RESUMEN
Melioidosis is a tropical disease caused by the bacterium Burkholderia pseudomallei. Outbreaks are uncommon and can generally be attributed to a single point source and strain. We used whole-genome sequencing to analyse B. pseudomallei isolates collected from an historical 2-year long case cluster that occurred in a remote northern Australian indigenous island community, where infections were previously linked to a contaminated communal water supply. We analysed the genome-wide relatedness of the two most common multilocus sequence types (STs) involved in the outbreak, STs 125 and 126. This analysis showed that although these STs were closely related on a whole-genome level, they demonstrated evidence of multiple recombination events that were unlikely to have occurred over the timeframe of the outbreak. Based on epidemiological and genetic data, we also identified two additional patients not previously associated with this outbreak. Our results confirm the previous hypothesis that a single unchlorinated water source harbouring multiple B. pseudomallei strains was linked to the outbreak, and that increased melioidosis risk in this community was associated with Piper methysticum root (kava) consumption.
Asunto(s)
Burkholderia pseudomallei/genética , Genoma Bacteriano , Melioidosis/microbiología , Australia/epidemiología , Brotes de Enfermedades , Humanos , Kava/microbiología , Melioidosis/epidemiología , Tipificación de Secuencias MultilocusRESUMEN
AIMS: Kava beverages are highly perishable even under refrigerated conditions. This study aimed to investigate the bacterial community dynamics in kava beverages during refrigeration. METHODS AND RESULTS: Four freshly made kava beverages were obtained from kava bars and stored at 4°C. On days 0, 3 and 6, the aerobic plate count (APC), lactic acid bacteria (LAB) count and yeast and mould count (YMC) of the samples were determined. Meanwhile, bacterial DNA was extracted from each sample and subjected to the polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). Moreover, species-specific PCR assays were employed to identify predominant Pseudomonas spp. involved in kava spoilage. Over the storage period, the APC, LAB count and YMC of the four kava beverages all increased, whereas their pH values decreased. The DGGE profile revealed diverse bacterial populations in the samples. LAB, such as Weissella soli, Lactobacillus spp. and Lactococcus lactis, were found in the kava beverages. Species-specific PCR assays detected Pseudomonas putida and Pseudomonas fluorescens in the samples; Ps. fluorescens became dominant during refrigeration. CONCLUSIONS: LAB and Pseudomonas may play a significant role in the spoilage of kava beverages. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides important information that may be used to extend the shelf life of kava beverages.
Asunto(s)
Bacterias/clasificación , Bacterias/aislamiento & purificación , Microbiología de Alimentos/métodos , Kava/microbiología , Bacterias/genética , Bebidas/microbiología , Recuento de Colonia Microbiana , ADN Bacteriano/análisis , ADN Bacteriano/genética , Electroforesis en Gel de Gradiente Desnaturalizante/métodos , Lactobacillus/genética , Lactobacillus/aislamiento & purificación , Reacción en Cadena de la Polimerasa/métodos , Refrigeración , Weissella/genética , Weissella/aislamiento & purificaciónRESUMEN
AIM: Fresh kava beverages have a limited shelf life under refrigerated conditions. The objective of this study was to isolate and identify bacteria in aqueous extracts of kava rhizome. METHODS AND RESULTS: The internal part of kava rhizome was used to minimize soil contamination. Three kava extracts were prepared, serially diluted and plated on nutrient agar. Isolated colonies were identified by sequencing polymerase chain reaction amplicons targeting the eubacterial 16S rDNA and the tuf gene of Staphylococcus. Seventy-five bacterial isolates belonged to 16 genera. Bacillus, Cellulomonas, Enterococcus, Pectobacterium and Staphylococcus were identified in all kava extracts. CONCLUSIONS: Kava rhizome contains large amounts of starch and fibre, which justify the presence of polysaccharide-degrading bacteria in the extracts. Bacillus cereus group and Staphylococcus species may produce toxins and cause foodborne illness. SIGNIFICANCE AND IMPACT OF THE STUDY: The results of this study provide fundamental information that may be used to enhance the microbial quality and safety of kava beverages.
Asunto(s)
Bacterias/aislamiento & purificación , Microbiología de Alimentos , Kava/microbiología , Bacterias/clasificación , Bacterias/genética , Bebidas/microbiología , ADN Bacteriano/genética , Datos de Secuencia Molecular , Reacción en Cadena de la Polimerasa/métodos , ARN Ribosómico 16S/genética , Rizoma/microbiología , Análisis de Secuencia de ADNRESUMEN
Preparative scale fermentation of (6S)-dihydrokawain (1) with Rhizopus arrhizus (ATCC 11145) gave 3'-hydroxydihydrokawain (2) and (8S)-hydroxydihydrokawain (3). Structure elucidation of the metabolites was based on spectroscopic data. The C-8 absolute configuration of (3) was assessed via its Mosher's esters.