The effects of storage conditions on viability of Clostridium difficile vegetative cells and spores and toxin activity in human faeces

AIMS: Clostridium difficile is a common nosocomial pathogen and as such diagnostic and research methods may necessitate storage of faecal specimens for long periods, followed by subsequent re-examination. This study investigated the effects of storage conditions upon the viability of this organism and its toxin. METHODS: Three genotypically distinct strains of C difficile (two clinical isolates including the UK epidemic strain, and an environmental isolate) were grown anaerobically at 37°C for 72 hours in a pool of five faecal emulsions. Aliquots of each emulsion were stored at either -20°C (frozen) or 4°C (refrigerated). Emulsions were assayed for viable cells, spores, and cytotoxin titre before storage and at days 1, 3, 5, 7, 14, 28, and 56. An aliquot of each emulsion was also removed, assayed, and replaced in storage at each time point to investigate the effects of multiple freezing/refrigeration/thawing . RESULTS: Neither storage temperature nor multiple cycles of refrigeration/freezing and thawing adversely affected the viability of C difficilevegetative cells or spores. Single and multiple exposures of samples to 4°C had little effect upon the C difficile toxin titre. Toxin titres of multiply frozen and thawed faeces became significantly lower than for refrigerated faeces (p < 0.01) by day 5 of the experiment in two of the three strains, and in all strains by day 28. Toxin titres of singly frozen faeces became significantly lower than for refrigerated faeces (p < 0.01) by day 56 of the experiment in two of the three strains. CONCLUSION: Storage temperature and multiple cycles of freezing (refrigeration)/thawing had minimal effects upon the viability of C difficile or its spores. Storage at 4°C has no discernible effect on C difficile cytotoxin. However, storage at -20°C has a detrimental effect upon C difficile cytotoxin, and multiple cycles of freezing and thawing may further adversely effect toxin titres

History of solar-terrestrial relations as deduced from spacecraft and geomagnetic data: Solar M regions

This brief history is organized around the long problem of the solar M region, i.e. the structure on the sun that is responsible for recurrent geomagnetic disturbances

Solar activity and the weather

The attempts during the past century to establish a connection between solar activity and the weather are discussed; some critical remarks about the quality of much of the literature in this field are given. Several recent investigations are summarized. Use of the solar/interplanetary magnetic sector structure in future investigations is suggested to add an element of cohesiveness and interaction to these investigations

Solar Wind Disturbances Associated with Flares

Solar wind disturbances associated with flare

A synoptic approach to sun-weather investigations

The advantages of a regular program of daily observations of the magnetosphere, ionosphere and atmosphere are described. Such synoptic observations may be one of the best routes to understanding the physical mechanisms involved in sun-weather influences. Some specific examples of such observations are given

Why does the sun sometimes look like a magnetic monopole?

For several months in early 1965 the sun appeared to have large scale magnetic field directed outwards at nearly all latitudes and longitudes. Several independent observations that lead to this puzzling situation are discussed

Solar structure and terrestrial weather

The possibility that solar activity has discernible effects on terrestrial weather is considered. Research involving correlation of weather conditions with solar and geomagnetic activity is discussed

Asymmetry in geomagnetic response to the polarity of the interplanetary magnetic field

Geomagnetic asymmetric response as function of polarity pattern of interplanetary magnetic fiel

Geophysical predications: Sun-weather

The present status of sun-weather research is summarized. Recommendations for future research are given