Taxonomy of Campylobacter, Arcobacter, and Helicobacter: a review

Comparison of the Diagnostic Accuracy of Three Real-Time PCR Assays for the Detection of Arcobacter butzleri in Human Stool Samples Targeting Different Genes in a Test Comparison without a Reference Standard

Potential etiological relevance for gastroenteric disorders including diarrhea has been assigned to Arcobacter butzleri. However, standard routine diagnostic algorithms for stool samples of patients with diarrhea are rarely adapted to the detection of this pathogen and so, A. butzleri is likely to go undetected unless it is specifically addressed, e.g., by applying pathogen-specific molecular diagnostic approaches. In the study presented here, we compared three real-time PCR assays targeting the genes hsp60, rpoB/C (both hybridization probe assays) and gyrA (fluorescence resonance energy transfer assay) of A. butzleri in a test comparison without a reference standard using a stool sample collection with a high pretest probability from the Ghanaian endemicity setting. Latent class analysis was applied with the PCR results obtained with a collection of 1495 stool samples showing no signs of PCR inhibition to assess the real-time PCR assays' diagnostic accuracy. Calculated sensitivity and specificity were 93.0% and 96.9% for the hsp60-PCR, 100% and 98.2% for the rpoB/C-PCR, as well as 12.7% and 99.8% for the gyrA-PCR, respectively. The calculated A. butzleri prevalence within the assessed Ghanaian population was 14.7%. As indicated by test results obtained with high-titer spiked samples, cross-reactions of the hsp60-assay and rpoB/C-assay with phylogenetically related species such as A. cryaerophilus can occur but are less likely with phylogenetically more distant species like, e.g., A. lanthieri. In conclusion, the rpoB/C-assay showed the most promising performance characteristics as the only assay with sensitivity >95%, albeit associated with a broad 95%-confidence interval. In addition, this assay showed still-acceptable specificity of >98% in spite of the known cross-reactivity with phylogenetically closely related species such as A. cryaerophilus. If higher certainty is desired, the gyrA-assay with specificity close to 100% can be applied for confirmation testing with samples showing positive rpoB/C-PCR results. However, in case of a negative result in the gyrA-assay, this cannot reliably exclude the detection of A. butzleri in the rpoB/C-assay due to the gyrA-assay's very low sensitivity.

Molecular detection and genetic characterization of Arcobacter butzleri isolated from red-footed pet tortoises suspected for Campylobacter spp. from Grenada, West Indies

The aim of the study was to detect and genetically characterize Arcobacter butzleri in pet red-footed tortoises suspected for Campylobacter spp., using molecular techniques. A written consent from tortoise owners was obtained, after explaining the advantages of the research to tortoise owners of Grenada. Fecal samples were collected from 114 tortoises from five parishes of the country and cultured for Campylobacter spp. using selective culture techniques. A. butzleri was isolated from 4.39% of pet tortoises. Total thirteen isolates were obtained; all identified as A. butzleri by a universal and a species-specific Polymerase Chain Reaction (PCR) and direct sequencing. Genetic characterization of these isolates was performed based on Enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) that generated eight different genetic fingerprints with a discriminatory power of 0.91. Campylobacter species were not detected molecularly in any of the culture-positive samples. This is the first report of infection of pet tortoises in Grenada, West Indies with A. butzleri. This study emphasizes on the risk of zoonotic transmission of A. butzleri by exotic pets, which is a serious concern for public health.

Enhanced Single-tube Multiplex PCR Assay for Detection and Identification of Six Arcobacter Species

AIM

A single-tube multiplex PCR (mPCR) assay was developed for rapid, sensitive and simultaneous detection and identification of six Arcobacter species including two new species, A. lanthieri and A. faecis, along with A. butzleri, A. cibarius, A. cryaerophilus and A. skirrowii on the basis of differences in the lengths of their PCR products. Previously designed monoplex, mPCR and RFLP assays do not detect or differentiate A. faecis and A. lanthieri from other closely related known Arcobacter spp.

METHODS AND RESULTS

Primer pairs for each target species (except A. skirrowii) and mPCR protocol were newly designed and optimized using variable regions of housekeeping including cpn60, gyrA, gyrB and rpoB genes. The accuracy and specificity of the mPCR assay was assessed using DNA templates from six targets and 11 other Arcobacter spp. as well as 50 other bacterial reference species and strains. Tests on the DNA templates of target Arcobacter spp. were appropriately identified, whereas all 61 other DNA templates from other bacterial species and strains were not amplified. Sensitivity and specificity of the mPCR assay was 10 pg μl^-1 of DNA concentration per target species. The optimized assay was further evaluated, validated and compared with other mPCR assays by testing Arcobacter cultures isolated from various faecal and water sources.

CONCLUSIONS

Study results confirm that the newly developed mPCR assay is rapid, accurate, reliable, simple, and valuable for the simultaneous detection and routine diagnosis of six human- and animal-associated Arcobacter spp.

SIGNIFICANCE AND IMPACT OF THE STUDY

The new mPCR assay is useful not only for pure but also mixed cultures. Moreover, it has the ability to rapidly detect six species which enhances the value of this technology for aetiological and epidemiological studies.

Influence of pH of TSI medium on the detection of hydrogen sulfide production by Campylobacter hyointestinalis

AIMS

To examine the influence of pH of triple sugar iron (TSI) agar medium on the detection of hydrogen sulfide (H(2)S) production in Campylobacter hyointestinalis ssp. hyointestinalis (CHH).

METHODS AND RESULTS

TSI medium was adjusted by the addition in HCl or NaOH to cover a pH 6.0-9.0. One loopful of bacterial growth of CHH strain ATCC 35217 was inoculated into each different pH medium, and incubated at 37 degrees C under micro-aerobic conditions. The H(2)S production was not detectable even after incubation for 72 h in acidic medium pH; however, TSI with alkaline pH (8.0-9.0) allowed detection as early as 3 h of incubation. A total of 20 CHH strains from various animal sources were examined for the detection of H(2)S production in TSI medium with pH 9.0. The H(2)S was detected in all the strains examined within 12 h, and the judgment was unambiguous.

CONCLUSION

The results showed that the detection of H(2)S production by CHH was influenced by medium pH, and TSI with alkaline condition is highly sensitive.

SIGNIFICANCE AND IMPACT OF THE STUDY

The findings of the present study suggest that TSI medium with alkaline pH contributes to fast detection and led to unambiguous judgment of H(2)S production by CHH.

Antimicrobial susceptibility of clinical isolates of non-jejuni/coli campylobacters and arcobacters from Belgium

OBJECTIVES

To determine the susceptibility of non-jejuni/coli campylobacters and arcobacters isolated from diarrhoeal stool specimens in Belgium.

METHODS

The MICs were determined using Etest for six antimicrobial agents including ampicillin, erythromycin, nalidixic acid, ciprofloxacin, gentamicin and tetracycline for the most frequently isolated non-jejuni/coli campylobacter and arcobacter strains in two University Hospital laboratories between 1995 and 2005.

RESULTS

In total, 85 Campylobacter upsaliensis, 20 Campylobacter concisus, 11 Campylobacter fetus, 61 Arcobacter butzleri and 10 Arcobacter cryaerophilus isolates were tested. Most C. upsaliensis strains were susceptible to ampicillin (100%), gentamicin (100%), ciprofloxacin (94.1%) and tetracycline (100%), whereas 11.8 and 12.9% were resistant to nalidixic acid and erythromycin, respectively. For A. butzleri, 78.7% of isolates were susceptible to ampicillin and erythromycin. Most A. butzleri isolates were susceptible to ciprofloxacin (96.7%), nalidixic acid (82.0%), gentamicin (100%) and tetracycline (100%). All C. concisus strains were fully susceptible to ampicillin and tetracycline, but 5% of them were resistant to gentamicin, ciprofloxacin and erythromycin. Nearly all C. fetus and A. cryaerophilus strains were susceptible to erythromycin but the results should be interpreted with caution since only a small number of strains were tested.

CONCLUSIONS

Fluoroquinolones should be considered in the treatment of severe C. upsaliensis and A. butzleri infection. When clinically indicated, erythromycin remains the first choice for the treatment of intestinal campylobacteriosis caused by C. concisus and C. fetus.

Campylobacter, from obscurity to celebrity

After its successful isolation from stools in the 1970s, Campylobacter jejuni has rapidly become the most commonly recognised cause of bacterial gastroenteritis in man. Reported cases of human campylobacteriosis represent only a small fraction of the actual number. In industrialised countries, the incidence of C. jejuni/Campylobacter coli infections peaks during infancy, and again in young adults aged 15-44 years. Acute self-limited gastrointestinal illness, characterised by diarrhoea, fever and abdominal cramps, is the most common presentation of C. jejuni/C. coli infection. The introduction of selective media has made the diagnosis of Campylobacter enteritis a simple procedure. In general, Campylobacter enteritis is a self-limiting disease which seldom requires antimicrobial therapy, although one in 1000 infections may lead to the Guillain-Barré syndrome. In industrialised countries, most infections are acquired through the handling and consumption of poultry meat. In developing countries, where the disease is confined to young children, inadequately treated water and contact with farm animals are the most important risk factors. Many infections are acquired during travel. Fluoroquinolone resistance has been reported in C. jejuni since the late 1980s in Europe and Asia, and since 1995 in the USA. The use of fluoroquinolones to treat animals used for food has accelerated this trend of resistance. In Australia, where fluoroquinolones have not been licensed for use in food production animals, C. jejuni remains susceptible to fluoroquinolones. The public health burden of Campylobacter spp. other than C. jejuni/C. coli remains unmeasured. Better diagnostic methods may reveal the true health burden of these organisms.

Detection of Arcobacter spp. in the coastal environment of the Mediterranean Sea

The occurrence of Arcobacter spp. was studied in seawater and plankton samples collected from the Straits of Messina, Italy, during an annual period of observation by using cultural and molecular techniques. A PCR assay with three pairs of primers targeting the 16S and 23S rRNA genes was used for detection and identification of Arcobacter butzleri, Arcobacter cryaerophilus, and Arcobacter skirrowii in cultures and environmental samples. Only one of the Arcobacter species, A. butzleri, was isolated from seawater and plankton samples. With some samples the A. butzleri PCR assay gave amplified products when cultures were negative. A. cryaerophilus and A. skirrowii were never detected by culture on selective agar plates; they were detected only by PCR performed directly with environmental samples. Collectively, our data suggest that culturable and nonculturable forms of Arcobacter are present in marine environments. The assay was useful for detecting Arcobacter spp. both as free forms and intimately associated with plankton. This is the first report showing both direct isolation of A. butzleri and the presence of nonculturable Arcobacter spp. in the coastal environment of the Mediterranean Sea.

Evaluation of the ProSpecT Microplate Assay for detection of Campylobacter: a routine laboratory perspective

OBJECTIVES

To evaluate the use of the new enzyme-linked immunosorbent assay, the ProSpecT Campylobacter Microplate Assay (Alexon-Trend, Minneapolis, MN, USA), which allows 2-h detection of both Campylobacter jejuni and Campylobacter coli antigen directly in stool specimens.

METHODS

Over 4 months, all stool samples preserved in Cary-Blair medium, or fresh specimens, from non-hospitalized children and HIV-infected patients (adults and children), submitted to our laboratory were evaluated with the ProSpecT Campylobacter Microplate Assay. Results were compared with those obtained by routine culture methods using both a specific medium and a filtration method for the recovery of Campylobacter spp.

RESULTS

Of the 1205 stool specimens cultured, 101 were found to be positive for either C. jejuni or C. coli, giving an overall recovery rate of 8.38%. Ninety samples were positive by both culture and ProSpecT Campylobacter Microplate Assay, and 11 were positive by culture only, giving a sensitivity of 89.1%. In addition, of 1104 samples negative by culture, 25 were initially positive by ProSpecT Campylobacter Microplate Assay. We found no cross-reaction with other bacterial enteropathogens isolated from stool specimens. These results thus confirm a high specificity (97.7%) for both C. jejuni and C. coli. The positive and negative predictive values found were 78.3% and 99%, respectively. There was no statistically significant difference in sensitivity and specificity if the stool was fresh or preserved with Cary-Blair medium.

CONCLUSION

These data suggest that the ProSpecT Campylobacter Microplate Assay is a rapid and easy-to-use test for the detection of both C. jejuni and C. coli in stool specimens. It could be used for patients for whom early antibiotic therapy is needed or for epidemiologic studies.

Isolation and characterization of Campylobacter, Helicobacter, and Anaerobiospirillum strains from a puppy with bloody diarrhea

We carried out a microscopic examination of stools from a 2-month-old female puppy with bloody diarrhea, and this revealed large numbers of different spiral-shaped bacteria. To isolate these organisms, a rectal swab specimen was inoculated onto plates of Skirrow's agar and incubated at 37 degrees C for 6 days in a microaerobic atmosphere. Finally, a total of six different spiral-shaped bacteria (strains G1104, 94105, FR106, B0101, 3J102, and J2103) were isolated. Based on their morphology, biochemical traits, whole-cell protein profiles, and analysis of their 16S rDNA sequences, they were identified as Campylobacter upsaliensis, Helicobacter cinaedi, 'Flexispira rappini', two Anaerobiospirillum spp. with different morphologies, and Helicobacter sp., respectively. Analysis of 16S rRNA gene sequence data for strains 94150 (H. cinaedi) and FR106 (F. rappini) revealed that this approach has limitations when identifying isolates to the species level because of a high degree of sequence homology between these species (>99%) and considerable sequence variation among different isolates within these species. The dog was treated orally with amoxicillin for 3 days, which resolved the diarrhea. However, 1 day after the last dose the bloody diarrhea recurred but regarded to six more days amoxicillin treatment. This suggests a bacterial cause for the diarrhea. The approach to identification to microaerobic spiral-shaped bacteria in diarrheic dogs can be applied further to characterize their role in diarrhea illness.

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

AIMS

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

METHODS AND RESULTS

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

CONCLUSIONS

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

SIGNIFICANCE AND IMPACT OF THE STUDY

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

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.

Isolation of Campylobacter concisus from feces of children with and without diarrhea

A prospective study compared fecal isolation rates of Campylobacter concisus for children with diarrhea and without diarrhea by a filter technique in which media were incubated for 4 days in a microaerobic atmosphere. No statistically significant difference in isolation rates was found (13.2% in patients with diarrhea and 9% in controls). Moreover, 35 of 37 children attending the same day care center harbored different C. concisus strains, as was demonstrated by arbitrary primer PCR DNA fingerprinting. These data suggest a lack of a pathogenic role for C. concisus in enteritis.

A selective medium for the isolation of Arcobacter from meats

A method, including enrichment in Arcobacter Selective Broth (ASB) and isolation on semisolid Arcobacter Selective Medium (ASM) under aerobic conditions at 24 degrees C, is described for the isolation of Arcobacter from retail meat products. Selective agents used in ASB and ASM were cefoperazone, trimethoprim, piperacillin and cycloheximide. Arcobacters were isolated from 53 (24.1%) of 220 poultry meat products and also, at lower incidence from samples of beef and pork. The isolates were identified as A. butzleri or A. butzleri-like and belonged to a wide variety of serotypes and biotypes.

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.

Culture media for the isolation of campylobacters

The history of the development of selective media for isolation of campylobacters, including the rationale for choice of selective agents is described. Developments have included modifications to allow incubation at 37 degrees C instead of 42 or 43 degrees C and changes in the types and concentrations of antibiotics in order not to inhibit organisms such as Campylobacter upsaliensis, C. jejuni subsp. doylei and some strains of C. coli and C. lari. When examining foods, plating media originally developed for isolation from faeces are normally used, sometimes after liquid enrichment. Most of the media include ingredients intended to protect campylobacters from the toxic effect of oxygen derivatives. Most commonly used are lysed or defibrinated blood; charcoal; a combination of ferrous sulphate, sodium metabisulphite and sodium pyruvate (FBP); and haemin or haematin. To date no medium includes an indicator system--for instance a pH indicator to show whether colonies produce acid or alkali from particular substrates. The manner in which liquid enrichment media are used has been modified for food samples to avoid inhibitory effects on sublethally damaged cells by toxic components in the formula. This is done by a preliminary period of incubation at reduced temperature and sometimes by delayed addition of antibiotics. Expensive and time-consuming methods have been proposed to achieve a microaerobic atmosphere while using liquid enrichment media. To date there is no generally accepted 'standard' method of isolating campylobacters from food.

Identification of Campylobacter jejuni on the basis of a species-specific gene that encodes a membrane protein

To facilitate discrimination between the closely related enteropathogens Campylobacter jejuni and C. coli, unique differences in antigenic surface structure were examined. A genomic library of C. jejuni 81116 was constructed in plasmid pBluescriptIISK- and expressed in Escherichia coli K-12. Rabbit hyperimmune serum raised against C. jejuni ATCC 29428 recognized a clone expressing a C. jejuni 24-kDa membrane-associated protein. Antiserum raised against sonicated recombinant E. coli expressing the 24-kDa protein reacted with C. jejuni, whereas C. coli did not react specifically. Determination of the nucleotide sequence of the DNA insert of this recombinant plasmid revealed an open reading frame encoding 214 amino acids; the gene was designated mapA; and its gene product was designated MAPA. The 18 N-terminal amino acid residues constitute a signal sequence characteristic of prokaryotic membrane lipoproteins. In a dot blot hybridization assay with a mapA probe, 120 clinical isolates of C. jejuni were unequivocally discriminated from 126 other campylobacters, including 34 C. coli isolates. A PCR test based on the mapA sequence was developed for identification of C. jejuni. A PCR product was obtained with all of the clinical isolates of C. jejuni tested from human, dog, cat, bovine calf, and chicken sources. Recombinant MAPA with an added C-terminal six-histidine tail was affinity purified and used to immunize rabbits. The rabbit anti-MAPA serum specifically recognized the protein in whole cells of C. jejuni on Western blots (immunoblots). The MAPA protein was present in all of the C. jejuni strains tested and was absent in C. coli and related campylobacters.

Rapid detection of Campylobacter jejuni and Campylobacter coli isolated from clinical specimens using the polymerase chain reaction

Seventeen Campylobacter strains isolated from 16 children hospitalised with acute diarrhea were analysed by in vitro enzymatic amplification using two sets of oligonucleotide primers specific for Campylobacter jejuni and Campylobacter coli, respectively. Thirteen strains (76%) were identified as Campylobacter jejuni and four strains (24%) as Campylobacter coli. Subsequent bacteriological identification confirmed the identity of the same 13 Campylobacter jejuni strains and the 4 Campylobacter coli strains. Thus, these PCR methods enabled rapid and specific detection of all the Campylobacter jejuni and Campylobacter coli strains without any false-positive or false-negative results.

Chemotaxonomy of Bacteroides: a review

The loose definition of Bacteroides, some species of which are important etiologic agents of oral diseases, has enabled isolates with only marginal similarities to be reposited in this genus. Many attempts have been made over the years to improve the taxonomy of this heterogeneous group of bacteria. The present article reviews major chemotaxonomic characters and techniques that have been used for this purpose: pigmentation, metabolites, whole-cell fatty acids, phospholipids, isoprenoid quinones, carbohydrates of lipopolysaccharide, whole-cell proteins, peptidoglycans, enzymes, pyrolysis mass spectrometry, DNA composition, restriction fragment length polymorphisms of DNA and ribosomal (r) RNA, homology of DNA and RNA, DNA-rRNA hybridization, and 16S and 5S rRNA oligonucleotide cataloging and sequencing. Despite improvements in their taxonomy, some bacteroides are still misclassified. Suggestions for further improvements in the taxonomy of bacteroides are made.

Severe diarrhea associated with Arcobacter butzleri

Two patients with chronic disease (diabetes mellitus type I, hyperuricemia and alcohol abuse, respectively) were hospitalized with persistent diarrhea and severe abdominal cramps. Using routine methods, the only pathogen isolated in stool specimens was Arcobacter butzleri. In both cases acute symptoms subsided quickly after antibiotic therapy. After termination of antibiotic treatment, Arcobacter butzleri could no longer be detected in stool specimens. Although very little is known about the clinical significance of Arcobacter butzleri infections in humans, it is highly likely that in both cases Arcobacter butzleri played a major causative role in acute disease.