**1. Introduction**

Prawn such as *Macrobrachium vollenhobenii* is an important source animal protein that provides good quality protein and essential minerals and vitamins. It is also regarded as safest animal source of protein which comes from either wild or culture system. The current decline in the status fish from wild has been attributed to overfishing, illegal and irresponsible fishing, habitat destruction and pollution, among other factors. More so, the increase in population and change in the consumption pattern of fish has create huge gap between the demand and supply of fish [1]. One of the ways to bridge this gap is through aquaculture. The act of aquaculture means rearing of aquatic organisms, which entails any form of intervention to improve the production quantity and quality, management, disease prevention and control. Over the years, aquaculture has become the fastest growing sector in the world [2].

aquaculture but probiotics from lactic acid bacteria (LAB) and *Bacillus* species are often used

Gut Microbiota and Innate Immune Response of *Macrobrachium vollenhovenii* Infected…

*Lactobacillus acidophilus* is bacteria belonging to the genus Bacillus. It probiotics benefit as member of LAB group to improve non-specific immune response and disease resistance in in *Macrobrachium vollenhovenii* has not been fully elucidated hence the need for this study. Therefore, this study investigated the effect of diets fortified with *Lactobacillus acidophilus* on gut microbiota and innate immune response of *Macrobrachium vollenhovenii* Infected with

Feed ingredients were purchased from a reliable store Melbourne, Australia. *Lactobacillus aci-*

105 cfu/mL (**Table 1**). Soya bean was further prepared by toasting in a hot plate for 15 min at 100°C. Ingredients were ground in hammer mill and mixed together to formulate 43% crude protein (**Table 1**) calculated according to Pearson Square Method [9]. The mixed ingredients were pelleted through pelleting machine. The feeds were packed in polythene bags and stored in a cool dry place at room temperature until use with labels on them. The crude proteins of the ingredients were: fish meal (72%); toasted soybean (46.2%) and white maize (9.3%) [10].

*Macrobrachium vollenhenvonii* juveniles (mean weight = 18.02 ± 0.11 g; n = 360; 180 prawns for each pathogen) were obtained from a reputable farm in Melbourne, Australia and acclimatised for 2 weeks in glass aquaria tanks before the experiment. Prawns were weighed

design with three replicates. Each tank contained 20 prawns. The tanks were constantly connected to aerator (Model: AP-60) with air blowers. The prawns that were fed experimental diets were further subjected to *Pseudomonas aeruginosa* and *Aeromonas hydrophila* infection for 2 weeks to examine their innate immune performances and survival. The diets were fed to the *Macrobrachium vollenhovenii* to satiation throughout the experimentation. Measurements of

Three prawns were collected from each experimental unit before and after the trial for gut microbiota evaluation. Each prawn was deactivated in freezer at −20°C for 10 min and sterilised using formalin (50 ppm). The guts were aseptically collected and weighed into sterile universal bottles containing peptone water (0.1%) to release the available bacteria for a period of 2 h. 1 mL was taken from each sample bottle and diluted 10-folds and subsequently serially

, 102 , 103 , 104 and

http://dx.doi.org/10.5772/intechopen.78010

95

) in a completely randomised

*dophilus* ATCC 4356 was obtained from a laboratory and prepared into 0, 101

The feeds were reproduced after 21 days to avoid nutrients depletion.

and distributed into 18 glass aquaria tanks (35 × 30 × 20 cm**<sup>3</sup>**

the weight changes were measured using sensitive scale (**Model: M1207)**.

*Pseudomonas aeruginosa* and *Aeromonas hydrophila.*

**2. Materials and methods**

**2.1. Preparation of experimental diets**

**2.2. Experimental design and procedure**

**2.3. Evaluation of gut microbiota**

[7, 8].

Worldwide total crusteceans was 6,915,100 tonnes representing about 7% of total aquaculture production [2]. This achievement was attributed to transformation of farming techniques from simple methods to an improved and intensive aquaculture which promotes high seed quantities, adequate knowledge of stocking density, supply of required fish feeds. However, in spite of the success recorded in the prawn farms in recent times, the performance are far from it demand. The poor performance has been associated with many constraints, such as, modern knowledge in the science of fish farming, government policy, fish feed industry, marketing, distribution, and diseases. One of the major barriers to prawn farming are diseases and their management.

Disease is an establishment of pathogens in prawn tissues which cause disorderliness in physiological function of the fish that result in physical, biological and economical losses. Diseases arise as a result of complex interaction among the fish, pathogen and culture environment [3, 4]. Fish has inbuilt immune systems and defence mechanisms which protect them from being infected with pathogens. But practice of intensive farming system has the possibility of exposing prawn to infections. However, bacteria have been reported to be responsible for about 70–80% of disease infection in fish [5]. Some important bacteria in prawn farming are *Pseudomonas aeruginosa* and *Aeromonas hydrophila. Pseudomonas aeruginosa* and *Aeromonas hydrophila* are gram-negative bacteria in the families of Pseudomonadaceae and Aeromonadaceae respectively. They are ubiquitous, facultative anaerobe, rod-shaped and sugar fermented organism. Studies have reported that *Pseudomonas aeruginosa* and *Aeromonas hydrophila* infection in fish has resulted into haemorrhagic, speticemia, furunculosis and high mortality among others [1].

The problems of increase antibiotic resistance bacteria, residual effect and environmental unfriendly experienced in the use of antibiotics could ameliorate by probiotics application. Therefore, current studies have moved toward search for alternative such as probiotics. Probiotics are life microbial feed supplements that improve health host by modify the gastrointestinal tract of the fish. Fish, being a hydrophilic animal rely solely on the environment (water) which filtering through the body and gill as fish performs it physiological function would benefit from use of probiotics. Probiotics enhance the nutrient utilisation, modulate gut flora, inhibit the growth of pathogenic bacteria and improve growth and immune system of the fish as reported in the previous studies [6, 7]. Several probiotics have been used in aquaculture but probiotics from lactic acid bacteria (LAB) and *Bacillus* species are often used [7, 8].

*Lactobacillus acidophilus* is bacteria belonging to the genus Bacillus. It probiotics benefit as member of LAB group to improve non-specific immune response and disease resistance in in *Macrobrachium vollenhovenii* has not been fully elucidated hence the need for this study. Therefore, this study investigated the effect of diets fortified with *Lactobacillus acidophilus* on gut microbiota and innate immune response of *Macrobrachium vollenhovenii* Infected with *Pseudomonas aeruginosa* and *Aeromonas hydrophila.*
