Antibiotic resistance and virulence genes of extraintestinal pathogenic Escherichia coli from tropical estuary, south India

Introduction: Escherichia coli strains can cause a variety of intestinal and extraintestinal diseases. Extraintestinal pathogenic E. coli (ExPEC) strains have the ability to cause severe extraintestinal infections. Multidrug resistance among ExPEC could complicate human infections. Methodology: Escherichia coli strains were isolated during the period of January 2010 to December 2012 from five different stations set at Cochin estuary. Susceptibility testing was determined by the disk-diffusion method using nine different antimicrobial agents. A total of 155 strains of Escherichia coli were screened for the presence of virulence factor genes including papAH, papC, sfa/focDE, iutA, and kpsMT II associated with ExPEC. Results: Among the 155 E. coli isolates, 26 (16.77%), carried two or more virulence genes typical of ExPEC. Furthermore, 19.23% of the ExPEC isolates with multidrug resistance were identified to belong to phylogenetic groups B2 and D. Statistically significant association of iutA gene in ExPEC was found with papC (p < 0.001) and kpsMT II (p < 0.001) genes. ExPEC isolates were mainly resistant to ampicillin (23.07%), tetracycline (19.23%), co-trimoxazole (15.38%), and cefotaxime (15.38%). The adhesion genes papAH and sfa/focDE were positively associated with resistance to gentamicin, chloramphenicol, and cefotaxime (p < 0.05). Conclusions: Co-occurrence of virulence factor genes with antibiotic resistance among ExPEC poses considerable threat to those who use this aquatic system for a living and for recreation.