Thumbnail Image

Thesis

Browse

20221
Reset filters
Subject: Veterinary Microbiology × Author: LOKESWARI, R × End date: 2022 × Start date: 2022 × Thesis Type: M.V.Sc. ×
Reset filters

Search Results

Now showing 1 - 1 of 1
  • Thumbnail Image
    ThesisItemOpen Access
    ASSESSMENT OF ANTIBIOGRAM AND DETECTION OF GENETIC DETERMINANTS OF SELECTED VIRULENCE FACTORS IN AVIAN PATHOGENIC ESCHERICHIA COLI ISOLATES OF CHICKEN
    (SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA, 2022-05) LOKESWARI, R; SIVARAMA KRISHNA, G(MAJOR); ANAND KUMAR, P; GANGU NAIDU, S
    The present study was taken up for understanding the pathogenic potential and prevalence of antibiotic resistance pattern of avian E. coli strains, isolated from colibacillosis affected chickens by both traditional and molecular methods. A total of 105 samples were collected from the internal organs of colibacillosis affected chickens. Based on morphological, cultural and biochemical characterization viz., Gram staining, growth pattern on EMB agar, lactose fermentation on MacConkey agar, IMViC tests (Indole, Methyl Red, Voges-Proskauer, Citrate), Catalase, Nitrate, Oxidase and Urease tests, E. coli was isolated and characterized from 81 samples (77.14%) out of 105 samples collected. The gene coding for 16S rRNA is highly conserved among species/strains of Escherichia genus was detected in all the 81 E. coli isolates by PCR. In congo red dye uptake assay, all the isolates produced orange red to red color colonies, indicating their invasiveness and pathogenic potential. Out of 81 isolates, the production of hemolysin was phenotypically characterized in 74 (91.4%) isolates, of which 39 (48.2%) isolates are ɑ-hemolytic and 35 (43.2%) are Entero-hemolytic on 10 per cent sheep blood agar. The biofilm production was assessed by qualitative tests like Christensen borosilicate glass tube method and polypropylene tube method, and quantitatively by tissue culture plate method (TCP). Among the qualitative methods the polypropylene tube method (89.47% Sensitivity and 91.66% Specificity in comparison to TCP method) was found to be superior to the borosilicate tube method (77.1% sensitivity, 83.3% specificity in comparison to TCP method). In TCP method, 61 isolates (75.3%) were quantitatively characterized as biofilm producers, which is the most reliable method. In Embryo lethality test, based on the % embryo death rate, 52 isolates were characterized as highly pathogenic strains, 24 isolates were characterized as moderately pathogenic and five isolates were characterized as low pathogenic strains. A total of eight genes were targeted for the identification of genetic determinants of virulence factors for all the 81 avian pathogenic E. coli isolates. The hlyF gene was detected in four isolates viz., F6, H1, H2 and H3, iroN gene was detected in five isolates viz., B3, B4, B5, D1 and D3, whereas eaeA gene was detected only in H3 isolate. The genes iss, ompT, stx1, stx2 and hlyA were detected in none of the isolates tested. All the isolates were found to be multidrug resistant with a Multiple antibiotic resistance index (MAR) of more than 0.2 as assessed by disc diffusion method. The occurrence of genes coding for extended spectrum β-lactamase (ESBL) were assessed in multiplex PCR and a prevalence of 86.27 per cent of blaTEM, 3.7 per cent of blaOXA and 0 per cent of blaSHV was reported in the present study. In conclusion, our study might be the first to assess the pathogenic potential of E. coli from colibacillosis affected chickens by both traditional and molecular methods in Andhra Pradesh. The present data on characterization of pathogenic E. coli strains and existence of multidrug resistant strains of E. coli in colibacillosis affected chickens may be useful for developing novel control strategies and vaccines.