Bacteria to develop immunity...it seems to me that this is a question of practical importance...

... I am usually very reluctant to express my view on matters that lie outside my field of competence. However, having glanced through the detailed research program that you enclosed in your letter I decided to share an observation with you:I fail to find among the itemized points of study one aspect which, in my humble opinion, should have been of particular interest.I am referring to the recognition that certain microbes and infections may be particularly linked to hospitals - a view which, I believe, has received some attention in pertinent literature.I am not familiar with the details of this problem, but I believe it has to do with the ability of bacteria to develop immunity to antibiotics, as has been established in the case of penicillin, etc.Hence, it is very possible that methods of infection control that are effective elsewhere may lose their effectiveness because of their continued and consistent application in hospitals, causing the bacteria to become immune to this form of infection control, or because the hospital environment has produced certain strains of certain bacteria, which has given them a measure of immunity in that specific environment. ...I do not know whether the omission of this aspect from your project is due to the fact that a three-month study period would not be sufficient to include an investigation into this area, since, undoubtedly, it would entail the problem of distinguishing "immunized" from "non-immunized" bacteria, etc., as well as the problems of changing methods of sterilization and infection control and clinical observation, etc. Or, simply, because this question is outside your present work.Yet, it seems to me that this is a question of practical importance and should be well within your field of interest.

Freely translated and adapted

Erev Lag BaOmer, 5729 (1969)