Surprising Absence of Antibiotic Resistance in Salmonella enterica Isolates from Galapagos Marine Iguanas (Amblyrhynchus cristatus)

Abstract

Reptilians are known to carry Salmonella enterica, an intestinal bacterial pathogen (for humans and other animals) which is known to carry a cornucopia of antibiotic resistance genes. We cultured fecal matter from marine iguanas in the San Cristobal island and obtained 20 S. enterica isolates which lacked clinical resistance to any of the antibiotics tested. This finding is unexpected because isolates were obtained from a beach visited by tourists, close to the San Cristobal town in San Cristobal island. This island houses many domestic and peri-domestic animals known to carry S. enterica and antibiotic-resistant bacteria. It is important to understand whether this lack of antibiotic resistance is due to genetic isolation of Salmonella and these marine iguanas from those in domestic animals. We discuss the potential zoonotic transmission of strains from wildlife.