Enhancing growth and resistance to Vibrio alginolyticus disease in catarina scallop (Argopecten ventricosus) with Bacillus and Lactobacillus probiotic strains during early development

In bivalve aquaculture, selecting suitable probiotic treatments can be crucial for improving hatchery‐rearing of larvae and juveniles. We assessed the potential of five bacterial strains, previously selected in vitro, to improve survival, growth and resistance of catarina scallop Argopecten ventricosus during early and late larval and juvenile developmental stages, as well as during exposure to the pathogen Vibrio alginolyticus. Hatchery‐reared larvae and juveniles were treated with eight treatments of single or combined strains of Bacillus and Lactobacillus at 1 × 10⁶ CFU mL^?1 every 48 h for 9 days (larvae) and 21 days (juveniles). Compared with the control, significantly higher survival and growth in size and weight of early veliger larvae occurred with the antibiotic and the RL5 (Lactobacillus graminis) treatments. Significantly enhanced settlement of pediveliger larvae occurred with a different probiotic strain, the mix of Lactobacillus and Bacillus (MIX‐LB), while higher survival and growth of early juveniles occurred with C3 (Lactobacillus plantarum). The mix of Bacillus (MIX‐B) significantly increased survival of juveniles from V. alginolyticus after 120‐h infection, consistent with maximum activity of superoxide dismutase enzyme. In contrast, all untreated and infected scallops died by 96 h. The three Bacillus strains performed poorly when used as single treatments and when given to early developing larvae. Our results indicate that the action mechanism of probiotic strains is stage specific and strain specific, generating different responses by the host, including improved survival and growth (likely from better nutrient assimilation) and higher resistance against pathogens (possibly from strengthening the immune system).     

Comparative studies of the growth,survival, and reproduction of diploid and triploid Kumamoto oyster,Crassostrea sikamea

Triploid oysters have been used for farming to improve growth but have not been created in the Kumamoto oyster, Crassostrea sikamea, which is one of the crucial aquaculture species on the southern coast of China. In the present study, triploids were created using cytochalasin B to inhibit polar body II release in C. sikamea, with the untreated oysters as controls. Triploidy rates of 87 and 57.67%, on average, were obtained in larvae and adults, respectively. Larval growth and survival of the triploid were significantly lower than that of the controls (p < 0.05). In contrast, the triploid postlarvae and adults had a significant growth advantage over the controls (p < 0.05) during the period of 180 (December) to 450 days (September of the next year). Moreover, the triploids clearly exhibited significant sterility in the reproductive season. The glycogen and triglyceride contents in the gonad, adductor muscle, mantle, and gill were higher in triploids than in controls from 180 to 450 days. As a result, high physiological energy supply was strongly correlated with superior growth and reduced reproduction in triploid C. sikamea. The triploid C. sikamea is an excellent oyster species and can be used to improve growth for C. sikamea farming.     

Probiotic effect of Bacillus NL110 and Vibrio NE17 on the survival,growth performance and immune response of Macrobrachium rosenbergii (de Man)

Eight hundred and eighty‐five strains of bacterial isolates from various samples associated with the natural habitat of Macrobrachium rosenbergii were screened for their probiotic potential. Two putative probionts namely Bacillus NL110 and Vibrio NE17 isolated from the larvae and egg samples, respectively, were selected for experimental studies and were introduced to the juveniles of M. rosenbergii (0.080±0.001 g) through different modes such as through feed, water and both. The probiotic potential of the above bacteria in terms of improvements in water quality, growth, survival, specific growth rate (SGR), feed conversion ratio and immune parameters was evaluated. The treatment groups showed a significant improvement in SGR and weight gain (P<0.001). Survival among different treatment groups was better than that in the control group. There were also significant improvements in the water quality parameters such as the concentration of nitrate and ammonia in the treatment groups (P<0.05). Improvements in immune parameters such as the total haemocyte count (P<0.05), phenoloxidase activity and respiratory burst were also significant (P<0.001). It is concluded that screening of the natural microflora of cultured fish and shellfish for putative probionts might yield probiotic strains of bacteria that could be utilized for an environment‐friendly and organic mode of aquaculture.     

Antagonism against fish pathogens by cellular components and verification of probiotic properties in autochthonous bacteria isolated from the gut of an Indian major carp,Catla catla (Hamilton)

Probiotic potential of the autochthonous bacteria in catla, Catla catla has been evaluated through determination of antagonistic activity (in vitro) of the cellular components of gut bacteria against seven fish pathogens. Altogether 208 strains were isolated, inhibitory activity of the isolates was evaluated through cross‐streaking and 16 primarily selected antagonistic strains were confirmed using the double‐layer method. Four bacteria that showed antagonism against ≥4 pathogens were selected as putative probiotics. The intracellular, extracellular, whole‐cell and heat‐killed cell components exhibited bactericidal activity against the pathogens. In addition, the selected strains were capable of producing different extracellular enzymes, competent to grow in intestinal mucus and could tolerate diluted bile juice. Analysis of 16SrRNA partial gene sequence revealed that both the strains CC1FG2 and CC1FG4 were Bacillus methylotrophicus (KF559344 and KF559345), while the isolates CC1HG5 and CC2HG7 were Bacillus subtilis subsp. spizizenii (KF559346) and Enterobacter hormaechei (KF559347) respectively. Bio‐safety evaluation through intra‐peritoneal injection of the isolates did not induce any pathological signs or mortalities in C. catla. The study confirmed probiotic properties of autochthonous gut bacteria in C. catla and demonstrated potential for using them as bio‐control agents. However, in vivo studies are essential to explore their efficacy in the commercial aquaculture.     

Effect of probiotics on immune competence of giant freshwater prawn Macrobrachium rosenbergii

This study evaluates the effect of probiotics, Zymetin, on the immune efficiency of Macrobrachium rosenbergii juvenile against pathogenic Vibriospp. and Aeromonasspp. The experiment was conducted in glass aquaria with same level of feeding under different treatments, that is, negative control (Cn), positive control with Vibrio spp. (Cv) and Aeromonasspp. (Ca), prawn juveniles fed with probiotics (Zymetin) at 5 g/kg of feed but without pathogen (T1), probiotic fed prawn challenged with Vibrio spp. (T2) and Aeromonasspp. (T3). The results demonstrated that T1 showed higher survival rate, total haemocyte count, non‐granular haemocyte count, phagocytic activity, and clearance efficiency compared to other treatment groups. In contrast, decreased number of small and large granular haemocyte was observed in T1. Despite that, THC was found to be significantly different (p < 0.05) among all the controls and lowest was in Cv, followed by Ca. Besides, phagocytic activity and clearance efficiency against Vibrio spp. and Aeromonasspp. decreased significantly in Cn, Ca, and Cv fed M. rosenbergiijuvenile, while the values were found to be higher in T1 followed by T2 and T3, in that order. In addition, the challenge test showed an increasing trend of total and beneficial bacterial density as well as declining trend of some harmful bacteria in the water and gut of prawn in all the groups tested (p < 0.05).     

In vitro selection and characterization of putative probiotics isolated from the gut of Acipenser baerii (Brandt, 1869)

To select and characterize potential probiotic bacteria from the gut microbiota of Siberian sturgeon (Acipenser baerii), 129 strains isolated from the hindgut were screened for antagonistic activity against five fish pathogens. Ten isolates showed antagonism towards three or more pathogens. Nine of these isolates were Gram‐positive, belonging to Lactococcus (seven) and Bacillus (two), and a single strain belonging to the Gram‐negative Citrobacter. These inhibitory isolates were identified using genetic, phentotypic and biochemical traits, and further characterized by in vitro tests assessing the adhesion and growth in mucus and resistance to gastric and intestinal fluids. The candidate probiotics were determined to be non‐pathogenic through an in vivo study. Based on these assays, Lactococcus lactis ssp. lactis STG45 and STG81 showed the broadest inhibitory potential, a high viability in simulated gastrointestinal juice and the highest adhesion capacity to mucus. They were therefore selected as the most promising candidate probiotics. This is the first study screening probiotics among the gut microflora of Siberian sturgeon.     

Molecular species diagnosis confirmed the occurrence of Kumamoto oyster <Emphasis Type="Italic">Crassostrea sikamea</Emphasis> in Korean waters

In order to develop an appropriate natural resource management policy, it is important to elucidate the cryptic habitats of species. Oyster species are likely to have such unrecognized habitats owing to the difficulty involved in morphological species identification. In this study, we discovered a novel cryptic habitat of the Kumamoto oyster Crassostrea sikamea, a sibling species of the Pacific oyster C. gigas, in Korean waters. We collected 50 oyster samples from Suncheon Bay, located in the southern Korean Peninsula, among which 20 individuals of C. sikamea, 29 of C. gigas, and one C. sikamea/C. gigas hybrid were identified based on mitochondrial and nuclear DNA markers. There were no significant differences in shell morphology between the two species, which is consistent with how difficult it is to delineate them based on their shell features. Our identification of this novel C. sikamea habitat should help to improve the resource management of East Asian oysters.     

Molecular cloning and expression of the heat shock protein 70 gene in the Kumamoto oyster <Emphasis Type="Italic">Crassostrea sikamea</Emphasis>

Episodes of summer mortality of the Kumamoto oyster Crassostrea sikamea are a major problem for its cultivation. Expression of the heat shock protein 70 (HSP70) is induced by various environmental stresses, including heat. We cloned and sequenced hsp70 complementary DNA from C. sikamea to investigate the relationship between hsp70 expression and heat tolerance in this oyster. Quantitative real-time polymerase chain reaction was performed using gill tissue dissected from oysters before and after heat shock for 1 h. The results showed hsp70 expression was faster and greater in oysters cultured at 20–22 °C than at 10–12 °C, and survival was lower among oysters cultured at 20–22 °C than at 10–12 °C. Moreover, heat tolerance was investigated by a 1-h pre-heat treatment, followed by exposure to heat shock conditions 5 days later. Survival was higher and hsp70 expression was notably lower in oysters that received the pre-heat treatment compared with those that did not. We conclude that a pre-heat treatment of only 1 h may be useful for inducing heat tolerance in C. sikamea, and that a low level of hsp70 expression after heat shock is an important index in selecting for high heat tolerance in these oysters.     

Vibrio spp. Control at Brine Shrimp,Artemia, Hatching and Enrichment

Experiments were conducted to evaluate different prophylactic methods to control the bacterial load in brine shrimp, Artemia, hatching. The first experiment evaluated three treatments to control Vibrio spp. during the Artemia hatching: microalgae (Chaetoceros calcitrans), probiotic (Bacillus spp.), and antibiotic (Florfenicol). In the second experiment, Artemia metanauplius were enriched in distinct treatments with C. calcitrans, probiotic, and emulsion rich in docosahexaenoic and eicosapentaenoic fatty acids. Enriched Artemia metanauplius and nauplii (control) were offered to white shrimp, Litopenaeus vannamei, postlarvae (PL₇–PL₁₉). Presumptive Vibrio were quantified in Artemia, PL, and rearing water. Microalgae and probiotic were effective to control Vibrio spp. in Artemia nauplii. The enrichment process increased the Artemia bacterial load but did not affect Vibrio load in L. vannamei.     

The use of probiotics during the nursery rearing of the pink shrimp Farfantepenaeus brasiliensis (Latreille, 1817) in a zero exchange system

The present work evaluated the use of probiotics during the nursery rearing of the pink shrimp Farfantepenaeus brasiliensis, in a zero exchange aerobic heterotrophic culture system during 30 days. Three replicate tanks were randomly assigned to the following treatments: (1) Bacillus spp. mixture (Sanolife Pro‐‐W^®), (2) Bacillus sp., Enterococcus sp., Lactobacillus spp. mixture (Biomin Start‐grow^®), (3) Bacillus cereus var. toyoi and (4) control treatment (without probiotic addition). Bacteriological analysis monitored the abundance of presumptive Vibrio spp. in the water of experimental tanks. For the immunological analysis, shrimp haemolymph was collected to determine the granular haemocyte count and total protein concentration. Results showed that mean final weight and specific growth rate of shrimp in the probiotic treatments were significantly higher. Furthermore, shrimp reared in the probiotic treatments showed higher levels of total protein and granular haemocyte. The bacteriological analysis showed that the concentration of Vibrio spp. measured in probiotic treatment tanks was lower than that recorded in the control tanks.     

Identification and characterization of lactic acid bacteria isolated from rainbow trout, Oncorhynchus mykiss (Walbaum), with inhibitory activity against Lactococcus garvieae

A study was conducted to evaluate the probiotic properties of endogenous rainbow trout microbiota against pathogenic Lactococcus garvieae. A total of 335 bacterial strains were isolated from rainbow trout and screened for antagonistic activity against L. garvieae using an agar spot assay. Antagonistic strains were grouped by PCR amplification of repetitive bacterial DNA elements (rep‐PCR) and identified by 16S rRNA gene sequence analysis. The results revealed that the antagonistic strains belonged to the genera Lactobacillus, Lactococcus and Leuconostoc. Further probiotic characteristics, such as specific growth rate, doubling time, resistance to biological barriers, antibiotic resistance, hydrophobicity and production of antimicrobial substances, were also studied. These strains were able to survive low pH and high bile concentrations, showed good adherence characteristics and a broad spectrum of antibiotic resistance. The antagonistic efficacy was maintained after sterile filtration and was sensitive to proteinase K, indicating that proteinaceous extracellular inhibitory compounds were at least partially responsible for pathogen antagonism. Based on these results, these strains should be further studied to explore their probiotic effects in challenge experiments in vivo. This study shows clear evidence that the indigenous trout‐associated microbiota may provide a defensive barrier against L. garvieae.     

熊本牡蛎中国群体与美国群体杂交效应及杂交三倍体优势分析

为了评估熊本牡蛎(Crassostreasikamea)中国群体与美国群体的杂交效应与杂交三倍体优势,构建了杂交群体和自交群体,并使用细胞松弛素B诱导了杂交三倍体,比较分析了幼虫、稚贝与成贝的生长与存活优势。自交群体和杂交群体的幼虫、稚贝与成贝的培养条件均相同,室内培育幼虫,培育密度为4～5个/mL,自然海区养殖稚贝与成贝,养殖密度为40～45个/吊。结果表明,与自交组相比,杂交二倍体具有较高的卵裂率(13.61%)与D幼率(5.67%)(P0.05),但杂交二倍体幼虫的壳高生长表现杂种劣势(–0.43%),而稚贝、成贝的壳长与壳高的生长表现杂种优势,平均优势率分别为3.96%与6.65%。杂交三倍体诱导组幼虫的壳高生长优势率为3.69%,稚贝及成贝的壳长与壳高平均生长优势率分别为12.69%与13.64%,并且日龄越大生长优势越显著。总体上,杂交三倍体诱导组在3～180日龄具有存活劣势,并且15日龄存活劣势率最大(–48.72%),而在360日龄存活优势率为6.70%。杂交二倍体幼虫与成贝均具有存活优势,平均优势率分别为10.44%与4.59%。本研究表明熊本牡蛎中美地理群体杂交二倍体的生长和存活优于自交二倍体,而杂交三倍体诱导组的生长优势较显著,并且在成贝期具有显著的成活率优势,表明杂交三倍体诱导组的优势来源于三倍体优势和部分杂种优势。     

Effect of dietary supplementation of inulin and W. cibaria on haemato‐immunological parameters of hybrid surubim (Pseudoplatystoma sp)

The dietary supplementation of prebiotics, probiotics and symbiotic in hybrid surubins (a Pseudoplatystoma corruscans and P. fasciatum cross) was evaluated for the effects on their autochthonous intestinal microbiota and on haematological and immunological parameters. A total of 160 fish were divided into four treatment groups with four replicates each. The treatment groups were fed with the following diets for 15 days: control diet without supplementation; 0.5% inulin (prebiotic) supplementation; Weissella cibaria (CPQBA 001‐10 DRM 02) (7.87 ± 0.2 log CFU g^?1) supplementation; or 0.5% inulin and W. cibaria supplementation (symbiotic group). The midgut intestines of the fish with the symbiotic diet supplementation had higher concentrations of lactic acid bacteria (7.07 ± 1.11 log CFU g^?1) and low levels of Vibrio spp (1.90 ± 0.60 log CFU g^?1) and Pseudomonas spp (2.23 ± 1.48 log CFU g^?1). In addition, increased erythrocytes and reduced circulating neutrophils were observed in this group. No differences in blood glucose, serum protein or lysozyme levels were detected between treatment groups. However, a higher concentration of total immunoglobulin was observed in fish fed with the probiotic and symbiotic diets. The addition of 0.5% inulin (prebiotic) thus W. cibaria (probiotic) to the diet of Pseudoplatystoma hybrid surubins reduce the number of pathogenic bacteria and stimulate the beneficial intestinal microbiota and may possibly alter their immune defence system.     

Application of prospective probionts at early stages of Atlantic cod (Gadus morhua L.) rearing

This work aimed at validating the use of two prospective probionts (Arthrobacter sp. and Enterococcus sp.) at early stages of cod (Gadus morhua L.) rearing. Ova at late post‐fertilized stage and larvae during their first 4 weeks of life were bathed with both probionts, isolated previously from the cod‐rearing environment. This treatment was compared with groups fed rotifers supplemented with a commercial probiotic (Remus^®) and those untreated. Microbiological analyses (total viable counts, presumptive Vibrio and lactic acid bacteria) were performed in rearing systems and larval survival, growth and development were assessed. Larval development was evaluated by proteolytic activity of larval lysates and immunological analysis of important proteins: apolipoprotein A‐I, haemoglobin, C‐reactive protein, C3 and cod serum proteins. Bacterial bathing led to a significantly higher larval weight, length and culturable microbial load in larval gastrointestinal (GI) tract when compared with the control and Remus groups. Development occurred earlier in bathed larvae. However, their survival was negatively affected compared with the control group, but was significantly higher than for the Remus group. The non‐pathogenicity of both probionts was demonstrated by intraperitoneal injection of 13 g cod juveniles. The results suggest that Arthrobacter and Enterococcus probionts affected the larval GI microbiota and contributed to growth, development and digestion, either directly or indirectly.     

Autochthonous probiotic as growth promoter and immunomodulator for Astyanax bimaculatus cultured in water recirculation system

This work aimed to evaluate the probiotic Lactobacillus spp. in the microbiota of Astyanax bimaculatus reared in a water recirculation system. The experiment was randomized, using 800 postlarvae distributed into eight polyethylene containers, separated into two treatments, in quadruplicate: supplementation with Lactobacillus spp. (Probiotic) and no supplementation (Control). After 90 days of culture, 13 fish per container were anaesthetized. Three of these underwent microbiological evaluation, and haematological analyses were carried out on five. Immunological assessment was performed on another five fish. Zootechnical parameters were evaluated for all animals. In the microbiological evaluation, the probiotic group presented higher counts of lactic acid bacteria, but lower counts of Vibrio spp., Pseudomonas spp., and Staphylococcus spp., when compared with control. After haematological analysis, the supplemented group presented low haematimetric indices of Mean Corpuscular Haemoglobin Concentration and Mean Corpuscular Haemoglobin (MCHC and MCH, respectively) and higher amounts of total leucocytes, thrombocytes and circulating monocytes when compared with control. The immunological profile did not differ between treatments. In the zootechnical performance, probiotic group presented higher productivity, survival and apparent food efficiency when compared with control. Therefore, when Lactobacillus spp. was supplemented in the diet of A. bimaculatus, immunocompetence and the zootechnical performance of animals increased.     

Use of macroalgae supplemented with probiotics in the Haliotis rufescens (Swainson, 1822) culture in Northern Chile

In this study, we evaluate the use of macroalgae as vectors of probiotics bacteria into the digestive tract of abalone to improve their survival and growth. It is shown that when abalone Haliotis rufescens of different sizes were fed with a natural diet composed of fronds of the macroalga Macrocystis integrifolia supplemented with a mixture of Vibrio sp. C21‐UMA, Agarivorans albus F1‐UMA and Vibrio sp. F15‐UMA bacteria, there was a significant increase (P<0.05) in the average monthly growth rate and survival (%)in a period of 210 days, compared with the control without a probiotic supplement. The permanence of the probiotics in the digestive tract of the animals was monitored, and it was found that the number of culturable C21‐UMA and F1‐UMA bacteria decreased significantly (P<0.05) in recently weaned and adult abalone, and they almost disappeared completely on day 19 of the bioassay. However, the culturable Vibrio sp. F15‐UMA disappeared completely from the digestive tract on day 22 of the bioassay, and these were the bacteria that remained at the highest concentration compared with the other two bacterial strains over the experimental period. It is therefore shown that it is feasible to use a probiotic mixture to improve the profitability of the H. rufescens culture.     

Intestinal microbiota variation in Senegalese sole (Solea senegalensis) under different feeding regimes

The aim of this study was to determine the influence of the feeding regimes in Senegalese sole (Solea senegalensis) cultured under extensive, semi‐extensive and intensive production systems. A total of 254 bacterial isolates from guts of fish cultured under different production systems and feeding regimes were tested. Biochemical tests and genetic analyses based on the 16S rDNA sequence analysis were conduced to identify bacterial strains. Vibrio species were the most represented taxonomic group in the culturable microbiota of S. senegalensis guts tested. Particularly, Vibrio ichthyoenteri was the most frequently isolated Vibrio species. Comparison among diets showed a significant reduction (P<0.05) in vibrio percentages and a higher occurrence of Shewanella species in Senegalese soles fed polychaeta. In addition, a major influence of environmental temperature on microbiota composition was detected. Cold temperatures brought about a change in the percentages of Vibrio species and a higher representation of α‐Proteobacteria in both outdoor systems (extensive and semi‐extensive). The significant differences between intestinal bacterial composition in Senegalese soles fed commercial diets and natural preys (polychaeta) reveal the necessity to develop specific optimized diets for the intensive rearing of this fish species.     

Recent update on the prevalence of Vibrio species among cultured grouper in Peninsular Malaysia

Vibrio infections are common among marine fish and lead to serious problems in the aquaculture sector. This study reports a recent occurrence of Vibrio species (spp.) isolated from cultured groupers in Peninsular Malaysia using the gyrB and pyrH genes. A total of 147 Vibrio strains were successfully isolated from 77 (64%) groupers using culture method and subjected to gyrB and pyrH sequencing for species identification and confirmation. Results showed that 89% of Vibrio strains were identified and clustered to six groups of Vibrio spp., while 11% were not clustered to any Vibrio spp. using the gyrB sequences. Meanwhile, by analysis of the pyrH sequences all the 147 Vibrio strains (100%) were successfully identified and clustered into 11 groups of Vibrio spp., including the gyrB non‐identified strains. The pyrH gene provides a better resolution for identification of Vibrio spp. compared with the gyrB gene. Thus, the pyrH gene was more suitable for a rapid determination of Vibrio spp. distribution in Peninsular Malaysia. Using the pyrH gene, our study found higher prevalence of Vibrio vulnificus (33%), V. alginolyticus (24%) and V. parahaemolyticus (22%), followed by V. rotiferianus (5%), V. harveyi (3%), V. tubiashii (2%), V. campbellii (2%), V. ponticus (1%), V. diabolicus (1%), V. owensii (1%) and others Vibrio sp. (7%). Thus, the results of this study revealed that the occurrence of pathogenic vibrios among grouper fish is still high in Malaysian aquaculture. In addition, the pyrH gene was proved as a suitable marker for rapid identification of Vibrio species compared with the gyrB gene.     

Effects of synbiotic containing Lactobacillus plantarum 7–40 and galactooligosaccharide on the growth performance of white shrimp,Litopenaeus vannamei

This study aimed to develop a synbiotic combination with probiotic, Lactobacillus plantarum 7–40 and one of three prebiotics, fructooligosaccharide (FOS), galactooligosaccharide (GOS) and mannan oligosaccharide (MOS). The best in vitro growth was observed when probiotic was cultured in the medium containing either FOS or GOS as the sole of carbon source. The analysis of enzyme activity revealed that GOS induced the highest activities of protease and β‐galactosidase of probiotic. Based on the findings, probiotic + GOS were selected as synbiotic to evaluate if it could promote the growth of white shrimp, Litopenaeus vannamei. For this, four diets, including a basal diet with no GOS or probiotic (control), 0.4% GOS (PRE), 10⁸ CFU probiotic kg^?1 (PRO) and 0.4% GOS in combination with 10⁸ CFU probiotic kg^?1 (SYN), were fed to shrimp for 60 days, and then the growth performance, intestinal microbiota (including total Vibrio counts, VBCs; and lactic acid bacteria, LAB) and digestive enzyme (including protease, leu‐aminopeptidase and β‐galactosidase) were evaluated. The weight gain (WG) of shrimp fed the PRO did not significantly differ from those of control (p > .05). Shrimp fed the SYN had significantly higher WG compared with the other treatments (p < .05). In addition, the SYN‐fed shrimp had significantly higher LAB and protease, leu‐aminopeptidase and β‐galactosidase activity (p < .05). The lowest presumptive Vibrio count (VBC) was also observed in intestines of SYN‐fed shrimp. Therefore, we suggested that Lac. plantarum 7–40+ GOS can be used as a synergistic synbiotic for shrimp culture.     

Prevalence and antimicrobial resistance of vibrios of human health significance in inland saline aquaculture areas

This study was conducted to evaluate the prevalence, potential pathogenicity and antimicrobial resistance of Vibrio isolates from 65 soil/water/fish samples collected from inland saline aquaculture areas. Depending on the sample type, presumptive Vibrio counts ranged from 2.50 to 6.16 log₁₀ CFU/ml (or/g). Among the 119 confirmed Vibrio isolates, Vibrio cholerae was found to most dominant (91.6%) and it was detected in all the samples from inland saline areas. Seven other Vibrio spp. including Vibrio parahaemolyticus and Vibrio vulnificus were also detected. Except one O139 serotype, rest of the V. cholerae isolates were found belonging to non‐O1/non‐O139 serogroups. None of the V. cholerae isolate was found positive for ctx gene. Antimicrobial susceptibility testing against 7 commonly used antibiotics revealed highest resistance (50.4%) against ampicillin. Very high intermediate resistance (87.4%) was also observed against erythromycin. Contrary to previous studies, high susceptibility (>70%) to chloramphenicol, nalidixic acid, tetracycline and trimethoprim was observed in Vibrio isolates obtained in present study. Almost 20% of Vibrio isolates were resistant to two or more antibiotic classes with multiple antibiotic resistance (MAR) index value of ≥0.28. Presence of V. cholerae isolates with very high MAR index value of 0.85 also suggested that these multidrug‐resistant environment isolates could serve as reservoir of antibiotic‐resistant genes in aquatic systems. The presence of multiple drug resistance vibrios in emerging inland saline aquaculture systems emphasizes the need for their routine monitoring for developing the risk assessment and mitigation strategies.