Biomedical subjects

S L On

Publications and source records attributed to S L On.

At least 37 records · Page 2Linked to original sources

PubMed1999

Extensive 16S rRNA gene sequence diversity in Campylobacter hyointestinalis strains: taxonomic and applied implications.

Phylogenetic relationships of Campylobacter hyointestinalis subspecies were examined by means of 16S rRNA gene sequencing. Sequence similarities among C. hyointestinalis subsp. lawsonii strains exceeded 99.0%, but values among C. hyointestinalis subsp. hyointestinalis strains ranged from 96.4 to 100%. Sequence similarities between strains representing the two different subspecies ranged from 95.7 to 99.0%. An intervening sequence was identified in certain of the C. hyointestinalis subsp. lawsonii strains. C. hyointestinalis strains occupied two distinct branches in a phylogenetic analysis of the genus Campylobacter, emphasizing the need for multiple strain analysis when using 16S rRNA gene sequence comparisons for taxonomic investigations.

Animals↗

PubMed1998

In vitro genotypic variation of Campylobacter coli documented by pulsed-field gel electrophoretic DNA profiling: implications for epidemiological studies.

Six isolates of Campylobacter coli from different pig herds were subcultured up to 50 times over a 6-month period and DNA samples suitable for pulsed-field gel electrophoretic (PFGE) profiling prepared at regular (1, 20, 40 and 50 passages) intervals. In 5/6 strains, changes in the banding patterns of Sma1, Sal1 and/or BamH1 digests were observed. In one such strain the differences were considered artifactual. However, significant alterations in PFGE profiles between subcultures of four strains were seen, irrespective of the restriction enzyme used. Spontaneous intramolecular genomic rearrangements were considered the most likely mechanism for the changes observed. A numerical analysis based upon the combined distribution of Sma1- and sal1-derived fragments clustered most strain subcultures together, with the exception of those from one isolate which were divided into two clusters. The effect of spontaneous genetic change on PFGE profiles must be considered when evaluating strain relationships. Numerical techniques may aid data interpretation but results must be evaluated cautiously.

Animals↗

PubMed1998

An outbreak of infectious hepatitis in commercially reared ostriches associated with Campylobacter coli and Campylobacter jejuni.

A disease causing high morbidity and mortality was observed in young ostriches from six properties in southeast Queensland, Australia. The disease affected birds from 2-8 weeks of age and was characterised clinically by bright-green urates and pathologically by severe necrotic hepatitis. The liver lesions resembled those of vibrionic hepatitis in other avian species. Campylobacter coli was isolated from the livers of affected ostriches from five of the six properties. Campylobacter jejuni subsp. jejuni was isolated from birds from the remaining property. Pulsed-field gel electrophoresis-based (PFGE) typing of representative isolates indicated that trade of infected birds between farms was an important factor in the spread of C. coli. Phenotypic and genotypic data suggest a clonal variant of the principal outbreak type may account for the remaining cases from which C. coli was found. Conventional biochemical test results and PFGE clearly distinguished the C. jejuni strain isolated from the geographically remote farm from the outbreak of C. coli type. We believe this to be the first definitive report of avian hepatitis associated with C. coli.

Animals↗

PubMed1998

Validity of SmaI-defined genotypes of Campylobacter jejuni examined by SalI, KpnI, and BamHI polymorphisms: evidence of identical clones infecting humans, poultry, and cattle.

We describe here an examination of the validity of molecular types of Campylobacter jejuni as defined by separation of SmaI-digested DNA using pulsed-field gel electrophoresis (PFGE), recently suggested as part of a molecular subtyping scheme. Thirty-four Danish strains from humans, water, poultry and cattle were assigned to one of six SmaI 'profile groups' (PGs), with two additional strains included as genotypically distinct controls. The interstrain relationships were reexamined by PFGE of SalI, KpnI and BamHI-digested DNA, and also by serotyping with heat-stable antigens. All outbreak-related strains were indistinguishable by all criteria, as were two sets of two randomly-isolated human strains. Two groups of indistinguishable isolates contained randomly isolated strains from more than one source (poultry, humans and/or cattle), a finding with significant epidemiological connotations. All 'genetically identical' strains belonged to the same serotype, whereas genetic differences were detected between strains assigned to the same SmaI PG but differing in serotype. We conclude that PFGE-based genetic fingerprinting can yield invaluable data for epidemiological studies of sporadic C. jejuni infection, but that results based on one restriction site polymorphism must be checked with another enzyme.

Animals↗

PubMed1998

Diversity and prevalence of Arcobacter spp. in broiler chickens.

Ninety-nine strains of Arcobacter spp., isolated from 10 chicken carcasses purchased from a supermarket and 15 chicken carcasses collected from a poultry abattoir, were speciated using a variety of phenotypic identification methods. All were tested using API Campy test strips and the 16-test (Preston) identification scheme developed for campylobacters. Fifty strains were selected for examination using a more comprehensive probabilistic identification scheme, and the identity of representative strains confirmed by protein profiling using SDS-PAGE. All 25 carcasses yielded Arcobacter butzleri. Three supermarket and 10 abattoir carcasses also carried A. cryaerophilus, and two abattoir carcasses carried A. skirrowii. The API Campy scheme proved unsatisfactory for identifying these strains: only 20 of 99 strains were accurately identified, all of which were A. cryaerophilus, the only Arcobacter sp. included in the database. Moreover, 76 of 99 strains were misidentified. The 16-test scheme identified all the arcobacter strains as A. cryaerophilus, since neither A. butzleri nor A. skirrowii had been described when the scheme was developed. The computer-assisted probabilistic scheme succeeded in identifying all but one strain, the identity of which was clarified by the use of SDS-PAGE. To our knowledge this is the first time that arcobacters other than A. butzleri have been reported in poultry meat or any other food of animal origin. Their high prevalence in poultry products may be of significance to public health.

Animals↗

PubMed1998

Identification of unusual Campylobacter-like isolates from poultry products as Helicobacter pullorum.

Twenty-six unclassified Campylobacter-like strains previously isolated from 15 chicken carcasses and caecal contents, together with two more strains isolated from chicken faeces on a different occasion, were identified as Helicobacter pullorum using various phenotypic identification methods. API Campy identification kits and a 16-test identification scheme developed for campylobacters failed to identify these bacteria, or identified them as Campylobacter spp. Eighteen strains (including the two isolated on a different occasion) were chosen for examination using a more comprehensive probabilistic identification scheme. Using this method, 14 of the 18 strains were identified as H. pullorum with ID scores > 95%; two strains were also identified as H. pullorum with lower ID scores. Of the remaining two strains, one was not identified with this scheme and the other was misidentified to the H. acinonyx pylori complex. Whole cell protein profiling by SDS-PAGE confirmed the identity of these isolates as H. pullorum, affirming the value of a polyphasic approach for accurately identifying campylobacteria. The comparatively high prevalence of H. pullorum in poultry determined in this study (60%) suggests that routine isolation and identification methods should be amended to enable a thorough evaluation of its role in human gastroenteritis and avian hepatitis. Some phenotypic characters useful in identifying poultry campylobacteria are presented which could be utilized, along with other technique(s), for improved differentiation of the campylobacteria that are found in poultry.

Animals↗

PubMed1998

Emended description of Campylobacter sputorum and revision of its infrasubspecific (biovar) divisions, including C. sputorum biovar paraureolyticus, a urease-producing variant from cattle and humans.

A polyphasic taxonomic study of 15 bovine and human strains assigned to the catalase-negative, urease-positive campylobacter (CNUPC) group identified these bacteria as a novel, ureolytic biovar of Campylobacter sputorum for which we propose the name C. sputorum bv. paraureolyticus: suitable reference strains are LMG 11764 (human isolate) and LMG 17590 (= CCUG 37579, bovine isolate). The present study confirmed previous findings showing that the salient biochemical tests used to differentiate C. sputorum bv. sputorum from C. sputorum bv. bubulus are not reproducible; and that the absolute validity of source-specific biovars of the species is questionable. A correlation between the results of numerical analysis of protein profiles and the reaction of strains in certain enzyme tests was, however, noted. Therefore, it is proposed that the infrasubspecific (biovar) divisions of C. sputorum should be revised to include bv. sputorum for catalase-negative strains; bv. fecalis for catalase-positive strains; and bv. paraureolyticus for urease-positive strains. Strains classified previously as bv. bubulus should be reclassified as bv. sputorum. The species description of C. sputorum is revised accordingly.

Animals↗

PubMed1998

Isolation and identification of Helicobacter spp. from canine and feline gastric mucosa.

It is known that virtually all healthy adult dogs and cats harbor spiral helicobacters in their gastric mucosa. Three species, Helicobacter felis, Helicobacter bizzozeronii, and Helicobacter salomonis have been isolated in vitro from the gastric mucosa of these animals. The aims of this study were to evaluate the efficacy of an isolation method for canine and feline gastric helicobacters that has been developed at the University of Helsinki; to estimate the prevalence and distribution of these taxa in the samples examined; and to assess the efficacy and validity of an extensive set of standardized conventional phenotypic tests, whole-cell protein profiling, and ultrastructural analysis in identifying the different species isolated from canine and feline gastric mucosa. We cultured 95 and 22 gastric mucosal biopsies from dogs and cats, respectively. Twenty-one H. bizzozeronii strains, 8 H. felis strains, 8 H. salomonis strains, 3 mixed cultures, 2 "Flexispira rappini"-like organisms, and 3 as yet uncharacterized strains were isolated from the dogs, and 3 H. felis strains were isolated from the cats. The methods used here yielded Helicobacter isolation rates of 51% from dogs and 13.6% from cats, which exceed those reported previously. The main difficulties were primary isolation, mixed cultures, and identification to the species level. In the species identification, a detailed morphological examination was found to yield important phenotypic characteristics. A large panel of biochemical and tolerance tests did not clearly differentiate the closely related species H. bizzozeronii, H. felis, and H. salomonis. Highly standardized whole-cell protein profiling was shown to be an excellent method for species identification. Improvements in culture conditions for these bacteria are still needed, especially for cats. A genetic identification method not requiring culture is needed for future studies of these very fastidious helicobacters, as the clinical significance and ecology of these species within the gastric mucosa of the domestic carnivores remain largely unknown.

Animals↗

PubMed1997

Determination of clonal relationships of Salmonella typhimurium by numerical analysis of macrorestriction profiles.

The use of numerical analysis of macrorestriction profiles resolved by pulsed-field gel electrophoresis (PFGE) for identifying epidemiological and clonal relationships between strains of Salmonella typhimurium was investigated. A cluster analysis based on Xba1 macrorestriction profiles of 40 strains was compared to biotype, phage-type and ribotype data on each isolate to validate the integrity and significance of the results. A significant correlation between these data was noted, suggesting that evolutionary divergence, of both recent and a more distant nature, may be detected. Moreover, two principal clonal lines of Salm. typhimurium appear to be prevalent in Denmark, of which one is comparatively stable with respect to phenotype and genotype, while the other is relatively diverse in these respects. We conclude that numerical analysis of macrorestriction profiles is a useful means of evaluating interstrain relationships between Salm. typhimurium strains and has practical applications for both short- and long-term epidermiological surveillance purposes.

Bacterial Typing Techniques↗

PubMed1997

Isolation and characterization of a novel catalase-negative, urease-positive Campylobacter from cattle faeces.

Forty-four strains of a phenotypically unique Campylobacter were isolated from the faeces of 26 of 45 cows in a single herd. Isolation involved enrichment and membrane filtration onto blood agar or plating onto cefoperazone amphotericin teicoplanin agar. The strains exhibited phenotypic characteristics typical for Campylobacter species. However, they were unusual in that they produced urease and copious H2S in triple sugar iron (TSI) medium, but did not produce catalase. They did not grow aerobically. None of the strains grew on modified cefoperazone charcoal deoxycholate agar (mCCDA). Macrorestriction profiles of chromosomal DNA were prepared for 15 strains using pulsed-field gel electrophoresis (PFGE). Twelve of 15 profiles were identical and all appeared to be closely related. These catalase-negative, urease-positive campylobacters (CNUPC) represent a group not previously reported. Their sensitivity to antibiotics normally used in selective media for campylobacters might explain why they have not previously been encountered. Their ecological significance and importance with respect to human and animal disease remain to be assessed.

Anaerobiosis↗

PubMed1997

Campylobacter hyoilei Alderton et al. 1995 and Campylobacter coli Véron and Chatelain 1973 are subjective synonyms.

The taxonomic affiliation of Campylobacter hyoilei was reevaluated by examining a variety of phenotypic and genotypic criteria. Whole-cell protein electrophoresis and a comparison of 66 phenotypic characters revealed that reference strains of C. hyoilei were indistinguishable from Campylobacter coli strains. These data were confirmed by a DNA-DNA hybridization level of 67% between the type strains of the two species. Several species-specific assays based on PCR amplification or probe hybridization further substantiated that C. coli strains and C. hyoilei strains are indistinguishable. It is therefore concluded that C. hyoilei and C. coli represent the same species and that the former name should be regarded as a junior synonym of the latter name.

Bacterial Proteins↗

PubMed1997

Evaluation of a PCR assay for identification and differentiation of Campylobacter fetus subspecies.

OBJECTIVE: To evaluate a polymerase chain reaction assay for identification of Campylobacter fetus and differentiation of the defined subspecies. DESIGN: Characterisation of bacterial strains by traditional phenotyping, polymerase chain reaction, a probabilistic identification scheme and macrorestriction profiling using pulsed field gel electrophoresis. PROCEDURE: The results of identification of 99 bacterial strains as determined by conventional phenotyping or by polymerase chain reaction were compared. Two of these were type strains of C fetus subsp fetus and C fetus subsp venerealis; the remaining strains were field isolates putatively identified as C fetus. In cases where the subspecies identity was disputed, isolates were identified by means of a probabilistic identification scheme and by macrorestriction profiling. RESULTS: The agreement between strain identities initially suggested by traditional phenotypic methods and the PCR assay was found to be 80.8%. The polymerase chain reaction proved to be a reliable technique for the species and subspecies identification of C fetus; equivocal results were obtained in only two instances. Initial misidentifications by conventional phenotyping methods were attributed to methodological differences used in various laboratories. CONCLUSION: Our results indicate that misidentification of C fetus in routine diagnostic laboratories may be relatively common. The PCR assay evaluated gave rapid and reproducible results and is thus a valuable adjunctive method for the identification of C fetus and subsequent subspecies differentiation.

Animals↗

PubMed1996

A probability matrix for the identification of campylobacters, helicobacters and allied taxa.

A probabilistic identification matrix for campylobacteria, comprising 76 phenotypic characters and 37 taxa, is described. The accuracy and integrity of the matrix was evaluated using established computer-assisted methods. Certain taxa (for example, Campylobacter concisus and Camp. gracilis) demonstrated significant phenotypic diversity; previous data corroborated these findings. Differentiation between a few pairs of taxa proved difficult, although discriminatory characteristics were noted in each of these cases. The results indicate that most campylobacteria can be identified accurately and objectively with phenotypic tests when probabilistic methods of data assessment are employed.

Campylobacter↗

PubMed1996

Identification methods for campylobacters, helicobacters, and related organisms.

The organisms which are referred to as campylobacteria are associated with a diverse range of diseases and habitats and are important from both clinical and economic perspectives. Accurate identification of these organisms is desirable for deciding upon appropriate therapeutic measures, and also for furthering our understanding of their pathology and epidemiology. However, the identification process is made difficult because of the complex and rapidly evolving taxonomy, fastidious nature, and biochemical inertness of these bacteria. These problems have resulted in a proliferation of phenotypic and genotypic methods for identifying members of this group. The purpose of this review is to summarize the problems associated with identifying campylobacteria, critically appraise the methods that have been used for this purpose, and discuss prospects for improvements in this field.

Agglutination↗

PubMed1995

Isolation of Arcobacter butzleri from a neonate with bacteraemia.

We describe the case of a neonate with bacteraemia from whom the recently described organism Arcobacter butzleri was isolated. This appears to be the first report of the organism causing neonatal infection. Clinical details suggest that the infection was contracted in utero, although the mother showed no evidence of disease before delivery. Treatment of the preterm infant was ultimately successful in resolving the infection but the organism proved resistant to a wide range of antibiotics. Similar patterns of antibiotic resistance were also observed in 39 reference and field strains of the genus Arcobacter. These findings, combined with available data on the distribution of Arcobacter species, suggest that these organisms may be important human pathogens. Optimized methods for their isolation and identification are therefore required so as to ascertain their role in human disease.

Bacteremia↗

PubMed1995

Campylobacter hyointestinalis subsp. lawsonii subsp. nov., isolated from the porcine stomach, and an emended description of Campylobacter hyointestinalis.

The taxonomic relationships of seven isolates obtained from porcine stomachs (the "CHY" group), which resembled (but were distinct from) the type strain and other reference strains of Campylobacter hyointestinalis, were examined by using phenotypic and genomic methods. The phenotypic characteristics and ultrastructure of the new organisms were characteristic of Campylobacter species, although they could be distinguished from all previously described taxa. A numerical analysis of 38 phenotypic characters revealed that the new isolates formed a distinct group at a similarity level of 90.1% and could be clearly distinguished from reference strains representing 20 related taxa, principally species and subspecies belonging to the genera Campylobacter, Arcobacter, and Helicobacter. DNA-DNA hybridization studies revealed that the porcine stomach strains were genomically homogeneous (levels of relatedness, 84 to 90%), although the levels of DNA homology with type and reference strains of C. hyointestinalis were relatively high (56 to 71%). Differences in the DNA base compositions of the CHY group and C. hyointestinalis strains were also observed. Our data indicate that the new porcine isolates should be considered members of a subspecies of C. hyointestinalis, for which we propose the name Campylobacter hyointestinalis subsp. lawsonii subsp. nov. The type strain is strain CHY 5 (= LMG 14432 = NCTC 12901 = CCUG 34538). The description of C. hyointestinalis is emended accordingly, and a description of Campylobacter hyointestinalis subsp. hyointestinalis subsp. nov. is given.

Animals↗

PubMed1994

Identification of outbreak-associated and other strains of Clostridium difficile by numerical analysis of SDS-PAGE protein patterns.

Seventy-three cultures of Clostridium difficile isolated both during, and in the period immediately following, an outbreak of infection in a group of three hospitals, were characterized by one-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of whole-cell proteins. Each protein pattern was characterized by the presence of one or two dense bands which were highly reproducible. The protein patterns were used as the basis for a numerical analysis which divided the strains into five phenons (electrophoretic or EP types). The majority, 60 of the 73 cultures, belonged to a single phenon which included strains from both patients and the environment. We conclude that high-resolution SDS-PAGE of proteins provides an effective method for typing C. difficile and therefore for tracing the possible spread of epidemic strains in hospitals and other institutions, thereby allowing a better understanding of the epidemiology of the organism.

Adult↗

PubMed1994

A sustained outbreak of Clostridium difficile in a general hospital: persistence of a toxigenic clone in four units.

OBJECTIVE: To evaluate the endemicity and epidemiology of toxigenic Clostridium difficile in a sustained outbreak of antibiotic-associated diarrhea. SETTING: University-affiliated, 465-bed tertiary care teaching hospital with adjacent cancer clinic in Hamilton, Ontario. DESIGN: From August 8, 1991, through August 31, 1993, a total of 187 cases were investigated for epidemiologic analysis of toxigenic C difficile from stool cultures, to identify the endemic clone(s). To assess the nature of contamination, cultures of inanimate surfaces in the patient environment from the four most affected units (medical teaching, nonteaching medical, hematologic oncology, and the intensive care unit) were processed for C difficile. The 229 clinical strains and 24 environmental strains isolated were typed by numerical analysis of SDS-PAGE protein patterns. RESULTS: A majority (81%) of cases in the epidemiologic analysis were associated with a toxigenic electrophoretic (EP) type 1 C difficile that was identical to the strain first isolated from an index case that occurred 18 months before the start of this study. Culture and typing of the C difficile strains from the inanimate surfaces in the four most affected units showed that the patient environment was contaminated with the toxigenic EP type 1 organism. Six other strains that occurred infrequently among cases also were found in the environment. CONCLUSIONS: A single predominant toxigenic clone has been implicated in a sustained outbreak of antibiotic-associated diarrhea that affected elderly patients. The "endemic" clone transmitted for the 25-month study period was linked to an index case shedding a toxigenic EP type 1 strain that occurred 21 months prior to the initial outbreak on the medical teaching unit. The patient environment in the affected units was found to be contaminated with the same clone, possibly due to shedding of organisms by fecally incontinent symptomatic patients. The extrinsic factors contributing to the endemic transmission of this one clone still are not well understood.

Bacterial Typing Techniques↗