You’re Not Alone; Strep Resides in Your Throat and Beyond

March 6, 2017

Strep bacteria exist as microscopic spheres and other unseen shapes on and below our own surfaces. Some are usually benign, dwelling in mouths, skin, intestines, and respiratory tracts in forms that do little harm to most people. Others can cause meningitis, ear infections, and pneumonia.


Most of us can recall the unpleasant sensation of sitting in a doctor’s office, feeling a cotton swab swipe across the sore territory of our throats. Along with the symptoms—fever, red swollen tonsils, and a sore throat—this swab would be tested to confirm whether the culprit was the strep bacterial infection (also called group A strep). Fortunately, it’s an infection easily treatable with antibiotics.

This is just one species of strep; there are many other strep species, and fortunately, most are treatable with antibiotics. They exist as microscopic spheres and other unseen shapes on and below our own surfaces. Some are usually benign, dwelling in mouths, skin, intestines, and respiratory tracts in forms that do little harm to most people. Others can cause meningitis, ear infections, and pneumonia.

These infections are age-old: They have been known for centuries, but were first delineated into separate disease entities in the 16th century AD, according to the publication Streptococcus pyogenes: Basic Biology to Clinical Manifestations.

Strep are fairly versatile. Bacteria that causes strep throat can cause flesh-eating bacterial infections or rheumatic fever.

Mark Fisher, PhD, medical director at ARUP Laboratories

While strep is old, it is also broad and marvelous in range. “The type that causes strep throat can (in more rare cases) cause flesh-eating bacterial infections or the post-infectious inflammatory disease, acute rheumatic fever, that can involve the heart, joints, skin and brain or post streptococcal glomerulonephritis affecting the kidneys. The bacteria are multi-faceted pathogens,” says Mark Fisher, PhD, D(ABMM), a medical director at ARUP Laboratories and assistant professor of pathology at the University of Utah School of Medicine in Salt Lake City.

Let’s talk strep—the positive and the negative. Viridans streptococcus has a name derived from the Latin for green; this is because this bacteria partially breaks down (or hemolyzes) red blood cells, leading to a green color in the blood-containing culture media. This bacteria type hangs out in the mouth or respiratory tract and is often considered beneficial or neutral. But if a patient has low immunity or a prosthetic heart valve, they can be more susceptible to infection. In that case, when our gums bleed during flossing or a dental cleaning, the bacteria can be introduced into our bloodstream. In rare cases, an infection of the heart’s inner lining called endocardidis can result.

Streptococcus pneumoniae is a type of strep that can cause ear infections, meningitis, and pneumonia, especially in older people and children under two. This bacteria was first isolated by Louis Pasteur in 1881 from a patient’s saliva.  In the most serious cases, it sometimes causes blood stream infection or sepsis—a massive response to a bacterial infection that gets into the blood and can lead to organ failure or other injury: “It’s one of the most severe pathogens we have,” observed Harry Hill, MD, an ARUP medical director and professor of Pathology, Medicine and Pediatrics at the University of Utah School of Medicine.

Unlike for group A strep, there are existing vaccines for Streptococcus pneumoniae. It is good, too, that pediatric and adult vaccines exist for it, because children younger than two years old have low levels of certain blood antibodies (immunoglobulin G2) that make them less responsive to adult strep vaccines. That inoculation can help ward off the bacteria that can cause meningitis and pneumonia, as well as sepsis.

Catherine Arnold, Science Communications Writer