Abstract
Prospect of antibacterial agents may provide an alternative therapy for diseases caused by multidrug-resistant bacteria. This study aimed to evaluate the in vitro bioactivity of Moringa oleifera seed extracts against 100 vibrios isolated from the marine shrimp Litopenaeus vannamei. Ethanol extracts at low (MOS-E) and hot (MOS-ES) temperature are shown to be bioactive against 92% and 90% of the strains, respectively. The most efficient Minimum Inhibitory Concentration (MIC) levels of MOS-E and MOS-ES against a high percentage of strains were 32 µg mL−1. Bioguided screening of bioactive compounds showed that the ethyl acetate fraction from both extracts was the only one that showed antibacterial activity. Vibriocidal substances, niazirine and niazimicine, were isolated from the aforementioned fraction through chromatographic fractionation.
Highlights
Bacteria of Vibrio genus are ubiquitous in the marine environment and are part of the indigenous microbiota of marine invertebrates
Detection of antibacterial activity in higher plants against vibrios with virulent, antimicrobial-resistant profiles is of utmost importance
The 100 strains were phenotypically identified as V. navarrensis (n = 53), V. brasiliensis (n = 15), V. parahaemolyticus (n = 10), V. xuii (n = 8), V. coralliilyticus (n = 5), V. cholerae (n = 4), V. neptunis (n = 2), V. alginolyticus (n = 1), V. diazotrophicus (n = 1), and V. vulnificus B3 (n = 1) [11]
Summary
Bacteria of Vibrio genus are ubiquitous in the marine environment and are part of the indigenous microbiota of marine invertebrates. Some species are recognized as human pathogens, often associated with diseases such as cholera and acute gastroenteritis [1, 2]. Vibrios are seen as opportunistic pathogens of cultured aquatic organisms, which is one of the reasons for observing the use of antibiotics in shrimp cultivation. Inappropriate use of antimicrobial drugs in aquaculture has been associated with negative environmental impacts: selection of bacterial populations resistant to drugs [3, 4] and contamination of adjacent ecosystems to culture ponds. Detection of antibacterial activity in higher plants against vibrios with virulent, antimicrobial-resistant profiles is of utmost importance. Due to its high medicinal activity [5], the vibriocidal capacity of the angiosperm Moringa oleifera was investigated. The antimicrobial effect of Moringa has been researched since the 1980s and seems to be related to some specific components including pterygospermin and Moringa glycosides, as well as 4-(α-L-rhamnosyloxy)-benzyl isothiocyanate and 4-(α-L-rhamnosyloxy)-phenyl-acetonitrile, which act especially against Bacillus subtilis, Mycobacterium phlei, Serratia marcescens, Escherichia coli, Pseudomonas aeruginosa, Shigella sp., and Streptococcus sp. [6]
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