Thumbnail Image

Theses

Browse

20221
Reset filters
Subject: Veterinary Microbiology × Author: Das, Himasri × Type: Thesis × Thesis Type: Ph.D ×
Reset filters

Search Results

Now showing 1 - 1 of 1
  • Thumbnail Image
    ThesisItemOpen Access
    Biofilm production, associated genes and antimicrobial resistance of escerichia coli isolated from bovine mastitis
    (2022-09) Das, Himasri; Saikia, G K
    Livestock production sector acts as one of the greatest contributors towards economic development of the country. Mastitis is considered to be one of the most common diseases of high yielding dairy cows which can cause decline in the milk production that ultimately leads to great economic loss in both developed and developing countries. Bovine mastitis can be divided into two types, clinical mastitis and subclinical mastitis. The present study was undertaken on phenotypic and genotypic detection of biofilm producing E. coli isolated from bovine mastitic milk and their antimicrobial resistance profile against commonly used selected groups of antibiotics. To carry out the study, a total of 560 quarters from 140 animals of both organized and unorganized dairy farms in and around Guwahati were screened for mastitis by California Mastitis Test (CMT) out of which 108 animals were found positive for mastitis. The overall prevalence of mastitis including clinical (15%) and subclinical form (62.14%) in both types of farms was 77.14%. In quarter wise distribution of mastitis, involvement of hind quarter was found to be more frequent. A total of 33 E. coli were isolated from 108 milk samples of mastitic dairy cows. All the isolates were screened for biofilm producing ability when tested by using on qualitative as well as quantitative detection methods viz., Congo red agar, Christensen tube and Tissue culture plate methods and all of them were found to be biofilm producers. All the E. coli isolates were tested for presence of biofilm associated genes, viz., csgA, fimH and luxS. The csgA gene was detected in 30 (90.90%) isolates, fimH in 31(93.93%) isolates and luxS was found in 30 isolates (90.90%). On relative quantification of mRNA expression of csgD gene revealed that the ΔCT value is significantly and negatively associated with biofilm production (P value<0.05). The E. coli isolates showed 100% sensitivity to Gentamicin, Neomycin and Amoxicillin+Sulbactam followed by Streptomycin (96.97%), Colistin (84.85%), ciprofloxacin and Ceftriaxone+Sulbactam (72.73% to each), Cefoperazone+ Sulbactam (69.70), Enrofloxacin and amoxycillin (63.64% to each) and Ceftriaxone (39.39%). However 100% resistance was observed for Cloxacillin followed by Ampicillin (96.97%) and Sulfadiazine (90.91%) on Disc diffusion test. In the present study, a total of 15 (45.45%) isolates were found to be multidrug resistant. Among all the MDR biofilm producing isolates, 6 were strong biofilm producers, 5 were moderate and 4 were weak biofilm producers and a significant correlation has been found between the strength of biofilm production and presence of MDR isolates (p<0.01). Our present finding has shown that the MIC values of Ceftriaxone, Amoxycillin, Gentamicin, Streptomycin were significantly correlated with strength of biofilm (P value<0.05). Out of 33 E. coli isolates tested, 18 (54.54%) were confirmed as ESBL producers based on double disk synergy test (DDST) and E-test. Further genotypic characterization of ESBL producing E. coli showed that ESBL encoding gene blaCTX-M was detected in 13 (39.39%) isolates with a product size of 585bp, blaSHV gene was detected in 3 (9.09%) isolates with a product size of 393bp and blaTEM gene was detected in 6 (18.18%) isolates with a product size 506bp.