Aeromonas spp. are ubiquitous bacteria that cause diseases in fish and other aquatic animals. They are the natural inhabitants of different aquatic environments, such as freshwater, brackishwater and ...marinewater. Extrinsic stressors, such as crowding, unhygienic handling, poor water quality, polluted feeding and inadequate nutrition, can predispose fish to Aeromonas infection. In ornamental fish, motile Aeromonas spp. are known as aetiological agents of motile aeromonad infections, which cause significant mortality in fish and economic loss in the ornamental fish industry. The existence of different virulence factors leads to the virulence potential of motile Aeromonas spp. There are several antimicrobials used to treat bacterial infections in ornamental fish. However, the extensive use of antimicrobials in the ornamental fish industry causes multidrug resistance. This article reviewed a multitude of virulence factors that are related to the ornamental fish‐borne Aeromonas pathogenicity and the antimicrobial resistance determinants related to the multidrug resistance phenotypes of motile Aeromonas spp. in ornamental fish.
Significance and Impact of the Study: Aeromonas spp. are Gram‐negative bacteria, which are omnipresent in different aquatic environments. The virulence factors and antimicrobial resistance of ornamental fish‐borne motile Aeromonas spp. were identified in various studies. The information on virulence factors and multidrug resistance of ornamental fish‐borne motile Aeromonas spp. will help to understand virulence potential and multidrug resistance phenotypes, and highlight the possible treatment for motile aeromonad infections in the ornamental fish industry.
Aims
Yesso scallop (Patinopecten yessoensis) is a popular seafood in Korea. Aeromonas spp., well‐known pathogenic bacteria, has been reported in some molluscan shellfish, but it has not been studied ...in scallops so far. Therefore, we aimed to isolate, identify and characterize the Aeromonas spp. isolated from marketed Yesso scallops to estimate their potential risk to public health.
Methods and Results
Thirty‐two Aeromonas spp. including A. hydrophila (n = 13), A. salmonicida (n = 11), A. media (n = 3), A. caviae (n = 2), A. veronii (n = 2) and A. enteropelogenes (n = 1) were isolated from 105 marketed scallops and tested for phenotypic pathogenicity, virulence genes and antimicrobial susceptibility. Mean total bacterial count of scallop meat was 1·34 × 104 CFU per gram. Slime production and lipase tests were positive in 97% of the isolates while DNase, protease, gelatinase, phospholipase and haemolysis were shown by 88, 88, 81, 88 and 72% of the isolates respectively. Eleven virulence genes were detected among Aeromonas spp. (act (75%), alt (59%), ast (47%), aerA (78%), lip (59%), ahyB (94%), ser (75%), hlyA (75%), fla (64%), gcat (84%) and ascV (23%)), and exu was negative in all isolates. Aeromonas hydrophila and A. salmonicida harboured ≥7 virulence genes and positive for enterotoxin genes, act, alt and ast. All the isolates were multidrug resistant and 100% resistant to ampicillin, colistin, vancomycin and cephalothin. Also, 30, 31, 20, 21, 29, 24, 27 and 27 of the isolates were resistant to piperacillin, clindamycin, erythromycin, nalidixic acid, imipenem, meropenem, trimethoprim‐sulfamethoxazole and rifampicin respectively.
Conclusions
It is obvious with our results that the Aeromonas spp. isolated from Yesso scallops are highly virulent and potentially pathogenic, whereas the multidrug resistance further expedite their importance.
Significance and Impact of the Study
To our knowledge, this is the first study reporting Aeromonas spp. in scallop. This implies that not only the common varieties like oysters, but other bivalves can also harbour potentially pathogenic aeromonads which may have impacts on consumer health.
Aeromonas spp. are associated with seafood‐related outbreaks worldwide. In seafood industry, shellfish play a major role in global seafood production. With this emerging trend of shellfish ...consumption, shellfish‐related bacterial infections are being reported frequently. Aeromonas spp. are natural contaminants found in shellfish. Although 36 species have been identified, some species including Aeromonas hydrophila, Aeromonas caviae and Aeromonas veronii biotype sobria have dragged major attention as foodborne pathogenic bacteria. The ability to elaborate a variety of virulence factors of Aeromonas spp. contributes to the pathogenic activities. Also, emerging antimicrobial resistance in Aeromonas spp. has become a huge challenge in seafood industry. Furthermore, multidrug resistance increases the risk of consumer health. Studies have supplied pieces of evidence about the emerging health risk of Aeromonas spp. isolated from seafood. Therefore, the present review was intended to highlight the prevalence, virulence and antimicrobial resistance of Aeromonas spp. isolated from various types of shellfish.
Significance and Impact of the Study: This study summarized the virulence and antimicrobial resistance in Aeromonas spp. associated with shellfish. This review may help to increase consumer awareness about the possible health risk of shellfish borne Aeromonas spp. infections and emphasizes the importance of alternative or regulated control methods in Aeromonas spp. infections as most of the antimicrobials are less effective against them.
Aims
Manila clam (Ruditapes philippinarum) is one of the most popular seafood in Korea, owing to their unique taste and nutritional value. This study aimed to disclose the antibiotic and heavy metal ...resistance characteristics of Aeromonas spp. isolated from marketed Manila clam in Korea.
Methods and results
A total of 36 Aeromonas spp. strains were isolated and subjected to two tests: an antibiotic disk diffusion test to determine their resistance to antibiotics, and a broth dilution test to determine their resistance to heavy metals. PCR‐based amplification was performed to detect the resistance genes. A high level of resistance to ampicillin (100%) and cephalothin (89%) was observed, while 42, 39, 36 and 36% of the isolates were resistant to oxytetracycline, imipenem, nalidixic acid and tetracycline respectively. In addition, among the tested heavy metals, cadmium (Cd) recorded the highest resistance rate (61%), followed by chromium (Cr) (50%), lead (Pb) (47%) and copper (Cu) (37%). However, mercury (Hg) resistance was not observed. PCRs revealed the occurrence of blaTEM, blaSHV, blaCTX‐M, qnrS, tetB, tetE, aac(6′)‐Ib, strA‐strB and intI1 genes among 100, 31, 31, 78, 78, 89, 25, 50 and 72% of the isolates respectively. Moreover, heavy metal resistance genes, copA, merA and czcA were detected in 25, 47 and 61% of the isolates respectively.
Conclusions
The results suggest the importance of multi‐drug and heavy metal‐resistant aeromonads in Manila clam to assess the consumer safety and public health.
Significance and Impact of the Study
This study is the first to elaborate on the importance of multi‐drug and heavy metal‐resistant aeromonads in Manila clam. Particularly, the presence of extended‐spectrum‐β‐lactamase genes and other antibiotic resistance genes intensifies the possible health risks and may complicate therapeutic treatments upon infection, while heavy metal resistance suggests possible heavy metal exposure.
Aeromonas spp. are opportunistic pathogenic bacteria associated with a multitude of diseases in ornamental fish. In this study, virulence properties and antibiotic resistance patterns of 43 Aeromonas ...strains isolated from 46 zebrafish were investigated. The isolates were identified as Aeromonas veronii biovar veronii (n = 26), A. veronii biovar sobria (n = 3), Aeromonas hydrophila (n = 8), A. caviae (n = 3), Aeromonas enteropelogenes (n = 2) and Aeromonas dhakensis (n = 1) by gyrB gene sequencing. The sequence divergence within and between the species ranged from 0–5·80% and 4·90–8·00%. Each species formed a distinct group in a neighbour‐joining phylogenetic tree. The lipase production, biofilm formation, DNase activity, gelatinase production, caseinase production and β‐hemolysis were phenotypically observed in 34 (79·07%), 33 (74·74%), 30 (69·77%), 25 (58·14%), 22 (51·18%) and 21 (48·84%) isolates. The virulence genes were detected by polymerase chain reaction (PCR) in following frequencies‐ aer (86·05%), hlyA (83·72%), gcaT (83·72%), lip (72·09%), act (67·44%), fla (65·12%), ascV (58·14%), ast (55·81%), ser (41·86%), ahyB (39·53%) and alt (25·58%). Every isolate was resistant to at least four antibiotics in disk diffusion test. The multiple antibiotic resistance (MAR) index values ranged from 0·22–0·50 among the isolates. Our study suggests that zebrafish can be a potential reservoir of virulent and multi‐drug resistant Aeromonas spp.
Significance and Impact of the Study
Aeromonas spp. are Gram‐negative and facultative anaerobic bacteria which are ubiquitous in aquatic environments. Virulence properties and antibiotic resistance of ornamental fish‐borne Aeromonas spp. are poorly understood. The virulence factors as well as multiple antibiotic resistance profiles of zebrafish‐borne Aeromonas spp. were characterized for the first time in Korea. Most of the isolates were positive for phenotypic virulence traits and harboured several virulence genes revealing the virulence potential of zebrafish‐borne Aeromonas spp. Additionally, the high multiple antibiotic resistance (MAR) index values displayed by the isolates highlight the necessity of responsible use of antibiotics in the ornamental fish industry.
Significance and Impact of the Study: Aeromonas spp. are Gram‐negative and facultative anaerobic bacteria which are ubiquitous in aquatic environments. Virulence properties and antibiotic resistance of ornamental fish‐borne Aeromonas spp. are poorly understood. The virulence factors as well as multiple antibiotic resistance profiles of zebrafish‐borne Aeromonas spp. were characterized for the first time in Korea. Most of the isolates were positive for phenotypic virulence traits and harboured several virulence genes revealing the virulence potential of zebrafish‐borne Aeromonas spp. Additionally, the high multiple antibiotic resistance (MAR) index values displayed by the isolates highlight the necessity of responsible use of antibiotics in the ornamental fish industry.
ZnO-nanowire gas sensors were fabricated by a selective growth of nanowires on patterned Au catalysts thus forming nanowire air bridges or ‘
nanobridges’ between two Pt pillar electrodes. The gas ...sensing properties of nanobridge gas sensors were demonstrated using a diluted NO
2. The response, as a function of temperature, was highest at 225
°C and was linearly increased with the concentration of NO
2 in the range of 0.5–3
ppm and then showed a sign of saturation. Our sensor showed higher response compared with different types of sensors including ZnO nanocrystals, Sn- and In-doped ZnO thin film, or ZnO nanowires. The enhanced response was attributed to the additional modulation of the sensor resistance due to potential barrier at nanowire/nanowire junctions as well as the surface depletion region of each nanowire. Also nanobridge structure enabled fast recovery behavior because desorbed gas molecules can be easily swept away from the surface of ZnO nanowire without re-adsorption.
Removal of damaged mitochondria is orchestrated by a pathway involving the PINK1 kinase and the PARKIN ubiquitin ligase. Ubiquitin chains assembled by PARKIN on the mitochondrial outer membrane ...recruit autophagy cargo receptors in complexes with TBK1 protein kinase. While TBK1 is known to phosphorylate cargo receptors to promote ubiquitin binding, it is unknown whether TBK1 phosphorylates other proteins to promote mitophagy. Using global quantitative proteomics, we identified S72 in RAB7A, a RAB previously linked with mitophagy, as a dynamic target of TBK1 upon mitochondrial depolarization. TBK1 directly phosphorylates RAB7A
, but not several other RABs known to be phosphorylated on the homologous residue by LRRK2, in vitro, and this modification requires PARKIN activity in vivo. Interaction proteomics using nonphosphorylatable and phosphomimetic RAB7A mutants revealed loss of association of RAB7A
with RAB GDP dissociation inhibitor and increased association with the DENN domain-containing heterodimer FLCN-FNIP1. FLCN-FNIP1 is recruited to damaged mitochondria, and this process is inhibited in cells expressing RAB7A
. Moreover, nonphosphorylatable RAB7A failed to support efficient mitophagy, as well as recruitment of ATG9A-positive vesicles to damaged mitochondria. These data reveal a novel function for TBK1 in mitophagy, which parallels that of LRRK2-mediated phosphorylation of the homologous site in distinct RABs to control membrane trafficking.
Summary
For the last several decades, antimicrobial compounds have been used to promote piglet growth at weaning through the prevention of subclinical and clinical disease. There are, however, ...increasing concerns in relation to the development of antibiotic‐resistant bacterial strains and the potential of these and associated resistance genes to impact on human health. As a consequence, European Union (EU) banned the use of antibiotics as growth promoters in swine and livestock production on 1 January 2006. Furthermore, minerals such as zinc (Zn) and copper (Cu) are not feasible alternatives/replacements to antibiotics because their excretion is a possible threat to the environment. Consequently, there is a need to develop feeding programs to serve as a means for controlling problems associated with the weaning transition without using antimicrobial compounds. This review, therefore, is focused on some of nutritional strategies that are known to improve structure and function of gastrointestinal tract and (or) promote post‐weaning growth with special emphasis on probiotics, prebiotics, organic acids, trace minerals and dietary protein source and level.
Hypoxia-inducible factor-1α (HIF-1α) is a transcription factor that has a central role in the regulation of tumour metabolism under hypoxic conditions. HIF-1α stimulates glycolytic energy production ...and promotes tumour growth. Sirtuins are NAD(+)-dependent protein deacetylases that regulate cellular metabolism in response to stress; however, their involvement in the hypoxic response remains unclear. In this study, it is shown that SIRT2-mediated deacetylation of HIF-1α regulates its stability in tumour cells. SIRT2 overexpression destabilized HIF-1α under hypoxic conditions, whereas HIF-1α protein levels were high in SIRT2-deficient cells. SIRT2 directly interacted with HIF-1α and deacetylated Lys709 of HIF-1α. Deacetylation of HIF-1α by SIRT2 resulted in increased binding affinity for prolyl hydroxylase 2, a key regulator of HIF-1α stability, and increased HIF-1α hydroxylation and ubiquitination. Moreover, a pharmacological agent that increased the intracellular NAD(+)/NADH ratio led to the degradation of HIF-1α by increasing SIRT2-mediated deacetylation and subsequent hydroxylation. These findings suggest that SIRT2-mediated HIF-1α deacetylation is critical for the destablization of HIF-1α and the hypoxic response of tumour cells.
Aeromonas spp. are Gram‐negative opportunistic bacteria which have been commonly associated with fish diseases. In this study, antibiogram, antimicrobial resistance genes and integrons of 43 ...zebrafish‐borne Aeromonas spp. were studied. The isolates were identified as six Aeromonas species (A. veronii biovar veronii (n = 26), A. veronii biovar sobria (n = 3), A. hydrophila (n = 8), A. caviae (n = 3), A. enteropelogenes (n = 2) and A. dhakensis (n = 1)). Antibiogram of the isolates indicated that most of them were resistant to amoxicillin (100·00%), nalidixic acid (100·00%), oxytetracycline (100·00%), ampicillin (93·02%), tetracycline (74·42%), rifampicin (67·44%) and imipenem (65·15%). Multiple antimicrobial resistance (MAR) index values ranged from 0·19–0·44 to 90·70% isolates showed multidrug resistance. PCR of antimicrobial resistance genes revealed that the tetracycline resistance gene (tetA) was the most predominant (67·44%) among the isolates. The qnrS (53·49%), tetB (30·23%), tetE (30·23%), qnrB (23·26%) and aac(6’)‐Ib‐cr (4·65%) genes were also detected. Class 1 integrase (IntI1) gene was found in 46·51% of the isolates. Two types of class 1 integron gene cassette profiles (qacG‐aadA6‐qacG and drfA1) were identified. The results showed that zebrafish‐borne aeromonads can harbour different types of antimicrobial resistance genes and class 1 integrons.
Significance and Impact of the Study
Aeromonas spp. are important pathogens found in diverse environments. Antimicrobial resistance genes and integrons of ornamental fish‐borne Aeromonas spp. are not well studied. The antibiogram, antimicrobial resistance genes and class 1 integrons of Aeromonas spp. isolated from zebrafish were characterized for the first time in Korea. The prevalence of tetracycline resistance genes, plasmid‐mediated quinolone resistance genes and class 1 integron gene cassettes were observed among the isolates. The qacG‐aadA6‐qacG gene cassette was identified for the first time in Aeromonas spp. The results suggest that the wise use of antimicrobials is necessary for the better management of the ornamental fish.
Significance and Impact of the Study:Aeromonas spp. are important pathogens found in diverse environments. Antimicrobial resistance genes and integrons of ornamental fish‐borne Aeromonas spp. are not well studied. The antibiogram, antimicrobial resistance genes and class 1 integrons of Aeromonas spp. isolated from zebrafish were characterized for the first time in Korea. The prevalence of tetracycline resistance genes, plasmid‐mediated quinolone resistance genes and class 1 integron gene cassettes were observed among the isolates. The qacG‐aadA6‐qacG gene cassette was identified for the first time in Aeromonas spp. The results suggest that the wise use of antimicrobials is necessary for the better management of the ornamental fish.
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