Peptostreptococcus Infection Clinical Presentation

Updated: Apr 30, 2021
  • Author: Itzhak Brook, MD, MSc; Chief Editor: Michael Stuart Bronze, MD  more...
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Although anaerobic cocci can be isolated from infections at all body sites, a predisposition for certain sites has been observed. In general, Peptostreptococcus species, particularly P magnus, have been recovered more often from subcutaneous and soft tissue abscesses and diabetes-related foot ulcers than from intra-abdominal infections. [1]  Peptostreptococcus infections occur more often in chronic infections and in association with the predisposing conditions below.

CNS infections

Anaerobic gram-positive cocci and microaerophilic streptococci can be isolated from subdural empyema and from brain abscesses that develop as sequelae of chronic infections of the ears, [15] mastoid, sinuses, [16] and teeth.

Anaerobic gram-positive cocci and microaerophilic streptococci have been isolated from 18 (10- 46%) of 39 brain abscesses. [1, 2, 17]

Upper respiratory tract and dental infections

The high rate of anaerobic cocci colonization of the oropharynx accounts for the organisms' significance in these infections. [1, 2, 8, 18] Anaerobic gram-positive cocci and microaerophilic streptococci are often recovered from acute and chronic upper respiratory tract infections. These organisms have been recovered in 9%-38% of patients with chronic otitis media, [18] 15% of patients with chronic mastoiditis, 30% of patients with chronic sinusitis, 33% of patients with peritonsillar and retropharyngeal abscesses, and 50% of patients with purulent parotitis. [19] They have also accounted for two thirds of isolates from periodontal abscesses and are also found in acute necrotizing gingivitis.

In more than 90% of cases, other organisms also present in the oral florae have been found mixed with anaerobic gram-positive cocci and microaerophilic streptococci. These include Staphylococcus aureus, Streptococcus species, Fusobacterium species, and pigmented Prevotella and Porphyromonas species.

Anaerobic pleuropulmonary infections  [1, 2, 5]

Anaerobic gram-positive cocci and microaerophilic streptococci account for 10-20% of anaerobic isolates recovered from properly obtained specimens of pulmonary infections. The pulmonary infections in which these organisms have been found most frequently include aspiration pneumonia, empyema associated with aspiration pneumonia, lung abscesses, and mediastinitis.

Obtaining appropriate culture specimens of these organisms requires the use of transtracheal aspiration, aspiration through double-lumen catheterization, or direct lung puncture.

Intra-abdominal infections  [1, 2, 20]

Because anaerobic gram-positive cocci are part of the normal gastrointestinal florae, they can be isolated in approximately 20% of specimens from intra-abdominal infections, such as peritonitis and abscesses of the liver, spleen, and abdomen.

Anaerobic gram-positive cocci are generally recovered mixed with other organisms of intestinal origin that include Escherichia coli,Bacteroides fragilis group, and Clostridium species.

Female pelvic infections  [1, 2]

Anaerobic gram-positive cocci and microaerophilic streptococci can be isolated in 25-50% of patients with endometritis, pyoderma, pelvic abscess, Bartholin gland abscess, postsurgical pelvic infections, or pelvic inflammatory disease. The origin of these organisms is probably the vaginal and cervical florae.

The predominant anaerobic gram-positive cocci are P asaccharolyticus, P anaerobius, and P prevotii.

Bacteremias with anaerobic gram-positive cocci and microaerophilic streptococci are often associated with septic abortion.

Anaerobic gram-positive cocci are generally found mixed with Prevotella bivia and Prevotella disiens.

Osteomyelitis and arthritis  [1, 2, 21, 22]

Anaerobic gram-positive cocci are frequently isolated from anaerobically infected bones and joints. In studies, they accounted for 40% of anaerobic isolates of osteomyelitis caused by anaerobic bacteria and 20% of anaerobic isolates of arthritis caused by anaerobic bacteria.

P magnus and P prevotii are the predominant bone and joint isolates. In a 1980 study by Bourgault and colleagues, most patients with infections involving these organisms underwent orthopedic surgery and had foreign prosthetic material in place at the time of infection. [3] Management of these infections requires prolonged courses of antimicrobials and is enhanced by removal of the foreign material.

Skin and soft tissue infections

Anaerobic gram-positive cocci and microaerophilic streptococci are often recovered in polymicrobial skin and soft tissue infections [1, 2]  (eg, necrotizing synergistic gangrene; necrotizing fasciitis; decubitus ulcers; diabetes-related foot infections; paronychia; burns; human or animal bites [23] ). Peptostreptococcus is also commonly found in the tropical infection, acute noma. Anaerobic gram-positive cocci and microaerophilic streptococci are generally found mixed with other aerobic and anaerobic florae that originate from the mucosal surface adjacent to the infected site or that have been inoculated into the infected site.

Gastrointestinal florae can cause infections such as gluteal decubitus ulcers, diabetes-related foot infections, and rectal abscesses.

Vaginal and cervical florae can cause scalp wound infections in newborns after fetal monitoring.

Because anaerobic gram-positive cocci and microaerophilic streptococci are part of the normal skin florae, care must be used when obtaining specimens to avoid contamination by these florae.

Bacteremia and endocarditis  [14, 24]

Anaerobic gram-positive cocci and microaerophilic streptococci may be responsible for 4-15% of anaerobic bacteria isolated from blood cultures of patients with clinically significant anaerobic bacteremia. They are often recovered in persons with puerperal sepsis.

Peptostreptococci can cause fatal endocarditis, paravalvular abscess, and pericarditis. [25]

The most frequent source of bacteremia due to Peptostreptococcus is infections of the oropharynx, lower respiratory tract, female genital tract, abdomen, skin, and soft tissues. [26]  Peptoniphilus species that were formerly classified in the genus Peptostreptococcus have been recovered from blood samples in patients with pneumonia, from patients in preterm delivery, from patients with soft tissue infection, and from patients with colon or bladder disease. Half of these infections were polymicrobial. [27]

Predisposing factors for bacteremia due to Peptostreptococcus include malignancy; recent gastrointestinal, obstetrical, or gynecological surgery; immunosuppression; dental procedures; and oropharyngeal, female genital tract, abdominal, and soft tissue infections.

Microaerophilic streptococci typically account for 5-10% of cases of endocarditis; however, peptostreptococci have only rarely been isolated.



The following are the major predisposing conditions to infection with anaerobic gram-positive cocci and microaerophilic streptococci:

  • Previous surgery

  • Rupture of viscous

  • Immunodeficiency

  • Malignancy

  • Trauma

  • Diabetes

  • Steroid therapy

  • Presence of a foreign body

  • Sickle cell anemia

  • Reduced blood supply

  • Vascular disease

Infection with aerobic bacteria can make the local tissue conditions more favorable for the growth of anaerobes, including anaerobic cocci. Anaerobic conditions and anaerobic bacteria can impair host defenses. Anaerobic infection often manifests as suppuration, thrombophlebitis, abscess formation, and gangrenous destruction of tissue associated with gas. Anaerobes, including peptostreptococci, are common in chronic infections. Therapy with antimicrobials (eg, aminoglycosides, trimethoprim-sulfamethazine, older quinolones) often does not eradicate anaerobes.