Saran's Learn Microbiology

EVALUATION OF DISINFECTANTS REQUIRED CONCENTRATIONS AND TIMES FOR CHEMICAL DESTRUCTION OF MICROORGANISMS Disinfectants Microorganisms Disinfectant concentration Time Chlorine Mycobacterium tuberculosis 50 ppm 50 sec Entamoeba cyst 0.1 ppm 150 min Hepatitis A Virus 3 ppm 30 min Ethyl alcohol Staphylococcus aureus 70 % 10 min Escherichia coli 70 % 2 min Poliovirus 70 % 10 min Hydrogen peroxide Staphylococcus aureus 3 % 12.5 sec Neisseria gonorrhoea 3 % 0.3 sec Herpes simplex virus 3 % 12.8 sec Quaternary Ammonium compounds Staphylococcus aureus 450 ppm 10 min Salmonella typhi 300 ppm

TRANSPORT OF CLINICAL SPECIMENS Specimens to be sent to other laboratories require special attention for safe packing of the material. For hand-carried transportation over a short distance, the specimen should be placed upright in appropriate racks. For long distance transportation, it should be placed in three containers. a)   A primary container which has the specimen and is leak proof with a screw-cap. b)   A secondary container which is durable, waterproof and made of metal or plastic with a screw-cap. It should have enough absorptive material to absorb the contents of the primary container should the latter break or leak. On its outside, the details of the specimen should be pasted. c)    A tertiary container is usually made of wood or cardbox. It should be capable of withstanding the shocks and trauma of transportation. Dry ice can be kept between this and the secondary container along with sufficient absorbents and provision for the escape of carbon-di-oxide to prevent a p

COLLECTION OF CLINICAL SPECIMENS (i) BLOOD Whole blood is required for bacteriological examination. Serum separated from blood is used for Serological techniques. Skin antisepsis is extremely important at the time of collection of the sample. Tincture of iodine (1 – 2 %), Povidone iodine (10 %) and Chlorhexidine (0.5 % in 70 % Alcohol) are ideal agents. However, some individuals may be hypersensitive to iodine present in some of these. Collect blood during the early stages of disease since the number of bacteria in blood is higher in the acute and early stages of disease. Collect blood during Paroxysm (a sudden recurrence of symptoms) of fever since the number of bacteria is higher at high temperatures in patients with fever. In the absence of antibiotic administration, 99 % culture positivity can be seen with three blood cultures. Small children usually have higher number of bacteria in their blood as compared to adults and hence less quantity of blood needs to be collected from the