded. The susceptible clone was isolated again after half year. Broiler flocks on the farm may be repeatedly infected with a few C. jejuni clones. On farm II, new clones including antimicrobial resistant one, were often invaded. The change of predominant C. jejuni clone in each flock on both the farms was observed, in the absence of antimicrobial selective pressure.

Sources of Campylobacter spp. colonizing housed broiler flocks during rearing

The study aimed to identify sources of campylobacter in 10 housed broiler flocks from three United Kingdom poultry companies. Samples from (i) the breeder flocks, which supplied the broilers, (ii) cleaned and disinfected houses prior to chick placement, (iii) the chickens, and (iv) the environments inside and outside the broiler houses during rearing were examined. Samples were collected at frequent intervals and examined for Campylobacter spp. Characterization of the isolates using multilocus sequence typing (MLST), serotyping, phage typing, and flaA restriction fragment length polymorphism typing was performed. Seven flocks became colonized during the growing period. Campylobacter spp. were detected in the environment surrounding the broiler house, prior to as well as during flock colonization, for six of these flocks. On two occasions, isolates detected in a puddle just prior to the birds being placed were indistinguishable from those colonizing the birds. Once flocks were colonized, indistinguishable strains of campylobacter were found in the feed and water and in the air of the broiler house. Campylobacter spp. were also detected in the air up to 30 m downstream of the broiler house, which raises the issue of the role of airborne transmission in the spread of campylobacter. At any time during rearing, broiler flocks were colonized by only one or two types determined by MLST but these changed, with some strains superseding others. In conclusion, the study provided strong evidence for the environment as a source of campylobacters colonizing housed broiler flocks. It also demonstrated colonization by successive campylobacter types determined by MLST during the life of a flock.

Fluoroquinolone-resistant Campylobacter isolates from conventional and antibiotic-free chicken products

The use of fluoroquinolones (FQs) in poultry production is an important issue in public health today. In February 2002, two prominent U.S. poultry companies pledged to stop using FQs for flock-wide treatment. One year later, we began a survey of Campylobacter isolates on chicken products from these two companies and from two producers claiming total abstention from antibiotic use. Using both standard isolation methods and new methods modified to enhance detection of FQ-resistant Campylobacter, we compared rates of FQ-resistant Campylobacter among these products. Four major findings were drawn from this study: a) antibiotic-free brands were not more likely to be contaminated with Campylobacter; b) a high percentage of products from the two conventional brands were contaminated with FQ-resistant Campylobacter (43 and 96%); c) these conventional brands had significantly higher odds of carrying resistant strains compared with antibiotic-free products; and d) supplementing media with FQs increased the sensitivity of detecting FQ-resistant strains among mixed populations of Campylobacter, thus reducing a bias toward underestimating the prevalence of FQ-resistant Campylobacter on samples. These results suggest that FQ resistance may persist in the commercial poultry environment in the absence of FQ-selective pressure and that these strains contaminate a larger proportion of foods than reported previously.

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

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

Genetic characterization and antibiotic resistance of Campylobacter jejuni isolated from meats, water, and humans in Sweden

The incidence of Campylobacter jejuni has increased during the last decade, and today it is the leading cause of bacterial enteritis in most developed countries. Still, there is a lack of knowledge about infection routes and to what extent identified sources are responsible for spreading the bacterium to humans. The major objective of this work was to explore the genetic similarity between C. jejuni isolated from different sources. C. jejuni isolated from patients (n = 95), five types of meat (n = 71), and raw water (n = 11) during the year 2000 were subtyped by pulsed-field gel electrophoresis (PFGE). The pulsotypes obtained after digestion with SmaI revealed not only that C. jejuni is genetically diverse but also that specific pulsotypes occur frequently. Five clusters comprising 88 of the 162 SmaI-digested isolates were obtained. After digestion with KpnI most isolates in four of the five clusters were still indistinguishable, while the fifth cluster was strongly dissolved. The clusters comprised high frequencies of human and meat isolates, while only one of nine water isolates belonged to a cluster. The largest cluster comprised 21 human isolates, one raw water isolate, and seven chicken meat isolates, originating from at least six different broiler flocks. Low frequencies of antibiotic resistance were revealed when the meat and water isolates were tested for sensitivity to six antibiotics. Interestingly, the five isolates resistant to quinolones displayed similar or identical pulsotypes. The results showed that PFGE has proved useful in identifying clones and will be used in future work focusing on identification and eradication of the major reservoirs for common clones.