Microbes are micro-organisms, especially like bacteria that are responsible for various diseases. However, a number of them are also useful to us. Microbes are unicellular, minute organisms which are not visible to the naked eyes. A number of microbes are helpful to us in our routine life, while there are others that are detrimental for our health. The harmful microbes are known as pathogens.

Microbes that cause various diseases include viruses, bacteria, fungi, protozoa and a few types of worms. They invade the healthy host cells and subsequently interrupt or even impair the regular activities of the cells. When this happens, it results in widespread diseases.

Microbes have an effect on all living organisms on this planet. These micro-organisms are remarkably diverse and possess the ability to survive in an assortment of habitats ranging from the icy wastes of Antarctica to the hot springs. Many microbes also reside in the bodies of plants and animals.

In order to infect us, microbes first need to enter our body. The place from which they enter our body is called the portal entry. In fact, microbes can enter our body through four places which are described briefly here.

The different portal sites in our body

The portal entries include our respiratory tract (which include the nose and mouth). When influenza virus enters our body through this site, it causes flu. They can also enter the body through the gastrointestinal tract (such as the mouth oral cavity). For instance, when the Vibrio cholerae enters through this portal entry, it causes cholera. Microbes can also enter our body through the urogenital tract, such as when Escherichia coli which is responsible for cystitis. Sometimes, microbes also enter through the skin pores as in the case of Clostridium tetani which is responsible for tetanus.

How microbes make us fall sick

In order to infect us and make us fall ill, microbes first need to reach their target area inside the body. Next, they will need to bind themselves to the target area which they intend to infect and make sure that they are not extricated. Most importantly, after attaching themselves to the target site, microbes need to proliferate profusely and obtain the nutrients they need for their survival and proliferation from the host. They also need to survive inside the host and prevent being attacked by the immune system of the host.

Diseases caused by microbes

Micro-organisms or pathogens are responsible for various diseases in both plants as well as animals. Below are a few examples of the diseases caused by different microbes.

As is well known, viruses cause viral diseases, which include acute as well as infectious diseases such as common cold. In addition, they also cause chronic ailments such as AIDS. They are also responsible for polio, mumps, rabies and many others.

On the other hand, bacteria are responsible for diseases like cholera, typhoid, diphtheria and others.

Protozoa causes diseases such as malaria and sleeping sickness and several others.

Several minute worms also cause diseases. For instance, tapeworms and roundworms may cause diseases such as Taeniasis and Ascariasis respectively.

How microbes cause diseases: There are various ways by which microbes cause diseases and make us fall sick. After they enter the body of the host they attach themselves to their target site and start infecting it. At the same time, microbes begin to multiply copiously at the target site and get their necessary nutrients from the host. They also have to make efforts to survive and avoid being attacked by the host's immune system.

Groups of microbes

Microbes can be classified into various groups - bacteria, viruses, fungi, yeasts and parasites. A brief description of each of these groups is given below.


Bacteria are of various types. In fact, they are diverse in nature and the diseases they cause. However, not all types of bacteria are harmful for us. There are a number of bacteria that are not only helpful, but protective to humans. Some of these �beneficial� bacteria thrive naturally in our body, especially in the bowel and vagina, and they play an important role in protecting us from various types of infections. On the other hand, when some other types of bacteria infect us, they may be responsible for many serious ailments like pneumonia, meningitis, tuberculosis and several others. Usually, a course of antibiotics is necessary to treat bacterial infections.


Viruses are also disease-bearing microbes but they are different from bacteria. There are various types of viruses on this planet. In fact, viruses are responsible for most of the common and minor infections, which include sore throats, common colds, coughs, chicken pox and a number of diseases that are accompanied with rashes. It is worth mentioning here that most of the common infections in any community are caused by viral infections.

Compared to the bacterial and fungal infections, virus infections are more common and widespread too.

It is unfortunate that we still do not have effective antiviral medications for several viral infections. While antibiotics are an effective means of treating bacterial infections, there is no such common medicine to treat viral infections. However, we are fortunate that our immune system is generally capable of combating most of the viral infections within a specific period. In many cases, symptomatic treatments like taking paracetamol and/or ibuprofen may help to combat fever and catarrh. Such symptomatic treatments also necessitate ample rest and drinking plenty of fluids to get cured.

In addition, some antiviral medications are also available for treating specific viral infections. Some examples of such medicines include antiretroviral medicines to treat HIV. Similarly, acyclovir is generally used for treating herpes simplex virus infections. However, it needs to be underlined here that use of antiviral medicines does not help to eliminate the viruses from the body. Usually, such medicines just work to prevent the virus from multiplying within the body, thereby helping to check the virus as well as the infection caused by it.


There are various types of fungi and they cause multiple problems to humans, animals as well as plants. Generally, fungal infections cause harm to the human's skin and nails. They may be responsible for problems such as athlete's foot, ringworm and various skin rashes that occur locally. In addition, fungi may also cause infections in as well as around the nails. Many modern day creams are quite effective in quickly treating local fungal rashes. Nevertheless, at times nail infections caused by fungi can be somewhat bothersome and obdurate, generally requiring long-term treatments. Antifungal medicines are taken orally to treat such conditions.

Nearly all fungi in the environment are free-living. Some of them are also capable of infecting people who are healthy otherwise. They possess the ability to cause grave infections in some people, especially patients who suffer from a feeble immune system. For instance, cancer patients who have recently undergone chemotherapy are extremely susceptible to such serious fungal infections.


Though they are known as yeasts, actually these microbes are a type of fungus. There are various types of yeasts that are responsible for a variety of infections � the most common among such yeast infections is known as thrush. A variety of yeast known as Candida is responsible for thrush. Candida usually thrives best in the moist, warm and airless body areas. This particular yeast can infect the mouth as well as the vagina to cause thrush. In babies, yeast causes nappy rash. At times, yeast is also capable of infecting other body areas.

Anti-yeast creams as well as some medicines work well in treating infections caused by yeasts.


Parasite is a germ that requires a host (another living being) for its survival. It lives within or on another living being for its food. In other words, parasites are unable to make their own food and, hence, draw their food from their hosts.

Generally, parasites are found in polluted water and contaminated food. They are able to enter the body of the host by sexual conduct or through the openings made by insect bites. It has been seen that infections by parasites are more common in the tropical and sub-tropical regions.

Some examples of diseases caused by parasitic infections include malaria, giardia and amoebic dysentery. Parasites also include tapeworms, threadworms and hookworms.


Though antibiotics are effective in treating diseases caused by bacteria, they cannot be said to be a "cure all" or "panacea" for all types of infections. They are only useful in treating infections caused by bacteria and also some types of parasites. Hence, it is clear that antibiotics are not useful in treating infections caused by viruses, yeasts and fungi. This means antibiotics will not have any effect on infections caused by viruses. The good news is that our immune system possesses the ability to cure many of the infections caused by bacteria. In other words, you do not need antibiotics to cure minor bacterial infections such as a throat or ear infection when the individual is in good health.

However, when you are suffering any specific serious bacterial infection it is often necessary that you take antibiotics - for instance pneumonia, meningitis or a kidney infection. In such situations, antibiotics are often considered to be life-saving medicines. When you are ill, your physician will check you thoroughly and say whether you are suffering from any serious ailment. He will also suggest if you need to take antibiotics.

Some possible problems with antibiotics

While antibiotics work well to treat infections by bacteria and sometimes also those by some parasites, they also come with specific potential problems. Hence, it is not always wise to pop in antibiotics suspecting that you may be enduring a bacterial infection. Before taking antibiotics you need to be sure that you actually need to take the medicine because they may cause some side effects. However, they are a necessity when you have a serious bacterial infection.

Antibiotics may cause several adverse side effects, for instance rashes, allergies, nausea and diarrhea. These side effects of taking antibiotics are very common. However, most of the side effects of taking antibiotics are not serious in nature. Nevertheless, there are reports of some people breathing their last owing to severe allergic reactions after taking antibiotics.

Another potential problem with antibiotics is that these medicines can eliminate the beneficial normal "defence" bacteria that survive in our bowel and vagina, protecting us from various infections. When these �beneficial� bacteria are killed or inactivated we may be infected by pathogens more easily. For instance, in the absence of the normal �defence� bacteria we may unknowingly allow development of thrush.

At the same time, excessive use of antibiotics is also harmful for this may lead to some mutation in some bacteria, thereby becoming resistant to a number of antibiotics. As a result, these antibiotics will not work when you might require them very much. For instance, metacillin-resistant Staphylococcus aureus (also known as MRSA) is one bacterium that has over a period of time become resistant to various antibiotics and, therefore, it is extremely difficult to treat infections caused by this bacterium. There are more such examples. A number of bacteria turn out chemicals known as enzymes like extended-spectrum beta-lactamases (ESBLs). These enzymes also make the bacteria further resistant to several antibiotics. The more you use antibiotics, the problem of antibiotic resistance becomes greater.

However, if your doctor prescribes antibiotics to treat any bacterial infection, it is vital that you take the medicines as your physician has directed in the prescription and also to take the complete course of the treatment. Often this means that you should continue taking the antibiotics as your physician has directed till the time you feel better. Your inability to complete a course of treatment with antibiotics or your failure to take the medicines as directed by your physician can, in fact, lead to the development of resistant antibiotics. In other words, the antibiotics prescribed by your physician will not work on you when you take them next.

In addition, a number of antibiotics may also interact with other medicines that you may be taking already. When this happens you may suffer from reactions or the effectiveness of one treatment may be reduced. Hence, before your physician prescribes antibiotics for your condition, you ought to tell them about your medical history and all the medications you are already taking to treat some other health condition.