Global Distribution and Prevalence of Arcobacter in Food and Water

Antimicrobial susceptibility, virulence potential and sequence types associated with Arcobacter strains recovered from human faeces

PURPOSE

The genus Arcobacter includes bacteria that are considered emergent pathogens because they can produce infections in humans and animals. The most common symptoms are bloody and non-bloody persistent diarrhea but cases with abdominal cramps without diarrhea or asymptomatic cases have also been described as well as cases with bacteremia. The objective was to characterize Arcobacter clinical strains isolated from the faeces of patients from three Spanish hospitals.

METHODOLOGY

We have characterized 28 clinical strains (27 of A. butzleri and one of A. cryaerophilus) isolated from faeces, analysing their epidemiological relationship using the multilocus sequence typing (MLST) approach and screening them for their antibiotic susceptibility and for the presence of virulence genes.Results/Key findings. Typing results showed that only one of the 28 identified sequence types (i.e. ST 2) was already present in the MLST database. The other 27 STs constituted new records because they included new alleles for five of the seven genes or new combinations of known alleles of the seven genes. All strains were positive for the ciaB virulence gene and sensitive to tetracycline. However, 7.4 % of the A. butzleri and A. cryaerophilus strains showed resistance to ciprofloxacin.

CONCLUSION

The fact that epidemiological unrelated strains show the same ST indicates that other techniques with higher resolution should be developed to effectively recognize the infection source. Resistance to ciprofloxacin, one of the antibiotics recommended for the treatment of Arcobacter intestinal infections, demonstrated in 10.7 % of the strains, indicates the importance of selecting the most appropriate effective treatment.

Isolation, molecular identification and quinolone-susceptibility testing of Arcobacter spp. isolated from fresh vegetables in Spain

Some species of the Arcobacter genus are considered emerging foodborne and waterborne enteropathogens. However, the presence of Arcobacter spp. in vegetables very little is known, because most studies have focused on foods of animal origin. On the other hand, quinolones are considered as first-line drugs for the treatment of infection by campylobacteria in human patients, but few data are currently available about the resistance levels to these antibiotics among Arcobacter species. Therefore, the aim of this study was to investigate the presence and diversity of arcobacters isolated from fresh vegetables such as lettuces, spinaches, chards and cabbages. Resistance to quinolones of the isolates was also investigated. One hundred fresh vegetables samples purchased from seven local retail markets in Valencia (Spain) during eight months were analysed. The study included 41 lettuces, 21 spinaches, 34 chards and 4 cabbages. Samples were analysed by culture and by molecular methods before and after enrichment. By culture, 17 out of 100 analysed samples were Arcobacter positive and twenty-five isolates were obtained from them. Direct detection by PCR was low, with only 4% Arcobacter spp. positive samples. This percentage increased considerably, up 20%, after 48 h enrichment. By polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), 17 out of the 25 isolates were identified as A. butzleri and 8 as A. cryaerophilus. Only two A. butzleri isolates showed resistance to levofloxacin and ciprofloxacin. The sequencing of a fragment of the QRDR region of the gyrA gene from the quinolones-resistant isolates revealed the presence of a mutation in position 254 of this gene (C-T transition). This study is the first report about the presence of pathogenic species of Arcobacter spp. in chards and cabbages and confirms that fresh vegetables can act as transmission vehicle to humans. Moreover, the presence of A. butzleri quinolone resistant in vegetables could pose a potential public health risk.

Comparative isolation and genetic diversity of Arcobacter sp. from fish and the coastal environment

Arcobacter species are emerging food-borne and water-borne human pathogens associated mostly with food animals and their environment. The present study was aimed to isolate Arcobacter species from fish, shellfish and coastal water samples using two methods and to determine their genetic diversity. Of 201 samples of fish, shellfish and water samples analysed, 66 (32·8%) samples showed the presence of Arcobacter DNA from both Arcobacter enrichment broth and Bolton broth. Arcobacters were isolated from 58 (87·8%) and 38 (57·5%) of Arcobacter DNA-positive samples using Arcobacter blood agar and Preston blood agar, respectively. Arcobacter sp. identified by biochemical tests were further analysed by a genus-specific PCR, followed by a multiplex-PCR and 16S rRNA-RFLP. From both the methods, four different Arcobacter species namely Arcobacter butzleri, Arcobacter skirrowii, Arcobacter mytili and Arcobacter defluvii were isolated, of which A. butzleri was the predominant species. Enterobacterial repetitive intergenic consensus (ERIC)-PCR fingerprint analysis revealed that the arcobacters isolated in this study were genetically very diverse and no specific genotype was found associated with a specific source (seafood or water). Since pathogenic arcobacters are not known to be natural inhabitants of coastal marine environment, identifying the sources of contamination will be crucial for effective management of this problem.

SIGNIFICANCE AND IMPACT OF THE STUDY

Arcobacter sp. are emerging food- and water-borne human pathogens. In this study, comparison of two selective media suggested Arcobacter blood agar to be more efficient in yielding Arcobacter sp. from seafood. Furthermore, the isolation of Arcobacter sp. such as Arcobacter butzleri, A. skirrowii, A. mytili and A. defluvii from seafood suggests diverse sources of contamination of seafood by Arcobacter sp. Analysis of enterobacterial repetitive intergenic consensus sequence-PCR patterns of A. butzleri showed high genetic diversity and lack of clonality among the isolates. Arcobacter contamination of seafood is an emerging issue both from seafood safety and seafood trade point of view.

Pathogens of Food Animals: Sources, Characteristics, Human Risk, and Methods of Detection

Pathogens associated with food production (livestock) animals come in many forms causing a multitude of disease for humans. For the purpose of this review, these infectious agents can be divided into three broad categories: those that are associated with bacterial disease, those that are associated with viruses, and those that are parasitic in nature. The goal of this chapter is to provide the reader with an overview of the most common pathogens that cause disease in humans through exposure via the food chain and the consequence of this exposure as well as risk and detection methods. We have also included a collection of unusual pathogens that although rare have still caused disease, and their recognition is warranted in light of emerging and reemerging diseases. These provide the reader an understanding of where the next big outbreak could occur. The influence of the global economy, the movement of people, and food makes understanding production animal-associated disease paramount to being able to address new diseases as they arise.

Effects of Organic Amendments on Microbiota Associated with the Culex nigripalpus Mosquito Vector of the Saint Louis Encephalitis and West Nile Viruses

Mosquito microbiota provide important physiological and ecological attributes to mosquitoes, including an impact on their susceptibility to pathogens, fitness, and sensitivity to mosquito control agents. Culex nigripalpus mosquito populations transmit various pathogens, including the Saint Louis and West Nile viruses, and proliferate in nutrient-rich environments, such as in wastewater treatment wetlands. Our study examined whether increases in nutrients within larval mosquito developmental habitats impact microbial communities associated with C. nigripalpus mosquitoes. We characterized the effects of organic enrichments on microbiomes associated with C. nigripalpus mosquitoes and identified potential bacterial microbiota that will be further investigated for whether they alter mosquito life history traits and for their potential role in the development of microbial-based control strategies.

Pollution from nutrients in aquatic habitats has been linked to increases in disease vectors, including mosquitoes and other pestiferous insects. One possibility is that changes in mosquito microbiomes are impacted by nutrient enrichments and that these changes affect various traits, including larval development, susceptibility to larval control agents, and susceptibility of the adult mosquitoes to pathogens. We tested this hypothesis using field mesocosms supplemented with low- and high-organic-nutrient regimens and then sampled microbial communities associated with the naturally colonizing Culex nigripalpus mosquito vector. By high-throughput sequencing of 16S rRNA gene sequences, we found no significant differences in overall microbial communities associated with sampled mosquitoes, despite detecting discernible differences in environmental variables, including pH, dissolved oxygen, and nutrient amendments. Nevertheless, indicator species analysis revealed that members of the Clostridiales were significantly associated with mosquitoes that originated from high-nutrient enrichments. In contrast, members of the Burkholderiales were associated with mosquitoes from the low-nutrient enrichment. High bacterial variability associated with the life stages of the C. nigripalpus was largely unaffected by levels of nutrient enrichments that impacted larval microbial resources, including bacteria, ciliates, and flagellates in the larval environments.

IMPORTANCE Mosquito microbiota provide important physiological and ecological attributes to mosquitoes, including an impact on their susceptibility to pathogens, fitness, and sensitivity to mosquito control agents. Culex nigripalpus mosquito populations transmit various pathogens, including the Saint Louis and West Nile viruses, and proliferate in nutrient-rich environments, such as in wastewater treatment wetlands. Our study examined whether increases in nutrients within larval mosquito developmental habitats impact microbial communities associated with C. nigripalpus mosquitoes. We characterized the effects of organic enrichments on microbiomes associated with C. nigripalpus mosquitoes and identified potential bacterial microbiota that will be further investigated for whether they alter mosquito life history traits and for their potential role in the development of microbial-based control strategies.

Detection, Identification, and Antimicrobial Susceptibility of Arcobacter spp. Isolated from Shellfish in Spain

This work aimed to determine the presence of Arcobacter spp. in shellfish and to determine its susceptibility to quinolones. One hundred samples (41 mussels, 37 clams, and 22 cockles) were purchased from different local retail shops in Valencia, Spain, from September 2013 to June 2015. All samples were analyzed simultaneously by culture, after an enrichment step, and by polymerase chain reaction (PCR), directly and after enrichment. The susceptibility to levofloxacin and ciprofloxacin of the isolates was tested using the disk-diffusion test and E-test strips method. To clarify the mechanism of quinolone resistance, a fragment of the quinolone resistance-determining region of the gyrA gene was sequenced. Thirty-seven samples were positive and 49 isolates were obtained by culture, and Arcobacter spp. DNA was detected in 32% of the samples by PCR. However, after 48-h enrichment, the number of positive samples increased, and 68 of the 100 samples yielded the specific Arcobacter spp. PCR product. In addition, 49 isolates were identified by PCR-restriction fragment length polymorphism. The most commonly found species was Arcobacter butzleri (25 isolates, 51.03%) followed by Arcobacter cryaerophilus (19 isolates, 38.77%) and Arcobacter defluvii (5 isolates, 10.20%). Only three isolates of A. butzleri were resistant to both antibiotics. A mutation C to T transition in the position 254 of the gyrA gene was present in the three resistant isolates. This study confirms that pathogenic arcobacters are frequently found in edible shellfish samples. Moreover, this is the first time that A. butzleri and A. cryaerophilus have been isolated from cockles.

Microbial community structure in a full-scale anaerobic treatment plant during start-up and first year of operation revealed by high-throughput 16S rRNA gene amplicon sequencing

High-throughput amplicon sequencing of six biomass samples from a full-scale anaerobic reactor at a Norwegian wood and pulp factory using Biothane Biobed Expanded Granular Sludge Bed (EGSB) technology during start-up and first year of operation was performed. A total of 106,166 16S rRNA gene sequences (V3-V5 region) were obtained. The number of operational taxonomic units (OTUs) ranged from 595 to 2472, and a total of 38 different phyla and 143 families were observed. The predominant phyla were Bacteroidetes, Chloroflexi, Firmicutes, Proteobacteria, and Spirochaetes. A more diverse microbial community was observed in the inoculum biomass coming from an Upflow Anaerobic Sludge Blanket (USAB) reactor, reflecting an adaptation of the inoculum diversity to the specific conditions of the new reactor. In addition, no taxa classified as obligate pathogens were identified and potentially opportunistic pathogens were absent or observed in low abundances. No Legionella bacteria were identified by traditional culture-based and molecular methods.

Enhanced recovery of Arcobacter spp. using NaCl in culture media and re-assessment of the traits of Arcobacter marinus and Arcobacter halophilus isolated from marine water and shellfish

The genus Arcobacter is a relatively poorly known group of bacteria, and the number of new species and sequences from non-culturable strains has increased considerably in recent years. This study investigates whether using media that contain NaCl might help to improve the recovery of Arcobacter spp. from marine environments. To this aim, 62 water and shellfish samples were analysed in parallel, with both a commonly used culture method (enrichment in Arcobacter-CAT broth followed by culture on Blood Agar) and a new one that supplements the Arcobacter-CAT enrichment broth with 2.5% NaCl (w/v) followed by culturing on Marine Agar. The new method yielded ca. 40% more positive samples and provided a higher diversity of known (11 vs. 7) and unknown (7 vs. 2) Arcobacter species. Among the 11 known species recovered, Arcobacter marinus and Arcobacter halophilus were isolated only by this new method. No more strains of these species have been isolated since their original descriptions, both of which were based only on a single strain. In view of that, the phenotypic characteristics of these species are re-evaluated in the present study, using the new strains. Strains of A. halophilus had the same phenotypic profile as the type strain. However, some strains of A. marinus differed from the type strain in that they did not hydrolyse indoxyl-acetate, becoming, therefore, the first Arcobacter species to show a varying ability to hydrolyse indoxyl-acetate. This study shows to what extent a simple variation to the culture media can have a big influence on positive samples and on the community of species recovered.

Occurrence of emerging food-borne pathogenic Arcobacter spp. isolated from pre-cut (ready-to-eat) vegetables

Given that changes in consumer food behaviours have led to an increase in the demand for pre-cut ready-to-eat (RTE) vegetables, and that few data are currently available on the occurrence of Arcobacter spp. in such foods, the aim of the present study was to assess the occurrence of Arcobacter spp. that carry virulence-associated genes on pre-cut RTE vegetables, using cultural and molecular methods. Arcobacter was detected using biomolecular identification methods in 44/160 (27.5%) of the samples, of which 40/44 (90.9%) isolates corresponded to A. butzleri and 4/44 (9.1%) to A. cryaerophilus. Studying the incidence of 9 virulence-associated genes revealed the widespread distribution of these genes among the Arcobacter isolates tested. The results obtained in our research provided plenty of information on the health risks associated with the direct consumption of raw vegetables, and highlight the need to implement further studies at each level of the production chain, in order to obtain further information to help protect human health.

Neighborhood diversity of potentially pathogenic bacteria in drinking water from the city of Maroua, Cameroon

This study examined the spatial variation of potential gastrointestinal pathogens within drinking water sources and home storage containers in four neighborhoods in Maroua, Cameroon. Samples were collected from source (n = 28) and home containers (n = 60) in each study neighborhood. Pathogen contamination was assessed using quantitative polymerase chain reaction, targeting Campylobacter spp., Shiga toxin producing Escherichia coli (virulence genes, stx1 and stx2), and Salmonella spp. Microbial source tracking (MST) targeted three different host-specific markers: HF183 (human), Rum2Bac (ruminant) and GFD (poultry) to identify contamination sources. Staphylococcus aureus and the tetracycline-resistance gene (tetQ) were assessed to measure human hand contact and presence of antibiotic-resistant bacteria. Pathogen/MST levels were compared statistically and spatially, and neighborhood variation was compared with previously collected demographic information. All the test fecal markers and pathogens (except Arcobacter) were detected in home and source samples. Two neighborhoods tested positive for most pathogens/MST while the others only tested positive for one or two. Spatial variation of pathogens/MST existed between sources, storage containers, and neighborhoods. Differing population density and ethno-economic characteristics could potentially explain variation. Future research should explore the influence of demographic and ethno-economic factors on water quality during microbial risk assessments in urban Africa.

Isolation and identification of Arcobacter species from environmental and drinking water samples

Water plays an important role in the transmission of Arcobacter spp. to animals and humans. The aim of this study was to isolate and characterize Arcobacter spp. from 115 different water samples (66 sewage, 25 rivers, 16 spring water, and 8 drinking water) in Izmir, Turkey. In total, 41 samples (35.7 %) were found positive for Arcobacter spp. by the genus-specific PCR. Arcobacter butzleri was detected in 39 out of 115 samples (33.9 %) including 24 sewage, 13 rivers, and 2 spring water. The remaining Arcobacter spp. (n = 2) isolates could not be identified by m-PCR and 16S rRNA gene sequencing. Based on the phenotypic characterization, most of the Arcobacter species (87.8 %) indicated weak catalase activity. In addition, there were differences in phenotypic patterns among isolated species during growth at 37 °C under microaerobic and aerobic conditions, in the presence of 2 % (39/41) and 3.5 % (32/41) NaCl and 0.04 % TTC (39/41) and on MacConkey agar (38/41). The results of this study indicated that environmental water samples are common sources for Arcobacter spp. Therefore, effective control measures should be taken to protect human health.