Abstract
This study aimed to evaluate the in vitro effect of carvacrol on different microorganisms of importance in shrimp farming, as well as its in vivo effect on zootechnical, immunological and microbiological performance, as well as resistance, of Litopenaeus vannamei challenged with Vibrio parahaemolyticus. In particular, the antimicrobial activity of carvacrol was evaluated in vitro by analysis of the minimum inhibitory concentration (MIC) and by agar diffusion disc with Gram-negative and Gram-positive bacteria. The in vivo experiment was conducted using different concentrations of carvacrol (1, 3, 4 and 6 mg mL-1) added to shrimp feed, together with a control diet without carvacrol. After four weeks, zootechnical, immunological and microbiological parameters, as well as resistance, of animals challenged with V. parahaemolyticus were evaluated. The MIC of Vibrio alginolyticus and Vibrio harveyi was 0.078 mg mL-1, while for the other bacteria, it was 0.156 mg mL-1 of carvacrol. The greatest halos of inhibition were observed in V. parahaemolyticus and Vibrio harveyi with significant differences demonstrated for the other microorganisms, except Escherichia coli. The in vivo results showed no significant differences among treatments. In conclusion, the antimicrobial activity of carvacrol was confirmed with Gram-negative and Gram-positive bacteria, and it is suggested that its antimicrobial potential is more effective against Vibrio spp. However, the concentrations of carvacrol used in vivo did not affect the parameters evaluated.
Highlights
The Pacific white shrimp Litopenaeus vannamei is the most profitable and commercially important species in shrimp farming, with a global production of approximately 5 million tonnes in 2018 (ABCC, 2017; FAO, 2020)
This study aimed to evaluate the in vitro effect of the phenolic compound carvacrol on different microorganisms of importance in shrimp farming, and it’s in vivo effect on zootechnical, immunological and microbiological performance, and resistance of Litopenaeus vannamei challenged with Vibrio parahaemolyticus
The greatest halos of inhibition were observed in V. parahaemolyticus and V. harveyi with significant differences demonstrated for the other microorganisms, except Escherichia coli
Summary
The Pacific white shrimp Litopenaeus vannamei is the most profitable and commercially important species in shrimp farming, with a global production of approximately 5 million tonnes in 2018 (ABCC, 2017; FAO, 2020). With the intensification of production, these animals are affected by viral and bacterial infectious diseases that cause serious economic losses owing to decreased production (Chakraborty and Hancz, 2011). Among these diseases are those caused by Gram-negative bacteria of the genus Vibrio. These microorganisms are part of the natural microbiota of the peneid shrimps and under stressful conditions can cause infections. Prolonged use of chemical substances can accumulate in aquatic animals and select antibiotic-resistant microbiota (Alderman and Hastings, 1998). The chemical residues could affect the environment and human health developing resistant bacteria against drugs for human medicine (Chakraborty and Hancz, 2011)
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