Bacteria can be defined as creatures consisting of only one cell. They are alive but very small. As bacteria need to receive energy, they can live on products or emit toxins. In contrast to bacteria, viruses are much smaller and cannot be called as "living" in the common sense of the word. Under the microscope bacteria look like rods, spirals or balls. Life on the Earth would be impossible without these tiny organisms. The previous century is remarkable for the fact that we learnt the ways different microbes work and the ways it is possible to cure bacterial diseases. Moreover, the discovery of antibiotics for the treatment of a number of bacterial diseases can be called a real breakthrough in the medical history. Nevertheless, doctors often prescribe antibiotics for a number of conditions that do not require that kind of treatment. Very often it happens under the pressure of the patients who ask to prescribe antibiotics for their viral infections. Unfortunately, patients do not know that antibiotics cannot fight viruses. As a rule, doctors send the patients with such common viral infections as flu and cold to the drugstore with prescriptions for antibiotics. Recently, it has become impossible to fight bacterial diseases with the help of antibiotics. It happened because antibiotics were often prescribed inappropriately and bacteria have become completely resistant to the drugs. The resistance is called drug or antimicrobial resistance. It is a real problem today, especially in hospitals. It is necessary to mention that bacteria are very quick to multiply. For this reason, the bacteria that are not killed by antibiotics can rapidly outnumber those bacteria that can still be destroyed by the same drugs. Diphtheria and brucellosis are the representatives of bacterial diseases. Diphtheria is classified as an infectious respiratory disease. As a rule it affects tonsils, a nose, skin and throat. It has some common features with tetanus, for example it is caused by toxins, bacteria or poisons, but in contrast to tetanus, diphtheria can be passed from the infected person to others through sneezing. As for the symptoms of diphtheria, they can differ from patient to patient. It is the doctor who should define whether they are the symptoms of diphtheria or not. The most common symptoms of diphtheria are as follows: increased pulse, sore throat, low-grade fever, as well as throat obstruction, difficulty swallowing, difficulty breathing, arrhythmia, muscle paralysis, neck swelling, extreme weakness, high fever, heart failure and others. As for cutaneous diphtheria, it has the following symptoms: infected skin lesions, red skin rash, painful skin and swollen skin. One of the bacterial diseases is brucellosis. It is not a common disease for the United States. Nevertheless, it is common for those countries where the program controlling animal diseases has not reduced the amount of infected animals. Areas indicated as risky zones are those of the Mediterranean Basin (Spain, Italy, Turkey, Portugal, southern France, Greece, and North Africa), Eastern Europe, Africa, the Middle East, Central and South America, Asia and the Caribbean.