It is important to know how bacterial and viral infections differ. They have a different approach to their treatment. Antibiotics do not work on viruses, so there is no point in prescribing them for ARVI, but for a bacterial infection, it is necessary.

The human body is susceptible to a variety of diseases, and most of them are infectious. And such diseases can be bacterial or viral in nature. It is important to immediately determine which pathogen is causing the disease in order to choose the right treatment. But for this you need to know how to distinguish a viral infection from a bacterial one. In fact, there are differences, knowing which, you can fairly easily determine the type of pathogen.

Viruses are non-cellular organisms that need to invade a living cell in order to reproduce. There are a huge number of viruses that cause various pathologies, but the most common are those that provoke the development of so-called colds. Scientists count more than 30,000 such microbial agents, of which the influenza virus is the best known. As for the rest, they all cause SARS.

Even before going to a doctor, it is useful to know how to determine that a child or an adult has ARVI. There are many signs that indicate viral origin inflammation:

• short incubation period, up to 5 days;
• body aches even at low-grade fever;
• temperature rise above 38 degrees;
• intense fever;
• severe symptoms of intoxication (headache, weakness, drowsiness);
• cough;
• nasal congestion;
• severe redness of the mucous membranes (in some cases);
• possible loose stools, vomiting;
• sometimes a rash on the skin;
• the duration of the viral infection is up to 10 days.

Of course, all the symptoms listed above do not necessarily appear in every case, since different groups of viruses cause diseases with different symptoms. Some provoke an increase in temperature up to 40 degrees, intoxication, but without a runny nose and cough, although a redness of the throat is visible on examination. Others cause a severe runny nose, but low-grade fever without marked weakness or headache. In addition, a viral infection can have both acute and unexpressed onset. Much also depends on the "specialization" of the virus: some types cause a runny nose, others - inflammation of the pharyngeal walls, and so on. But a characteristic feature of each such disease is that it lasts no more than 10 days, and from about 4-5 days the symptoms begin to decrease.

Signs of a bacterial infection

To have an idea of ​​how to distinguish a viral infection from a bacterial one, it is important to know the features of the pathogenesis of both types of diseases. The following symptoms are characteristic of the bacterial:

• incubation period from 2 to 12 days;
• pain is localized only at the site of the lesion;
• low-grade fever (while the inflammation is not strongly developed);
• severe redness of the mucous membranes (only with severe inflammation);
• the formation of purulent abscesses;
• purulent discharge;
• plaque in the throat is white-yellow;
• intoxication (lethargy, fatigue, headache);
• apathy;
• decreased or complete lack of appetite;
• exacerbation of migraine;
• the illness lasts more than 10-12 days.

In addition to this symptom complex, a characteristic feature of bacterial infections is that they do not go away on their own, and without treatment, the symptoms only worsen.

That is, if ARVI can pass without specific treatment, it is enough to adhere to the correct regimen, take general strengthening agents, vitamins, then bacterial inflammation will progress until antibiotics are taken.

This is the main difference when it comes to colds.

Diagnostics

On the other hand, doctors often face the question of how to distinguish a bacterial infection from a viral one, based not only on symptoms. For this, laboratory tests are carried out, first of all, a general blood test is done. According to its results, one can understand whether the disease was caused by a viral or bacterial infection.

A complete blood count reflects indicators such as the number of erythrocytes, platelets, hemoglobin, leukocytes. The study determines the leukocyte formula, the erythrocyte sedimentation rate. Depending on these indicators, the type of infection is determined.

For diagnosis, the most important values ​​are the total number of leukocytes, leukocyte formula (the ratio of several types of leukocytes) and ESR.

Leukocytes are those blood cells that provide protection for the body, their main function is to absorb foreign particles and pathogens. There are several types of leukocytes:

As for the erythrocyte sedimentation rate, it changes depending on the state of the body. Normally, ESR in women is from 2 to 20 mm / h, in men - from 2 to 15 mm / h, in children under 12 years of age - from 4 to 17 mm / h.

Blood test for ARVI

If the disease is caused by a virus, the results of the study will be as follows:

• the number of leukocytes is normal or slightly below normal;
• an increased number of lymphocytes and monocytes;
• a decrease in the level of neutrophils;
• ESR is slightly reduced or normal.

Blood test for bacterial infection

In cases where various pathogenic bacilli and cocci have become the cause of the disease, the study reveals the following clinical picture:

Not everyone can understand what metamyelocytes and myelocytes are. These are also blood elements that are normally not detected during analysis, since they are contained in the bone marrow. But if there are problems with hematopoiesis, such cells can be detected. Their appearance speaks of a severe inflammatory process.

The importance of differential diagnosis

It is important to know how a bacterial and viral infection differs, since the whole point is in a different approach to their treatment.

Everyone knows that antibiotic therapy does not work on viruses, so there is no point in prescribing antibiotics for ARVI.

Rather, they will only harm - after all, such drugs destroy not only pathogenic, but also beneficial microorganisms, which partially form immunity. But with a bacterial infection, the appointment of antibiotics is mandatory, otherwise the body will not cope with the disease, and it will at least turn into a chronic form.

This is what diseases are distinguished by. However, despite the differences, sometimes the same therapy is prescribed for bacterial and viral infections. As a rule, this approach is practiced in pediatrics: even with an obvious viral infection, antibiotics are prescribed. The reason is simple: children's immunity is still weak, and a bacterial infection joins the virus in almost all cases, so the prescription of antibiotics is quite justified.

Viruses and bacteria are tiny objects that can only be seen using a powerful microscope. Viruses and bacteria can be found anywhere on the planet, and they both play an important role in evolution. Both bacteria and viruses can cause disease in plants, animals and humans. How are they different? Having studied them more thoroughly, we can conclude that they have something in common, but also a lot of differences.

Some information about viruses

Viruses are microscopic objects, a characteristic feature of which is that their life cycle can only take place inside a living cell. Outside of a living organism, viruses show no signs of life.

A virus outside a living cell is called a virioome. The sizes of virions vary widely - from 15 to 400 nm.

Virus structure

A virus just made consists of capsid- the protein coat that protects the genetic material of the virus - its nucleic acid (genome). According to the classification of viruses, created by the Nobel Prize in Physiology or Medicine David Baltimore, there are seven possible options viral genome:

1. Double-stranded DNA viruses.
2. Single-stranded DNA viruses.
3. RNA viruses, the genetic material of which is replicated in the cytoplasm.
4. Viruses with a positive single-stranded RNA (RNA (+)).
5. Viruses with negative single-stranded RNA (RNA (-)).
6. Single-stranded RNA (+) viruses that use a special enzyme for replication - reverse transcriptase, which allows DNA to be synthesized on an RNA template.
7. Double-stranded DNA viruses that use single-stranded RNA in the process of realizing genetic material.

The fact that RNA is capable of storing genetic information is a unique property inherent only in viruses.

More complex viruses include an additional shell - supercapsid... Spiny processes formed from lipo- or glycoproteins can often be observed on the surface of the supercapsid. These processes have the property of causing agglutination (gluing) of erythrocytes when they fall into the blood, bind to receptors on the surface of a vulnerable cell, and, subsequently, destroy its walls.

Once inside the cells and having lost unnecessary protective membranes, the virus begins to realize its genetic material - to synthesize viral proteins and replicate the genome. The viral genome can integrate into the chromosome of the affected cell by recombination, and then, when the cell divides, the genome of the virus will double. Plant viruses have the ability to move from one cell to another.

Overview of bacteria

Bacteria are microorganisms, usually unicellular, without a formed cell nucleus. A special branch of microbiology, bacteriology, is engaged in the study of bacteria. The size of bacteria can vary widely - from 0.15 to 50 microns.

There are always three structures in any bacteria:

1. Cytoplasmic membrane.
2. Ribosomes - Organelles Needed for Protein Synthesis
3. A nucleotide used to store the genetic material of a bacterium. It is presented in the form of one chromosome - a DNA molecule.

A cell wall is present on the surface of the cytoplasmic membrane, and an additional capsule is often located on top of it. The capsule and cell wall form the cell wall. The ribosomes and nucleotide of bacteria are located in the cytoplasm. The cytoplasmic membrane together with the cytoplasm is usually called protoplast.

Some bacteria have flagella that enable them to move through liquid and viscous media. Many have villi on the cell wall, which, according to many researchers, simplifies the process of bacterial attachment to the cell.

Reproduction of bacteria

Most bacteria reproduce by binary fission. It is a process in which two identical daughter cells are formed from one original cell. In the same process, DNA is replicated.

Some bacteria are characterized by sexual process, as a result of which a daughter cell is formed from two parental cells with non-identical genetic material, with a set of genes from both original cells. The resulting cell (bacterium) is called a recombinant.

What do viruses and bacteria have in common?

1. Both viruses and bacteria can be found anywhere on earth, in any habitat.
2. Both of them cause disease in humans, animals and plants. Many of them are deadly.
3. Viruses and bacteria are used in microbiological research.
4. The genetic material of viruses with double-stranded DNA and bacteria is presented in the same way.

The main differences between viruses and bacteria

1. Dimensions. Viruses are about 1000 times smaller than bacteria.
2. Structure. The structure of viruses differs from the structure of cells of all living organisms, including bacteria
3. Replication (reproduction). The virus does not replicate outside of a living cell, while bacteria can multiply in any environment.
4. Genetic material. The genome of the virus can be represented by both DNA and RNA, single-stranded or double-stranded, while the bacterium is characterized by a genome of double-stranded DNA.
5. Attachment to the cage. Many bacteria are able to bind by villi on the cell wall surface to cell receptors. In virions, this function is performed by spiny processes on the surface of the supercapsid.
6. Viruses can infect bacteria, just like any other living cell, and use them to reproduce their genetic material. In contrast, bacteria cannot infect viruses.

These are microscopic organisms that can cause disease, both in humans and in animals or plants. Although bacteria and viruses can have some General characteristics, they are also very different. Bacteria are usually much larger than viruses and can be viewed with a conventional microscope. Viruses are about 1000 times smaller than bacteria and are visible only under an electron microscope. Bacteria are single-celled organisms that reproduce independently of other organisms. Viruses need live help to reproduce.

Where do they meet?

Bacteria: bacteria live almost anywhere, including in / on other organisms and on inorganic surfaces. Some bacteria are considered and can survive in extremely harsh environments, such as the hydrothermal vents and stomachs of animals or humans.

Viruses: Like bacteria, viruses can be found in almost any environment. They are capable of infecting animals and plants, as well as bacteria and. Viruses that infect extremophiles such as archaea have genetic adaptations that allow them to withstand harsh environmental conditions. Viruses can persist (from a few seconds to several years) on surfaces or objects that we use every day.

Bacterial and viral structure

Bacteria: bacteria are prokaryotic cells that show all the characteristics of living organisms. Bacterial cells contain DNA and are immersed in and surrounded. These organelles perform vital functions that allow bacteria to obtain energy from the environment and reproduce.

Viruses: Viruses are not considered cells, but exist as particles of nucleic acid (DNA or RNA) enclosed in a protein envelope. Also known as virions, viral particles exist somewhere between living and nonliving organisms. Although they contain genetic material, they do not have the cell wall or organelles needed to produce and reproduce energy. Viruses rely solely on the host cell for replication.

Size and shape

Bacteria: Bacteria can occur in a variety of shapes and sizes. Common forms of bacterial cells include cocci (spherical), bacilli (rod-shaped), helix, and vibrios. Bacteria are usually between 200 and 1000 nanometers in size. The largest bacterial cells are visible to the naked eye. The world's largest bacteria are: Thiomargarita namibiensis, reaching up to 750,000 nanometers (0.75 millimeters) in diameter.

Viruses: the size and shape of viruses is determined by the amount of nucleic acid and proteins they contain. Viruses usually have spherical (polyhedral), rod-shaped, or spiral capsids. Some viruses, such as, have complex shapes that involve the addition of a protein attached to the capsid, with tail fibers extending from the tail. Viruses are much smaller than bacteria. They usually range in size from 20 to 400 nm in diameter. The largest known viruses, pandoraviruses, are about 1000 nanometers in diameter.

How are they reproduced?

Bacteria: bacteria usually multiply through a process known as. In this process, one cell replicates and divides into two identical cells. Under the right conditions, bacteria can grow exponentially.

Viruses: unlike bacteria, viruses can only replicate with the help of a host cell. Since viruses do not have the organelles needed to reproduce viral components, they must use the organelles of the host cell for replication. In viral replication, the virus injects its genetic material (DNA or RNA) into the cell. Virals are replicated and contain instructions for creating viral components. As soon as the components are collected, and the newly formed viruses mature, they rupture the cell and proceed to infect other cells.

Diseases caused by bacteria and viruses

Bacteria: while most bacteria are harmless, and some are even beneficial to humans, other bacteria can cause disease. The pathogenic bacteria that cause disease produce toxins that destroy the cells in the body. They can cause food poisoning and other serious illnesses, including meningitis, pneumonia, and tuberculosis. Bacterial infections can be treated with antibiotics, which are very effective at killing bacteria.

However, due to the overuse of antibiotics, bacteria have gained resistance to them. Some of them even became known as superbugs because they gained resistance to many modern antibiotics. Vaccines are also helpful in preventing the spread of bacterial diseases. The best way protecting yourself from bacteria and other germs is the right way to wash your hands often.

Viruses: viruses are those that cause a number of diseases, including chickenpox, flu, rabies, Ebola, Zika, and HIV / AIDS. Viruses are capable of causing persistent infections in which they are dormant and can be reactivated later.

Some viruses cause changes in host cells that lead to the development of cancer. These viruses are known to cause cancers such as liver cancer, cervical cancer, and Burkitt's lymphoma. Antibiotics don't work against viruses. Treatment for viral infections usually involves medications that treat the symptoms of the infection, not the virus itself. Typically, the immune system fights viruses on its own. Vaccines can also be used to prevent certain viral infections.

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All of us in biology lessons at school were told what bacteria and viruses are and how they differ. However, the majority of them retained only vague memories: “this is something infectious” and “some kind of infection”.

Equally profound knowledge is demonstrated by some journalists, on whose conscience "tuberculosis viruses", "influenza bacteria", "antiviral antibiotics" and other non-existent things.

feel the difference

Microbes is the collective name for all microscopic organisms, without taking into account their structure and life.

Structure

Bacteria Are real cells. They have everything they need to generate energy, synthesize substances necessary for life, as well as for reproduction. But bacteria do not have a nucleus - the genetic material is located directly in the cytoplasm (intracellular fluid).

Viruses - the most primitive form of life, standing on the border between living and inanimate nature. They consist only of genetic material (DNA or RNA), "packed" in a protein shell.

The origin of the viruses is not fully understood. The currently prevailing hypothesis is that they were once part of the genome of cellular organisms. These parts subsequently "escaped" from the host cells to start living at the expense of other organisms.

Life activity

Viruses

A viral particle is not able to multiply on its own - for this it needs the cells of the host organism. We are not talking about nutrition at all: the virus does not have its own metabolism.

So, the protein coat of the viral particle is attached to the membrane of a foreign cell. Most often, for each virus, this is a cell of a certain type. For example, the influenza virus prefers to attach to the epithelium of the mucous membranes (especially the trachea), the herpes simplex virus to the nervous tissue, and the human immunodeficiency virus to immune cells.

Having attached itself to the cell membrane, the virus "introduces" its genetic material into the host cell. There, viral DNA or RNA "multiplies" with the help of "host" enzyme systems, and on its matrix the cell begins to synthesize viral proteins. From nucleic acids and proteins, new viral particles are assembled and released by destroying the host cell. "Newborn" viruses infect more and more cells, causing the progression of the disease, and are released into the environment, infecting new "hosts".

Bacteria

Bacteria can multiply on their own (most often by dividing) and have their own metabolism. They use the "host" only as a food product and a fertile environment for life and reproduction. At the same time, they damage ("digest") cells and tissues with their enzymes and poison the body with waste products - toxins. All this leads to the development of the disease.

Some bacteria are essential for the normal functioning of the human body - they are called symbiotic flora. Living in the intestines, they are involved in the digestion of food, the production of vitamins and protection against intestinal infections. On the skin, in the mouth and in the vagina, they inhibit the growth of their disease-causing "brothers".

It is being treated

Ignorance of the difference in structure and activity between viruses and bacteria leads to several common misconceptions.

Misconception 1: Viral Infection Can Be Cured With Antibiotics

Actually. This is not true. Antibiotics disrupt the processes of building the cell wall, the synthesis of nucleic acids and protein, or the metabolism of certain substances. Since viruses do not have a cell wall, metabolism and their own synthesis systems, they are resistant to antibiotics. Medicines in this group are used only to treat bacterial infections.

Misconception 2. The virus that caused the disease can be purposefully destroyed

Actually. Not so simple. Even the body's immune forces are unable to "cleanse" the cell from the virus. They can destroy only those viral particles that have already entered the body, but have not yet ended up inside the cell. When the viral genome has penetrated the cell membrane, the only way to combat it is to destroy the entire cell, followed by absorption and digestion of the released viruses by immune cells.

Some viruses, having entered the human body, are in it constantly throughout the entire human life. Such properties are possessed, for example, by herpes viruses, papillomaviruses and HIV. In his life cycle they alternate a phase of active reproduction, which is manifested by an exacerbation of the disease, and a latent, "dormant" phase, when the virus is in the affected cells, not showing itself in any way. In a latent state, the virus is not available either for the immune system or for drugs, therefore, the claims of manufacturers and distributors of "miraculous" dietary supplements about the complete eradication of viruses are deliberately false.

Misconception 3. There is no cure for a viral infection.

Actually. They are. Most antiviral drugs work through one of three mechanisms.

The first is to stimulate the body's own defenses to fight the virus. This is how, for example, "Arbidol" and "Cycloferon" act.

The second is a violation of the structure of new viral particles. Drugs of this kind are altered analogs of nitrogenous bases that serve as material for the synthesis of nucleic acids. Due to their structural similarity, they are incorporated into the DNA or RNA of the virus multiplying in the cells, making new viral particles defective, unable to infect new cells. An example of such a drug is acyclovir, which is used to treat herpes infections.

The third mechanism is to prevent the virus from entering the cell. The drug prevents the viral DNA or RNA from detaching from the protein coat, due to which the genetic material of the virus loses its ability to penetrate the cell membrane. This is how rimantadine works, for example.

All of the above drugs act only on actively multiplying viruses.

In recent years, attempts have been made to generate gene therapy for viral infections, that is, to fight viruses with the help of ... viruses. For this, the genome of a suitable virus (such a virus is called a vector) is modified. First, it is deprived of its disease-causing properties. Secondly, a sequence of genes is added to it, which, when interacting with the genome of the virus targeted for treatment, "turns it off". After that, the vector with the genes is injected into the body of a person suffering from a viral infection. This treatment is still under development and confirmation of its efficacy and safety, but it is hoped that gene therapy for viral infections will become available in the coming years.

In addition, there are viruses that selectively attack bacterial cells. They are called bacteriophages (literally "bacteria eaters"). There have been many attempts to use them to fight bacterial infections, but they have not shown significant advantages over antibiotics. Bacteriophages are used in genetic engineering to deliver the required genetic material to bacterial cells.

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Preparing for your biology exam? Bedridden with the flu and wondering what kinds of microorganisms have made you so sick? While bacteria and viruses can make you sick in similar ways, in fact they are very different organisms with a wide range of distinguishing qualities. Exploring these differences can help you stay on top of any treatments you are taking and give you a better understanding of the complex biology that is going on in you all the time. You will be able to learn how to describe the differences between bacteria and viruses not only by learning the basics about them, but also by examining them through a microscope and discovering more information about their composition and function.

Steps

Part 1

Exploring the Difference

Explore the main differences. There are major differences between bacteria and viruses in size, origin, and effect on the body.

• Viruses are the smallest and most elementary form of life; they are 10 to 100 times smaller than bacteria.
• Bacteria are intercellular organisms (that is, they live between cells), while viruses are intracellular organisms, which implies that they enter the host cell and live inside it. Viruses alter the genetic material of a host cell from its normal function to the production of the virus itself.
• Some bacteria are good, but all viruses are bad.
• Antibiotics cannot kill viruses, but they can kill most bacteria, with the exception of most gram-negative bacteria.

1. Know the differences in reproduction. Viruses must have a living host in order to reproduce, such as a plant or animal. While most bacteria can grow on non-living surfaces.

   • Bacteria have all the "structures" (cell organelles) necessary for their growth and reproduction and, as a rule, do not reproduce sexually.
   • At the same time, viruses usually carry information - for example, DNA or RNA, packaged in a protein and / or membrane envelope. They need the structure of a host cell in order to reproduce. The "legs" of the virus attach to the surface of the cell and the genetic material contained in the virus is injected into the cell. Differently placed viruses do not actually "live", but are, in essence, information (DNA or RNA) and float around until they encounter a suitable host.

2. Determine if the microbe has a beneficial effect on our body. While it may seem difficult to understand, many, many tiny microorganisms live within (but separate from) our body. In fact, in terms of pure cell count, most people are roughly 90% of microbial life and only 10% of human cells. Many bacteria coexist peacefully with our organs; some even perform very important tasks, such as producing vitamins, recycling waste, and generating oxygen.

   Check if the body meets the criteria for life. While there is no precise, formal definition of what life is made of, scientists agree that bacteria are undoubtedly alive. On the other hand, viruses seem to be on the brink between life and death. For example, viruses have some characteristics of life, such as genetic material, evolve over time as a result of natural selection, and they have the ability to reproduce by making multiple copies of themselves. However, viruses do not have a cellular structure or their own metabolism; they need a host cell to reproduce. At the same time, viruses are mostly inanimate. Consider the following:

   Know the bacterial and viral causes of common diseases. If you are suffering from a disease and you know what it is, finding out if you are currently suffering from bacteria or viruses can be as simple as looking for information about your disease. Common diseases caused by bacteria and viruses include:

3. Biological differences between bacteria and viruses

   Organism	The size	Structure	Breeding method	Treatment	Alive?
   Bacteria	Large (about 1000 nanometers)	One cell: peptidoglycan / polysaccharide wall; cell membrane; ribosomes; free floating DNA / RNA	Not sexually. Copies DNA and multiplies by cell division (splitting).	Antibiotics; antibacterial agents for external sterilization	Yes
   Viruses	Small (20-400 nanometers)	Cell-free: simple protein structure; without walls and shell; no ribosomes, DNA / RNA embedded in the protein coat	Hijacks the host cell, forcing it to make copies of viral DNA / RNA; new viruses leave the host cell.	Treatment is unknown. Vaccination can prevent disease; symptoms are treatable.	Unknown; does not meet traditional living standards.

   Part 2

   Analyzing microscopic features

   Look for the presence of a cell. Structurally, bacteria are more complex than viruses. The bacteria are known as unicellular... This means that each bacterium consists of only one cell. At the same time, the human body contains many trillions of cells.

   We check the size of the organism. One of the most quick ways to distinguish bacteria from viruses is to compare their sizes. In almost 100% of cases, bacteria are larger than viruses. In essence, the biggest viruses exactly as big as the smallest bacteria.

   Checking for ribosomes (and no other organelles.) Although bacteria have cells, they are not complex. Bacteria do not have a nucleus and organelles, with the exception of ribosomes.

   Observation of the reproductive cycle of the body. Bacteria and viruses are not like most animals. They do not need to have sexual intercourse or exchange genetic information with other organisms of the same type in order to reproduce. However, it cannot be said that bacteria and viruses have the same reproductive strategies.