Investigation of Kokumi Substances and Bacteria in Thai Fermented Freshwater Fish (Pla-ra).

A 16S rRNA next-generation sequencing technique was applied to investigate the microbial diversity and liquid chromatography-tandem mass spectrometry was used to identify glutamyl peptide profiles of 10 Thai fermented freshwater fish (Pla-ra) samples. A total of 12 genera of bacteria were able to be detected, with Tetragenococcus spp., Staphylococcus spp., and Lactobacillus spp. dominating. Of the 18 glutamyl peptides analyzed, 17 were found, even though the amounts detected were lower than the taste threshold. Despite this, an increase in mouthfulness sensation, reflecting kokumi activity, was clearly identified in most of the samples, which might be because of a synergistic effect of different sub-threshold compounds present in the samples. In principle component analysis, the relationship between microorganisms and glutamyl peptide generation was observed, especially between Tetragenococcus spp. and Lentibacillus spp. and the generation of γ-Glu-Val-Gly. Correlations between microbial diversity and the generation of taste enhancers were identified in this study.

Adaptation of Campylobacter jejuni to biocides used in the food industry affects biofilm structure, adhesion strength, and cross-resistance to clinical antimicrobial compounds.

The emergence of biocide-adapted Campylobacter jejuni strains that developed into biofilms and their potential to develop clinical resistance to antimicrobial compounds was studied. C. jejuni was grown in sub-lethal concentrations of five biocides used in the food industry. C. jejuni exhibited adaptation to these biocides with increased minimum inhibitory concentrations. The 3-D structures of the biofilms produced by the biocide-adapted cells were investigated by atomic force microscopy (AFM). The results revealed marked variability in biofilm architecture, including ice-crystal-like structures. Adaptation to the biocides enhanced biofilm formation, with significant increases in biovolume, surface coverage, roughness, and the surface adhesion force of the biofilms. Adaptation to commercial biocides induced resistance to kanamycin and streptomycin. This study suggests that the inappropriate use of biocides may lead to cells being exposed to them at sub-lethal concentrations, which can result in adaptation of the pathogens to the biocides and a subsequent risk to public health.

Development of Multiple-Locus Variable-Number Tandem-Repeat Analysis for Molecular Subtyping of Campylobacter jejuni by Using Capillary Electrophoresis.

Campylobacter jejuni is a common cause of the frequently reported food-borne diseases in developed and developing nations. This study describes the development of multiple-locus variable-number tandem-repeat (VNTR) analysis (MLVA) using capillary electrophoresis as a novel typing method for microbial source tracking and epidemiological investigation of C. jejuni. Among 36 tandem repeat loci detected by the Tandem Repeat Finder program, 7 VNTR loci were selected and used for characterizing 60 isolates recovered from chicken meat samples from retail shops, samples from chicken meat processing factory, and stool samples. The discrimination ability of MLVA was compared with that of multilocus sequence typing (MLST). MLVA (diversity index of 0.97 with 31 MLVA types) provided slightly higher discrimination than MLST (diversity index of 0.95 with 25 MLST types). The overall concordance between MLVA and MLST was estimated at 63% by adjusted Rand coefficient. MLVA predicted MLST type better than MLST predicted MLVA type, as reflected by Wallace coefficient (Wallace coefficient for MLVA to MLST versus MLST to MLVA, 86% versus 51%). MLVA is a useful tool and can be used for effective monitoring of C. jejuni and investigation of epidemics caused by C. jejuni.

Microbiological evaluation of water during the 2011 flood crisis in Thailand.

In 2011, a severe flood occurred in Thailand, covering nearly half the country in water for several months. The contamination of floodwater and subsequent contamination of water for human consumption could have potentially led to a widespread health crisis. However, to date, no study has been conducted to determine the safety of the waters used for human consumption in Thailand during the severe flood. Therefore, we conducted microbiological analysis of 4 kinds of water (floodwater, river water, tap water, and filtered tap water) collected from industrial and residential areas that were damaged due to flooding. Higher net levels of bacteria were found in water with a higher turbidity. No clear trend was observed in the pH value of all 4 water samples. The level of total bacterial contamination in the water samples was estimated by real-time quantitative polymerase chain reaction (PCR). Eleven of the 12 tap water samples and all of the filtered tap water samples had a total bacterial load that exceeded the Thai water quality standards. One of the tap water samples and one of the filtered tap water samples were found to be positive for Shigella sp., although none of the floodwater samples showed detectable levels of this pathogen as determined by PCR analysis. One of the samples of floodwater was also found to be positive for Leptospira sp., but none of the tap water or filtered tap water samples were positive. Most of the tap water samples and all filtered tap water samples were found to be contaminated with Vibrio cholerae. Bacterial contamination in water samples was also analyzed by denaturing gradient gel electrophoresis (DGGE) analysis. These results revealed that several microorganisms were transferred via floodwater to different areas in the central part of Thailand and cross-contaminated between floodwater and water for human consumption.