Download Grouping bacteria by Gram status

Grouping bacteria
by Gram status
Bacteria can be divided into two main groups according to the external structure of the bacterial cell: Grampositive and Gram-negative.1 A simple technique called Gram staining identifies Gram-positive bacteria as dark
purple and Gram-negative bacteria as pink.2
Gram-positive
• Clostridium difficile
• Staphylococcus aureus
Cell wall
Provides the cell with its structure
and helps it tolerate adverse
conditions. The cell wall is made up
of peptidoglycan, a complex mesh
of sugars and amino acids.1,3
• Enterococcus spp.
• Streptococcus pneumonia
Cell membrane
Controls what goes in and out of
the bacteria. The inner membrane is
also where bacteria generate their
energy supply.1
Gram-negative
• Klebsiella pneumoniae
• Escherichia coli
• Neisseria gonorrhoeae
Cytoplasm
Gel-like substance that contains
nutrients essential to the functioning
of bacteria.1
• Acinetobacter
• Pseudomonas aeruginosa
• Haemophilus influenzae
Plasmid
Contains the genetic blueprint of
the bacteria.1
Studded with protein pores
that can expel antibiotics
from the bacteria4
Thick cell wall2,3
No outer membrane2,3
Thin cell wall2,3
Loose outer wall means many
substances, including antibiotics,
diffuse easily in and out of the cell2
Gram status and
resistance
Outer membrane that can
prevent antibiotics from
entering the bacteria5
Antibiotic resistance is a lethal and growing problem. Differences between Gram-positive and Gram-negative
bacterial cell walls result in varying susceptibility to the different types of antibiotics.2,5,6
Gram-negative bacteria are generally more dangerous than Gram-positive bacteria. They have developed
resistance against nearly all available antibiotic options. They are able to share their genetic material, allowing
this resistance to spread more broadly and quickly.6
There is an urgent need to find new antibiotics, especially against Gram-negative bacteria.
References
1.
2.
3.
4.
5.
6.
Phillips J, et al. The Biology of Disease. 2nd ed. Blackwell Publishing, Oxford, UK: 2001.
Medical Microbiology. Available at: http://www.ncbi.nlm.nih.gov/books/NBK7986/#A698. Last accessed March 2016.
Gould JL, Keeton WT. Biological Science. Volume 2. 6th ed. W.W. Norton & Company, London, UK: 1996.
Murakami S, et al. Nature 2006;443:173–9.
Rang HP, et al. Pharmacology. 5th ed. Churchill Livingstone, London, UK: 2003.
Centers for Disease Control and Prevention. Available at: http://www.cdc.gov/drugresistance/pdf/ar-threats-2013-508.pdf. Last accessed March 2016.