Genotypic and phenotypic situation of antimicrobial drug resistance of Escherichia coli in water and manure between biogas and non-biogas swine farms in central Thailand.

Currently, Thai livestock is rapidly expanding, especially the production of ruminants, chicken, and swine. The improper use of antibiotics will probably lead to an antimicrobial resistance problem. It has long been suspected that wastewater released from swine farms is a crucial aspect of the spread of antimicrobial resistance to the environment. Biogas systems are wastewater treatment systems commonly used on swine farms; however, little is known about the roles they play in the occurrence and transmission of resistant bacteria between biogas and non-biogas systems. This study collected pooled water, wastewater, and feces samples from five biogas farms and three non-biogas farms in Central Thailand. The samples were isolated to hemolytic E. coli (HEC) and non-hemolytic E. coli (NHEC) to test the drug resistance by using VITEK® 2 Compact (BioMérieux, USA) and detect resistant genes by using the polymerase chain reaction (PCR) technique to correlate the determined phenotypic and genotypic patterns. The results demonstrated that enumeration levels of E. coli ranged from 20.1 to 70.4 (MPN/100 ml), 10 to 10 (cfu/ml), and 10 to 10 (cfu/g), while they were 0-148.7 (MPN/100 ml), 10 to 10 (cfu/ml) and 10 to 10 (cfu/g) for water, wastewater and manure from biogas and non-biogas swine farms, respectively. The amount of E. coli in the sow feces samples was higher than the samples of nursery piglets on biogas farms at a 0.05 significant level (p < 0.05). The antimicrobial resistance indicated the relevant resistance characteristics of E. coli: the highest antimicrobial resistance was for ampicillin (AMP), followed by amoxicillin (AMX), tetracyclines (TET), chloramphenicol (C), and piperacillin (PIP), respectively. Multidrug resistance (MDR) of E. coli was 15 drugs: AMP-AMX-AMC-PIP-CEX-CEV-CPD-XNL-GM-IMP-SXT-C-TE (11.9%) and AMP-AMX-AMC-PIP-CEX-CEV-CPD-XNL-GM-IMP-SXT-C-ENR-MBR-TE (18.55%), which were the most commonly found in biogas and non-biogas swine farms, respectively. The bla, tetA, sul2, and sul3 were dominantly resistant genes isolated from the water from both types of farm; while, bla, aadA1, tetA, dfrA12, sul2, sul3, and cmlA were isolated from feces. The amount of E. coli in the final effluent from biogas swine farms was higher than the non-biogas swine farms; however, it was not significantly different at (p > 0.05). Furthermore, the findings of study found that genotypic characteristic of HEC showed similarity 100%. Thus, it was concluded that the levels of E. coli were accelerated in biogas wastewater treatment systems, and isolated E. coli demonstrated multidrug resistance. Even though E. coli was found in different locations, it showed relevant resistance characteristics. Therefore, regular monitoring of antimicrobial resistance on livestock farms is necessary for efficient management and drug uses on farms.