ANTIMICROBIAL RESISTANCE AND MOLECULAR CHARACTERIZATION OF ESCHERICHIA COLI ISOLATED FROM MILK AND MILK PRODUCTS IN CHHATTISGARH
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Date
2022-10-10
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Dau Shri Vasudev Chandrakar Kamdhenu Vishwavidyalaya Durg
Abstract
Milk is a major part of human food and plays a prominent role in the
human diet. Milk and milk products contain high moisture and are rich in vitamins
and minerals. Hence, its high nutritional value provides the ideal environment for
bacterial multiplication. Raw milk and milk products were contaminated under
unhygienic conditions. For milk to be safer for consumers it must be reasonably
free from microbes, such as Escherichia coli. The present study was undertaken to
isolate and identify the E. coli of public health significance in raw milk and milk
products along with their antibiogram pattern. A total of 200 samples (120 raw
milk and 80 milk products samples) were collected from Durg, Raipur, Bilaspur,
and Rajnandgaon districts of Chhattisgarh and analyzed for the isolation and
identification of E. coli by conventional cultural technique and further confirmed
by biochemical test and molecular techniques. All E. coli isolates were also tested
for their antibiotic susceptibility pattern by disc diffusion technique against 7
antibiotics. Prevalence of Extended Spectrum Beta-Lactamase (ESBL) genes
(blaCTX-M, blaSHV, blaTEM) and other resistance genes (tetA, tetB, gyrA and parC)
among E. coli isolates were also determined. A total of 63 E. coli isolates were
recovered from 200 raw milk and milk product samples, with an overall prevalence
of 31.5%. All isolates were genotypically confirmed by PCR-based molecular method
by targeting 16S rRNA gene.
Out of 63 isolates, 38.33 % (n=46) were isolated from raw milk and 21.25
% (n=17) were isolated from milk products. All isolates were found sensitive to Oxytetracycline and Ciprofloxacin whereas the majority of isolates showed
multiple antibiotics resistance. Maximum resistance was observed against
Amoxyclav (88.88%) and Amoxycillin (87.30%). The highest Multiple Antibiotic
Resistance (MAR) index of 1 was observed for 2 isolates and MAR index for all
E. coli isolates varied between 0.14 to 1.
All 63 E. coli isolates were further screened by phenotypic method for
ESBL production and 25 E. coli isolates were identified as presumptive ESBL
producers. All 25 isolates were found positive either for blaCTX-M, blaSHVand
blaTEM genes by molecular technique. Among 25 presumptive ESBL E. coli
isolates, 8 (12.69 %) isolates harbored blaTEM,, 9 (14.28 %) isolates harbored
blaCTX-M gene and 8 (12.69 %) isolates displayed expression for blaSHV gene.
Among 13 Tetracycline-resistant isolates, 7 (53.84%) isolates harbored tetA gene
whereas only 1 (7.69%) isolate harbored tetB gene. Among 12 Fluoroquinolone
resistant isolates, 4 (33.33%) contained gyrA gene whereas 6 (50%) isolates
contained parC gene. ESBL causes a rapid increase of multidrug-resistant bacteria
and also reduces the efficacy of a wide range of β- lactam antibiotics. Antibiotics
are regularly added to feed as feed additives in intensive animal production at subtherapeutic
doses to stimulate growth, improve feed efficiency, and avoid
infections. The presence of ESBL-producing E. coli in raw milk is a serious
public health threat. However, all pathogenic microorganisms are destroyed after
pasteurization, including resistant bacteria, making milk and other milk products
generally safe for human consumption.