Isolation, Pathotyping and Drug Susceptibility Pattern of Escherichia coli Isolates from Diarrheic Piglets

Background: Multidrug resistant strains of Escherichia coli have been causing worldwide outbreaks of food borne diseases in recent years. The emergence of antibiotic-resistant strains of E. coli and the occurrence of transmissible drug resistance among the organism has amplified the complications associated with its control and treatment measures. Data associated with the prevalence, virulence factors and antimicrobial susceptibility of E. coli isolates are needed to be studied in order to develop an effective control strategy for colibacillosis in piggeries. The goal of the investigation was to study the antimicrobial susceptibility pattern and pathotyping of E. coli isolates from diarrhoeic piglets. Methods: 102 rectal swab samples were collected from diarrhoeic piglets of ICAR-AICRP/MSP on Pig, College of Veterinary Science, Assam Agricultural University, Khanapara, ICAR-National Research Centre on Pig, Rani, Guwahati, Assam and from different unorganized farms of the state. These samples were then inoculated in Luria Bertani (LB) broth and incubated aerobically at 37oC for 24 hours followed by sub culturing them in MacConkey’s lactose agar (MLA) and Eosin Methylene Blue (EMB) agar for purification of the suspected E. coli isolates. The isolates were characterized by biochemical tests and motility tests and were pathotyped based on detection of specific virulence genes by multiplex Polymerase Chain Reaction (PCR). Result: Out of 102 rectal swab samples examined, 92 (90.2%) yielded E. coli which included 41 (91.12%) of 45 samples collected from ICAR-AICRP/MSP on Pig, College of Veterinary Science, Assam Agricultural University, Khanapara and 32 (88.89%) of 36 samples from ICAR-National Research Centre on Pig, Rani, Guwahati, Assam and 19 (90.48%) of 21 samples from different unorganized farms. All the 92 E. coli isolates were examined for the presence of stx1, est1, elt1 and eaeA genes using specific primers. Among these isolates, 25 (27.17%) were positive for stx1 gene, 18(19.56%) for est1 gene, 6(6.52%) for elt1 gene, 3 (3.26%) for both genes est1 and elt1 and 12 (13.04%) for eaeA gene. Antimicrobial susceptibility pattern of the isolates revealed that the highest percentage (71.74%) of the isolates were resistant to tetracycline and the least (4.34%) to imipenem.