Fluctuations of Virulence 



23 



8 (1968) 



Observations of fluctuations of virulence of B. influenzae. 

 By FREDERIC PARKER, JR. and JULIA T. PARKER 



[From the Department of Bacteriology, College of Physicians 

 and Surgeons, Columbia University, New York City] 



Since the relationship of the Pfeififer bacillus to influenza is 

 still a matter of dispute, any observation having a bearing on 

 its epidemiological properties should have some value. This is 

 particularly true since the epidemiology of this disease presents 

 several features unexplainable at the present time, such as the 

 difference in morbidity and mortality between the first and sec- 

 ond waves, the success of isolating the organism in the disease 

 at one time and the failure at other times, the negative experi- 

 ments in human inoculations, etc. 



The work reported here may be divided into three parts : 



I. Results obtained working with a virulent meningeal 

 strain. 



II. Results obtained working with the same strain when 

 less virulent. 

 III. Results with other less virulent strains. 



I. The experiments in this part were done with a strain of 

 B. influenzae isolated from the spinal fluid of a case of influenzal 

 meningitis at the Nursery and Quids' Hospital on October 5th, 

 1921. This strain was kept in whole defibrinated rabbit's blood 

 without transplantation until December 21st, about 10 weeks 

 after isolation, when this work was started. When the organism 

 was first received on artificial media, it was extremely pleo- 

 morphic, showing many long forms and forms of considerable 

 size. It is interesting to note that later in exudates from the 

 animal body, the organisms were extremely small and coccoid in 

 shape; in fact, they looked so small that we attempted to filter 

 them through a Berkfeldt N but with negative results. 



We inoculated rabbits in the following ways with the results 

 given below : 



1. Intratracheal Rabbits were injected at first with choco- 

 late broth cultures, then, in the succeeding experiments, with 

 varying amounts of exudates of animals dead from inocula- 



