Arcobacter: pathogenic potential and importance as zoonotic agent

Die Gattung Arcobacter (A.) gehört zur Familie der Campylobactereaceae und umfasst gegenwärtig 29 verschiedene Spezies. Insbesondere A. butzleri, A. cryaerophilus und A. skirrowii werden als potentielle Zoonoseerreger diskutiert, die vermutlich durch den Verzehr von kontaminierten Lebensmitteln oder Wasser übertragen werden und beim Menschen gastrointestinale Infektionen verursachen können. Durch das Fehlen einer standardisierten Routinediagnostik für Arcobacter wird die tatsächliche Prävalenz beim Menschen womöglich unterschätzt und auch über deren Virulenzpotential sowie antimikrobielle Empfindlichkeit ist bisher wenig bekannt. Ziel dieser Studie war es, die Prävalenz von Arcobacter in humanen Stuhlproben zu untersuchen und die isolierten Stämme zu charakterisieren. Insgesamt wurden 4636 Stuhlproben mittels selektiven Kulturverfahren auf Arcobacter untersucht. Verdächtige Isolate wurden durch multiplex PCR sowie anschließender rpoB-Sequenzierung identifiziert und durch ERIC-PCR genotypisiert. Das Vorhandensein zehn putativer Virulenzgene wurde mittels PCR untersucht und die Zytotoxizität gegenüber HT-29/B6-Zellen im WST-Assay bestimmt. Mittels Gradientendiffusionstest wurde außerdem die Empfindlichkeit gegenüber sechs Antibiotika ermittelt. Die Stuhlproben ambulanter (n = 3884) bzw. stationärer (n = 752) Patienten zeigten eine Belastung mit Arcobacter spp. von 0,85 bzw. 0,40 %. A. butzleri wurde dabei am häufigsten detektiert (n=24), gefolgt von A. cryaerophilus (n=10) und A. lanthieri (n=2). Die Genotypisierung der Isolate ergab eine hohe genetische Vielfalt innerhalb der Spezies. Die Prävalenz an putativen Virulenzgenen war in A. butzleri- sowie A. lanthieri-Stämmen höher als in A. cryaerophilus. Beide A. lanthieri-Isolate wiesen zusätzlich die Cytolethal-Distending Toxin kodierenden Gene auf. Während die A. butzleri- sowie beide A. lanthieri-Stämme überwiegend starke zytotoxische Effekte in vitro induzierten, zeigten die A. cryaerophilus-Stämme kaum zytotoxisches Potential. Die Arcobacter-Isolate waren ausgesprochen sensibel gegenüber Ciprofloxacin, während für Azithromycin und Ampicillin erhöhte MHKs festgestellt wurden. Diese Studie zeigt das Vorkommen von Arcobacter in humanen Stuhlproben, eine hohe Prävalenz putativer Virulenzgene bei A. butzleri und A. lanthieri sowie prominente zytotoxische Effekte in vitro. Das Vorhandensein der CDT-Gene in A. lanthieri, aber nicht A. butzleri, könnte auf unterschiedliche Pathomechanismen hindeuten. Darüber hinaus könnte Ciprofloxacin als antimikrobielle Behandlung schwerer Arcobacter-Infektionen vorgeschlagen werden. Es sind jedoch weitere Studien zur Epidemiologie und Pathogenese erforderlich, um das potenzielle Risiko von Arcobacter als Zoonoseerreger abschließend zu bewerten.The genus Arcobacter (A.) belongs to the family Campylobactereaceae and currently comprises 29 different species. Particularly, the three species A. butzleri, A. cryaerophilus und A. skirrowii are discussed as potential zoonotic pathogens, likely to be transmitted through consumption of contaminated food or water and causing gastrointestinal infections in humans. Since there is no standardized routine diagnostic for Arcobacter spp., data about their true prevalence in humans are lacking. Furthermore, the knowledge regarding their virulence potential as well as their antimicrobial susceptibility is still limited. Therefore, this study aimed at investigating the prevalence of Arcobacter in human stool samples and characterizing the isolated strains. Overall, a total of 4636 specimen were collected and screened for Arcobacter by selective cultural procedure. Suspicious isolates were identified using multiplex PCR followed by rpoB sequencing and genotyped by ERIC-PCR. Furthermore, the presence of ten putative virulence genes was investigated using PCR and cytotoxic effects on the human intestinal cell line HT-29/B6 were determined applying the WST-assay. Moreover, susceptibility to six antibiotics was investigated using the gradient strip diffusion method. Arcobacter spp. were detected in 0,85 % and 0,40 % of specimens obtained from 3884 outpatients and 752 hospitalized patients, respectively. Among the 36 Arcobacter isolates A. butzleri was the most prevalent species (n=24) followed by A. cryaerophilus (n=10) and A. lanthieri (n=2). Genotyping of the isolates revealed a high genetic diversity within the species. The incidence of the analyzed virulence genes was higher in A. butzleri and A. lanthieri isolates compared to A. cryaerophilus. Additionally, the three cytolethal distending toxin (CDT) genes were detectable in both A. lanthieri isolates. Cytotoxic effects were observed for most of A. butzleri and both A. lanthieri strains, while A. cryaerophilus strains induced less cytotoxic effects on HT-29/B6 cells. Antimicrobial susceptibility testing of Arcobacter isolates revealed high susceptibility to ciprofloxacin, whereas elevated MIC values were detected for azithromycin and ampicillin. This study demonstrates the occurrence of Arcobacter in human stool samples, high prevalence of putative virulence genes in A. butzleri as well as A. lanthieri isolates and prominent cytotoxic effects of these strains in vitro. The presence of CDT genes in A. lanthieri but not A. butzleri could suggest different pathomechanisms. Furthermore, ciprofloxacin could be proposed as antimicrobial treatment of severe Arcobacter infections. However, further studies regarding epidemiology and pathogenesis are needed to finally assess the potential risk of Arcobacter as zoonotic pathogens

Prevalence, antimicrobial susceptibility and virulence gene profiles of Arcobacter species isolated from human stool samples, foods of animal origin, ready-to-eat salad mixes and environmental water

Background Members of the genus Arcobacter are considered as emerging zoonotic food and waterborne pathogens that cause gastroenteritis and bacteremia in humans. However, the potential risk that Arcobacter species pose to public health remains unassessed in various countries, including Baltic states. Therefore, the aim of this study was to determine the prevalence, antimicrobial susceptibility and presence of putative virulence genes of Arcobacter isolates recovered from humans, food products and environmental water in Lithuania. Results A total of 1862 samples were collected and examined from 2018 to 2020 in the city of Kaunas. Overall, 11.2% (n = 208) of the samples were positive for the presence of Arcobacter spp. The highest prevalence was detected in chicken meat (36%), followed by environmental water (28.1%), raw cow milk (25%), ready-to-eat salad mixes (7.1%) and human stool (1.7%). A. butzleri was the most frequently isolated species (n = 192; 92.3%), followed by A. cryaerophilus (n = 16; 7.7%). Arcobacter spp. antimicrobial susceptibility testing revealed unimodally distributed aggregated minimal inhibitory concentrations (MICs) for gentamicin, tetracycline, ciprofloxacin, ampicillin and erythromycin. However, a bimodal distribution for azithromycin was found with 96.2% of determined MICs above the epidemiological cut-off value (ECOFF) defined for Campylobacter jejuni (0.25 µg/ml). Majority of the Arcobacter isolates (n = 187; 89.9%) showed high susceptibility to ciprofloxacin with MICs below or equal to the ECOFF value of 0.5 µg/ml. The putative virulence genes cadF (100%), ciaB (100%), cj1349 (99%), tlyA (99%), mviN (97.9%) and pldA (95.8%) were the predominant genes detected among A. butzleri isolates. In contrast, the mviN and ciaB genes were present in all, whereas cj1349 (12.5%), tlyA (25%) and hecA (12.5%) were only detected in few A. cryaerophilus isolates. Conclusions Our results demonstrate that food products and environmental water in Lithuania are frequently contaminated with Arcobacter spp. that carry multiple putative virulence genes. Furthermore, A. butzleri were isolated from 1.7% of inpatients. Fluoroquinolones and aminoglycosides were found to be more effective against Arcobacter in comparison to other antimicrobial agents. However, further studies are needed to determine the pathogenic mechanisms and factors that facilitate the spread of Arcobacter infections

Glutathione reductase-catalyzed cascade of redox reactions to bioactivate potent antimalarial 1,4-naphthoquinones--a new strategy to combat malarial parasites.

Our work on targeting redox equilibria of malarial parasites propagating in red blood cells has led to the selection of six 1,4-naphthoquinones, which are active at nanomolar concentrations against the human pathogen Plasmodium falciparum in culture and against Plasmodium berghei in infected mice. With respect to safety, the compounds do not trigger hemolysis or other signs of toxicity in mice. Concerning the antimalarial mode of action, we propose that the lead benzyl naphthoquinones are initially oxidized at the benzylic chain to benzoyl naphthoquinones in a heme-catalyzed reaction within the digestive acidic vesicles of the parasite. The major putative benzoyl metabolites were then found to function as redox cyclers: (i) in their oxidized form, the benzoyl metabolites are reduced by NADPH in glutathione reductase-catalyzed reactions within the cytosols of infected red blood cells; (ii) in their reduced forms, these benzoyl metabolites can convert methemoglobin, the major nutrient of the parasite, to indigestible hemoglobin. Studies on a fluorinated suicide-substrate indicate as well that the glutathione reductase-catalyzed bioactivation of naphthoquinones is essential for the observed antimalarial activity. In conclusion, the antimalarial naphthoquinones are suggested to perturb the major redox equilibria of the targeted infected red blood cells, which might be removed by macrophages. This results in development arrest and death of the malaria parasite at the trophozoite stage

Prevalence and antimicrobial susceptibility of Arcobacter species in human stool samples derived from out- and inpatients: the prospective German Arcobacter prevalence study Arcopath

Background: Arcobacter species, particularly A. butzleri, but also A. cryaerophilus constitute emerging pathogens causing gastroenteritis in humans. However, isolation of Arcobacter may often fail during routine diagnostic procedures due to the lack of standard protocols. Furthermore, defined breakpoints for the interpretation of antimicrobial susceptibilities of Arcobacter are missing. Hence, reliable epidemiological data of human Arcobacter infections are scarce and lacking for Germany. We therefore performed a 13-month prospective Arcobacter prevalence study in German patients. Results: A total of 4636 human stool samples was included and Arcobacter spp. were identified from 0.85% of specimens in 3884 outpatients and from 0.40% of specimens in 752 hospitalized patients. Overall, A. butzleri was the most prevalent species (n = 24; 67%), followed by A. cryaerophilus (n = 10; 28%) and A. lanthieri (n = 2; 6%). Whereas A. butzleri, A. cryaerophilus and A. lanthieri were identified in outpatients, only A. butzleri could be isolated from samples of hospitalized patients. Antimicrobial susceptibility testing of Arcobacter isolates revealed high susceptibilities to ciprofloxacin, whereas bimodal distributions of MICs were observed for azithromycin and ampicillin. Conclusions: In summary, Arcobacter including A. butzleri, A. cryaerophilus and A. lanthieri could be isolated in 0.85% of German outpatients and ciprofloxacin rather than other antibiotics might be appropriate for antibiotic treatment of infections. Further epidemiological studies are needed, however, to provide a sufficient risk assessment of Arcobacter infections in humans

Geological evidence for historical and older earthquakes and tsunamis along the Nankai Trough, Japan

In the wake of the devastating 2011 Tōhoku earthquake and tsunami, the Central Disaster Management Council of the Japanese Cabinet Office issued new guidance for assessing seismic hazards in Japan. Before 2011, seismic hazard assessment relied on source models developed from knowledge of a small number of well-documented historical earthquakes. Less well-known historical earthquakes, including the AD 869 Jōgan Sanriku earthquake, were largely disregarded as their seismic intensities or tsunami heights could not be reconciled with the chosen seismic sources. Following the unexpectedly large size of the Tōhoku earthquake, the Cabinet Office advocated renewed investigation of earthquake and tsunami occurrence over historical and longer timescales, with a particular focus on defining the largest possible magnitudes. The new guidelines pay close attention to the Nankai Trough, the subduction zone where the Philippine Sea Plate dives beneath the Eurasian Plate. The Nankai Trough faces the densely populated and highly industrialised coastline of south central Japan and harbours a widely-known seismic gap along its eastern Tōkai segment. A full-length rupture of the Nankai Trough, including the Tōkai segment, could produce an earthquake with a magnitude approaching that of the 2011 event, with tsunami travel times to the closest shorelines of less than 30 minutes. We review geological evidence for historical and older earthquakes and tsunamis along the Nankai Trough. This evidence comes from a wide variety of sources, including uplifted marine terraces, subsided marshes, liquefaction features, turbidites and tsunami deposits in coastal lakes and lowlands. Examining papers published before and after 2011, we investigate the impact of the new Cabinet Office guidelines on attempts to understand the magnitude and recurrence of these events. Additionally, we introduce the Belgian Science Policy Office funded QuakeRecNankai project, a collaboration aiming to supplement existing records by generating a long time series of earthquake and tsunami recurrence from sites at the eastern end of the Nankai Trough. The project uses a diverse range of geophysical, sedimentological, geochemical and microfossil approaches to investigate records of Holocene paleotsunamis in and around Lake Hamana and records of seismic shaking from the Fuji Five Lakes.QuakeRecNanka