Aantibiotic are drugs, antivirus, antibacterial and anti fungal that has been formulated to combat invading pathogen.
We share our world with microorganisms; we are surrounded by vast numbers of these minute creatures, they are in the air, in the water, in the food we eat and some are living inside our bodies.
Bacteria causes diverse diseases and our immune system has evolved ways to fight those that are harmful how to cohabit peaceably with others.
Human has a balance of normal flora, a combination of microorganisms that inhabits the surface of the skin and the digestive tract, these microscopic forms of life are important in digestions of food and also as a barrier against pathogenic microorganisms.
Many bacteria does not harm the body unless there is a disruption in immune system balance, the patient’s immune system is depressed or an injury or stressors creates a breach in the immune system defence, and this condition could lead to the overgrowth of normal flora or more of one type of pathogenic organism.
The immune system can become so weak that it cannot fight off invading pathogen or restore the normal flora balance of the body, when this happens the doctor will recommend antibiotics for the patient.
Different antibiotics are effective against different types of microorganisms; some are narrow focused, meaning they are active against one specific microorganism and they do not disrupt the balance of normal flora, while others are broad spectrum, meaning, they act against a variety of microorganism. However, some microbes have developed resistance to drugs used in their treatment thereby rendering them useless.
What is antibiotics resistance?
Antibiotic resistance is therefore a form of drug resistance whereby some microorganisms are able to survive after treatment or exposure to one or more antibiotics.
Human do not develop resistance to drug, this phenomena is entirely a property of pathogenic organism. The ability of disease causing organisms to resist different type of drug is known as Multi Drug Resistance (MDR), or simply ‘Super Bug’.
Bacteria resistance strategies
Bacteria are not confined to any particular mechanism of resistance, rather they have different strategies and two pathogens may use different mechanism to withstand the same drug. Organism can alter their gene to produce mutants which are then selected for in the presence of a chemotherapeutic agent; these mutants usually arise from spontaneous or induced genetic mutation or acquisition of gene from other bacteria species through asexual reproduction processes such as conjugation, transformation or transduction. The process involves horizontal transfer of gene.
Many antibiotic resistance plasmids are found on transmissible plasmids, this makes their transfer possible. They contains gene that causes resistance to different drugs.
When disease agents are exposed to antibiotics, they will naturally choose to use the gene for resistant to withstand the antibiotics and survive, bacteria can use this method to spread the gene for resistance in their natural environment.
Some may become resistant by simply blocking the passage of drugs. This is common in most Gram +ve bacteria, these group of microscopic organisms are unaffected by Penicillin G’’’’’’’. Antibiotic cannot penetrate the envelope outer membrane. Organisms develop Penicillin resistance by changing its binding protein.
Bacteria can become resistance to sulfonamides by decreasing their cell wall permeability
There is also the case of Mycobacterium, that uses mycotic acid in a complex lipid layer outside their peptidoglycan to resist treatment.
Some bacteria can pump drugs out of their cell after it has penetrated the cell wall barriers, other have Plasma Membrane Translocaies, known as efflux pumps, these pumps; expel the drugs from the cell, these protein channel are very many and are non specific, as a result, they are regarded as multi drug resistant pumps..
Another resistance strategy is by the use of drug/proton antiporters, this simply means that as proton enters the cell, drug leaves, bacteria that employs this strategy includes E. coli, P. aeruginosa and S. aureus.
Chemical modification is another resistant strategy use by pathogen, drugs are inactivated or activated, and an example of chemical modification is the hydrolysis of better lactam ring of penicillin by enzyme penicillase.
Drugs can be activated by the addition of chemical groups, for example, chloramphenycol has two hydroxyl groups that can be acetylated in a reaction catalyzed by the enzyme chloramphenycol acyltransferase with acetyl COA as donor, acetyltransferase catalysis the acetylation of amino acid.
Aminoglycoside can be modified and activated in several ways, some of their enzyme catalyses the addition of hydroxyl group into either phosphate (phosphotransferase) or adenyl group (adenyltransferase).
Bacteria may also use an alternate pathway to evade the sequence inhibited by the agent or increase the production of target metabolites.
Definition of Terms
Plasmids: a genetic particle in bacteria cell that can replicate independent of chromosome, they are found in the cytoplasm and are important in drug resistance.
Normal flora: these are microorganisms that live on host without causing disease or interfering with normal body function. However they can become infectious when a breach occur in the immune system barriers.
Pathogen: Disease causing organism
Peptidoglycan: is a phospholipids bilayer that forms a mesh outside the plasma membrane of bacteria, its s important in Gram staining
Mutants: phenotype in which mutation is manifested; it is also a gene that is rare and usually harmful in contrast to a wild-type gene not newly generated
Chemotherapeutic agent: are drugs used to inhibit the proliferation in rapidly multiplying cells.