Disinfectant: kills the vegetative forms – does not kill their spores. – used on inanimate objects.
Germicide: kills vegetative form but not their spores.
Antiseptic: applied to the surface of the body – prevent multiplication, (either by killing Mos or by inhibiting their growth and metabolic activities. (Often used on cuts or abrasions to prevent infection).
Sanitizer: microbial populations could not exceed specific numbers. Agent that kills 99.9% of microorganisms contaminating an area. – commonly applied to inanimate objects.
6. Minimum inactivation by extraneous material: when combine with proteins or other organic materials found in the substance being treated, this decreases the amount of the chemical available for action against microorganism.
7. Activity at ordinary temperatures: It should not be necessary to raise the temperature beyond that normally found in the environment were the agent is to be used.
8. Ability to penetrate: Unless the chemical can penetrate the surface, its antimicrobial action is limited to the site of application.
9. Material safety: The compound should not rest or other wise disfigure metals, nor should it stain or damage fabrics.
10. Deodorizing ability: The agent should either be oderless or have a pleasant smell.
11. Detergent ability: Should has cleansing properties
12. Availability and low cost: The product should be readily available and inexpensive.
Disinfectant must be effective against a wide variety of infectious agents (gram +ve and gram –ve bacteria, acid fast bacteria, bacterial endospores, fungi and viruses) at high dilutions and in the presence of organic matter.
The disinfectant must have the following properties:
The chemical must be toxic for infectious agent.
Should not be toxic to people
Should be stable upon storage.
Should be oderless or with a pleasant odor.
Should be soluble in water and lipids for penetration into microorganisms.
Antibiotics were initially isolated from one species of organism and were found to inhibit the growth of another.
There are a number of very important criteria which need to be considered when trying to optimise treatment for a bacterial infection:
1. Spectrum of activity of the drug/any resistance
Use a drug which is effective against the infecting organism. Hence, cultures should be taken to try and identify the organism first before initiating antimicrobial therapy.
Also, cultures of the organism can be tested to see whether or not they are resistant to any antibiotic. Once we have this sensitivity data? it is possible to modify the therapy by choosing agents to which the organism is not resistant.
Narrowest spectrum antibiotics are specific for certain bacteria and hence limit the spread of resistance. Broad spectrum antibiotics not only affect the bacteria in question, but many others which are present .
Also the dose and duration needs to be considered. Subtherapeutic doses often lead to resistance.
Sometimes an alternative drug needs to be used if a person has an allergic reaction to the drug being used (common in penicillin).
Patient factors such as age and any underlying disease needs to be considered – often the dose needs to be altered to prevent toxicity. e.g. A lot of’ drugs are excreted by the kidney and kidney function in the elderly is often decreased. Chloramphenicol in the young can be toxic since its metabolism is dependent on the liver. which is immature (may lack certain metabolic enzymes) in the neonate.
Sometimes a combination of drugs may be useful (e.g. amoxycillin with clavulanic acid), while other combinations may not be.
4. Bacteristatic vs. bactericidal
In an immunocompetent host, a bacteristatic agent may be sufficient to limit the infection but may not be appropriate in an immuno compromised host. In these cases, a bactericidal agent is better.
Often there is pressure from patients to prescribe a certain antibiotic. e.g. Treatment of a streptococcal throat infection is often with prescription of penicillin. However, if no antibioitic treatment were given then the person would recover in about the same time - hence there is no benefit in using an antibiotic (more likelihood of side effects and development of resistance), However. if the doctor does not prescribe penicillin and the patient is expecting it, then problems may arise with the doctor patient relationship.