Medical microbiology Assignment PDF
Added on 2021-04-21
6 Pages1494 Words46 Views
Running head: MEDICAL MICROBIOLOGYMedical MicrobiologyName of student:Name of university:Author note:
1MEDICAL MICROBIOLOGYThe essay analyzes the case of RP, a 20 years old male patient with complaints of waterydiarrhea, abdominal pains and cramps. The review of the patient’s detail and his travel historyrevealed infective gastroenteritis. The main purpose of the essay is to evaluate the TBS agarresults to find out the causes of infection in patients. The procedures used for diagnostics testingof cholera and implications of the test results have been provided. The isolate in the present case is Vibrio cholerae, which is a Gram-negative, facultativebacterium responsible for causing the disease cholera in humans. These are asporogenous,motile, curved or straight rods. When humans ingest the microorganism, it causes severe diarrheaaccompanied with vomiting and nausea. The primary connection between the microorganismsand human is through water where there is an absence of proper water purification system. Thegrowth of the organism can be noted in TCBS agar, and the organism gives positive results forOxidase test and String test. Further, agglutination is observed with serogroup O1 antisera(Gillespie 2014). Thiosulfate-Citrate-Bile Salts-Sucrose (TCBS) Agar is widely used for the selective isolation of Vibrio cholera from different specimens. The different components are sucrose, dipeptone, sodium citrate, sodium thiosulphate, sodium chloride, yeast extract, ox bile, sodium cholate, ferric citrate, bromothymol blue, thymol blue and agar. Sodium citrate and thiosulphate inhibit growth of Enterobacteria. Ox bile and sodium cholate is responsible for inhibition of gram-positive bacteria. Bromthymol BlueandThymol Blueare pHindicators. Fermentation of sucrose makes bromothymol blue turns yellow. thiosulfateacts as a sulfur source. Yeast extractandpeptoneare sources of nitrogen, vitamins, and amino acids. Sodium chlorideprovidesoptimum growth and metabolic activity of halophilicVibriospp.Agaracts as asolidifying agent (Murray, Rosenthal and Pfaller 2015).
2MEDICAL MICROBIOLOGYIf the results of the string test for identification of V. cholerae are positive, it is to beunderstood that the cells of the bacteria have been lysed due to sodium deoxycholate orSodiumtaurocholate and the DNA has been released from the cells, leading to a viscous mixture. The testis done by placing a drop of 0.5% aqueous solution of sodium deoxycholate on the slide mixing asmall bacterial growth culture from the MacConkey agar into the drop. A mucoid “string” isnoticed when one draws the inoculation loop away from the suspension if positive result isachieved. In case of negative result, there is no appearance of string (Ford 2014).Serogroup O1 organisms are the causal agents of cholera outbreaks. The serogroupantisera is the agent that can be subdivide strains of Vibrio cholerae into various subtypes likeOgawa, Inaba and Hikojama. The serogroup antisera test is based on the principle ofagglutination. Serogroup O1 antisera are set of antisera, which is absorbed with different strainsof Vibrio cholera. The main procedure surrounding the test includes taking V. cholerae strainsfrom broth cultures after confirming the organism by their morphological features andemulsifying it with Vibrio cholerae antiserum. Next, the culture plates are observed for antigen-antibody ineterctions. This test is interpreted by detecting agglutination process in the sample. Apositive interaction is indicated by signs of macroscopic agglutination, whereas a negativeinteraction is denoted by absence of agglutination. Macroscopic agglutination also suggest thatone or more antigen of the V. cholera are specified by the antiserum (Baranova, Levinson andMantis 2018). The isolate being serogroup O1 positive is identified when agglutinations are observedwith serogroup O1 antisera. In case of RP, serogroup O1 positive result was found thusconfirming that one or more antigens were present in Vibrio cholera strain and serotype O1 isresponsible for causing diarrhea in patient. These findings will have implications in deciding the
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