Survival of Campylobacter jejuni in biofilms isolated from chicken houses

Sodium dichloroisocyanurate: improving broiler health by reducing harmful microbial levels in the waterline

Sodium dichloroisocyanurate (NaDCC) is commonly used for treating drinking water, industrial water, and wastewater. This study aimed to investigate the potential effects of NaDCC-treated waterline drinking water on the growth of AA+ broilers by reducing microbial levels in the waterline. A total of 480 healthy 1-day-old AA+ broilers (46.77 ± 0.50 g) were selected for the experiment and randomly divided into four groups with six replicates of 20 birds each. The control group received regular drinking water, while the test groups received drinking water with NaDCC concentrations of 10, 30, and 50 mg/L. The test groups consumed the treated water on specific days throughout the 42-day experimental period. Results showed that NaDCC treatment significantly reduced the levels of E. coli, Salmonella, S. aureus and Moulds in the drinking water at the waterline (p < 0.05). Drinking water with NaDCC also led to reduced broiler fecal emissions of NH3 and H2S, as well as reduced counts of E. coli, Salmonella, S. aureus and Moulds (p < 0.05), particularly at 30 mg/L and 50 mg/L concentrations. Broilers consuming NaDCC at 50 mg/L exhibited a significant increase in ADG from days 1-42 (p < 0.05). The levels of E. coli, Salmonella, S. aureus and Moulds in the drinking water at the waterline were significantly and positively correlated with the bacterial count in the feces (p < 0.05, R > 0.6). Additionally, bacterial levels in drinking water and broiler feces were negatively correlated with broiler production performance indicators, including ADG, ADFI, F/G and AWC. In conclusion, NaDCC can indirectly enhance broiler performance by reducing the levels of harmful bacteria in the waterline without affecting normal drinking water. The addition of 30 mg/L or 50 mg/L of NaDCC to the waterline in poultry production can effectively control harmful microorganisms and improve poultry health. Based on the experiment's results, it is recommended to preferentially use 30 mg/L NaDCC in the waterline to reduce farming costs.

Pseudomonas fragi biofilm on stainless steel (at low temperatures) affects the survival of Campylobacter jejuni and Listeria monocytogenes and their control by a polymer molybdenum oxide nanocomposite coating

Pseudomonas spp. are widely distributed bacteria on surfaces in the food production and processing environment, where they form extracellular polymeric substance rich biofilms that interact with other bacteria. In this study, the influence of biofilm of Pseudomonas fragi ATCC 4973 on Listeria monocytogenes ATCC 19115 and Campylobacter jejuni NCTC 11168 was investigated at 5 °C and 15 °C on stainless steel in broth and food homogenates (fish or chicken meat). Stainless steel was then coated with PVDF-HFP/PVP/MoO₃ nanocomposite and examined for surface changes (scanning electron microscope, static contact angle, Vickers hardness and elastic modulus). The effect of the prepared nanocomposite coating on P. fragi and on L. monocytogenes and C. jejuni was evaluated in mono- and co-culture. P. fragi produced more biofilm at 15 °C than at 5 °C, especially when food homogenates were used as growth media. Co-cultivation with pathogens did not affect biofilm production by P. fragi, but significant changes were observed in L. monocytogenes and C. jejuni, resulting in a decrease and increase, respectively, in the determined number of culturable biofilm cells. The first change was probably due to competition for the surface, and the second to the oxygen gradient. Stainless steel was then coated with a PVDF-HFP/PVP/MoO₃ nanocomposite, which was characterised by lower roughness and higher wettability, but lower hardness compared to uncoated stainless steel. The prepared nanocoating showed bactericidal activity when tested in phosphate buffered saline. When used in food homogenates, a reduction of over 95 % in bacterial counts was observed. An abundant biofilm of P. fragi proved protective to L. monocytogenes and C. jejuni against the functionalised nanocomposite surface when tested in food homogenates. The control of spoilage Pseudomonas spp., which are common in the food production and processing environment, is important for reducing the contamination of food with spoilage bacteria and with pathogens such as L. monocytogenes and C. jejuni, which may be present in the same environment. The PVDF-HFP/PVP/MoO₃ nanocomposite showed good potential for use as a coating for food contact surfaces, but possible migration of nanoparticles from the nanocomposite coating to food should be evaluated before its commercial use.

Positive biofilms to control surface-associated microbial communities in a broiler chicken production system - a field study

In the One Health concept, the use of beneficial bacteria to form positive biofilms that prevent the settlement of undesirable bacteria is a promising solution to limit the use of antimicrobials on farms. However, there is a lack of field studies reporting the onset of these beneficial bacteria after application and the effects on autochthonous surface microbiota. In the study reported here, the inner surfaces of commercial broiler chicken houses were treated or not with a bacterial consortium composed of Bacillus spp. and Pediococcus spp. strains, able to form covering biofilms in different laboratory models. Preinstalled coupons were sampled over time to capture microbial biofilm dynamics on-farm surfaces. The results showed that the bacterial consortium can establish on the farm surfaces, modulate microbial communities, and limit the implantation of Enterobacteriaceae and Enterococcaceae, two families containing potential pathogens.

Isolation and Characterization of Lytic Bacteriophages Specific for Campylobacter jejuni and Campylobacter coli

In this study, two lytic bacteriophages designated as vB_CjP and vB_CcM were isolated and evaluated for their ability to combat multidrug-resistant bacteria Campylobacter jejuni and Campylobacter coli, respectively. A morphological analysis of these phages by transmission electron microscopy revealed that the vB-CjP bacteriophage had a mean head dimension of 66.6 ± 2.1 nm and a short non-contractile tail and belongs to the Podoviridae family, whereas vB_CcM had a mean head dimension of 80 ± 3.2 nm, a contractile tail, and a length calculated to be 60 ± 2.5 nm and belongs to the Myoviridae family. The results of the host range assay showed that vB_CjP could infect 5 of 10 C. jejuni isolates, whereas vB_CcM could infect 4 of 10 C. coli isolates. Both phages were thermostable and did not lose their infectivity and ability to lyse their host following exposure to 60 °C for 10 min; furthermore, phage particles were relatively stable within a pH range of 6–8. A one-step growth curve indicated that the phages produced estimated burst sizes of 110 and 120 PFU per infected cell with latent periods of 10 and 15 min, for vB-CjP and vB-CcM, respectively. The lytic activity of these phages against planktonic Campylobacter showed that these phages were able to control the growth of Campylobacter in vitro. These results suggest that these phages have a high potential for phage applications and can reduce significantly the counts of Campylobacter spp. The lytic activity of vB-CjP and vB-CcM phages at different (MOIs) against multidrug resistance Campylobacter strains was evaluated. The bacterial growth was slightly delayed by both phages, and the highest efficiency of both phages was observed when MOI = 1 was applied.

Antimicrobial Resistance Gene Transfer from Campylobacter jejuni in Mono- and Dual-Species Biofilms

Horizontal gene transfer (HGT) is a driving force for the dissemination of antimicrobial resistance (AMR) genes among Campylobacter jejuni organisms, a leading cause of foodborne gastroenteritis worldwide. Although HGT is well documented for C. jejuni planktonic cells, the role of C. jejuni biofilms in AMR spread that likely occurs in the environment is poorly understood. Here, we developed a cocultivation model to investigate the HGT of chromosomally encoded AMR genes between two C. jejuni F38011 AMR mutants in biofilms. Compared to planktonic cells, C. jejuni biofilms significantly promoted HGT (P < 0.05), resulting in an increase of HGT frequencies by up to 17.5-fold. Dynamic study revealed that HGT in biofilms increased at the early stage (i.e., from 24 h to 48 h) and remained stable during 48 to 72 h. Biofilms continuously released the HGT mutants into supernatant culture, indicating spontaneous dissemination of AMR to broader niches. DNase I treatment confirmed the role of natural transformation in genetic exchange. HGT was not associated with biofilm biomass, cell density, or bacterial metabolic activity, whereas the presence of extracellular DNA was negatively correlated with the altered HGT frequencies. HGT in biofilms also had a strain-to-strain variation. A synergistic HGT effect was observed between C. jejuni with different genomic backgrounds (i.e., C. jejuni NCTC 11168 chloramphenicol-resistant strain and F38011 kanamycin-resistant strain). C. jejuni performed HGT at the frequency of 10-7 in Escherichia coli-C. jejuni biofilms, while HGT was not detectable in Salmonella enterica-C. jejuni biofilms. IMPORTANCE Antimicrobial-resistant C. jejuni has been listed as a high priority of public health concern worldwide. To tackle the rapid evolution of AMR in C. jejuni, it is of great importance to understand the extent and characteristics of HGT in C. jejuni biofilms, which serve as the main survival strategy of this microbe in the farm-to-table continuum. In this study, we demonstrated that biofilms significantly enhanced HGT compared to the planktonic state (P < 0.05). Biofilm cultivation time and extracellular DNA (eDNA) amount were related to varied HGT frequencies. C. jejuni could spread AMR genes in both monospecies and dual-species biofilms, mimicking the survival mode of C. jejuni in food chains. These findings indicated that the risk and extent of AMR transmission among C. jejuni organisms have been underestimated, as previous HGT studies mainly focused on the planktonic state. Future AMR controlling measures can target biofilms and their main component eDNA.

Pseudomonas putida as a potential biocontrol agent against Salmonella Java biofilm formation in the drinking water system of broiler houses

Background

Environmental biofilms can induce attachment and protection of other microorganisms including pathogens, but can also prevent them from invasion and colonization. This opens the possibility for so-called biocontrol strategies, wherein microorganisms are applied to control the presence of other microbes. The potential for both positive and negative interactions between microbes, however, raises the need for in depth characterization of the sociobiology of candidate biocontrol agents (BCAs). The inside of the drinking water system (DWS) of broiler houses is an interesting niche to apply BCAs, because contamination of these systems with pathogens plays an important role in the infection of broiler chickens and consequently humans. In this study, Pseudomonas putida, which is part of the natural microbiota in the DWS of broiler houses, was evaluated as BCA against the broiler pathogen Salmonella Java.

Results

To study the interaction between these species, an in vitro model was developed simulating biofilm formation in the drinking water system of broilers. Dual-species biofilms of P. putida strains P1, P2, and P3 with S. Java were characterized by competitive interactions, independent of P. putida strain, S. Java inoculum density and application order. When equal inocula of S. Java and P. putida strains P1 or P3 were simultaneously applied, the interaction was characterized by mutual inhibition, whereas P. putida strain P2 showed an exploitation of S. Java. Lowering the inoculum density of S. Java changed the interaction with P. putida strain P3 also into an exploitation of S. Java. A further increase in S. Java inhibition was established by P. putida strain P3 forming a mature biofilm before applying S. Java.

Conclusions

This study provides the first results showing the potential of P. putida as BCA against S. Java in the broiler environment. Future work should include more complex microbial communities residing in the DWS, additional Salmonella strains as well as chemicals typically used to clean and disinfect the system.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-020-02046-5.

Detection of Campylobacter spp. in water by dead-end ultrafiltration and application at farm level

AIMS

The purposes were to evaluate the detection of low levels of Campylobacter in water by dead-end ultrafiltration (DEUF) to determine the sensitivity and suitability for use under field condition.

METHODS AND RESULTS

The DEUF technique followed by detection according to ISO 10272 was tested on artificially and naturally contaminated water. Campylobacter were detected in all samples spiked with more than 10 CFU 60 l-1 and in four of nine samples with a concentration below 10 CFU 60 l-1 water. Naturally contaminated water from five different broiler producers was analysed. Campylobacter were detected in four of 12 samples from ponds near the houses and in three of 24 samples from water pipes inside the broiler houses, but not in tap water sampled at the entrance of the broiler houses.

CONCLUSIONS

The results indicate that DEUF is useful for detection of low numbers of Campylobacter in large volumes of water.

SIGNIFICANCE AND IMPACT OF THE STUDY

Contaminated water is an important source for transmission of Campylobacter to broilers and humans. The concentration of Campylobacter is usually low with a high level of background microbiota. This study shows the advantages of DEUF both in the laboratory and under field conditions.

Trans-Cinnamaldehyde, Eugenol and Carvacrol Reduce Campylobacter jejuni Biofilms and Modulate Expression of Select Genes and Proteins

Campylobacter jejuni is the leading cause of human foodborne illness globally, and is strongly linked with the consumption of contaminated poultry products. Several studies have shown that C. jejuni can form sanitizer tolerant biofilm leading to product contamination, however, limited research has been conducted to develop effective control strategies against C. jejuni biofilms. This study investigated the efficacy of three generally recognized as safe status phytochemicals namely, trans-cinnamaldehyde (TC), eugenol (EG), or carvacrol (CR) in inhibiting C. jejuni biofilm formation and inactivating mature biofilm on common food contact surfaces at 20 and 37°C. In addition, the effect of phytochemicals on biofilm architecture and expression of genes and proteins essential for biofilm formation was evaluated. For the inhibition study, C. jejuni was allowed to form biofilms either in the presence or absence of sub-inhibitory concentrations of TC (0.75 mM), EG (0.61 mM), or CR (0.13 mM) for 48 h and the biofilm formation was quantified at 24-h interval. For the inactivation study, C. jejuni biofilms developed at 20 or 37°C for 48 h were exposed to the phytochemicals for 1, 5, or 10 min and surviving C. jejuni in the biofilm were enumerated. All phytochemicals reduced C. jejuni biofilm formation as well as inactivated mature biofilm on polystyrene and steel surface at both temperatures (P < 0.05). The highest dose of TC (75.64 mM), EG (60.9 mM) and CR (66.56 mM) inactivated (>7 log reduction) biofilm developed on steel (20°C) within 5 min. The genes encoding for motility systems (flaA, flaB, and flgA) were downregulated by all phytochemicals (P < 0.05). The expression of stress response (cosR, ahpC) and cell surface modifying genes (waaF) was reduced by EG. LC-MS/MS based proteomic analysis revealed that TC, EG, and CR significantly downregulated the expression of NapA protein required for oxidative stress response. The expression of chaperone protein DnaK and bacterioferritin required for biofilm formation was reduced by TC and CR. Scanning electron microscopy revealed disruption of biofilm architecture and loss of extracellular polymeric substances after treatment. Results suggest that TC, EG, and CR could be used as a natural disinfectant for controlling C. jejuni biofilms in processing areas.

Occurrence and characterisation of biofilms in drinking water systems of broiler houses

Background

Water quality in the drinking water system (DWS) plays an important role in the general health and performance of broiler chickens. Conditions in the DWS of broilers are ideal for microbial biofilm formation. Since pathogens might reside within these biofilms, they serve as potential source of waterborne transmission of pathogens to livestock and humans. Knowledge about the presence, importance and composition of biofilms in the DWS of broilers is largely missing. In this study, we therefore aim to monitor the occurrence, and chemically and microbiologically characterise biofilms in the DWS of five broiler farms.

Results

The bacterial load after disinfection in DWSs was assessed by sampling with a flocked swab followed by enumerations of total aerobic flora (TAC) and Pseudomonas spp. The dominant flora was identified and their biofilm-forming capacity was evaluated. Also, proteins, carbohydrates and uronic acids were quantified to analyse the presence of extracellular polymeric substances of biofilms. Despite disinfection of the water and the DWS, average TAC was 6.03 ± 1.53 log CFU/20cm². Enumerations for Pseudomonas spp. were on average 0.88 log CFU/20cm² lower. The most identified dominant species from TAC were Stenotrophomonas maltophilia, Pseudomonas geniculata and Pseudomonas aeruginosa. However at species level, most of the identified microorganisms were farm specific. Almost all the isolates belonging to the three most abundant species were strong biofilm producers. Overall, 92% of all tested microorganisms were able to form biofilm under lab conditions. Furthermore, 63% of the DWS surfaces appeared to be contaminated with microorganisms combined with at least one of the analysed chemical components, which is indicative for the presence of biofilm.

Conclusions

Stenotrophomonas maltophilia, Pseudomonas geniculata and Pseudomonas aeruginosa are considered as opportunistic pathogens and could consequently be a potential risk for animal health. Additionally, the biofilm-forming capacity of these organisms could promote attachment of other pathogens such as Campylobacter spp. and Salmonella spp.

Electronic supplementary material

The online version of this article (10.1186/s12866-019-1451-5) contains supplementary material, which is available to authorized users.

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.

Salmonella and Campylobacter biofilm formation: a comparative assessment from farm to fork

It takes several steps to bring food from the farm to the fork (dining table), and contamination with food-borne pathogens can occur at any point in the process. Campylobacter spp. and Salmonella spp. are the main microorganisms responsible for foodborne disease in the EU. These two pathogens are able to persist throughout the food supply chain thanks to their ability to form biofilms. Owing to the high prevalence of Salmonella and especially of Campylobacter in the food supply chain and the huge efforts of food authorities to reduce these levels, it is of great importance to fully understand their mechanisms of persistence. Diverse studies have evaluated the biofilm-forming capacity of foodborne pathogens isolated at different steps of food production. Nonetheless, the principal obstacle of these studies is to reproduce the real conditions that microorganisms encounter in the food supply chain. While there are a wide number of Salmonella biofilm studies, information on Campylobacter biofilms is still limited. A comparison between the two microorganisms could help to develop new research in the field of Campylobacter biofilms. Therefore, this review evaluates relevant work in the field of Salmonella and Campylobacter biofilms and the applicability of the data obtained from these studies to real working conditions. © 2018 Society of Chemical Industry.

Effects of chlorine and hydrogen peroxide sanitation in low bacterial content water on biofilm formation model of poultry brooding house waterlines

An in vitro experiment was performed to determine if biofilm would develop when polyvinylchloride (PVC) test coupons (material used for poultry waterlines) were exposed to low bacterial content warm water (≤1000 cfu/mL, test water) and also to determine if biofilm development would be influenced by adding a sanitizer. PVC sections 2.54 cm long and internal diameter of 1. 90 cm were used as test coupons to grow biofilm. Two coupons were immersed in 600 mL test water in a beaker. Nine beakers were utilized similarly with a total of 18 coupons. Three beakers (T1) were treated with a chlorine (Cl) based product (targeted to produce 2 to 4 ppm residual) and the other 3 (T2) with hydrogen peroxide a (HP) based product (targeted to produce 25 to 50 ppm residual). Three untreated beakers served as controls (T3). All beakers and coupons were placed into a water bath shaker under warm and moving water conditions mimicking poultry brooding conditions. Coupons and test water were sampled for treatments for aerobic plate count (APC). Trial 1 used test water with zero cfu bacteria/mL initial APC, whereas the Trial 2 test water initial APC was 3 log10 cfu/mL. Test water samples and coupons had no bacterial growth for all treatments on sampling occasions for Trial 1. In Trial 2, T3 (control) and T2 (HP treated) had APC growth in both test water (2.5 to 3.0 log10 cfu/mL) and on coupons (2 to 2.5 log10 cfu/cm2) on sampling d with no difference (P > 0.05) between these treatments. Whereas, T1 (Cl treated) eliminated bacteria (zero cfu/mL) in test water and inhibited biofilm growth on test coupons (≤0.2 log10 cfu/cm2) during sampling d (P < 0.05). This experiment showed that biofilm can develop in minimally contaminated water even in the presence of sanitizers, yet chlorine was more effective than hydrogen peroxide in limiting this development.

Effect of chlorine treatment on inhibition of E. coli serogroup O2 incorporation into 7-day-old biofilm on polyvinylchloride surface

Poultry waterlines are constructed using polyvinylchloride (PVC) material on which bacterial biofilm can easily form. Biofilm can harbor pathogens including avian pathogenic E. coli (APEC) strains. An in vitro evaluation was performed to determine if E. coli sero group O2 (avian pathogenic) could attach on a PVC surface that had pre-formed biofilm and if this phenomenon could be affected when water was treated with chlorine. Initially, biofilm growth was induced in PVC test coupons (15.16 cm2) for a 7-day period mimicking the waterline scenario in the first wk of poultry brooding; and then this biofilm was challenged with E. coli O2 seeded water in presence/absence of chlorine treatment. After rinsing, test coupons were sampled for bacterial (APC) and E. coli O2 enumeration at various occasions post seeding the pathogen and chlorine treatment. Day 7 APC recovered from coupons was 4.35 log10 cfu/cm2 in trial 1 and 3.66 log10 cfu/cm2 in trial 2. E. coli O2 was not recovered from chlorine treated test coupons (P < 0.05), whereas it was retrieved from untreated coupons (untreated contained > 3 log10 cfu/cm2 in trial 1 and > 2 log10 cfu/cm2 in trial 2). This study suggests that E. coli O2 can incorporate into pre-formed biofilm on a PVC surface within 24 h if water sanitation is not present, and the attachment time of the pathogen can prolong in the absence of already formed biofilm.

Biofilm growth on polyvinylchloride surface incubated in suboptimal microbial warm water and effect of sanitizers on biofilm removal post biofilm formation

An in vitro experiment was conducted to understand the nature of biofilm growth on polyvinyl chloride (PVC) surface when exposed to suboptimal-quality microbial water (>4 log₁₀ cfu/mL) obtained from a poultry drinking water source mimicking water in waterlines during the first week of poultry brooding condition. PVC sections (internal surface area of 15.16 cm²) were utilized in the study to grow biofilm. After a 7-d test period, test coupons with 7-day-old biofilm were transferred into autoclaved municipal water and then treated with either chlorine-based or hydrogen peroxide-based sanitizer at bird drinking water rate, to see the impact on removal of biofilm formed on test coupons. Two trials (T1 and T2) were conducted. Test coupons used in T1 and T2 had the bacterial growth of 3.67 (SEM 0.04) and 3.97 (SEM 0.11) log₁₀ cfu/cm² on d 7. After sanitizer application, chlorine-based sanitizer removed bacteria in biofilm completely (0 cfu/cm²) within 24 h post treatment whereas hydrogen peroxide-based sanitizer reduced the counts to 1.68 log₁₀ cfu/cm² (P < 0.05) by 48 h post sanitizer application. Control remained the same (P > 0.05). Results indicated that biofilm formation can occur quickly under suboptimal water condition on PVC surface, and sanitizer application helped mitigate already formed biofilm, yet chlorine proved to be more effective than hydrogen peroxide.

Salmonella enterica Serovar Kentucky Flagella Are Required for Broiler Skin Adhesion and Caco-2 Cell Invasion

Nontyphoidal Salmonella strains are the main source of pathogenic bacterial contamination in the poultry industry. Recently, Salmonella enterica serovar Kentucky has been recognized as the most prominent serovar on carcasses in poultry-processing plants. Previous studies showed that flagella are one of the main factors that contribute to bacterial attachment to broiler skin. However, the precise role of flagella and the mechanism of attachment are unknown. There are two different flagellar subunits (fliC and fljB) expressed alternatively in Salmonella enterica serovars using phase variation. Here, by making deletions in genes encoding flagellar structural subunits (flgK, fliC, and fljB), and flagellar motor (motA), we were able to differentiate the role of flagella and their rotary motion in the colonization of broiler skin and cellular attachment. Utilizing a broiler skin assay, we demonstrated that the presence of FliC is necessary for attachment to broiler skin. Expression of the alternative flagellar subunit FljB enables Salmonella motility, but this subunit is unable to mediate tight attachment. Deletion of the flgK gene prevents proper flagellar assembly, making Salmonella significantly less adherent to broiler skin than the wild type. S Kentucky with deletions in all three structural genes, fliC, fljB, and flgK, as well as a flagellar motor mutant (motA), exhibited less adhesion and invasion of Caco-2 cells, while an fljB mutant was as adherent and invasive as the wild-type strain.

IMPORTANCE

In this work, we answered clearly the role of flagella in S Kentucky attachment to the chicken skin and Caco-2 cells. We demonstrated that the presence of FliC is necessary for attachment to broiler skin. Expression of the alternative flagellar subunit FljB enables Salmonella motility, but this subunit is unable to mediate strong attachment. Deletion of the flgK gene prevents proper flagellar assembly, making Salmonella significantly less adherent to broiler skin than the wild type. S Kentucky with deletions in all three structural genes, fliC, fljB, and flgK, as well as a flagellar motor mutant (motA), exhibited less adhesion and invasion of Caco-2 cells, while an fljB mutant was as adherent and invasive as the wild-type strain. We expect these results will contribute to the understanding of the mechanisms of Salmonella attachment to food products.

Chemical, physical and morphological properties of bacterial biofilms affect survival of encased Campylobacter jejuni F38011 under aerobic stress

Campylobacter jejuni is a microaerophilic pathogen and leading cause of human gastroenteritis. The presence of C. jejuni encased in biofilms found in meat and poultry processing facilities may be the major strategy for its survival and dissemination in aerobic environment. In this study, Staphylococcus aureus, Salmonella enterica, or Pseudomonas aeruginosa was mixed with C. jejuni F38011 as a culture to form dual-species biofilms. After 4days' exposure to aerobic stress, no viable C. jejuni cells could be detected from mono-species C. jejuni biofilm. In contrast, at least 4.7logCFU/cm² of viable C. jejuni cells existed in some dual-species biofilms. To elucidate the mechanism of protection mode, chemical, physical and morphological features of biofilms were characterized. Dual-species biofilms contained a higher level of extracellular polymeric substances with a more diversified chemical composition, especially for polysaccharides and proteins, than mono-species C. jejuni biofilm. Structure of dual-species biofilms was more compact and their surface was >8 times smoother than mono-species C. jejuni biofilm, as indicated by atomic force microscopy. Under desiccation stress, water content of dual-species biofilms decreased slowly and remained at higher levels for a longer time than mono-species C. jejuni biofilm. The surface of all biofilms was hydrophilic, but total surface energy of dual-species biofilms (ranging from 52.5 to 56.2mJ/m²) was lower than that of mono-species C. jejuni biofilm, leading to more resistance to wetting by polar liquids. This knowledge can aid in developing intervention strategies to decrease the survival and dispersal of C. jejuni into foods or environment.

L-fucose influences chemotaxis and biofilm formation in Campylobacter jejuni

Campylobacter jejuni and Campylobacter coli are zoonotic pathogens once considered asaccharolytic, but are now known to encode pathways for glucose and fucose uptake/metabolism. For C. jejuni, strains with the fuc locus possess a competitive advantage in animal colonization models. We demonstrate that this locus is present in > 50% of genome-sequenced strains and is prevalent in livestock-associated isolates of both species. To better understand how these campylobacters sense nutrient availability, we examined biofilm formation and chemotaxis to fucose. C. jejuni NCTC11168 forms less biofilms in the presence of fucose, although its fucose permease mutant (fucP) shows no change. In a newly developed chemotaxis assay, both wild-type and the fucP mutant are chemotactic towards fucose. C. jejuni 81-176 naturally lacks the fuc locus and is unable to swim towards fucose. Transfer of the NCTC11168 locus into 81-176 activated fucose uptake and chemotaxis. Fucose chemotaxis also correlated with possession of the pathway for C. jejuni RM1221 (fuc+) and 81116 (fuc-). Systematic mutation of the NCTC11168 locus revealed that Cj0485 is necessary for fucose metabolism and chemotaxis. This study suggests that components for fucose chemotaxis are encoded within the fuc locus, but downstream signals only in fuc + strains, are involved in coordinating fucose availability with biofilm development.

Campylobacter jejuni CsrA Regulates Metabolic and Virulence Associated Proteins and Is Necessary for Mouse Colonization

Campylobacter jejuni infection is a leading bacterial cause of gastroenteritis and a common antecedent leading to Gullian-Barré syndrome. Our previous data suggested that the RNA-binding protein CsrA plays an important role in regulating several important phenotypes including motility, biofilm formation, and oxidative stress resistance. In this study, we compared the proteomes of wild type, csrA mutant, and complemented csrA mutant C. jejuni strains in an effort to elucidate the mechanisms by which CsrA affects virulence phenotypes. The putative CsrA regulon was more pronounced at stationary phase (111 regulated proteins) than at mid-log phase (25 regulated proteins). Proteins displaying altered expression in the csrA mutant included diverse metabolic functions, with roles in amino acid metabolism, TCA cycle, acetate metabolism, and various other cell processes, as well as pathogenesis-associated characteristics such as motility, chemotaxis, oxidative stress resistance, and fibronectin binding. The csrA mutant strain also showed altered autoagglutination kinetics when compared to the wild type. CsrA specifically bound the 5' end of flaA mRNA, and we demonstrated that CsrA is a growth-phase dependent repressor of FlaA expression. Finally, the csrA mutant exhibited reduced ability to colonize in a mouse model when in competition with the wild type, further underscoring the role of CsrA in C. jejuni colonization and pathogenesis.

Pancreatic amylase is an environmental signal for regulation of biofilm formation and host interaction in Campylobacter jejuni

Campylobacter jejuni is a commensal bacterium in the intestines of animals and birds and a major cause of food-borne gastroenteritis in humans worldwide. Here we show that exposure to pancreatic amylase leads to secretion of an α-dextran by C. jejuni and that a secreted protease, Cj0511, is required. Exposure of C. jejuni to pancreatic amylase promotes biofilm formation in vitro, increases interaction with human epithelial cell lines, increases virulence in the Galleria mellonella infection model, and promotes colonization of the chicken ileum. We also show that exposure to pancreatic amylase protects C. jejuni from stress conditions in vitro, suggesting that the induced α-dextran may be important during transmission between hosts. This is the first evidence that pancreatic amylase functions as an interkingdom signal in an enteric microorganism.

Evaluation of Propidium Monoazide and Quantitative PCR To Quantify Viable Campylobacter jejuni Biofilm and Planktonic Cells in Log Phase and in a Viable but Nonculturable State

Despite being considered fragile and fastidious, Campylobacter jejuni remains the leading cause of bacterial gastroenteritis in the developed world. C. jejuni survives stresses by forming biofilms or entering a viable but nonculturable (VBNC) state. To investigate the number of viable cells in samples exposed to low nutrient and temperature stress, a novel method, propidium monoazide quantitative PCR (PMAqPCR), was compared with Bac Light biovolume analysis and conventional plate counting for the enumeration of C. jejuni-removed biofilm cells and separately grown planktonic cells in late log phase (24 h). There were no significant differences between viable cell counts obtained using PMAqPCR and those from plate counts or Bac Light biovolume analyses for each sample, confirming that this method provides results consistent with those from accepted enumeration methods (P > 0.05). To induce a VBNC state, C. jejuni planktonic cells and dislodged and washed biofilm cells were separately incubated in phosphate-buffered saline at 4°C for up to 60 days. Even when cells exposed to stress were provided with enrichment in Bolton broth before plating, treated biofilm cells lost culturability by day 10, whereas their planktonic counterparts remained culturable to day 60. The nonculturable biofilm cells remained viable in high numbers to day 60, and viable cell counts from the PMAqPCR (6.15 log cells per ml) were not significantly different from those obtained using the Bac Light assay (6.98 log cells per ml) (P > 0.05), confirming that this novel method is also reliable for cells exposed to stress for extended periods. PMAqPCR shows promise for analysis where C. jejuni exists in biofilms or in the VBNC state. Adopting PMAqPCR in routine monitoring, in conjunction with improved biofilm cell collection methods, will allow for more accurate enumeration of viable and potentially virulent cells, leading to improved sanitation and reduced incidence of infection.

Thermotolerant Campylobacter during Broiler Rearing: Risk Factors and Intervention

Thermotolerant Campylobacters are one of the most important bacterial causative agents of human gastrointestinal illness worldwide. In most European Union (EU) member states human campylobacteriosis is mainly caused by infection with Campylobacter jejuni or Campylobacter coli following consumption or inadequate handling of Campylobacter-contaminated poultry meat. To date, no effective strategy to control Campylobacter colonization of broilers during rearing is available. In this review, we describe the public health problem posed by Campylobacter presence in broilers and list and critically review all currently known measures that have been researched to lower the numbers of Campylobacter bacteria in broilers during rearing. We also discuss the most promising measures and which measures should be investigated further. We end this review by elaborating on readily usable measures to lower Campylobacter introduction and Campylobacter numbers in a broiler flock.

Does Campylobacter jejuni form biofilms in food-related environments?

Campylobacter jejuni is one of the most frequent causes of bacterial gastrointestinal food-borne infection worldwide. This species is part of the normal flora of the gastrointestinal tracts of animals used for food production, including poultry, which is regarded as the primary source of human Campylobacter infections. The survival and persistence of C. jejuni in food processing environments, especially in poultry processing plants, represent significant risk factors that contribute to the spread of this pathogen through the food chain. Compared to other food-borne pathogens, C. jejuni is more fastidious in its growth requirements and is very susceptible to various environmental stressors. Biofilm formation is suggested to play a significant role in the survival of C. jejuni in the food production and processing environment. The aims of this minireview were (i) to examine the evidence that C. jejuni forms biofilms and (ii) to establish the extent to which reported and largely laboratory-based studies of C. jejuni biofilms provide evidence for biofilm formation by this pathogen in food processing environments. Overall existing studies do not provide strong evidence for biofilm formation (as usually defined) by most C. jejuni strains in food-related environments under the combined conditions of atmosphere, temperature, and shear that they are likely to encounter. Simple attachment to and survival on surfaces and in existing biofilms of other species are far more likely to contribute to C. jejuni survival in food-related environments based on our current understanding of this species.

Flagella-mediated adhesion and extracellular DNA release contribute to biofilm formation and stress tolerance of Campylobacter jejuni

Campylobacter jejuni is a leading cause of foodbourne gastroenteritis, despite fragile behaviour under standard laboratory conditions. In the environment, C. jejuni may survive within biofilms, which can impart resident bacteria with enhanced stress tolerance compared to their planktonic counterparts. While C. jejuni forms biofilms in vitro and in the wild, it had not been confirmed that this lifestyle confers stress tolerance. Moreover, little is understood about molecular mechanisms of biofilm formation in this pathogen. We previously found that a ΔcprS mutant, which carries a deletion in the sensor kinase of the CprRS two-component system, forms enhanced biofilms. Biofilms were also enhanced by the bile salt deoxycholate and contained extracellular DNA. Through more in-depth analysis of ΔcprS and WT under conditions that promote or inhibit biofilms, we sought to further define this lifestyle for C. jejuni. Epistasis experiments with ΔcprS and flagellar mutations (ΔflhA, ΔpflA) suggested that initiation is mediated by flagellum-mediated adherence, a process which was kinetically enhanced by motility. Lysis was also observed, especially under biofilm-enhancing conditions. Microscopy suggested adherence was followed by release of eDNA, which was required for biofilm maturation. Importantly, inhibiting biofilm formation by removal of eDNA with DNase decreased stress tolerance. This work suggests the biofilm lifestyle provides C. jejuni with resilience that has not been apparent from observation of planktonic bacteria during routine laboratory culture, and provides a framework for subsequent molecular studies of C. jejuni biofilms.

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.

Cleaning conveyor belts in the chicken-cutting area of a poultry processing plant with 45°c water

Conveyor belts are widely used in food handling areas, especially in poultry processing plants. Because they are in direct contact with food and it is a requirement of the Brazilian health authority, conveyor belts are required to be continuously cleaned with hot water under pressure. The use of water in this procedure has been questioned based on the hypothesis that water may further disseminate microorganisms but not effectively reduce the organic material on the surface. Moreover, reducing the use of water in processing may contribute to a reduction in costs and emission of effluents. However, no consistent evidence in support of removing water during conveyor belt cleaning has been reported. Therefore, the objective of the present study was to compare the bacterial counts on conveyor belts that were or were not continuously cleaned with hot water under pressure. Superficial samples from conveyor belts (cleaned or not cleaned) were collected at three different times during operation (T1, after the preoperational cleaning [5 a.m.]; T2, after the first work shift [4 p.m.]; and T3, after the second work shift [1:30 a.m.]) in a poultry meat processing facility, and the samples were subjected to mesophilic and enterobacterial counts. For Enterobacteriaceae, no significant differences were observed between the conveyor belts, independent of the time of sampling or the cleaning process. No significant differences were observed between the counts of mesophilic bacteria at the distinct times of sampling on the conveyor belt that had not been subjected to continuous cleaning with water at 45°C. When comparing similar periods of sampling, no significant differences were observed between the mesophilic counts obtained from the conveyor belts that were or were not subjected to continuous cleaning with water at 45°C. Continuous cleaning with water did not significantly reduce microorganism counts, suggesting the possibility of discarding this procedure in chicken processing.

Transmission OF Campylobacter coli in chicken embryos

Campylobacter coli is an important species involved in human cases of enteritis, and chickens are carriers of the pathogen mainly in developing country. The current study aimed to evaluate the transmission of C. coli and its pathogenic effects in chicken embryos. Breeder hens were inoculated intra-esophageally with C. coli isolated from chickens, and their eggs and embryos were analyzed for the presence of bacteria using real-time PCR and plate culture. The viability of embryos was verified. In parallel, SPF eggs were inoculated with C. coli in the air sac; after incubation, the embryos were submitted to the same analysis as the embryos from breeder hens. In embryos and fertile eggs from breeder hens, the bacterium was only identified by molecular methods; in the SPF eggs, however, the bacterium was detected by both techniques. The results showed no relationship between embryo mortality and positivity for C. coli in the embryos from breeder hens. However, the presence of bacteria is a cause of precocious mortality for SPF embryos. This study revealed that although the vertical transmission is a possible event, the bacteria can not grow in embryonic field samples.

Characterization of mono- and mixed-culture Campylobacter jejuni biofilms

Campylobacter jejuni, one of the most common causes of human gastroenteritis, is a thermophilic and microaerophilic bacterium. These characteristics make it a fastidious organism, which limits its ability to survive outside animal hosts. Nevertheless, C. jejuni can be transmitted to both humans and animals via environmental pathways, especially through contaminated water. Biofilms may play a crucial role in the survival of the bacterium under unfavorable environmental conditions. The goal of this study was to investigate survival strategies of C. jejuni in mono- and mixed-culture biofilms. We grew monoculture biofilms of C. jejuni and mixed-culture biofilms of C. jejuni with Pseudomonas aeruginosa. We found that mono- and mixed-culture biofilms had significantly different structures and activities. Monoculture C. jejuni biofilms did not consume a measurable quantity of oxygen. Using a confocal laser scanning microscope (CLSM), we found that cells from monoculture biofilms were alive according to live/dead staining but that these cells were not culturable. In contrast, in mixed-culture biofilms, C. jejuni remained in a culturable physiological state. Monoculture C. jejuni biofilms could persist under lower flow rates (0.75 ml/min) but were unable to persist at higher flow rates (1 to 2.5 ml/min). In sharp contrast, mixed-culture biofilms were more robust and were unaffected by higher flow rates (2.5 ml/min). Our results indicate that biofilms provide an environmental refuge that is conducive to the survival of C. jejuni.

Bacteriophage-Mediated Dispersal of Campylobacter jejuni Biofilms

Bacteria in their natural environments frequently exist as mixed surface-associated communities, protected by extracellular material, termed biofilms. Biofilms formed by the human pathogen Campylobacter jejuni may arise in the gastrointestinal tract of animals but also in water pipes and other industrial situations, leading to their possible transmission into the human food chain either directly or via farm animals. Bacteriophages are natural predators of bacteria that usually kill their prey by cell lysis and have potential application for the biocontrol and dispersal of target bacteria in biofilms. The effects of virulent Campylobacter specific-bacteriophages CP8 and CP30 on C. jejuni biofilms formed on glass by strains NCTC 11168 and PT14 at 37°C under microaerobic conditions were investigated. Independent bacteriophage treatments (n ≥ 3) led to 1 to 3 log₁₀ CFU/cm² reductions in the viable count 24 h postinfection compared with control levels. In contrast, bacteriophages applied under these conditions effected a reduction of less than 1 log₁₀ CFU/ml in planktonic cells. Resistance to bacteriophage in bacteria surviving bacteriophage treatment of C. jejuni NCTC 11168 biofilms was 84% and 90% for CP8 and CP30, respectively, whereas bacteriophage resistance was not found in similarly recovered C. jejuni PT14 cells. Dispersal of the biofilm matrix by bacteriophage was demonstrated by crystal violet staining and transmission electron microscopy. Bacteriophage may play an important role in the control of attachment and biofilm formation by Campylobacter in situations where biofilms occur in nature, and they have the potential for application in industrial situations leading to improvements in food safety.

Survival of Campylobacter jejuni on beef and pork under vacuum packaged and retail storage conditions: examination of the role of natural meat microflora on C. jejuni survival

The ability of Campylobacter jejuni ATCC 11168 to survive on beef and pork stored under chilled, vacuum packaged and retail display conditions were examined. In addition, the effect of natural microflora on commercial beef and pork on the survival of C. jejuni under these storage conditions was examined. When sterile cores of beef and pork were inoculated with ∼ 10(5) to 10(6) cfu cm(-2)C. jejuni, and were stored under aerobic or vacuum packaged conditions at -1.5 or 4 °C, its numbers dropped significantly and C. jejuni could not be enumerated by direct plating after 21 d of the 6 wks study. In contrast, survival of C. jejuni on commercial vacuum packaged beef and pork was significantly enhanced, resulting in only 1 log cfu cm(-2) reduction at the end of 6 wks. During 7 d of display in a retail case, numbers of C. jejuni dropped quickly, but could be enumerated by direct plating even after the 7 d. The presence of high numbers of inoculated C. jejuni on beef and pork had no significant effect on the natural microflora numbers compared to uninoculated controls when the meat was stored either in vacuum or in a retail display case. These results show that natural microflora on vacuum packaged meat afford enhanced survival of C. jejuni present on the surfaces of both beef and pork when stored at refrigeration temperatures. Hence, strict hygienic practices or the implementation of decontamination technologies are recommended to ensure safety of meat with respect to this pathogen.

Evaluation of different selective media and culturing techniques for the quantification of Campylobacter ssp. from broiler litter

Poultry is a major reservoir for Campylobacter, the leading cause of foodborne illness in the United States, but how broilers become initially colonized is still under debate. Broiler litter is a potential source, but the best technique for quantifying Campylobacter from litter is still unknown. Therefore, our objectives were to determine if certain media are more selective for quantifying Campylobacter and if enrichment allows for the detection of stressed or viable but nonculturable cells from broiler litter samples. In this trial, 5 media and 2 culturing techniques were used to enumerate Campylobacter from broiler litter. The media used were campy-Line agar (CLA), campy-cefex agar (CCA), modified CCA, Campylobacter agar plates (CAP), and modified charcoal cefoperazone deoxycholate agar. Litter samples were obtained from a commercial broiler house. Each sample was equally divided and diluted 10-fold into peptone, for direct plating, or 4-fold into Campylobacter enrichment broth. Samples diluted in peptone were direct-plated onto each media and incubated under microaerophilic conditions for 48 h at 42 degrees C. Samples diluted in enrichment broth were incubated under the same conditions for 24 h, then further diluted to 10-fold before plating. Plates from enriched samples were incubated for an additional 24 h after plating. After incubation, all plates (direct and enriched) were counted and presumptive positive colonies were confirmed using a Campylobacter latex agglutination kit. Results indicated that there was no difference in the ability of any of the selective media tested to grow Campylobacter. Direct-plated samples had a higher Campylobacter isolation rate compared with enriched samples. The CLA and CAP were able to suppress total bacterial growth better than modified charcoal cefoperazone deoxycholate, modified CCA, and CCA. The CLA and CAP were the only media able to detect total bacterial population shifts over time. In conclusion, it is important before making a final decision on a selective medium to consider the medium's ability to suppress total bacterial growth as well as isolate Campylobacter.

Biofilm formation in bacterial pathogens of veterinary importance

Bacterial biofilms are structured communities of bacterial cells enclosed in a self-produced polymer matrix that is attached to a surface. Biofilms protect and allow bacteria to survive and thrive in hostile environments. Bacteria within biofilms can withstand host immune responses, and are much less susceptible to antibiotics and disinfectants when compared with their planktonic counterparts. The ability to form biofilms is now considered a universal attribute of micro-organisms. Diseases associated with biofilms require novel methods for their prevention, diagnosis and treatment; this is largely due to the properties of biofilms. Surprisingly, biofilm formation by bacterial pathogens of veterinary importance has received relatively little attention. Here, we review the current knowledge of bacterial biofilms as well as studies performed on animal pathogens.

Survival of Campylobacter jejuni under conditions of atmospheric oxygen tension with the support of Pseudomonas spp

Campylobacter jejuni is a major food-borne pathogen. Despite causing enteritis in humans, it is a well-adapted intestinal microorganism in animals, hardly ever generating disease symptoms. Nevertheless, as a true microaerophilic microorganism it is still puzzling how Campylobacter cells can survive on chicken meat, the main source of human infection. In this study, we demonstrate that C. jejuni is able to withstand conditions of atmospheric oxygen tension when cocultured with Pseudomonas species, major food-spoiling bacteria that are frequently found on chicken meat in rather high numbers. Using an in vitro survival assay, interactions of 145 C. jejuni wild-type strains and field isolates from chicken meat, broiler feces, and human clinical samples with type strains and food isolates of Pseudomonas spp., Proteus mirabilis, Citrobacter freundii, Micrococcus luteus, and Enterococcus faecalis were studied. When inoculated alone or in coculture with Proteus mirabilis, Citrobacter freundii, Micrococcus luteus, or Enterococcus faecalis type strains, Campylobacter cells were able to survive ambient oxygen levels for no more than 18 h. In contrast, Campylobacter bacteria inoculated with type strains or wild-type isolates of Pseudomonas showed a prolonged aerobic survival of up to >48 h. This microbial commensalism was diverse in C. jejuni isolates from different sources; isolates from chicken meat and humans in coculture with Pseudomonas putida were able to use this survival support better than fecal isolates from broilers. Scanning electron microscopy revealed the development of fiberlike structures braiding P. putida and C. jejuni cells. Hence, it seems that microaerophilic C. jejuni is able to survive ambient atmospheric oxygen tension by metabolic commensalism with Pseudomonas spp. This bacterium-bacterium interaction might set the basis for survival of C. jejuni on chicken meat and thus be the prerequisite step in the pathway toward human infection.

A new microtitre plate screening method for evaluating the viability of aerobic respiring bacteria in high surface biofilms

AIMS

It is difficult to determine the effects of bactericidal compounds against bacteria in a biofilm because classical procedures for determining cell viability require several working days, multiple complicated steps and are frequently only applicable to cells in suspension. We attempt to develop a compact, inexpensive and versatile system to measure directly the extent of biofilm formation from water systems and to determine the viability of respiring bacteria in high surface biofilms.

METHODS AND RESULTS

It has been reported that the reduction of tetrazolium sodium salts, such as XTT (sodium 3,3'-[1-[(phenylamino)carbonyl]-3,4-tetrazolium]Bis(4-methoxy)-6-nitro)benzene sulfonic acid hydrate), during active bacterial metabolism can be incorporated into a colorimetric method for quantifying cell viability. XTT is reduced to a soluble formazan compound during bacterial aerobic metabolism such that the amount of formazan generated is proportional to the bacterial biomass.

CONCLUSIONS

We show here, for the first time, that this colorimetric approach can be used to determine the metabolic activity of adherent aerobic bacteria in a biofilm as a measure of cell viability. This technique has been used to estimate viability and proliferation of bacteria in suspension, but this is the first application to microbial communities in a real undisturbed biofilm.

SIGNIFICANCE AND IMPACT OF THE STUDY

This simple new system can be used to evaluate the complex biofilm community without separating the bacteria from their support. Thus, the results obtained by this practice may be more representative of the circumstances in a natural system, opening the possibility to multiple potential applications.

The ability of Campylobacter jejuni cells to attach to stainless steel does not change as they become nonculturable

The ability of Campylobacter jejuni strains to attach to stainless steel as they became nonculturable during storage in distilled water at 4 degrees C for 30 days was investigated. From an initial count of approximately 7 log colony-forming units/mL all strains completely lost culturability by day 20, but the numbers of cells attaching to stainless steel remained constant at approximately 3.5 log cells/cm(2). These findings suggest that viable but nonculturable Campylobacter in a liquid matrix can still attach to stainless steel.

Planktonic and biofilm communities from 7-day-old chicken cecal microflora cultures: characterization and resistance to Salmonella colonization

Information implicating bacterial biofilms as contributory factors in the development of environmental bacterial resistance has been increasing. There is a lack of information regarding the role of biofilms within the microbial ecology of the gastrointestinal tract of food animals. This work used a continuous-flow chemostat model derived from the ceca of 7-day-old chicks to characterize these communities and their ability to neutralize invasion by Salmonella enterica serovar Typhimurium. We characterized and compared the biofilm and planktonic communities within these microcosms using automated ribotyping and the Analytical Profile Index biotyping system. Eleven species from eight different genera were identified from six culture systems. Klebsiella pneumoniae was isolated from all planktonic communities and four of the biofilm communities. Three of the communities resisted colonization by Salmonella enterica serovar Typhimurium, two communities suppressed growth, and one community succumbed to colonization. In cultures that resisted colonization, no Salmonella could be isolated from the biofilm; in cultures that succumbed to colonization, Salmonella was consistently found within the biofilms. This study was one of a series that provided a molecular-based characterization of both the biofilm and planktonic communities from continuous-flow culture systems derived from the cecal microflora of chicks, ranging in age from day-of-hatch to 14 days old. The one common factor relating to successful colonization of the culture was the presence of Salmonella within the biofilm. The capacity to sequester the introduced Salmonella into the biofilm appears to be a contributing factor to the inability of these cultures to withstand colonization by the Salmonella.

Characterization of planktonic and biofilm communities of day-of-hatch chicks cecal microflora and their resistance to Salmonella colonization

Recent concerns about the use of antimicrobials in food animals have increased interest in the microbial ecology and biofilms within their gastrointestinal tract. This work used a continuous-flow chemostat system to model the microbial community within the ceca from day-of-hatch chicks and its ability to resist colonization by Salmonella enterica serovar Typhimurium. We characterized the biofilm and planktonic communities from five cultures by using automated ribotyping. Eight species from six different genera were identified. Overall, the planktonic communities were more diverse, with 40% of the cultures containing four or more bacterial species. Eighty percent of the biofilm communities contained only one or two species of bacteria. Enterococcus faecalis was the only species isolated from all communities. None of the resulting microbial communities was able to resist colonization by S. enterica serovar Typhimurium. This is the first study to provide a molecular-based characterization of the biofilm and planktonic communities found in day-of-hatch chicken cecal microflora cultures.

The CprS sensor kinase of the zoonotic pathogen Campylobacter jejuni influences biofilm formation and is required for optimal chick colonization

Campylobacter jejuni, a prevalent cause of bacterial gastroenteritis, must adapt to different environments to be a successful pathogen. We previously identified a C. jejuni two-component regulatory system (Cj1226/7c) as upregulated during cell infections. Analyses described herein led us to designate the system CprRS (Campylobacter planktonic growth regulation). While the response regulator was essential, a cprS sensor kinase mutant was viable. The Delta cprS mutant displayed an apparent growth defect and formed dramatically enhanced and accelerated biofilms independent of upregulation of previously characterized surface polysaccharides. Delta cprS also displayed a striking dose-dependent defect for colonization of chicks and was modestly enhanced for intracellular survival in INT407 cells. Proteomics analyses identified changes consistent with modulation of essential metabolic genes, upregulation of stress tolerance proteins, and increased expression of MOMP and FlaA. Consistent with expression profiling, we observed enhanced motility and secretion in Delta cprS, and decreased osmotolerance and oxidative stress tolerance. We also found that C. jejuni biofilms contain a DNase I-sensitive component and that biofilm formation is influenced by deoxycholate and the metabolic substrate fumarate. These results suggest that CprRS influences expression of factors important for biofilm formation, colonization and stress tolerance, and also add to our understanding of C. jejuni biofilm physiology.

Planktonic and biofilm community characterization and Salmonella resistance of 14-day-old chicken cecal Microflora-derived continuous-flow cultures

This study evaluated the composition of gastrointestinal bacterial communities in birds during an age in which their susceptibility to Salmonella is highly diminished. One of the challenges to developing probiotics is to develop an efficacious culture of minimal diversity that includes bacteria that are vital contributors to protection from pathogens, but excludes unnecessary species. This study used in vitro continuous-flow culture techniques to test the ability of mixed bacterial cultures acquired from in vivo sources, to resist colonization by a marker Salmonella enterica serovar Typhimurium, and then characterized the constituents of both biofilm and planktonic communities by biochemical, phenotypic, and molecular methods. These cultures, initiated from 14-day-old chicks, were all able to restrict colonization by Salmonella in an average of 10 days. Eighteen species of bacteria from 10 different genera were characterized. However, each culture contained a mixture of only 11 species, which included lactic acid bacteria. Biofilms contained less than 50% of the species found in the planktonic communities. Although not adults, the diversity of microbes within the cecal cultures from 14-day-old birds represents a community complex enough to oppose colonization by a nonindigenous bacteria in vitro. These results describe bacterial mixtures containing less diversity than in previously described avian protective cultures.