CHAPTER XIII 



APPLICATIONS OF BACTERIOLOGY 



DIAGNOSTIC METHODS 



Direct diagnostic methods Direct diagnosis of the microbe Cultures 

 from the blood Examination of faeces Indirect diagnostic methods 

 Cytodiagnoses. 



Biological diagnostic methods Agglutination : specificity and group 

 agglutinations : variations in bacteria from the agglutination point of 

 view Precipitation : employment in forensic medicine and in the 

 adulteration of foods Applications to anthropology : confirmation of 

 the simian origin of man Complement-fixation : first experiment of 

 Bordet : clinical application Wassermann's reaction and the sero- 

 diagnosis of syphilis The nature of the substances coming into play 

 in this reaction Supcrscnsitive reactions : tuberculin. 



THE simplest and surest way to diagnose an infectious 

 disease is to demonstrate the presence of the specific microbe, 

 /.*., direct bacteriological diagnosis. When this is impossible, 

 indirect diagnosis is resorted to, i.e., the lesions of the tissues 

 which are constant accompaniments of a virus which is 

 invisible are sought for. The presence in exudates of certain 

 cell elements is noted, or the body-fluids and bacteria are 

 made to react together specifically (antibodies and antigens) : 

 in the latter case it is more properly a case of biological 

 diagnosis. 



Direct Diagnostic Methods. 



The microbe is sought for wherever there is a possibility 

 of finding it; blood, exudates and transudates, pus, mucous 

 discharges, false membranes, ulcers and chancres, sputum, 



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