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Abstract: Streptococcosis is an important bacterial disease in Nile tilapia causing severe economic losses to tilapia aquaculture worldwide. The effects of water quality (low‐ [LS] and high‐level [HS] soiling, to mimic clean or dirty surface conditions and temperatures) and disinfectant application (diluted concentrations and exposure time) were characterized on the inactivation of Streptococcus agalactiae isolated from diseased tilapia. Five isolates were tested against three commercial disinfectant products with the main ingredients being povidone iodine (Anidine 100™; AD), benzalkonium chloride (Better BKC 80%™; BKC 80), and a mixture of quaternary ammonium compounds and glutaraldehyde (Chloraldehyde™; CR). CR demonstrated highest efficacy to S. agalactiae inactivation, followed by BKC 80 and AD, respectively. Higher‐level soiling, low temperature, diluted concentrations and short exposure time all decreased the disinfectant efficacy. CR and BKC 80 provided more than 5‐log inactivation at 1‐min exposure at 20°C under HS conditions, and also with ten‐fold‐diluted concentrations at 60‐min exposure time at 30°C. However, AD required 10‐min exposure to effectively remove bacteria under LS conditions at 30°C. The results could facilitate aquaculture management planning that leads to operating cost reductions and improvements in biosecurity. [ABSTRACT FROM AUTHOR]

Aims: To evaluate the use of nonlocal, already-available strains of phages to indicate faecal contamination in Thailand waters. Methods and Results: Phages of Bacteroides fragilis strains ATCC 700786 (RYC2056PH) and ATCC 51477 (HSP40PH) were measured in 71 human and animal wastewater samples in Thailand using a double-layer agar assay. Bacteriophage RYC2056PH was detected at concentrations comparable to representative human and animal wastewater samples from European and Mediterranean countries, with 61·7 and 33·3% above the threshold value of 100 PFU 100 ml-1 in wastewater samples of human and animal origins, respectively. On the other hand, HSP40PH was detected at low concentrations in both human- and animal-polluted wastewaters. Moreover, RYC2056PH was found in 12 canal waters with human-influenced pollution and was not detected in 6 nonpolluted river waters being tested in this study. Conclusions: The presence of RYC2056PH could indicate nonsource-specific faecal contamination in Thailand. Significance and Impact of the Study: This study provided the first evidence that bacteriophages of the European-isolated B. fragilis strain RYC2056 could be used as nonsource-specific faecal indicators in the Southeast Asian region. The results of this study support the worldwide use of Bacteroides phages as faecal indicators. [ABSTRACT FROM AUTHOR]

This study investigated the effect of exposure times on the response of ammonia oxidizing mixed culture (AOMC) to phenolic compounds while having the future goal to develop a biosensor using AOMC for toxicity monitoring. AOMC was used instead of purified nitrifying culture because of the ease of culture development. The oxygen utilization rate (OUR) was measured during three exposure periods; 0-15, 25-40 and 50-65 min. It was found that phenolic compounds have a strong inhibitory effect on AOMC. The percentage of OUR reduction increased with higher concentrations and the extended exposure times improved the toxic response of AOMC, especially to the lower concentrations (0.25, 0.50, 1.0 mg/L). Further, AOMC detoxifying mechanisms might result in the reduction of toxic response when the longest exposure time was applied. However, at the higher concentrations (2.5 and 5.0 mg/L), the extended exposure times did not have a critical effect on the response pattern of AOMC, especially for phenol and mono-chlorinated phenols. It was illustrated that AOMC is very sensitive to phenolic compounds and its sensitivity is high enough for the detection of phenolic compounds at the level of effluent standard in Thailand and Japan with a rapid response time of 15 min. To improve the sensitivity of AOMC to low phenolic compound concentrations, an extended exposure time of 25-40 min would be recommended. [ABSTRACT FROM AUTHOR]