Biofilm production, associated genes and antimicrobial resistance of escerichia coli isolated from bovine mastitis
Loading...
Date
2022-09
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
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.