Comparison of PFGE, ribotyping and phage-typing in the epidemiological analysis of Campylobacter jejuni serotype HS2 infections

Prevalence, Persistence, and Antimicrobial Resistance of Campylobacter spp. from Eggs and Laying Hens Housed in Five Commercial Housing Systems

Husbandry practices for laying hens in commercial egg production is a topic of interest from a social, economic, and regulatory standpoint. Animal welfare concerns regarding the use of conventional cages have arisen and consumer perceptions of hen welfare have led to a higher demand for cage-free eggs. The aim of this study was to assess the impact of housing systems on prevalence, persistence, and antimicrobial resistance (AMR) of Campylobacter from laying hens and shell eggs. A total of 425 samples were collected over a 10-month period from the North Carolina Layer Performance and Management Test and Campylobacter isolates were identified by serological, biochemical, and molecular tests. Genetic variability was evaluated using pulsed-field gel electrophoresis (PFGE) and AMR testing was performed. Prevalence of Campylobacter spp. ranged from 11.1% in the enrichable cages to 19.7% in the conventional systems. A greater prevalence of Campylobacter was found in the fecal swab samples from free-range birds compared with those of birds housed in the more intensive housing systems (p > 0.05). Overall, 72 isolates were confirmed as Campylobacter spp. by PCR. More than 90% of the isolates (n = 66) were identified as Campylobacter jejuni, followed by Campylobacter coli (n = 6). C. jejuni isolates displayed high levels of resistance to tetracycline (67%). Genetic variability of Campylobacter was high, with more than 20 PFGE patterns identified. Pattern "a" comprised 42% of isolates from all housing systems and was also the most persistent. This study suggests that housing systems of laying hens used for commercial shell egg production may impact the rate of Campylobacter shedding by layers. Isolation rates and tetracycline resistance levels of this pathogen are still of concern, emphasizing the need for well-implemented biosecurity measures on the farm.

Campylobacter Phage Isolation and Characterization: What We Have Learned So Far

Lytic Campylobacter phages, which can be used to combat this pathogen in animals and on food products, have been studied for more than 30 years. Though, due to some peculiarities of the phages, which hampered their isolation and particularly their molecular analysis for a long time, progress in this research field was rather slow. Meanwhile, the situation has changed and much more is known about the biology and genetics of those phages. In this article, we address specific issues that should be considered when Campylobacter phages are studied, starting with the isolation and propagation of the phages and ending with a thorough characterization including whole-genome sequencing. The basis for advice and recommendations given here is a careful review of the scientific literature and experiences that we have had ourselves with Campylobacter phages.

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.

Global Distribution of Campylobacter jejuni Penner Serotypes: A Systematic Review

Penner serotyping has been the principal method for differentiating Campylobacter isolates since its inception. Campylobacter capsule polysaccharide (CPS), the principal serodeterminant on which Penner serotyping is based, is presently of interest as a vaccine component. To determine the required valency of an effective CPS-based vaccine, a comprehensive understanding of CPS distribution is needed. Because of the association between Penner serotype and CPS, we conducted a systematic review to estimate the frequency and distribution of Penner serotypes associated with cases of Campylobacteriosis. In total, more than 21,000 sporadic cases of C. jejuni cases were identified for inclusion. While regional variation exists, distribution estimates indicate that eight serotypes accounted for more than half of all sporadic diarrheal cases globally and three serotypes (HS4 complex, HS2, and HS1/44) were dominant inter-regionally as well as globally. Furthermore, a total of 17 different serotypes reached a representation of 2% or greater in at least one of the five regions sampled. While this review is an important first step in defining CPS distribution, these results make it clear that significant gaps remain in our knowledge. Eliminating these gaps will be critical to future vaccine development efforts.

Circulating Methylated XAF1 DNA Indicates Poor Prognosis for Gastric Cancer

BACKGROUND

Methylated DNA in fluids may be a suitable biomarker for cancer patients. XAF1 has been shown to be frequently down-regulated in human gastric cancer (GC). Here, we investigated if XAF1 methylation in GC could be a useful biomarker.

METHODS

Real-time RT-PCR was used to detect XAF1 mRNA expression; immunohistochemistry and western blot were used to examine XAF1 protein expression in GC tissues (n = 202) and their corresponding para-cancerous histological normal tissues (PCHNTs). Real-time methylation specific-PCR was used to investigate XAF1 promoter methylation in the same panel of GC tissues, their PCHNTs and sera.

RESULTS

We confirmed frequent XAF1 down-regulation in both mRNA and protein levels in GC tissues as compared to normal controls and PCHNTs. XAF1 hypermethylation was evidenced in 83.2% (168/202) of GC tissues and 27.2% (55/202) of PCHNTs, while no methylation was detected in the 88 normal controls. The methylation level in GC tissues was significantly higher than that in PCHNTs (p<0.05). The hypermethylation of XAF1 significantly correlated with the down-regulation of XAF1 in GC tissues in both mRNA and protein levels (p<0.001 each). Moreover, we detected high frequency of XAF1 methylation (69.8%, 141 out of 202) in the sera DNAs from the same patients, while the sera DNAs from 88 non-tumor controls were negative for XAF1 methylation. The XAF1 methylation in both GC tissues and in the sera could be a good biomarker for diagnosis of GC (AUC = 0.85 for tissue and AUC = 0.91 for sera) and significantly correlated with poorer prognosis (p<0.001). In addition, after-surgery negative-to-positive transition of XAF1 methylation in sera strongly associated with tumor recurrence.

CONCLUSIONS

1) Dysfunction of XAF1 is frequent and is regulated through XAF1 promoter hypermethylation; 2) Detection of circulating methylated XAF1 DNAs in the serum may be a useful biomarker in diagnosis, evaluating patient's outcome (prognosis and recurrence) for GC patients.

Enrichment culture can bias the isolation ofCampylobactersubtypes

Enrichment culture is often used to isolateCampylobacter. This study compared isolation ofCampylobacterspp. from 119 broiler chicken environments from two farms, using Preston and modified Exeter (mExeter) and modified Bolton (mBolton) enrichments. mExeter was significantly more effective in isolatingCampylobacterspp. from the environmental samples compared to Preston (P<0·001) and mBolton (P<0·04) broths but there was no significant difference between the latter two methods (P>0·05). Enrichment broth type did not affect isolation from chicken faecal or soil and litter samples.C. jejuniwas isolated from significantly more environmental samples using mExeter broth compared to Preston (P<0·01) and mBolton (P<0·003) broths; there was no difference between the latter two methods or between all methods for detection ofC. coli(P>0·05). OnlyC. coliwas isolated from the soil and litter samples and although bothC. jejuniandC. coliwere recovered from the faecal samples there was no effect of using different enrichment broths. The majority of samples where the same species had been isolated yielded the same or closely related genotypes as defined by pulsed-field gel electrophoresis. Isolates recovered using Preston and mBolton broths were less genetically diverse than those from mExeter broth. We conclude that the enrichment method used affects both the number and species ofCampylobacterisolated from naturally contaminated samples.

Influence of production system on the rate of onset of Campylobacter colonization in chicken flocks reared extensively in the United Kingdom

1. Because thermophilic Campylobacter spp. are common in chicken flocks reared extensively, cross-sectional and longitudinal studies were carried out on organic and free-range farms to determine the onset of colonisation (lag phase) and likely sources of flock infection. 2. For 14 organic and 14 free range flocks, there was a difference in lag phases, with the former being colonized at a mean of 14·1 d in comparison with 31·6 d for the latter. Whereas most free-range flocks became colonized when released on to pasture, those reared organically were usually colonized at the housed brooding stage. 3. Further study of organic flocks on three farms over 7 successive crop cycles confirmed that colonisation was strongly influenced by the prevailing husbandry conditions and was not a consequence of the length of the rearing period. 4. Molecular epidemiological investigations on a farm showing the shortest lag phase, using PFGE typing with two different restriction enzymes (SmaI and KpnI) and flaA SVR sequence typing, revealed that potential sources of colonisation for organic chickens were already present on the farm at the time of chick placement. Such sources included the ante area of the brooding house, surrounding pasture and other livestock being kept on the farm. 5. Overall, the study demonstrated that, under UK conditions, the prevalence of colonisation was greater in extensive flocks (95-100%) than it was for conventional broilers (55%), similar to the situation in other countries, but all three management systems showed comparable levels of caecal carriage in positive birds (log(10)/g 6·2-6·7).

Campylobacter bacteriophages and bacteriophage therapy

Members of the genus Campylobacter are frequently responsible for human enteric disease with occasionally very serious outcomes. Much of this disease burden is thought to arise from consumption of contaminated poultry products. More than 80% of poultry in the UK harbour Campylobacter as a part of their intestinal flora. To address this unacceptably high prevalence, various interventions have been suggested and evaluated. Among these is the novel approach of using Campylobacter-specific bacteriophages, which are natural predators of the pathogen. To optimize their use as therapeutic agents, it is important to have a comprehensive understanding of the bacteriophages that infect Campylobacter, and how they can affect their host bacteria. This review will focus on many aspects of Campylobacter-specific bacteriophages including: their first isolation in the 1960s, their use in bacteriophage typing schemes, their isolation from the different biological sources and genomic characterization. As well as their use as therapeutic agents to reduce Campylobacter in poultry their future potential, including their use in bio-sanitization of food, will be explored. The evolutionary consequences of naturally occurring bacteriophage infection that have come to light through investigations of bacteriophages in the poultry ecosystem will also be discussed.

Genetic characterization and antimicrobial susceptibility of Campylobacter spp. isolated from domestic and imported chicken meats and humans in Korea

This study was conducted to examine the in vitro activity of antimicrobials against Campylobacter spp. isolates from chicken and human sources and the genetic interrelation among them. During 2004-2008, a total of 173 Campylobacter spp. isolated from chicken meats (60 domestic and 62 imported chicken meats) and humans (n = 51) were tested for susceptibility to nine antimicrobials. Of 173 isolates, 140 (80.9%) showed multidrug resistance (MDR) against three to eight antimicrobials. The most frequent pattern type was MDR to four antimicrobials: ciprofloxacin, nalidixic acid, ampicillin, and tetracycline. Over 52.6% (91/173) of the isolates tested were resistant to these four antibiotics simultaneously. Especially, two and five isolates originated from Korea and Brazil showed resistance against all antibiotics tested, except for florfenicol. Further, 95% (57/60) of the isolates originated from domestic chicken showed resistance to ciprofloxacin, the antimicrobial agent of choice for treatment of human campylobacteriosis. Genotypic characterization of all Campylobacter isolates performed by pulsed-field gel electrophoresis yielded 74 types among the 173 isolates. Isolates sharing the same or similar genetic clusters were detected in different countries at different times. The pulsed-field gel electrophoresis patterns of chicken-related isolates were closely related to those of isolates from humans with gastroenteritidis. The results of this study suggest that MDR Campylobacter spp. are widespread and that Campylobacter with similar genotypes are circulating both in humans and in chicken meat in Korea.

Campylobacter immunity and coinfection following a large outbreak in a farming community

An outbreak of campylobacteriosis affected approximately one-half of 165 people attending an annual farmers' dance in Montrose, Scotland, in November 2005. Epidemiological investigations, including a cohort study (n = 164), identified chicken liver paté as the most likely vehicle of infection. Paté preparation involved deliberate undercooking of chicken livers by flash-frying, followed by mechanical homogenization. Typing of 32 Campylobacter strains (isolated from submitted stools) by multilocus sequence typing identified four distinct clades of Campylobacter jejuni. There was good agreement when isolates were typed by Penner serotyping, pulsed-field gel electrophoresis, and flaA short variable region sequencing but poorer agreement with phage and antibiotic susceptibility testing. At least three attendees were coinfected with two Campylobacter strains each. The outbreak was probably due to several livers contributing Campylobacter strains that survived undercooking and were dispersed throughout the paté. The study highlights improper culinary procedures as a potential human health risk and provides a striking counterexample to the "dominant outbreak strain" view of point source outbreaks of food-borne infections. It also demonstrates that previous exposure to biologically plausible sources of Campylobacter may confer protection against subsequent infection.

Real-time PCR approach for detection of environmental sources of Campylobacter strains colonizing broiler flocks

Reducing colonization of poultry flocks by Campylobacter spp. is a key strategy in the control and prevention human campylobacteriosis. Horizontal transmission of campylobacters, from in and around the farm, is the presumed route of flock colonization. However, the identification and prioritization of sources are confounded by the ubiquitous nature of these organisms in the environment, their poor rates of recovery by standard culture methods, and the need for cost-effective and timely methods for strain-specific comparison. A real-time PCR screening test for the strain-specific detection of campylobacters in environmental samples has been developed to address this issue. To enable this approach, fluorescently labeled PCR oligonucleotide probes suitable for a LightCycler-based assay were designed to match a highly variable DNA segment within the flaA short variable region (SVR) of Campylobacter jejuni or C. coli. The capacity of such probes to provide strain-specific tools was investigated by using bacterial cultures and spiked and naturally contaminated poultry fecal and environmental samples. The sensitivity of two representative probes was estimated, by using two different C. jejuni strains, to be 1.3 x 10(2) to 3.7 x 10(2) CFU/ml in bacterial cultures and 6.6 x 10(2) CFU/ml in spiked fecal samples. The specificity of the SVR for C. jejuni and C. coli was confirmed by using a panel of strains comprising other Campylobacter species and naturally contaminated samples. The approach was field tested by sampling the environment and feces of chickens of two adjacently located poultry houses on a conventional broiler farm throughout the life of one flock. All environmental samples were enriched for 2 days, and then DNA was prepared and stored. Where feasible, campylobacter isolates were also recovered and stored for subsequent testing. A strain-specific probe based on the SVR of the strain isolated from the first positive chicken fecal sample was developed. This probe was then used to screen the stored environmental samples by real-time PCR. Pulsed-field gel electrophoresis was used to compare recovered environmental and fecal isolates to assess the specificity of the method. The results established the proof of principle that strain-specific probes, based on the SVR of flaA, can identify a flock-colonizing strain in DNA preparations from enriched environmental cultures. Such a novel strategy provides the opportunity to investigate the epidemiology of campylobacters in poultry flocks and allows targeted biosecurity interventions to be developed. The strategy may also have wider applications for the tracking of specific campylobacter strains in heavily contaminated environments.

Genetic instability is associated with changes in the colonization potential of Campylobacter jejuni in the avian intestine

AIMS

A panel of pulsed field gel electrophoresis (PFGE) type variants of Campylobacter jejuni, previously identified as of clonal origin, were investigated to determine whether genomic instability could be observed during competitive growth.

METHODS AND RESULTS

Upon recovery from frozen storage, some variants had undergone alterations in PFGE profiles, but subsequent culture produced constant genotypes. Individual variants did not display differences in colonization potential when tested in orally challenged 1-day-old chickens. However, competitive colonization using mixtures of two or three PFGE types generally resulted, by 4 weeks postchallenge, in one predominant PFGE type in all birds. For some variant mixtures, a minor population of novel PFGE types was detected in individual birds. The creation of new variants appeared to be dependent on the extent of competition and of the individual host. Genomic rearrangements most likely explain this increase in genetic diversity, apparently without the involvement of natural transformation or plasmid acquisition. In vitro cultivation of mixed inoculations were again selected for particular variants; but genetic diversity was not generated, suggesting that the selection pressures in vitro differed from those active in vivo.

CONCLUSION

These observations support the hypothesis that by generating genetic diversity, C. jejuni can improve its phenotypic fitness to survive and colonize subsequent hosts.

SIGNIFICANCE AND IMPACT OF THE STUDY

The consequences of such observations for the development of campylobacter control strategies for poultry may be substantial.

Sources and spread of thermophilic Campylobacter spp. during partial depopulation of broiler chicken flocks

The practice of partial depopulation or thinning (early removal of a portion of birds from a commercial broiler flock) is a reported risk factor for Campylobacter colonization of residual birds because of the difficulty in maintaining biosecurity during the thinning process. The effect of this practice was studied in detail for 51 target flocks, each at a different growing farm belonging to one of seven major poultry companies throughout the United Kingdom. On 21 of these farms, the target flock was already colonized by Campylobacter, and at slaughter all cecal samples examined were positive, with a mean of 8 log CFU/g. An additional 27 flocks became positive within 2 to 6 days of the start of thinning and had similarly high levels of cecal carriage at slaughter. Just before the thinning process, Campylobacter was isolated frequently from the farm driveways, transport vehicles, equipment, and personnel. Strains from seven farms on which flocks became colonized after thinning were examined by pulsed-field gel electrophoresis typing. An association was found between strains occurring at specific sampling sites and those isolated subsequently from the thinned flocks. The results indicated that particular strains had spread from one farm to another when the farms were jointly owned by the same company and employed the same bird-catching teams and/or vehicles. These results highlight the need for better hygiene control in relation to catching equipment and personnel and more effective cleaning and disinfection of vehicles and bird-transport crates.

Characterization of genetically matched isolates of Campylobacter jejuni reveals that mutations in genes involved in flagellar biosynthesis alter the organism's virulence potential

Phenotypic and genotypic evidence suggests that not all Campylobacter jejuni isolates are pathogenic for humans. We hypothesized that differences in gene content or gene expression alter the degree of pathogenicity of C. jejuni isolates. A C. jejuni isolate (Turkey) recovered from a turkey and a second C. jejuni isolate (CS) recovered from a chicken differed in their degrees of in vitro and in vivo virulence. The C. jejuni Turkey isolate invaded INT 407 human epithelial cells and secreted the Cia (Campylobacter invasion antigen) proteins, while the C. jejuni CS isolate was noninvasive for human epithelial cells and did not secrete the Cia proteins. Newborn piglets inoculated with the C. jejuni Turkey isolate developed more severe clinical signs of campylobacteriosis than piglets inoculated with the C. jejuni CS isolate. Additional work revealed that flagellin was not expressed in the C. jejuni CS isolate. Microarray and real-time reverse transcription-PCR analyses revealed that all flagellar class II genes were significantly downregulated in the C. jejuni CS isolate compared to the C. jejuni Turkey isolate. Finally, nucleotide sequencing of the flgR gene revealed the presence of a single residue that was different in the FlgR proteins of the C. jejuni Turkey and CS isolates. Complementation of the C. jejuni CS isolate with a wild-type copy of the flgR gene restored the isolate's motility. Collectively, these findings support the hypothesis that critical differences in gene content or gene expression can alter the pathogenic potential of C. jejuni isolates.

PFGE genotyping and antimicrobial susceptibility of Campylobacter in retail poultry meat in Estonia

In the present study, the Campylobacter isolates from retail poultry meat in Estonia were sero- and genotyped, and the antimicrobial susceptibility was determined. Forty-eight chicken (36 Estonian, 12 imported) and 22 turkey (imported) Campylobacter isolates from 580 raw broiler chicken (396 Estonian, 184 imported) and 30 turkey (imported) meat samples were studied. Of the isolates, 64 were C. jejuni, 4 C. coli, and 2 Campylobacter spp. Penner serotyping of 54 C. jejuni isolates revealed 11 different serotypes, and 22% of the isolates were nontypeable by the commercial antisera. The most common serotypes O:1,44; O:21, and O:55 accounted for 28%, 13%, and 13% of the isolates, respectively. Differences in serotype distribution were seen for chicken and turkey isolates. Genotypic characterization of all Campylobacter isolates (n=70) was performed by pulsed-field gel electrophoresis (PFGE). SmaI and KpnI yielded 29 and 34 PFGE types, respectively, revealing high diversity among isolates. The serotype distribution did not show an association with the origin of the sample, but the majority of the isolates sharing a similar PFGE genotype originated from one country. High levels of resistance to ciprofloxacin (66%), nalidixic acid (66%), tetracycline (44%), ampicillin (34%), and erythromycin (14%) were detected among the 70 Campylobacter isolates. The simultaneous resistance to two or three antimicrobial agents occurred in 60% of the isolates. The Campylobacter isolates from turkey meat had higher resistance to ampicillin, ciprofloxacin, nalidixic acid, and tetracycline than those from chicken meat. None of the chicken isolates were resistant to gentamicin, and no turkey isolates to erythromycin or gentamicin.

Campylobacter spp. subtype analysis using gel-based repetitive extragenic palindromic-PCR discriminates in parallel fashion to flaA short variable region DNA sequence analysis

AIMS

The repetitive extragenic palindromic-PCR (rep-PCR) subtyping technique, which targets repetitive extragenic DNA sequences in a PCR, was optimized for Campylobacter spp. These data were then used for comparison with the established genotyping method of flaA short variable region (SVR) DNA sequence analysis as a tool for molecular epidemiology.

METHODS AND RESULTS

Uprime Dt, Uprime B1 or Uprime RI primers were utilized to generate gel-based fingerprints from a set of 50 Campylobacter spp. isolates recovered from a variety of epidemiological backgrounds and sources. Analysis and phenogram tree construction, using the unweighted pair group method with arithmetic mean, of the generated fingerprints demonstrated that the Uprime Dt primers were effective in providing reproducible patterns (100% typability, 99% reproducibility) and at placing isolates into epidemiological relevant groups. Genetic stability of the rep-PCR Uprime Dt patterns under nonselective, short-term transfer conditions revealed a Pearson's correlation approaching 99%. These same 50 Campylobacter spp. isolates were analysed by flaA SVR DNA sequence analysis to obtain phylogenetic relationships.

CONCLUSIONS

The Uprime Dt primer-generated rep-PCR phenogram was compared with a phenogram generated from flaA SVR DNA sequence analysis of the same isolates. Comparison of the two sets of resulting genomic relationships revealed that both methods segregated isolates into similar groups.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results indicate that rep-PCR analysis performed using the Mo Bio Ultra Clean Microbial Genomic DNA Isolation Kit for DNA isolation and the Uprime DT primer set for amplification is a useful and effective tool for accurate differentiation of Campylobacter spp. for subtyping and epidemiological analyses.

Genotyping of Campylobacter spp. from retail meats by pulsed-field gel electrophoresis and ribotyping

AIMS

To determine the genetic relatedness of Campylobacter spp. from retail meat products, and compare the discriminatory power of pulsed-field gel electrophoresis (PFGE) and automatic ribotyping.

METHODS AND RESULTS

A total of 378 Campylobacter isolates recovered from 159 raw meats (130 chicken, 25 turkey, three pork and one beef) sampled from 50 retail grocery stores of four supermarket chains in the Maryland suburban area from August 1999 to July 2000 were analysed by PFGE with SmaI, 120 isolates of which were also characterized by ribotyping with PstI using RiboPrinter system. A total of 148 unique PFGE patterns were identified, 91 of which were present in multiple Campylobacter isolates and 24 in multiple meat samples. Nineteen Campylobacter clones with identical PFGE patterns recurred frequently (up to nine times) throughout the sampling period. Comparing ribotyping with PFGE, we identified 44 PFGE patterns and 22 RiboGroups among the 120 isolates tested. Multiple PFGE patterns within one RiboGroup were commonly observed, as well as multiple RiboGroups within one PFGE pattern.

CONCLUSIONS

Although Campylobacter present in retail meats were genetically diverse, certain clones persisted in poultry meats. PFGE had a greater discriminatory power than ribotyping, and the two methods were complementary in genotyping Campylobacter.

SIGNIFICANCE AND IMPACT OF THE STUDY

Genomic DNA fingerprinting of Campylobacter confirmed diverse and recurrent Campylobacter clones in the retail meats, which provides additional data for a better understanding of the epidemiological aspect of Campylobacter infection.

Campylobacter jejuniisolated from retail poultry meat, bovine feces and bile, and human diarrheal samples in Japan: Comparison of serotypes and genotypes

To determine the significance of poultry and bovine as infectious sources of Campylobacter jejuni in Japan, the serotype distribution and pulsed-field gel electrophoresis (PFGE) patterns of poultry and bovine isolates were compared with those of isolates from patients with diarrhea in Akita (Japan). Serotypes O:2 and O:4-complex were common in human, poultry, and bovine isolates, and serotype O:23,36,53 was common in human and bovine isolates. SmaI PFGE patterns of isolates belonging to these serotypes were generated. Eight PFGE patterns were shared by poultry and human isolates and three patterns were shared by human and bovine isolates. Further analysis of the isolates having the same SmaI PFGE pattern by KpnI PFGE confirmed that four patterns and two patterns were still shared by poultry and human isolates, and bovine and human isolates, respectively. Thus, serotypic and genotypic data indicated a possible link between sporadic human campylobacteriosis and C. jejuni from retail poultry and bovine bile and feces, suggesting that bovine serves as an infectious source of C. jejuni in Japan, as is observed in other countries.

Application of molecular genetic methods in diagnostics and epidemiology of food-borne bacterial pathogens

Salmonella enterica, Campylobacter and Yersinia species, Shiga toxin-producing Escherichia coli (STEC), Listeria monocytogenes and Clostridium perfringens are the bacterial pathogens constituting the greatest burden of food-borne disease in Finland. Several molecular genetic methods have been applied to diagnose, discriminate and survey these bacteria. PCR, PCR-RFLP and PFGE are the most widely and successfully used. However, these methods are unable to replace conventional and internationally standardised phenotyping. Electronic database libraries of the different genomic profiles will enable continuous surveillance of infections and detection of possible infection clusters at an early stage. Furthermore, whole-genome sequence data have opened up new insights into epidemiological surveillance. Laboratory-based surveillance performed in a timely manner and exploiting adequate methods, and co-operation at local, national and international levels are among the key elements in preventing food-borne diseases. This paper reviews different applications of molecular genetic methods for investigating enteric bacterial pathogens and gives examples of the methods successfully used in diagnostics and epidemiological studies in Finland.

Adaptation of Campylobacter jejuni NCTC11168 to high-level colonization of the avian gastrointestinal tract

The genome sequence of the human pathogen Campylobacter jejuni NCTC11168 has been determined recently, but studies on colonization and persistence in chickens have been limited due to reports that this strain is a poor colonizer. Experimental colonization and persistence studies were carried out with C. jejuni NCTC11168 by using 2-week-old Light Sussex chickens possessing an acquired natural gut flora. After inoculation, NCTC11168 initially colonized the intestine poorly. However, after 5 weeks we observed adaptation to high-level colonization, which was maintained after in vitro passage. The adapted strain exhibited greatly increased motility. A second strain, C. jejuni 11168H, which had been selected under in vitro conditions for increased motility (A. V. Karlyshev, D. Linton, N. A. Gregson, and B. W. Wren, Microbiology 148:473-480, 2002), also showed high-level intestinal colonization. The levels of colonization were equivalent to those of six other strains, assessed under the same conditions. There were four mutations in C. jejuni 11168H that reduced colonization; maf5, flaA (motility and flagellation), and kpsM (capsule deficiency) eliminated colonization, whereas pglH (general glycosylation system deficient) reduced but did not eliminate colonization. This study showed that there was colonization of the avian intestinal tract by a Campylobacter strain having a known genome sequence, and it provides a model for colonization and persistence studies with specific mutations.

Antimicrobial susceptibilities and epidemiological analysis of Salmonella enteritidis isolates in Korea by phage typing and pulsed-field gel electrophoresis

A total of 81 isolates of Salmonella Enteritidis were analyzed by antibiotic susceptibility, phage typing, and pulsed-field gel electrophoresis (PFGE). Thirty-two isolates came from broiler carcasses and pig feces, and 49 isolates were from humans in Seoul and suburbs of Seoul, Korea. Antibiotic resistance was most prevalent among human isolates. Of human isolates, 89.8% were resistant to more than two antibiotics, while 64.7% of poultry isolates and 13.3% of pig isolates showed multiple resistance to more than two antibiotics. The most common phage type (PT) was PT1, followed by PT30 or 33, PT21 and PT20a. The isolates showed six PFGE patterns with XbaI or SpeI digestion, and five PFGE patterns with NotI digestion. But a single pattern, PFGE X1, S1, or N1, was predominant and the rest of the PFGE patterns differed by only one or two bands. Results indicated the spread of a genetically related clone of Salmonella Enteritidis in foods and humans in Korea and that phage typing as well as PFGE may offer an improved level of discrimination for the epidemiological investigation of Salmonella Enteritidis.

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.

Clonal complexes of Campylobacter jejuni identified by multilocus sequence typing correlate with strain associations identified by multilocus enzyme electrophoresis

Multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) with SmaI were used to subtype 55 isolates of Campylobacter jejuni from a diverse range of human and animal sources previously characterized by multilocus enzyme electrophoresis (MEE). MEE and MLST targeted 11 and 7 loci, respectively, and all loci were unique to each method. MEE, MLST, and PFGE identified 40, 37, and 48 discrete subtypes, respectively, with many of the subtypes occurring only once within the data set. Simpson's indices of diversity were calculated to be 0.979, 0.966, and 0.994 for MEE, MLST, and PFGE, respectively, demonstrating that MEE and MLST had similar discriminatory powers but that PFGE was more discriminatory. Allele diversity was higher in the MLST loci; individual single-locus diversities for the 11 MEE loci and the 7 MLST loci were 0.491 and 0.854, respectively. The clonal complexes recognized by MLST correlated with the strain associations previously recognized by MEE and contained some isolates indistinguishable by PFGE. Many clusters contained isolates from diverse geographical regions and from both humans and animals. These results demonstrate the usefulness of MLST for investigation of the global epidemiology of this important pathogen and illustrate its potential to identify indistinguishable strains or clones in geographically distinct regions.

Molecular characterization of fluoroquinolone-resistant Campylobacter spp. isolated from poultry

Campylobacteriosis, an infectious disease caused by Campylobacter jejuni and Campylobacter coli, is treated by fluoroquinolone antibiotics in clinical practices. However, use of these drugs in animal husbandry may select for fluoroquinolone-resistant campylobacters and, thereby, compromise the clinical treatment of infection. In this study, 21 fluoroquinolone-resistant campylobacters were isolated from poultry samples. Morphological and biochemical characteristics indicated that 19 isolates were C. jejuni and two were C. coli. All isolates were resistant to multiple antibiotics but sensitive to chloramphenicol and gentamicin. These isolates were characterized at the molecular level by amplifying the flagellin gene (flaA) by PCR. The PCR protocol amplified a 1.7-kb flaA gene from all isolates. RFLP analysis of the 1.7-kb amplicons after digestion with DdeI yielded four distinct patterns. The 21 fluoroquinolone-resistant campylobacter isolates were further characterized by pulsed-field gel electrophoresis (PFGE) and compared with the PFGE patterns of nine fluoroquinolone-sensitive campylobacter strains. Four of the 21 fluoroquinolone-resistant isolates were untypable by the PFGE protocol. The PFGE analysis with SalI or SmaI indicated that seven or five, respectively, of the 17 resistant isolates had identical macrorestriction profiles (mrps). However, PFGE analysis with a combination of SalI and SmaI indicated that four of the 17 isolates had similar macrorestriction profiles. The PFGE patterns of the 17 fluoroquinolone-resistant isolates were different from the nine sensitive campylobacter strains.

Campylobacter jejuni in black-headed gulls (Larus ridibundus): prevalence, genotypes, and influence on C. jejuni epidemiology

Campylobacteriosis is a zoonotic disease in which birds have been suggested to play an important role as a reservoir. We investigated the prevalence of Campylobacter jejuni subsp. jejuni in black-headed gulls (Larus ridibundus) in southern Sweden with the aim of examining the nature of C. jejuni infection in this bird species. Birds were sampled in four sampling series each year during 1999 (n = 419) and 2000 (n = 365). Longitudinally sampled C. jejuni isolates from individual gulls were subjected to macrorestriction profiling (MRP) by pulsed-field gel electrophoresis to investigate the genotypical stability during the natural course of infection. Furthermore, a subset (n = 76) of black-headed gull isolates was compared to isolates from broiler chickens (n = 38) and humans (n = 56) originating from the same geographic area. We found a pronounced seasonal variation in C. jejuni carriage, with the highest rates found in late autumn. MRP similarities were higher between isolates of human and broiler chicken origin, than between those of wild bird origin and either of the other two hosts. However, identical MRPs were found in two gull isolates and one human isolate after digestion with two restriction enzymes, strongly indicating that they may have been colonized by the same clone of C. jejuni. The MRPs most prevalent in gull isolates did not occur among isolates from humans and broiler chickens, suggesting the existence of a subpopulation of C. jejuni adapted to species-specific colonization or environmental survival.

Multiresistant clones of Salmonella enterica: The importance of dissemination

Increasing anitmicrobial resistance among foodborne pathogens has prompted calls for the reduction of anitmicrobial use in livestock to prevent future emergence or resistance. In the case of Salmonella enterica, clonal dissemination may play a more critical role in regional changes in antimicrobial resistance in Salmonellae than antimicrobial selection pressure. Multi-resistant Salmonella Typhimurium definitive type 104 (mr-DT104) emerged from an unknown location and was disseminated globally during the 1980s and 1990s. Other clones of Salmonella Typhimurium and non-Typhimurium Salmonellae have demonstrated an ability to disseminate widely. The clonal epidemiology of mr-DT104 is in contrast with that of Campylobacter jejuni, in which antimicrobial resistance is polyclonal and seems to develop in response to local antimicrobial pressures. The epidemiology of mr-DT104 is more similar to that of methicillin resistant Staphylococcus aureus, which is also characterized by international transmission of a few clonal subtypes. Control measures for multiresistant disseminated clones of Salmonellae must focus on the interruption of dissemination in order to be effective.

Diversity of Campylobacter isolates from retail poultry carcasses and from humans as demonstrated by pulsed-field gel electrophoresis

Campylobacter spp. are a major contaminant of poultry. Eating undercooked chicken and handling raw poultry have been identified as risk factors for campylobacteriosis in humans. Previous studies have found Campylobacter spp. on 90% of poultry carcasses. In the present study, pulsed-field gel electrophoresis (PFGE) was used to assess the genetic diversity of strains on retail poultry carcasses. PFGE patterns of isolates from campylobacteriosis cases were compared to those from the poultry isolates. Over a 1-year study period (March 2000 through February 2001), whole fresh young chickens (n = 72) were obtained from three retail outlets in an urban community in the south-central United States. Campylobacter spp. were isolated from 82% of these carcasses. Strains (n = 70) were defined on the basis of their PFGE pattern. Sixty-seven percent of the carcasses from which Campylobacter spp. were isolated were contaminated with more than one PFGE-distinguishable strain. During the 1-year study period, most of the PFGE patterns (59%) were limited to isolates obtained from a single carcass. Forty-one percent of the PFGE-distinguishable strains were recovered from more than one carcass. Ninety-seven percent of the carcasses contaminated with the same strain were purchased at the same time from the same store. To examine the degree of genetic stability, four strains were followed in vitro over an estimated 1,000 doublings. The PFGE pattern of one of these isolates underwent minor changes during in vitro growth. The data indicate extensive variability in the PFGE patterns of Campylobacter spp. isolated from humans and from poultry carcasses. In spite of difficulties caused by such diversity and the fact that some carcasses are contaminated with more than one strain, the pattern variation provides a useful method for linking a particular strain to its source.

Comparison of pulsed-field gel electrophoresis and amplified fragment length polymorphism techniques for investigating outbreaks of enteritis due to campylobacters

Campylobacters are the most commonly reported cause of acute bacterial enteritis in the United Kingdom and United States, with poultry, milk, and water implicated as sources or vehicles of infection. The majority of campylobacter infections are sporadic, although outbreaks may occur, and these provide an opportunity to evaluate genotypic fingerprinting techniques. In this study, pulsed-field gel electrophoresis (PFGE) was compared with single-enzyme-amplified fragment length polymorphism (SAFLP). The results for the three separate episodes indicated that SAFLP and PFGE both clustered the strains from the first incident as 100% homologous. The strains from the second and third incidents clustered as distinct from both the first incident and from each other. PFGE is well recognized as a discriminatory fingerprinting technique for campylobacters; however, SAFLP has proven to be equally discriminatory, but far less labor intensive and with the added advantages of less "hands-on" time and inexpensive equipment, it is an excellent alternative to PFGE for investigation of outbreaks.

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.

Coinfection with Campylobacter species: an epidemiological problem?

AIMS

To determine the frequency of coinfection with multiple strains in sporadic cases of human Campylobacter infection.

METHOD AND RESULTS

During 1999 10 single colonies of Campylobacter were cultured from each of 53 positive faecal samples. Five isolates were taken from nonselective agar after passive filtration of faecal suspensions and five isolates were taken from selective agar plates. All isolates were sero- and phage typed and their antibiotic resistance determined. Pulsed-field gel electrophoresis and flagellin gene typing were performed on selected isolates. One patient was infected with Camp. coli, the remainder with strains of Camp. jejuni. The majority of patients was infected with a single strain of Campylobacter, but from each of four samples, 7.5%, two strains of Camp. jejuni, confirmed by molecular typing, were identified.

CONCLUSION

Coinfection occurs in sporadic cases of campylobacteriosis.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study has implications in outbreak investigation when distinct strains have been isolated from epidemiologically related patients and/or the suspected source or vehicle.

Molecular strain typing ofCampylobacter jejuniby pulsed-field gel electrophoresis in a single day

Rapid molecular strain typing is critical for effective outbreak investigation and implementation of infection control measures. Pulsed-field gel electrophoresis is a highly discriminatory technique for Campylobacter jejuni, but generally requires 3–5 days. We describe a simplified protocol for pulsed-field gel electrophoresis that provides high quality typing of C. jejuni isolates in a single day.Key words: pulsed-field gel electrophoresis, Campylobacter jejuni, molecular epidemiology.

Rapid pulsed-field gel electrophoresis protocol for subtyping of Campylobacter jejuni

We developed a rapid pulsed-field gel electrophoresis (PFGE) protocol for subtyping Campylobacter isolates based on the standardized protocols used by PulseNet laboratories for the subtyping of other food-borne bacterial pathogens. Various combinations of buffers, reagents, reaction conditions (e.g., cell suspension concentration, lysis time, lysis temperature, and restriction enzyme concentration), and electrophoretic parameters were evaluated in an effort to devise a protocol that is simple, rapid, and robust. PFGE analysis of Campylobacter isolates can be completed in 24 to 30 h using this protocol, whereas the most widely used current protocols require 3 to 4 days to complete. Comparison of PFGE patterns obtained in six laboratories showed that subtyping results obtained using this protocol are highly reproducible.

Allelic diversity and recombination in Campylobacter jejuni

The allelic diversity and population structure of Campylobacter jejuni were studied by multilocus nucleotide sequence analysis. Sequences from seven housekeeping genes were obtained from 32 C. jejuni isolates isolated from enteritis patients in Germany, Hungary, Thailand, and the United States. Also included was strain NCTC 11168, the complete genomic sequence of which has recently been published. For all loci analyzed, multiple strains carried identical alleles. The frequency of synonymous and nonsynonymous sequence polymorphisms was low. The number of unique alleles per locus ranged from 9 to 15. These alleles occurred in 31 different combinations (sequence types), so that all but two pairs of strains could be distinguished from each other. Sequences were analyzed for evidence of recombination by the homoplasy test and split decomposition. These analyses showed that intraspecific recombination is frequent in C. jejuni and has generated extensive diversity of allelic profiles from a small number of polymorphic nucleotides.

Use of pulsed-field gel electrophoresis and flagellin gene typing in identifying clonal groups of Campylobacter jejuni and Campylobacter coli in farm and clinical environments

Although campylobacters have been isolated from a wide range of animal hosts, the association between campylobacters isolated from humans and animals in the farm environment is unclear. We used flagellin gene typing and pulsed-field gel electrophoresis (PFGE) to investigate the genetic diversity among isolates from animals (cattle, sheep, and turkey) in farm environments and sporadic cases of campylobacteriosis in the same geographical area. Forty-eight combined fla types were seen among the 315 Campylobacter isolates studied. Six were found in isolates from all four hosts and represented 50% of the total number of isolates. Seventy-one different SmaI PFGE macrorestriction profiles (mrps) were observed, with 86% of isolates assigned to one of 29 different mrps. Fifty-seven isolates from diverse hosts, times, and sources had an identical SmaI mrp and combined fla type. Conversely, a number of genotypes were unique to a particular host. We provide molecular evidence which suggests a link between campylobacters in the farm environment with those causing disease in the community.

Genomic relatedness within five common Finnish Campylobacter jejuni pulsed-field gel electrophoresis genotypes studied by amplified fragment length polymorphism analysis, ribotyping, and serotyping

Thirty-five Finnish Campylobacter jejuni strains with five SmaI/SacII pulsed-field gel electrophoresis (PFGE) genotypes selected among human and chicken isolates from 1997 and 1998 were used for comparison of their PFGE patterns, amplified fragment length polymorphism (AFLP) patterns, HaeIII ribotypes, and heat-stable (HS) serotypes. The discriminatory power of PFGE, AFLP, and ribotyping with HaeIII were shown to be at the same level for this selected set of strains, and these methods assigned the strains into the same groups. The PFGE and AFLP patterns within a genotype were highly similar, indicating genetic relatedness. The same HS serotypes were distributed among different genotypes, and different serotypes were identified within one genotype. HS serotype 12 was only associated with the combined genotype G1 (PFGE-AFLP-ribotype). These studies using polyphasic genotyping methods suggested that common Finnish C. jejuni genotypes form genetic lineages which colonize both humans and chickens.

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.

Evaluation of phenotypic and genotypic methods for subtyping Campylobacter jejuni isolates from humans, poultry, and cattle

Six methods for subtyping of Campylobacter jejuni were compared and evaluated with a collection of 90 isolates from poultry, cattle, and sporadic human clinical cases as well as from a waterborne outbreak. The applied methods were Penner heat-stable serotyping; automated ribotyping (RiboPrinting); random amplified polymorphic DNA typing (RAPD); pulsed-field gel electrophoresis (PFGE); restriction fragment length polymorphisms of the flagellin gene, flaA (fla-RFLP); and denaturing gradient gel electrophoresis of flaA (fla-DGGE). The methods were evaluated and compared on the basis of their abilities to identify isolates from one outbreak and discriminate between unrelated isolates and the agreement between methods in identifying clonal lines. All methods identified the outbreak strain. For a collection of 80 supposedly unrelated isolates, RAPD and PFGE were the most discriminatory methods, followed by fla-RFLP and RiboPrinting. fla-DGGE and serotyping were the least discriminative. All isolates included in this study were found to be typeable by each of the methods. Thirteen groups of potentially related isolates could be identified using a criterion that at least four of the methods agreed on clustering of isolates. None of the subtypes could be related to only one source; rather, these groups represented isolates from different sources. Furthermore, in two cases isolates from cattle and human patients were found to be identical according to all six methods.

Sequence polymorphism, predicted secondary structures, and surface-exposed conformational epitopes of Campylobacter major outer membrane protein

The major outer membrane protein (MOMP), a putative porin and a multifunction surface protein of Campylobacter jejuni, may play an important role in the adaptation of the organism to various host environments. To begin to dissect the biological functions and antigenic features of this protein, the gene (designated cmp) encoding MOMP was identified and characterized from 22 strains of C. jejuni and one strain of C. coli. It was shown that the single-copy cmp locus encoded a protein with characteristics of bacterial outer membrane proteins. Prediction from deduced amino acid sequences suggested that each MOMP subunit consisted of 18 beta-strands connected by short periplasmic turns and long irregular external loops. Alignment of the amino acid sequences of MOMP from different strains indicated that there were seven localized variable regions dispersed among highly conserved sequences. The variable regions were located in the putative external loop structures, while the predicted beta-strands were formed by conserved sequences. The sequence homology of cmp appeared to reflect the phylogenetic proximity of C. jejuni strains, since strains with identical cmp sequences had indistinguishable or closely related macrorestriction fragment patterns. Using recombinant MOMP and antibodies recognizing linear or conformational epitopes of the protein, it was demonstrated that the surface-exposed epitopes of MOMP were predominantly conformational in nature. These findings are instrumental in the design of MOMP-based diagnostic tools and vaccines.

Efficacy of flagellin gene typing for epidemiological studies of Campylobacter jejuni in poultry estimated by comparison with macrorestriction profiling

Thirty isolates of Campylobacter jejuni isolated from 29 different Danish broiler flocks were chosen for the evaluation of PCR-Fla typing as a genotyping tool. Except for two isolates that originated from the same broiler flock, the isolates were clearly distinguishable on basis of their macrorestriction profiles using the restriction endonucleases SmaI and KpnI. PCR-Fla typing of the 30 isolates yielded 16 distinct genotypes, whereas one isolate was untypeable by this method. The dominant PCR-Fla type (1/1) was shared by eight isolates, and five additional Fla groups containing two or three isolates were obtained. The PCR-Fla type of one isolate changed spontaneously after five subcultures, illustrating the relative plasticity of the gene locus. Comparison of MRPs within and between Fla-types support the view that some PCR-Fla types may be conserved within clonal lines. It is concluded that PCR-Fla typing is useful as a genotyping tool in large-scale epidemiological studies but that additional analyses with other methods are required to properly define interstrain relationships.

A three-year study of Campylobacter jejuni genotypes in humans with domestically acquired infections and in chicken samples from the Helsinki area

Campylobacter jejuni isolates from stool samples of patients with domestically acquired sporadic infections and from chicken from retail shops were studied during seasonal peaks from June to September over a 3-year period from 1996 to 1998. A large number of pulsed-field gel electrophoresis (PFGE) genotypes (a combined SmaI-SacII pattern) were identified each year. Certain genotypes persisted for the whole study period, and predominant genotypes represented 28 to 52% of the strains during a restricted period of time. The peak level of positive chicken samples was between July and August of each study year, when 10 to 33% of the samples were positive for campylobacter. The same PFGE genotypes found in humans were also detected in the chicken samples. This suggests that common genotypes were circulating in the area.

Restriction fragment length polymorphism analysis using random chromosomal gene probes for epidemiological analysis of Campylobacter jejuni infections

We have evaluated the ability of a new genotyping method for Campylobacter jejuni based on restriction fragment length polymorphisms using random chromosomal gene probes. DNAs from C. jejuni strains digested with each of three restriction enzymes, HhaI, HaeIII, and HpaII, were analyzed by Southern hybridization using each of two unrelated cosmid clones, P14 and P15 (respectively containing 30- and 35-kb genomic DNA fragments of C. jejuni strain OH4384). The method reported provides a stable and discriminating means for identifying C. jejuni strains and should be useful for epidemiological analyses.

Isolation and characterization of Campylobacter jejuni subsp. jejuni from macaroni penguins (Eudyptes chrysolophus) in the subantarctic region

On Bird Island, South Georgia, albatrosses (n = 140), penguins (n = 100), and fur seals (n = 206) were sampled for Campylobacter jejuni. C. jejuni subsp. jejuni was recovered from three macaroni penguins (Eudyptes chrysolophus). These isolates, the first reported for the subantarctic region, showed low genetic diversity and high similarity to Northern Hemisphere C. jejuni isolates, possibly suggesting recent introduction to the area.

Genetic diversity in Helicobacter pullorum from human and poultry sources identified by an amplified fragment length polymorphism technique and pulsed-field gel electrophoresis

Helicobacter pullorum was first isolated from the faeces and carcasses of poultry and has been associated with human gastroenteritis. The aim of this study was to examine interstrain genetic diversity within H. pullorum. Two fingerprinting techniques were used: amplified fragment length polymorphism (AFLP) and pulsed field gel electrophoretic (PFGE) analysis. The 20 strains examined were from four countries and comprised 13 human isolates and seven poultry isolates. Their identity was confirmed by a species-specific PCR assay. The human and poultry isolates had distinct genotypes and most strains showed a high degree of genetic diversity. Genotyping also indicated a clonal origin for two strains from the same poultry flock, and established a close relatedness between three chicken carcass isolates from a processing plant. It is concluded that these two genotyping techniques will provide a useful basis for future epidemiological investigations of H. pullorum in poultry, and may provide a link with its possible causal role in human gastrointestinal infections.

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.

Restriction fragment length polymorphism analysis of the flaA gene of Campylobacter jejuni for subtyping human, animal and poultry isolates

233 strains of Campylobacter jejuni were subtyped by PCR-RFLP analysis of the flagellin (flaA) gene by double digestion with EcoRI and PstI (EP flaA-profiling). The strains represented a variety of common Penner heat stable (HS) serotypes and comprised isolates of human, bovine, ovine, chicken and canine origin. FlaA amplicons were obtained directly from DNA in cell lysates of most strains. RFLP analysis showed considerable allelic variation and nine EP flaA-types were identified of which the most common were type 2 (32%), type 3 (20%), type 4 (12%) and type 6 (12%). Other flaA-profiles each represented less than 10% of strains. C. jejuni strains of each serotype generally had one or two specifically associated flaA-types although some were features of several serotypes. Strains with the same flaA-type were found in different hosts. EP flaA-profiles were reproducible, clear and simple to record, and laboratory protocols were rapid and low cost with high throughput capacity. The EP flaA-profiling scheme provided an excellent molecular subtyping method to supplement HS serotyping, and reference strains are recommended to facilitate its use in future epidemiological investigations.

High-resolution genotyping of Campylobacter strains isolated from poultry and humans with amplified fragment length polymorphism fingerprinting

For epidemiological studies of Campylobacter infections, molecular typing methods that can differentiate campylobacters at the strain level are needed. In this study we used a recently developed genotyping method, amplified fragment length polymorphism (AFLP), which is based on selective amplification of restriction fragments of chromosomal DNA, for genetic typing of Campylobacter jejuni and Campylobacter coli strains derived from humans and poultry. We developed an automated AFLP fingerprinting method in which restriction endonucleases HindIII and HhaI were used in combination with one set of selective PCR primers. This method resulted in evenly distributed band patterns for amplified fragments ranging from 50 to 500 bp long. The discriminatory power of AFLP was assessed with a C. jejuni strain, an isogenic flagellin mutant, and distinct C. jejuni strains having known pulsed-field gel electrophoresis and fla PCR-restriction fragment length polymorphism genotypes. Unrelated C. jejuni strains produced heterogeneous patterns, whereas genetically related strains produced similar AFLP patterns. Twenty-five Campylobacter strains obtained from poultry farms in The Netherlands grouped in three C. jejuni clusters that were separate from a C. coli cluster. The band patterns of 10 C. jejuni strains isolated from humans were heterogeneous, and most of these strains grouped with poultry strains. Our results show that AFLP analysis can distinguish genetically unrelated strains from genetically related strains of Campylobacter species. However, desirable genetically related strains can be differentiated by using other genotyping methods. We concluded that automated AFLP analysis is an attractive tool which can be used as a primary method for subtyping large numbers of Campylobacter strains and is extremely useful for epidemiological investigations.