Classification of Medically Important Bacteria
By Dr. Umair Khan (MBBS)
Bacteria are classified in a number of ways, including by their shape, Gram staining, oxygen requirements, and metabolic pathways.
Shape
Bacteria can be classified as cocci (spheres), bacilli (rods), or spirilla (spirals).
Gram staining
Bacteria can be classified as Gram-positive or Gram-negative. Gram-positive bacteria have a thick cell wall that makes them more resistant to antibiotics. Gram-negative bacteria have a thinner cell wall and are more susceptible to antibiotics.
Oxygen requirements
Bacteria can be classified as aerobic, anaerobic, or facultative anaerobes. Aerobic bacteria require oxygen to grow. Anaerobic bacteria do not require oxygen and can actually be harmed by it. Facultative anaerobes can grow with or without oxygen.
Metabolic pathways
Bacteria can be classified as chemoorganotrophic or chemolithotrophic. Chemoorganotrophic bacteria obtain energy by breaking down organic compounds. Chemolithotrophic bacteria obtain energy by breaking down inorganic compounds.
Medically important bacteria
There are many different types of bacteria that can cause disease in humans. Some of the most common medically important bacteria include:
Staphylococcus aureus: This bacterium is a Gram-positive coccus that is often found on the skin and in the nose. It can cause a variety of infections, including skin infections, pneumonia, and sepsis.
Streptococcus pneumoniae: This bacterium is a Gram-positive coccus that is a common cause of pneumonia, meningitis, and ear infections.
Haemophilus influenzae: This bacterium is a Gram-negative bacillus that is a common cause of meningitis, pneumonia, and ear infections in children.
Neisseria meningitidis: This bacterium is a Gram-negative diplococcus that is a common cause of meningitis.
Escherichia coli: This bacterium is a Gram-negative rod that is a common inhabitant of the intestines. However, some strains of E. coli can cause food poisoning, urinary tract infections, and other infections.
Salmonella: This bacterium is a Gram-negative bacillus that is a common cause of food poisoning.
Pseudomonas aeruginosa: This bacterium is a Gram-negative rod that is a common cause of infections in hospitals.
Mycobacterium tuberculosis: This bacterium is a Gram-positive rod that is the cause of tuberculosis.
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Bacteriology
Study of Bacteria
Microbiology
Study of Microorganisms
