Pulsed-field gel electrophoresis indicates genotypic heterogeneity among Campylobacter upsaliensis strains

Speciation of Campylobacter coli, C. jejuni, C. helveticus, C. lari, C. sputorum, and C. upsaliensis by matrix-assisted laser desorption ionization-time of flight mass spectrometry

Multiple strains of Campylobacter coli, C. jejuni, C. helveticus, C. lari, C. sputorum, and C. upsaliensis isolated from animal, clinical, or food samples have been analyzed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Whole bacterial cells were harvested from colonies or confluent growth on agar and transferred directly into solvent and then to a spot of dried 3-methoxy-4-hydroxycinnamic acid (matrix). Multiple ions in the 5,000- to 15,000-Da mass range were evident in spectra for each strain; one or two ions in the 9,500- to 11,000-Da range were consistently high intensity. "Species-identifying" biomarker ions (SIBIs) were evident from analyses of multiple reference strains for each of the six species, including the genome strains C. jejuni NCTC 11168 and C. jejuni RM1221. Strains grown on nine different combinations of media and atmospheres yielded SIBI masses within +/-5 Da with external instrument calibration. The highest-intensity C. jejuni SIBIs were cytosolic proteins, including GroES, HU/HCj, and RplL. Multiple intraspecies SIBIs, corresponding probably to nonsynonymous nucleotide polymorphisms, also provided some intraspecies strain differentiation. MALDI-TOF MS analysis of 75 additional Campylobacter strains isolated from humans, poultry, swine, dogs, and cats revealed (i) associations of SIBI type with source, (ii) strains previously speciated incorrectly, and (iii) "strains" composed of more than one species. MALDI-TOF MS provides an accurate, sensitive, and rapid method for identification of multiple Campylobacter species relevant to public health and food safety.

High-resolution genotyping of Campylobacter upsaliensis strains originating from three continents

Ninety-six Campylobacter upsaliensis strains that originated from Australia, Canada, and Europe (Germany) and that were isolated from humans, dogs, and cats were serotyped for their heat-stable surface antigens. All of them were genotyped by enterobacterial repetitive intergenic consensus sequence PCR (ERIC-PCR) profiling, and 83 strains were genotyped by macrorestriction analysis with the endonuclease XhoI. Eighty-four percent of the strains belonged to five different serotypes (serotypes OI, OII, OIII, OIV, and OVI), with the proportions of strains in each serotype being comparable among the groups of strains from all three continents. Two serotypes, OIII and OIV, were prevalent at rates of 35 to 40%. Serotypes OI, OII, and OVI were detected at rates of 1.5 to 15%. Between 10 and 17.7% of the strains did not react with the available antisera. Analysis of the ERIC-PCR profiles revealed two distinct genotypic clusters, which represented the German and the non-European strains, respectively. XhoI macrorestriction yielded two genotypic clusters; one of them contained 80.2% of the German strains and 34.6% of the non-European strains, and the second cluster consisted of 65.4% of the non-European strains and 19.8% of the German strains. Fourteen strains from all three continents were analyzed for their 16S rRNA gene sequences. Only two minor variations were detected in four of the strains. In conclusion, C. upsaliensis has undergone diverging processes of genome arrangement on different continents during evolution without segregating into different subspecies.

Genetic heterogeneity of Campylobacter concisus determined by pulsed field gel electrophoresis-based macrorestriction profiling

In order to investigate the genetic diversity of Campylobacter concisus to assist molecular typing studies, the use of macrorestriction profiling was examined. A suitable protocol was developed that included the use of formaldehyde pretreatment to prevent DNA degradation, and restriction enzyme NotI for pulsed field gel electrophoresis-based genotyping. Subsequently, 53 strains of C. concisus, principally from cases of diarrhoea in children, were examined. Fifty-one distinct patterns were obtained, indicating the high discriminatory potential of the method. Patterns comprised between one and 14 restriction fragments, with type and reference strains of two well-defined genomospecies of oral and faecal origin containing six and 12 fragments respectively. Our results show that C. concisus is genetically diverse and suggest the species as currently defined to be a taxonomic continuum comprised of several genomospecies. The pulsed field gel electrophoresis typing method described here has considerable potential for molecular epidemiological studies of C. concisus and may be a useful adjunctive method for helping to resolve key taxonomic issues for this species.

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.

Genomic heterogeneity and O-antigenic diversity of Campylobacter upsaliensis and Campylobacter helveticus strains isolated from dogs and cats in Germany

A serotyping scheme based on heat-stable surface antigens was established for 101 Campylobacter upsaliensis and 10 Campylobacter helveticus strains isolated from 261 dogs and 46 cats of different ages originating from two geographically distinct regions in Germany. The prevalence of C. upsaliensis varied between 27.8% in juvenile dogs (<12 months of age) and 55.4% in adult dogs (P < 0.05). Of the cats, 19.6% harbored C. upsaliensis, whereas 21.7% carried C. helveticus. Of the C. upsaliensis isolates from both host species, 93.1% belonged to five different serogroups, two of them being prevalent at rates of 47.5 and 27.7%, with different frequencies in both regions. Six (54.6%) of the C. helveticus isolates also belonged to serotypes found among C. upsaliensis strains, whereas five (45.4%) possessed an O antigen unique for C. helveticus. In contrast, a considerable degree of genomic diversity of the isolates was assessed by macrorestriction analyses with the endonucleases SmaI and XhoI, using pulsed-field gel electrophoresis as well as enterobacterial repetitive intergenic consensus sequence PCR (ERIC PCR). Restriction with SmaI pointed towards the existence of clonal groups associated to some extent with serotypes, while restriction with XhoI disintegrated these groups to smaller noncoherent subgroups. Analysis of ERIC PCR profiles did not exhibit any associations with serotypes. In conclusion these data demonstrate the genomic heterogeneity among C. upsaliensis strains and indicate that the combination of SmaI restriction with serotyping is a useful tool to investigate the expansion of clonal groups of C. upsaliensis.

Nonlinear electrophoresis and focusing of macromolecules

Effects of nonlinear dependence drift velocity of (double-stranded) DNA vs. electric field strength were investigated. In comparatively weak fields, the molecular drift velocity is proportional to the external electric field, while in strong fields there is additional nonlinear component. This effect offers possibilities to manipulate the total drift velocity at will-the macromolecules of different size can be made to move in opposite directions in pulsed field gel electrophoresis.A new approach for focusing DNA molecules based on nonlinear electrophoresis and geometric trapping in electric fields is proposed. The focusing is carried out in an alternating nonuniform electric field, created by using a wedge gel with hyperbolic boundaries. It is shown that the fractions separated in such wedge retain their rectilinear shape. Gel electrophoresis experiments supported the possibility of a pronounced nonlinear focusing of DNA molecules. This nonlinear separation technique presents encouraging prospects for micromanipulating systems and also for preparative isolation of long DNA fragments and development of new separation methods for bacterial fingerprinting.

Identification of Campylobacter jejuni, C. coli, C. lari, C. upsaliensis, arcobacter butzleri, and A. butzleri-like species based on the glyA gene

Currently, the detection and identification of Campylobacter and Arcobacter species remains arduous, largely due to cross-species phenotypic similarities and a relatively narrow spectrum of biochemical reactivity. We have developed a PCR-hybridization strategy, wherein degenerate primers are used to amplify glyA fragments from samples, which are then subjected to species-specific oligodeoxyribonucleotide probe hybridizations, to identify and distinguish between Campylobacter jejuni, C. coli, C. lari, C. upsaliensis, Arcobacter butzleri, and an A. butzleri-like species. Evaluation of this strategy with genomic DNA from different type strains suggests that this approach is both specific and sensitive and thus may be applicable in a diagnostic assay to identify and differentiate these highly related species.

Enteric colonisation following natural exposure to Campylobacter in pigs

A survey was conducted to establish the prevalence of Campylobacter in pigs from an integrated commercial hog farm. This study was carried out in four different groups of pigs: 1) adult gilts (50); 2) pregnant sows (9); 3) piglets at day-of-birth (73); 4) weaned piglets (20). Rectal and/or caecal samples were collected from each pig. Campylobacter was cultured and enumerated from such samples using Bolton enrichment broth and Campy-Cephex agar plates. Both biochemical and serological tests were used to determine Campylobacter species. Gilts had a 76 per cent incidence of Campylobacter with a mean of 76.3 per cent for C. jejuni, 21 per cent for C. coli and 2.6 per cent for C. lari. Pregnant sows had a 100 per cent incidence of Campylobacter with a mean of 87 per cent for C. jejuni and 13 per cent for C. coli. Newborn piglets had a 57. 8 per cent incidence of Campylobacter, rising to 100 per cent by the time of weaning. Thus it appears that pigs, from the day of birth, are highly susceptible to colonisation by Campylobacter.

Campylobacter upsaliensis: waiting in the wings

Despite strong epidemiological evidence supporting an important role for Campylobacter upsaliensis as a human enteropathogen, it remains relatively unknown in the realm of clinical microbiology. Clinical studies indicate that infection with this organism usually is associated with benign self-limiting diarrhea. However, more serious illnesses, including spontaneous abortion and hemolytic-uremic syndrome, recently have been associated with human infections. Understanding of the virulence properties and molecular biology of C. upsaliensis is beginning to evolve. There is now a pressing need for controlled, prospective epidemiologic studies in addition to further in-depth investigation of the pathogenesis of this enteric campylobacter to more precisely define its role in human disease. Furthermore, since C. upsaliensis is sensitive to the antibiotics routinely used in Campylobacter selective media, widespread appreciation of the importance of this organism will rely on the development of widely applicable, effective techniques for its isolation.