Medical microbiology Assignment Example | Topics and Well Written Essays - 750 words

Medical microbiology - Assignment Example Some of them are insufficient media, bactericidal activity present in blood, amount of blood used for culturing, antibiotics occurrence, blood collection time. Most of bacterial cells of Salmonella serovar Typhi resides intracellulary in the patient’s blood. There is a need of reliable, rapid and sensitive methods for clinical detection of Salmonella serovar Typhi. Serological tests are available but its sensitivity and specificity is very low. The blood culture sensitivity is highest during the first week of illness but it then gradually decreases with advancement of illness. 45- 70% patients of typhoid fever can be identified through blood culturing. It depends upon the blood sample amount, bacteraemic level of Salmonella, culture medium type, length of incubation. Also the Salmonella bacteria presence in patient’s blood is very low, often below detection by blood culturing and even below detection by PCR. Difficulties become more due to limited amount of patient blood sample. Ox bile tryptone soy broth was used for blood culture; it allows blood cell lysis completely, which causes the release of intracellular bacteria. It does not inhibit the growth of Salmonella Typhi. From research it was found out that bacterial growth can be increased if blood culture media contains lyzing agents for blood cells. By performing various tests it was found out that 2.4% ox bile presence in blood culture will lyse blood cells within 1.5 hours so that the bacteria present intracellulary came out. Salmonella bacteria when kept in tryptone soya broth containing 2.4% ox bile for 3 hours will increase the amount of bacteria from 0.75 CFU per milliliter of blood. This level can be easily detectible by using regular PCR method. This blood culture PCR assay processing time is lesser than 8 hours as compared to conventional blood culture which may take 2 -5 days. Salmonella serovars patient’s blood or serum is also bactericidal