Occurrence and molecular characteristics of antimicrobial resistance, virulence factors, and extended-spectrum β-lactamase (ESBL) producing Salmonella enterica and Escherichia coli isolated from the retail produce commodities in Bangkok, Thailand

Abstract

The incidence of antimicrobial resistance (AMR) in the environment is often overlooked and leads to serious health threats under the One Health paradigm. Infection with extended-spectrum β-lactamase (ESBL) producing bacteria in humans and animals has been widely examined, with the mode of transmission routes such as food, water, and contact with a contaminated environment. The purpose of this study was to determine the occurrence and molecular characteristics of resistant Salmonella enterica ( S. enterica) ( n = 59) and Escherichia coli ( E. coli) ( n = 392) isolated from produce commodities collected from fresh markets and supermarkets in Bangkok, Thailand. In this study, the S. enterica isolates exhibited the highest prevalence of resistance to tetracycline (11.9%) and streptomycin (8.5%), while the E. coli isolates were predominantly resistant to tetracycline (22.5%), ampicillin (21.4%), and sulfamethoxazole (11.5%). Among isolates of S. enterica (6.8%) and E. coli (15.3%) were determined as multidrug resistant (MDR). The prevalence of ESBL-producing isolates was 5.1% and 1.0% in S. enterica and E. coli, respectively. A minority of S. enterica isolates, where a single isolate exclusively carried bla _CTX-M-55 (n = 1), and another isolate harbored both bla _CTX-M-55 and bla _TEM-1 (n = 1); similarly, a minority of E. coli isolates contained bla _CTX-M-55 ( n = 2) and bla _CTX-M-15 ( n = 1). QnrS (11.9%) and bla _TEM (20.2%) were the most common resistant genes found in S. enterica and E. coli, respectively. Nine isolates resistant to ciprofloxacin contained point mutations in gyrA and parC. In addition, the odds of resistance to tetracycline among isolates of S. enterica were positively associated with the co-occurrence of ampicillin resistance and the presence of tetB ( P = 0.001), while the E. coli isolates were positively associated with ampicillin resistance, streptomycin resistance, and the presence of tetA ( P < 0.0001) in this study. In summary, these findings demonstrate that fresh vegetables and fruits, such as cucumbers and tomatoes, can serve as an important source of foodborne AMR S. enterica and E. coli in the greater Bangkok area, especially given the popularity of these fresh commodities in Thai cuisine.

Highlights

• •

  First report on semi-quantitative data on antimicrobial resistance in S. enterica and E. coli isolated from vegetables and fruits in Thailand.

• •

  S. enterica And E. coli isolates were predominantly resistant to tetracycline (12% and 23%, respectively) with the multidrug resistance phenotype (7% and 15%, respectively).

• •

  ESBL-producing S. enterica ( n = 2) and E. coli ( n = 3) harbored CTX- M-55, which is commonly found in Thailand's livestock animals, aquaculture, humans, and the environment.

• •

  The QRDR mutation in gyrA and parC is trending toward being related to the level of ciprofloxacin resistance in this study.