Identity and virulence properties of Aeromonas isolates from healthy Northern snakehead ( Channa argus ) in China

Abstract

Members of the genus Aeromonas are opportunistic pathogen of a variety of aquatic animals that exhibits multidrug resistance, phenotypes, virulence genes and virulence. The present study described the species distribution and the potential pathogenicity of Aeromonas isolated from healthy Northern snakehead (Channa argus) in China. Molecular identification revealed that A. veronii biovar veronii (69/167; 41·3%) and A. hydrophila (41/167; 24·6%) were the most common species found in Northern snakehead intestine based on sequencing of the 16S rRNA gene and DNA gyrase subunit B protein. The distribution of seven virulence factors including aer (84·4%), act (80·8%), ser (40·1%), Aha (27·5%), lip (23·4%), exu (15·0%) and LuxS (12·6%) were determined exclusively in Aeromonas isolates. All the seven virulence genes were present in 9·6% (16/167), among which 11 strains were identified as A. veronii biovar veronii. For the strains harbouring seven virulence genes, the 50% lethal doses (LD50) of isolates were lower compared to the isolates carrying two virulence genes. The challenge tests revealed that isolate W31 had the lowest lethal dose, causing 50% mortality at 4·5 × 103 colony‐forming units (CFU) per ml. Furthermore, histopathology of Northern snakehead infected with Aeromonas strains showed necrosis and congestion in liver, spleen and kidney and also damage to the intestine. This study confirms that the Aeromonas strains isolated from healthy Northern snakehead may be a cause of concern for public health. Significance and Impact of the Study Aeromonas species are widely distributed in aquatic environments and have considerable virulence potential. The aim of this study was to identify Aeromonas strains isolated from healthy Northern snakehead, and to investigate if Aeromonas species isolated from healthy fish potential pathogenicity with special reference to virulence and epidemiology studies.

Aeromonas veronii Infection in Commercial Freshwater Fish: A Potential Threat to Public Health

“…In recent years, there have been an increasing numbers of cases of large-scale A. veronii outbreaks. It has been reported that A. veronii can infect freshwater fish, amphibians, birds, and red meat animals, resulting in serious losses to the aquaculture industry and threatening food safety [2][3][4]. In addition, A. veronii can also cause human infections, especially in elderly and children with low immunity, causing sepsis, gastroenteritis, and other diseases [5][6][7][8][9][10][11].…”

“…There has been a variety of proven virulence factors, including outer membrane proteins, motility related factors, toxins, proteases, quorum sensing systems, secretion systems, and iron ion acquisition systems, among others [16,17]. Related research demonstrated that hemolytic and cytotoxic activities and pathogenicity were correlated with the presence of virulence genes in Aeromonas strains [4]. Those virulence factors play an important role in the development of disease.…”

Functional Analysis of preA in Aeromonas veronii TH0426 Reveals a Key Role in the Regulation of Virulence and Resistance to Oxidative Stress

“…The pellets were washed three times with PBS. For the pH tolerance test, the washed pellets were resuspended in PBS at different pH values (3,4,5,6,7,8,9, and 10) at 28 • C. For the oxidative stress test, the washed pellets were resuspended in PBS containing 1 mM H 2 O 2 for 1 h at 28 • C. For the temperature stress test, the washed pellets were incubated in PBS for 1 h at 55 • C. For the osmotic tolerance test, the washed bacteria were plated directly on an LB solid plate containing 0.4 M NaCl at 28 • C for 24 h, after which colonies were counted. The pellets were resuspended 1 mL of sterile PBS for 1 h at 28 • C and regarded as blank controls in all tolerance tests.…”

“…In recent years, a growing number of cases of large-scale A. veronii outbreaks have resulted in the infection of freshwater fish, livestock, birds, and red meat animals (such as camels). These events can cause severe losses to the breeding industry and threaten food hygiene and safety [2][3][4]. Moreover, A. veronii has been reported to be the etiological agent of gastrointestinal infections and a wide spectrum of extra-intestinal infections, including wound infection, septicemia, urinary tract and soft tissue infections, and septic arthritis in humans [5].…”

Comparative proteomic analysis reveals novel potential virulence factors of Aeromonas veronii

“…6 While causing substantial economic losses in the aquaculture industry, it also seriously threatens human health. 3,5,7 Reports of A. veronii cases are increasing, and related studies show that its pathogenicity is influenced by multiple factors. 3 However, current research on A. veronii is aimed mainly at studying common virulence factors, such as outer membrane proteins, pili, flagella, aerolysin, hemolysin, enterotoxin, proteases, and some adhesion factors, so pathogenesis has not completely been characterized.…”