Antibacterial activities of serum from the Komodo Dragon (Varanus komodoensis)

Abstract

Komodo dragons (<em>Varanus komodoensis</em>) are able to feed on large prey items by injecting a dose of toxic bacteria with their bite that, over time, kills the prey by systemic infection. Dragons also suffer bites from other members of their own species during territorial disputes and feeding frenzies. However, they do not suffer the same fate as their prey, suggesting that they have developed a strong immunity to bacterial infections. This study was undertaken to determine the antibacterial activities of serum from the Komodo dragon. Bacterial cultures were treated with different volumes serum from <em>Varanus komodoensis </em>and the growth was monitored by optical density at 430 nm. In addition, the serum was treated with protease, chelators of divalent metal ions, or with mild heat to determine the mechanism of antibacterial activities. Treatment of bacterial cultures with serum from Komodo dragons (<em>Varanus komodoensis</em>) resulted in a volume-dependent decrease in bacterial growth. Cultures of <em>Escherichia coli</em>, <em>Staphylococcus aureus</em>, and <em>Klebsiella oxytoca</em> exhibited moderate-strong growth inhibition by <em>V. komodoensis</em> serum, while cultures of <em>Streptococcus epidermitis</em>, <em>Salmonella typhimurium</em>, <em>Providencia stuartii</em>, and<em> Shigella flexneri</em> were nearly completely obliterated for 24 h by only 10% (v/v) serum. The antibacterial activity of<em> V. komodensis</em> serum occurred very rapidly, as 18% of E. coli growth was inhibited by a five min exposure to serum. Furthermore, 10- and 20-min incubations of <em>E. coli</em> with serum from <em>V. komodoensis</em> resulted in 43 and 68% inhibition of bacterial growth, respectively. The bactericidal capacity of the serum against <em>E. coli</em> was 2,075,000 bacteria/μL serum, and was inhibited by mild heat treatment, pronase, EDTA, and phosphate, indicating that the anti-bacterial action is most probably due to the presence of a potent serum complement protein system

Plasma antibacterial activities in ornate (Terrapene ornata) and eastern box turtles (Terrapene carolina)

“…Repeated exposure to potentially pathogenic bacteria via the fecal‐oral route may explain the more robust plasma antibacterial ability of ornate box turtles against these organisms. This activity is similar to that observed in Komodo dragons (Merchant, Henry, et al, 2013), yellow‐bellied sliders ( Trachemys scripta ; Haskins, Hamilton, Jones, et al, 2017; Haskins, Hamilton, Stacy, Finger, & Tuberville, 2017), and eastern mud turtles ( Kinosternon subrubrum ; Cochran et al, 2018), and superior to values reported for red‐eared sliders (Zimmerman, Paitz, et al, 2010), common snapping turtles (Baker, Kessler, & Merchant, 2019), alligator snapping turtles (Baker, Kessler, & Merchant, 2019), gopher tortoises ( Gopherus polyphemus ; Goessling, Guyer, & Mendonça, 2016; Goessling, Guyer, & Mendonça, 2017; Goessling, Koler, et al, 2017; Sandmeier et al, 2016; Sandmeier et al, 2018) and prairie rattlesnakes (Baker & Merchant, 2018a).…”

“…This may be due to the robust innate immune response against Salmonella spp. demonstrated by many apparently‐healthy wild reptiles, including EBT and OBT from the present study, common snapping turtles ( Chelydra serpentina ; Baker, Kessler, & Merchant, 2019), Komodo dragons ( Varanus komodoensis ; Merchant, Henry, Falconi, Muscher, & Bryja, 2013), and several species of crocodilians (Merchant et al, 2006; Merchant, Roche, Elsey, & Prudhomme, 2003).…”

“…The exact reason for the disparity in box turtle antibacterial activity against different Staphylococcus spp. is unclear, but incomplete killing of S. aureus is also observed in common snapping turtles (Baker, Kessler, & Merchant, 2019), alligator snapping turtles ( Macrochelys temminckii ; Baker, Kessler, & Merchant, 2019), prairie rattlesnakes ( Crotalus viridis ; Baker & Merchant, 2018a), and Komodo dragons ( Varanus komodoensis ; Merchant, Henry, et al, 2013). Like box turtle plasma, Komodo dragon serum effectively inhibits growth of S. epidermidis , potentially indicating a conserved innate immune response to members of this genus (Merchant, Henry, et al, 2013).…”

Characterization of Phospholipase A2 Enzyme Activity in Serum of the Komodo Dragon (Varanus komodoensis)Soluble phospholipase A2 (sPLA2) is an enzyme found in the peripheral circulation of vertebrates which has significant immunological activity. This en

“…The curve appeared to be asymptotic in nature, approaching a maximum product formation of approximately 85-90 nmol. This strong activity is not surprising considering the potent and broad-acting antibacterial activity of the Komodo dragon serum [11], and also the effective serum complement activity [12] previously described for these animals. These animals are known to have a broad spectrum of both gram positive and negative bacterial species in their saliva [22].…”

“…Several recent studies have characterized antibacterial activity [11], serum complement [12], and dipeptidyl peptidase [13] activities of serum from the Komodo dragon. In addition, these animals have been reported to express antimicrobial peptides [14].…”