Maria José Figueras

Taxonomy, Epidemiology, and Clinical Relevance of the Genus Arcobacter

SUMMARY 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.

Cronobacter condimenti sp. nov., isolated from spiced meat, and Cronobacter universalis sp. nov., a species designation for Cronobacter sp. genomospecies 1, recovered from a leg infection, water and food ingredients.

A re-evaluation of the taxonomic position of five strains, one assigned to Cronobacter sakazakii (strain 1330(T), isolated from spiced meat purchased in Slovakia), two previously assigned to Cronobacter genomospecies 1 (strains NCTC 9529(T) and 731, isolated from water and a leg infection, respectively) and two previously assigned to Cronobacter turicensis (strains 96 and 1435, isolated from onion powder and rye flour, respectively) was carried out. The analysis included phenotypic characterization, 16S rRNA gene sequencing and multilocus sequence analysis (MLSA) of seven housekeeping genes (atpD, fusA, glnS, gltB, gyrB, infB, ppsA; 3036 bp). 16S rRNA gene sequence analysis and MLSA showed that strain 1330(T) formed an independent phylogenetic lineage in the MLSA, with Cronobacter dublinensis LMG 23823(T) as the closest neighbour. DNA-DNA reassociation and phenotypic analysis revealed that strain 1330(T) represented a novel species, for which the name Cronobacter condimenti sp. nov. is proposed (type strain 1330(T) = CECT 7863(T) = LMG 26250(T)). Strains NCTC 9529(T), 731, 96 and 1435 clustered together within an independent phylogenetic lineage, with C. turicensis LMG 23827(T) as the closest neighbour in the MLSA. DNA-DNA reassociation and phenotypic analysis confirmed that these strains represent a novel species, for which the name Cronobacter universalis sp. nov. is proposed (type strain NCTC 9529(T) = CECT 7864(T) = LMG 26249(T)).

Aeromonas spp. and traveler's diarrhea: clinical features and antimicrobial resistance.

Traveler’s diarrhea is the most common health problem of international travelers. We determined the prevalence of Aeromonas spp. associated with traveler’s diarrhea and analyzed the geographic distribution, clinical features, and antimicrobial susceptibility. Aeromonas spp. were isolated as a cause of traveler’s diarrhea in 18 (2%) of 863 patients. A. veronii biotype sobria was isolated in nine patients, A. caviae in seven patients, and A. jandai and A. hydrophila in one patient each. Aeromonas spp. were isolated with a similar prevalence in Africa, Latin America, and Asia. Watery and persistent diarrhea, fever, and abdominal cramps were common complaints. All strains were resistant to ampicillin; showed variable resistance to chloramphenicol, tetracycline, and cotrimoxazole; and were susceptible to cefotaxime, ciprofloxacin, and nalidixic acid. The persistence of symptoms made antimicrobial treatment necessary.

Fast detection of Salmonella Infantis with carbon nanotube field effect transistors

In this paper we report a fast, sensitive and label-free biosensor for the selective determination of Salmonella Infantis. It is based on a field effect transistor (FET) in which a network of single-walled carbon nantotubes (SWCNTs) acts as the conductor channel. Anti-Salmonella antibodies were adsorbed onto the SWCNTs and subsequently the SWCNTs were protected with Tween 20 to prevent the non-specific binding of other bacteria or proteins. Our FET devices were exposed to increasing concentrations of S. Infantis and were able to detect at least 100 cfu/mL in 1h. To evaluate the selectivity of our FET devices, Streptococcus pyogenes and Shigella sonnei were tested as potential competing bacteria for Salmonella. At a concentration of 500 cfu/mL, neither Streptococcus nor Shigella interfered with the detection of Salmonella. Therefore, these devices could be used as useful label-free platforms to detect S. Infantis and, by using the suitable antibody, other bacteria or viruses.

Presence of Arcobacter spp. in environmental waters correlates with high levels of fecal pollution

We investigated the presence of Arcobacter spp. in 205 water samples of freshwater, seawater and sewage in Spain. These bacteria were present in 55.1% of the samples (113/205) and were significantly associated for the first time with bacterial indicators of fecal pollution. The dominant species in the positive samples was Arcobacter butzleri (94%) followed by Arcobacter cryaerophilus (30%) and Arcobacter skirrowii (1.8%).

Extended method for discrimination of Aeromonas spp. by 16S rDNA RFLP analysis

A previously described molecular method, based on 16S rDNA RFLP analysis, for the identification of Aeromonas spp. was unable to separate the species Aeromonas salmonicida, Aeromonas bestiarum and the recently described Aeromonas popoffii. In this study, the method has been extended with endonucleases AIwNI and PstI for the identification of these species. A molecular frame for the identification of all known Aeromonas spp. is presented.

Arcobacter mytili sp. nov., an indoxyl acetate-hydrolysis-negative bacterium isolated from mussels

Three Arcobacter isolates, recovered from mussels (genus Mytilus), and one isolate from brackish water in Catalonia (north-east Spain) showed a novel pattern using a recently described identification method for members of the genus Arcobacter, 16S rRNA gene RFLP. Enterobacterial repetitive intergenic consensus PCR fingerprinting demonstrated that the three isolates from mussels belonged to two genotypes and that the fourth isolate from water belonged to a third genotype. Analysis of the 16S rRNA and rpoB gene sequences showed that the new isolates formed a separate lineage within the genus Arcobacter. This was also confirmed by the low DNA-DNA relatedness values (16-30 %) of the isolates with the type strains of recognized Arcobacter species. Hydrolysis of indoxyl acetate, a characteristic trait for all species of the genus Arcobacter, was negative for the novel isolates. The susceptibility of the novel isolates to cefoperazone, together with the lack of urease production and nitrate reduction, further enabled them to be differentiated from recognized Arcobacter species based on physiological characteristics. Genotypic and phenotypic characteristics indicated that the new isolates represent a novel species of the genus Arcobacter, for which the name Arcobacter mytili sp. nov. is proposed, with the type strain F2075(T) (=CECT 7386(T) =LMG 24559(T)). The DNA G+C content of strain F2075(T) was 26.9 mol%.

Prevalence of Arcobacter in Meat and Shellfish

Arcobacter is considered an emergent foodborne and waterborne enteropathogen. However, its prevalence in foods of animal origin is only partially known, because most studies have been concentrated on poultry, pork, and beef, and methods applied do not allow identification of all currently accepted Arcobacter species. We investigated the prevalence of Arcobacter in 203 food samples, 119 samples of seven different types of meats and 84 samples of four types of shellfish. Isolates were identified in parallel by using a published multiplex PCR method and a recently described 16S rDNA restriction fragment length polymorphism method that allows all currently accepted Arcobacter species to be characterized. The global prevalence of Arcobacter was 32%; it was highest in clams (5 of 5 samples, 100%) and chicken (9 of 14 samples, 64.3%) followed by pork (9 of 17 samples, 53.0%), mussels (23 of 56 samples, 41.1%), and duck meat (2 of 5 samples, 40.0%). Turkey meat and beef had a similar recovery rate (10 of 30 samples, 33.3%; 5 of 16 samples, 31.3%; respectively), and rabbit meat had the lowest rate (1 of 10 samples, 10.0%). No arcobacters were found in oysters, frozen shrimps, or sausages. This food survey is the first in which five of the seven accepted Arcobacter species have been isolated. Arcobacter butzleri was the most prevalent species (63.0% of isolates) followed by Arcobacter cryaerophilus (26.6%), Arcobacter mytili (4.7%), Arcobacter skirrowii (3.1%), and Arcobacter nitrofigilis (3.1%). Three (4.7%) of the isolates were classified as belonging to three potentially new phylogenetic lines. Our results indicated that Arcobacter species are widely distributed in the food products studied.

Distribution of virulence genes in clinical and environmental isolates of Aeromonas spp.

The distribution and phenotypic activity of the genes encoding for serine protease, glycerophospholipid-cholesterol acyltransferase, lipases, aerolysin/hemolysin and DNases were investigated in 234 isolates identified by 16S rDNA-RFLP representing all the species of Aeromonas. The former three genes were found to be highly conserved among the genus. Aerolysin/hemolysin and DNase genes and β-hemolytic activity were significantly more frequent in clinical than in environmental isolates. Aerolysin/hemolysin and serine protease genes were present in all β-hemolytic strains supporting serine protease as possibly important for the activation of the former gene. The high prevalence of virulence factors in clinical isolates indicates that they may play a role in the mechanisms of pathogenesis of these microorganisms.

Diversity and pathogenecity of Vibrio species in cultured bivalve molluscs.

Shellfish production is seriously affected by bacterial pathogens that cause high losses in hatcheries and in the aquaculture sector. A number of Vibrio species are considered important pathogens and have provoked severe mortality outbreaks. The pathologies caused by vibrios in bivalves have been described since the 1960s; however, over recent years, successive episodes of high mortality have been recorded due to these microorganisms. The present work provides an updated overview of the different studies performed in relation with the diversity of Vibrio spp. associated to bivalves. Special attention is given to the main Vibrio diseases and implicated species affecting the different life stages of cultured bivalves.