practical exercises

Illustrations of instruements used in microbiology

  • AutoclaveEmploys moist heat for sterilization. Typical usage involves exposing articles at 121°C for 15 minutes at 15 pounds per square inch. Culture media, linen, dressing and certain rubber materials can be sterilized.
  • Arnold steamerEmploys moist heat at 100°C. Articles are exposed to steam for a duration of 20 minutes for three consecutive days (tyndallization) or for a duration of 90 minutes (free steaming). Media such as selenite broth, gelatin and sugar containing media are sterilized.
  • Hot air ovenEmploys dry heat for sterilization. Typical usage involves heating articles at 160°C for one hour. Glasswares, metal instruments, oils, grease, powders are sterilized.
  • InspissatorEmploys moist heat below 100°C for sterilization of serum and egg containing media. Articles heated at 80-85°C for 30 minutes on three succcessive days. E.g: Loeffler's serum slope and Jowestein Jensen medium.
  • Koch's steamerEmploys moist heat at 100°C. Articles are exposed to steam for a duration of 20 minutes for three consecutive days (tyndallization) or for a duration of 90 minutes (free steaming). Media such as selenite broth, gelatin and sugar containing media are sterilized.
  • Candle filterBasically made of diatomaceous earth or porcelain and baked into shape of candle. Different types of earthenware filters are Pasteur-Chamberland filter, Berkefeld filter and Mandler filter. Used for clarifying liquids.
  • Seitz FilterEmploys a disc made of asbestos inside a metal casing. Chrysoile type asbestos is used. Discs are used and discarded whereas metal holder sterilized by autoclaving. Three grades: HP/PYR, HP/EKS, HP/EK. Used for filter sterilzation or clarifying of heat labile liquids.
  • Durham's tubeSmall glass tubes measuring 6x50mm are placed inverted inside a bigger tube. Used for detection of gas production in sugar fermentation tests. Sterilized in hot-air oven.
  • Lovibond comparatorA device used to adjust pH of liquid medium with chemical pH indicators. Consists of a disc with coloured circles and corresponding pH values. pH of medium is adjusted to match the colour in the circle.
  • McIntosh Fildes JarDevice used to generate anerobic conditions that works on evacuation-replacement technique. Air is evacuated using vaccuum pump and replaced by a mixture of N2+CO2+H2. Residual oxygen is removed by combining with H2 using palladium catalyst.
  • Microtitre plateMade of polystyrene or perspex. Consists of 96 wells; eight rows of 12 wells. Used in hemagglutination, hemagglutination-inhibition test and antibiotic susceptibility testing for MIC values.
  • Pasteur pipetteUngraduated glass pipette with rubber teat/bulb. Length can range from 150mm to 340mm. Glass tube sterilized in hot air oven. Used for aseptic transfer of liquids.
  • Sterile cotton swabCotton wound around wooden stick is used for collecting certain clinical material for diagnosis as well as for performing antibiotic susceptibility test by disk diffusion. Swab is kept inside a glass tube and sterilized in hot air oven.
  • VDRL slideAlso known as Kline concavity slides, this glass slide measures 3 x 2 ¼ inch x 3 mm thick, and have 12 concavities measuring 16 mm in diameter and 1.75 mm in depth. Used for performing VDRL test for syphilis.
  • Widal rackSteel rack for holding tubes while performing Widal tube agglutination test. Round bottom Felix tube is used for O antigen where as conical bottom Dreyer's tube is used for H antigen.
  • javascript sliderInoculating wire, bacteriological loop and spud. Nichrome wire of 0.5 SWG is held firmly in a holder. Sterilized by flaming in bunsen flame.
  • Tuberculin syringeUsed for performing intradermal skin tests. Volume of 0.1ml is injected intradermally.
Autoclave1 Arnold steamer2 Hot air oven3 Inspissator4 Koch's steamer5 Candle filter6 Seitz Filter7 Durham's tube8 Lovibond comparator9 McIntosh Fildes Jar10 Microtitre plate11 Pasteur pipette12 Sterile cotton swab13 VDRL slide14 Widal rack15 Inoculation instruments16 Tuberculin syringe17
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