Detection of antimicrobial resistance in Escherichia coli and Salmonella spp. Originated from cultivated oysters and estuarine waters

Abstract

The raising and spreading antimicrobial resistance (AMR) bacteria in humans, animals, and�environment is a serious global public health issue. Improper use of antimicrobial agents can promote resistant bacteria, and as a result, they can circulate in the environment. Contamination of AMR in the environment can increase the risk of AMR distribution in humans, animals, and the environment. Monitoring and surveillance of AMR in the environmental sector are limited compared to animal and human sectors. The objectives of this study were to determine phenotype and genotype of AMR and extended-spectrum beta-lactamase (ESBL) production in�Escherichia coli�and�Salmonella�isolated from cultivated oysters and estuarine waters, to examine serovars of�Salmonella�isolates, and to detect virulence genes in�E. coli�and�Salmonella�isolated from cultivated oysters (n=144) and estuarine water (n=96).�E. coli�(n=409) and�Salmonella�(n=126) isolates were obtained from cultivated oysters and estuarine waters from Phang Nga, Thailand. The predominant serovars of�Salmonella�were Paratyphi B (13.50%), followed by Eastbourne (12.70%), and II (15.87%). The resistance to at least one antimicrobial agent was found in�E. coli�(94.13%) and Salmonella (96.82%). The multidrug resistance�E. coli�(42.60%) and�Salmonella�(23.02%) were observed. The�blaTEM�(31.55%),�tet(A)�(25.44%), and�strA�(14.92%) were the most prevalent resistance genes found in�E. coli�isolates, while sul3�(14.29%),�blaTEM�(11.91%), and�cmlA�(11.91%) were commonly found in resistance�Salmonella. Phenotypic ESBL production was detected in eight�E. coli�isolates from estuarine waters, and two�Salmonella�isolates from oysters. One of
 E. coli�and�Salmonella�isolates that harbored�blaTEM-1�corresponded to broad-spectrum beta-lactamase. However,�four�
 E. coli�isolates harbored�blaCTX-M�genes. The most common virulence genes of�E. coli�isolates were�istx1�(17.85%) and�lt�(11.74%).�For�Salmonella�isolates,�high prevalence of�invA�(76.98%),�stn�(76.98%), and�fimA�(69.05%) were observed. The�E. coli�isolates that resistant to ampicillin were resistant to chloramphenicol and trimethoprim (p<0.0001).�Furthermore, the�E. coli�isolates harboring�stx1�and�stx2�were more likely to�resistant to chloramphenicol than those did not contain virulence genes (p<0.0001). The�Salmonella�isolates that consisted of�invA�and�fimA�were more likely to be resistant to various antibiotics, including ampicillin, chloramphenicol, tetracycline, and trimethoprim.
 In conclusion, oysters and estuarine water are one of the potential AMR hotspots in the environment. Therefore, continuing monitoring and surveillance of AMR should be implemented in the environment.