ABSTRACT
AIM: Serratia marcescens wound infection after snakebite is often associated with aggressive presentations. However, the virulence determinants remain understudied. MATERIALS & METHODS: Whole-genome sequencing was performed on S. marcescens VGH107, an isolate from wound infection secondary to Trimeresurus mucrosquamatus bite. Comparative genomics approach coupled with multivirulent-locus sequencing typing was applied to systematically predict potential virulence factors. RESULTS: Multivirulent-locus sequencing typing indicated VGH107 falls within the cluster of high pathogenic strains. Comparative analysis identified virulence genes unique in VGH107, including ecpD and ecpE genes for periplasmic chaperone-pilus subunit complex and cdiA and cdiB genes for contact-dependent growth inhibition system. CONCLUSION: The data established here provide foundation for further research regarding the virulence and resistance of S. marcescens.
Subject(s)
Genome, Bacterial/genetics , Serratia Infections/microbiology , Serratia marcescens/genetics , Serratia marcescens/pathogenicity , Snake Bites/microbiology , Trimeresurus/microbiology , Wound Infection/microbiology , Animals , DNA, Bacterial/genetics , Drug Resistance, Multiple, Bacterial/genetics , Genes, Bacterial , Humans , Male , Middle Aged , Multilocus Sequence Typing , Phylogeny , Sequence Analysis, DNA , Serratia Infections/etiology , Snake Bites/complications , Taiwan , Virulence Factors/genetics , Wound Infection/etiologyABSTRACT
OBJECTIVE: To determine the oral bacterial flora associated with two common local venomous snakes in Hong Kong, namely the Chinese cobra (Naja atra) and the bamboo pit viper (Trimeresurus albolabris). DESIGN: Cross-sectional study. SETTING: A non-government organisation and a regional hospital in Hong Kong. SUBJECTS: Thirty-two Chinese cobras and seven bamboo pit vipers. MAIN OUTCOME MEASURES: Species identification of bacteria in the oral cavity of both snakes and their antibiotic susceptibilities. RESULTS: The oral cavity of Chinese cobra harbour a wide range of pathogenic bacteria, including: Gram-negative bacterial species like Morganella morganii, Aeromonas hydrophila and Proteus, and Gram-positive bacteria like Enterococcus faecalis, coagulase-negative Staphylococcus as well as anaerobic species (clostridia). The oral cavity of the Chinese cobra is more likely than that of the bamboo pit viper to harbour pathogenic bacteria associated with snakebite infection (P<0.001). The median number of pathogenic bacteria per snake was significantly higher in the Chinese cobra (P<0.001). All pathogenic Gram-negative bacteria isolated were susceptible to levofloxacin. Amoxicillin/clavulanate provided good coverage against pathogenic Gram-positive bacteria (Enterococcus faecalis) and anaerobes. CONCLUSION: 'Prophylactic' antibiotic treatment for Chinese cobra bites may be beneficial, owing to the multiple pathogenic bacteria in its oral cavity and the higher risk of ensuing necrosis. The regimen of levofloxacin plus amoxicillin/clavulanate appears promising for this purpose, but further study is required to confirm its clinical utility in patients.
