Evaluation of the indoxyl acetate hydrolysis test for rapid differentiation of Campylobacter, Helicobacter, and Wolinella species

Rapid diagnosis and precision treatment of Helicobacter pylori infection in clinical settings

Helicobacter pylori is a gram-negative bacterium that colonizes the stomach of approximately half of the worldwide population, with higher prevalence in densely populated areas like Asia, the Caribbean, Latin America, and Africa. H. pylori infections range from asymptomatic cases to potentially fatal diseases, including peptic ulcers, chronic gastritis, and stomach adenocarcinoma. The management of these conditions has become more difficult due to the rising prevalence of drug-resistant H. pylori infections, which ultimately lead to gastric cancer and mucosa-associated lymphoid tissue (MALT) lymphoma. In 1994, the International Agency for Research on Cancer (IARC) categorized H. pylori as a Group I carcinogen, contributing to approximately 780,000 cancer cases annually. Antibiotic resistance against drugs used to treat H. pylori infections ranges between 15% and 50% worldwide, with Asian countries having exceptionally high rates. This review systematically examines the impacts of H. pylori infection, the increasing prevalence of antibiotic resistance, and the urgent need for accurate diagnosis and precision treatment. The present status of precision treatment strategies and prospective approaches for eradicating infections caused by antibiotic-resistant H. pylori will also be evaluated.

Proposal of Helicobacter higonensis sp. nov. isolated from a human clinical specimen, and emended description of Helicobacter valdiviensis Collado, 2014

We have previously isolated a gram-negative microaerophilic strain, PAGU2000T from a patient presenting with a fever in Kumamoto Prefecture, Japan. The present study aimed to comprehensively analyze the taxonomy of the isolated strain using a polyphasic approach. The 16S rRNA gene sequence analysis indicated that the strain was a member of enterohepatic Helicobacter. The strain PAGU2000T shared a 97.5% 16S rRNA gene nucleotide identity with Helicobacter valdiviensis, and this taxonomic position was confirmed by phylogenetic analysis of the GyrA amino acid sequences. The proposed strain PAGU2000T has a 1.482 Mbp chromosome with a DNA G + C content of 31.3 mol% and encodes 1520 predicted coding sequences. The average nucleotide identity between the strain PAGU2000T and type strain of H. valdiviensis was 70.3%, which was lower than the recommended threshold of 95% for species delineation. The strain PAGU2000T was a motile, non-spore-forming, and spiral-shaped bacterium, exhibiting catalase and oxidase activities but not urease and nitrate reduction. This study demonstrates that the isolate represents a novel species within enterohepatic Helicobacter, for which the name Helicobacter higonensis is proposed (type strain: PAGU2000T = GTC 16811T = LMG 33095T). In this study, we describe the phenotypic and morphological features of this strain and propose an emended description of some biochemical traits of H. valdiviensis.

Comparison of Two Culture-Based Detection Systems for the Isolation of Arcobacter butzleri, Arcobacter cryaerophilus, and Arcobacter skirrowii in Raw Ground Poultry

Arcobacters are emerging pathogens that have been underestimated due to a lack of a standardized isolation method. The aim of this research was to evaluate the ability to isolate Arcobacter butzleri, Arcobacter cryaerophilus, and Arcobacter skirrowii using two Arcobacter-specific culture detection systems: (i) the Houf broth and modified charcoal cefoperazone deoxycholate agar supplemented with cefoperazone, amphotericin B, and teicoplanin (HB/mCCDA+CAT), and (ii) the Nguyen-Restaino-Juárez Arcobacter enrichment broth and chromogenic agar (NRJ-B/M). Both detection systems were evaluated for productivity ratio, sensitivity, and specificity. As a result, the productivity ratio for both plating agars were >90%, which indicates that the selective agents used in the two plating agars did not inhibit Arcobacter growth. Moreover, sensitivity evaluations using artificially inoculated retail ground poultry (n = 780) determined that both detection systems were able to isolate A. butlzeri with >95% sensitivity at the 0.1 and 1.0-2.0 CFU/g detection level. The sensitivity in A. cryaerophilus isolation was higher for NRJ-B/M (78.0% at 0.1 CFU/g; 95.1% at 1.0-2.0 CFU/g) when compared with HB/mCCDA+CAT (34.1% at 0.1 CFU/g; 51.2% at 1.0-2.0 CFU/g). Both detection systems resulted in <50% sensitivity when isolating A. skirrowii at 0.1 and 1.0-2.0 CFU/g; however, the sensitivity for NRJ-B/M was significantly higher than HB/mCCDA+CAT. At the detection level of 5.0 CFU/g, both detection systems were able to isolate A. skirrowii with 100% sensitivity. Specificity comparisons using uninoculated ground poultry samples (n = 40) indicated the growth of background microbiota were significantly inhibited or could be easily differentiated on NRJ-B/M (90.0%, specificity) when compared with HB/mCCDA+CAT (30.0%, specificity). Overall, these results show that the NRJ-B/M detection system is a more sensitive and specific detection system when isolating Arcobacter spp. from ground chicken.

A New Method for Detection of Arcobacter butzleri, Arcobacter cryaerophilus, and Arcobacter skirrowii Using a Novel Chromogenic Agar

ABSTRACT

Arcobacter species are gram-negative rods that have been implicated in food- and waterborne illness. Although various cultural isolation methods have been proposed, the current procedures are unable to fully suppress the growth of background microbiota present in food samples, which inhibits Arcobacter isolation. The purpose of this study was to develop a selective enrichment broth and chromogenic plating medium to detect three Arcobacter species that have been recognized as emerging foodborne pathogens: Arcobacter butzleri, Arcobacter cryaerophilus, and Arcobacter skirrowii. The developed Nguyen-Restaino-Juárez (NRJ) Arcobacter detection system consists of a selective enrichment broth (NRJ-B) and a selective-differential plating medium (NRJ-M). The protocol of the detection method was determined by evaluating the growth of A. butzleri, A. cryaerophilus, and A. skirrowii under various temperatures (30, 35, and 42°C) and incubation (aerobic, microaerophilic, and anaerobic) conditions. Additionally, 47 Arcobacter strains and 39 non-Arcobacter strains were tested in inclusivity and exclusivity evaluations of NRJ-B and NRJ-M. Overall, the study determined that the optimal growth conditions of Arcobacter species using the NRJ Arcobacter detection system were aerobic incubation at 30°C. NRJ-B supported good growth of A. butzleri, A. cryaerophilus, and A. skirrowii while effectively suppressing the growth of non-Arcobacter strains after 48 h. Furthermore, NRJ-M yielded 97.8% inclusivity and 100.0% exclusivity using the tested strains and resulted in salmon-pigmented Arcobacter colonies (1.0 to 1.5 mm in diameter) after 72 h. The novel protocol is the first to develop a chromogenic plating medium for the isolation of Arcobacter species. This simple and accurate test method would greatly contribute to understanding the distribution of pathogenic Arcobacter species in food samples.

HIGHLIGHTS

Proposal of Helicobacter canicola sp. nov., previously identified as Helicobacter cinaedi, isolated from canines

During the course of our taxonomic investigation of Helicobacter cinaedi, it was realized that the strains isolated from dogs, which have been identified as H. cinaedi, showed different biochemical traits than did the isolates obtained from humans. None of the three dog isolates could reduce nitrate to nitrite, whereas all of the human H. cinaedi isolates could do so. The dog isolates showed a strong positive alkaline phosphatase reaction and could grow at 42°C, however the human isolates showed negative to very weak responses to those tests. The GyrA protein based phylogenetic analysis showed that the three isolates from dogs formed a slightly distinct cluster from the human isolate cluster. Phylogenetic analysis of the 16S rRNA, 23S rRNA, gyrB, and hsp60 gene sequences further confirmed that the dog isolates differed from the human H. cinaedi isolate cluster. The whole-genome in silico DNA similarities of each isolate based on their full genome sequences revealed that the isolates from dogs shared more than 94.9% ANIb (average nucleotide identity based on BLAST), while 94.0% ANIb were found between the isolates from dogs and the humans, including the H. cinaedi type strain ATCC BAA-847(T) (=CCUG 18818(T)). From these data, we propose a new species, 'H. canicola' sp. nov., for the isolates from dogs. The type strain is PAGU 1410(T) (CCUG 33887(T)=LMG 29580(T)).

Arcobacter marinus sp. nov

A slightly curved, rod-shaped marine bacterium, designated strain CL-S1T, was isolated from near Dokdo, an island in the East Sea, Korea. Cells were Gram-negative and grew well under either aerobic or microaerobic conditions. Analyses of the 16S rRNA and gyrA gene sequences of strain CL-S1T revealed an affiliation with the genus Arcobacter within the class Epsilonproteobacteria. Phylogenetic analyses based on 16S rRNA and gyrA gene sequences showed that strain CL-S1T formed a robust clade with Arcobacter halophilus LA31BT, with sequence similarities of 96.1 and 88.2 %, respectively. DNA–DNA relatedness between strain CL-S1T and A. halophilus DSM 18005T was 44 %, indicating that they represent genomically distinct species. Strain CL-S1T grew optimally at 30–37 °C, at pH 7 and in the presence of 3–5 % NaCl. The dominant cellular fatty acids were iso-C15 : 0 2-OH and/or C16 : 1 ω7c (28.4 %), C16 : 0 (26.2 %) and C18 : 1 ω7c (22.3 %). The DNA G+C content of strain CL-S1T was 28 mol%. Strain CL-S1T differed phenotypically from A. halophilus LA31BT based on its ability to grow aerobically at 10 °C and inability to grow under anaerobic conditions. Based on the data presented, strain CL-S1T is considered to represent a novel species of the genus Arcobacter, for which the name Arcobacter marinus sp. nov. is proposed. The type strain is CL-S1T (=KCCM 90072T =JCM 15502T).

Antimicrobial resistance of Campylobacter species isolated from edible bivalve molluscs purchased from Bangkok markets, Thailand

Campylobacter species have been recognized as the most commonly reported cause of bacterial gastroenteritis in humans. The increase of resistance rates to drugs of choice used for treatment in campylobacteriosis is becoming a public health concern. In parallel, the increased use of antimicrobials in aquaculture may lead to the emergence of resistant microorganisms and is likely to cause additional health risk to humans through food consumption. The study assesses the presence of antimicrobial resistance in Campylobacter species isolated from three groups of bivalve molluscs (bloody cockles, green mussels, and oysters) purchased from markets in Bangkok. Thirty samples were collected from each group. Susceptibility to three antimicrobials was determined using the Epsilometer test. Rates of erythromycin, nalidixic acid, and ciprofloxacin resistance in Campylobacter isolates were 72-84%, 28-40%, and 21-25%, respectively. There was no statistically significant difference in the prevalence of each antimicrobial resistance between the three groups. This study demonstrates a significant level of antimicrobial resistance in the Campylobacter spp. isolated from molluscs with a particular high rate of resistance to erythromycin. Consumption of raw molluscs contaminated with antimicrobial-resistant Campylobacter spp. may therefore result in resistant infections in humans.

Indigogenic substrates for detection and localization of enzymes

Indoxyl esters and glycosides are useful chromogenic substrates for detecting enzyme activities in histochemistry, biochemistry and bacteriology. The chemical reactions exploited in the laboratory are similar to those that generate indigoid dyes from indoxyl-beta-d-glucoside and isatans (in certain plants), indoxyl sulfate (in urine), and 6-bromo-2-S-methylindoxyl sulfate (in certain molluscs). Pairs of indoxyl molecules released from these precursors react rapidly with oxygen to yield insoluble blue indigo (or purple 6,6'-dibromoindigo) and smaller amounts of other indigoid dyes. Our understanding of indigogenic substrates was developed from studies of the hydrolysis of variously substituted indoxyl acetates for use in enzyme histochemistry. The smallest dye particles, with least diffusion from the sites of hydrolysis, are obtained from 5-bromo-, 5-bromo-6-chloro- and 5-bromo-4-chloroindoxyl acetates, especially the last of these three. Oxidation of the diffusible indoxyls to insoluble indigoid dyes must occur rapidly. This is achieved with atmospheric oxygen and an equimolar mixture of K(3)Fe(CN)(6) and K(4)Fe(CN)(6), which has a catalytic function. H(2)O(2) is a by-product of the oxidation of indoxyl by oxygen. In the absence of a catalyst, the indoxyl diffuses and is oxidized by H(2)O(2) (catalyzed by peroxidase-like proteins) in sites different from those of the esterase activity. The concentration of K(3)Fe(CN)(6)/K(4)Fe(CN)(6) in a histochemical medium should be as low as possible because this mixture inhibits some enzymes and also promotes parallel formation from the indoxyl of soluble yellow oxidation products. The identities and positions of halogen substituents in the indoxyl moiety of a substrate determine the color and the physical properties of the resulting indigoid dye. The principles of indigogenic histochemistry learned from the study of esterases are applicable to methods for localization of other enzymes, because all indoxyl substrates release the same type of chromogenic product. Substrates are commercially available for a wide range of carboxylic esterases, phosphatases, phosphodiesterases, aryl sulfatase and several glycosidases. Indigogenic methods for carboxylic esterases have low substrate specificity and are used in conjunction with specific inhibitors of different enzymes of the group. Indigogenic methods for acid and alkaline phosphatases, phosphodiesterases and aryl sulfatase generally have been unsatisfactory; other histochemical techniques are preferred for these enzymes. Indigogenic methods are widely used, however, for glycosidases. The technique for beta-galactosidase activity, using 5-bromo-4-chloroindoxyl-beta-galactoside (X-gal) is applied to microbial cultures, cell cultures and tissues that contain the reporter gene lac-z derived from E. coli. This bacterial enzyme has a higher pH optimum than the lysosomal beta-galactosidase of animal cells. In plants, the preferred reporter gene is gus, which encodes beta-glucuronidase activity and is also demonstrable by indigogenic histochemistry. Indoxyl substrates also are used to localize enzyme activities in non-indigogenic techniques. In indoxyl-azo methods, the released indoxyl couples with a diazonium salt to form an azo dye. In indoxyl-tetrazolium methods, the oxidizing agent is a tetrazolium salt, which is reduced by the indoxyl to an insoluble coloured formazan. Indoxyl-tetrazolium methods operate only at high pH; the method for alkaline phosphatase is used extensively to detect this enzyme as a label in immunohistochemistry and in Western blots. The insolubility of indigoid dyes in water limits the use of indigogenic substrates in biochemical assays for enzymes, but the intermediate indoxyl and leucoindigo compounds are strongly fluorescent, and this property is exploited in a variety of sensitive assays for hydrolases. The most commonly used substrates for this purpose are glycosides and carboxylic and phosphate esters of N-methylindoxyl. Indigogenic enzyme substrates are among many chromogenic reagents used to facilitate the identification of cultured bacteria. An indoxyl substrate must be transported into the organisms by a permease to detect intracellular enzymes, as in the blue/white test for recognizing E. coli colonies that do or do not express the lac-z gene. Secreted enzymes are detected by substrate-impregnated disks or strips applied to the surfaces of cultures. Such devices often include several reagents, including indigogenic substrates for esterases, glycosidases and DNAse.

Identification of thermotolerant campylobacter species by fluorescence in situ hybridization

Thermotolerant Campylobacter spp. (Campylobacter jejuni, C. coli, C. lari, and C. upsaliensis) are leading causes of food-borne diarrhea in humans. In this study, the usefulness of fluorescence in situ hybridization (FISH) for the identification of Campylobacter isolates was investigated. A hierarchical FISH probe set that included six group-, genus-, and species-specific probes was developed and evaluated with 12 reference strains and 94 clinical isolates of Campylobacter, Arcobacter, and Helicobacter. FISH correctly identified all isolates to the genus level and detected all thermotolerant Campylobacter isolates. The assay showed high degrees of sensitivity for the identification of C. jejuni (90%), C. coli (97%), C. lari (81%), and C. upsaliensis (100%) to the species level.

Prevalence of Campylobacter spp isolated from grower-finisher pigs in Ontario

This study aimed to establish the prevalence of Campylobacter spp. in 80 Ontario grower-finisher pig herds. Ninety-nine percent of the isolates yielded Campylobacter, C coli being the most common species detected. Control of this microorganism must rely on careful food processing and storage of pork, rather than on an on-farm approach.

Detection and identification of food-borne pathogens of the genera Campylobacter, Arcobacter and Helicobacter by multiplex PCR in poultry and poultry products

The objective of this study was to develop a multiplex polymerase chain reaction (PCR) to detect and differentiate food-borne pathogens of the three genera Campylobacter, Arcobacter and Helicobacter in a single step procedure. One common reverse primer and three genus-specific forward primers were designed by hybridizing to the 16S rRNA of selected reference strains. Besides the species with significance as food-borne pathogens isolated from poultry meat--Campylobacter jejuni, Campylobacter coli, Arcobacter butzleri and Helicobacter pullorum--several other members of these genera were tested to determine the specificity of the designed multiplex PCR. In total, 20 ATCC and NCTC reference strains of Campyobacter, Arcobacter and Helicobacter were used to evaluate the PCR. Specific amplificates were obtained from all thermophilic species of Campylobacter as well as from species of Arcobacter and Helicobacter. No amplification product was obtained from the non-thermophilic Campylobacter, C. hyointestinalis and C. fetus. Furthermore, a total of 43 field strains of the three genera isolated from poultry, pigs, cattle and humans were investigated using this PCR. To confirm the classification of 10 H. pullorum strains the 16S rRNAs were sequenced. The developed PCR is a helpful diagnostic tool to detect and differentiate Campylobacter, Arcobacter and Helicobacter isolated from poultry and poultry products.

Atypical Helicobacter canadensis strains associated with swine

Forty-two Helicobacter isolates were isolated from swine feces in The Netherlands and Denmark. All 12 isolates sequenced (16S rRNA gene) formed a robust clade with Helicobacter canadensis ( approximately 99% similarity). Species-specific PCR indicated that all of the isolates were H. canadensis isolates. Although the appearance of the porcine isolates was similar to the appearance of H. canadensis, only one of these isolates was able to hydrolyze indoxyl acetate, a cardinal characteristic of this taxon. Examination of the 23S rRNA and hsp60 genes revealed high levels of similarity between the porcine isolates and H. canadensis. However, amplified fragment length polymorphism genomic typing showed that isolates recovered from swine feces were genetically distinct from H. canadensis strains obtained from humans and geese.

Campylobacter curvus-associated hepatic abscesses: a case report

Campylobacter curvus was isolated from blood cultures of a patient with liver abscesses. Bacterial identification involved Gram staining, biochemical analysis, gas-liquid chromatography, and 16S rRNA sequencing. The difficulty in isolation, identification, and growth of the species confirms previous work that these organisms may be overlooked by conventional detection methods.

The occurrence of Cryptosporidium parvum, Campylobacter and Salmonella in newborn dairy calves in the Manawatu region of New Zealand

AIM

To determine the occurrence of Cryptosporidium parvum oocysts, Campylobacter spp and Salmonella spp in faecal samples taken from newborn dairy calves on 24 dairy farms in the Manawatu region of New Zealand.

METHODS

A cross-sectional study was conducted during the 2002 calving season. Faecal samples were collected from 185 newborn calves from a convenience sample of 24 dairy farms. The samples were tested microscopically for the presence of C. parvum oocysts, and bacteriologically for the presence of Campylobacter spp and Salmonella spp.

RESULTS

Infections with C. parvum were identified in 33/156 (21.2%) calves from 10 farms. More than 10(6) oocysts/g (OPG) faeces were detected in calves from four farms. Campylobacter spp were isolated from 58/161 (36%) calves from 18 farms; in particular, C. jejuni subsp jejuni was isolated from 11/161 (6.8%) calves from seven farms. Salmonellae were not detected.

CONCLUSIONS

Despite the short and concentrated calving pattern and the long interval between calving seasons characterising most dairy farms in New Zealand, C. parvum is widespread among calves. Campylobacter spp, especially C. jejuni, rapidly colonise the intestinal tract of newborn calves.

RELEVANCE

This study provided an estimate of the ecological impact of newborn dairy calves with regard to the potentially zoonotic enteric pathogens most frequently isolated from human gastrointestinal infections in New Zealand.

Antimicrobial resistance in Campylobacter jejuni and Campylobacter coli strains isolated in 1991 and 2001-2002 from poultry and humans in Berlin, Germany

The susceptibilities of 430 Campylobacter jejuni strains and 79 C. coli strains to six antimicrobial agents were tested and analyzed. The two sets of strains originated from retail market chicken and turkey samples and from humans, respectively, in Berlin, Germany. Two groups of isolates, one dating from 1991 and the other dating from 2001-2002, were tested. Of the Campylobacter sp. isolates recovered from humans in 2001-2002, 45.1% were resistant to ciprofloxacin, 37.8% were resistant to tetracycline, 12.8% were resistant to ampicillin, and 50.0% were resistant to trimethoprim-sulfamethoxazole. All isolates were susceptible to gentamicin, while the overall rate of resistance to erythromycin was 6.1%. During the 10 years between the two sampling times, the rates of resistance to ciprofloxacin (P<0.001), ampicillin (P=0.035), and tetracycline (P=0.01) increased significantly among strains isolated from humans. Furthermore, among human C. coli strains the rate of resistance to erythromycin rose from 7.1% in 1991 to 29.4% in 2001-2002. In comparison, Campylobacter sp. isolates from poultry already had high rates of resistance in 1991. Different rates of resistance to tetracycline among isolates from chickens and turkeys suggested the development of resistance during antimicrobial treatment in food animals. Thus, discrepancies in the antimicrobial resistance rates among Campylobacter isolates originating from poultry and humans support the hypothesis that at least some of the resistant Campylobacter strains causing infection in humans come from sources other than poultry products.

Comparison of broth microdilution, E Test, and agar dilution methods for antibiotic susceptibility testing of Campylobacter jejuni and Campylobacter coli

A standardized broth microdilution method was compared to the E test and an agar dilution method for the antimicrobial susceptibility testing of Campylobacter jejuni and C. coli isolates. A group of 47 human clinical isolates, 37 isolates from retail poultry, and 29 isolates from living turkeys (total, 113 isolates) was included in the study. These encompassed 92 C. jejuni and 21 C. coli strains. The MICs of six antimicrobial agents were determined by the broth microdilution and E test methods, and the strains of human origin were additionally tested by the agar dilution method. In general, broth microdilution MICs agreed within 1 log(2) MIC increment with 90.0% of E test results and 78.7% of agar dilution test results. The agar dilution method gave much lower gentamicin MICs than the broth microdilution method, but the data were significantly (P < 0.01) correlated and there was 100% agreement in the sensitivities and specificities in the comparison of the tests. The broth microdilution method had the highest sensitivity for analysis of the susceptibilities of Campylobacter to nalidixic acid and trimethoprim-sulfamethoxazole. The MICs of ciprofloxacin and erythromycin complied numerically by all three methods. The classification of the results and the correlation of the data demonstrated a high degree of agreement. All methods were equally suitable for the testing of the sensitivity of Campylobacter to tetracycline. Thus, the broth microdilution method appears to be an easy and reliable method for determination of the MICs of antibiotics for C. jejuni and C. coli, and it may offer an interesting alternative to MIC determination by the agar dilution technique or the E test.

Helicobacter winghamensis sp. nov., a novel Helicobacter sp. isolated from patients with gastroenteritis

From 1997 to 1999 seven isolates of Campylobacter-like organisms from five patients that were exhibiting symptoms of gastroenteritis, including fever, stomach malaise, and diarrhea, were investigated. The organisms were isolated from stool samples and found to exhibit a diverse colony morphology; hence multiple isolates were submitted from one of the patients. All isolates were found to be identical. The organisms were catalase, urease, alkaline phosphatase, and nitrate negative but oxidase and indoxyl acetate positive. They grew at 37 degrees C but not at 42 degrees C, and three of the isolates from two different patients were sensitive to nalidixic acid and cephalothin. Full 16S rRNA sequence analysis not only grouped these organisms within the Helicobacter genus but also differentiated them from previously identified Helicobacter species. The closest relative by phylogenetic analysis was Helicobacter sp. flexispira taxon 1. Electron microscopy showed that these isolates had one or two bipolar flagella; however, the periplasmic fibers, a characteristic of the known Helicobacter sp. flexispira taxa, were not observed. The present isolates also lacked a flagellar sheath, a trait shared with four other Helicobacter spp., H. canadensis, H. mesocricetorum, H. pullorum, and H. rodentium. On the basis of the unique phenotypic properties of these isolates and 16S rRNA sequence analysis, we propose the classification of a new Helicobacter species, Helicobacter winghamensis sp. nov.

Differentiation of clinical Helicobacter pullorum isolates from related Helicobacter and Campylobacter species

BACKGROUND

Helicobacter pullorum, first detected in the liver and intestinal contents of poultry, was defined as a new species in 1994. This organism has since been isolated from humans with gastroenteritis. Phenotypic as well as genotypic methods have been used to identify H. pullorum associated with cases of human disease.

MATERIALS AND METHODS

Clinical isolates were submitted for identification to the National Laboratory for Enteric Pathogens by Provincial Public Health Laboratories within Canada. Phenotypic characterization was conducted using a variety of growth and biochemical tests including oxidase, catalase, indoxyl acetate, H2S production in triple sugar iron (TSI) agar, antimicrobial susceptibility testing, and fatty acid analysis. Genotypic identification was performed using a polymerase chain reaction-restriction fragment-length polymorphism (PCR-RFLP) analysis of a 1-kb fragment of the Helicobacter 16S rRNA gene.

RESULTS

During the last 7 years (1993-1999) a total of 11 isolates of H. pullorum were detected from patients with gastroenteritis for inclusion in this study. Typically, these isolates were oxidase and catalase positive, produced optimal growth at 42 degrees C, and produced H2S in TSI. Of these 11 isolates, 1 showed DNase activity, while another did not produce H2S in TSI, and only 2 showed tolerance to 1% bile. Antimicrobial susceptibility assays indicated that 6 of the 11 strains were resistant to nalidixic acid. The fatty acid profiles of the isolates were similar to each other and provided a distinguishing profile from the other related species. Genetically identical and distinct species-specific restriction fragment-length polymorphism (RFLP) patterns were produced using the restriction enzymes Bsr I and Dde I.

CONCLUSION

Phenotypic and genotypic procedures were used to identify H. pullorum. Interspecies phenotypic variability was apparent and supported the use of a polyphasic approach for identification. Similarities to the more prominent human pathogens Campylobacter coli and C. lari were also noted. The use of a combination of phenotypic and, in particular, genotypic markers for H. pullorum should prove valuable both for epidemiological investigations and for the diagnosis of disease related to this emerging human pathogen.

Multiplex PCR for the identification of Arcobacter and differentiation of Arcobacter butzleri from other arcobacters

A multiplex polymerase chain reaction (PCR) assay to identify Arcobacter isolates and to distinguish A. butzleri from other arcobacters is described. The test uses two primer sets. Set I targets a section of the 16S rRNA genes of Arcobacter spp. Set II amplifies a portion of the 23S rRNA genes unique to A. butzleri. Specificity of the primer sets was evaluated using ATCC reference strains of A. butzleri, A. cryaerophilus, A. skirrowii, Bacteroides spp., Campylobacter spp., Helicobacter spp. and Wolinella succinogenes. Upon PCR amplification, all of the Arcobacter isolates yielded a 1223 bp product, whereas A. butzleri ATCC 49616 exhibited both a 1223 bp and a 686 bp product. No PCR product was observed for other closely related ATCC strains (n = 37). We next analyzed by multiplex PCR field strains of Arcobacter spp. (n = 108) which had been previously characterized to the species level by either DNA-DNA hybridization, dot blot hybridization, ribotyping or by serology. The 1223 bp multiplex PCR product identified all of the isolates as Arcobacter. The presence of both the 1223 and 686 bp amplicons identified 66 strains as A. butzleri. Speciation by multiplex PCR agreed with results obtained by the other methods. The multiplex PCR assay is specific, rapid and easy to interpret and, thus, will aid in elucidating the prevalence, epidemiology and zoonotic potential of Arcobacter.

Polyphasic taxonomy, a consensus approach to bacterial systematics

Over the last 25 years, a much broader range of taxonomic studies of bacteria has gradually replaced the former reliance upon morphological, physiological, and biochemical characterization. This polyphasic taxonomy takes into account all available phenotypic and genotypic data and integrates them in a consensus type of classification, framed in a general phylogeny derived from 16S rRNA sequence analysis. In some cases, the consensus classification is a compromise containing a minimum of contradictions. It is thought that the more parameters that will become available in the future, the more polyphasic classification will gain stability. In this review, the practice of polyphasic taxonomy is discussed for four groups of bacteria chosen for their relevance, complexity, or both: the genera Xanthomonas and Campylobacter, the lactic acid bacteria, and the family Comamonadaceae. An evaluation of our present insights, the conclusions derived from it, and the perspectives of polyphasic taxonomy are discussed, emphasizing the keystone role of the species. Taxonomists did not succeed in standardizing species delimitation by using percent DNA hybridization values. Together with the absence of another "gold standard" for species definition, this has an enormous repercussion on bacterial taxonomy. This problem is faced in polyphasic taxonomy, which does not depend on a theory, a hypothesis, or a set of rules, presenting a pragmatic approach to a consensus type of taxonomy, integrating all available data maximally. In the future, polyphasic taxonomy will have to cope with (i) enormous amounts of data, (ii) large numbers of strains, and (iii) data fusion (data aggregation), which will demand efficient and centralized data storage. In the future, taxonomic studies will require collaborative efforts by specialized laboratories even more than now is the case. Whether these future developments will guarantee a more stable consensus classification remains an open question.

Phenotypic and ribosomal RNA characterization of Arcobacter species isolated from porcine aborted fetuses

Aerotolerant organisms resembling Campylobacter, now designated as Arcobacter, have been described from aborted farm animals and from cases of human enteritis worldwide. The goals of this study were 1) to attempt to recover Arcobacter spp. from cases of porcine abortion, 2) to characterize these isolates by phenotype and ribotype, and 3) to compare the usefulness of ribotype and phenotype patterns for identifying Arcobacter butzleri and the DNA hybridization groups 1A and 1B of A. cryaerophilus. Isolates of Arcobacter spp. from North Carolina and Iowa were recovered from porcine tissues. In Iowa, Arcobacter spp. were recovered from 43% (13/30) of porcine abortion cases evaluated. Isolations were made from placenta (44%), kidney (44%), and stomach contents (12%), which were the only tissues examined. The most reliable biochemical tests for A. butzleri included growth in 1% glycine and in 1.5% NaCl, weak catalase activity, and resistance to cadmium chloride. Arcobacter cryaerophilus strains were characterized by strong catalase activity and sensitivity to cadmium chloride. The DNA hybridization groups 1A and 1B of A. cryaerophilus could not be distinguished by biochemical tests. This represents the first description of A. cryaerophilus DNA group 1A in animals within the United States.

Genotypic and phenotypic characterization of Helicobacter cinaedi and Helicobacter fennelliae strains isolated from humans and animals

By DNA-DNA hybridization, we classified 26 human strains, 4 dog and cat strains, and 4 hamster strains putatively identified as Helicobacter cinaedi as well as 2 human strains and 2 animal strains of Helicobacter fennelliae. All but one human strain belonged to the same hybridization group as the type strain of H. cinaedi. The animal strains also appeared to belong to this hybridization group. Both human strains of H. fennelliae were shown to be H. fennelliae by DNA-DNA hybridization, but both animal strains were less than 15% related to the type strain. All strains were also characterized by plasmid profiles and ribotyping. Plasmids were found in 23% of the human strains, 100% of the hamster strains, and 33% of the dog and cat strains. Human strains were essentially identical by ribotyping, but were clearly differentiated from the hamster and dog and cat strains. Some strains may be difficult to culture on primary isolation; we found that our strains grew well on anaerobic CDC agar, brucella agar, and tryptic soy agar II. Our H. cinaedi and H. fennelliae strains differed from those previously described because some were resistant to cephalothin: some H. cinaedi strains were also resistant to nalidixic acid. All isolates were also characterized by antimicrobial susceptibility testing. We found that human strains of H. cinaedi were more resistant to clindamycin and erythromycin than were animal isolates; 19% of the human strains were resistant to ciprofloxacin. Therefore, we recommend that antimicrobial susceptibility results be obtained before initiating therapy for H. cinaedi and H. fennelliae infections.

Arcobacter-specific and Arcobacter butzleri-specific 16S rRNA-based DNA probes

The genus Arcobacter encompasses gram-negative, aerotolerant, spiral-shaped bacteria formerly designated Campylobacter cryaerophila. Two genus-specific 16S rRNA-based oligonucleotide DNA probes (23-mer and 27-mer) were developed. The probes hybridized with strains of Arcobacter butzleri (n = 58), Arcobacter cryaerophilus (n = 19), and Arcobacter skirrowii (n = 17). The probes did not cross-react with any of the reference strains of Campylobacter, Helicobacter, including "Flexispira rappini," or Wolinella. The 27-mer hybridized with 61 Arcobacter spp. field isolates originating from late-term aborted porcine (n = 54) and equine (n = 2) fetuses and humans with enteritis (n = 5). The species of Arcobacter isolates (n = 56) recovered from aborted livestock fetuses were determined by ribotyping and were as follows: A. cryaerophilus group 1A (11 of 56; 20%), A. cryaerophilus group 1B (37 of 56; 66%), A. butzleri (5 of 56; 9%), and unknown (3 of 56; 5%). The five human field strains were identified as A. butzleri. A species-specific DNA probe (24-mer) for A. butzleri was also developed since there is evidence that this organism may be a human pathogen. This probe hybridized with previously characterized strains of A. butzleri (n = 58), with 10 field strains identified as A. butzleri by ribotyping and with 2 strains having an indeterminate ribotype. The A. butzleri-specific probe did not cross-react with strains of A. skirrowii (n = 17) and A. cryaerophilus (n = 19).

Comparison of three rapid methods, tributyrine, 4-methylumbelliferyl butyrate, and indoxyl acetate, for rapid identification of Moraxella catarrhalis

Moraxella catarrhalis can easily be differentiated from other oxidase-positive, gram-negative cocci with tributyrine, 4-methylumbelliferyl butyrate, or indoxyl acetate. All M. catarrhalis give positive reactions, and all Neisseria spp. give negative reactions. The 4-methylumbelliferyl butyrate tube test and indoxyl acetate strip test provide same-day identification of M. catarrhalis isolates.

Three supplementary diagnostic tests for Campylobacter species and related organisms

We analyzed 307 recent clinical isolates and reference strains of Campylobacter spp., Helicobacter spp., and Arcobacter spp. for arylsulfatase and pyrazinamidase activities and susceptibility to polymyxin B. All isolates studied were identified by DNA dot hybridization prior to testing. Campylobacter concisus, C. sputorum, and Helicobacter fennelliae were positive for arylsulfatase. C. jejuni, C. coli, C. lari, C. upsaliensis, and C. concisus were positive for pyrazinamidase. Only Helicobacter spp. were resistant to polymyxin B. C. fetus subsp. fetus, C. hyointestinalis, C. mucosalis, and Arcobacter spp. were negative in all three tests. The tests were simple to perform and read, and with the exception of C. sputorum biovars, all isolates within a species gave consistently positive or negative results in all the assays. These three phenotypic tests may help refine current methods for phenotypic identification of Campylobacter spp. and related organisms in a reference laboratory setting.

Pulsed-field gel electrophoresis for epidemiologic studies of Campylobacter hyointestinalis isolates

Campylobacter hyointestinalis was isolated from five members of the same family who had previously consumed raw milk. Pulsed-field gel electrophoresis of genomic DNAs from the five strains, after digestion with restriction endonuclease SalI, revealed that three strains had identical genome patterns and therefore appeared to be related, whereas the other two had completely different genome patterns and appeared to be unrelated. We report here for the first time the isolation of C. hyointestinalis from family members who had consumed raw milk. Our study also demonstrates the usefulness of pulsed-field gel electrophoresis for epidemiologic studies of this unusual campylobacter.

Campylobacter butzleri sp. nov. isolated from humans and animals with diarrheal illness

Seventy-eight aerotolerant Campylobacter isolates were characterized phenotypically and by DNA hybridization (hydroxyapatite method at 50 and 65 degrees C). Two DNA relatedness groups were found. (i) Sixty-four strains belonged to aerotolerant Campylobacter DNA hybridization group 2. These organisms were isolated from humans, primarily with diarrheal illness, and animals on several continents. Strains were aerotolerant at 30 and 36 degrees C and catalase negative or weakly catalase positive, grew in media containing glycine and on MacConkey agar, were susceptible to nalidixic acid, and were resistant to cephalothin. The name Campylobacter butzleri sp. nov. is proposed for this group. (ii) DNA hybridization group 1 consisted of the type strain of Campylobacter cryaerophila and 13 additional strains isolated from 10 animals outside the United States and from three humans within the United States. This group was genetically diverse; five strains were closely related to the type strain of C. cryaerophila (DNA hybridization group 1A), and eight strains were more closely related to one another (DNA hybridization group 1B). Strains in DNA hybridization group 1B were phenotypically diverse, with two of eight strains resembling C. cryaerophila. The seven strains from DNA hybridization groups 1A and 1B which resembled C. cryaerophila and the C. cryaerophila type strain were aerotolerant only at 30 degrees C and catalase positive, did not grow in glycine or on MacConkey agar, were generally susceptible to nalidixic acid, and were resistant to cephalothin. The remaining six strains of DNA hybridization group 1B phenotypically resembled C. butzleri; however, they were generally catalase positive and susceptible to nalidixic acid and cephalothin. DNA hybridization group 1B is not designated as a separate species at this time since it cannot, with certainty, be separated genetically from C. cryaerophila or phenotypically from C. butzleri.