Infectious drug resistance in bacteria: present facts and future prospects: submitted for the Lewis Cameron Undergraduate Prize in Bacteriology
Achong, Michael R.
The discovery of infectious (transferrable) drug resistance resulted from careful epidemiological observations on the changing pattern of drug resistant strains of Shigella in Japan ( Watanabe, 1963 a). From 1957 onwards a. large and increasing percentage of these strains, isolated from cases of bacillary dysentery, were found to be resistant to one or more of the commonly used antibiotics (for convenience, synthetic antibacterial drugs will be included in this term), namely, streptomycin, sulphonamides, chloramphenicol and tetracyclines. In a single outbreak of dysentery, resistant shigellae were isolated from some patients; even the same patient sometimes yielded sensitive and resistant shigellae of the same serotype. Moreover, the administration of a single anti- biotic to patients harbouring a sensitive organism could cause them to excrete bacteria that were resistant to all four of the aforementioned drugs. In some cases, patients who harboured drug -resistant shigellae also harboured strains of Esch. coli that were also resistant to these four antibiotics.About this time, it was widely accepted that the principal mechanism responsible for acquired drug resistance was spontaneous mutation at a low rate to a single drug resistance followed by the preferential growth of the resistant cells in the presence of that particular drug. However, this concept of spontaneous mutation followed by environmental selection could not account for these patterns of multiple drug - resistance in shigellae nor the rapid increase in its incidence, and Japanese workers proposed that the transfer of mi:.ltiple drug resistance from multiple drug -resistant Esch.. coli to shigellae in the intestinal tract of the patients was responsible for the epidemiological findings. Such a transfer was demonstrated independently by 2. Ochiai et al (1959) and -Akiba et al (1960) by cultivation of a mixture of resistant and sensitive strains in vitro and subsequently in human volunteers (Kagiwada et a1,1960 and in the sterile intestinal tract of newly hatched chicks ( Walton, 1966a)