Study of the infectivity of saline-stored Campylobacter jejuni for day-old chicks

Effects of DNA extraction methods on the real time PCR quantification of Campylobacter jejuni, Campylobacter coli, and Campylobacter lari in chicken feces and ceca contents

Polymerase chain reaction (PCR) method was coupled with a DNA extraction to enumerate Campylobacter spp. from poultry gastrointestinal tract samples. Three experiments were conducted that included: 1) Development of a DNA standard curve related to bacterial DNA primers; 2) Design of a cell/genomic DNA extraction protocol to isolate Campylobacter spp. DNA from complex samples such as poultry feces; and 3) Comparison of PCR quantification to standard plate count methodology. The standard curve using primers for Campylobacter spp. was created for DNA extracted from environmental isolates with a linear range (R² > 0.95) and with a high specificity for C. coli and C. jejuni recovered from poultry, swine and laboratory isolates. A 2-step extraction process of bacterial DNA from poultry feces was developed in which the cells were first concentrated using a gradient-centrifugation step followed by comparison of 4 DNA extraction methods. Two commercial DNA extraction methods (Zymo Research Quick DNA, and Invitrogen magnetic separation), a traditional phenol-chloroform DNA extraction method using proteinase K to inactivate DNAses, and an in-house isolation method for DNA extraction based on chaotropic salts were used. The middle gradient layer recovered 89% to 98% of the bacteria cells from the sample, with recovery dependent upon the Campylobacter genus. The 4 DNA extractions methods recovered 112 to 302 ug/nL of DNA. Finally, the qPCR and standard plate methods were highly correlated for enumerating Campylobacter spp. in the 2.0 to 8.0-log CFU range. Analyses of the results from this study demonstrate that the combination of the standard curve for Campylobacter spp. DNA primers, the gradient cell concentration method and DNA extraction techniques with qPCR can be used to enumerate Campylobacter spp. from poultry samples with findings similar those of traditional plate count methodology.

Genotyping, virulence genes and antimicrobial resistance of Campylobacter spp.isolated during two seasonal periods in Spanish poultry farms

Campylobacter spp. are the leading causes of bacterial human gastroenteritis worldwide; being poultry farms the main source of infections. In order to obtain information on prevalence and diversity of Campylobacter-infected flocks in the North of Spain, fourteen farms were studied between autumn and spring in 2014 and 2015, respectively. Moreover, virulence genes involved in pathogenicity and antimicrobial resistance were investigated. A survey about preventive hygiene practices at farms was performed to determine the risky practices that could contribute to the presence of Campylobacter in this step of the poultry food chain. Testing the presence of Campylobacter spp. showed 43 % of the farms were positive during autumn, whereas only 31 % were positive in spring. A very high prevalence within-flock was observed (43.1 % to 88.6 %) and C. jejuni was the most prevalent species in both periods. Genotyping by pulsed field gel electrophoresis (PFGE) showed a high heterogeneity among farms (309 isolates clustered into 21 pulsotypes). Virulence genes were present in all C. jejuni isolates while cdtA and cdtC were absent in C. coli. On the contrary, the latter showed higher antimicrobial resistance than C. jejuni. This study suggests that environment might be one of the main sources for Campylobacter transmission, as water supply seemed to be a clear cause of the contamination in a specific farm. However, in other farms other environmental factors contributed to the contamination, confirming the multifactorial origin of Campylobacter colonization in broilers. Therefore, biosecurity measures in farms are crucial to reduce Campylobacter contamination, which may have important implications for human and animal health.

Observe Before You Leap: Why Observation Provides Critical Insights for Formative Research and Intervention Design That You'll Never Get From Focus Groups, Interviews, or KAP Surveys

Four case studies show how observation can uncover issues critical to making a health intervention succeed or, sometimes, reveal reasons why it is likely to fail. Observation can be particularly valuable for interventions that depend on mechanical or clinical skills; service delivery processes; effects of the built environment; and habitual tasks that practitioners find difficult to articulate.

Formative research is essential to designing both study instruments and interventions in global health. While formative research may employ many qualitative methods, focus group discussions and in-depth interviews are the most common. Observation is less common but can generate insights unlikely to emerge from any other method. This article presents 4 case studies in which observation revealed critical insights: corralling domestic poultry to reduce childhood diarrhea, promoting insecticide-treated bed nets (ITNs) to prevent malaria, evaluating skilled birth attendant competency to manage life-threatening obstetric and neonatal complications, and assessing community health worker (CHW) ability to use malaria rapid diagnostic tests (RDTs). Observation of Zambian CHWs to design malaria RDT training materials revealed a need for training on how to take finger-stick blood samples, a procedure second nature to many health workers but one that few CHWs had ever performed. In Lima, Peru, study participants reported keeping their birds corralled “all the time,” but observers frequently found them loose, a difference potentially explained by an alternative interpretation of the phrase “all the time” to mean “all the time (except at some specific seemingly obvious times).” In the Peruvian Amazon, observation revealed a potential limitation of bed net efficacy due to the built environment: In houses constructed on stilts, many people sleep directly on the floor, allowing mosquitoes to bite from below through gaps in the floorboards. Observation forms and checklists from each case study are included as supplemental files; these may serve as models for designing new observation guides. The case studies illustrate the value of observation to clearly understanding clinical practices and skills, details about how people carry out certain tasks, routine behaviors people would most likely not think to describe in an interview, and environmental barriers that must be overcome if an intervention is to succeed. Observation provides a way to triangulate for social desirability bias and to measure details that interview or focus group participants are unlikely to recognize, remember, or be able to describe with precision.

Prevalence, genotyping and risk factors of thermophilic Campylobacter spreading in organic turkey farms in Germany

BACKGROUND

The need for organic food of animal origin has increased rapidly in recent years. However, effects of organic animal husbandry on food safety have not been rigorously tested especially in meat turkey flocks. This study provides for the first time an overview on the prevalence and genetic diversity of Campylobacter species (spp.) in five organic meat turkey farms located in different regions in Germany, as well as on potential risk factors of bacterial spreading. Thirty cloacal swabs as well as water samples and darkling beetles were collected from each flock and examined for the presence of Campylobacter by conventional and molecular biological methods. The isolates were genotyped by flaA-RFLP.

RESULTS

Campylobacter spp. were detected in cloacal swabs in all 5 turkey flocks with prevalence ranged from 90.0 to 100 %. 13 cloacal swabs collected from birds in farm III and IV were harboured mixed population of thermophilic campylobacters. In total, from 158 Campylobacter isolated from turkeys 89 (56.33 %) were identified as C. coli and 69 (43.76 %) as C. jejuni. Three Campylobacter (2 C. jejuni and 1 C. coli) were detected in drinkers of two farms and 3 C. coli were isolated from darkling beetles of one farm. No Campylobacter were isolated from main water tanks. flaA-RFLP assay showed that turkey farms can harbour more than one genotype. In a single turkey two different genotypes could be detected. The genotypes of campylobacters isolated from water samples or beetles were identical with those isolated from turkeys. No effect was found of some environmental parameters [ammonia concentration (NH3), carbon dioxide concentration (CO2), relative humidity (RH) and air temperature)] on Campylobacter prevalence in organic turkey farms. Additionally, drinking water and darkling beetles might be considered as risk factors for the spreading of Campylobacter in turkey flocks.

CONCLUSIONS

This study highlights the high prevalence and genotypic diversity of Campylobacter spp. isolated from organic turkey flocks. Further research is needed to assess other potential risk factors responsible for bacteria spreading in order to mitigate the spread of Campylobacter in organic turkey flocks by improving biosecurity control measures.

Role of environmental survival in transmission of Campylobacter jejuni

Campylobacter species are the most common cause of bacterial gastroenteritis, with C. jejuni responsible for the majority of these cases. Although it is clear that livestock, and particularly poultry, are the most common source, it is likely that the natural environment (soil and water) plays a key role in transmission, either directly to humans or indirectly via farm animals. It has been shown using multilocus sequence typing that some clonal complexes (such as ST-45) are more frequently isolated from environmental sources such as water, suggesting that strains vary in their ability to survive in the environment. Although C. jejuni are fastidious microaerophiles generally unable to grow in atmospheric levels of oxygen, C. jejuni can adapt to survival in the environment, exhibiting aerotolerance and starvation survival. Biofilm formation, the viable but nonculturable state, and interactions with other microorganisms can all contribute to survival outside the host. By exploiting high-throughput technologies such as genome sequencing and RNA Seq, we are well placed to decipher the mechanisms underlying the variations in survival between strains in environments such as soil and water and to better understand the role of environmental persistence in the transmission of C. jejuni directly or indirectly to humans.

Transmission and dose-response experiments for social animals: a reappraisal of the colonization biology of Campylobacter jejuni in chickens

Dose-response experiments characterize the relationship between infectious agents and their hosts. These experiments are routinely used to estimate the minimum effective infectious dose for an infectious agent, which is most commonly characterized by the dose at which 50 per cent of challenged hosts become infected-the ID(50). In turn, the ID(50) is often used to compare between different agents and quantify the effect of treatment regimes. The statistical analysis of dose-response data typically makes the assumption that hosts within a given dose group are independent. For social animals, in particular avian species, hosts are routinely housed together in groups during experimental studies. For experiments with non-infectious agents, this poses no practical or theoretical problems. However, transmission of infectious agents between co-housed animals will modify the observed dose-response relationship with implications for the estimation of the ID(50) and the comparison between different agents and treatments. We derive a simple correction to the likelihood for standard dose-response models that allows us to estimate dose-response and transmission parameters simultaneously. We use this model to show that: transmission between co-housed animals reduces the apparent value of the ID(50) and increases the variability between replicates leading to a distinctive all-or-nothing response; in terms of the total number of animals used, individual housing is always the most efficient experimental design for ascertaining dose-response relationships; estimates of transmission from previously published experimental data for Campylobacter spp. in chickens suggest that considerable transmission occurred, greatly increasing the uncertainty in the estimates of dose-response parameters reported in the literature. Furthermore, we demonstrate that accounting for transmission in the analysis of dose-response data for Campylobacter spp. challenges our current understanding of the differing response of chickens with respect to host-age and in vivo passage of bacteria. Our findings suggest that the age-dependence of transmissibility between hosts-rather than their susceptibility to colonization-is the mechanism behind the 'lag-phase' reported in commercial flocks, which are typically found to be Campylobacter free for the first 14-21 days of life.

Campylobacter in poultry: filling an ecological niche

Epidemiological studies indicate that Campylobacter species may be responsible for the majority of cases of sporadic gastroenteritis in humans. These studies also suggest that poultry may be one of the most common sources of the bacteria for humans. Campylobacter and related genera in the family Campylobacteraceae are oral and intestinal commensals of vertebrates and some nonvertebrates, a characteristic that complicates rational approaches to controlling Campylobacter contamination of poultry. This review will discuss the phylogeny, genomics, and physiology of campylobacters with the intention of revealing how these organisms have evolved to fill their intestinal ecological niche in poultry and how their physiology must be understood in order to enact effective control strategies.

Genotyping of Campylobacter jejuni strains from Danish broiler chickens by restriction fragment length polymorphism of the LPS gene cluster

AIMS

To apply and evaluate LG (LPS genes) genotyping, which is a genotyping method based on a cluster of genes involved in the synthesis of surface lipopolysaccharides (LPS) in Campylobacter species, for typing of Campylobacter jejuni isolates obtained from Danish broiler chickens. Furthermore, the LG genotyping method was used to study the genetic stability of four C. jejuni strains after gastrointestinal passage through experimentally infected chickens.

METHODS AND RESULTS

In the present study, the LG genotyping method was modified with respect to the restriction enzymes used. To validate the method, 63 Penner serotype reference strains and 107 C. jejuni chicken isolates, representing the most common Penner serotypes of C. jejuni in Danish poultry, were selected for typing. The method was successfully used for typing all isolates and the LG genotype profiles were reproducible. There were no changes in the LG genotype of the C. jejuni strains obtained after experimental passage through chickens.

CONCLUSIONS

All C. jejuni strains obtained from broiler chickens were typeable by the LG genotyping method. Application of the RsaI restriction enzyme improved the method in terms of ease and consistency of analyses and increase of discriminatory power.

SIGNIFICANCE AND IMPACT OF THE STUDY

The LG genotyping method is a valuable tool for typing C. jejuni isolates obtained from poultry. However, the association between Penner serotyping based on passive haemagglutination of heat-stable antigens and LG genotyping was low when applied to poultry isolates. This is in contrast to previous studies on isolates of human origin that reported a high correlation between results obtained by the two typing methods (Shi et al. 2002).

Quantification of Campylobacter spp. in chicken rinse samples by using flotation prior to real-time PCR

Real-time PCR is fast, sensitive, specific, and can deliver quantitative data; however, two disadvantages are that this technology is sensitive to inhibition by food and that it does not distinguish between DNA originating from viable, viable nonculturable (VNC), and dead cells. For this reason, real-time PCR has been combined with a novel discontinuous buoyant density gradient method, called flotation, in order to allow detection of only viable and VNC cells of thermotolerant campylobacters in chicken rinse samples. Studying the buoyant densities of different Campylobacter spp. showed that densities changed at different time points during growth; however, all varied between 1.065 and 1.109 g/ml. These data were then used to develop a flotation assay. Results showed that after flotation and real-time PCR, cell concentrations as low as 8.6 x 10(2) CFU/ml could be detected without culture enrichment and amounts as low as 2.6 x 10(3) CFU/ml could be quantified. Furthermore, subjecting viable cells and dead cells to flotation showed that viable cells were recovered after flotation treatment but that dead cells and/or their DNA was not detected. Also, when samples containing VNC cells mixed with dead cells were treated with flotation after storage at 4 or 20 degrees C for 21 days, a similar percentage resembling the VNC cell fraction was detected using real-time PCR and 5-cyano-2,3-ditolyl tetrazolium chloride-4',6'-diamidino-2-phenylindole staining (20% +/- 9% and 23% +/- 4%, respectively, at 4 degrees C; 11% +/- 4% and 10% +/- 2%, respectively, at 20 degrees C). This indicated that viable and VNC Campylobacter cells could be positively selected and quantified using the flotation method.

Inability of cecal microflora to promote reversion of viable nonculturable Campylobacter jejuni

Campylobacter jejuni cells are able to enter a viable but nonculturable (VBNC) state when they are suspended in water. In the present experiments we inoculated day-of-hatch leghorn and broiler chicks with normal gut microflora and subsequently challenged these with high doses of VBNC C. jejuni. The objective was to determine if the pre-establishment of a normal gut flora would enable VBNC Campylobacter to recover, revert to the vibrionic form, and colonize the cecum. Day-of-hatch leghorn and broiler chicks were gavaged through the esophagus with 0.75 ml of a continuous-flow culture of normal cecal organisms. Two days after gavage, the same chicks were gavaged with 0.75 ml (greater than 10(9) colony-forming units) of a VBNC suspension of C. jejuni. Seven days later, cecal contents were collected, serially diluted, and examined for the presence of viable culturable C. jejuni. Our results demonstrated that the VBNC C. jejuni cells were unable to revert to a vibrionic culturable form capable of colonizing the cecum.

Oral immunization of chickens with avirulent Salmonella vaccine strain carrying C. jejuni 72Dz/92 cjaA gene elicits specific humoral immune response associated with protection against challenge with wild-type Campylobacter

It is well documented that poultry and poultry products are the major source of human campylobacteriosis and salmonellosis. This study examined the general efficacy of avirulent Salmonella vaccine strains expressing Campylobacter antigen as a bivalent chicken vaccine prototype. Three C. jejuni genes: cjaA (cj0982c), cjaC (cj0734c) and cjaD (cj0113) encoding highly immunogenic proteins which are conserved among different Campylobacter serotypes, were introduced into avirulent Salmonella enterica sv. Typhimurium (chi 4550 and chi 3987) strains of two different serotypes (UK-1 and SR). The high copy number plasmid pYA3341 Asd(+) was used as a cloning vector. The constitutive expression of all analysed genes as measured by Western immunoblot technique was independent of the particular host strain. Specific rabbit anti-rCjaA antibody reacted not only with CjaA but also with other solute-binding protein (family 3), component of the ABC transport system (CjaC protein), was chosen as the protective antigen for animal experiments. Chickens orally immunized with Salmonella expressing Campylobacter cjaA gene developed serum IgG and mucosal IgA antibody responses against Campylobacter membrane proteins and Salmonella OMPs, as measured by an ELISA test. Protection experiment showed that chicken immunization with avirulent Salmonella carrying Campylobacter cjaA gene greatly reduced the ability of heterologous wild type C. jejuni strain to colonize the bird cecum.

Effect of Campylobacter-specific maternal antibodies on Campylobacter jejuni colonization in young chickens

Using laboratory challenge experiments, we examined whether Campylobacter-specific maternal antibody (MAB) plays a protective role in young chickens, which are usually free of Campylobacter under natural production conditions. Kinetics of C. jejuni colonization were compared by infecting 3-day-old broiler chicks, which were naturally positive for Campylobacter-specific MAB, and 21-day-old broilers, which were negative for Campylobacter-specific MAB. The onset of colonization occurred much sooner in birds challenged at the age of 21 days than it did in the birds inoculated at 3 days of age, which suggested a possible involvement of specific MAB in the delay of colonization. To further examine this possibility, specific-pathogen-free layer chickens were raised under laboratory conditions with or without Campylobacter infection, and their 3-day-old progenies with (MAB(+)) or without (MAB(-)) Campylobacter-specific MAB were orally challenged with C. jejuni. Significant decreases in the percentage of colonized chickens were observed in the MAB(+) group during the first week compared with the MAB(-) group. These results indicate that Campylobacter-specific MAB plays a partial role in protecting young chickens against colonization by C. jejuni. Presence of MAB in young chickens did not seem to affect the development of systemic immune response following infection with C. jejuni. However, active immune responses to Campylobacter occurred earlier and more strongly in birds infected at 21 days of age than those infected at 3 days of age. Clearance of Campylobacter infection was also observed in chickens infected at 21 days of age. Taken together, these findings (i) indicate that anti-Campylobacter MAB contributes to the lack of Campylobacter infection in young broiler chickens in natural environments and (ii) provide further evidence supporting the feasibility of development of immunization-based approaches for control of Campylobacter infection in poultry.

Domestic poultry-raising practices in a Peruvian shantytown: implications for control of Campylobacter jejuni-associated diarrhea

Raising poultry at home is common in many periurban communities in low-income countries. Studies demonstrate that free-range domestic poultry increase children's risk of infection with diarrhea-causing organisms such as Campylobacter jejuni. Corralling might reduce risk, but research on the socioeconomic acceptability of corralling is lacking. To explore this issue, we studied local knowledge and practices related to poultry-raising in a Peruvian shantytown. Our objectives were to understand: (1). motives for raising domestic poultry; (2). economic and cultural factors that affect the feasibility of corralling; and (3). local perceptions about the relationship between domestic poultry and disease. During 1999-2000, we met with community health volunteers and conducted ethnographic and structured interviews with residents about poultry-raising practices. We then enrolled 12 families in a 2-month trial of corral use during which field workers made biweekly surveillance visits to each family. Most participants reported that they raise birds because home-grown poultry and eggs taste better and are more nutritious and because they enjoy living around animals. Some want to teach their children about raising animals. To prevent theft, many residents shut their birds in provisional enclosures at night, but most stated that birds are healthier, happier, and produce better meat and eggs when let loose by day. Many view bird feces in the house and yard as dirty, but few see a connection to illness. Residents consider chicks and ducklings more innocuous than adult birds and are more likely to allow them inside the house and permit children to play with them. After extensive orientation and technical assistance, participants were willing to corral birds more often. But due to perceived disadvantages, many kept birds penned only intermittently. Additional food and water costs were a significant obstacle for some. Adequate space, bird care and corral hygiene would also need to be addressed to make this intervention viable. Developing a secure, acceptable and affordable corral remains a challenge in this population.

A matter of bacterial life and death

Over 50 years ago, standard microbiological methods were established for determining whether bacterial cells were dead or alive. Recently there has been a flurry of reports suggesting that bacteria may exist in an eclipsed state, escaping detection by standard methods. Whether there really is such a state is of more than academic interest, considering the implications for public health. The ensuing debate has been unusually energetic for the normally cultured community of microbiologists.