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What Are the Dangers of Gram Negative Bacteria?

There are many ways to divide life forms into different groups based upon their characteristics. Gram-positive and Gram-negative bacteria are two broad divisions of all bacteria, with the major difference between the two lying in the structure of their cell membranes. While both types can cause infectious diseases, Gram-negative bacteria are a major concern to public health because their cell structure makes them resistant to antibiotics.

  1. Gram Stain

    • The Gram stain is a way of dividing bacteria into the two major groups. Gram-positive bacteria retain the dye crystal violet during the staining process, turning purple, whereas Gram-negative bacteria become pink during the process. Some bacteria are variable, and Gram-positive bacteria can become Gram-negative bacteria under certain circumstances. The difference between the two lies in their cell membranes. Gram-positive bacteria have a thick cell wall that is mostly made of peptidoglycan. The peptidoglycan layer in Gram-negative bacteria is very thin, and their outermost layer is protected by a membrane of lipoprotein molecules. This means that the two types of cells have very different properties and respond differently to chemicals.

    Antibiotic Resistance

    • The main danger of Gram-negative bacteria is that Gram-negative bacterial infections do not respond to standard antibiotic treatment. For instance, Gram-negative bacteria resist the effects of penicillin and cephalosporin because these antibiotics work by disrupting cell walls, which Gram-negative bacteria lack. The outer membrane of Gram-negative bacteria resists the effects of many types of antibiotics because it is impermeable to the antibiotic. This means that infections caused by Gram-negative bacteria are very difficult to treat.

    Hospital Infections

    • Infections caused by Gram-negative bacteria are often contracted in hospital settings and are a major cause for hospital-related infection and death. Patients with weakened immune systems are particularly susceptible, although patients with stronger immune systems can and do acquire these types of infections. These bacteria survive for a long time on surfaces and are often contracted through catheters, ventilators or wounds. Once inside the body, Gram-negative bacteria typically invade the bloodstream, causing infection. Gram-negative bacteria are often involved in urinary infections and ventilator-assisted pneumonia.

    Treatment

    • Because Gram-negative bacteria are so resistant to antibiotics, treatment can be difficult or impossible. There are two antibiotics that were developed in the 1940s, colistin and polymyxin B, which both are capable of treating infection from Gram-negative bacteria. However, both drugs have severe side effects, such as nerve and kidney damage. Treatment with these drugs can lead to kidney failure. Some strains of Gram-negative bacteria are also resistant to these antibiotics.

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