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Silver has been known for its ability to purify drinking water for at least 2000 years, but silver as an antibiotic has become evident in the past 100 years or so following discoveries in microbiology when Loius Pasteur and Robert Koch conducted fundamental research on the concepts of infection and transmission of disease.

Robert Koch established his principles of disease when he first diagnosed anthrax as a fatal infection in human patients and proved that it as caused by an 'organic' pathogen. Subsequent research by Pasteur and Koch in 1876-1877 on anthrax, and transfer of Bacillus anthrasis can be regarded as the starting point of modern pathogenic bacteriology.

It is not clear when the antibiotic properties of metallic silver were first recognized, but reviews of silver in healthcare commonly refer to silver vessels being used to transport drinking water for the monarchs of ancient Babylon, Rome and the Persian Empires. Records from the 14th century suggest that the value of silver in surgery as a means of alleviating disease was appreciated (1)

Ambrose Paré (1510-1590) was a perdiatric surgeon who attended the gunshot wounds of Henry II of France, and who pioneered silver clips and instruments in surgery and for life threatening conditions. Later surgeons such as John Woodall (1617) , surgeon general of the East India Company, also claimed that silver clips, silver instruments, silver nitrate and silver foil reduced the incidence of infections (2).

At the turn of the 20th century, metal salts including copper, lead, arsenic, bismuth, antimony, mercury and silver were commonly used to control bacterial and fungal infections (3). Mercury and Silver ions were most effective and provided greatest antibacterial action at a concentration of one part per million (ppm) (4). The term 'oligodynamic' coined by the German botanist Karl von Nägeli to describe the ability of micro-organisms to selectively absorb metal ions from dilute solutions (5) was used by pharmacologists at the time to denote high antibiotic efficacy of low concentrations of these metal ions. He was first to recognize that the bactericidal concentrations of silver solutions were related to the amount of free Ag+ within a system (6). Silver proteins of varying strengths were developed ni the early 20th century as an alternative to silver nitrate, although the colloidal form of metallic silver was thought by Dr. Henry Crookes to have profound germicidal action:

"certain metals in a colloidal state exhibit profound germicidal action, but are quite harmless to human beings. There is no microbe known that is not killed by colloidal silver in laboratory tests within six minutes". (7)

Henry Crookes produced silver colloids which were patented before the outbreak of WW1, and his company Crookes Laboratories eventually became Crookes Healthcare in the 1960's. In 1971 the successful pharmaceutical business was bought by Boots, which used 'Crookes' as a label for marketing brand names such as Nurofen, Strepsils and Optrex. (8)

References

1. D. G. Brater and W. J. Daly, Clinical Pharmacology in the Middle Ages: principles that presage the 21st century, Clinical Pharmacology and Therapeutics., 2000, 67, 447.

2. A. B. G. Lansdown, Pin and needle tract infections: the prophylactic role of silver, Wounds UK, 2006, 2, 4, 51

3. T. Solleman, Silver, in A Manual of Pharmacology and its Applications to Therapeutics and Toxicology, Saunders, Philadelphia, 1942, pp. 1102-1109

4. B. D. Davis, Principles of sterilization, in Bacterial and Mycotic Infections of Man, ed. R. J. Dubois, Lippincott, Philadelphia, 1952, pp. 707-725.

5. K. W. von Nägeli, Leben die oligodynamischen Erscheinungen an lebenden Zellen, Denkschr. Schweiz. Naturforsch. Ges. 1893, 33, 174

6. R. E. Burrell, A scientific perspective on the use of topical silver preparations, Ostomy Wound Management, 2003, 49 (Suppl.), 19

7. H. Crookes, Use of Colloidal Silver, London, 1910

8. W. H. Brock, Case of the Poisonous Socks, RSC Publishing, 2011