Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul Evidence of antibiotic resistance in Enterobacteriales isolated from green sea turtles, Chelonia mydas on the Great Barrier Reef Md. Shamim Ahasan a,⁎ , Jacqueline Picard a , Lisa Elliott b , Robert Kinobe a , Leigh Owens a , Ellen Ariel a a College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville 4811, Quensland, Australia b AusPhage, 10 Heather Avenue, Rasmussen, Queensland, 4811, Australia ARTICLE INFO Keywords: Antibiotic resistance Enterobacteriales Enteric bacteria Green sea turtle Great Barrier Reef ABSTRACT This study investigated Enterobacteriales and their antimicrobial resistance in green sea turtles captured adjacent to the central Great Barrier Reef (GBR) and proximate to urban development. Cloacal swabs were taken from 73 green turtles between 2015 and 2016. A total of 154 out of 341 Gram-negative bacterial isolates were identified as Enterobacteriales that represent 16 different species from 9 different genera. The dominant isolates were Citrobacter (30.52%), Edwardsiella (21.43%) and Escherichia (12.34%). The resistance against 12 antibiotics belonging to 6 different classes was determined. The isolates showed highest resistance to β-lactam antibiotics (78.57%) followed by quinolone (50%) and tetracycline classes (46.1%). Approximately one-third (37.7%) of the isolates identified exhibited multidrug-resistance. Isolates recovered from rehabilitated turtles were significantly multidrug resistant (p < 0.009) compared to isolates from other study sites. These results provide baseline information on antimicrobial resistance while revealing gaps for further research to evaluate the level of pollution in the GBR. 1. Introduction Since the World Health Organisation (WHO) first considered the emergence of antimicrobial resistance to be of global concern in the 1980s, the number of types of multi-resistant bacterial strains has continued to increase, outpacing the development of effective anti- biotics (Frieri et al., 2016; Grundmann et al., 2011). The Enterobacter- iales being ubiquitous are easily able to exchange genetic materials including those that code for antimicrobial resistance. These facultative anaerobes usually present as commensal intestinal flora in terrestrial animals, including humans (Bonelli et al., 2014). Several genera of Enterobacteriales are responsible for a number of serious, life-threaten- ing infections in humans such as acute gastritis, urinary tract and respiratory tract infections (Kresken et al., 2016; Najjuka et al., 2016; Wright, 2010). The Great Barrier Reef (GBR) situated off the east coast of Queensland is the largest and most diverse ecosystem on the planet. This world heritage site is managed by the Great Barrier Reef Marine Parks Authority (GBRMPA) who have identified risks and vulnerable animals in the Great Barrier Reef Biodiversity Conservation Strategy 2013 (GBRMPA, 2013). In this document it was indicated that the inshore areas of the GBR were under greatest threat as a result of human-related activities and that they should be better investigated. Furthermore, experts identified a need to evaluate the level of contamination in the GBR of antimicrobial resistance of microbes and the potential role of marine megafauna as their reservoir (Koenig et al., 2011; Webster and Hill, 2007). Aquatic environments can become contaminated from a variety of sources including urban surface run-off and effluent discharges (Goni- Urriza et al., 2000; Wellington et al., 2013). This suggests that aquatic fish, mammals and reptiles have the potential to harbor antibiotic resistant bacteria and studies involving several marine reptiles, includ- ing sea turtles, support the notion that antibiotic resistant bacteria are present in the marine environment (Al-Bahry et al., 2011; Foti et al., 2009; Santoro et al., 2006; Stewart et al., 2014; Wallace et al., 2013; Wheeler et al., 2012). Green sea turtles, Chelonia mydas, have several characteristics that make them a good bio-indicator for environmental health. With a long life-span and high site fidelity to coastal foraging habitats, green sea turtles are exposed long-term to coastal anthropogenic factors and are prime reservoir candidates for antibiotic resistant bacteria originating from urban run-off. Their reproduction migration inevitably takes them across international borders and exposes them to significant environ- mental stressors (Foti et al., 2009; Read et al., 2014). These challenges http://dx.doi.org/10.1016/j.marpolbul.2017.04.046 Received 24 February 2017; Received in revised form 24 April 2017; Accepted 25 April 2017 ⁎ Corresponding author. E-mail address: mdshamim.ahasan@my.jcu.edu.au (Md. S. Ahasan). Marine Pollution Bulletin xxx (xxxx) xxx–xxx 0025-326X/ © 2017 Elsevier Ltd. All rights reserved. Please cite this article as: Ahasan, Md. S., Marine Pollution Bulletin (2017), http://dx.doi.org/10.1016/j.marpolbul.2017.04.046