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Biochemical Tests For Identification Of Medical Bacteria Pdf Download

Edwardsiella tarda is one of the serious fish pathogens, infecting both cultured and wild fish species. Research on edwardsiellosis has revealed that E. tarda has a broad host range and geographic distribution, and contains important virulence factors that enhance bacterial survival and pathogenesis in hosts. Although recent progress in edwardsiellosis research has enabled the development of numerous, highly effective vaccine candidates, these efforts have not been translated into a commercialized vaccine. The present review aims to provide an overview of the identification, pathology, diagnosis and virulence factors of E. tarda in fish, and describe recent strategies for developing vaccines against edwardsiellosis. The hope is that this presentation will be useful not only from the standpoint of understanding the pathogenesis of E. tarda, but also from the perspective of facilitating the development of effective vaccines.

biochemical tests for identification of medical bacteria pdf download


Several important findings suggest that intra- and/or inter-specific variability exists among E. tarda strains. E. tarda isolated from humans could be differentiated from isolates from fish by RAPD (random amplified polymorphic DNA) analysis [22], and E. tarda isolated from freshwater fish or pond sediments showed diverse and/or homogeneous characteristics in plasmid profiling, ERIC-PCR (enterobacterial repetitive intergenic consensus-polymerase chain reaction), SDS-PAGE, and RFLP (restriction fragment length polymorphism) analyses of 16S rDNA [12, 23, 24]. In addition, Western blot profiles of LPS (lipopolysaccharides) from E. tarda strains isolated from turbot and other fish revealed that only isolates from turbot were recognized by rabbit sera raised against the isolate from turbot [25]. Biochemical tests, protein profiling, LPS profiling, and RAPD analysis showed that E. tarda strains from olive flounder have highly homogeneous phenotypic and genotypic characteristics compared to isolates from Japanese eel (unpublished data).

A hospital-based cross-sectional study was conducted at SCSH from September 1, 2018, to March 30, 2019. Specimens from the ocular and periocular areas were collected from a total of 332 patients who visited the eye unit. Specimens were inoculated on blood agar, chocolate agar, MacConkey agar, and mannitol salt agar. Isolated bacteria were identified by a series of biochemical tests using the standard bacteriological method. Antimicrobial susceptibility test was performed according to the Clinical and Laboratory Standard Institute by disk diffusion method. Factors that could be associated with ocular and periocular infection were collected by using structured questionnaire. Data analysis was done using SPSS version 22.0 software package. A P value less than 0.05 was considered statistically significant.

After pure colonies were obtained, further identification was conducted using standard microbiological techniques, which include Gram stain, colony morphology, and biochemical tests. Gram-negative bacteria were identified by using several biochemical tests such as; kligler iron agar, citrate utilization test, lysine decarboxylase test, urease test, motility test, indole test, oxidase test, tributyrin, X and V factors. Gram-positive bacteria were identified using hemolytic activity on sheep blood agar, catalase test, coagulase test, bile solubility and optochin disk test [2, 13]. The quality of laboratory data was ensured by checking the expiry date of all reagents and culture media, checking the sterility of culture media before use and by conducting performance tests of culture media by using known strains such as S. aureus (ATCC 25923), E. coli (ATCC 25922) and Pseudomonas aeruginosa (ATCC 27853), H. influenzae (ATCC 49247), Neisseria meningitidis serogroup-A (ATCC 13077), S. pneumoniae (ATCC 49619) and Neisseria gonorrhea (ATCC 49226).

Identification of isolates was initiated by Gram staining. All Gram-negative isolates were further identified by motility test (by the hanging-drop method), biochemical tests, PCR amplification, and serotyping.

Among a total of 280 samples examined for bacteriological status, 19 bovine and ovine samples were positive for Salmonella by biochemical testing (but the number of true positive samples was reduced to 13 by further tests as described in Section 3.2). The isolates from bovine and ovine samples were all Gram-negative rods and motile. The samples were positive for the citrate, LDC, and H2S production tests. The urease and indole tests were negative for these isolates. The isolates were positive for the catalase test.

These four tests will, as we shall see, allow for the differentiation of the families of organisms and will guide the laboratorian to other more definitive tests for the identification of the organism.

As mentioned, the type of hemolytic reaction produced on sBAP is a major clue toward the identification of the genus. Hemolysis is the lysis of the sheep erythrocytes within the agar by bacterial toxins (hemolysins) that are produced by the different genera of Gram-positive cocci.

Once a presumptive identification has been made based on colony and microscopic morphology and the catalase reaction, additional tests can be performed to establish the genus and species of the organism. For the micrococci, susceptibility to the antimicrobial agents, bacitracin and furazolidone, as well as the modified oxidase test can be performed to distinguish this group from the staphylococci. A very important test in the categorization of the staphylococci is the coagulase test. Staphylococci are either producers of the enzyme coagulase or non-producers. The pathogen, Staphylococcus aureus, is notably coagulase-positive while most other members of the family are coagulase-negative. The streptococci and enterococci are categorized by expression of either beta, alpha, or gamma hemolysis on sBAP, depending on the genus/species. Some streptococci also possess unique cell wall carbohydrate antigens that can be identified by reactivity with specific indicator antibodies in an agglutination assay (Lancefield typing). Because of their diversity, there are a variety of biochemical tests that are used by laboratories to identify the Gram-positive cocci. Each genus lends itself to a separate tutorial.

Lastly, do not underestimate the variety of different genera in the four families of the Gram- positive cocci that can, under the right circumstances, move from relatively harmless saprophytes to disease-producing opportunists. Although the initial placement of the Gram- positive cocci into broad categories is relatively easy, further classification of some isolates can be challenging and requires a battery of tests to arrive at a definitive identification.

This novel evidence- and risk-based approach will allow optimised resource use and sustainable laboratory biosafety and biosecurity policies and practices that are relevant to their individual circumstances and priorities, enabling equitable access toclinical and public health laboratory tests and biomedical research opportunities without compromising safety.

Samples are collected from Modji leather industrial effluents and stored in the microbiology lab. After isolated bacteria from effluent using serial dilution and followed by isolated protease-producing bacteria using skim milk agar media. After studying primary and secondary screening using zonal inhibition methods to select potential protease-producing bacteria using skim milk agar media. Finally, to identify the potential bacteria using biochemical methods, bacterial biomass, protease activity, and gene sequencing (16S rRNA) method to finalize the best alkaline protease producing bacteria identified.

This study has exposed that from twenty-eight different bacterial samples isolated from leather industry effluent; further primary and secondary screening methods were selected three potential alkaline protease strains. Finally, based on its biochemical identification, biomass, and protease activity, ML12 (Bacillus cereus strains) is the best strain identified. The alkaline protease has the significant feature of housing potent bacterial species for producing protease of commercial value.

Cells of every living organism consist of a chemical substance that possesses the ability to catalyze or speed up a biochemical reaction and acts as biocatalysts, which are known as enzymes. Enzymes have better catalytic efficiency, adjustable activity, and high specificity when compared to catalysts of chemical or synthetic origin. These advantages have broadened the application of enzymes in various industries such as chemical, food, and pharmaceutical (Pires-Cabral et al. 2010; Yucel 2012; Masi et al. 2017a). This has generated a greater demand for enzyme production of high quality by cost-effective and commercial methods. Due to its importance, almost every form of life on earth possesses alkaline protease enzymes as an important factor in their physiological function. Though the protease enzymes are produced by different forms of life, due to their flexibility towards genetic manipulation, the ones that are produced by microbial sources such as bacteria and fungi are more preferred rather than human or plant protease enzymes (Masi et al. 2014; Tiwari et al. 2015).

There is a need to develop novel protease enzymes for further necessary applications of these enzymes. Moreover, enzymes produced by bacteria that are present in effluents are a greater boon to establishing the significance of converting industrial wastes to highly valuable enzymes especially like proteases (Tiwari et al. 2015; Masi 2020). The main purpose of this study is isolation, screening, and identification by morphological and biochemical aspects of potent alkaline protease-producing bacteria from leather industry effluent.

Bacteria from the leather industrial effluent site were subjected to serial dilution and then preceded for pour plating method in LB media to observe bacterial consortium. Based on colony morphology, each distinct morphological character was considered as different bacterial species and was subjected to the streak plate method for pure colony isolation and as shown in Figs. 1 and 2. A total of 28 different protease-producing bacterial isolates were isolated from the leather industry effluent sample. The isolates were sub-cultured and maintained in LB media for future tests.


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