What is Gram-Positive Bacteria?
It’s important to understand the difference between two types of bacteria: gram-positive and gram-negative. The names come from a special coloring test that was developed in 1884 by Hans Christian Gram.
Gram-positive bacteria are named this way because they turn blue when treated with a special dye called crystal violet. This happens because they have a thick layer on their cell wall, made of a substance called peptidoglycan, which holds onto the dye. When viewed under a microscope, these bacteria appear blue.
On the other hand, gram-negative bacteria have a thinner peptidoglycan layer and an additional outer membrane. Because their peptidoglycan layer is thinner, it doesn’t hold onto the blue dye used in the staining process.
Besides the color they turn with the dye, bacteria can also be identified by their shape. Gram-positive bacteria can be circular (cocci), rod-shaped (bacilli), or have a branching filament shape.
What Causes Gram-Positive Bacteria?
There are different types of bacteria known as ‘Gram-positive cocci’. These include two types, ‘Staphylococcus’, which tends to grow in clusters, and ‘Streptococcus’, which usually forms chains. These bacteria can be identified based on their reaction to a substance called catalase. Staphylococcus is catalase-positive, while Streptococcus is catalase-negative. Staphylococcus can be divided further into coagulase-positive (S. aureus) and coagulase-negative (S. epidermidis and S. saprophyticus) species.
Streptococcus bacteria can also be divided up into different groups, which include Strep. pyogenes (Group A), Strep. agalactiae (Group B), enterococci (Group D), Strep viridans, and Strep pneumonia.
Another type of Gram-positive bacteria, called ‘bacilli’, differ based on their ability to produce spores, which are resilient structures that allow certain bacteria to weather harsh conditions. For example, Bacillus and Clostridia are types of rods that can form spores, whereas Listeria and Corynebacterium cannot. Bacteria that can produce spores can survive in their environment for many years.
There are also types of rods known as Nocardia and Actinomyces, which are bacteria that grow in branching, thread-like structures.
Gram-positive bacteria have a thicker wall made of a substance called ‘peptidoglycan’ compared to Gram-negative bacteria. This is a thick polymer that is around 20 to 80 nanometres thick, while the peptidoglycan layer of the Gram-negative bacteria’s wall is only 2 to 3 nanometres thick and is covered with a layer of fat-like substance called an ‘outer lipid bilayer’ membrane.
Risk Factors and Frequency for Gram-Positive Bacteria
Deaths from bloodstream infections have risen by 78% in just twenty years. These infections are often caused by certain bacteria, called gram-positive organisms, that can grow in different ways and resist treatments. A study found that in people with an existing serious illness, these particular bacteria were responsible for 62% of all bloodstream infections in 1995 and increased to 76% in 2000. On the other hand, infections caused by gram-negative organisms dropped from 22% to 14% during these years.
Signs and Symptoms of Gram-Positive Bacteria
Recognizing patients with sepsis and completing needed blood tests is crucial.
The physical signs to look out for can include:
- Blisters from impetigo, a skin infection
- Leaking wounds or sores
- Redness on the skin
- Fever
- A heart murmur, which might indicate endocarditis (an infection of the heart’s inner lining)
- Pinpoint, round spots that appear on the skin if toxic shock syndrome is present
- Surface-level pockets of pus
- Heat sensation from the affected area
Testing for Gram-Positive Bacteria
If your doctor thinks you might have an infection from a certain type of bacteria (known as gram-positive bacteria), they will likely order several tests. These are meant to help confirm the infection and gain a better understanding of your overall health. Here are the tests you might expect:
The first is a Complete Blood Count (CBC). This is a common test that can give your doctor a lot of information about the cells in your blood, such as the number of red and white blood cells and the level of hemoglobin, a protein that carries oxygen.
They might also want to check your electrolytes. These are minerals like sodium, potassium, and calcium that are vital to many bodily functions, like maintaining your heart rhythm or keeping you hydrated.
A blood culture test allows your doctor to check for bacteria or yeast in your blood. This test involves taking a blood sample from a vein in your arm.
The pro-calcitonin level test checks the level of a specific protein in your blood. If this protein is high, it can be a sign that there is a serious bacterial infection in the body.
If they suspect you may have endocarditis, an infection of the inner lining of your heart, your doctor may order an echocardiogram. This is an ultrasound of your heart that can provide an image of its structure and function.
Finally, if your doctor suspects a septic joint, which is an infection in a joint such as in the knee or hip, they may perform a joint aspiration. This procedure involves using a needle to take a sample of fluid from the joint for testing.
Treatment Options for Gram-Positive Bacteria
Penicillin, the first antibiotic ever, was introduced in 1928 by Alexander Fleming during World War II. Penicillin is primarily used to treat infections caused by streptococcal bacteria. However, it’s not effective against Staph or Enterococcus bacteria.
For dealing with infections caused by Staph (MSSA) and Strep bacteria, we have another group of antibiotics, like nafcillin, oxacillin, cloxacillin, and dicloxacillin. These antibiotics are resistant to the enzyme penicillinase, which some bacteria produce to fend off penicillin.
The antibiotics piperacillin and ticarcillin are known as anti-pseudomonal penicillins and are effective against a broad range of bacteria. This includes gram-positive, gram-negative, pseudomonas, and anaerobes which are bacteria that don’t need oxygen to grow. In addition, Carbapenems are another group of antibiotics that also cover a wide spectrum of bacteria, including gram-positives, gram negatives, and anaerobes.
For more serious infections such as those caused by MRSA (a type of staph bacteria that’s resistant to many antibiotics), other antibiotics like Trimethoprim/sulfamethoxazole, clindamycin, and doxycycline are commonly used.
Vancomycin, linezolid, daptomycin, and tigecycline are among the options for treating moderate to severe community and hospital-acquired MRSA. If a patient is allergic to vancomycin, linezolid is an alternative. However, if linezolid is used, it’s important to perform weekly blood tests because it may affect bone marrow causing decreased formation of new blood cells (neutropenia, thrombocytopenia, and anemia). These antibiotics, along with tigecycline, can also be used in cases of vancomycin-resistant enterococci.
Please note that different bacteria cause different infections, and the medication suitable for each infection depends on many factors, such as the patient’s overall health, allergies, and the bacteria’s resistance patterns. The physician will consider all these factors when deciding the most suitable antibiotic.
What else can Gram-Positive Bacteria be?
The following topics are examples of different medical conditions and procedures that doctors need to know about:
- Bacteremia (blood infection)
- Bronchiectasis imaging (procedure to visualize lung damage)
- Chemical burns
- Diarrhea
- Electrical injuries in emergency medicine
- Emergent management of acute otitis (immediate treatment of ear infection)
- Emergent management of thermal burns (immediate treatment of heat burns)
- Empyema imaging (procedure to visualize collection of pus in the body)
- Fever in infants and toddlers
- Fever without a known cause
- Henoch-schonlein purpura (a disease that causes inflammation and bleeding in small blood vessels)
- Hospital-acquired infections
- Ingrown nails
- Necrotizing enterocolitis imaging (procedure to visualize severe intestinal damage in premature infants)
What to expect with Gram-Positive Bacteria
The outlook after getting infected with gram-positive organisms can differ greatly. The highest death rates are often seen in the elderly, who typically have weaker immune systems and less overall bodily strength.
