Influence of tetracycline exposure on tetracycline resistance and the carriage of tetracycline resistance genes within commensal Escherichia coli populations

Abstract

Aims: To assess the influence of incremental tetracycline exposure on the genetic basis of tetracycline resistance within faecal Escherichia coli. Methods and Results: Through the adoption of a novel combination of multiple breakpoint selection, phenotypic characterization and the application of a polymerase chain reaction based gene identification system it proved possible to monitor the influence of antibiotic exposure on resistance gene possession. Using tetracycline as a case study a clear hierarchy was revealed between tet genes, strongly influenced by host antimicrobial exposure history. Conclusions: The antimicrobial exposure regime under which an animal is produced affects both the identity and magnitude of resistance gene possession of a selected bacterial population within its enteric microflora. Among the ramifications associated with such resistance gene selection is the degree of resistance conferred and the carriage of linked resistance determinants. This selection is applied by exposure to antibiotic concentrations well below recognized minimum inhibitory tetracycline concentration breakpoints widely adopted to characterize bacterial ÔsusceptibilityÕ. Significance and Impact of the Study: This study confirms the ability of minimal antibiotic exposure to select for the continued persistence of resistance genes within the enteric microflora. It is clearly demonstrated that different antimicrobial regimes select for different resistance genes, the implications of which are discussed.

Prevalence and antimicrobial susceptibility of bacterial pathogens isolates from diseased swine in southwest, China

“…The E. coli isolates assessed in this study displayed similar levels of resistance to tetracyclines, ampicillin, gentamicin and fluoroquinolones as were previously reported for E. coli strains isolated from diseased swine in China by Tian et al (2009). High levels of resistance to tetracycline (~60-95%) have also been detected in E. coli isolates recovered from apparently healthy swine on-farm or at slaughter in other countries (Kozak et al, 2003;KijimaTanaka et al, 2003;Teshager et al, 2000;Blake et al, 2003). Most of E. coli isolates (67.3%) from swine were resistant to fluoroquinolones (e.g.…”

Patterns of Efflux Pump Genes Among Tetracycline Resistance Uropathogenic Escherichia coli Isolates Obtained From Human Urinary Infections

“…Several investigations have studied tetracycline resistance in bacteria by examining their ability to grow in the presence of drugs, but these studies are not useful for determining the types of tetracycline resistance determinants responsible for antibiotic resistance in bacteria (7). On the Other hand, molecular microbiology techniques can accurately describe genetic basis of antibiotic resistance in bacteria (18).…”

Antibiotic resistant bacteria used as bioindicators of environmental pollution produced by tertiary treated sewage effluent

“…Karami et al [21] reported that Tc r is an attractive model for studying the ecology of antibiotic resistance. Tc r determinants were detected from different bacteria isolated from different environmental samples [22][23][24]. On the other hand, Al-Bahry et al [5] used molecular techniques for detection of Amp resistant determinants for biomonitoring of marine habitats using multiplex PCR.…”