Environmental and Genetic Factors Affecting Antibiotic Resistance of Extended Spectrum β-Lactamase Bacteria from the Rio Grande River in El Paso, TX and CD. Juarez, Mexico

Background: The Rio Grande River provides a major source of potable and agricultural water for the population of the Texas/Mexico border region. Cattle farming and ranching are the most prevalent activities, which may contribute to the microbial burden of pharmaceuticals into our state’s water resources. Antibiotics, presumably released into the environment by discharges originating from waste-water treatment plants, septic disposal systems, animal feeding operations and urban runoff have a definite impact on the ecosystem and may contribute to an increase in antibiotic resistance. We hypothesized that waters of the Rio Grande River contained Multi Drug Resistant Organisms (MDRO) and mobile genetic elements. This could represent a serious public health concern for residents in the El Paso/Juarez, Mexico border. Human health consequences as a result of antimicrobial resistant bacteria may include: increased number of infections, increased frequency of treatment failure, increased severity of infections and increase health cost. Purpose: The main objective of this research study was to determine the presence of selected genetic antimicrobial biomarkers such as Extended Spectrum Beta Lactamase genes (ESBL), mobile genetic elements, integrons (class I and class II), and to screen for Carbapenem Resistant (CRE) Enterobacteria in a 26 km segment of the Rio Grande River. Methods : Water and sediment samples were obtained from the Rio Grande River. DNA was extracted from both isolated bacteria and directly from water and sediment. Amplification of selected resistant biomarkers (TEM, SHV and CTX genes) and integrons (class I and II), was accomplished by polymerase chain reaction (PCR). Screening for CRE bacteria was done by culture on CHROMagar Chromogenic Media. Results: Analysis of water samples (15) collected at five different time periods throughout the year showed that 73.3% contained ESBL genes and integrons. Among these, 60% were TEM and/or 46.7% were CTX-M. Integrons were identified in 11 water samples (73.3%). Also, a total of 310 xv bacterial isolates were recovered, from which 142 bacterial isolates were characterized as 18 different genera of bacteria. From these, 91 (64%) were resistant to at least 2 or more combinations of antibiotics and 105 (74%) were multi-resistant to more than 4 different antibiotics. 28 isolates were identified as Gram negative bacteria with multiple drug resistant patterns and therefore included in this study for the molecular analysis of ESBL genes. From these, 22 (78.6%) were positive for the presence of one or more ESBL and 11 (39.3%) were positive for CRE. TEM was identified as the most prevalent ESBL gene of resistance in both, water and bacterial isolates samples. Conclusions: To our knowledge, characterization of genes responsible for antibiotic resistance in the El Paso-Cd. Juarez region had never been performed previously. These findings may contribute to improve preventive measures and policies in the management of infectious diseases and our environment natural resources