Mercury antibacterial action

The test identifies the substance to be examined as either a salt of mercury, Hg2 + or Hg + or a substance containing covalently bound mercury. At the present, reference to mercury is made in only two monographs. One is an inorganic salt mercuric chloride, HgCl2, which has antibacterial action through precipitation proteins and thimerosal (Figure 3.24.1), which likewise is an antiseptic but also a preservative in pharmaceutical product. The use... 

Mercuric chloride, other mercury-containing antibacterials and silver will inhibit enzymes in the membrane, and for that matter in the cytoplasm, which contain thiol, -SH, groups. A similar achon is shown by 2-bromo-2-nitropropan-l,3-diol (bronopol) and iso-thiazolones. Under appropriate condihons the toxic action on cell thiol groups may be reversed by addition of an extrinsic thiol compound, for example cysteine or thioglycollic aeid (see also Chapters 12 and 23). 

Silver and mercury salts have a long history of use as antibacterial agents.241-243 The use of mercurochrome ((40), Figure 18) as a topical disinfectant is now discouraged. Silver sulfadiazene (38) finds use for treatment of severe burns the polymeric material slowly releases the antibacterial Ag+ ion. Silver nitrate is still used in many countries to prevent ophthalmic disease in newborn children.244 The mechanism of action of Ag and Hg is through slow release of the active metal ion—inhibition of thiol function in bacterial cell walls gives a rationale for the specificity of bacteriocidal action. 

The number of proteins capable of metal interaction is enormous but actions of gold in arthritis (Chapter 11), and mercury in diuretics (Chapter 12.1), are two examples which may be traced to enzyme inhibition. The antibacterial effect of mercury is also probably due to enzyme inhibition (Chapter 9.1.1), contrasting with the inhibition of DNA synthesis by silver (Chapter 9.1.2). 

Antibacterial complexes such as silver sulfadiazene and some mercurials also manifest antiviral activity [51, 52]. Mersalyl, a diuretic (Chapter 12), has some in vivo action when mice treated with lethal doses of coxsackie virus are then administered the mercury complex [53]. The levels needed for 100% inactivation in vitro by mercurials is dependent on the virus, and thiols reverse the antiviral effect [54]. Conformational changes and breakdown into subunits have also been observed after mercury treatment [51],... 

Chelating agents may manifest their antiviral activity by metal sequestration and, as with bacteria and parasites, the natural differences between the host and invading cells may be exploited. Chelating agents with antiviral activity include the thiosemicarbazones, 1,10-phenanthrolines and phosphonoacetates. The latter compounds may act by zinc chelation. Metal complexes with antiviral action are platinum and palladium amines, as well as the antibacterial silver and mercury species. 

Amino- and hydrazino-quinazolines exhibited antibacterial activity and a patent claim on the in vitro action of 2,4-diamino-quinazolines was made. " The preparation of thiopegan derivatives as potential antimalarials and antibacterials deserves mention. Complete inhibition of influenza virus in vitro but not in vivo was shown by, 6,8-dichloro-2,4-dihydroxyquinazoline and other cyclic ureas. Activity against trachoma virus was also displayed by several 2-trichloromethylquinazolines. 7-Chloro-6-sulfonamido-4(37I)quinazolinones are more effective than the mercury diuretics and can be administered orally. The 1 -dihydro derivatives are even more effective and one (59) has been marketed under the name Quinethazone. ... 

---