Pathogenicity and antibiotic susceptibility of two bacterial pathogens associated with the clam Tapes decussatus in some Egyptian fisheries

Abstract

Bivalve aquaculture is generally influenced by bacterial pathogens that cause high mortality-related losses in hatcheries. Six bacterial phenotypes had been previously isolated as the most predominant microorganisms in carpet shell clam (Tapes decussates) samples collected from natural beds in representative Egyptian clam fisheries. The main aims of this study were to investigate the nature of the pathogenic strains that significantly affect clam survival and test their susceptibility to commercially available antibiotics. Based on their 16S rRNA sequences and some biochemical features, two potent clam pathogens were emerged; one of which is gram-positive and the other is gram-negative. The former isolate was identified as Micrococcus luteus and the latter as Vibrio alginolyticus. Experimental challenges with the two bacterial pathogens introduced at different initial cell concentrations (2.5 X 10 4-7.5 X 10 4 cfu ml-1) showed markedly diverse clam mortality results. However, the pathogenic interaction of M. luteus with clam survival was generally higher than that of V. alginolyticus. When introduced at a relatively low initial cell density, the infectious records of V. alginolyticus were significantly increased suggesting that the expression of its key virulence factors is mainly triggered as a response to host contact. Antibiotic susceptibility tests suggested chloramphenicol and tetracycline as markedly effective agents that can be used to control the spread of these two bacterial pathogens in aquaculture applications.

Genome‐wide comparison of Carnobacterium maltaromaticum derived from diseased fish harbouring important virulence‐related genes

“…D‐mannosaminuronic acid and/or capsular K7 antigen) of V. parahaemolyticus , Bacillus , S. aureus and/or E. coli are crucial factors in their virulence (Ichihara, Ishimoto, & Ito, 1974; Miller et al., 2004; O'Riordan & Lee, 2004; Torii, Sakakibara, & Kuroda, 1973; Yoneyama et al., 1982). Also, their composition consisting of long‐chain polysaccharide polymers can be considered important factors for bacterial pathogenicity (Abdella, El‐Wazzan, El‐Sersy, Sabry, & El‐Helow, 2017; Miller et al., 2004; O'Riordan & Lee, 2004). Specifically, one of the major cell wall components in gram‐positive bacteria is teichuronic acid (TUA), composed of repeating units of D‐mannosaminuronic acid and glucose with phosphodiester bond (Arunkumar, Thanalakshmi, Kumar, & Premkumar, 2013).…”

“…Specifically, one of the major cell wall components in gram‐positive bacteria is teichuronic acid (TUA), composed of repeating units of D‐mannosaminuronic acid and glucose with phosphodiester bond (Arunkumar, Thanalakshmi, Kumar, & Premkumar, 2013). TUA is a well‐known virulence factor for gram‐positive bacteria, such as Streptococcus , Staphylococcus and Micrococcus (Abdella et al., 2017; Deng, Alexander, Lei, & Anderson, 2010). According to UDP‐N‐acetylglucosamine‐derived O‐antigen building block biosynthesis in the Meta Cyc database (Caspi et al., 2015), the final step in the synthesis of D‐mannosaminuronic acid (UDP‐N‐acetyl‐α‐D‐mannosaminuronate) is the conversion of UDP‐N‐acetyl‐α‐D‐mannosamine to UDP‐N‐acetyl‐α‐D‐mannosaminuronate via UDP‐N‐acetyl‐D‐mannosamine dehydrogenase ( wecC ).…”

Molecular characterization of Aeromonas hydrophila detected in Channa marulius and Sperata sarwari sampled from rivers of Punjab in Pakistan

“…These fish are prime candidates for aquaculture and have been widely cultivated [12,13]. However, it's important to note that freshwater bodies, their primary habitat, also host the zoonotic pathogen Aeromonas hydrophila, which can infect fish, bivalves, amphibians, reptiles, and humans [14][15][16]. Two successful candidates in freshwater aquaculture are Sperata sarwari and Channa marulius, cultivated commercially in various regions, including Pakistan, India, Bangladesh, China, and Indonesia, where they are top producers [17].…”

Whole spectrum of Aeromonas hydrophila virulence determinants and the identification of novel SNPs using comparative pathogenomics

“…The increasing output necessitates the efficient use of water resources, which has been achieved through intensive aquaculture systems; however, it is a very stressful environment for cultivated animals and has intensified the development and spread of bacterial infections 4 . Freshwater bodies have been found as reservoirs of Aeromonas hydrophila , which may infect fish, reptiles, amphibians, bivalves, and humans 5 – 8 . It has been proven to be the causative agent of numerous disease outbreaks in fish, including septicemia, ulcerative and hemorrhagic diseases 2 , 9 .…”