Death and lysis of leptospirae when cultured in asbestos-filtered growth media

Our plain-English summary of Death and lysis of leptospirae when cultured in asbestos-filtered growth media, by H.C. Ellinghausen (Applied Microbiology, 1973).

The study

• Author: H.C. Ellinghausen
• Journal: Applied Microbiology
• Published: 1973;26(6):959-68
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Death and lysis of leptospirae, when cultured in asbestos-filtered bovine albumin polysorbate 80 media, was quantitated. The pathogens (virulent and avirulent) required 2 x 10(6) cells/ml to initiate growth in such media, whereas inocula of 2 to 20 cells/ml grew in control medium. Saprophytic leptospirae initiated growth from 2 cells/ml in asbestos-filtered medium as well as control medium. The adverse action of asbestos-filtered medium was not removed by storage of medium for 2 years at 25 C and was not diminished when such medium was frozen at -80 C. Washing with water, HCl and NaHCO(3)-NaCl, citric acid, and medium components did not remove the lytic activity associated with asbestos-filtered culture medium. Continuous subculture in asbestos-filtered medium was possible from large inocula; however, upon subsequent dilution and reinoculation into asbestos-filtered media, there was no evidence of acquired resistance, and all pathogens failed to grow.

In plain English

This was a laboratory study by a single author at the U.S. Department of Agriculture's National Animal Disease Laboratory in Ames, Iowa. It did not study people or asbestos disease. It tested leptospirae, bacteria some of which cause disease, grown in a bovine albumin polysorbate 80 (BA-P80) culture medium that had been sterilized by passing it through asbestos filter pads. Thirty-seven strains were tested. Disease-causing (pathogenic) strains, both virulent and avirulent, needed about 2 million cells per ml to start growing in asbestos-filtered medium, while 2 to 20 cells per ml grew in control medium. Smaller inocula died. Twenty lots of pads, from all three leading U.S. pad manufacturers, gave the same result. Storing the medium for 2 years, freezing it at -80 C, or washing the pads with water, acids or medium components did not remove the effect. Saprophytic (non-pathogenic) strains grew from 2 cells per ml and were sometimes stimulated. Repeated subculture produced no resistance. The author concluded that the effect was not a simple process and that its cause remained unproved.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: laboratory experiment (bacterial culture study)
• Who was studied: 37 strains of leptospirae (pathogenic virulent and avirulent, saprophytic, and unclassified), tested at the National Animal Disease Laboratory, Ames, Iowa. Serotype pomona (DM2H) was used for most detailed experiments.
• Exposure: BA-P80 culture medium filtered through asbestos filter pads (sterilizing and clarifying pads, including 0.025, 0.1 and 1.0 micrometer pads) from the three leading U.S. manufacturers, 20 lots. The article does not name the asbestos fiber type in the pads. The comparison was control medium (autoclaved basal medium plus membrane-filtered albumin) and membrane-filtered medium.
• Main results:
  • Pathogenic strains (virulent and avirulent) required 2 x 10^6 cells/ml to start growth in asbestos-filtered medium. In control medium, inocula of 2 to 20 cells/ml grew.
  • For pomona (DM2H), growth was negative with inocula of 2 x 10^5 cells/ml or less in every lot of asbestos-filtered medium. These cultures were not viable on subculture.
  • No asbestos pad from any source, used as supplied or after washing, was satisfactory.
  • All 32 pathogenic strains were sensitive to the lytic effect. There was no correlation between virulence and sensitivity.
  • Saprophytic strains grew from 2 cells/ml in asbestos-filtered medium, as they did in control medium. At 7 days their growth was stimulated in asbestos-filtered medium, varying with strain, inoculum and incubation time.
  • Storage of asbestos-filtered medium for 2 years at 25 C did not remove its adverse effect, and freezing it at -80 C did not diminish the effect.
  • Washing the pads with water, HCl followed by NaHCO3-NaCl, citric acid, or medium components did not remove the lytic activity.
  • For pomona (DM2H), survival depended on exposure time and inoculum size. Cultures of 200,000 cells/ml were viable at 72 hours of exposure but not after 76 hours. At 2 cells/ml, the culture could not be recovered even at zero hours.
  • After 4 serial subcultures in asbestos-filtered medium, pathogens re-diluted to 2 x 10^5 cells/ml or less had acquired no resistance.
  • Growth in asbestos-filtered medium produced no substantial changes in cross-agglutinating activity of copenhageni M-20 in the microscopic agglutination test. Similar observations were made with four other serotypes.
• The authors' conclusion: The author concluded that the lytic action of asbestos-filtered medium on pathogenic leptospirae is not a simple process and probably not due to a single chemical. It remained to be proved whether a soluble or a particulate entity from the pads, or both, was responsible. The author also speculated, without testing it, that the mechanism may have some application to human health.
• Limitations the authors state:
  • The author states that the cause of the lytic activity was not identified: whether it is soluble, particulate, or both remained unproved.
  • Cross-agglutinating absorption studies were not performed.
  • The reason pathogens and saprophytes reacted differently remained unanswered.

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