No abstract

Despite great advancement in genetic typing, phenotyping is still an indispensable tool for categorization of bacteria. certain amino acids may be essential for bacterial survival, growth, pathogenicity or toxin production, which prompts the idea that the intrinsic ability to utilize single amino acid under live-or-die situation could be a basis for differentiation of bacteria species. In this study, we determined the single amino acid consumption profiles of 7 bacterial species, and demonstrated that most bacteria have species-specific pattern of amino acid consumption. We also discovered that bacterial strains from different hosts, toxigenicity, and antibiotic-resistance presented distinct preference for certain amino acids. Taken altogether, the amino acid consumption profiles showed potential to be a novel tool complementary to study not only bacterial categorization but also biochemical characteristics of the bacteria such that its phenotyping can be used to uncover strategies for nutritional, pharmaceutical, taxonomic, and evolutionary aspects of bacterial researches. Bacterial identification is crucial in a wide variety of applications including disease diagnosis, food safety, and environmental monitoring. In general, two distinct methods are used for bacterial identification; genotyping and the phenotyping. Genotypic methods such as DNA sequencing, refer to discrimination of bacterial strains based on their genetic content 1. On the other hand, phenotypic traits are based on the characteristics expressed by bacterial strains, which comprise morphological, physiological, and biochemical features. For example, Analytical Profile Index (API) and Biolog system are commonly used phenotypic methods which rely on the utilization and metabolism of simple chemical compounds 2,3. Although genotyping has recently become mainstream for bacterial strain typing, phenotypic methods still play an important role in many cases and provide crucial insights into bacterial strains. For instance, about two-thirds of genes from bacterial to mammalian cells have been shown to possess biochemical function, but only a small fraction of these genes are known to be associated with phenotypes 4,5. Therefore, more phenotypic information is desirable in understanding the roles of those inexplicable genes 6,7 and to discover their resultant behaviors in relations to pathology, epidemiology, and ecology. Amino acids (AAs) are critical substances for nitrogen and carbon metabolism in bacteria. Different bacteria may have different abilities to utilize AAs depending on their genetic and adopted differences as well as the nutritional availability from the environment, rendering significant variations in their phenotypes even when they belong to the same species. So far, bacteria utilize AAs in a species-dependent manner have been reported elsewhere. For example, Escherichia coli can use serine (Ser), aspartate (Asp), cysteine (Cys), glycine (Gly), glutamate (Glu), and alanine (Ala) as the sole carbon and nitrogen sources during aerobic grow...

Prudent antimicrobial use requires knowledge of pharmacokinetics (PK) in a specific fish species which in turn depends on water temperature and salinity. Although the influence of each individual factor is known, the combined effect is less clear. The objective of the current study was to investigate the effect of temperature and salinity concurrently on the PK of florfenicol (FF) in Nile tilapia reared in brackish water. Twenty-eight fish were divided into four groups and kept at one of two temperatures (24 vs. 32°C) and two salinity levels (5 vs. 15 ppt). The FF was administered at a single dose of 15 mg/kg body weight via oral gavage. The serum concentrations were analyzed by HPLC method and the PK parameters were analyzed by a 2-compartmental model. The result revealed that at 32°C, the elimination half-lives (t1/2β), time to reach the peak concentration (Tmax), area under the serum concentration-time curve (AUC), and mean residence time (MRT) were significantly decreased, while the clearance relative to bioavailability (CL/F) significantly increased compared to those at 24°C. The extents of these PK changes were similar at the two salinity levels. On the contrary, increasing the salinity from 5 to 15 ppt at a given temperature level produced no significant change in the PK behavior. Our finding indicated that only water temperature, but not salinity, is the major determinant factor governing the FF fate in the fish body.

Toxoplasma gondii and Neospora caninum are intracellular protozoan parasites that cause reproductive disorders in ruminants and humans. Information on the risk factors of T. gondii and N. caninum infections in goats is very limited in Taiwan. The aim of the study was to investigate the epidemiology and identify the risk factors of these two infections in goats. A total of 630 caprine sera were collected from 42 dairy goat farms and the owners were interviewed by a structured questionnaire. The apparent seroprevalences of T. gondii in farm-and individual-levels were respectively 88.1% and 32.22%, while those of N. caninum were 19.05% and 2.54%, respectively. Toxoplasma gondii B1 gene was identified in 7 feed samples and 8 from the water samples whereas N. caninum was not found. Wooden flooring was the main risk factor for T. gondii infection while the frequency of visits by staff to other farms and the breed of goat were risk factors for N. caninum. The improvement of flooring materials or thorough cleaning, periodic disinfection and maintenance of dryness on the floor are highly recommended for the prevention of T. gondii infection in farmed goats. In addition, unnecessary visits to other farms should be limited to prevent the spread of N. caninum. These factors should be highlighted for the prevention of T. gondii and N. caninum in goats, particularly when raised in intensive housing system with flooring on height.