BACTERICIDAL PEOPERTIES 15 



1. Type of Organism. — In the early days of antisep- 

 sis, disinfectants were tested bacteriologically with the 

 idea of discovering some chemical agent that would 

 destroy all known bacteria when used in a weak solution. 

 No such universal antiseptic has been found. On the 

 contrary, it has been found that different antiseptics 

 have a selective action upon certain types of organisms. 

 For example, bichlorid of mercury is a most powerful 

 disinfectant for anthrax, but has only a weak action 

 on tubercle bacilli and is much less effective than some 

 other drugs (creolin, lysol, alcohol) for superficial dis- 

 infection of the skin, while carbolic acid is relatively 

 ineffective against tetanus bacilli, anthrax spores, and 

 tubercle bacilli. It therefore follows that in disinfec- 

 tion the different organisms and bacteria must be con- 

 sidered individually. In general, it can be said that 

 spore-bearing bacteria require stronger disinfectants 

 than non-spore bearers. Here again individual differ- 

 ences in resistance of species of spores and vegetative 

 forms manifest themselves. It is, therefore, difficult to 

 make a comparative table of individual drugs. In gen- 

 eral, the strongest disinfectants which also destroy spores 

 are mercuric chlorid, silver nitrate, iodin, creolin, lysol, 

 liquor cresolis compound and other cresol preparations, 

 and formalin. The weaker disinfectants which kill only 

 spore-free organisms are coal tar, carbolic acid, salicylic 

 acid, dyes, boric acid, and calcium lyes (whitewash) and 

 acids. 



Individual Resistance of Organisms. — The individual 

 resistance of different organisms varies. Some infectious 

 agents are .very r^gadily ,destroyed while others are very 

 resistant. For practical purposes disease-producing 

 micro-organisms may be- divided into two groups on the 

 basis of their power to resist. disinfection. 



