Bioassay and Whole-Genome Analysis of Bacillus velezensis FIO1408, a Biocontrol Agent Against Pathogenic Bacteria in Aquaculture
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Abstract.— Surveys undertaken on diseases caused by Vibrio spp. in Penaeus monodon from culture ponds of coastal Andhra Pradesh recorded the occurrence of five types of diseases: tail necrosis, shell disease, red disease, loose shell syndrome (LSS), and white gut disease (WGD). Among these, LSS, WGD, and red disease caused mass mortalities in shrimp culture ponds. Six species of Vibrio—V. harveyi , V. parahaemolyticus, V. alginolyticus, V. anguillarum , V. vulnificus , and V. splendidus —are associated with the diseased shrimp. The number of Vibrio spp. associated with each disease ranged from two to five. Additionally, shrimp with red disease had concurrent infections with white spot syndrome virus. Vibrio harveyi in the case of LSS and WGD, V. parahaemolyticus for red disease, and V. alginolyticus for shell disease are the major etiologcal agents. Differences occur in the degree of virulence of different species of Vibrio and also different isolates of the same species. Vibrio harveyi isolated from LSS shrimp is the most virulent. In general, all the Vibrio isolates from LSS shrimp tend to be more virulent as compared to their counterparts from other diseased shrimp. It is apparent that the degree of virulence of various Vibrio isolates depends on its source and the pond environmental conditions. Most of the Vibrio isolates showed susceptibility to oxytetracycline, norfloxacin, and ciprofloxacin. The luminous V. harveyi exhibited resistance to many antibiotics and susceptibility to only three drugs. Considering the emergence of antimicrobial resistant strains of Vibrio , the need for using probiotics in place of antibiotics for disease control is stressed.
Penaeus monodon
Vibrio harveyi
Vibrio alginolyticus
White spot syndrome
Bacterial disease
Vibrio Infections
Vibrio vulnificus
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This paper presents a feasibility study of using bacteriophage to detect penaeid shrimp luminous disease pathogen,Vibrio Harveyi.The results indicated that the Vibrio harveyi bacteriophage separated from shrimp hatchery showed a special phagocytosis on Vibrio harveyi.They could not infect and lyses certain bacteria such as Vibrio alginolyticus,Vibrio parahaemo-lyticus and photosynthetic bacteria,but could specially lyse the experimental Vibrio harveyi which were separated from the same hatchery.The appearance rate of engulfing bacteria spot is 80 percent.The appearance rate of engulfing spot showed a high correlativity with the shrimp luminous disease occurrence.The method can be used as a chief means of detecting Vibrio harveyi and diagnosing shrimp luminous disease pathogen.
Vibrio harveyi
Vibrio alginolyticus
Marine bacteriophage
Photobacterium
Bacterial disease
Vibrio vulnificus
Hatchery
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Vibrio alginolyticus
Bacterial disease
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A comparative study of virulence of P. aeruginosa strains PAO containing and not containing plasmids has been made. A number of plasmids which are present in strains PAO decrease their virulence for mice 3-7 times. The virulence-affecting plasmids considerably differ in their biological properties. Bacterial mutations rpm, selected as mutations stabilizing RP4 plasmid in PAO cells, have also been found to affect virulence of bacteria, decreasing its level several times. The introduction of plasmids into PAO cells carrying mutations rpm is not accompanied by decrease of virulence.
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strains of bacteria were isolated from diseased Penaeus monodon. Among them, two strains were found to be the main pathogens causing red body disease in cultured P.monodon, with a mortality of 70% and 90% respectively . Based on biochemical test results, these two strains were classfied as Aeromonas hydrophila and Vibrio parahemolyticus. The strain of A. hydrophila was very sensitive to doxycycinum, while the strain of V. parahemolyticus was very sensitive to norfloxacinum, erythromycinum, penicilin and doxycycinum.
Penaeus monodon
Strain (injury)
Bacterial disease
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The effects of temperature and pH on the expression of four virulence factors: hemolysin(AHH),aerolysin(AerA),outer membrane proteins(OMP) and adhesion(Aha),from Aeromonas hydrophila and on its pathogenicity are studied.The results show that the expression of these virulence factors from A.hydrophila is affected by temperature and pH in the media.All four virulence factors are highly expressed in A.hydrophila when being grown at 15 ℃,25 ℃ and 37 ℃ determined by RT-PCR.At 4 ℃,both AHH and AerA are still expressed,but neither OMP nor Aha was.All four virulence factors tested here are expressed in bacterial cells when being grown at pH 5.0 and pH 7.0.Only AHH expression is detected at pH 9.0.These results are supported by the results from the challenge experiments with crucian carp.In addition,the study shows that the pathogenicity of the bacteria is affected by the body temperature of fish.
Aerolysin
Hemolysin
Crucian carp
Virulence factor
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ABSTRACT Strains of Vibrio vulnificus , a marine bacterial species pathogenic for humans and eels, are divided into three biotypes, and those virulent for eels are classified as biotype 2. All biotype 2 strains possess one or more plasmids, which have been shown to harbor the biotype 2-specific DNA sequences. In this study we determined the DNA sequences of three biotype 2 plasmids: pR99 (68.4 kbp) in strain CECT4999 and pC4602-1 (56.6 kb) and pC4602-2 (66.9 kb) in strain CECT4602. Plasmid pC4602-2 showed 92% sequence identity with pR99. Curing of pR99 from strain CECT4999 resulted in loss of resistance to eel serum and virulence for eels but had no effect on the virulence for mice, an animal model, and resistance to human serum. Plasmids pC4602-2 and pR99 could be transferred to the plasmid-cured strain by conjugation in the presence of pC4602-1, which was self-transmissible, and acquisition of pC4602-2 restored the virulence of the cured strain for eels. Therefore, both pR99 and pC4602-2 were virulence plasmids for eels but not mice. A gene in pR99, which encoded a novel protein and had an equivalent in pC4602-2, was further shown to be essential, but not sufficient, for the resistance to eel serum and virulence for eels. There was evidence showing that pC4602-2 may form a cointegrate with pC4602-1. An investigation of six other biotype 2 strains for the presence of various plasmid markers revealed that they all harbored the virulence plasmid and four of them possessed the conjugal plasmid in addition.
Vibrio vulnificus
Strain (injury)
Vibrio Infections
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Multiple factors can be involved in the virulence processes of Aeromonas hydrophila. The objective of the present paper was to verify the presence of aerolysin, hidrolipase, elastase and lipase virulence genes through the polymerase chain reaction (PCR) in A. hydrophila isolates obtained from fish of the São Francisco River Valley, and to evaluate virulence according to the presence of these genes in Nile tilapia fingerlings. One hundred and fourteen isolates from the bacteria were used. DNA was heat extracted and PCR undertaken using specific primers described in the literature. For in vivo tests Nile tilapia fingerlings were used. From the PCR tests, negative isolates for all genes tested were selected, positive isolates for two genes (aerolysin and elastase) and positive for the four genes tested. These were inoculated at a concentration of 10(8) UFC/ml into the tilapias, considered as treatments; another group of animals was used as control (with inoculation of saline solution). In all, 12 distinct standards regarding the presence of virulence factors in isolates from A. hydrophila, were observed. Of the 114 isolates analyzed, 100 (87.72%) presented at least one of the virulence factors under study. The virulence factors were widely distributed among the A. hydrophila isolates. Aerolysin was the most frequent virulence factor present in the isolates analyzed. A. hydrophila led to the mortality of the Nile tilapia fingerlings, regardless of the absence or quantity of virulence genes tested.
Aerolysin
Nile tilapia
Virulence factor
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The two main diseases in the pangasius catfish industry are bacillary necrosis of Pangasianodon (BNP) and motile aeromonas septicaemia (MAS), where the aetiological agents have been identified as Edwardsiella ictaluri and Aeromonas hydrophila, respectively. In this study, apparently healthy Pangasianodon hypophthalmus were exposed to E. ictaluri, A. hydrophila or both bacterial species by intraperitoneal injection or immersion. There were 20 fish per treatment group, and the bacterial isolates used for the study were recovered from natural infections of BNP or MAS in farmed Vietnamese P. hypophthalmus. The results of the experimental infections mimicked the natural disease outbreaks reported from these pathogens in P. hypophthalmus. Furthermore, it was clearly demonstrated that E. ictaluri was only recovered from the fish exposed to the bacterium and not recovered from the animals receiving A. hydrophila.
Edwardsiella ictaluri
Bacterial disease
Pangasius
Vietnamese
Aerolysin
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