eMedicine Specialties > Infectious Diseases > Bacterial Infections

Peptostreptococcus Infection

Itzhak Brook, MD, MSc, Professor, Department of Pediatrics, Georgetown University School of Medicine

Updated: Jun 17, 2008

Introduction

Background

Clinically significant anaerobic cocci include Peptostreptococcus species, Veillonella species (gram-negative cocci), and microaerophilic streptococci (aerotolerant). Anaerobic gram-positive cocci include various clinically significant species of the genus Peptostreptococcus.¹

Peptostreptococcus infections can occur in all body sites, including the CNS, head, neck, chest, abdomen, pelvis, skin, bone, joint, and soft tissues. Inadequate therapy against these anaerobic bacteria may lead to clinical failures. Because of their fastidiousness, peptostreptococci are difficult to isolate and are often overlooked. Isolating them requires appropriate methods of specimen collection, transportation, and cultivation. Their slow growth and increasing resistance to antimicrobials, in addition to the polymicrobial nature of the infection, complicate treatment.²

Peptostreptococcus is the only genus among anaerobic gram-positive cocci encountered in clinical infections. This group also includes species within the genus formerly known as Peptococcus, with the exception of Peptococcus niger. This change in taxonomy was based on the results of a guanine-plus-cytosine content analysis. Additionally, Gaffkya anaerobia was renamed Peptostreptococcus tetradius. The species of anaerobic gram-positive cocci isolated most commonly include Peptostreptococcus magnus,³ Peptostreptococcus asaccharolyticus, Peptostreptococcus anaerobius, Peptostreptococcus prevotii, and Peptostreptococcus micros.^4,5,6,7

Anaerobic gram-positive cocci that produce large amounts of lactic acid during the process of carbohydrate fermentation were reclassified as Streptococcus parvulus and Streptococcus morbillorum from Peptococcus or Peptostreptococcus. Most of these organisms are anaerobic, but some are microaerophilic.

Based on DNA homology and whole-cell polypeptide-pattern study findings supported by phenotypic characteristics, the DNA homology group of microaerobic streptococci that was formerly known as Streptococcus anginosus or Streptococcus milleri is now composed of 3 distinct species: S anginosus, Streptococcus constellatus, and Streptococcus intermedius.⁸ The microaerobic species S morbillorum was transferred into the genus Gemella. A new species within the genus Peptostreptococcus is Peptostreptococcus hydrogenalis; it contains the indole-positive, saccharolytic strains of the genus.⁹

Pathophysiology

Peptostreptococcus organisms are part of the normal florae of human mucocutaneous surfaces, including the mouth, intestinal tract, vagina, urethra, and skin.² They are isolated with high frequency from all specimen sources. Anaerobic gram-positive cocci are the second most frequently recovered anaerobes and account for approximately one quarter of anaerobic isolates. Anaerobic gram-positive cocci are usually recovered mixed with other anaerobic or aerobic bacteria from infections at different sites of the body.

Many of these infections are synergistic. Bacterial synergy, the presence of which is determined by mutual induction of sepsis enhancement, increased mortality, increased ability to induce abscesses, and enhancement of the growth of the bacterial components in mixed infections, is found between anaerobic gram-positive cocci and their aerobic and anaerobic counterparts.¹⁰ The ability of anaerobic gram-positive cocci and microaerophilic streptococci to produce capsular material is an important virulence mechanism, but other factors may also influence the interaction of these organisms in mixed infections.¹¹

Frequency

United States

The exact frequency of Peptostreptococcus infections is difficult to calculate because of inappropriate methods of collection, transportation, and cultivation of specimens. These infections are found more commonly in patients with chronic infections. Recovery rates in blood cultures are 2-5% and are higher in patients who have predisposing conditions. In 1974, Martin reported that anaerobic cocci were isolated in 8.5-31% of clinical specimens that yielded any anaerobic bacteria at the Mayo Clinic.⁶

In 2 studies published in 1988 and 1989, Brook reported that anaerobic gram-positive cocci accounted for 26% of all anaerobic bacteria recovered at BethesdaNavyHospital and WalterReedArmyHospital from 1973-1985. The infected sites where the organisms predominated were ears (53% of all anaerobic isolates), cysts (40%), bones (39%), and obstetrical and gynecological sites (35%). They were occasionally found in the CNS, abdomen, lymph nodes, bile, and eyes. Most isolates were found in abscesses, wounds, and obstetrical and gynecological infections.

The recovery rates differed for the different anaerobic gram-positive cocci. In descending order of frequency, the most common anaerobic gram-positive cocci were P magnus (18% of all anaerobic gram-positive cocci and microaerophilic streptococci), P asaccharolyticus (17%), P anaerobius (16%), P prevotii (13%), P micros (4%), Peptostreptococcus saccharolyticus (3%), and Peptostreptococcus intermedius (2%).^5,12

The highest recovery rates of P magnus were in bone and chest infections. The highest recovery rate of P asaccharolyticus and P anaerobius were with obstetrical/gynecological and respiratory tract infections and wounds. Isolates of each of the most frequently recovered anaerobic gram-positive cocci were recovered from abscesses, wounds, and obstetrical and gynecological infections.⁵

Although most of the infections were polymicrobial when anaerobic and facultative cocci were recovered, these organisms were isolated in pure culture in 45 (8%) of 559 patients who had infections involving anaerobic gram-positive cocci, in 12 (10%) of 121 individuals who had infections due to microaerophilic streptococci, and in 15 (9%) of 176 patients who had P magnus infection.⁷ The most frequent types of infections from which anaerobic gram-positive cocci were isolated in pure culture were soft tissue infections, osteomyelitis, arthritis (especially in the presence of a prosthetic implant), and bacteremia. Most patients from whom microaerophilic streptococci were recovered in pure culture had abscesses (eg, dental, intracranial, pulmonary), bacteremia, meningitis, or conjunctivitis.

P magnus is the most commonly isolated anaerobic cocci.³ It is most often recovered in pure culture. The most common peptostreptococci in the different infectious sites are P anaerobius in oral infections; P magnus and P micros in respiratory tract infections; P magnus, P micros, P asaccharolyticus, Peptostreptococcus vaginalis, and P anaerobius in skin and soft tissue infections; P magnus and P micros in deep organ abscesses; P magnus, P micros, and P anaerobius in gastrointestinal tract–associated infections; P magnus, P micros, P asaccharolyticus, P vaginalis, P tetradius, and P anaerobius in female genitourinary infections; and P magnus, P asaccharolyticus, P vaginalis, and P anaerobius in bone and joint infections and leg and foot ulcers.⁸

International

The frequency of these infections appears to be higher in developing countries, where therapy is often inadequate or delayed.

Mortality/Morbidity

Mortality has decreased over the past 3 decades.

Age

Peptostreptococcus infections can occur in patients of all ages; however, head and neck infections occur more frequently in children than in adults.¹

Clinical

Physical

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,¹³ mastoid, sinuses,¹⁴ and teeth.
- Anaerobic gram-positive cocci and microaerophilic streptococci have been isolated from 18 (46%) of 39 brain abscesses.^2,1
Upper respiratory tract and dental infections^2,1
- The high rate of anaerobic cocci colonization of the oropharynx accounts for the organisms' significance in these infections. Anaerobic gram-positive cocci and microaerophilic streptococci are often recovered from acute and chronic upper respiratory tract infections. These organisms have been recovered in 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. They have also accounted for two thirds of isolates from periodontal abscesses.
- 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^4,2,1
- 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^2,1
- 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^2,1
- 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^2,1
- 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^2,1
- Anaerobic gram-positive cocci and microaerophilic streptococci are often recovered in polymicrobial skin and soft tissue infections (eg, necrotizing synergistic gangrene; necrotizing fasciitis; decubitus ulcers; diabetes-related foot infections; paronychia; burns; human or animal bites; infected cysts; abscesses of the breast, rectum, and anus). 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^12,15
- 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.
- 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.
- 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.

Causes

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

Workup

Laboratory Studies

Microbiology⁹
- Anaerobic, microaerophilic, and facultative gram-positive cocci have minor morphological differences. P magnus has a larger diameter than other anaerobic gram-positive cocci. P micros has a smaller diameter than other anaerobic gram-positive cocci and usually forms short chains. P anaerobius and Peptostreptococcus productus are elongated and often appear in pairs or chains.
- Gas-liquid chromatography and biochemical tests are required for genus-level identification and separation of most anaerobic gram-positive cocci. These organisms are fastidious, and their complete identification is often difficult. Because of ill-defined differences in the pathogenic potential for the different species, the need for exact specification is controversial.
- Anaerobic cocci show slow but adequate growth on all nonselective anaerobic growth media. Vancomycin-containing selective media inhibit their growth.
Recovery in clinical specimens⁹
- Anaerobic and facultative gram-positive cocci are often isolated from clinical specimens mixed with other anaerobic or aerobic bacteria and, on rare occasions, are isolated as the sole pathogen. As a group, these organisms are the most frequently recovered anaerobes in cutaneous, oral, respiratory tract, and female genital tract infections.
- Collecting anaerobic bacteria specimens is important because documentation of an anaerobic infection is through culture of organisms from the infected site. Documentation requires proper collection of appropriate specimens, expeditious transportation, and careful laboratory processing.
- Obtain uncontaminated specimens. Inadequate culture techniques or media can lead to faulty results and the incorrect conclusion that only aerobic organisms are present in a mixed infection. Specimens must be obtained free of contamination. Inadequate techniques or media can lead to missing the presence of anaerobic bacteria or the assumption that only aerobic organisms are present in a mixed infection.
- Because anaerobes are present on mucous membranes and skin, even minimal contamination with normal florae can be misleading.
- Unacceptable or inappropriate specimens can also yield normal florae and therefore have no diagnostic value. Obtain appropriate specimens using techniques that bypass the normal florae.
- Direct-needle aspiration is the best method of obtaining a culture. Direct-needle aspiration is probably the best method of obtaining a culture, and the use of swabs is much less desirable.
  - Specimens obtained from normally sterile sites, such as blood, spinal, joint, or peritoneal fluids, are collected after thorough skin decontamination.
  - Two approaches are used to culture the maxillary sinus following sterilization of the canine fossa or the nasal vestibule, either via the canine fossa or via the inferior meatus.
  - Urine collected is collected by percutaneous suprapubic bladder aspiration.
  - Other specimens can be collected from abscess contents, from deep aspirates of wounds, and by special techniques, such as transtracheal aspirates or direct lung puncture.
  - Specimens of the lower respiratory tract are difficult to obtain without contamination with indigenous florae. Double-lumen catheter bronchial brushing and bronchoalveolar lavage, cultured quantitatively, can be useful.
  - Culdocentesis fluid obtained after decontamination of the vagina is acceptable.
- Transportation of specimens should be expeditious. Place specimens into an anaerobic transporter as soon as possible. These devices generally contain oxygen-free environments provided by a mixture of carbon dioxide, hydrogen, and nitrogen plus an aerobic condition indicator.
- Liquid or tissue specimens are always preferred to swabs.
  - Inoculate liquid specimens into an anaerobic transport vial or a syringe. All air bubbles are expelled from the syringe. Insertion of the needle tip into a sterile rubber stopper is no longer recommended. Because air gradually diffuses through the plastic syringe wall, specimens should be processed in less than 30 minutes.
  - Transport tissue specimens in an anaerobic jar or a sealed plastic bag rendered anaerobic.
  - If swabs are used, place them in sterilized tubes containing carbon dioxide or prereduced, anaerobically sterile Carey and Blair semisolid media.
- Gram stain of a smear of the specimen provides important preliminary information regarding types of organisms present, suggests appropriate initial therapy, and serves as a quality control. Immediately place cultures under anaerobic conditions and incubate for 48 hours or longer. An additional 36-48 hours is usually required for species- or genus-level identification using biochemical tests; kits containing these tests are commercially available.
- A rapid enzymatic test enables identification after only 4 hours of aerobic incubation. Gas-liquid chromatography of metabolites is often used. Nucleic acid probers and polymerase chain reaction methods are also being developed for rapid identification.¹⁶ Detailed procedures of laboratory methods can be found in microbiology manuals.
- Antimicrobial susceptibility test results of peptostreptococci have become less predictable because of the increasing resistance of peptostreptococci to several antimicrobials.¹⁷ Resistance to metronidazole is common. Routine susceptibility testing is time consuming and often unnecessary; however, it is important to test the susceptibility of isolates recovered from sterile body sites, those that are clinically important and have variable susceptibilities, and especially those isolated in pure cultures from properly collected specimens. These include isolates associated with bacteremia; endocarditis; and bone, joint, or skull infections.¹⁸
- Perform testing with antibiotics. Recommended methods include agar microbroth and macrobroth dilution. Newer methods include the E-test and the spiral gradient end point system. Agents that should be tested include penicillin, broad-spectrum penicillin, penicillin plus a beta-lactamase inhibitor, clindamycin, chloramphenicol, second-generation cephalosporins (eg, cefoxitin), newer quinolones, tigecycline, metronidazole, and carbapenems.

Imaging Studies

Radiological or imaging studies are helpful. The presence of gas in the infected site is a strong indication of anaerobic infection.

Treatment

Medical Care

A patient's recovery from anaerobic infection depends on prompt and proper treatment according to the following principles: (1) neutralizing toxins produced by anaerobes, (2) preventing local bacterial proliferation by changing the environment, and (3) limiting the spread of bacteria.

Control the environment by debriding necrotic tissue, draining pus, improving circulation, alleviating obstruction, and increasing tissue oxygenation. Certain types of adjunctive therapy, such as hyperbaric oxygen therapy, may be useful but remain unproven.
In many cases, antimicrobial therapy is the only form of therapy required, but it can also be an adjunct to a surgical approach. Because anaerobic bacteria, including peptostreptococci, are generally recovered mixed with aerobic organisms, choose antimicrobial agents that treat both types of pathogens, taking into consideration their aerobic and anaerobic antibacterial spectrum and their availability in oral or parenteral form.
Penicillin G is most effective for treating anaerobic gram-positive cocci and microaerophilic streptococci.
- Other effective agents include other penicillins, cephalosporins, chloramphenicol, clindamycin, vancomycin, telithromycin, linezolid, quinupristin/dalfopristin, and carbapenems.
- The efficacy of macrolides (eg, erythromycin) and imidazoles (eg, metronidazole) is variable and unpredictable. Imidazoles are ineffective against some anaerobic gram-positive cocci and all aerotolerant strains.
- The newer quinolones are effective against more than 90% of anaerobic cocci; ciprofloxacin is less effective.
- Occasionally, certain strains are resistant to antimicrobials, especially after administration of these agents.
- When mixed with other beta-lactamase–producing bacteria, anaerobic gram-positive cocci and microaerophilic streptococci may survive penicillin or cephalosporin therapy because of the protection provided by the free enzyme. In such instances, antimicrobials with wider spectrums of activity may be more effective.

Surgical Care

In most cases, surgical therapy is critically important. Surgical therapy includes (1) draining abscesses, (2) debriding necrotic tissues, (3) decompressing closed-space infections, and (4) relieving obstructions. If surgical drainage is not used, the infection may persist and serious complications may develop.

Medication

Clinical judgment, personal experience, safety, and expected level of patient compliance should direct the physician in the choice of antimicrobial agents. When choosing antimicrobials for the therapy of mixed infections, their aerobic and anaerobic antibacterial spectrum and their availability in oral or parenteral form should be considered. Some antimicrobials have a limited range of activity.

Aside from susceptibility patterns, other factors influencing the choice of antimicrobial therapy include the pharmacologic characteristics of the various drugs, their toxicity, their effect on the normal florae, and their bactericidal activity. Although identification of the infecting organisms and their antimicrobial susceptibility may be needed for selection of optimal therapy, the clinical setting and gram-stain preparation of the specimen may indicate the types of anaerobes present in the infection and may indicate the nature of the infectious process.

Although the duration of therapy for anaerobic infections is generally longer than for aerobic and facultative infections, the duration must be individualized depending on the patient's response to the therapy. In some cases, the patient may require a 6- to 8-week course. However, therapy may be shortened after proper surgical drainage.¹⁹

Because peptostreptococci are often mixed with other aerobic and anaerobic bacteria in the infectious process, broader antimicrobial coverage is often necessary. Furthermore, because of the difficulty in recovering other fastidious anaerobic organisms, they may not be recovered even when cultures are taken.

Antimicrobial agents with broader coverage against anaerobic bacteria, including peptostreptococci, include cefoxitin, clindamycin, carbapenem (eg, imipenem, meropenem, ertapenem), tigecycline, the combination of a penicillin (eg, ticarcillin) with a beta-lactamase inhibitor (ie, clavulanate), and quinolones with anti-anaerobic activity (ie, moxifloxacin).¹⁹

An anti–gram-negative enteric agent is generally added to treat Enterobacteriaceae when treating intra-abdominal infections.

Penicillin is added to metronidazole to cover microaerophilic streptococci, peptostreptococci, Actinomyces species, and Arachnia species when treating intracranial and dental infections.

Penicillin is the antimicrobial of choice for bacteremia caused by non beta-lactamase producers; however, if other organisms may be involved in another site, broader coverage is needed.

A macrolide or amoxicillin is added to metronidazole to treat S aureus and aerobic streptococci in upper respiratory tract infections.

Doxycycline is effective against chlamydial and mycoplasmal infections and is added to most regimens when treating pelvic infections.

Oral therapy for peptostreptococci is often substituted for parenteral therapy. Oral agents include clindamycin, amoxicillin and clavulanate, and chloramphenicol.

Antimicrobials

Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting.

Penicillin G (Pfizerpen)

Interferes with synthesis of cell-wall mucopeptide during active multiplication, resulting in bactericidal activity against susceptible microorganisms (beta-lactam).

Dosing

Adult

10-28 million U/d IV q4h in 6 divided doses

Pediatric

50,000-100,000 U/d IV

Interactions

Probenecid can increase effects; coadministration with tetracyclines can decrease effects

Contraindications

Documented hypersensitivity

Precautions

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

Precautions

Caution in impaired renal function; may cause angioedema, pruritic rash, delayed rash, and gastrointestinal intolerance

Cefoxitin (Mefoxin)

Second-generation cephalosporin indicated for gram-positive cocci and gram-negative rod infections. Infections caused by cephalosporin- or penicillin-resistant gram-negative bacteria may respond.

Dosing

Adult

2 g IV q6h

Pediatric

40 mg/kg/d IV q6h

Interactions

Probenecid may increase effects; coadministration with aminoglycosides or furosemide may increase nephrotoxicity (closely monitor renal function)

Contraindications

Documented hypersensitivity

Precautions

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

Precautions

Bacterial or fungal overgrowth of nonsusceptible organisms may occur with prolonged use or repeated treatment; caution in previously diagnosed colitis

Cefotetan (Cefotan)

Second-generation cephalosporin indicated for management of infections caused by susceptible gram-positive cocci and gram-negative rods.

Dosing

Adult

2 g IV q12h

Pediatric

20-40 mg/kg IV q12h for 5-10 d

Interactions

Consumption of alcohol within 72 h of administration may produce disulfiramlike reactions; may increase hypoprothrombinemic effects of anticoagulants

Contraindications

Documented hypersensitivity

Precautions

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

Precautions

Reduce dosage by half with CrCl <10-30 mL/min and by one fourth with CrCl <10 mL/min; bacterial or fungal overgrowth of nonsusceptible organisms may occur with prolonged or repeated therapy

Clindamycin (Cleocin)

Lincosamide for treatment of serious skin and soft tissue staphylococcal infections. Effective against aerobic and anaerobic streptococci (except enterococci). Inhibits bacterial growth, possibly by blocking dissociation of peptidyl t-RNA from ribosomes, causing RNA-dependent protein synthesis to arrest.

Dosing

Adult

150-300 mg PO q6h
600 mg IV q8h

Pediatric

20-30 mg/kg/d PO divided q6h
25-40 mg/kg/d IV

Interactions

Increases duration of neuromuscular blockade induced by tubocurarine and pancuronium; erythromycin may antagonize effects; antidiarrheals may delay absorption

Contraindications

Documented hypersensitivity; regional enteritis; ulcerative colitis; hepatic impairment; antibiotic-associated colitis

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Adjust dose in severe hepatic dysfunction; no adjustment necessary in renal insufficiency; commonly associated with Clostridium difficile diarrhea; associated with severe and possibly fatal colitis

Amoxicillin and clavulanate (Augmentin)

Treat bacteria resistant to beta-lactam antibiotics.

Dosing

Adult

500 mg PO q8h
875 mg PO q12h

Pediatric

40 mg/kg/d PO q8h (tid formulation)
45 mg/kg/d PO q12h (bid formulation)

Interactions

Coadministration with warfarin or heparin increases risk of bleeding

Contraindications

Documented hypersensitivity

Precautions

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

Precautions

Administer for a minimum of 10 d to eliminate organism and prevent sequelae (endocarditis, rheumatic fever); following treatment, perform cultures to confirm eradication of streptococci

Ticarcillin and clavulanate potassium (Timentin)

Inhibit biosynthesis of cell-wall mucopeptide and are effective during stage of active growth. Contains 4.7-5 mEq of Na⁺/g.

Dosing

Adult

3.1 g IV q4-6h

Pediatric

200-300 mg/kg/d IV q4-6h

Interactions

Tetracyclines may decrease effects; high concentrations of ticarcillin may physically inactivate aminoglycosides if administered in same IV line; effects are synergistic when administered concurrently with aminoglycosides; probenecid may increase penicillin levels

Contraindications

Documented hypersensitivity; severe pneumonia, bacteremia, pericarditis, emphysema, meningitis, and purulent or septic arthritis should not be treated with oral penicillin during acute stage

Precautions

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

Precautions

Perform CBC counts prior to initiation of therapy and at least weekly during therapy; monitor for liver function abnormalities by measuring AST and ALT during therapy; exercise caution in hepatic insufficiency; perform urinalysis, BUN, and creatinine determinations during therapy, and adjust dose if values become elevated; monitor blood levels to avoid possible neurotoxic reactions

Chloramphenicol (Chloromycetin)

Binds to 50S bacterial-ribosomal subunits and inhibits bacterial growth by inhibiting protein synthesis. Effective against gram-negative and gram-positive bacteria.

Dosing

Adult

500 mg to 1 g IV q6h; not to exceed 4 g/d

Pediatric

80-100 mg/kg/d IV

Interactions

Concurrently with barbiturates, serum levels may decrease while barbiturate levels may increase, causing toxicity; manifestations of hypoglycemia may occur with sulfonylureas; rifampin may reduce serum levels, presumably through hepatic enzyme induction; may increase effects of anticoagulants; may increase serum hydantoin levels, possibly resulting in toxicity; hydantoins may either increase or decrease levels

Contraindications

Documented hypersensitivity

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Use only for indicated infections; rarely, serious or fatal blood dyscrasias (aplastic anemia, hypoplastic anemia, thrombocytopenia, granulocytopenia) can occur; leukopenia, thrombocytopenia, and anemia are dose-related effects; adjust dose in severe liver or kidney dysfunction; caution in pregnancy at term or during labor because of potential toxic effects on fetus (gray baby syndrome)

Imipenem and cilastatin (Primaxin)

For treatment of multiorganism infections in which other agents do not have wide-spectrum coverage or are contraindicated because of potential for toxicity.

Dosing

Adult

500-750 mg IV q6h; not to exceed 3 g/d

Pediatric

15-25 mg/kg/d IV q6h; not to exceed 2 g/d

Interactions

Coadministration with cyclosporine may increase adverse CNS effects of both agents; coadministration with ganciclovir may result in generalized seizures

Contraindications

Documented hypersensitivity

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Adjust dose in renal insufficiency; high doses can cause seizures and renal failure, especially in elderly patients and those with prior seizure disorders

Meropenem (Merrem)

Bactericidal broad-spectrum carbapenem antibiotic that inhibits cell-wall synthesis. Effective against most gram-positive and gram-negative bacteria. Has slightly increased activity against gram-negatives and slightly decreased activity against staphylococci and streptococci compared with imipenem.

Dosing

Adult

1 g IV q8h

Pediatric

<3 months: Not recommended
>3 months: 40 mg/kg IV q8h

Interactions

Probenecid may inhibit renal excretion, increasing levels

Contraindications

Documented hypersensitivity

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Pseudomembranous colitis and thrombocytopenia may occur, requiring immediate discontinuation of medication

Ertapenem (Invanz)

Bactericidal activity results from inhibition of cell wall synthesis and is mediated through ertapenem binding to penicillin-binding proteins. Stable against hydrolysis by a variety of beta-lactamases, including penicillinases, cephalosporinases, and extended-spectrum beta-lactamases. Hydrolyzed by metallo-beta-lactamases.

Dosing

Adult

1 g/d for 14 d if given IV and for 7 d if given IM; infuse over 30 min if given IV

Pediatric

Not established

Interactions

Probenecid may reduce renal clearance and increase half-life but benefit is minimal and does not justify coadministration

Contraindications

Documented hypersensitivity

Precautions

Pregnancy

B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals

Precautions

Pseudomembranous colitis may occur; seizures and adverse CNS reactions may occur; when using with lidocaine to administer IM, avoid inadvertent injection into blood vessel

Moxifloxacin (Avelox)

Inhibits the A subunits of DNA gyrase, resulting in inhibition of bacterial DNA replication and transcription.

Dosing

Adult

400 mg PO/IV qd

Pediatric

<18 years: Not recommended
>18 years: Administer as in adults

Interactions

Antacids and electrolyte supplements reduce absorption; loop diuretics, probenecid, and cimetidine increase serum levels; NSAIDs enhance CNS stimulating effect
May increase toxicity of theophylline, caffeine, cyclosporine, and digoxin (monitor digoxin levels); may increase effects of anticoagulants (monitor PT); ferrous sulfate decreases bioavailability (administer moxifloxacin 4 h prior or 8 h following ferrous sulfate); coadministration with drugs that prolong QTc interval (quinidine, procainamide, amiodarone, sotalol, erythromycin, tricyclic antidepressants) increase risk of life-threatening arrhythmia

Contraindications

Documented hypersensitivity; known Q-T prolongation; concurrent administration of drugs that cause Q-T prolongation

Precautions

Pregnancy

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

In prolonged therapy, periodically evaluate organ system functions (eg, renal, hepatic, hematopoietic); superinfections may occur with prolonged or repeated antibiotic therapy; fluoroquinolones have induced seizures in CNS disorders and caused tendinitis or tendon rupture

Tigecycline (Tygacil)

A glycylcycline antibiotic that is structurally similar to tetracycline antibiotics. Inhibits bacterial protein translation by binding to 30S ribosomal subunit, and blocks entry of amino-acyl tRNA molecules in ribosome A site. Complicated intra-abdominal infections caused by C freundii, E cloacae, E coli, K oxytoca, K pneumoniae, E faecalis (vancomycin-susceptible isolates only), S aureus (methicillin-susceptible isolates only), S anginosus group (includes S anginosus, S intermedius, and S constellatus), B fragilis, B thetaiotaomicron, B uniformis, B vulgatus, C perfringens, and P micros.

Dosing

Adult

Infuse each dose over 30-60 min
100 mg IV once, then 50 mg IV q12h
Severe hepatic impairment (ie, Child Pugh class C): 100 mg IV once, then 25 mg IV q12h

Pediatric

<18 years: Not established
>18 years: Administer as in adults

Interactions

Coadministration decreases warfarin clearance and increases warfarin C_max and AUC (monitor aPTT and INR); coadministration of antibiotics with oral contraceptives may decrease contraceptive effect

Contraindications

Documented hypersensitivity

Precautions

Pregnancy

D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus

Precautions

Caution in severe hepatic impairment (reduce dose); may adversely effect tooth development; may permit clostridial overgrowth, resulting in antibiotic-associated colitis; may have adverse effects similar to those of tetracyclines (eg, photosensitivity, pseudotumor cerebri, pancreatitis, antianabolic action)

Follow-up

Deterrence/Prevention

When peptostreptococci and other anaerobes predominate, aggressive treatment of acute infection can prevent chronic infection. When the risk of anaerobic infection is high, as with intra-abdominal and postsurgical infections, proper antimicrobial prophylaxis may reduce the risk.
Preventing oral florae aspiration by improving neurological status, suctioning oral secretions, improving oral hygiene, and maintaining lower stomach pH can reduce the risk of aspiration pneumonia and its complications.
Irrigating wounds, debriding necrotic tissue, draining pus, and improving the blood supply helps prevent skin and soft tissue infections.

Patient Education

For excellent patient education resources, visit eMedicine's Bacterial and Viral Infections Center. Also, see eMedicine's article Antibiotics.

Miscellaneous

Medicolegal Pitfalls

Failure to diagnose Peptostreptococcus infection
Failure to use proper antimicrobial therapy

References

Brook I. Anaerobic Infections. In: Diagnosis and Management. 4th Edition. New York: Informa Healthcare USA inc; 2007.
Finegold SM. Anaerobic Bacteria in Human Disease. Orlando, Fla: Academic Press; 1977.
Bourgault AM, Rosenblatt JE, Fitzgerald RH. Peptococcus magnus: a significant human pathogen. Ann Intern Med. Aug 1980;93(2):244-8. [Medline].
Bartlett JG. Anaerobic bacterial infections of the lung and pleural space. Clin Infect Dis. Jun 1993;16 Suppl 4:S248-55. [Medline].
Brook I. Recovery of anaerobic bacteria from clinical specimens in 12 years at two military hospitals. J Clin Microbiol. Jun 1988;26(6):1181-8. [Medline].
Martin WJ. Isolation and identification of anaerobic bacteria in the clinical laboratory. A 2-year experience. Mayo Clin Proc. May 1974;49(5):300-8. [Medline].
Brook I. Peptostreptococcal infection in children. Scand J Infect Dis. 1994;26(5):503-10. [Medline].
Murdoch DA. Gram-positive anaerobic cocci. Clin Microbiol Rev. Jan 1998;11(1):81-120. [Medline].
Jousime-Somers H, Summanen P, Citron DM, et al. Wadsworth-KTL Anaerobic Bacteriology Manual. 6^th ed. Belmont, Calif: Star Publishing; 2002.
Araki H, Kuriyama T, Nakagawa K, Karasawa T. The microbial synergy of Peptostreptococcus micros and Prevotella intermedia in a murine abscess model. Oral Microbiol Immunol. Jun 2004;19(3):177-81. [Medline].
Brook I, Walker RI. Pathogenicity of anaerobic gram-positive cocci. Infect Immun. Aug 1984;45(2):320-4. [Medline].
Brook I. Anaerobic bacterial bacteremia: 12-year experience in two military hospitals. J Infect Dis. Dec 1989;160(6):1071-5. [Medline].
Saini S, Gupta N, Aparna, Seema, Sachdeva OP. Bacteriological study of paediatric and adult chronic suppurative otitis media. Indian J Pathol Microbiol. Jul 2005;48(3):413-6. [Medline].
Brook I. Microbiology of acute and chronic maxillary sinusitis associated with an odontogenic origin. Laryngoscope. May 2005;115(5):823-5. [Medline].
Blairon L, De Gheldre Y, Delaere B, Sonet A, Bosly A, Glupczynski Y. A 62-month retrospective epidemiological survey of anaerobic bacteraemia in a university hospital. Clin Microbiol Infect. Jun 2006;12(6):527-32. [Medline].
Song Y, Liu C, McTeague M, Vu A, Liu JY, Finegold SM. Rapid identification of Gram-positive anaerobic coccal species originally classified in the genus Peptostreptococcus by multiplex PCR assays using genus- and species-specific primers. Microbiology. Jul 2003;149:1719-27. [Medline].
Aldridge KE, Ashcraft D, Cambre K, Pierson CL, Jenkins SG, Rosenblatt JE. Multicenter survey of the changing in vitro antimicrobial susceptibilities of clinical isolates of Bacteroides fragilis group, Prevotella, Fusobacterium, Porphyromonas, and Peptostreptococcus species. Antimicrob Agents Chemother. Apr 2001;45(4):1238-43. [Medline].
Wexler HM, Finegold SM. Current susceptibility patterns of anaerobic bacteria. Yonsei Med J. Dec 1998;39(6):495-501. [Medline].
Brook I. Treatment of anaerobic infection. Expert Rev Anti Infect Ther. Dec 2007;5(6):991-1006. [Medline].
Malik NN, Goh D, McLean C, Huchzermeyer P. Orbital cellulitis caused by Peptostreptococcus. Eye. Jun 2004;18(6):643-4. [Medline].

Keywords

Peptostreptococcus infection, anaerobic cocci, anaerobic gram-positive cocci, peptococci, peptostreptococci, Peptococcus, microaerophilic streptococci, Peptostreptococcus magnus, P magnus, Peptostreptococcus asaccharolyticus, P asaccharolyticus, Peptostreptococcus anaerobius, P anaerobius, Peptostreptococcus prevotii, P prevotii, Peptostreptococcus micros, P micros, Streptococcus anginosus, S anginosus, Streptococcus milleri, S milleri, Streptococcus constellatus, S constellatus, Streptococcus intermedius, S intermedius, Streptococcus morbillorum, S morbillorum, Peptostreptococcus hydrogenalis, P hydrogenalis, Staphylococcus aureus, S aureus, Streptococcus, Veillonella, Fusobacterium, Porphyromonas, Prevotella, Prevotella bivia, P bivia, Prevotella disiens, P disiens, Escherichia coli, E coli, Bacteroides fragilis, B fragilis

Contributor Information and Disclosures

Author

Itzhak Brook, MD, MSc, Professor, Department of Pediatrics, Georgetown University School of Medicine
Itzhak Brook, MD, MSc is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians-American Society of Internal Medicine, American Federation for Clinical Research, American Medical Association, American Society for Microbiology, Armed Forces Infectious Diseases Society, Association of Military Surgeons of the US, Infectious Diseases Society of America, International Immunocompromised Host Society, International Society for Infectious Diseases, Medical Society of the District of Columbia, New York Academy of Sciences, Pediatric Infectious Diseases Society, Society for Ear, Nose and Throat Advances in Children, Society for Experimental Biology and Medicine, Society for Pediatric Research, Southern Medical Association, and Surgical Infection Society
Disclosure: Nothing to disclose.

Medical Editor

Douglas A Drevets, MD, Assistant Professor, Department of Medicine, Section of Infectious Disease, Oklahoma University Health Sciences Center
Douglas A Drevets, MD is a member of the following medical societies: American Association of Immunologists, American Society for Microbiology, Central Society for Clinical Research, and Christian Medical & Dental Society
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Aaron Glatt, MD, Professor of Clinical Medicine, New York Medical College; President and CEO, Former Chief Medical Officer, Departments of Medicine and Infectious Diseases, New Island Hospital
Aaron Glatt, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physician Executives, American College of Physicians, American College of Physicians-American Society of Internal Medicine, American Medical Association, American Society for Microbiology, American Thoracic Society, American Venereal Disease Association, Infectious Diseases Society of America, International AIDS Society, and Society for Healthcare Epidemiology of America
Disclosure: Nothing to disclose.

CME Editor

Eleftherios Mylonakis, MD, Clinical and Research Fellow, Department of Internal Medicine, Division of Infectious Diseases, Massachusetts General Hospital
Eleftherios Mylonakis, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians, American Society for Microbiology, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

Chief Editor

Burke A Cunha, MD, Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital
Burke A Cunha, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

Further Reading