CHAPTER V 

 DIAGNOSIS 



A bare knowledge of the morphology and biology of pathogenic bacteria is of 

 little value in diagnosis unless we also know how, when and where to search for a 

 them in disease. Some of this information has been imparted in the previous 

 chapters, here an attempt will be made to add additional information that may 

 serve in attempts to disclose the offending organism present in infectious 

 diseases. 



DISEASES OF THE SKIN 



Some skin diseases are caused by bacteria and others are not. Of the organ- 

 isms which attack the skin the staphylococcus is probably the most frequent 

 offender. Since the staphylococcus albus is practically always present upon the 

 skin in health and disease, we cannot with assurance look upon it as an etiolog- 

 ical factor when obtained in smears or cultures taken from skin lesions, except 

 under the following conditions : 



1. When possible contamination by contact with the surface of the skin of 

 the operator or of the patient has been precluded. 



2. When the organism has been found in pure culture after attempts to dis- 

 cover other organisms, especially the acne bacillus, have failed. 



ACNE 



Acne may be caused by the acne bacillus or the staphylococcus. The 

 staphylococcus is found in slides and aerobic cultures made from the core of acne 

 lesions in practically all cases, whether due to the staphylococcus or the acne 

 bacillus. 



The acne bacillus is an obligate anaerobe, to obtain it in pure culture from an 

 acne lesion proceed as follows : Wash the skin surrounding the pimple with soap 

 and water and alcohol, remove the top of the pimple with a sterile needle, obtain 

 the lower half of the core with a sterile platinum loop (avoiding contact of either 

 loop or removed material with the patient's skin or any object), plant slant tubes 

 of agar, blood serum and a tube of bouillon and incubate anaerobically at 37C. 

 for 10 days (by incubating for 10 days the acne bacillus will outgrow staphylo- 

 cocci that are present) . After planting culture media obtain a core as before and 

 smear in a thin film on cover glasses, gently heat until dry and stain one with 

 methylene blue, another by Gram's method. The acne bacillus is somewhat 

 similar in morphology to the diphtheria bacillus and is Gram positive. 



