Microorganisms
Microorganisms are divided into several groups: bacteria, mycoplasms, viruses, fungi, protozoa, and rickettsia. Bacteria are classified according to their shape, such as cocci, bacilli, and spirilla. They are also classified into two groups that depend upon their capacity to be stained. This staining process is called Gram staining. It involves sequential procedures using crystal violet and iodine solutions followed by alcohol that allow rapid identification of organisms as Gram-positive or Gram-negative types. Gram stains can identify specific types of bacteria. Gram-negative microorganisms stain red or rose pink . Gram-positive microorganisms stain blue or purple . Fungi may also be identified by Gram staining. The culture and sensitivity tests can determine which antibiotics should be prescribed.