Chemotherapy and antibiotics | Human Health & Diseases

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the term antibiotic strictly refers to substances that are of biological origin whereas the term chemotherapeutic agent refers to a synthetic chemical;
the distinction between these terms has been blurred because many of our newer “antibiotics” are actually chemically modified biological products or even chemically synthesized biological products;
the generic terms to refer to either antibiotics or chemotherapeutic agents are antimicrobic or antimicrobial agent.;
however, the term antibiotic is often used to refer to all types of antimicrobial agents.

chemotherapy is the use of drugs to treat or cure infections;
effective drugs show selective toxicity, killing the pathogen but having no effect on host cells;
there is a wide range of chemotherapeutic agents for bacterial and fungal infections, but few for viral infections;
some drugs are derived from natural compounds but others, such as isoniazid used for treatment of tuberculosis, are synthetic

although there are a number of different types of antibiotic they all work in one of two ways:

a bactericidal antibiotic kills the bacteria by either interfering with the formation of the bacterium’s cell wall or its cell contents; e.g. penicillin is a bactericidal;
a bacteriostatic stops bacteria from multiplying.

antibiotics interfere with some aspect of growth or metabolism of the target organism such as
- synthesis of bacterial walls;
- protein synthesis (transcription and translation);
- cell membrane function;
- enzyme action;
penicillin functions by preventing the synthesis of the cross links between the peptidoglycan polymers in the cell wall;
this means that they are only active against bacteria which are growing;
most types of bacteria have enzymes for destroying penicillin (penicillinases) and are therefore resistant to the antibiotic;
the main sites of action are shown in the diagram below:
different diseases are treated with different antibiotics;
all strains of some bacteria are resistant to several antibiotic; e.g. tuberculosis is resistant to penicillin;

antibiotics are classed as bactericidal or bacteriostatic according whether they kill bacterial cells directly or indirectly;
they are also divided into classes such as cephalosporins or macrolides depending in their chemical structure and action;
all antibiotics can also be described as either narrow spectrum or broad spectrum.
broad spectrum are effective against a wide range of bacteria
narrow spectrum are effective only against a few;

those with a narrow spectrum of action can kill only a small number of species of bacteria, maybe even just one;
narrow spectrum antibiotics tend to be very specific and act on a molecule in the metabolism of one particular type of bacteria that is special to that species;

the narrow-spectrum antibiotic will not kill as many of the normal microorganisms in the body as the broad spectrum antibiotics. So, tt has less ability to cause superinfection.
the narrow spectrum antibiotic will cause less resistance of the bacteria as it will deal with only specific bacteria.

narrow spectrum antibiotics can be used only if the causative organism is identified.
if you don’t choose the drug very carefully, the drug may not actually kill the microorganism causing the infection.

broad spectrum antibiotics are active against a wide range of bacterial species;
broad spectrum antibiotics act on structures or processes that are common to many different bacteria, such as the components of the cell wall.

antibiotics should be chosen carefully;
screening antibiotics against the strain of the bacterium or fungus isolated from sufferers ensures that the most effective antibiotic can be chosen;
the diagram below shows results of antibiotic sensitivity test carried out on a strain of the human gut bacterium coli that causes epidemics of food borne and water borne diseases;
bacteria are collected from feaces, or from food or water and grown on an alga medium;
different antibiotics are absorbed onto discs of filter paper placed on the agar plate;
the plate is incubated and the diameters of the inhibition zones where no bacteria are growing are measured;
the diameters are compared with standard diameters as in the tables below and the most appropriate antibiotics are chosen;
increasingly, bacteria which were once susceptible to antibiotics are now resistant;
this has a great impact on disease control as it prolongs epidemics, lengthening the period of time when people when people are ill and increasing the risk of higher mortality rates;
the inappropriate and widespread use of antibiotics should therefore be discouraged;
some drugs should be kept for use as a last resort when everything else has failed, and drug companies must continue to invest in research for new drugs to replace those which quickly become redundant;

kill pathogen after infection;
interfere with growth/metabolism of pathogen;
g. protein synthesis/synthesis of cell wall;
do not harm host;
not effective against viruses;
mainly used against bacteria and fungi;
some narrow spectrum/effective against a limited range of micro-organisms; – bacteria can become resistant

Below is a list of the most common side-effects of antibiotics:

diarrhoea – researchers from Stanford University School of Medicine found that rise in sugars in the gut following antibiotic treatment allows harmful bacteria to get a foothold and cause infection. Harmful bacteria thrive on sugar;
feeling and being sick;
infections of the mouth, digestive tract and vagina.

Below is a list of rare side-effects of antibiotics: