Antibacterial Chemotherapy refers to the use of any chemical or drug for the treatment of bacterial diseases. It is the part of antimicrobial chemotherapy.
Antimicrobial chemotherapy can be divided into several branches on the basis of type of pathogen, for e.g.
For bacterial pathogen – Antibacterial Chemotherapy
For viral pathogen – Antiviral Chemotherapy
For fungal pathogen – Antifungal Chemotherapy, etc

Chemotherapy may either mean involvement of any drug that fight against any cancerous cell or it may involve the use of any antimicrobial drug to cure diseases caused by infectious microorganisms or pathogens.
Antimicrobial drugs work by different mechanisms for different type of organisms. The overall mechanism by which any antimicrobial drug functions is by interfering with the structure and/or function of microorganisms. They either directly kill microbial cell or function by inhibiting their growth.

The development of chemotherapy has been known to begin with the successful research of a German physician, Paul Ehrlich (1854-1915).
Ehrlich was always fascinated to learn more about the dyes that bind to and stain the microbial cells. He was sure and stated that one of the dyes could be used as a chemical that would selectively destroy or kill the infectious pathogen inside the human body without making any harm to human cell and he named it “Magic Bullet”. Working more on this, he was able to find that the dye, trypsan red was active against the trypanosome that causes African Sleeping Sickness. Later, Ehrlich with his assistant Sahachiro Hata tested a variety of arsenic-based chemicals on Syphilis-infected rabbits and was successful in finding that Arsphenamine (an arsenic based chemical compound) was active against the Syphilis spirochete which was then made available in the market.
The other German scientist, Domagk in 1927 found the another Magic Bullet to treat diseases. He observed the antimicrobial activity of a synthetic dye, Prontosil Red which was able to cure Streptococcal and Staphylococcal infections with very limited toxicity. Sulfanilamide (one of the active breakdown products of prontosil in body) was the first synthetic antimicrobial drug.

A Synthetic Antimicrobial is a drug that is developed from any type of a chemical compound that is not found in nature.

Penicillin was the first naturally synthesized antibiotic which was initially discovered by a 21 years old French medical student. No one remembered his work until Alexander Fleming in September 1928 accidently rediscovered the antibiotic. The petri plate of Staphylococcus which was inoculated by Fleming was found to develop certain molds which made the clear zone of inhibition of staph-bacterial species around them. It was meant that the mold infected the petri plates even before the bacteria were inoculated. Fleming suggested that the mold (probably the strain of Penicillium notatum) produced a substance which inhibited the bacterial growth surrounding it and hence had an antibacterial property.
Further experiment results concluded that Penicillin was active against streptococci, meningococci and Corynebacterium diphtheriae, which is the causative agent of diphtheria.
The isolation, mass production and purification of penicillin were accomplished by Howard Florey and Ernst Chain for which they got the nobel prize. They found that the penicillin once pured was effectively able to show antimicrobial properties against streptococcal infection in mice.
Later, Dorothy Hodgkin observed and analyzed the structure of various naturally synthesized products using X-rays. Because of her observation on the chemical structure of naturally synthesized penicillin, it was easier for many scientists to produce a variety of semi synthetic penicillin.

A semisynthetic antimicrobial is defined as the chemically modified product of a natural antibiotic.

After the discovery of penicillin, other scientists got the determination for the discovery of more antibiotics by natural or chemical synthesis.
Selman Waksman developed a new antibiotic, Streptomycin which was produced by the actinomycete, Streptomyces griseus. This antibiotic was discovered by the soil microorganisms, particularly bacteria and fungi. It was the first discovery of antibiotic- producing soil microorganism. It was found that streptomycin was successful in treating tuberculosis.
Other microorganisms producing chloramphenicol, neomycin, terramycin and tetracycline were also isolated later.