Prevalence of antibiotic-resistant Salmonella in kratom: Three-year monitoring study

Objectives

Kratom, powder from Mitragyna speciosa leaves, is a popular psychoactive drug. It poses a health risk to consumers not only because of its narcotic and stimulating effects, but also because its quality is not controlled by the same laws as other food and pharmaceutical products. Due to the absence of mandatory quality control, kratom carries an increased risk of pathogenic bacteria contamination. Based on previous studies, the most relevant of these from a public health perspective are bacteria of the genus Salmonella, particularly serotypes that may cause severe gastrointestinal illness and exhibit resistance to antimicrobial agents. To assess the scale of the problem, we monitored the occurrence of Salmonella in commercially available kratom in the Czech Republic and determined its antimicrobial resistance.

Study design

Original microbiological research (long-term monitoring).

Methods

In 2022–2024, we tested 96 different kratom samples, from which Salmonella was isolated by the cultivation method according to EN ISO 6579. Series of biochemical and agglutination tests were used to determine the species, subspecies and serotypes. The disk diffusion method was used for testing susceptibility to 16 antimicrobial agents, and the results were interpreted using EUCAST and CLSI criteria.

Results

Salmonella was isolated from 16 out of all 96 tested samples. Biochemical and agglutination tests revealed that Salmonella enterica subsp. enterica was the most prevalent species and subspecies (14 samples), with some of the identified serotypes being relatively rare. Regarding the susceptibility to antimicrobial agents, out of all isolates 15 were resistant to at least one tested antimicrobial agent, and three isolates were classified as multidrug resistant.

Conclusions

Based on our analysis, the rate of Salmonella contamination did not differ statistically over the three years of study. Our results highlight the need for the continuous monitoring of Salmonella in kratom and provide a basis for the implementation of legal restrictions of its sale.