A survey of antibiotic-resistant bacteria in a sewage treatment plant in Thibodaux, Louisiana, USA Travis J. Everage, Raj Boopathy * , Rajkumar Nathaniel, Gary LaFleur, John Doucet Department of Biological Sciences, Nicholls State University, Thibodaux, LA 70310, USA article info Article history: Received 17 January 2014 Received in revised form 21 April 2014 Accepted 13 May 2014 Available online 4 July 2014 Keywords: Sewage treatment Antibiotic-resistant COD Free DNA Genetic transformation abstract Antibiotic resistance is becoming a very large problem throughout the world. Antibiotics are used as prescribed medications to fight infections and prevent secondary bacterial infections during primary viral infections; they are also included in feeds for livestock and poultry. After passing through the human or animal body the antibiotics enter into the wastewater treatment process, where water is processed and cleaned and then returned to the environment. During sewage treatment, antibiotics come in contact with bacteria entering the treatment process, as well as bacteria used in the treatment process. The bacteria exposed to these antibiotics can become resistant during the treatment process and then expose the resistance genes to the environment upon release of treated water from the plant. Bacteria can become resistant via several mechanisms, including spontaneous mutation, induced mu- tation, genetic transformation, conjugation, and transduction. Because of the contact between bacteria and antibiotics during the treatment process, sewage plants are considered prime habitat to create antibiotic-resistant bacteria. There was a lack of research documenting the changes and flow of resis- tance between the stages of the wastewater treatment process or the possibility of uptake of resistant DNA in the environment into which the treated water is released. Therefore, this work was conducted to study the prevalence of antibiotic-resistant bacteria in various stages of sewage treatment. The results show the presence of antibiotic-resistant bacteria in raw sewage, as well as treated sewage. The results also indicate the possible release of antibiotic-resistant free DNA into the final discharge point in the nearby wetland. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction Alexander Fleming discovered the first antibiotic, penicillin, in 1928, when he found that there was a chemical from a bread mold that killed his cultures of Staphylococcus aureus. Penicillin was developed as an antibiotic 10 years later; this was followed by 30 years of active antibiotic research (Colson, 2008). There are now several hundred antibiotics used on humans and animals, sepa- rated into several classes depending on structure and function (Brooks et al., 1995). Antibiotics are normally derived from natural sources such as bacteria, fungi, and sometimes animals, but they can be synthetic (Pel aez, 2006). As a natural consequence of the use of antibiotics, bacteria started to become resistant (Wood and Moellering, 2003). Bacteria can be naturally or intrinsically resistant, or acquire resistance. Bacteria can acquire resistance in more than one way, including natural spontaneous mutations, induced mutations, transduction, conjugation, and transformation (Batzing, 2002). There is no limit to the number of drugs bacteria can become resistant to, and this causes a worldwide problem (Wood and Moellering, 2003). It is known that while humans or animals are taking antibiotics, the pharmaceuticals are excreted from the body in urine or feces (Stolker et al., 2003). It has been found that the excretions also contain metabolites of the antibiotics. Once excreted from the body, the antibiotics enter the wastewater system, eventually entering the sewage treatment plant (McQuillan et al., 2002). The majority of sewage treatment plants use three different treatment phases, one of which includes the use of bacteria to decompose organic matter (Bauman, 2004). It has been found that the bacteria used in the sewage treatment plant as bioremediators can become resistant to antibiotics, and ultimately pass the resistance genes to the envi- ronment through the plant's discharge (Alighardashi et al., 2009). The differences in wastewater treatment plant design and operation influence the fate of resistant bacteria and resistance * Corresponding author. Tel.: þ1 (985) 448 4716; fax: þ1 (985) 493 2496. E-mail address: Ramaraj.Boopathy@nicholls.edu (R. Boopathy). Contents lists available at ScienceDirect International Biodeterioration & Biodegradation journal homepage: www.elsevier.com/locate/ibiod http://dx.doi.org/10.1016/j.ibiod.2014.05.028 0964-8305/© 2014 Elsevier Ltd. All rights reserved. International Biodeterioration & Biodegradation 95 (2014) 2e10