ABSTRACT
Glass, rubber and stainless steel surfaces were exposed to various types of bacteria in the presence of milk and a number of milk components under both static and agitated incubation conditions. Numbers of bacteria attaching were enumerated by epifluorescence microscopy. Results were affected by the different bacterial types, the nature of the attachment surface and the substances in which the bacteria were suspended with a Moraxella-like species, stainless steel and lactose and non-casein protein solutions respectively resulting in greatest numbers of cells attaching. Agitation had no marked influence on attachment.
Subject(s)
Dairying/instrumentation , Milk/microbiology , Acinetobacter/isolation & purification , Alcaligenes/isolation & purification , Animals , Cattle , Female , Flavobacterium/isolation & purification , Moraxella/isolation & purification , Pseudomonas/isolation & purificationABSTRACT
Ethanol dehydration followed by argon replacement induced drying (ARID) was found to be a suitable method for the preparation of glass, stainless steel and rubber surfaces which had been in contact with inoculated milk and which were to be examined using scanning electron microscopy (SEM). This technique was used to examine samples of all three materials which had been subjected to both single and repeated inoculation with whole milk containing a Pseudomonas sp. or a Micrococcus sp. and incubated for various periods. Some samples were also prepared for SEM using a cryofixation technique. The Pseudomonas sp. was found to proliferate on glass and stainless steel surfaces but not on rubber. Due to the clumping tendency of the Micrococcus sp. proliferation of this organism was more difficult to assess accurately. In general there was no difference in results obtained between single and repeated inoculation. Various factors which may have aided attachment of micro-organisms to surfaces were identified viz., surface channels present in stainless steel, milk deposits and the production of extracellular material. The value of using both the cryofixation and chemical preparatory techniques for the identification of artifacts is discussed.
