By Bamidele Odumosu
The word ‘antimicrobial’ is a term used for any substance that has the potency of eradicating disease causing living things. In this category i.e. disease causing living things, bacteria, fungi, viruses, and parasites, are usually referred to as microbes due to their microscopic sizes. Antimicrobials include antibiotics that are specifically against bacteria, antifungals for fungi, and antiviral for a virus. Bacteria are predominantly involved in disease and infections common to man hence antibiotics are more commonly encountered among the available antimicrobials. Penicillin, the first antibiotic to be produced led to the discovery of many other antibiotics commercially for the treatment of various bacterial infections. Although there are other microbes that are responsible for other infections and diseases such as ringworm, malaria, herpes and chicken pox etc. Bacterial infection is more common because they are frequently encountered by humans and they have a rapid multiplication rate sometimes with minimal nutrient requirements.
The victory against bacterial infection has been long celebrated ever since the discovery of penicillin also known as ‘wonder drug’ in 1928 for the treatment of disease that miraculously saved millions of people from dying. The celebration didn’t last a decade when bacterial resistance to penicillin was discovered and treatment failure as a result of infections by resistant strains were observed. There were newly developed antibiotics that were targeted towards resistant bacteria but only worked for a short period of time before the development of resistance by bacteria were also observed. It seems as if the more the effort in developing newer antibiotics the more the bacteria develop resistance to them.
Antimicrobial agents have revolutionized the field of medicine in many ways but their use has been marred by the frequent discovery of resistant strains of bacteria that appears to be a global menace. Notably among the world’s most acknowledged resistant bacteria include Staphylococcus aureus known for its resistance to methicillin popularly known as methicillin-resistant Staphylococcus aureus (MRSA), another resistant bacteria called Mycobacterium tuberculosis responsible for tuberculosis infection has been known to be highly resistant to treatment by antibiotics. The question someone might want to ask is how and why bacteria develop resistance to antimicrobial agents such as antibiotics. The answer to this question may appear complex to a lay man but to make it simple it is better summed up by saying the man is the architect of his own fate. We cannot deny interplay of natural circumstances associated with bacterial resistance, however, the global spread of antimicrobial resistance today is largely influenced by human activities.
To understand the issue of resistance, a little insight into how bacteria develop resistance is needful. Resistance to antibiotics in bacteria is either intrinsic i.e. naturally or by the acquisition of resistance genes from a closely related bacteria. Natural resistance to antibiotics are usually passed down to their offspring and the population increases with replication. This type of resistance is usually not a problem especially when antibiotics can be developed for this category of resistant bacteria. The real threat of antimicrobial therapy lies with bacteria that develop resistance via an acquisition of resistance traits from other bacteria. This phenomenon is usually mediated by transferable traits also known as resistance genes that are passed from one bacteria to another via mobile genetic elements. Human activities such as indiscriminate use and prescription of antibiotics, over the counter sales of antibiotics, agricultural and veterinary use are among the causes of antibiotic resistance. Currently, the world is battling a serious threat of bacterial pathogens that are resistant to essentially all of the available antibiotics. Acinetobacter baumannii, Pseudomonas aeruginosa, Klebsiella pneumoniae and Escherichia coli are among the top list of multiple drug resistant bacteria of global relevance as recently reported by the World Health Organisation.
Acquired resistance to antibiotics in bacteria via mobile genetic elements is the major weapon currently in use by bacteria to evade antimicrobial agent. Disturbingly, there is no new production of antibiotics in the last decades and microorganisms are constantly evolving in resistance mechanism with the trend. With the discovery of a mobile resistance gene mcr-1 that confers resistance to colistin, a last resort antibiotic for the treatment of extensive drug resistant bacteria recently found in E.coli and other Gram negative bacteria, the war between human and infectious bacteria appears to be favoring the pathogens. If care is not taken, we might slide into a pre-antibiotic era where bacterial infections are almost impossible to treat because of the presence of antimicrobial resistance genes.
Bamidele Odumosu, PhD is an expert in Pharmaceutical Microbiology and specializes in Antimicrobial resistance and drug resistant bacteria. He is currently a lecturer in the Department of Microbiology, in the University of Lagos