High-resolution genomic fingerprinting of Campylobacter jejuni and Campylobacter coli by analysis of amplified fragment length polymorphisms

Knowledge gaps in control of Campylobacter for prevention of campylobacteriosis

Campylobacteriosis is an important, worldwide public health problem with numerous socio-economic impacts. Since 2015, approximately 230,000 cases have been reported annually in Europe. In the United States, Australia and New Zealand, campylobacteriosis is the most commonly reported disease. Poultry and poultry products are considered important sources of human infections. Poultry meat can become contaminated with Campylobacter during slaughter if live chickens are intestinal carriers. Campylobacter spp. can be transferred from animals to humans through consumption and handling of contaminated food products, with fresh chicken meat being the most commonly implicated food type. Regarding food-borne disease, the most important Campylobacter species are Campylobacter jejuni and Campylobacter coli. In humans, clinical signs of campylobacteriosis include diarrhoea, abdominal pain, fever, headache, nausea and vomiting. Most cases of campylobacteriosis are sporadic and self-limiting, but there are post-infection complications, for example, Guillain-Barrés syndrome. This review summarizes an analysis undertaken by the DISCONTOOLS group of experts on campylobacteriosis. Gaps were identified in: (i) knowledge of true number of infected humans; (ii) mechanisms of pathogenicity to induce infection in humans; (iii) training to prevent transfer of Campylobacter from raw to ready-to-eat food; (iv) development of effective vaccines; (v) understanding transmission routes to broiler flocks; (vi) knowledge of bacteriocins, bacteriophages and antimicrobial peptides as preventive therapies; (vii) ration formulation as an effective preventive measure at a farm level; (viii) development of kits for rapid detection and quantification of Campylobacter in animals and food products; and (ix) development of more effective antimicrobials for treatment of humans infected with Campylobacter. Some of these gaps are relevant worldwide, whereas others are more related to problems encountered with Campylobacter in industrialized countries.

Virulence characteristics of hcp (+) Campylobacter jejuni and Campylobacter coli isolates from retail chicken

Background

Recently the Type VI secretion system (T6SS), which can play a significant role in bacterial survival and pathogenesis, was reported in Campylobacter spp., having the hcp gene as a key component.

Methods

Campylobacteriosis is associated with the consumption of infected chicken meat. Our study aimed to explore the presence of T6SS in C. jejuni (n = 59) and C. coli (n = 57) isolates, from retail raw chicken and to investigate their pathogenic potential. The hcp gene was used as an indicator for the T6SS presence.

Results

Using multiplex PCR we have identified a significantly higher prevalence of hcp in C. coli isolates (56.1%) than in C. jejuni (28.8%) and AFLP analysis of the isolates showed a high degree of genetic similarity between the isolates carrying the hcp gene. Genome sequencing data showed that 84.3% of the C. coli and 93.7% of the C. jejuni isolates had all 13 T6SS open reading frames. Moreover, the virulence characteristics of hcp + isolates, including motility and the ability to invade human intestinal epithelial cells in vitro, were significantly greater than in the control strain C. jejuni 12502; a human isolate which is hcp positive.

Conclusion

Overall, it was discovered that hcp⁺C. coli and C. jejuni isolated from retail chicken isolates posses genetic and phenotypic properties associated with enhanced virulence. However, since human infections with C. coli are significantly less frequent than those of C. jejuni, the relationship between virulence factors and pathogenesis requires further study.

Development of a comparative genomic fingerprinting assay for rapid and high resolution genotyping of Arcobacter butzleri

Background

Molecular typing methods are critical for epidemiological investigations, facilitating disease outbreak detection and source identification. Study of the epidemiology of the emerging human pathogen Arcobacter butzleri is currently hampered by the lack of a subtyping method that is easily deployable in the context of routine epidemiological surveillance. In this study we describe a comparative genomic fingerprinting (CGF) method for high-resolution and high-throughput subtyping of A. butzleri. Comparative analysis of the genome sequences of eleven A. butzleri strains, including eight strains newly sequenced as part of this project, was employed to identify accessory genes suitable for generating unique genetic fingerprints for high-resolution subtyping based on gene presence or absence within a strain.

Results

A set of eighty-three accessory genes was used to examine the population structure of a dataset comprised of isolates from various sources, including human and non-human animals, sewage, and river water (n=156). A streamlined assay (CGF₄₀) based on a subset of 40 genes was subsequently developed through marker optimization. High levels of profile diversity (121 distinct profiles) were observed among the 156 isolates in the dataset, and a high Simpson’s Index of Diversity (ID) observed (ID > 0.969) indicate that the CGF₄₀ assay possesses high discriminatory power. At the same time, our observation that 115 isolates in this dataset could be assigned to 29 clades with a profile similarity of 90% or greater indicates that the method can be used to identify clades comprised of genetically similar isolates.

Conclusions

The CGF₄₀ assay described herein combines high resolution and repeatability with high throughput for the rapid characterization of A. butzleri strains. This assay will facilitate the study of the population structure and epidemiology of A. butzleri.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-015-0426-4) contains supplementary material, which is available to authorized users.

Genetic differentiation of Campylobacter jejuni

Genotyping methods have been developed and applied to differentiate Campylobacter jejuni isolates over the last two decades. Although a wealth of information was generated, the data are disappointingly complex and do not support simple models of transmission. Several observations have apparently weakened the value and complicated the interpretation of genotyping methods. For several methods, instability of genotype has been demonstrated, due to recombinations with or without transformation. C. jejuni is partly non-clonal, as demonstrated by multilocus sequence typing, which is explained by a natural ability to take up DNA. Plasticity of the genome, allowing for recombinations involving large DNA segments, and recombinations within loci frequently used for typing, further complicates the interpretation of typing data. The lack of clear-cut epidemiologic trends is probably not due to a lack of data or paucity of the used techniques, but is caused by the complex population genetics of the species.

Pulsed-field gel electrophoresis typing of Campylobacter fetus subsp. fetus from sheep abortions in the Hawke's Bay region of New Zealand

AIM

To type Campylobacter isolates from sheep abortions from the Hawke's Bay region of New Zealand.

METHODS

Campylobacter isolates were collected from aborted sheep fetuses from commercial farms in the Hawke's Bay region. Information on the Campylobacter vaccination status of flocks in the study was collected. Isolates were identified to species level using standard phenotypic tests, then typed using pulsed-field gel electrophoresis (PFGE).

RESULTS

Eighty-one C. fetus subsp. fetus isolates were cultured from aborted sheep fetuses from 25 farms and four C. jejuni isolates were cultured from fetuses from three farms. The C. fetus subsp. fetus isolates were classified into six PFGE groups. A single pulsed-field type predominated amongst isolates from 19 of the 25 farms. The C. jejuni isolates comprised two types.

CONCLUSIONS

A range of C. fetus subsp. fetus PFGE types was identified, and one type, B1, was found most frequently. Campylobacter fetus subsp. fetus was only isolated from samples from sheep that had not been vaccinated with C. fetus subsp. fetus vaccine that season.

Prevalence of Campylobacter and Salmonella in raw chicken on retail sale in the republic of Ireland

To assess the current risks to consumers from Campylobacter and Salmonella in raw chicken products sold in the Republic of Ireland, a retail survey was undertaken to define their prevalence. Samples (n = 510) were analyzed using protocols based on ISO 10272-1:2006 and ISO 6579:2002. Processor codes on pack labels showed that 67% of samples were produced in the Republic of Ireland and 25% in the United Kingdom. Salmonella was present in 5.1% of samples, but the eight serovars found caused less than 7% of human salmonellosis reported in the Republic of Ireland. The results suggest that on-farm controls to limit Salmonella infection of broilers have been successful and that in Ireland raw chicken is not a significant cause of salmonellosis in humans. The overall prevalence of Campylobacter spp. was 84.3%. Isolation by the ISO method found 52.7% of samples to be positive, but overgrowth by contaminants was frequently evident. Therefore, in addition to enrichment, an homogenized sample was plated directly onto modified charcoal cefoperazone deoxycholate agar, and this detected a further 31.6%. Speciation of isolates (n = 426) determined that 67% were Campylobacter jejuni and 32% were Campylobacter coli. These species are the most common cause of campylobacteriosis in man. The results indicate that there is a need for poultry producers to introduce interventions to minimize the exposure of consumers in the Republic of Ireland to Campylobacter spp., as has been successfully done for Salmonella.

Comparative genotypic and pathogenic examination of Campylobacter concisus isolates from diarrheic and non-diarrheic humans

Background

Campylobacter concisus is an emerging enteric pathogen, yet it is commonly isolated from feces and the oral cavities of healthy individuals. This genetically complex species is comprised of several distinct genomospecies which may vary in pathogenic potential.

Results

We compared pathogenic and genotypic properties of C. concisus fecal isolates from diarrheic and healthy humans residing in the same geographic region. Analysis of amplified fragment length polymorphism (AFLP) profiles delineated two main clusters. Isolates assigned to AFLP cluster 1 belonged to genomospecies A (based on genomospecies-specific differences in the 23S rRNA gene) and were predominantly isolated from healthy individuals. This cluster also contained a reference oral strain. Isolates assigned to this cluster induced greater expression of epithelial IL-8 mRNA and more frequently contained genes coding for the zonnula occludins toxin and the S-layer RTX. Furthermore, isolates from healthy individuals induced greater apoptotic DNA fragmentation and increased metabolic activity than those from diarrheic individuals, and isolates assigned to genomospecies A (of which the majority were from healthy individuals) exhibited higher haemolytic activity compared to genomospecies B isolates. In contrast, AFLP cluster 2 was predominated by isolates belonging to genomospecies B and those from diarrheic individuals. Isolates from this cluster displayed greater mean epithelial invasion and translocation than cluster 1 isolates.

Conclusion

Two main genetically distinct clusters (i.e., genomospecies) were identified among C. concisus fecal isolates from healthy and diarrheic individuals. Strains within these clusters differed with respect to clinical presentation and pathogenic properties, supporting the hypothesis that pathogenic potential varies between genomospecies. ALFP cluster 2 isolates were predominantly from diarrheic patients, and exhibited higher levels of epithelial invasion and translocation, consistent with known roles for these factors in diarrhoeal disease. Conversely, isolates from healthy humans and AFLP cluster 1 or genomospecies A (which were predominantly isolated from healthy humans) exhibited increased haemolytic ability, apoptotic DNA fragmentation, IL-8 induction, and/or carriage of toxin genes. Given that this cluster contains an oral reference strain, it is possible that some of the AFLP cluster 1 isolates are periodontal pathogens and may cause disease, albeit via a different mechanism than those from AFLP cluster 2.

Prevalence of Campylobacter spp. in raw retail poultry on sale in Northern Ireland

A year-long survey of fresh, retail poultry products on sale in Northern Ireland was undertaken to define the prevalence of Campylobacter spp. by using protocols based on ISO (standard) 10272-1:2006. Incubation at 37 and 42 degrees C was undertaken to increase the diversity of isolates obtained. Overall, 652 isolates were identified as Campylobacter spp. by using PCR and amplified fragment length polymorphic typing. Phenotyping wrongly identified 21% of isolates. Prevalences of Campylobacter found were chicken, 91% (n = 336); turkey, 56% (n = 77); and duck, 100% (n = 17). Prevalence rates for chicken produced in Northern Ireland, Scotland, England, and Wales were similar, with a mean value of 91%. The prevalences in product from the latter two countries were much higher than were found in two United Kingdom-wide surveys of chicken. The incubation temperature did not affect the relative proportions of the species isolated (P > 0.05). Campylobacter jejuni composed 64.6% of isolates, Campylobacter coli, 27.4%, and Campylobacter lari, 1%. Most cases of human campylobacteriosis are caused by C. jejuni and C. coli. The overall Campylobacter prevalence results are consistent with Northern Ireland surveys undertaken since 2000, and indicate that United Kingdom strategies to control Campylobacter in chicken have not had a significant effecton the prevalence of this pathogen in retail products on sale in Northern Ireland.

Multilocus sequence typing for investigation of diversity of Campylobacter jejuni strains from humans and environment in Norway

This report describes the use of the Multilocus Sequence Typing (MLST) method for typing 32 strains previously identified as Campylobacter jejuni. This system identified a great diversity between the investigated strains. The majority of strains belonged to already existing alleles found on the Campylobacter MLST home page, and most of them represented clonal complexes ST-21 and ST-45, but there were some newly identified alleles as well.

A large waterborne outbreak of campylobacteriosis in Norway: the need to focus on distribution system safety

Background

On 7 May 2007 the medical officer in Røros (population 5600) reported 15 patients with gastroenteritis. Three days later he estimated hundreds being ill. Untreated tap water from a groundwater source was suspected as the vehicle and chlorination was started 11 May. Campylobacter was isolated from patients' stool samples. We conducted an investigation to identify the source and describe the extent of the outbreak.

Methods

We undertook a retrospective cohort study among a random sample of customers of Røros and neighbouring Holtålen waterworks. Holtålen, which has a different water source, was used as a control city. We conducted telephone interviews to gather data on illness from all household members. One randomly selected household member was asked about detailed exposure history. The regional hospital laboratory tested patients' stools for enteropathogens. Campylobacter isolates were typed by AFLP for genetic similarity at the Norwegian Institute of Public Health. Local authorities conducted the environmental investigation.

Results

We identified 105 cases among 340 individuals from Røros and Holtålen (Attack Rate = 31%). Tap water consumption was the only exposure associated with illness. Among randomly selected household members from Røros, a dose-response relationship was observed in daily consumed glasses of tap water (χ² for trend = 8.1, p = 0.004). Campylobacter with identical AFLP was isolated from 25 out of 26 submitted stool samples. No pathogens were detected in water samples. We identified several events that might have caused pressure fall and influx of contaminated water into the water distribution system. On two occasions, pressure fall was noticed and parts of the distribution system were outdated.

Conclusion

The investigation confirmed a waterborne outbreak of campylobacteriosis in Røros. Although no single event was identified as the cause of contamination, this outbreak illustrates the vulnerability of water distribution systems. Good quality source water alone is not enough to ensure water safety. For a better risk management, more focus should be put on the distribution system security. Waterworks personnel should monitor the pressure regularly; reduce the leakage by upgrading the distribution network and use chlorination when conducting maintenance work.

Isolation and characterization of Helicobacter suis sp. nov. from pig stomachs

A new cultivation method was successfully applied for the in vitro isolation of a hitherto uncultured spiral Helicobacter species associated with ulceration of the non-glandular stomach and gastritis in pigs and formerly described as 'Candidatus Helicobacter suis'. Three isolates, HS1(T), HS2 and HS3, were subcultured from the stomach mucosa of three pigs after slaughter and were analysed using a polyphasic taxonomic approach. The novel isolates grew on biphasic culture plates or very moist agar bases in microaerobic conditions and exhibited urease, oxidase and catalase activities. Sequencing of the 16S rRNA gene, the 23S rRNA gene, the partial hsp60 gene and partial ureAB genes confirmed that the strains present in the gastric mucosa of pigs constituted a separate taxon, corresponding to 'Helicobacter heilmannii' type 1 strains as detected in the gastric mucosa of humans and other primates. For all genes sequenced, the highest sequence similarities were obtained with Helicobacter felis, Helicobacter bizzozeronii and Helicobacter salomonis, Helicobacter species isolated from the gastric mucosa of dogs and cats, which have also been detected in the human gastric mucosa and which are commonly referred to as 'Helicobacter heilmannii' type 2. SDS-PAGE of whole-cell proteins of strains HS1(T), HS2 and HS3 differentiated them from other Helicobacter species of gastric origin. The results of the polyphasic taxonomic analysis confirmed that the novel isolates constitute a novel taxon corresponding to 'Helicobacter heilmannii' type 1 strains from humans and to 'Candidatus H. suis' from pigs. The name Helicobacter suis sp. nov. is proposed for the novel isolates with the type strain HS1(T) (=LMG 23995(T)=DSM 19735(T)).

Campylobacter canadensis sp. nov., from captive whooping cranes in Canada

Ten isolates of an unknown Campylobacter species were isolated from cloacal swabs obtained from captive adult whooping cranes (Grus americana). All isolates were identified as Campylobacter based on generic PCR and grouped with other Campylobacter species based on 23S rRNA gene sequence. None of the isolates could be identified by species-specific PCR for known taxa, and all ten isolates formed a robust clade that was very distinct from known Campylobacter species based on 16S rRNA, rpoB and cpn60 gene sequences. The results of 16S rRNA gene nucleotide sequence (<or=92% sequence similarity to recognized Campylobacter species) and genomic DNA (no detectable relatedness) analyses were consistent with novel species status. Cells of the Campylobacter from whooping cranes were uniflagellar and typically sigmoid to allantoid in shape (0.48 microm wide and 2.61 microm long), but also spheroid to coccoid (0.59 microm wide and 0.73 microm long). The bacterium was oxidase-positive, able to reduce nitrite, able to grow at 3 degrees and 42 degrees C, and grew anaerobically, as well as in an atmosphere devoid of H2, and on MacConkey agar. It was not alpha-haemolytic and was negative for hippurate and indoxyl acetate hydrolysis and alkaline phosphatase. It also was susceptible to cephalotin and was unable to grow on nutrient agar, on a medium containing 3.5% NaCl or in ambient O2. The bacterium was unable to grow at 25 degrees C and growth was negative or very restricted at 30 degrees C. Fluorescent amplified fragment length polymorphism analysis indicated that nine of the recovered isolates were genetically distinct. A species-specific primer set targeting the cpn60 gene was developed. The name Campylobacter canadensis sp. nov. is proposed for the novel species, with the type strain L266T (=CCUG 54429T=LMG 24001T).

Species diversity of campylobacteria in a wild bird community in Sweden

AIMS

To analyse the occurrence and host species distribution of campylobacteria species in shorebirds, geese and cattle on grazed coastal meadows in Sweden.

METHODS AND RESULTS

Species identification was performed through a polyphasic approach, incorporating Amplified Fragment Length Polymorphism (AFLP) profiling, 16S RNA gene sequence analysis together with extensive phenotypic characterization. From 247 sampled birds and 71 cattle, we retrieved 113 urease positive thermophilic Campylobacter (UPTC) and 16 Campylobacter jejuni ssp. jejuni isolates. Furthermore, 18 isolates of Helicobacter canadensis, and five isolates that potentially represent a new genus of micro-aerophilic, spiral and Gram-negative bacteria were isolated. The distribution of bacterial species on hosts was uneven: all H. canadensis isolates were retrieved from geese, while all but one of the Campylobacter lari UPTC isolates were found in shorebirds. AFLP type distribution of Camp. lari UPTC isolates among individual, resampled and breeding-paired Redshank birds generally indicated a constant shift in strain populations over time and absence of geographical clustering.

CONCLUSIONS

The large number of isolated campylobacteria, including species that are zoonotic enteropathogens, indicates that these wild birds potentially may serve as reservoirs of human infections. However, despite a common environment, the different host species largely carried their own campylobacteria populations, indicating that cross-species transmission is rare.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our study is one of few that provide data on the occurrence of campylobacteria in wild animals, adding information on the ecology and epidemiology of micro-organisms that are of public health concern.

Comparison of virulence-associated in vitro properties of typed strains of Campylobacter jejuni from different sources

Campylobacter jejuni is a major cause of human diarrhoeal disease, but specific virulence mechanisms have not been well defined. This blinded study was undertaken with 40 C. jejuni isolates from different sources to determine their haemolytic, cytotoxic and adhesion and invasion activities towards mammalian cells. The results were correlated with source of isolation and genetic makeup by amplified fragment length polymorphism (AFLP) typing. The isolates had variable degrees of haemolytic activity against rabbit erythrocytes and cytotoxicity towards CaCo-2, HeLa and Vero cells. The data indicated that the haemolytic and cytotoxic activities were due to separate factors. A range of cytotoxicity was exhibited, whereby some strains had no activity against the target cells and others had activity against all three cell lines. Certain strains had activity against CaCo-2 cells but little or no activity against the other cells, while others exhibited the opposite phenotype. The data suggested that the cytotoxicity assay with the different cell lines may have detected more than one cytotoxin. A wide variation between isolates was observed for both adherence and invasion with all three cell lines, yet, overall, the strains showed a significantly greater invasion capacity for CaCo-2. There was no clear relationship between source of isolation or disease manifestation and possession of statistically significantly higher levels of particular virulence-associated factors although, in some cases, a correlation between cytotoxicity and cell invasion was evident. Five AFLP clusters, each representing two to eleven isolates with similar profiles, were observed at the 90 % similarity level. Some AFLP groups contained isolates with a common serotype, but each group had C. jejuni isolates from more than one source with the exception of group IV, which contained only human isolates. Isolates with high cytotoxic activity against CaCo-2 cells were confined to groups I, III and IV and a group of unrelated strains (U). Group II isolates had uniformly low cytotoxicity. Isolates in groups I, V and U were more invasive for CaCo-2 cells than isolates in groups II, III and IV. The strain differences in cytotoxicity or invasion did not correlate with source of isolation.

Novel Campylobacter isolation method using hydrophobic grid membrane filter and semisolid medium

Culture procedures for isolation of thermophilic campylobacters from food matrices are complex, labor intensive, and time-consuming. Most available methods include the use of antibiotics as selective agents to prevent the growth of competing microflora. A simple procedure for isolation of thermophilic campylobacters after enrichment in Rosef's enrichment broth was developed using a hydrophobic grid membrane filter (HGMF) on semisolid medium (SSM). SSM contains no antibiotics, and the HGMF physically separates Campylobacter from the enrichment broth, allowing isolation based on differential motility. The HGMF-SSM method was compared to the Agriculture and Agri-Food Canada Food Safety Procedures Manual (FSPM-10) method (Isolation of Thermophilic Campylobacters from Fresh Pork, Beef Veal, Poultry and Ready-to-Eat Meat Products), which includes the use of selective antibiotics. During the initial study, after enrichment the HGMF-SSM method yielded pure cultures of campylobacters after 16 to 18 h (overnight) compared with 48 h for the FSPM-10 method. Ninety-four turkey samples collected at local retail stores and 38 frozen pig fecal samples were processed by both methods. Thirty-five samples (26.5%) were positive by the HGMF-SSM method; 24 (18.2%) of these positive samples contained Campylobacter jejuni and 11 (8.3%) contained Campylobacter coli. With the FSPM-10 method, 25 samples (18.9%) were positive: 21 (15.9%) with C. jejuni and 4 (3%) with C. coli. For a subsequent field study, only the HGMF-SSM method was used to isolate Campylobacter from 1,200 chicken samples and 454 turkey samples sold at retail. Analysis of five subisolates from various samples indicated that only one type of Campylobacter was recovered by the HGMF-SSM method, as ascertained by MICs for 10 antimicrobials, sequencing of the short variable region of the flaA gene, and fingerprinting based on amplified fragment length polymorphism. The absence of antibiotics in the SSM may explain the higher recovery of thermophilic campylobacters. The HGMF-SSM method resulted in improved isolation of campylobacters and is simpler, faster, cheaper, and less labor intensive than the FSPM-10 method. The recovery of one type of Campylobacter from the chicken samples may have important implications, particularly in epidemiological studies.

Campylobacter in waterfowl and aquatic environments: incidence and methods of detection

Campylobacters are emerging as one of the most significant causes of human infections worldwide, and the role that waterfowl and the aquatic environment have in the spread of disease is beginning to be elucidated. On a world scale campylobacters are possibly the major cause of gastrointestinal infections. Campylobacters are common commensals in the intestinal tract of many species of wild birds, including waterfowl. They are also widely distributed in aquatic environments where their origins may include waterfowl as well as sewage effluents and agricultural runoff. Campylobacters have marked seasonal trends. In temperate aquatic environments they peak during winter, whereas spring-summer is the peak period for human infection. Campylobacter species may survive, and remain potentially pathogenic, for long periods in aquatic environments. The utility of bacterial fecal indicators in predicting the presence of campylobacters in natural waters is questionable. Viable but nonculturable Campylobacter cells may occur, but whether they have any role in the generation of outbreaks of campylobacteriosis is unclear. The routine detection of Campylobacter spp. in avian feces and environmental waters largely relies on conventional culture methods, while the recognition of a particular species or strain is based on serotyping and increasingly on molecular methods. Thus, PCR combined with selective enrichment enhances the detection of campylobacters in water and feces, while DNA sequencing facilitates recognition of particular species and strains.

Helicobacter pullorum in chickens, Belgium

A total of 110 broilers from 11 flocks were tested for Helicobacter pullorum by polymerase chain reaction; positive samples were reexamined with a conventional isolation method. H. pullorum isolates were examined by amplified fragment length polymorphism (AFLP) fingerprinting for interstrain genetic diversity and relatedness. Sixteen isolates from cecal samples from 2 different flocks were obtained. AFLP analysis showed that these isolates and 4 additional isolates from a different flock clustered according to their origin, which indicates that H. pullorum colonization may occur with a single strain that disseminates throughout the flock. Strains isolated from different hosts or geographic sources displayed a distinctive pattern. H. pullorum is present in approximately one third of live chickens in Belgium and may represent a risk to human health.

Environmental survival mechanisms of the foodborne pathogen Campylobacter jejuni

Campylobacter spp. continue to be the greatest cause of bacterial gastrointestinal infections in humans worldwide. They encounter many stresses in the host intestinal tract, on foods and in the environment. However, in common with other enteric bacteria, they have developed survival mechanisms to overcome these stresses. Many of the survival mechanisms used by Campylobacter spp. differ from those used by other bacteria, such as Escherichia coli and Salmonella spp. This review summarizes the mechanisms by which Campylobacter spp. adapt to stress conditions and thereby increase their ability to survive on food and in the environment.

Amplified fragment length polymorphism, serotyping, and quinolone resistance of Campylobacter jejuni and Campylobacter coli strains from chicken-related samples and humans in Taiwan

The high-resolution genotyping method of amplified fragment length polymorphism (AFLP) analysis was used to study the genetic relationships between Campylobacter jejuni isolates from chicken-related samples (n = 32) and humans (n = 27) as well as between Campylobacter coli isolates from chicken-related samples (n = 27) and humans (n = 5). These isolates were collected between 1994 and 2003 in Taiwan. All C. jejuni and C. coli isolates showed highly heterogeneous fingerprints. C. jejuni isolates were separated in two distinct genetic clusters (A and B) at 40% genetic similarity and 42 different AFLP types at 90% similarity. However, three clusters at 40% genetic similarity and 33 different AFLP types at 90% similarity were observed in C. coli isolates. These results showed that AFLP analysis could be used to identify individual isolates of two Campylobacter species. Among C. jejuni isolates, the predominant AFLP type 1 was observed in five (7.9%) isolates, and types 5 and 12 in four (6.3%) isolates each. Cluster B consisted of 10 isolates, while the majority of isolates (n = 53) belonged to cluster A. In some AFLP types (1, 5, 12, 14 and 31), AFLP fingerprints of chicken-related isolates were closely related genetically to those of isolates from humans with gastroenteritis. The predominant serotypes in C. jejuni isolates were B:2 and Y:37. All isolates belonging to serotype O:19 grouped into one single AFLP type. Some chicken samples yielded multiple isolates of Campylobacter harboring simultaneously quinolone-resistant and quinolone-sensitive isolates attributed to the same species, or harboring C. jejuni and C. coli that have the characteristics of quinolone resistance.

Delineation of Campylobacter concisus genomospecies by amplified fragment length polymorphism analysis and correlation of results with clinical data

Campylobacter concisus has been as frequently isolated from human diarrhea as the important enteropathogen Campylobacter jejuni, but it also occurs in the feces of healthy individuals. The role of C. concisus in human disease has been difficult to determine, since the species comprises at least two phenotypically indistinguishable but genetically distinct taxa (i.e., genomospecies) that may vary in pathogenicity. We examined 62 C. concisus strains by amplified fragment length polymorphism (AFLP) profiling and correlated the results with clinical data. All C. concisus strains gave unique AFLP profiles, and numerical analysis of these data distributed the strains among four clusters. The clustering was of taxonomic significance: two clusters contained, respectively, the type strain (of oral origin) and a reference strain (from diarrhea) of each of the known genomospecies. Genomospecies 2 strains were more frequently isolated from immunocompetent patients and/or patients without concomitant infections that presented with fever, chronic diarrhea, and gut inflammation than was genomospecies 1, clustering with the type strain of oral origin. Bloody diarrhea was recorded only with C. concisus genomospecies 2 infections. We identified two additional C. concisus genomospecies: genomospecies 3 comprised a single strain from an immunocompetent patient, and genomospecies 4 contained five isolates from severely immunodeficient patients, i.e., organ transplantation recipients or those with hematological malignancies. All genomospecies 4 strains were of the same protein profile group and failed to react with a C. concisus species-specific PCR assay based on 23S rRNA gene sequences: the taxonomic position of this group requires closer investigation. Campylobacter concisus is genetically and taxonomically diverse and contains at least four distinct genomospecies that may exhibit differences in their spectra of virulence potential.

Identification and molecular epidemiology of Campylobacter coli isolates from human gastroenteritis, food, and animal sources by amplified fragment length polymorphism analysis and Penner serotyping

Campylobacter coli is an infrequently studied but important food-borne pathogen with a wide natural distribution. We investigated its molecular epidemiology by use of amplified fragment length polymorphism (AFLP)-based genotyping and Penner serotyping. Serotype reference strains and 177 Danish isolates of diverse origin identified by routine phenotyping as C. coli were examined. Molecular tools identified some 12% of field isolates as Campylobacter jejuni, emphasizing the need for improved identification methods in routine laboratories. Cluster analysis of AFLP profiles of 174 confirmed C. coli isolates revealed a difference in the distribution of isolates from pig and poultry (chicken, duck, turkey, and ostrich) species and indicated the various poultry species, but not pigs, to be likely sources of human C. coli infection. A poor correlation was observed between serotyping and AFLP profiling, suggesting that the former method has limited value in epidemiological studies of this species.

Extended multilocus sequence typing system for Campylobacter coli, C. lari, C. upsaliensis, and C. helveticus

A multilocus sequence typing (MLST) system has been reported previously for Campylobacter jejuni to both differentiate strains and identify clonal lineages. However, sequence variation at the MLST loci prevents its use for closely related Campylobacter species. We describe herein an expanded MLST method to include three clinically relevant Campylobacter species, C. coli, C. lari, and C. upsaliensis, and a fourth Campylobacter species, C. helveticus. The C. coli and C. helveticus methods use the same seven C. jejuni loci (aspA, atpA, glnA, gltA, glyA, pgm, and tkt); however, adk and pgi were substituted for aspA and gltA in C. lari and for gltA and pgm in C. upsaliensis. Multiple C. coli (n = 57), C. lari (n = 20), C. upsaliensis (n = 78), and C. helveticus (n = 9) isolates, representing both clinical and environmental sources, were typed. All four species were genetically diverse: the majority (> 80%) of the isolates had unique sequence types (STs). Using this method, mixed C. lari, C. upsaliensis, and C. helveticus isolates were identified; upon separation, each isolate was shown to contain two strains of the same species with distinct STs. Additionally, the expanded MLST method was able to detect potential lateral transfer events between C. jejuni and either C. coli or C. lari and between C. upsaliensis and C. helveticus. Thus, the expanded MLST method will prove useful in differentiating strains of five Campylobacter species, identifying mixed Campylobacter cultures, and detecting genetic exchange within the genus.

Phylogenetic analysis and PCR-restriction fragment length polymorphism identification of Campylobacter species based on partial groEL gene sequences

The phylogeny of 12 Campylobacter species and reference strains of Arcobacter butzleri and Helicobacter pylori was studied based on partial 593-bp groEL gene sequences. The topology of the phylogenetic neighbor-joining tree based on the groEL gene was similar to that of the tree based on the 16S rRNA gene. However, groEL was found to provide a better resolution for Campylobacter species, with lower interspecies sequence similarities (range, 65 to 94%) compared with those for the 16S rRNA gene (range, 90 to 99%) and high intraspecies sequence similarities (range, 95 to 100%; average, 99%). A new universal reverse primer that amplifies a 517-bp fragment of the groEL gene was developed and used for PCR-restriction fragment length polymorphism (PCR-RFLP) analysis of 68 strains representing 11 Campylobacter species as well as reference strains of A. butzlerii and H. pylori. Digestion with the AluI enzyme discriminated all Campylobacter species included in the study but showed more intraspecies diversity than digestion with the ApoI enzyme. A hippurate-negative variant of Campylobacter jejuni with a high level of groEL sequence similarity to both C. jejuni (96%) and C. coli (94%) gave a unique AluI profile and an ApoI profile identical to those of other C. jejuni strains. In conclusion, groEL gene sequencing and PCR-RFLP analysis are recommended as valuable tools for the identification of Campylobacter species.

Ribotyping characterisation of campylobacter isolates randomly collected from different sources in Italy

In this study the potential for using the automated PstI ribotyping as a primary library typing method to survey Campylobacter and for identification of two thermophilic Campylobacter jejuni and Campylobacter coli species was evaluated. A total of 158 isolates randomly collected in Italy from different sources were analyzed. A large percentage of chicken (28%), turkey (27%) and turkey meat (25%) isolates shared their ribotyping profiles (ribotypes) with those of humans, whereas the swine isolates had unique profiles. The identification results obtained by ribotyping corresponded to those collected by using a multiplex PCR protocol specifically designed for C. jejuni and C. coli detection. The comparison of the PstI ribotyping profiles obtained in this research with those of the isolates collected over time will facilitate determining the ribotypes that are more frequently transmitted to humans in comparison to those that are normally harboured only in animals, foods and in the environment.

The genome-sequenced variant of Campylobacter jejuni NCTC 11168 and the original clonal clinical isolate differ markedly in colonization, gene expression, and virulence-associated phenotypes

The genome sequence of the enteric bacterial pathogen Campylobacter jejuni NCTC 11168 (11168-GS) was published in 2000, providing a valuable resource for the identification of C. jejuni-specific colonization and virulence factors. Surprisingly, the 11168-GS clone was subsequently found to colonize 1-day-old chicks following oral challenge very poorly compared to other strains. In contrast, we have found that the original clinical isolate from which 11168-GS was derived, 11168-O, is an excellent colonizer of chicks. Other marked phenotypic differences were also identified: 11168-O invaded and translocated through tissue culture cells far more efficiently and rapidly than 11168-GS, was significantly more motile, and displayed a different morphology. Serotyping, multiple high-resolution molecular genotyping procedures, and subtractive hybridization did not yield observable genetic differences between the variants, suggesting that they are clonal. However, microarray transcriptional profiling of these strains under microaerobic and severely oxygen-limited conditions revealed dramatic expression differences for several gene families. Many of the differences were in respiration and metabolism genes and operons, suggesting that adaptation to different oxygen tensions may influence colonization potential. This correlates biologically with our observation that anaerobically priming 11168-GS or aerobically passaging 11168-O caused an increase or decrease, respectively, in colonization compared to the parent strain. Expression differences were also observed for several flagellar genes and other less well-characterized genes that may participate in motility. Targeted sequencing of the sigma factors revealed specific DNA differences undetected by the other genomic methods [corrected].

Comparative genotyping of Campylobacter jejuni by amplified fragment length polymorphism, multilocus sequence typing, and short repeat sequencing: strain diversity, host range, and recombination

Three molecular typing methods were used to study the relationships among 184 Campylobacter strains isolated from humans, cattle, and chickens. All strains were genotyped by amplified fragment length polymorphism (AFLP) analysis, multilocus sequence typing (MLST), and sequence analysis of a genomic region with short tandem repeats designated clustered regularly interspaced short palindromic repeats (CRISPRs). MLST and AFLP analysis yielded more than 100 different profiles and patterns, respectively. These multiple-locus typing methods resulted in similar genetic clustering, indicating that both are useful in disclosing genetic relationships between Campylobacter jejuni isolates. Group separation analysis of the AFLP analysis and MLST data revealed an unexpected association between cattle and human strains, suggesting a common source of infection. Analysis of the polymorphic CRISPR region carrying short repeats allowed about two-thirds of the typeable strains to be distinguished, similar to AFLP analysis and MLST. The three methods proved to be equally powerful in identifying strains from outbreaks of human campylobacteriosis. Analysis of the MLST data showed that intra- and interspecies recombination occurs frequently and that the role of recombination in sequence variation is 50 times greater than that of mutation. Examination of strains cultured from cecum swabs revealed that individual chickens harbored multiple Campylobacter strain types and that some genotypes were found in more than one chicken. We conclude that typing of Campylobacter strains is useful for identification of outbreaks but is probably not useful for source tracing and global epidemiology because of carriage of strains of multiple types and an extremely high diversity of strains in animals.

Evaluation of 11 PCR assays for species-level identification of Campylobacter jejuni and Campylobacter coli

We examined the sensitivity and specificity of 11 PCR assays described for the species identification of Campylobacter jejuni and Campylobacter coli by using 111 type, reference, and field strains of C. jejuni, C. coli, and Campylobacter lari. For six assays, an additional 21 type strains representing related Campylobacter, Arcobacter, and Helicobacter species were also included. PCR tests were initially established in the laboratory by optimizing conditions with respect to five type and reference strains of C. jejuni, C. coli, and C. lari. One PCR test for C. coli failed to give appropriate results during this initial setup phase and was not evaluated further. The remaining 10 assays were used to examine heated lysate and purified DNA templates as appropriate of well-characterized type, reference, and field strains of C. jejuni (n = 62), C. coli (n = 34), and C. lari (n = 15). The tests varied considerably in their sensitivity and specificity for their respective target species. No assay was found to be 100% sensitive and/or specific for all C. jejuni strains tested, but four assays for C. coli gave appropriate responses for all strains examined. Between one and six strains of C. jejuni gave amplicons in four of seven C. jejuni PCR tests only where purified DNA was used as the template; corresponding results were seen with one strain of C. coli in each of three assays for the latter species. Our findings indicate that a polyphasic strategy for PCR-based identification should be used to identify C. jejuni and C. coli strains. The data may assist laboratories in selecting assays suited for their needs and in designing evaluations of future PCR tests aimed to identify these species.

Comparison of 23S polymerase chain reaction-restriction fragment length polymorphism and amplified fragment length polymorphism techniques as typing systems for thermophilic campylobacters

In this study, we evaluated the combination of polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and amplified fragment length polymorphism (AFLP) molecular typing techniques for the analysis of thermophilic campylobacter species isolated from clinical and poultry samples. 23S PCR-RFLP analysis performed to fingerprint 69 strains exhibited an excellent level of typability. Eleven different types were defined at 100% linkage level following numerical analysis of band patterns. Differentiation of Campylobacter jejuni and Campylobacter coli at species level was achieved although no significant relationship could be observed between the profiles and the origin of the strains. Simplified AFLP analysis of the isolates disclosed the presence of 66 different banding patterns. The resulting dendrogram showed a high diversity among the strains studied. All the isolates were grouped within eight main types with a 69% homology degree among them. Differentiation at subspecies level was possible but no significant relationship could be observed between the AFLP profiles and the origin of the strains. When used in combination, 23S PCR-RFLP and single-enzyme AFLP methods can be applied to determine taxonomic and epidemiological relationships among thermophilic campylobacters.

Development and application of a new scheme for typing Campylobacter jejuni and Campylobacter coli by PCR-based restriction fragment length polymorphism analysis

A molecular typing approach for Campylobacter jejuni and Campylobacter coli was developed with restriction fragment length polymorphism analysis of a 9.6-kb PCR-amplified portion of the lipopolysaccharide gene cluster. Sixty-one Penner serotype reference strains were analyzed with this new genotyping scheme, and 32 genogroups were found. Eleven additional genogroups were obtained from 87 clinical C. jejuni strains tested. This molecular typing method shows a correlation with the Penner heat-stable serotyping method, a phenotypic typing method based on lipopolysaccharide structures that is often used as a "gold standard" for subtyping Campylobacter spp. This strong correlation suggests that the data obtained can be directly compared with epidemiological data collected in the past by classical serotyping of C. jejuni and C. coli. In contrast to the high percentage of nontypeability by phenotyping, this molecular typing method results in 100% typeability and provides a superior alternative to serotyping.

Detection of heat-stable antigens of Campylobacter jejuni and C. coli by direct agglutination and passive hemagglutination

The two serotyping schemes for the detection of heat-stable antigens of Campylobacter jejuni and Campylobacter coli use the same strains for antiserum production but differ in the detection systems used for identifying agglutination. The Penner method uses passive hemagglutination (PHA) while the Laboratory of Enteric Pathogens method uses the same antisera but in a whole-bacterial-cell direct agglutination (DA) protocol. C. jejuni produces a polysaccharide capsule, which is antigenic, and is the main component detected by the PHA method. The DA method will detect both capsule antigens and lipopolysaccharide (LPS) or lipooligosaccharide (LOS) surface antigens. Comparison of both methods by using a selection of isolates from human infection has shown a range of variation in agglutination specificity, reflecting the differences in antigens detected by the two methods. While 27.4% of the 416 C. jejuni isolates reacted with the antisera raised against the same type strains by either method, the majority showed a range of more complex relationships. None of the 37 C. coli isolates reacted with the same antiserum by both methods. Together the two schemes gave a total of 102 distinct combined serogroups for C. jejuni and 16 for C. coli. Thus, while some clonally related isolates share the same capsule and LOS or LPS antigens, other strains appear to have a common capsule antigen but differ in their LPS or LOS structures or vice versa.

Differentiation of Campylobacter species by AFLP fingerprinting

The fluorescent amplified fragment length polymorphism (AFLP) fingerprinting method was tested for its ability to identify and subtype the most important Campylobacter species found in veterinary infections. Sixty-nine reference strains and 19 clinical isolates of Campylobacter jejuni subsp. jejuni, Campylobacter jejuni subsp. doylei, Campylobacter upsaliensis, Campylobacter coli, Campylobacter lari, Campylobacter fetus subsp. fetus, C. fetus subsp. venerealis, Campylobacter hyointestinalis subsp. hyointestinalis, C. hyointestinalis subsp. lawsonii, Campylobacter mucosalis, Campylobacter helveticus and Campylobacter sputorum were subjected to analysis. The topology of the dendrogram obtained by numerical analysis of the AFLP profiles did not reflect the phylogenetic relationships as derived from 16S rDNA sequence comparison. However, except for C. lari, AFLP analysis grouped the strains that belonged to the same genomic species into distinct clusters. C. lari strains were separated into two distinct AFLP groups, which corresponded with nalidixic-acid-sensitive and -resistant variants of C. lari. These results correlated with data from whole-cell protein profiling. Within C. jejuni, C. hyointestinalis and C. fetus, strains could be identified at the subspecies level. AFLP analysis also allowed the subtyping of most species at the strain level. It is concluded that AFLP analysis is a valuable tool for concurrent identification of campylobacters at the species, subspecies and strain levels. In addition, the data confirm and extend previous reports showing that C. lari is a heterogeneous species that may comprise multiple taxa.

Whole genome comparison of Campylobacter jejuni human isolates using a low-cost microarray reveals extensive genetic diversity

Campylobacter jejuni is the leading cause of bacterial food-borne diarrhoeal disease throughout the world, and yet is still a poorly understood pathogen. Whole genome microarray comparisons of 11 C. jejuni strains of diverse origin identified genes in up to 30 NCTC 11168 loci ranging from 0.7 to 18.7 kb that are either absent or highly divergent in these isolates. Many of these regions are associated with the biosynthesis of surface structures including flagella, lipo-oligosaccharide, and the newly identified capsule. Other strain-variable genes of known function include those responsible for iron acquisition, DNA restriction/modification, and sialylation. In fact, at least 21% of genes in the sequenced strain appear dispensable as they are absent or highly divergent in one or more of the isolates tested, thus defining 1300 C. jejuni core genes. Such core genes contribute mainly to metabolic, biosynthetic, cellular, and regulatory processes, but many virulence determinants are also conserved. Comparison of the capsule biosynthesis locus revealed conservation of all the genes in this region in strains with the same Penner serotype as strain NCTC 11168. By contrast, between 5 and 17 NCTC 11168 genes in this region are either absent or highly divergent in strains of a different serotype from the sequenced strain, providing further evidence that the capsule accounts for Penner serotype specificity. These studies reveal extensive genetic diversity among C. jejuni strains and pave the way toward identifying correlates of pathogenicity and developing improved epidemiological tools for this problematic pathogen.

Evidence for a genetically stable strain of Campylobacter jejuni

The genetic stability of selected epidemiologically linked strains of Campylobacter jejuni during outbreak situations was investigated by using subtyping techniques. Strains isolated from geographically related chicken flock outbreaks in 1998 and from a human outbreak in 1981 were investigated. There was little similarity in the strains obtained from the different chicken flock outbreaks; however, the strains from each of three chicken outbreaks, including strains isolated from various environments, were identical as determined by fla typing, amplified fragment length polymorphism (AFLP) analysis, and pulsed-field gel electrophoresis, which confirmed the genetic stability of these strains during the short time courses of chicken flock outbreaks. The human outbreak samples were compared with strain 81116, which originated from the same outbreak but has since undergone innumerable laboratory passages. Two main AFLP profiles were recognized from this outbreak, which confirmed the serotyping results obtained at the time of the outbreak. The major type isolated from this outbreak (serotype P6:L6) was exemplified by strain 81116. Despite the long existence of strain 81116 as a laboratory strain, the AFLP profile of this strain was identical to the profiles of all the other historical P6:L6 strains from the outbreak, indicating that the genotype has remained stable for almost 20 years. Interestingly, the AFLP profiles of the P6:L6 group of strains from the human outbreak and the strains from one of the recent chicken outbreaks were also identical. This similarity suggests that some clones of C. jejuni remain genetically stable in completely different environments over long periods of time and considerable geographical distances.

Identification of taxonomic and epidemiological relationships among Campylobacter species by numerical analysis of AFLP profiles

Amplified fragment length polymorphism (AFLP)-based profiling was performed on 138 strains representing all named Campylobacter species and subspecies. Profiles of 15/16 species comprised 6 to greater than 100 fragments and were subjected to numerical analysis. The mean similarity of 48 duplicate, outbreak and/or 'identical' strain profiles exceeded 94%. Species were clearly distinguished at the 17.90% similarity (S-) level in the dendrogram. Subspecies of Campylobacter jejuni and Campylobacter hyointestinalis, and biovars of Campylobacter lari and Campylobacter sputorum were distinguished at higher S-levels. All outbreak or 'genetically identical' strains of C. jejuni subsp. jejuni, Campylobacter coli, C. hyointestinalis and C. sputorum clustered at S-levels >92% and were distinguished from unrelated strains. Numerical analysis of AFLP profiles is useful for concurrent identification of taxonomic and epidemiological relationships among most Campylobacter species.

Comparative fingerprinting analysis of Campylobacter jejuni subsp. jejuni strains by amplified-fragment length polymorphism genotyping

Amplified-fragment length polymorphism (AFLP) analysis with the endonucleases BglII and MfeI was used to genotype 91 Campylobacter jejuni subsp. jejuni strains from outbreaks and sporadic cases. AFLP-generated fragments were labeled with fluorescent dye and separated by capillary electrophoresis. The software packages GeneScan and GelCompar II were used to calculate AFLP pattern similarities and to investigate phylogenetic relationships among the genotyped strains. The AFLP method was compared with two additional DNA-based typing methods, pulsed-field gel electrophoresis (PFGE) using SmaI and restriction fragment length polymorphism analysis on PCR products (PCR-RFLP) of the flaA and flaB genes. We found that AFLP analysis of C. jejuni strains is a rapid method that offers better discriminatory power than do both PFGE and PCR-RFLP. AFLP and, to a lesser extent, PCR-RFLP could differentiate strains within the same PFGE profiles, which also makes PCR-RFLP an alternative to PFGE. We were able to clearly distinguish 9 of 10 recognized outbreaks by AFLP and to identify similarities among outbreak and sporadic strains. Therefore, AFLP is suitable for epidemiological surveillance of C. jejuni and will be an excellent tool for source identification in outbreak situations.

A variation of the amplified-fragment length polymorphism (AFLP) technique using three restriction endonucleases, and assessment of the enzyme combination BglII-MfeI for AFLP analysis of Salmonella enterica subsp. enterica isolates

We have performed amplified-fragment length polymorphism (AFLP) fingerprinting on a collection of Salmonella enterica subsp. enterica serovar typhimurium strains with a restriction endonuclease combination (BglII and MfeI) that has previously been used successfully for typing Campylobacter jejuni isolates with high resolution. Additionally, a variation of the AFLP assay in which two rare cutting restriction enzymes (XbaI and BsrGI) in combination with the frequent cutter (HinP1I) was examined. The BglII and MfeI enzyme combination offered low resolution for genotyping Salmonella typhimurium isolates and is not recommended for this common serovar. The three-enzyme combination gave a higher discrimination, and is thus a new alternate way of performing AFLP fingerprinting of S. typhimurium.

Computer-assisted analysis and epidemiological value of genotyping methods for Campylobacter jejuni and Campylobacter coli

For epidemiological tracing of the thermotolerant Campylobacter species C. jejuni and C. coli, reliable and highly discriminatory typing techniques are necessary. In this study the genotyping techniques of flagellin typing (flaA typing), pulsed-field gel electrophoresis (PFGE), automated ribotyping, and amplified fragment length polymorphism (AFLP) fingerprinting were compared. The following aspects were compared: computer-assisted analysis, discriminatory power, and use for epidemiological typing of campylobacters. A set of 50 campylobacter poultry isolates from The Netherlands and neighboring countries was analyzed. Computer-assisted analysis made cluster analysis possible and eased the designation of different genotypes. AFLP fingerprinting was the most discriminatory technique, identifying 41 distinct genotypes, while PFGE identified 38 different types, flaA typing discriminated 31 different types, and ribotyping discriminated 26 different types. Furthermore, AFLP analysis was the most suitable method for computer-assisted data analysis. In some cases combining the results of AFLP fingerprinting, PFGE, and flaA typing increased our ability to differentiate strains that appeared genetically related. We conclude that AFLP is a highly discriminatory typing method and well suited for computer-assisted data analysis; however, for optimal typing of campylobacters, a combination of multiple typing methods is needed.

Genetic diversity of the Campylobacter genes coding immunodominant proteins

Three Campylobacter jejuni 72Dz/92 genes (cjaA (ompH1), cjaC (hisJ) and cjaD (omp18)) encoding immunodominant proteins are considered to be potential chicken vaccine candidates. The presence and conservation of cjaA, cjaC and cjaD genes among different Campylobacter clinical isolates were determined. The genes were detected in thirty Campylobacter strains using hybridization as well as Western blot analysis. However, PCR products of the predicted size were amplified only from ten out of thirty examined strains regardless of the employed primer pair. The nucleotide sequence of the C. jejuni 72Dz/92 genes was compared with the nucleotide sequences of their homologs cloned from other Campylobacter strains as well as with the whole genome sequence of C. jejuni NCTC 11168. The examined sequences revealed 0 to 16% divergence. Strain-dependent levels of divergence were observed. The polymorphism detected in cjaC was mainly within the 5' region of the gene, while the nucleotide substitutions in cjaA and cjaD are distributed uniformly along the whole genes. Most of the observed nucleotide substitutions occurred at the third base of the codons. This observation is consistent with the results of Western blot experiments.

Integronlike structures in Campylobacter spp. of human and animal origin

Resistance to antimicrobial agents used to treat severe Campylobacter spp. gastroenteritis is increasing worldwide. We assessed the antimicrobial resistance patterns of Campylobacter spp. isolates of human and animal origin. More than half (n = 32) were resistant to sulphonamide, a feature known to be associated with the presence of integrons. Analysis of these integrons will further our understanding of Campylobacter spp. epidemiology.

Pathophysiology of Campylobacter jejuni infections of humans

Campylobacter jejuni and closely related organisms are major causes of human bacterial enteritis. These infections can lead to extraintestinal disease and severe long-term complications. Of these, neurological damage, apparently due to the immune response of the host, is the most striking. This review examines current knowledge of the pathophysiology of the organism. Diversity of C. jejuni isolates in genotypic and phenotypic characteristics now is recognized and clinically relevant examples are presented. Expected future directions are outlined.