Aerobic growth and survival of Campylobacter jejuni in food and stream water

Effect of biofilm formation in a hostile oxidative stress environment on the survival of Campylobacter jejuni recovered from poultry in Iraqi markets

Background and Aim

Campylobacter jejuni is a major contributor to bacterial enteritis, a common health problem. The resistance of this microaerophilic bacterium to oxidative stress allows it to thrive under aerobic conditions. This study aimed to investigate whether the capacity of C. jejuni to form biofilms in the presence of oxidative stress contributes to the pathogen's ability to thrive in agricultural settings as well as in chicken slaughter lines.

Materials and Methods

Twenty identified strains originating from chicken samples (eight from caeca contents and 12 from frozen chicken carcasses) were previously isolated and identified according to standard bacteriological protocols, followed by confirmation at the species level using multiplex polymerase chain reaction assay. Crystal violet staining was used to evaluate biofilm formation by these bacteria. Two exposure periods to gaseous ozone (1 and 2 min) were used to assess resistance to oxidative damage.

Results

Most of the strong biofilm-forming Campylobacter strains came from imported frozen chicken meat (25%), whereas only 10% came from caeca content. After exposure to gaseous ozone at 600 mg/h for 2 min, strong biofilm-producing strains exhibited a higher survival rate with a limited reduction of up to 3 logs, whereas negative biofilm-producing strains exhibited a limited survival rate with a reduction of 6 logs.

Conclusion

Based on our findings, we hypothesized that the presence of C. jejuni strains capable of forming biofilms in poultry farms and/or chicken production facilities triggers a public health alarm as this bacterium seems to be able to adapt more easily to live and thrive in hostile environmental conditions.

Survival capability of Campylobacter upsaliensis under environmental stresses

Objective

Campylobacter upsaliensis has been recognized as an emerging pathogen. However, little is known about its survival in the environment. To evaluate its survival capability, we estimated the reduction in viable counts of C. upsaliensis after aerobic exposure to starvation in phosphate-buffered saline (PBS), acidity (pH = 4.3), high osmolarity (4% NaCl), and dryness in wet pulp disks at different temperatures. Also, survival in dog feces and dog food at variable temperate was assessed.

Results

Campylobacter upsaliensis remained culturable under starvation for 4 days at 25 °C and for 10 weeks at 4 °C. C. upsaliensis was also recoverable after exposure to high osmolality for 9 days, dryness for 5 days, and acidity for 2 days, respectively. Similarly, C. upsaliensis survived in dog feces and dog food for several days at 25 °C and weeks at 4 °C. The survival capability of the organism was dependent on the water content, and also temperature. Notably, the tested C. upsaliensis strain was less resilient under all tested conditions than a C. jejuni strain used as a control. The findings showed that C. upsaliensis is able to survive under various environmental stresses, suggesting that it could pose a potential threat to public health.

Waterborne Isolates of Campylobacter jejuni Are Able to Develop Aerotolerance, Survive Exposure to Low Temperature, and Interact With Acanthamoeba polyphaga

Campylobacter jejuni is regarded as the leading cause of bacterial gastroenteritis around the world. Even though it is generally considered to be a sensitive microaerobic pathogen, it is able to survive in the environment outside of the intestinal tract of the host. This study aimed to assess the impact of selected environmental parameters on the survival of 14 C. jejuni isolates of different origins, including 12 water isolates. The isolates were tested for their antibiotic resistance, their ability to survive at low temperature (7°C), develop aerotolerance, and to interact with the potential protozoan host Acanthamoeba polyphaga. The antibiotic susceptibility was determined by standard disk diffusion according to EUCAST. Out of the 14 isolates, 8 were resistant to ciprofloxacin (CIP) and 5 to tetracycline (TET), while only one isolate was resistant to erythromycin (ERY). Five isolates were resistant to two different antibiotic classes. Tetracycline resistance was only observed in isolates isolated from wastewater and a clinical sample. Further, the isolates were tested for their survival at 7°C under both aerobic and microaerobic conditions using standard culture methods. The results showed that under microaerobic conditions, all isolates maintained their cultivability for 4 weeks without a significant decrease in the numbers of bacteria and variation between the isolates. However, significant differences were observed under aerobic conditions (AC). The incubation led to a decrease in the number of cultivable cells, with complete loss of cultivability after 2 weeks (one water isolate), 3 weeks (7 isolates), or 4 weeks of incubation (6 isolates). Further, all isolates were studied for their ability to develop aerotolerance by repetitive subcultivation under microaerobic and subsequently AC. Surprisingly, all isolates were able to adapt and grow under AC. As the last step, 5 isolates were selected to evaluate a potential protective effect provided by A. polyphaga. The cocultivation of isolates with the amoeba resulted in the survival of about 40% of cells treated with an otherwise lethal dose of gentamicin. In summary, C. jejuni is able to adapt and survive in a potentially detrimental environment for a prolonged period of time, which emphasizes the role of the environmental transmission route in the spread of campylobacteriosis.

Characterisation of Aerotolerant Forms of a Robust Chicken Colonizing Campylobacter coli

Campylobacter contaminated poultry meat is a major source of human foodborne illness. Campylobacter coli strain OR12 is a robust colonizer of chickens that was previously shown to outcompete and displace other Campylobacter strains from the chicken's gastrointestinal tract. This strain is capable of aerobic growth on blood agar. Serial aerobic passage increased this aerotolerance as assessed by quantitative assays for growth and survival on solid media. Aerotolerance was also associated with increased peroxide stress resistance. Aerobic passage did not alter cellular morphology or motility or hinder the microaerobic growth rate. Colonization of broiler chickens by aerotolerant C. coli OR12 was significantly lower than the wild-type strain at 3 days after challenge but not by 7 days, suggesting adaptation had occurred. Bacteria recovered from chickens had retained their aerotolerance, indicating this trait is stable. Whole genome sequencing enabled comparison with the wild-type sequence. Twenty-three point mutations were present, none of which were in genes known to affect oxidative stress resistance. Insertions or deletions caused frame shifts in several genes including, phosphoglycerate kinase and the b subunit of pyruvate carboxylase that suggest modification of central and carbohydrate metabolism in response to aerobic growth. Other genes affected include those encoding putative carbonic anhydrase, motility accessory factor, filamentous haemagglutinin, and aminoacyl dipeptidase proteins. Aerotolerance has the potential to affect environmental success and survival. Increased environmental survival outside of the host intestinal tract may allow opportunities for transmission between hosts. Resistance to oxidative stress may equate to increased virulence by virtue of reduced susceptibility to oxidative free radicals produced by host immune responses. Finally, resistance to ambient atmospheric oxygen may allow increased survival on chicken skin, and therefore constitutes an increased risk to public health.

Cellulose accessibility and microbial community in solid state anaerobic digestion of rape straw

Solid state anaerobic digestion (SSAD) with leachate recirculation is an appropriate method for the valorization of agriculture residues. Rape straw is a massively produced residue with considerable biochemical methane potential, but its degradation in SSAD remains poorly understood. A thorough study was conducted to understand the performance of rape straw as feedstock for laboratory solid state anaerobic digesters. We investigated the methane production kinetics of rape straw in relation to cellulose accessibility to cellulase and the microbial community. Improving cellulose accessibility through milling had a positive influence on both the methane production rate and methane yield. The SSAD of rape straw reached 60% of its BMP in a 40-day pilot-scale test. Distinct bacterial communities were observed in digested rape straw and leachate, with Bacteroidales and Sphingobacteriales as the most abundant orders, respectively. Archaeal populations showed no phase preference and increased chronologically.

Adhesion, Biofilm Formation, and Genomic Features of Campylobacter jejuni Bf, an Atypical Strain Able to Grow under Aerobic Conditions

Campylobacter jejuni is the leading cause of bacterial enteritis in Europe. Human campylobacteriosis cases are frequently associated to the consumption of contaminated poultry meat. To survive under environmental conditions encountered along the food chain, i.e., from poultry digestive tract its natural reservoir to the consumer's plate, this pathogen has developed adaptation mechanisms. Among those, biofilm lifestyle has been suggested as a strategy to survive in the food environment and under atmospheric conditions. Recently, the clinical isolate C. jejuni Bf has been shown to survive and grow under aerobic conditions, a property that may help this strain to better survive along the food chain. The aim of this study was to evaluate the adhesion capacity of C. jejuni Bf and its ability to develop a biofilm. C. jejuni Bf can adhere to abiotic surfaces and to human epithelial cells, and can develop biofilm under both microaerobiosis and aerobiosis. These two conditions have no influence on this strain, unlike results obtained with the reference strain C. jejuni 81-176, which harbors only planktonic cells under aerobic conditions. Compared to 81-176, the biofilm of C. jejuni Bf is more homogenous and cell motility at the bottom of biofilm was not modified whatever the atmosphere used. C. jejuni Bf whole genome sequence did not reveal any gene unique to this strain, suggesting that its unusual property does not result from acquisition of new genetic material. Nevertheless some genetic particularities seem to be shared only between Bf and few others strains. Among the main features of C. jejuni Bf genome we noticed (i) a complete type VI secretion system important in pathogenicity and environmental adaptation; (ii) a mutation in the oorD gene involved in oxygen metabolism; and (iii) the presence of an uncommon insertion of a 72 amino acid coding sequence upstream from dnaK, which is involved in stress resistance. Therefore, the atypical behavior of this strain under aerobic atmosphere may result from the combination of insertions and mutations. In addition, the comparison of mRNA transcript levels of several genes targeted through genome analysis suggests the modification of regulatory processes in this strain.

The impact of environmental conditions on Campylobacter jejuni survival in broiler faeces and litter

INTRODUCTION

Campylobacter jejuni is the leading bacterial food-borne pathogen within the European Union, and poultry meat is an important vehicle for its transmission to humans. However, there is limited knowledge about how this organism persists in broiler litter and faeces. The aim of this study was to assess the impact of a number of environmental parameters, such as temperature, humidity, and oxygen, on Campylobacter survival in both broiler litter and faeces.

MATERIALS AND METHODS

Used litter was collected from a Campylobacter-negative broiler house after final depopulation and fresh faeces were collected from transport crates. Samples were confirmed as Campylobacter negative according to modified ISO methods for veterinary samples. Both sample matrices were inoculated with 9 log10 CFU/ml C. jejuni and incubated under high (≥85%) and low (≤70%) relative humidity conditions at three different temperatures (20°C, 25°C, and 30°C) under both aerobic and microaerophilic atmospheres. Inoculated litter samples were then tested for Campylobacter concentrations at time zero and every 2 hours for 12 hours, while faecal samples were examined at time zero and every 24 hours for 120 hours. A two-tailed t-test assuming unequal variance was used to compare mean Campylobacter concentrations in samples under the various temperature, humidity, and atmospheric conditions.

RESULTS AND DISCUSSION

C. jejuni survived significantly longer (P≤0.01) in faeces, with a minimum survival time of 48 hours, compared with 4 hours in used broiler litter. C. jejuni survival was significantly enhanced at 20°C in all environmental conditions in both sample matrices tested compared with survival at 25°C and 30°C. In general, survival was greater in microaerophilic compared with aerobic conditions in both sample matrices. Humidity, at the levels examined, did not appear to significantly impact C. jejuni survival in any sample matrix. The persistence of Campylobacter in broiler litter and faeces under various environmental conditions has implications for farm litter management, hygiene, and disinfection practices.

Description of Campylobacter jejuni Bf, an atypical aero-tolerant strain

BACKGROUND

Campylobacter jejuni is a leading cause of bacterial enteritis worldwide. This microaerophilic bacterium can survive in aerobic environments, suggesting it has protective mechanisms against oxidative stress. The clinical C. jejuni Bf strain is characterized by an increased resistance to oxygen. This study aimed to characterize the behavior of the clinical C. jejuni Bf strain under an aerobic atmosphere and in response to ROS-promoter agents.

METHODS

Growth was studied in both aerobic and microaerobic conditions using classic cultivable methods. Electronic microscopy and mreB gene expression were used to evaluate the morphology of this strain under aerobic conditions. The survival under oxidative stress was tested in the presence of different concentrations of hydrogen peroxide (H2O2) and paraquat (PQ).

RESULTS

The results showed that C. jejuni Bf strain can grow aerobically, unlike other strains of C. jejuni tested. Cells of C. jejuni Bf exposed to oxidative stress presented changes in morphology and the gene mreB, responsible for maintaining the bacillary cell morphology, was down-expressed. In aerobically acclimated conditions, C. jejuni Bf exhibited a higher survival rate of 52 % in the presence of H2O2 (1 mM) compared to the reference strain NCTC 11168. Concentrations above 1 mM PQ were lethal for the reference strain but not for C. jejuni Bf.

CONCLUSIONS

Taken together, these data highlight the resistance to oxidative stress conditions of C. jejuni Bf, indicating that this microorganism seems more adapted to survival in hostile environmental conditions.

High-Frequency Variation of Purine Biosynthesis Genes Is a Mechanism of Success in Campylobacter jejuni

Phenotypic variation is prevalent in the zoonotic pathogen Campylobacter jejuni, the leading agent of enterocolitis in the developed world. Heterogeneity enhances the survival and adaptive malleability of bacterial populations because variable phenotypes may allow some cells to be protected against future stress. Exposure to hyperosmotic stress previously revealed prevalent differences in growth between C. jejuni strain 81-176 colonies due to resistant or sensitive phenotypes, and these isolated colonies continued to produce progeny with differential phenotypes. In this study, whole-genome sequencing of isolated colonies identified allelic variants of two purine biosynthesis genes, purF and apt, encoding phosphoribosyltransferases that utilize a shared substrate. Genetic analyses determined that purF was essential for fitness, while apt was critical. Traditional and high-depth amplicon-sequencing analyses confirmed extensive intrapopulation genetic variation of purF and apt that resulted in viable strains bearing alleles with in-frame insertion duplications, deletions, or missense polymorphisms. Different purF and apt alleles were associated with various stress survival capabilities under several niche-relevant conditions and contributed to differential intracellular survival in an epithelial cell infection model. Amplicon sequencing revealed that intracellular survival selected for stress-fit purF and apt alleles, as did exposure to oxygen and hyperosmotic stress. Putative protein recognition direct repeat sequences were identified in purF and apt, and a DNA-protein affinity screen captured a predicted exonuclease that promoted the global spontaneous mutation rate. This work illustrates the adaptive properties of high-frequency genetic variation in two housekeeping genes, which influences C. jejuni survival under stress and promotes its success as a pathogen.

IMPORTANCE

C. jejuni is an important cause of bacterial diarrheal illness. Bacterial populations have many strategies for stress survival, but phenotypic variation due to genetic diversity has a powerful advantage: no matter how swift the change in environment, a fraction of the population already expresses the survival trait. Nonclonality is thus increasingly viewed as a mechanism of population success. Our previous work identified prominent resistant/sensitive colonial variation in C. jejuni bacteria in response to hyperosmotic stress; in the work presented here, we attribute that to high-frequency genetic variation in two purine biosynthesis genes, purF and apt. We demonstrated selective pressure for nonlethal mutant alleles of both genes, showed that single-cell variants had the capacity to give rise to diverse purF and apt populations, and determined that stress exposure selected for desirable alleles. Thus, a novel C. jejuni adaptive strategy was identified, which was, unusually, reliant on prevalent genetic variation in two housekeeping genes.

Putative mechanisms and biological role of coccoid form formation in Campylobacter jejuni

In certain conditions Campylobacter jejuni cells are capable of changing their cell shape from a typically spiral to a coccoid form (CF). By similarity to other bacteria, the latter was initially considered to be a viable but non-culturable form capable of survival in unfavourable conditions. However, subsequent studies with C. jejuni and closely related bacteria Helicobacter pylori suggested that CF represents a non-viable, degenerative form. Until now, the issue on whether the CF of C. jejuni is viable and infective is highly controversial. Despite some preliminary experiments on characterization of CF cells, neither biochemical mechanisms nor genetic determinants involved in C. jejuni cell shape changes have been characterized. In this review, we highlight known molecular mechanisms and genes involved in CF formation in other bacteria. Since orthologous genes are also present in C. jejuni, we suggest that CF formation in these bacteria is also a regulated and genetically determined process. A possible significance of CF in the lifestyle of this important bacterial pathogen is discussed.

Survival of poultry-derived Campylobacter jejuni of multilocus sequence type clonal complexes 21 and 45 under freeze, chill, oxidative, acid and heat stresses

The application of multilocus sequence typing (MLST) for studying Campylobacter jejuni diversity reveals that MLST clonal complex (CC) 21 and CC-45 occupies significant proportion in the diverse population of C. jejuni. These two complexes are ecologically abundant and represent an interesting subpopulation for studying C. jejuni survival under different stress conditions. In the present study we characterize and compare 19 C. jejuni strains assigned to CC-21 and CC-45, isolated from chicken meat, based on laboratory stress models maintained in Muller-Hinton broth. Model conditions were mimicking freeze, chill, oxidative, acid and heat stresses. Results show that survival patterns varied between the strains. C. jejuni strains of CC-21 survived significantly better than C. jejuni strains of CC-45 under heat (P value = 0.022) and chill (P value = 0.001) stress models. On the other hand, C. jejuni strains of CC-45 showed significantly better survival compared to C. jejuni strains of CC-21 in response to oxidative (P value = 0.003) and freeze (P value = 0.021) stress models. C. jejuni strains assigned to the founder ST-45 showed significantly better survival (P value = 0.017) under heat stress model compared to their ancestral sequence types. However, an association between survival fitness and the diversification of a clonal group cannot be demonstrated directly from the obtained results. In conclusion, findings of the present study show that genotypic variations of C. jejuni might play a role in enabling certain lineages to be selected when encountering adverse and stressful environments. In future stress response studies, it is recommended to consider the effect of genotypic diversity among C. jejuni strains as that might bias the experimental findings.

Adhesion ability of Campylobacter jejuni to Ht-29 cells increases with the augmentation of oxidant agent concentration

Campylobacter jejuni (C. jejuni) is a leading cause of human enteritis worldwide and the most frequently reported zoonotic agent in the European Union. Despite the fact that C. jejuni is a microaerobic bacteria, known as a fragile one, it is able to survive through adverse conditions such as oxidative stress. The purpose of this study was first to test the oxidative stress resistance in 22 C. jejuni strains of various origins, and to compare adhesive and invasive abilities of four selected strains in the intestinal cell line Ht-29. Secondly, the effect of an oxidative stress on C. jejuni adhesion to Ht-29 cells was investigated. Results show that all the tested strains were able to survive after a 24-h incubation period in broth containing 10 μM of paraquat. From 12.5 μM of paraquat, bacterial strains exhibit different behaviour, and only three strains are able to survive at 25 μM of paraquat. In addition, this study revealed that the number of bound bacteria to epithelial cells increases with augmentation of paraquat concentration, suggesting a link between oxidative stress survival of C. jejuni and virulence on Ht-29 cells.

Long-term survival of Campylobacter jejuni at low temperatures is dependent on polynucleotide phosphorylase activity

Campylobacter jejuni is a leading cause of bacterial gastroenteritis worldwide. Infection generally occurs after ingestion of contaminated poultry products, usually conserved at low temperatures. The mechanisms promoting survival of C. jejuni in the cold remain poorly understood despite several investigations. The present study provides insight into the survival mechanism by establishing the involvement of polynucleotide phosphorylase (PNPase), a 3'-5' exoribonuclease with multiple biological functions in cold survival. The role of PNPase was demonstrated genetically using strains with altered pnp genes (which encode PNPase) created in C. jejuni F38011 and C. jejuni 81-76 backgrounds. Survival assays carried out at low temperatures (4 and 10 degrees C) revealed a difference of 3 log CFU/ml between the wild-type and the pnp deletion (Deltapnp) strains. This did not result from a general requirement for PNPase because survival rates of the strains were similar at higher growth temperatures (37 or 42 degrees C). trans-Complementation with plasmid pNH04 carrying the pnp gene under the control of its natural promoter restored the cold survival phenotype to the pnp deletion strains (at 4 and 10 degrees C) but not to the same level as the wild type. In this study we demonstrate the role of PNPase in low-temperature survival of C. jejuni and therefore attribute a novel biological function to PNPase directly related to human health.

Pyruvate relieves the necessity of high induction levels of catalase and enables Campylobacter jejuni to grow under fully aerobic conditions

AIMS

Several cases of campylobacteriosis reported worldwide seemingly conflict with the strict growth requirements and sensitivity to environmental stress of Campylobacter jejuni. In this study, the need for a micro-aerobic environment [dissolved oxygen tension (DOT): 0.1-90%; 100% air saturation)] and the adaptive responses to oxygen stress were studied.

METHODS AND RESULTS

The growth of C. jejuni in continuous culture was assessed under different DOT in the presence or absence of pyruvate. In a medium without pyruvate, continuous cultures of C. jejuni showed typically micro-aerobic behaviour and cells were unable to grow under fully aerobic conditions. However in the presence of pyruvate (25 mmol l(-1)), continuous cultures of C. jejuni were able to grow in a broad DOT range, varying from 0.1% to at least 90%, and the catalase activity was decreased.

CONCLUSIONS

Addition of pyruvate results in the decrease in the concentration of hydrogen peroxide, which enables C. jejuni to grow aerobically.

SIGNIFICANCE AND IMPACT OF THE STUDY

New information on the oxidative physiology of C. jejuni and its ability to grow aerobically in media supplemented with pyruvate is presented.

Morphological and physiological responses of Campylobacter jejuni to stress

Under conditions of stress, cells of Campylobacter assume a coccoid shape that may be an evolutionary strategy evolved by the organism to enable survival between hosts. However, the physiology of Campylobacter as it devolves from spiral to coccoid-shaped morphology is poorly understood. In this study, conditions influencing the survival of Campylobacter jejuni ATCC 35921 in broth were determined. Cells in late log phase were resuspended in broth at 4 or 60 degrees C. The culturability of these cold- or heat-stressed cell suspensions was determined by spread plate counts and the activity of cells by the direct viable count technique and 5-cyano-2,3-ditolyltetrazolium chloride staining. C. jejuni changed form completely from culturable to viable but nonculturable cells (VBNC) within 25 days at 4 degrees C, and 15 min at 60 degrees C. Light microscopy of C. jejuni VBNC cells showed that the spiral-shaped cells became coccoid, and transmission electron microscopy of C. jejuni VBNC cells showed that the outer membrane was lost in aging cell suspensions. Furthermore, a limited proteomic study was carried out to compare C. jejuni proteins that exhibited increased or decreased synthesis on exposure to 60 degrees C.

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.

Survival of Campylobacter jejuni in water: effect of grazing by the freshwater crustacean Daphnia carinata (Cladocera)

Environmental studies of the human-pathogenic bacterium Campylobacter jejuni have focused on linking distributions with potential sources. However, in aquatic ecosystems, the abundance of C. jejuni may also be regulated by predation. We examine the potential for grazing by the freshwater planktonic crustacean Daphnia carinata to reduce the survival of C. jejuni. We use a system for measuring grazing and clearance rates of D. carinata on bacteria and demonstrate that D. carinata can graze C. jejuni cells at a rate of 7% individual(-1) h(-1) under simulated natural conditions in the presence of an algal food source. We show that passage of C. jejuni through the Daphnia gut and incorporation into fecal material effectively reduces survival of C. jejuni. This is the first evidence to suggest that grazing by planktonic organisms can reduce the abundance of C. jejuni in natural waters. Biomanipulation of planktonic food webs to enhance Daphnia densities offers potential for reducing microbial pathogen densities in drinking water reservoirs and recreational water bodies, thereby reducing the risk of contracting water-borne disease.

Survival of cold-stressed Campylobacter jejuni on ground chicken and chicken skin during frozen storage

Campylobacter jejuni is prevalent in poultry, but the effect of combined refrigerated and frozen storage on its survival, conditions relevant to poultry processing and storage, has not been evaluated. Therefore, the effects of refrigeration at 4 degrees C, freezing at -20 degrees C, and a combination of refrigeration and freezing on the survival of C. jejuni in ground chicken and on chicken skin were examined. Samples were enumerated using tryptic soy agar containing sheep's blood and modified cefoperazone charcoal deoxycholate agar. Refrigerated storage alone for 3 to 7 days produced a reduction in cell counts of 0.34 to 0.81 log10 CFU/g in ground chicken and a reduction in cell counts of 0.31 to 0.63 log10 CFU/g on chicken skin. Declines were comparable for each sample type using either plating medium. Frozen storage, alone and with prerefrigeration, produced a reduction in cell counts of 0.56 to 1.57 log10 CFU/g in ground chicken and a reduction in cell counts of 1.38 to 3.39 log10 CFU/g on chicken skin over a 2-week period. The recovery of C. jejuni following freezing was similar on both plating media. The survival following frozen storage was greater in ground chicken than on chicken skin with or without prerefrigeration. Cell counts after freezing were lower on chicken skin samples that had been prerefrigerated for 7 days than in those that had been prerefrigerated for 0, 1, or 3 days. This was not observed for ground chicken samples, possibly due to their composition. C. jejuni survived storage at 4 and -20 degrees C with either sample type. This study indicates that, individually or in combination, refrigeration and freezing are not a substitute for safe handling and proper cooking of poultry.

Estimating potential environmental loadings of Cryptosporidium spp. and Campylobacter spp. from livestock in the Grand River Watershed, Ontario, Canada

Exposure to waterborne pathogens in recreational or drinking water is a serious public health concern. Thus, it is important to determine the sources of pathogens in a watershed and to quantify their environmental loadings. The natural variability of potentially pathogenic microorganisms in the environment from anthropogenic, natural, and livestock sources is large and has been difficult to quantify. A first step in characterizing the risk of nonpoint source contamination from pathogens of livestock origin is to determine the potential environmental loading based on animal prevalence and fecal shedding intensity. This study developed a probabilistic model for estimating the production of Cryptosporidium spp. and Campylobacter spp. from livestock sources within a watershed. Probability density functions representing daily pathogen production rates from livestock were simulated for the Grand River Watershed in southwestern Ontario. The prevalence of pathogenic microorganisms in animals was modeled as a mixture of beta-distributions with parameters drawn from published studies. Similarly, gamma-distributions were generated to describe animal pathogen shedding intensity. Results demonstrate that although cattle are responsible for the largest amount of manure produced, other domesticated farm animals contribute large numbers of the two pathogenic microorganisms studied. Daily pathogen production rates are highly sensitive to the parameters of the gamma-distributions, illustrating the need for reliable data on animal shedding intensity. The methodology may be used for identifying source terms for pathogen fate and transport modeling and for defining and targeting regions that are most vulnerable to water contamination from pathogenic sources.

Effectiveness of chemical sanitizers against Campylobacter jejuni-containing biofilms

Survival of Campylobacter jejuni in mixed-culture biofilms was determined after treatment with chemical sanitizers including chlorine, quaternary ammonia, peracetic acid (PAA), and a PAA/peroctanoic acid mixture (PAA/POA). Biofilm-producing bacteria (gram-positive rods, Y1 and W1) were isolated from chicken house nipple drinkers. A meat plant isolate (Pseudomonas sp.) was also included as a biofilm producer. Two-day-old biofilms grown on polyvinyl chloride (PVC) plastic coupons in R2A broth at 12 degrees C were incubated with 10(6) CFU/ml C jejuni for 6 h to allow attachment. The coupons were then rinsed and incubated in fresh media for an additional 24 h. C. jejuni-containing biofilms were detached by vortexing with glass beads in modified brucella broth, which was then enumerated for C. jejuni on selective/differential media. The presence of biofilm enhanced (P < 0.01) the attachment and survival of C. jejuni After the 24-h incubation, only 20 CFU/cm2 of C. jejuni were recovered from the control without biofilms compared to 2,500 to 5,000 CFU/cm2 in samples with preexisting biofilms. The presence of biofilm microflora decreased (P < 0.01) the effectiveness of sanitizers against C. jejuni. Chlorine was the most effective sanitizer since it completely inactivated C. jejuni in the biofilms after treatment at 50 ppm for 45 s. C. jejuni in biofilms was susceptible to all sanitizers tested but was not completely inactivated by treatment with quaternary ammonia, PAA, or PAA/POA mixture at 50 and 200 ppm for 45 s.

Validation of a polymerase chain reaction/restriction enzyme analysis method for species identification of thermophilic campylobacters isolated from domestic and wild animals

AIMS

To compare and evaluate a polymerase chain reaction/restriction enzyme analysis (PCR/REA) method with standard phenotypic tests for the identification and differentiation of the thermophilic campylobacters Campylobacter jejuni, C. coli, C. lari and C. upsaliensis.

METHODS AND RESULTS

One hundred and eighty-two presumptive thermophilic campylobacters from 12 different animal species were tested by a recently published PCR/REA and standard phenotypic tests. By PCR/REA, 95% of the isolates were clearly identified as either one of the four thermophilic Campylobacter species or as not belonging to this group of organisms at all. By standard phenotyping, 174 of the 182 isolates were initially identified as either C. jejuni, C. coli, C. lari or C. upsaliensis. Additional genotypic tests and phenotyping showed that 52 of these identifications were either incorrect or unreliable. Of the C. jejuni isolates, 19% were identified as C. coli by initial phenotyping and 27 sheep isolates phenotyped as C. coli or C. lari were, in fact, arcobacters.

CONCLUSIONS

The PCR/REA was more reliable than standard phenotyping for the identification of thermophilic campylobacters from different animals.

SIGNIFICANCE AND IMPACT OF THE STUDY

Routinely used phenotypic tests often resulted in unreliable identifications, requiring additional testing. The PCR/REA, however, gave unequivocal results and was considered useful for the routine identification of thermophilic campylobacters from different animals.