Study of bacterial loading in macrophage cells of hybrid catfish

Hybrid catfish (Clarias macrocephalus x Clarias gariepinus) farming has developed very successfully in Thailand over the last 10 years. Farmers, however, are still encountering disease problems and, as a result, face economic losses. Some disease problems are associated with inadequate farm management practices. This study was carried out to investigate the presence of bacteria in macrophage cells isolated from hybrid catfish cultured in different environmental conditions. Results from farm investigations showed that the percentage of macrophages containing intracellular bacteria was related to water quality parameters. Experimental trials were conducted using high stocking density as stressor and bath challenge with pathogenic Aeromonas hydrophila. The results showed that fish kept in high density and bath challenged with bacteria had higher percentage of macrophages containing bacteria than those kept under normal conditions. The presence of bacterial loading in macrophage cells is, therefore, considered to be an indication of the health of the fish

Intra- and interlaboratory performance of antibiotic disk-diffusion-susceptibility testing of bacterial control strains of relevance for monitoring aquaculture environments

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A simple device for sampling pond sediment

The sediment and water inter-phase layer in aquaculture ponds is a dynamic zone that plays a crucial role in maintaining the ecological balance of the pond system. An accurate sediment profile of the soft-watery layer that includes several important parameters can only be determined by using an adequate sampling technique. Because most of the commercially available grabs and soil corers currently used do not fulfill these requirements, a new, simple device for sediment sampling was designed in the framework of the European Union (EU)-funded ASIARESIST project. The sampler was used to collect samples from the upper 5 to 10 cm soil layer for bacteriological analysis from aquaculture ponds in Malaysia, Thailand and Vietnam. The sampler consisted of a three-piece PVC pipe that could be sterilized and had a total length of 230 cm. Each section was threaded at the end except for the top of the first and last section that tapered into a sharp point at an angle of 458. When dismantled into sections, the sampler was convenient to transport and to reassemble at the site of sampling. The sediment sampler proved to be effective in obtaining intact profiles of bottom sediment, including soft sediments, was user-friendly and could be easily constructed at low cos

Intra- and interlaboratory performance of antibiotic disk-diffusion-susceptibility testing of bacterial control strains of relevance for monitoring aquaculture environments

none13In the course of an international research project on hazard analysis of antimicrobial resistance in SE Asian aquaculture environments, 2 European Union and 3 SE Asian laboratories attempted to harmonize a procedure for antimicrobial agent susceptibility testing based on disk diffusion (DD). For this purpose, a selected panel of 10 bacterial control strains of relevance for monitoring warm-water aquaculture environments was sent by the central laboratory to the other participating laboratories. In each laboratory, 10 independently replicated DD determinations of each control strain to 6 antibiotics were performed using Iso-Sensitest Agar (ISA) according to a standard operating procedure (SOP); in total, this study thus yielded 300 data sets for all 5 laboratories. At the end of the study, strain authenticity of subcultures of the control strains used by the respective participating laboratories was verified by the central laboratory. Based on the arithmetic mean of 10 inhibition-zone diameter measurements and standard deviation (SD), intralaboratory SD variations ranged from 0 to 2 mm when 79% of the recorded data sets were considered. In 8% of the data sets, the SD value exceeded 4 mm, which in most cases could be attributed to the fact that the data points for a given strain–disk combination were not normally distributed in one of the laboratories. At the interlaboratory level, 81% of the SD values based on global averaging of 50 data points per strain–disk combination were situated in the 0 to 5 mm range. Comparison with a minimal data set from literature of DD testing performed with Mueller-Hinton (MH) medium indicated that the use of either ISA or MH medium in DD testing has a limited impact on the method’s precision among different laboratories. In conclusion, the current study has provided a validated SOP to promote the coordination and harmonization of DD-susceptibility methodologies for aquaculture-associated organisms at an international level. As one of the main action items for the future, new interpretive breakpoints should be specifically designed and validated for aquaculture drugs and organismsG. HUYS ; M. CNOCKAERT ; K. BARTIE ; D. T. H. OANH ; N.T. PHUONG ; T. SOMSIRI ; S. CHINABUT ; F. YUSOFF ; M. SHARIFF ; M. GIACOMINI; S. BERTONE ; J. SWINGS ; A. TEALEG., Huys; M., Cnockaert; K., Bartie; D. T. H., Oanh; N. T., Phuong; T., Somsiri; S., Chinabut; F., Yusoff; M., Shariff; Giacomini, Mauro; S., Bertone; J., Swings; A., Teal

Effect of season and temperature on mortality in amphibians due to chytridiomycosis

To investigate the distribution and incidence of chytridiomycosis in eastern Australian frogs and to examine the effects of temperature on this disease. A pathological survey and a transmission experiment were conducted. Diagnostic pathology examinations were performed on free‐living and captive, ill and dead amphibians collected opportunistically from eastern Australia between October 1993 and December 2000. We conducted a transmission experiment in the laboratory to investigate the effects of temperature: eight great barred frogs () exposed to zoospores of and six unexposed frogs were housed individually in each of three rooms held at 17°C, 23°C and 27°C. Chytridiomycosis was the cause of death or morbidity for 133 (55.2%) of 241 free‐living amphibians and for 66 (58.4%) of 113 captive amphibians. This disease occurred in 34 amphibian species, was widespread around the eastern seaboard of Australia and affected amphibians in a variety of habitats at high and low altitudes on or between the Great Dividing Range and the coast. The incidence of chytridiomycosis was higher in winter, with 53% of wild frogs from Queensland and New South Wales dying in July and August. Other diseases were much less common and were detected mostly in spring and summer. In experimental infections, lower temperatures enhanced the pathogenicity of in . All 16 frogs exposed to at 17°C and 23°C died, whereas 4 of 8 frogs exposed at 27°C survived. However, the time until death for the frogs that died at 27°C was shorter than at the lower temperatures. Infections in survivors were eliminated by 98 days. Chytridiomycosis is a major cause of mortality in free‐living and captive amphibians in Australia and mortality rate increases at lower temperatures