Microbial, steroids and heavy metals contamination and antimicrobial resistance of bacterial isolates in thai herbal products

Screening for the presence of bacteria, steroids, and heavy metals is essential for the protection of consumers of herbal medications. Samples of Thai herbal medicine (n = 59) were collected from one metropolitan region and four provinces to test for the presence of bacteria, steroids and heavy metal contamination. Total aerobic microbial and total yeast/ mold counts ranged from 0 -9x106 and 0 -20 colony-forming units (CFU)/g respectively. The range of 0 - 1,100 CFU/g represented the most likely coliform bacterial concentrations. Clostridium spp, Escherichia coli and Pseudomonas aeruginosa were detected in 19, 14 and 3 percent of the samples, respectively, whereas Salmonella spp and Staphylococcus aureus were not present. Overall, 47% of the herbal medicine samples fulfilled the standards for quality set forth by the WHO guidelines and Thai Pharmacopoeia. The percentage of samples that met the quality standards was 100, 64, 50, 50, 40, 33, and 0 percent for tea, tablets, capsules, liquids, pills, and powder forms, respectively. While all P. aeruginosa isolates were sensitive to the seven test antibiotics, 25% of E. coli isolates demonstrated multidrug resistance, namely, resistance to amoxicillin/clavulanate, ampicillin, ciprofloxacin, and trimethoprim/sulfamethoxazole. PCR-based assays revealed that all E. coli and P. aeruginosa isolates carried blaTEM but not blaSHV gene, while 25% of E. coli also contained blaCTX-M gene. An immunochromatographic assay revealed that 2% of the herbal medicine samples were positive for dexamethasone (confirmed by a reference laboratory of the Ministry of Public Health Thailand) and paracetamol and diclofenac (non-steroid anti-inflammatory drugs) were also detected. The mean +/- standard deviation (SD) (range) of cadmium and lead evaluated in 32/59 randomly selected samples using in-house methods based on AOAC International (2016) 999.10 was 0.0385 +/- 0.0247 mg/kg (0.003-0.26 4 mg/kg) and 0.140 +/- 0.009 mg/kg (0.003-0.61 7 mg/kg) respectively, within the limit of cadmium and lead standard criterion (<= 0.3 and <= 10 mg/kg respectively). The study's findings should contribute to raising the standard of Thai herbal medicine preparations.