2006, Vol 1 No 2, Article 10

Drug Resistance

Aijaz Ahmad Banday
BVSc & AH, MVSc (Veterinary Microbiology)

INTRODUCTION

The most serious current problem in relation to the use of anti microbial drugs in the control of infectious diseases is the increasing frequency with which bacterial resistance to some of these substances has developed. In practice this means that the treatment of specific infection with an antibiotic agent known to be potentially active against a particular microbial species may be ineffective when used for the treatment of certain outbreaks of that infection.

HOW DRUG RESISTANCE IS DEVELOPING

Detailed investigations have revealed that the property of multiple drug resistance can be transferred from the resistant strains of Escherechia to Shigella in the intestinal tract of the patients as well as in vitro under laboratory conditions. Further investigations have shown that the transfer of multiple drug resistance can take place among the majority of genera of family Enterobacteraciae as well as in certain other genera. These observations as well as epidemiological aspects of this problem have lead to world wide investigations in relation to the control of infectious diseases in animals and man by anti microbial drugs. It is now known that within the family Enterobacteraciae the multiple drug resistance may be transferred by conjugation from one bacterium to another by means of episomes known as R factors (resistance factors) in association with resistance transfer factor s (RTF).
The episomes that consist of DNA occur in the cytoplasm of the donor bacterium and multiply independently of the chromosomal DNA. Thus a bacterium with an R factor only is a cell that is resistant to one or more anti microbial drugs but is not able to transfer this resistance to another susceptible cell. on the other hand, a bacterium with both an R factor and RTF is both resistant and capable under suitable conditions of transferring the resistance to another susceptible host. It is now known that this transfer of antibiotic resistance from one bacterium into another can take place not only in the normal bacterial flora of the intestines of animals (e.g. calves, chickens, pigs) but also in the absence of antibiotics in the environment; that the frequency with which in vivo transfers take place will be higher when colonization of the bacteria occurs in the intestines and that transfer can occur between bacteria belonging to the same genius for example from Escherechia coli to Escherechia coli or from one related genus to another for example Escherechia coli to Salmonella typhimurium.

WHAT TO EXPECT AND HOW TO HANDLE IT

This newly acquired knowledge means the original assumption that drug resistance developed in bacterial population by a natural process of selection over a prolonged period of time and only in the presence of the particular antibiotic, is not the sole method by which the resistance can occur. These latest investigations have shown that by means of R factors and RTF microbial resistance to drugs may also develop quickly and can be transferred from one bacterial species to another and the process can continue in the absence of the antibiotic from the microbial environment.
During recent years the widespread use of antibiotic in the field of the veterinary medicine and their further use as additives in animal foodstuffs to promote growth, have resulted in the development of increasing numbers of bacterial strains possessing resistance to many of the drugs in common use and this is becoming particularly evident among the strains of Salmonella and Escherechia. Although it’s possible for human intestinal bacterial pathogens to develop drug resistance from the bacterial strains derived from animals, but present evidence would indicate that this may not be the most important mode of development of drug resistance currently observed in man, but it may be more commonly the results of antimicrobial therapy in vogue through human medicine. However both the veterinary and medical aspects of drug resistance are serious problems and the use of drugs in veterinary medicine which also apply to the treatment of human diseases must be made with discretion.

Editors Note:

This brief yet visionary article had been written by the author almost two decades back. Tragically Dr. Aijaz Ahmad Banday died at a very young age. The loss of a scientist of repute, as the author was, is irreparable. Kashvet and VetScan pay tribute to this son of the soil and feel honored by including this article of his in the issue.