STUDIES ON AIRBORNE DISSEMINATION OF ANTIBIOTIC RESISTANT GENES THROUGH ESCHERICHIA COLI IN DAIRY FARMS
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Date
2024-02-09
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Dau Shri Vasudev Chandrakar Kamdhenu Vishwavidyalaya Durg
Abstract
Antibiotic resistance genes (ARGs) are a paramount global concern.
Livestock farms, particularly dairy facilities, are significant contributors to the
dissemination of ARGs into the environment due to extensive antibiotic use in animal
husbandry. Ubiquitous presence of E. coli in dairy farm air suggests that it can serve
as a vector for transmitting ARGs to the external environment. The present study
aimed to investigate the prevalence and distribution of ARGs in E. coli isolates
collected from various sources within dairy farms, with a focus on airborne
transmission. A total of 120 samples, comprising of air (n=90), fecal (n=15) and milk
samples (n=15) were collected from 5 dairy farms located in and around Durg district
of Chhattisgarh and processed for the isolation and identification of E. coli using
conventional cultural techniques, which were further confirmed by biochemical tests
and molecular techniques. All E. coli isolates were also tested for their antibiotic
susceptibility pattern against 10 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 was also determined. Enterobacterial
repetitive intergenic consensus polymerase chain reaction (ERIC-PCR) was also
performed to determine genetic similarity among the isolates recovered from different
samples. A total of 121 isolates comprising air (66), fecal (27), milk (28) were
recovered. All isolates were genotypically confirmed by PCR-based molecular
method by targeting 16S rRNA gene. In all E. coli isolates maximum resistance was
observed against Cephalexin (97.52%), Cifixime (88.42%) and Cefotaxime (86.77%).
Highest Multiple Antibiotic Resistance (MAR) of 1 was observed for 1 isolate and
MAR index for all isolates varied between 0.2 to 1. On screening 67 multi drug
resistant (MDR) E. coli isolates for ESBL production by phenotypic method 47
(70.14%) isolates were identified as presumptive ESBL producers and 23 (34.32%),
25 (37.31%), and 1 (1.49%) isolates displayed expression of blaTEM, blaCTX-M, and
blaSHV gene, respectively. Among 15 phenotypically tetracycline-resistant E. coli
isolates, 12 (80%) isolates harboured the tetA gene and 6 (40%) isolates harboured
the tetB genes. Among 56 phenotypically fluoroquinolone-resistant E. coli isolates,
all 56 isolates (100%) were confirmed to carry the gyrA and parC genes. The ERIC PCR dendrogram analysis of air, fecal, and milk isolates revealed a range of
similarity between 25% to 78%, indicating a genomic diversity within the dairy farm
environment.
This study highlighted the need of comprehensive strategies to address
antibiotic use in animal husbandry practices and to mitigate the transmission of ARGs
through airborne pathways, particularly via E. coli in dairy farm environments.