Page 100 - The Veterinary Laboratory and Field Manual 3rd Edition

The selection, use, maintenance and quality control of laboratory equipment and supplies 69

• Use similar containers for the standard and should be heated through natural convection.
the test solutions and standardize the meter Fan-assisted incubators cause drying out of
at a pH close to that anticipated for the test bacteriology media and are therefore not very
solution. suitable for bacteriology (unless the Petri dishes
are wrapped up in a plastic bag). The incubator
should be fitted with an internal glass door.
Incubators In the laboratory, incubators may be used
for microbiological culture and for regulat-
Incubators (see Figure 2.33) are heated cabinets ing chemical reactions for biochemical tests
that are used to maintain a desired constant (ELISA, enzyme-linked immunosorbent assay).
temperature. The cabinets are heated by elec- The microbiology incubator should be kept for
tricity passed through heating elements situated culture use only due to the risk of contamination
around the lagged body of the cabinet and con- of other samples.
trolled by a thermostat. Most incubators have In countries with a land-climate, summers
timing switches. Most have an automatic ther- can be very warm and winters extremely cold.
mostat and a (digital) thermometer to allow In these countries incubators can be used in
regular checking of temperature (on a daily wintertime to provide room temperature (for
basis). Some units also have a humidity regula- incubating ELISA plates and for clotting of whole
tor (which will require the addition of water) or blood) and incubators with cooling capacity can
incubators can be designed to create a CO envi- be used for bacteriology when the surrounding
2
ronment (CO gas bottle needed). The incubator temperature rises above 37°C.
2
There are small and inexpensive incubators
available for district laboratories with a few
specimens requiring culture or where there is
a need of portability. The DC-powered Cultura
M incubator can be powered from a car cigarette
lighter plus the mains for maximum flexibility.

Care and maintenance

• An incubator should be fitted with a digi-
tal temperature display or supplied with a
thermometer for insertion through the vent
hole in the roof of the incubator. Adjust the
thermostat until the display or thermometer
shows the correct reading, that is, 36°C, for
routine incubation of bacteriological cultures.
• Make sure the ventilation holes are not
obstructed.
• Do not overload the cabinet. There should
be adequate space for air convection around
contents.
Figure 2.33 Incubator. Photo: Willy Schauwers, • Switch off the incubator before disinfection
Provincial Institute for Hygiene, Antwerp, Belgium. and cleaning.

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