Development of a simple and rapid method based on polymerase chain reaction-based restriction fragment length polymorphism analysis to differentiate Helicobacter, Campylobacter, and Arcobacter species

A Review on the Prevalence of Arcobacter in Aquatic Environments

Arcobacter is an emerging pathogen that is associated with human and animal diseases. Since its first introduction in 1991, 33 Arcobacter species have been identified. Studies have reported that with the presence of Arcobacter in environmental water bodies, animals, and humans, a possibility of its transmission via water and food makes it a potential waterborne and foodborne pathogen. Therefore, this review article focuses on the general characteristics of Arcobacter, including its pathogenicity, antimicrobial resistance, methods of detection by cultivation and molecular techniques, and its presence in water, fecal samples, and animal products worldwide. These detection methods include conventional culture methods, and rapid and accurate Arcobacter identification at the species level, using quantitative polymerase chain reaction (qPCR) and multiplex PCR. Arcobacter has been identified worldwide from feces of various hosts, such as humans, cattle, pigs, sheep, horses, dogs, poultry, and swine, and also from meat, dairy products, carcasses, buccal cavity, and cloacal swabs. Furthermore, Arcobacter has been detected in groundwater, river water, wastewater (influent and effluent), canals, treated drinking water, spring water, and seawater. Hence, we propose that understanding the prevalence of Arcobacter in environmental water and fecal-source samples and its infection of humans and animals will contribute to a better strategy to control and prevent the survival and growth of the bacteria.

Arcobacter butzleri: Up-to-date taxonomy, ecology, and pathogenicity of an emerging pathogen

Arcobacter butzleri, recently emended to the Aliarcobacter butzleri comb. nov., is an emerging pathogen causing enteritis, severe diarrhea, septicaemia, and bacteraemia in humans and enteritis, stillbirth, and abortion in animals. Since its recognition as emerging pathogen on 2002, advancements have been made in elucidating its pathogenicity and epidemiology, also thanks to advent of genomics, which, moreover, contributed in emending its taxonomy. In this review, we provide an overview of the up-to-date taxonomy, ecology, and pathogenicity of this emerging pathogen. Moreover, the implication of A. butzleri in the safety of foods is pinpointed, and culture-dependent and independent detection, identification, and typing methods as well as strategies to control and prevent the survival and growth of this pathogen are provided.

Arcobacter: an emerging food-borne zoonotic pathogen, its public health concerns and advances in diagnosis and control - a comprehensive review

Arcobacter has emerged as an important food-borne zoonotic pathogen, causing sometimes serious infections in humans and animals. Newer species of Arcobacter are being incessantly emerging (presently 25 species have been identified) with novel information on the evolutionary mechanisms and genetic diversity among different Arcobacter species. These have been reported from chickens, domestic animals (cattle, pigs, sheep, horses, dogs), reptiles (lizards, snakes and chelonians), meat (poultry, pork, goat, lamb, beef, rabbit), vegetables and from humans in different countries. Arcobacters are implicated as causative agents of diarrhea, mastitis and abortion in animals, while causing bacteremia, endocarditis, peritonitis, gastroenteritis and diarrhea in humans. Three species including A. butzleri, A. cryaerophilus and A. skirrowii are predominantly associated with clinical conditions. Arcobacters are primarily transmitted through contaminated food and water sources. Identification of Arcobacter by biochemical tests is difficult and isolation remains the gold standard method. Current diagnostic advances have provided various molecular methods for efficient detection and differentiation of the Arcobacters at genus and species level. To overcome the emerging antibiotic resistance problem there is an essential need to explore the potential of novel and alternative therapies. Strengthening of the diagnostic aspects is also suggested as in most cases Arcobacters goes unnoticed and hence the exact epidemiological status remains uncertain. This review updates the current knowledge and many aspects of this important food-borne pathogen, namely etiology, evolution and emergence, genetic diversity, epidemiology, the disease in animals and humans, public health concerns, and advances in its diagnosis, prevention and control.

Helicobacter pylori identification: a diagnostic/confirmatory method for evaluation

The Helicobacter pylori extra gastric reservoir is probably the oral cavity. In order to evaluate the presence of this bacterium in patients with periodontitis and suspicious microbial cultures, saliva was collected from these and non-periodontitis subjects. PCRs targeting 16S rRNA gene and a 860 bp specific region were performed, and digested with the restriction enzyme DdeI. We observed that the PCR-RFLP approach augments the accuracy from 26.2 % (16/61), found in the PCR-based results, to 42.6 % (26/61), which is an excellent indicator for the establishment of this low-cost procedure as a diagnostic/confirmatory method for H. pylori evaluation.

Performance of five molecular methods for monitoring Arcobacter spp

Background

Bacteria belonging to the Arcobacter genus are emerging enteropathogens and potential zoonotic agents. Their taxonomy has evolved very rapidly, and there are presently 18 recorded species. The prevalence of species belonging to Arcobacter is underestimated because of the limitations of currently available methods for species identification.

The aim of this study was to compare the performance of five PCR based methods that target regions of 16S rRNA, 23S rRNA or gyrA genes to identify Arcobacter species, and to review previous results reported in the literature using these methods.

Results

The five tested methods were found not to be reliable. They misidentified between 16.8% and 67.4% of the studied strains; this was dependent upon the target regions of the tested genes. The worst results obtained were for the identification of Arcobacter cryaerophilus and Arcobacter butzleri when the 23S rRNA gene was used as the target. These species were confused with many non-targeted species.

Conclusion

Our results suggest that the known diversity of Arcobacter spp. in different environments could be expanded if reliable identification methods are applied in future studies.

Updated 16S rRNA-RFLP method for the identification of all currently characterised Arcobacter spp

BACKGROUND

Arcobacter spp. (family Campylobacteraceae) are ubiquitous zoonotic bacteria that are being increasingly recognised as a threat to human health. A previously published 16S rRNA-RFLP Arcobacter spp. identification method produced specific RFLP patterns for the six species described at that time, using a single endonuclease (MseI). The number of characterised Arcobacter species has since risen to 17. The aim of the present study was to update the 16S rRNA-RFLP identification method to include all currently characterised species of Arcobacter.

RESULTS

Digestion of the 16S rRNA gene with the endonuclease MseI produced clear, distinctive patterns for 10 of the 17 species, while the remaining species shared a common or very similar RFLP pattern. Subsequent digestion of the 16S rRNA gene from these species with the endonucleases MnlI and/or BfaI generated species-specific RFLP patterns.

CONCLUSIONS

16S rRNA-RFLP analysis identified 17 Arcobacter spp. using either polyacrylamide or agarose gel electrophoresis. Microheterogeneities within the 16S rRNA gene, which interfered with the RFLP identification, were also documented for the first time in this genus, particularly in strains of Arcobacter cryaerophilus isolated from animal faeces and aborted foetuses.

Taxonomy, epidemiology, and clinical relevance of the genus Arcobacter

The genus Arcobacter, defined almost 20 years ago from members of the genus Campylobacter, has become increasingly important because its members are being considered emergent enteropathogens and/or potential zoonotic agents. Over recent years information that is relevant for microbiologists, especially those working in the medical and veterinary fields and in the food safety sector, has accumulated. Recently, the genus has been enlarged with several new species. The complete genomes of Arcobacter butzleri and Arcobacter nitrofigilis are available, with the former revealing diverse pathways characteristic of free-living microbes and virulence genes homologous to those of Campylobacter. The first multilocus sequence typing analysis showed a great diversity of sequence types, with no association with specific hosts or geographical regions. Advances in detection and identification techniques, mostly based on molecular methods, have been made. These microbes have been associated with water outbreaks and with indicators of fecal pollution, with food products and water as the suspected routes of transmission. This review updates this knowledge and provides the most recent data on the taxonomy, species diversity, methods of detection, and identification of these microbes as well as on their virulence potential and implication in human and animal diseases.

Rapid and accurate detection of Arcobacter contamination in commercial chicken products and wastewater samples by real-time polymerase chain reaction

An SYBR Green real-time polymerase chain reaction (PCR) assay was developed for Arcobacter detection in food and wastewater samples. The assay was applied to 36 chicken and 33 wastewater samples, and the results were compared with those obtained for conventional PCR, multiplex PCR, and culture isolation. Isolates were identified by multiplex PCR and restriction fragment length polymorphism analysis of PCR-amplified DNA fragment, and typed by randomly amplified polymorphic DNA. Arcobacter sp. was detected in 25 of the 26 chicken carcasses (96%) and in 4 of the 10 liver samples (40%) by real-time PCR. Twenty-five chicken samples were positive also by conventional PCR, but in most of them the detection was only possible after 48-h enrichment. Arcobacter butzleri was the most frequently detected species. Twenty-four Arcobacter isolates were obtained from chicken samples, where A. butzleri is the only identified species. All the wastewater samples (100%) were positive for Arcobacter sp. by real-time PCR without enrichment. A. butzleri and Arcobacter cryaerophilus were detected by multiplex PCR. Fifteen samples were found to be positive by culture. Thirty-six isolates were obtained; all of them were identified as A. butzleri by multiplex PCR. However, by PCR-restriction fragment length polymorphism, 34 were identified as A. butzleri, 1 as A. cryaerophilus, and another 1 as Arcobacter skirrowii. A great genetic heterogeneity was observed by randomly amplified polymorphic DNA-PCR profiling. The real-time PCR assay developed in this work showed better detection levels than conventional PCR, together with shorter times of testing samples. Therefore, it could be used as a rapid and accurate instrument for monitoring Arcobacter contamination levels in food and water samples.

A new 16S rDNA-RFLP method for the discrimination of the accepted species of Arcobacter

The genus Arcobacter that includes some species of clinical interest has been recently enlarged with the addition of several new species. The available molecular techniques for the characterization of Arcobacter spp. are unable to identify all the species included in this genus. We have developed a 16S rDNA-RFLP method able to separate the currently accepted 6 species of Arcobacter, including the 2 hybridization groups of Arcobacter cryaerophilus. The method based on the use of a pair of primers and of the endonuclease MseI has been validated using 12 reference strains (including the type strains) and 75 fresh isolates. All isolates tested produced species-specific RFLP patterns. This easy-to-perform method allows a fast and reliable recognition of the members of this complex genus.