APPLIED MICROBIOLOGY, Jan. 1972, p. 174-176Copyright © 1972 American Society for Microbiology

Vol. 23, No. 1Printed in U.S.A.

Inoculation Technique for Fungus CulturesRAMON M. FUSARO

Department of Dermatology, The University of Nebraska Medical Center, Omaha, Nebraska 68105

Received for publication 23 August 1971

A plastic straw and wood applicator stick serve as a simple, inexpensive, anddisposable inoculation unit for fungal studies. The method gives a uniform andintact inoculum. The technique is especially useful because a large number ofagar plates can be inoculated rapidly.

To inoculate a large number of Sabouraudagar plates with a fungus, the standard tech-niques can be time-consuming and do not al-ways give uniform (diameter) inoculations.The following is a description of a simple, in-expensive, and disposable method.The materials consist of plastic drinking

straws (4 mm in diameter by 26 cm in length;Carnival Straws Supra Plastic, National SodaStraw Co., Chicago, Ill.), which were cut intothirds, and 6-inch (ca. 15.2 cm) wood appli-cator sticks. A single applicator stick is in-serted into each straw and gas-sterilized(ethylene oxide).

Prior to the inoculation, a hole is made inthe center of the agar with another plasticstraw without an applicator stick (Fig. 1). Thesterile agar core cut by the plastic straw willremain within the tip of the straw when thestraw is withdrawn by sealing the other openend of the straw with the finger tip (Fig. 2).The same straw can then be used to remove 5to 10 more sterile agar cores from other platesas the entrapped agar cores act as suctionplugs.

When using the inoculating unit (plasticstraw with wood applicator stick), the middleportion of the straw is grasped and squeezed tohold the stick within the straw. The applicatorstick is pulled up into the tube so that its endis approximately 1 to 2 cm from the distal endof the plastic straw which will be inserted intothe fungus colony growing on Sabouraudagar. After punching to the bottom of the platethrough the agar (Fig. 3), the straw is rolledbetween the fingers to sever the core. Thestraw is then tilted to break the adhesive forceof the agar plug to the petri plate. The unit islifted out and the tip of the plastic straw con-taining the fungus plug is placed into the agarhole in the recipient plate (Fig. 4). The appli-cator stick is pushed gently down against theagar plug while the plastic straw is liftedslowly out of the agar hole, thereby placing theinoculum in the agar hole (Fig. 5).

It should be emphasized that the inoculumis uniform in diameter only, not cell number.The time necessary to inoculate many plates isminimal.

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FIG. 3. Inoculation unit cuts out the fungal inoc-FIG. 1. Plastic straw without an applicator stick ulum by rolling the straw between fingers.

inserted into recipient agar.

FIG. 2. Agar core remains in the tip of the strawas the index finger prevents entry of air at top ofstraw.

FIG. 4. Tip of the straw containing the fungalplug is inserted into the agar hole.

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FIG. 5. After pressing out plug and withdrawingstraw in one motion, the fungal inoculum remains inthe agar hole.

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