An investigation of the bacterial profile recovered from the oral cavity of sharks, on the coast of KwaZulu-Natal, South Africa.

Abstract

Shark attacks are a rare occurrence globally; however quick treatment of a contaminated wound is imperative. Failure to treat infections in a timely manner may result in fatalities as marine bacteria have opportunistic qualities. In addition, limited knowledge is available on antibiotic resistance of bacteria associated with marine top-predators. A cross-sectional study was, therefore, performed to investigate the bacterial profile of a shark’s oral cavity. During 2012 to 2013, oral swabs were taken from sharks caught in protective gill-nets along the KwaZulu-Natal coastline in South Africa. Isolates were characterised by Gram-stain morphology and identified using biochemical tests and MALDI-ToF MS (Matrix assisted laser desorption/ionisation time-of-flight mass spectrometer). MICs (minimal inhibitory concentration) were performed using agar dilution against clinically important antibiotics. Data presented includes 205 isolates from 34 sharks. A total of ten species of sharks were caught. Ragged-tooth Carcharias taurus was the most frequently caught at 24% (8/34), the least frequent was smooth hammerhead Sphyrna lewini and copper Carcharhinus brachyurus at 3% (1/34). The highest prevalence of bacterial isolates were found in great white, Carcharodon carcharias (20%), scalloped hammerhead Spyrna lewini (16%) and mako Isurus oxyrhincus (14%) sharks. A Pearson correlation was used to calculate the similarities between sharks based on bacterial assemblages and shark-phylogeny. A trend was seen, however, no statistical significance was found. A plausible connection could be established with a higher sample number. In this study Micrococcus, Staphylococcus, Vibrio and Pseudomonas species rank among the four most frequently found bacteria in sharks. MICs revealed bacterial resistance of 50% to cefuroxime, 38% to ampicillin, 18% to nalidixic acid, 14% to tetracycline, 11% to erythromycin, 10% to ceftriaxone and lowest is 2% to ciprofloxacin. No resistance to gentamicin was found, highlighting its value in wound management. This primary data suggests the presence of clinically important bacteria in sharks transferable to humans, requiring specific treatments regimes.