Microbiology Laboratory

I was posted to microbiology laboratory for 2 week. Read and understood the laboratory safety manual and general protocol.

Was sent to the processing bench for the first 2 days. I learnt how to clocked in the various samples that was sent to the microbiology laboratory to verify the time that the samples were received. I was taught how to differentiate the various nature of the specimen so as to allocate them to the various benches for tests. The blood bottles was first incubated in an incubator for to check for sign of mircoorganism growing in the bottle. The type of test is denoted by the colour of the cap. Blue represent aerobic culture, golden represent anaerobic culture while red represent fungal culture. Urine specimen regardless of catheter or mid-stream urine was first culture in a blood and macConkey spilt-well agar. It is noted that streaking must be done on blood agar first before macConkey so as to avoid carry-over effect from macConkey agar to blood. MacConkey agar will encourage growth of gram-negative bacteria. Specimen that were not urine or blood were labeled as miscellenous item. All swab of superficial wound will be culture on blood and macConkey agar, while addition culture on PEA plate to be carried out if swab of site is below waist. PEA agar encourage growth of gram-positive bacteria. Type of culture to be carried out depend on appearance of stool. If it is a normal stool, culture will be carried out on macConeky, Salmonella-shigella agar and selenite broth. Addition culture will be carried out on watery stool. They are TSA agar with 5% sheep agar, thiosulphate Citrate Bile Salt sucrose agar and alkanline peptone water. These agar will help to detect the presence of Vibro which are usually associated with watery stool.

Supervisor then allocated me to the microscopy bench on the third day to observe the various procedure. I was taught to differentiate the appearance for the respiratory specimen. It may be mucoid, plurelent, watery or blood-stain. Depending on what type of stain the doctor request, the medical techologist will then process the request. Usually gram staining is carried out. Slide is stained with crystal violet for one minute and then washed. Slide is then stained with iodine for 2 minutes follow by washing and rapid decolourising by 100% acetone. Slide is lastly counter-stained with safranin for 1 mintues and then read under microscope. I was taught to identify blastoconidia and mycellium under the microscope. If acid-fast stain is request, it must be read under an immuno-fluroscent microscope in the dark room to identify mycobacellium.

I was then allocated to the urine bench on the fourth and fifth day to observe interpretration of the urine culture that was cultured on the blood and macConkey spilt-well plate. Colour and appearance of the culture will be noted to aid in the interpretattion. Usuaaly, if there is green colour on the blood agar culture, it implies culture is alpha hemolytic, and if there is pink colour culture on the macConkey agair, it implies culture is a lactose fermenter. Addition information such as whther culure is in swamps will aids in the identifcation.If culture contain less than 10^5 and is not a pure culture, no further testing will be carried out as this is usually due to contamination. Addition tests that are carried out may be radID one procedure, staph grouping kit, indole test etc.

Yeo Ching Wei
0503288C
TG02