Quantitative recovery of spores from thermophilic spore papers.

Abstract

SUMMARY A homogeniser (Stomacher 400) which does not damage bacteria has been used to produce an homogenate of spore papers, from which it was possible to make quantitative assessments of viable spores recoverable from such papers before and after exposure to sterilising procedures.After being discouraged for many years, the use of spore papers has now regained favour in the absence of satisfactory physical tests for ethylene oxide and formaldehyde sterilising processes. Such tests depend on the inclusion of suitable standard spore preparations in appropriate test pieces (Line and Pickerill, 1973;Mitchell and Alder, 1975) and their examination for spores remaining viable after exposure to the sterilising process. Customary practice is to transfer the spore paper aseptically to tryptone-soya broth and to incubate at 560C for 14 days. As a method this has the disadvantage that growth, if it occurs, may result from one surviving spore or from many; there will even be occasions when growth will result from contaminants introduced at the time of sampling or culture. However, all such 'positive' results will carry equal weight in the assessment of the sterilising process. What would be preferable, though hitherto considered impossible, would be the quantitative recovery of spores from papers so that not only could the initial loading of the papers be checked but also the survival rates could be determined. Kelsey (1961) stated that in spite of the employment of a variety of the then available disintegrative procedures no quantitative recovery technique could be devised because the spores remained caught up in the filter paper fibres. We here describe a simple method for the quantitative recovery of spores from spore paper in which homogenization (accomplished using a recently introduced machine developed specially for microbiological analyses) is followed by a modification of the surface dropwise counting technique of Miles and Misra (1938).

Quantitative assessment of sterilization efficiency using lyophilized calcium alginate biological indicators

“…Thus, it has been frequently reported that commercially available BIs do not conform to the requirements of the regulatory authorities or indeed the performance claims of the manufacturers (Hodges 1982~. Most of the preparations currently available are designed simply to give a positive or negative result indicated by the presence or absence of growth following incubation after the BI has been transferred from the autoclave load to a suitable culture medium. Criticism that the resulting growth could equally have come from a single surviving s#pore as many thousands has led to attempts to quantify recovery of spores after processing (Everall and Morris 1978). This paper describes the use of a carrier for bacterial spores which may have application for both dry and moist heat sterilization and which will readily permit quantification of spore survival.…”

Recovery of spores from impregnated filter paper.

“…Filter paper discs impregnated with spores are commonly used for testing various sterilising procedures. Kelsey (1961) and, more recently, Everall and Morris (1978) claimed that the quantitative recovery of spores from such discs was difficult, and the latter workers described a method of achieving it by means of a macerating machine. In this laboratory the task is accomplished by a simple hand shaking procedure, which takes 15 seconds or less.…”

A non-specific agglutination problem in the rubella haemagglutination-inhibition test using trypsinised human red cells.

“…Kelsey (1961) and, more recently, Everall and Morris (1978) claimed that the quantitative recovery of spores from such discs was difficult, and the latter workers described a method of achieving it by means of a macerating machine. In this laboratory the task is accomplished by a simple hand shaking procedure, which takes 15 seconds or less.…”