GENERAL CONSIDERATION OF ANTIBIOTICS

The agents of human infection belong to five major groups.

1. Bacteria

2. Fungi

3. Protozoa

4. Helminthes

5. Viruses

The first three groups are members of kingdom Protista, one of the primary biologic subdivisions along with plants and animals. The protista are distinguished from plants and animals by being either unicellular or relatively simple multicellular. Helminthes are complex multi cellular organisms, which are classified as Metazoa with in animal kingdom. Helminthes and protozoa, they are commonly called parasite. Viruses are not cells but they can replicate within cells.

Cellular organisms differ from viruses as under:

1. STRUCTURE:

Cells possess nucleus or nuclei containing DNA surrounded by cytoplasm. With in cytoplasm protein are produced and synthesized and energy is produced. On the other hand viruses have an inner core of genetic material either DNA or RNA surrounded by protein coat known as “Capsid” that is made up of sub units known as capsomers. Viruses don’t contain cytoplasm and hence they depend on host cells for protein synthesis and energy generation.

2. METHOD OF REPLICATION:

Cellular organisms or cell replicate by Binary fission in which one parent cell divide into two progeny cell retaining its cellular structure

In contrast, viruses disassemble to produce many copies of their nucleic acid and protein and then reassemble into multiple progeny viruses. Viruses must replicate inside the cells.

3. NATURE OF NUCLEIC ACID:

Cells contain both DNA and RNA where viruses contain either DNA or RNA.

Cells are evolved into 2 fundamentally different types.

1. Eukaryotic cells

2. Prokaryotic cells

Fungi and protozoa are Eukaryotic where as bacteria are prokaryotic.

Eukaryotic cells have the true nucleus with multiple chromosomes surrounded by a nuclear membrane and uses mitotic apparatus to ensure equal allocation of chromosomes to progeny cells. The nuclide of prokaryotic cells consists of a single, circular molecule of loosely organized DNA lacking the nuclear membrane and mitotic apparatus.

Eukaryotic cells contain organelles like mitochondria, lysosomes and larger ribosome’s (80S) where as prokaryotes contain no organelles and possess smaller ribosome (70S).

Most prokaryotes contain a rigid cell wall that contains peptidoglycan, a polymer of amino acid and sugar as its unique structural unit. On the other hand Eukaryotes don’t contain peptidoglycan.

Eukaryotic cell membrane contains sterols whereas no prokaryotes have sterols in membranes.