Shrimp pathogenicity, hemolysis, and the presence of hemolysin and TTSS genes in Vibrio harveyi isolated from Thailand

Abstract

The virulence factors of Vibrio harveyi, the causative agent of luminous vibriosis, are not completely understood. We investigated the correlations between shrimp mortality, hemolysis, the presence of a hemolysin gene (vhh), and a gene involved in the type III secretion system (the Vibrio calcium response gene vcrD). V. harveyi HY01 was isolated from a shrimp that died from vibriosis, and 36 other V. harveyi isolates were obtained from fish and shellfish in Hat Yai city, Thailand. An ocean isolate of V. harveyi BAA-1116 was also included. Thirteen isolates including V. harveyi HY01 caused shrimp death 12 h after injection. Most V. harveyi isolates in this group (designated as Group A) caused hemolysis on prawn blood agar. None of the shrimp died after injection with V. harveyi BAA-1116. Molecular analysis of all V. harveyi isolates revealed the presence of vcrD in both pathogenic and non-pathogenic strains. Although vhh was detected in all V. harveyi isolates, some isolates did not cause hemolysis, indicating that vhh gene expression might be regulated. Analysis of the V. harveyi HY01 genome revealed a V. cholerae like-hemolysin gene, hlyA (designated as hhl). Specific primers designed for hhl detected this gene in 3 additional V. harveyi isolates but the presence of this gene was not correlated with pathogenicity. Random amplified polymorphic DNA (RAPD) analysis revealed a high degree of genetic diversity in all V. harveyi isolates, and there were no correlations among the hhl-positive isolates or the pathogenic strains.KEY WORDS: Vibrio harveyi · Type III secretion system · TTSS · vcrD · vhh · hhl · Random amplified polymorphic DNA analysis · RAPD Resale or republication not permitted without written consent of the publisherDis Aquat Org 86: [113][114][115][116][117][118][119][120][121][122] 2009 against sheep and fish erythrocytes compared with non-virulent isolates from sea water or diseased Talorchestia sp. (Liu et al. 1996). Investigations of the pathogenicity of V. harveyi isolates in fish (Atlantic salmon and rainbow trout) have demonstrated that both pathogenic and non-pathogenic V. harveyi isolates induced hemolysis against erythrocytes from sheep, rabbit, donkey, and horse, and the presence of the hemolysin gene vhh has been demonstrated in V. harveyi (Zhang & Austin 2000, Zhang et al. 2001). An investigation of the mortality of Artemia franciscana nauplii after inoculation with V. harveyi isolates from healthy and diseased penaeid shrimp from Asia and the Americas indicated that particular exoenzymes were associated with virulent strains (Soto-Rodriguez et al. 2003). No correlation between the hemolytic activity against sheep erythrocytes and the death of infected shrimps was detected (Soto-Rodriguez et al. 2003). Further research is needed to resolve these controversies between the pathogenicity of V. harveyi and its ability to cause hemolysis.Recent studies have shown that many bacteria use a cell-cell communication process known as quorum sensing to control cell population density and...

Sigma E Regulators Control Hemolytic Activity and Virulence in a Shrimp Pathogenic Vibrio harveyi

“…The V. harveyi hemolysin (VHH) is a member of the broadly distributed thermolabile hemolysin (TLH) family [9]–[12] and appears to be sufficient for hemolytic activity in some, but not all, strains of V. harveyi [12], [13]. We have previously determined that the vhh gene is present in all V. harveyi isolates from both healthy and diseased marine animals collected in Southern Thailand [14]. However, hemolytic activity on blood agar was variable in the vhh bearing isolates, suggesting that hemolytic activity is influenced by additional factors.…”

Virulence of Vibrio harveyi responsible for the “Bright-red” Syndrome in the Pacific white shrimp Litopenaeus vannamei

“…at dose of 10 3 CFU g À1 . Challenges with V. harveyi strains reported mortalities of about 50% at doses exceeding 10 4 CFU g À1 (Liu et al, 1996;Alapide-Tendencia and Dureza, 1997;Jayasree et al, 2006;Rattanama et al, 2009). These findings clearly demonstrate differences in the virulence of V. harveyi strains.…”

“…Only gelatinase, amylase and lipase activities were detected in the three salinities, the hydrolytic activity of the other enzymes was weak without differences among treatments. Several studies consider the hemolytic activity as a major virulence factor for some V. harveyi strains (Zhong et al, 2006;Haldar et al, 2010;Rattanama et al, 2009) but Vh CAIM 1792 does not have it (data not shown). There was no correlation between Artemia mortality and hemolytic activity of V. harveyi strains (Soto-Rodriguez et al, 2003).…”

“…Vibriosis is another important disease affecting the shrimp industry in Mexico, causing recurrent outbreaks (Soto-Rodriguez et al, 2010a). Some Vibrio strains have proved to be pathogenic to penaeid shrimp (Alapide- Tendencia and Dureza, 1997;Goarant et al, 2006;Jayasree et al, 2006;Soto-Rodriguez et al, 2003, 2010bRattanama et al, 2009;Lin et al, 2010).…”

‘Bright-red’ syndrome in Pacific white shrimp Litopenaeus vannamei is caused by Vibrio harveyi

“…During shrimp grow-out, many species have been associated with vibriosis, but only a few have been demonstrated to be the etiological agent, with others representing normal microbiota of the shrimp or the environment . Vibrio strains proven to be pathogenic for shrimp include V. parahaemolyticus (red-leg disease syndrome; Alapide- Tendencia & Dureza 1997), V. penaeicida (syndrome 93; Ishimaru et al 1995), V. nigripulchritudo (summer syndrome; Goarant et al 2006), V. alginolyticus (shell disease and loose shell syndrome; Jayasree et al 2006), V. harveyi (AlapideTendencia & Dureza 1997 and V. campbellii (Soto-Rodriguez et al 2003, Rattanama et al 2009, Lin et al 2010.…”