- Abbe, Ernst (1840–1905)
- Acne, Microbial Basis of
- Acridine Orange
- Actinomyces
- Adenoviruses
- Adjuvant
- Aerobes
- Agar and Agarose
- Agar Diffusion
- AIDS
- AIDS, Recent Advances in Research and Treatment
- Alexander, Hattie Elizabeth (1901-1968)
- Allergies
- Amebic Dysentery
- American Type Culture Collection
- Ames, Bruce N. (1928- )
- Amino Acid Chemistry
- Anaerobes and Anaerobic Infections
- Anaphylaxis
- Animal Models of Infection
- Anthrax
- Anthrax, Terrorist Use as a Biological Weapon
- Anti-Adhesion Methods
- Antibiotic Resistance, Tests for
- Antibiotics
- Antibody and Antigen
- Antibody Formation and Kinetics
- Antibody, Monoclonal
- Antibody-Antigen, Biochemical and Molecular Reactions
- Antigenic Mimicry
