Peptostreptococcus Infection

Peptostreptococcus infections are caused by bacteria that normally live harmlessly in the human body but can turn dangerous when conditions allow them to spread and multiply beyond their usual areas.

Table of contents

• What is Peptostreptococcus?
• Where these bacteria normally live
• Types of infections
• Symptoms of infection
• How infections develop
• Diagnosis
• Treatment options

What is Peptostreptococcus?

Peptostreptococcus is a type of bacteria that belongs to a group called anaerobic bacteria, which means they grow in places without oxygen. These bacteria are very small, round in shape, and can appear alone, in pairs, or in short chains when viewed under a microscope^[1].

There are several species within this group. The most commonly identified ones include Peptostreptococcus magnus, Peptostreptococcus asaccharolyticus, Peptostreptococcus anaerobius, Peptostreptococcus prevotii, and Peptostreptococcus micros^[2]. The scientific classification of these bacteria has changed over the years based on new research, and some species previously called Peptostreptococcus have been moved to other groups^[3].

These bacteria grow slowly and are sometimes difficult to identify in laboratory tests because they require special conditions for growth^[2].

Where these bacteria normally live

Peptostreptococcus species are commensal organisms, meaning they live naturally in and on the human body without causing harm under normal circumstances. They are part of the normal bacterial community in several areas^[2].

• mouth
• throat
• skin
• gastrointestinal tract (digestive system)
• vagina
• urinary tract

Peptostreptococcus bacteria are found frequently in specimens from all body sites. Anaerobic bacteria like Peptostreptococcus are the second most commonly recovered type of anaerobic bacteria, making up about one quarter of all anaerobic bacteria found in infections^[3]. However, they usually do not cause problems unless conditions change that allow them to become harmful.

Types of infections

Peptostreptococcus bacteria can cause infections in many different parts of the body. These infections can range from mild to severe, and they occur more often in people with certain risk factors or underlying health conditions^[1].

Most often, Peptostreptococcus bacteria are recovered mixed together with other bacteria, both those that need oxygen and those that don’t. This means infections usually involve multiple types of bacteria working together^[2].

Brain and nervous system infections

These bacteria can be isolated from meningitis (infection of the membranes covering the brain and spinal cord), brain abscesses (pockets of pus in the brain), and other infections of the brain and skull. Such infections often develop as complications of long-lasting infections in the ears, sinuses, or teeth^[1].

Upper respiratory and dental infections

Because Peptostreptococcus bacteria commonly live in the mouth and throat, they play a significant role in infections in these areas. They have been found in 9 to 38 percent of patients with chronic middle ear infections, 15 percent with chronic infection of the bone behind the ear, 30 percent with chronic sinus infections, and 33 percent with abscesses around the tonsils and back of the throat^[1].

These bacteria also account for two thirds of isolates from gum abscesses and are found in severe gum infections^[1]. In more than 90 percent of cases, other bacteria from the mouth are also present alongside Peptostreptococcus^[1].

Lung infections

Peptostreptococcus accounts for 10 to 20 percent of anaerobic bacteria recovered from properly collected lung infection specimens. The lung infections where these organisms are found most frequently include pneumonia caused by breathing in mouth contents, lung abscesses, empyema (pus around the lungs), and infections in the space between the lungs^[1].

Abdominal infections

Because these bacteria are part of the normal digestive system, they can be found in about 20 percent of specimens from abdominal infections such as peritonitis (infection of the abdominal lining) and abscesses of the liver, spleen, and abdomen. They are generally recovered mixed with other intestinal bacteria^[1].

Female reproductive system infections

Peptostreptococcus can be isolated in 25 to 50 percent of patients with infections of the uterus lining, pelvic abscesses, infections after pelvic surgery, or pelvic inflammatory disease^[1].

Skin and soft tissue infections

Peptostreptococcus species, particularly P. magnus, have been found more often in skin abscesses and foot ulcers in people with diabetes than in abdominal infections^[1]. These bacteria can cause brain, liver, breast, and lung abscesses, as well as widespread tissue infections that destroy tissue^[2].

Symptoms of infection

The symptoms depend on where in the body the infection occurs. Because Peptostreptococcus infections tend to be chronic (long-lasting) rather than sudden, symptoms may develop gradually^[1].

Common symptoms of Peptostreptococcus infections include:

• Fever
• Pain and swelling at the site of infection
• Redness and warmth of affected skin
• Pus or fluid drainage
• Pain when swallowing (if throat is affected)
• Difficulty breathing (if lungs are affected)
• Abdominal pain (if digestive system is affected)

For brain infections, symptoms may include severe headache, stiff neck, confusion, and fever. For lung infections, symptoms include cough, chest pain, and difficulty breathing^[1].

How infections develop

Peptostreptococcus bacteria become harmful when they move from their normal locations to other parts of the body where they should not be. This usually happens when certain conditions are present^[2].

Infections typically occur when:

• The immune system is weakened by illness or medications
• There is trauma or injury to tissue
• Surgery creates openings for bacteria to enter
• There are breaks in the skin or mucous membranes
• There is poor blood circulation to an area
• Other chronic diseases are present, such as diabetes

Infection is usually associated with trauma or disease^[6]. Under conditions where the immune system is suppressed or tissues are damaged, these normally harmless bacteria can become disease-causing and even spread through the bloodstream^[2].

In most cases, Peptostreptococcus works together with other bacteria in what are called mixed anaerobic infections. This means multiple types of bacteria that don’t need oxygen are working together to cause disease^[2].

Diagnosis

Diagnosing a Peptostreptococcus infection requires proper collection and testing of specimens. Healthcare providers monitor for symptoms and confirm the presence of bacteria through laboratory culture^[6].

The best specimens for culture are aspirates (fluid removed with a needle) or tissue samples^[6]. Because these bacteria grow slowly and need special conditions without oxygen, they can be difficult to isolate in the laboratory. This is one reason why they are sometimes overlooked^[3].

The bacteria are identified by their appearance under the microscope and by special tests that determine which species is present. Small round bacteria may be seen on laboratory slides in short chains and pairs^[4].

Treatment options

Recovery from Peptostreptococcus infection depends on quick and proper treatment. Treatment follows several important principles^[8]:

Antibiotic therapy

Penicillin G is most effective for treating Peptostreptococcus and similar bacteria. Other effective medications include other penicillins, cephalosporins, chloramphenicol, clindamycin, vancomycin, telithromycin, linezolid, quinupristin/dalfopristin, and carbapenems^[8].

The effectiveness of macrolides (such as erythromycin) and imidazoles (such as metronidazole) varies and cannot always be predicted. The newer quinolone antibiotics work against more than 90 percent of these bacteria, though ciprofloxacin is less effective^[8].

Because Peptostreptococcus is usually found mixed with other bacteria, healthcare providers choose antibiotics that can treat both the anaerobic bacteria (those that don’t need oxygen) and the aerobic bacteria (those that do need oxygen) that are present^[8].

Sometimes certain strains become resistant to antibiotics, especially after these medicines have been used before. When mixed with other bacteria that produce enzymes that break down certain antibiotics, Peptostreptococcus may survive treatment with penicillin or similar drugs because of protection from these enzymes. In such cases, antibiotics with broader activity may be more effective^[8].

Surgical treatment

In many cases, surgery is critically important. Surgical treatment includes^[8]:

• Draining abscesses by aspiration or surgical drainage
• Removing dead tissue
• Relieving pressure from closed-space infections
• Removing blockages

Without surgical drainage when needed, the infection may continue, and serious complications may develop^[8].

Additional measures

Treatment also focuses on changing the environment where bacteria grow by removing dead tissue, draining pus, improving blood circulation, relieving blockages, and increasing oxygen to tissues^[8].

The length of treatment for these infections is generally longer than for other types of bacterial infections and must be adjusted based on how the patient responds. In some cases, patients may need 6 to 8 weeks of treatment. However, treatment time may be shortened after proper surgical drainage^[9].