Prior to the beginning of the 20th Century, infectious diseases accounted for high morbidity and mortality worldwide. The average life expectancy at birth was 47 years (46 and 48 years for men and women respectively) even in the industrialized world. Infectious diseases such as smallpox, cholera, diphtheria, pneumonia, typhoid fever, plaque, tuberculosis, typhus, syphilis, etc. were rampant.1
The discovery of penicillin in 1928 by Sir Alexander Fleming (1881-1955) marked the beginning of the antibiotic revolution.2 Ernst Chain and Howard Florey purified the first penicillin, penicillin G, in 1942 but became widely available outside the Allied military in 1945.3 This marked the beginning of the antibiotic era.
This antibiotic era witnessed the discovery of many new antibiotics, and the period between the 1950s and 1970s was named the golden era of discovery of novel antibiotics, and no new classes of antibiotics have been discovered since then. After that, the approach to discovery of new drugs was the modification of existing antibiotics.4 The antibiotic era revolutionized the treatment of infectious diseases worldwide, although with much success in developed countries. In the US for example, the leading causes of death changed from communicable diseases to non-communicable diseases (cardiovascular disease, cancer, and stroke), the average life expectancy at birth rose to 78.8 years, and older population changed from 4% to 13% of the entire US population.1 And infectious diseases now become the problem of elderly, cancer patients, transplant patients, surgical patients, patients on immunosupp- ressive drugs and other at-risk groups in developed countries.5 Although the developing countries also recorded a lot of improvement in the morbidity and mortality rate, infectious diseases still disproportionately affect all age group in these parts of the world.5,6 This is due to a combination of other factors like poverty, inadequate public health measures, poor sanitation, poor vaccination coverage, etc.