Volume 49 Number 3

Alteration of antimicrobial phenotypic resistance of E. coli in municipal wastewater treatment process and receiving canal water in Bangkok, Thailand

Wilai Chiemchaisri^a,*, Chart Chiemchaisri^a, Nopparat Patchanee^b, Toru Watanabe^c

 
ABSTRACT:     The phenotypic prevalence of antibiotic-resistant E. coli (ARE) in the sewage of Bangkok City, Thailand, during the conventional activated sludge (CAS) process was evaluated. The relationship of ARE in the CAS effluent/receiving water was investigated. The CAS E. coli isolates were tested against 20/21 antibiotics in 6 classes: 4 aminoglycosides, A; 3 tetracyclines, T; 1 chloramphenicol, C; 11 quinolones, Q; 1 sulfonamide, S; and 1 betalactam, B. The results showed that the sewage contained 84% ARE, of which 28% was single drug-resistance and 56% was multidrug-resistant E. coli (MRE). Poor removals of ARE/MRE were found in the CAS. Inversely, a more susceptive E. coli population to all tested antibiotics was detected in the CAS effluent (24%). When MRE was classified into low (L)-, medium (M)-, and high (H)-levels based on number of resistant antibiotics, it showed that the effluent L-MRE (2 to 5 antibiotics) was highest (46%) compared to the others (29?38%), while H-MRE (11 to 16 antibiotics) was relatively dominant in the dewatered sludge (24%). Additionally, Q-S-T was the most phenotypic resistant pattern in sludge, while Q-S was highly frequent in effluent. ARE in receiving water showed a high correlation to MRE of CAS effluent along receiving water due to high contamination of coliforms and E. coli.

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* Corresponding author, E-mail: fengwlc@ku.ac.th

Received 12 Sep 2023, Accepted 9 May 2024