Abstract
Background:
Although seafood is a major source of high-quality nutrients, it may also harbor pathogenic and antimicrobial-resistant bacteria, posing risks to food safety and public health. Escherichia coli and Klebsiella spp. are important pathogens associated with seafood contamination and antimicrobial resistance.

Aim:
To determine the prevalence, antimicrobial susceptibility, and resistance patterns of Escherichia coli and Klebsiella spp. isolated from seafood sold in markets in Hanoi, Vietnam.

Methods:
A total of 120 seafood samples (squid, fish, shrimp, and oyster) were collected from retail markets in Hanoi and immediately transported to the laboratory for analysis. MALDI-TOF mass spectrometry and biochemical tests were used to isolate and identify E. coli and Klebsiella spp. The antimicrobial susceptibility of bacterial isolates was assessed using the disc diffusion method.

Results:
The prevalence of E. coli and Klebsiella spp. in seafood was 35/120 (29.2%) and 24/120 (20.0%), respectively, with oysters showing significantly higher contamination rates than squid, fish, and shrimp. Among the 35 E. coli isolates, the highest resistance was observed against ceftazidime (71.4%), followed by cefotaxime (57.2%), sulfamethoxazole/trimethoprim (45.7%), ampicillin (37.2%), and tetracycline (37.2%). In contrast, 24 Klebsiella spp. isolates showed the highest resistance rates to sulfamethoxazole/trimethoprim (95.8%), ampicillin (91.7%), and ceftazidime (50.0%). Multidrug resistance was observed in 9 E. coli and 3 Klebsiella spp. isolates.

Conclusion:
The high prevalence and antimicrobial resistance rates of E. coli and Klebsiella spp. isolated from seafood sold in the study area highlight the need for improved surveillance, stricter control of antimicrobial use in aquaculture, and enhanced food safety measures.

Key words: Antimicrobial resistance; E. coli; Klebsiella spp.; Prevalence; Seafood; Hanoi