The Thai Journal of Veterinary Medicine


The objective of this study was to isolate antimicrobial resistant bacteria from animals, humans and environment, and to characterize them based on phenotypic attributes of resistance. A total of 521 samples were collected from animals (284), humans (69) and environment (168) which resulted in isolation of 615 non-duplicate resistant isolates (to either amoxycillin-clavulanate, ceftazidime, cefixime, meropenem, or imipenem). Antimicrobial susceptibility test (AST) revealed the highest rate of resistance to cefixime (49.3%) followed by ceftazidime (45%), meropenem (38.1%), amoxicillin-clavulanate (35.3%), and imipenem (13%). Identification recorded Escherichia coli (54.6%), Klebsiella spp. (17%), Citrobacter spp. (7.5%), Enterobacter spp. (6.7%), Acinetobacter spp. (3.0%), Serratia spp. (2.8%), Proteus spp. (2.5%), Shigella spp. (2.5%), and other bacteria (3%). Production of extended-spectrum beta-lactamases (ESBLs), assessed by double disc diffusion test (DDDT) and double disc synergy test (DDST) using amoxicillin and amoxicillin-clavulanate, and ceftazidime and ceftazidime-clavulanate/ ceftazidime-tazobactam, was seen among 60 (28.6%) and 47 (22.3%) isolates, respectively. Moreover, 22.5% of the isolates expressed carbapenemase phenotype identified by imipenem-EDTA metallo-beta-lactamases (MBLs) DDDT/DDST. Out of 30 carbapenem-resistant isolates tested, five isolates (16.6%) exhibited positive MBL E-test. Moreover, positive modified Hodge test was shown by five bacterial isolates (16.6%). The present study proved the wide occurrence of multidrug-resistant (MDR) bacteria associated with animals, humans and environment. The phenotypic detection of ESBLs and carbapenemases establishes the preliminary background to more reliable genotypic identification of antimicrobial resistance, and thus aids in rapid clinical diagnosis of MDR bacterial pathogens.

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