AUTHOR AND EDITOR INFORMATION

Section 1 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• References

INTRODUCTION

Section 2 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• References

Background

Lancefield group B beta streptococci, Streptococcus agalactiae, once were considered pathogens only of domestic animals, causing mastitis in cows. S agalactiae now is best known as a cause of postpartum infection and as the most common cause of neonatal sepsis. More recently, the role of this organism as a cause of infection in nonpregnant adults has been described in a number of series. These studies allow description of the clinical spectrum of disease, including clinical features, risk factors, therapy, and outcome of group B streptococci in the nonpregnant adult.

Group B streptococci colonize the vaginal and gastrointestinal tract in healthy women. Neonates acquire the organism as a result of vertical transmission from the maternal genital tract to the infant in utero or at delivery. Carriage rates in women can range from 5-40%. While acquisition of the organism by the neonate is efficient, the rate of subsequent clinical disease is quite low, 1-2%. Neonatal sepsis from group B streptococci is a rare event, but it is more common in the setting of prematurity and prolonged rupture of the membranes. The large number of women who carry this organism and the fact that neonatal sepsis is a rare event make a prevention approach to this problem difficult. Many pregnant women require treatment to prevent a single neonatal infection. This problem has been studied, focusing on both immunoprophylaxis and chemoprophylaxis.

Disease in the neonate is divided into early and late disease. Early neonatal sepsis with group B streptococci often is observed within 24 hours of delivery, but it can become apparent as late as 7 days after birth. Nothing specific regarding the clinical presentation in early disease differentiates group B streptococci as the etiology from other pathogens. Pneumonia with bacteremia is common and meningitis less likely. Late disease is defined as infection after 1 week and before 3 months after birth. Late disease commonly is serotype III, characterized by bacteremia and meningitis.

Group B streptococcal infection in the infant is more common in the absence of antibody to group B streptococci. Because antibody to group B streptococci is protective for the disease in the animal model, interest in vaccination as an approach to reduce the incidence of group B streptococcal colonization in healthy women is ongoing. Vaccine development was promising at one time, but shifting serotypes of group B streptococci responsible for clinical disease have limited this approach. Problems related to access to vaccination for women of childbearing age and the emotion and possible litigation associated with vaccination during pregnancy have made this approach less attractive.

The current approach to the prevention of group B streptococcal infection in pregnancy has become a national standard as a result of the effort of the Centers for Disease Control and Prevention (CDC) in 1995. This approach requires intrapartum antimicrobial prophylaxis in term women with culture evidence of recent vaginal or rectal group B streptococcal infection. Women without a known group B streptococci status delivering before 37 weeks' gestation with premature rupture of the membranes or intrapartum fever also are candidates for intrapartum antimicrobial prophylaxis. Penicillin or ampicillin is the initial approach to this problem. Clindamycin and erythromycin are standard for the individual with penicillin allergy, but group B streptococci now are not always sensitive to these 2 drugs.

Group B streptococci as a cause of infection in pregnant women can be manifest by chorioamnionitis, endometritis, or genitourinary infection with bacteremia. Rarely, endocarditis or meningitis can be observed.

Only in the last 3 decades has the role of group B streptococci as a serious pathogen in the nonpregnant adult been well defined. A number of studies have allowed description of the clinical spectrum of disease, including clinical features, risk factors, therapy, and outcomes. This organism is an extremely rare cause of infection in a healthy individual. It almost always is associated with underlying abnormalities. Diabetes is associated most commonly with group B streptococci in some series. This association, which the authors have observed over the last 25 years, is unexplained. Malignancy was the most common association in a series from an institution with a large oncology population. Cardiovascular and genitourinary abnormalities have been observed as major factors for the acquisition of group B streptococci. Other conditions associated with group B streptococci in adults include neurologic deficits, cirrhosis, steroids, AIDS, renal dysfunction, and peripheral vascular disease.

Group B streptococci in elderly people, aged 70 years or older, is strongly linked to congestive heart failure and being bedridden. Urinary tract infection, pneumonia, and soft tissue infection were the most common illnesses in this group. Neurologic illness is associated with pneumonia in elderly people, possibly as a result of aspiration of group B streptococci from the upper respiratory tract. Nosocomial infection with group B streptococci was common in this group and is described in other series. The source of this infection is not always clear, but the genitourinary tract and skin are thought to be the sources of some nosocomial infections.

Group B streptococci colonize not only the female genital tract but also are found commonly in the gastrointestinal tract and have been described as asymptomatic colonizers of the urethra in both men and women. Group B streptococci can colonize the upper respiratory tract. Colonization also is observed in wound and soft tissue cultures in the absence of obvious infection. Determining the acquisition and transmission of the organism can be puzzling. Group B streptococci are very invasive but produce little inflammation at the entry site.

Primary bacteremia without an obvious source with group B streptococcal infection is a common presentation in adults. While one series suggests that group B streptococci bacteremia is low grade and easily controlled with little morbidity, other authors suggest that the clinical presentation may be that of classic sepsis with shock and may carry a high mortality. Sustained bacteremia raises the question of endocarditis or an infected catheter. Group B streptococci can be a cause of acute destructive endocarditis, which may require emergency valve replacement. Other sources of bacteremia include pneumonia in elderly people and genitourinary and soft tissue infection. Polymicrobial bacteremia with group B streptococci is observed in disease related to infected lines and also can reflect a genitourinary source.

Urinary tract infections are a common manifestation of group B streptococcal disease. This is observed in pregnancy as well as in the nonpregnant adult.

A variety of skin and soft tissue infections, including cellulitis, line-site infection, infected decubiti, diabetic feet, osteomyelitis, and arthritis, are described commonly and are the most common group B streptococcal infections in some reports. Necrotizing fasciitis caused by group B streptococci has been described recently. The soft tissue and bone infections may not be cured by a medical therapy alone, and surgical intervention may be necessary. For fasciitis or its possibility, surgery should be immediate.

Other manifestations of group B streptococcal infection include meningitis, peritonitis, and endo-ophthalmitis.

Group B streptococci at one time were sensitive to penicillin, ampicillin, cefazolin, erythromycin, and clindamycin. The organism remains sensitive to penicillin and ampicillin. While penicillin is the treatment of choice, that penicillin therapy produces a better outcome than other antibiotics is not clear. Because aminoglycoside may provide synergy in killing the organism, it often is added for serious infection. This 2-drug therapy is synergistic only if the organism is sensitive to aminoglycoside, making sensitivity testing important. Clinically, 2-drug therapy with penicillin and aminoglycoside has not been shown to improve the outcome over penicillin alone.

The efficacy of clindamycin and macrolides is good, but sensitivity testing must be performed before using these antibiotics because resistance is observed and appears to be increasing. Group B streptococci always are sensitive to vancomycin, and it would be the treatment of choice in the penicillin-allergic patient. Quinolones may have efficacy for group B streptococci, but little clinical experience exists. Linezolid may play a role in treating this infection, but, in the literature, no experience with treating group B streptococcal infection with linezolid exists.

Pathophysiology

S agalactiae is a gram-positive coccus that, when cultured on sheep blood agar, forms glistening gray-white colonies with a narrow zone of beta hemolysis. It is an invasive encapsulated organism capable of producing severe disease in hosts who are immunocompromised. Infection in the absence of associated comorbid medical conditions is rare. Virulence is related to the polysaccharide toxin produced by group B streptococci. Immunity is mediated by antibody to the capsular polysaccharide and is serotype-specific. Several serotypes are known—Ia, Ib, Ic, II, III, IV, V, VI, VII, and VIII. Group B streptococci colonize the vagina, gastrointestinal tract, and the upper respiratory tract of healthy humans. The portal of entry is not apparent, but possible areas include the skin, genital tract, urinary tract, and respiratory tract.

Frequency

United States

Group B streptococci are observed in neonatal sepsis in 1.8-3.2 out of 1000 live births. Early disease is observed in 1.4 out of 1000 births, while late disease is observed in 0.3 out of 1000 births. The incidence of early disease has decreased over the past decade, possibly as a result of the CDC guidelines for the prevention of neonatal colonization with group B streptococcus.

The incidence of invasive group B streptococcal infections in the nonpregnant adult population of Atlanta during the period of 1982-1983 was 2.4 cases per 100,000 population. A subsequent study conducted in Atlanta from 1989-1990 revealed an incidence rate of 4.4 cases per 100,000 population.

The incidence in adults older than 60 years rises to 18 cases per 100,000 population. This is similar to the incidence of pneumococcal sepsis.

International

The role of group B streptococci in the developing world is not well defined. Carriage rates and serotypes in women in less developed countries are similar to those observed in the industrial world. However, group B streptococci early disease in infants is not documented in less developed countries. A clear explanation for this has not been found.

Mortality/Morbidity

Group B streptococci has significant mortality in both neonates and adults. The mortality rate of group B streptococci bacteremia ranges from 9-47% in adults. The mortality rate is highest for elderly patients with comorbid medical conditions. The highest mortality rate is observed in patients with endocarditis, meningitis, and pneumonia. The high mortality rate in elderly people with group B streptococci may not reflect the organism but may reflect the predisposing condition or conditions that put the individual at risk for group B streptococcal infection.

The mortality rate of group B streptococcal infection in neonates is much less than that of nonpregnant adults. Increasing awareness of group B streptococcal infection in infants has led to improved outcome in recent years.

Postpartum group B streptococcal infection is associated with a low mortality rate because the group at risk is comprised of healthy, young or middle-aged women.

Race

The incidence of group B streptococcal infection is higher in African Americans than whites. The difference is even more striking in older African Americans. These differences probably are a result of socioeconomic differences rather than race.

Sex

• Young and middle-aged women are at risk because of obstetrical and gynecological manipulation.
• With the exclusion of pregnant women, adult group B streptococcal infection occurs in equal numbers of men and women.

Age

• The mean age for infection is 64 years.
• Bimodal distribution is well recognized, with young and middle-aged healthy women with infection secondary to obstetrical or gynecological manipulation as one group. The second group is an elderly population with group B streptococcal infection complicating preexisting illness.

CLINICAL

Section 3 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• References

History

Other than in cases of group B streptococcal infection in young and middle-aged women, a case of a healthy adult who develops group B streptococcal infection is extremely unusual. This infection almost always is associated with underlying abnormalities. Diabetes is the disease most commonly associated with group B streptococci in some series. This association, which the authors have observed over the last 25 years, is unexplained. Malignancy was the most common association in a series from an institution with a large oncology population. Cardiovascular and genitourinary abnormalities have been observed as major factors for the acquisition of group B streptococci. Other conditions associated with group B streptococcal infection in adults include neurologic deficits, cirrhosis, steroids, AIDS, renal dysfunction, and peripheral vascular disease. In elderly people aged 70 years or older, group B streptococcal infection is strongly linked to congestive heart failure and being bedridden.

Pneumonia from group B streptococcal infection is rare and has few unique features. It is observed in elderly people with diabetes and with neurologic deficits. It may be the result of aspiration of group B streptococci that colonize the upper airway. In one series, it appeared to be associated with a high rate of bacteremia.

Meningitis, a common manifestation of neonatal infection, is uncommon in adults. It almost always is associated with anatomical abnormalities contiguous with, or of, the central nervous system, usually as a result of neurosurgery.

Bacteremia with group B streptococci is a common manifestation of this organism. While a genitourinary, soft tissue, or line-related source of infection is a possibility, in most cases, no source of infection can be identified. Group B streptococcal pneumonia in elderly people has been associated with bacteremia. Group B streptococcal bacteremia without a source always raises the possibility of endocarditis. Often, the diagnosis will become obvious because endocarditis with this organism is very destructive and frequently requires valve replacement for valve insufficiency.

Skin and soft tissue infection, osteomyelitis, arthritis, discitis, and colonization of diabetic feet and decubitus ulcers are observed with group B streptococcal infection. Many of these patients are diabetic. The cause of this strong association is not clear. While medical therapy should cure many group B streptococcal infections, those involving skin, soft tissue, and bone may not be cured with antibiotics alone and may require surgical intervention.

Chorioamnionitis, endometritis, and the full spectrum of urinary tract infection (from asymptomatic bacteruria to cystitis and pyelonephritis with bacteremia) are observed with group B streptococcal infection. These are common complications in young and middle-aged women that often are related to childbirth. Urinary tract infections with group B streptococci also are observed in elderly men and women. These individuals often have diabetes or genitourinary abnormalities.

• Pneumonia in the elderly patient with neurologic deficits who is bedridden with fever, shortness of breath, chest pain, pleuritic pain, or cough
• Meningitis in the neurosurgical patient with fever, headache, nuchal rigidity, or confusion
• Bacteremia, line-related infection, sepsis, or endocarditis in the patient with fever, malaise, confusion, chest pain, shortness of breath, myalgia, or arthralgia
• Skin and soft tissue infection, osteomyelitis, or septic arthritis in patients with diabetes or in elderly patients with fever, malaise, localized pain, cellulitis, arthralgia, arthritis, or weakness
• Urinary tract infection or pelvic abscess in the postpartum woman or older man or woman with fever, dysuria, flank pain, or pelvic pain

Physical

• Pneumonia in the elderly patient with neurologic deficit who is bedridden with fever, lung consolidation, pleural effusion, tachypnea, tachycardia, or hypotension
• Meningitis in the neurosurgical patient with fever, confusion, hypotension, headache, nuchal rigidity, or changing mental status
• Bacteremia, line-related sepsis, or endocarditis in the patient with fever, murmur, evidence of an embolic event, hypotension, phlebitis, tachycardia, tachypnea, splenomegaly, or evidence of heart failure
• Skin and soft tissue infection, osteomyelitis, septic arthritis, or discitis in diabetic or elderly patients with fever, cellulitis, arthritis, arthralgia, localized pain, decubitus ulcer, vascular insufficiency of the lower extremity, back pain, wound infection, or neurologic dysfunction
• Urinary tract infection or pelvic abscess in the postpartum woman or older man or woman with fever, flank pain, pelvic pain, or abdominal pain.

DIFFERENTIALS

Section 4 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• References

Other Problems to be Considered

Bacteremia of unknown cause
Cellulitis
Chorioamnionitis
Diabetic foot
Discitis
Endocarditis
Epidural abscess
Line infection
Necrotizing fasciitis
Osteomyelitis
Septic arthritis
Soft tissue infection
Urinary tract infection

WORKUP

Section 5 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• References

Lab Studies

• Gram stain of an appropriate specimen is a useful first test. It can be an early indicator of streptococcal infection.
• Isolation of group B streptococci from blood, cerebrospinal fluid (CSF), and/or a site of local suppuration is the only means by which the diagnosis of invasive infection can be documented. Group B streptococcal antigen also may be detected in blood, CSF, and/or urine and may aid in diagnosis in certain circumstances.

Imaging Studies

• Consider pneumonia in the elderly patient with fever and other appropriate symptoms who is bedridden and has neurologic deficits. Check the chest x-ray for infiltrate or effusion.
• In the neurosurgical patient with fever and other appropriate symptoms, consider meningitis. Check the CT scan of the head, looking for abscess or contiguous infection and make sure no evidence of increased intracranial pressure is present so that a lumbar puncture (LP) can be performed safely.
• In a patient with fever, consider bacteremia, endocarditis, and line-related sepsis. Check an echocardiogram, looking for vegetation or evidence of valve destruction.
• In a patient who is elderly, bedridden, or diabetic with fever and appropriate symptoms, consider soft tissue infection, osteomyelitis, discitis, epidural abscess, wound infection, necrotizing fasciitis, and decubitus ulcer. Check the x-ray of the involved area, looking for evidence of gas or bone destruction and check the CT scan or MRI of the involved area, looking for phlegmon, abscess, or osteomyelitis.
• In a postpartum woman or older man or woman with fever and appropriate symptoms, consider urinary tract infection and pelvic abscess. Check the sonogram of the genitourinary system or pelvis, looking for evidence of genitourinary obstruction or abscess and check the CT scan or MRI for evidence of obstruction or abscess.

Procedures

• Pneumonia may require diagnostic and therapeutic thoracentesis if pleural effusion is present; empyema requires drainage by thoracentesis, chest tube, or surgery.
• Bacteremia, endocarditis, and line-related sepsis may require valve replacement because of destructive endocarditis.
• Soft tissue infection, arthritis, osteomyelitis, discitis, and epidural abscess may require diagnostic aspiration, as well as curative surgery. Necrotizing fasciitis and septic arthritis are surgical emergencies. Epidural abscess may require emergency surgery.
• Urinary tract infection or pelvic abscess may require aspiration under sonography or CT scan for a diagnostic tap to isolate an organism, relieve obstruction, or drain an abscess.

TREATMENT

Section 6 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• References

Medical Care

Group B streptococci are as sensitive to penicillin and ampicillin as they were 50 years ago. The organisms were never as exquisitely sensitive to penicillin as were group A beta-hemolytic streptococci. As a result, the initial therapy for group B streptococcal infection always has been high-dose parenteral penicillin or ampicillin.

Synergy can be demonstrated with penicillin or ampicillin plus an aminoglycoside, but this therapy is not associated with a better clinical outcome than penicillin or ampicillin alone. Testing for aminoglycoside sensitivity is important because synergy is not observed if the organism is not aminoglycoside sensitive. Also, a group B streptococcal isolate can be resistant to one aminoglycoside and sensitive to another.

While clindamycin and erythromycin were at one time uniformly active against group B streptococci, resistance has been increasing in recent years. As a result, checking the sensitivity before using these agents against group B streptococci is important. Oral clindamycin remains an excellent agent to follow a course of parenteral therapy for bone, soft tissue, and lung infections.

Because of possible resistance with clindamycin, vancomycin remains the initial treatment of choice for group B streptococcal infection in the penicillin-allergic individual. Penicillin, ampicillin, or vancomycin remains the treatment of choice for endocarditis. While vancomycin may be adequate in group B streptococcal meningitis in a penicillin-allergic individual, skin testing and desensitization for penicillin therapy might be considered. Penicillin has not been demonstrated to be superior to vancomycin for endocarditis with group B streptococcus infection.

The efficacy of quinolones for group B streptococci has not been well studied, although the isolates often are sensitive.

Similarly, linezolid, a new antibiotic with efficacy for aerobic gram-positive cocci, should have activity against group B streptococci. It is available in parenteral or oral form. However, no clinical data exist concerning the use of linezolid for group B streptococci at this time.

Surgical Care

Surgical opinion and intervention is important.

• Pneumonia may require drainage of empyema.
• Endocarditis, bacteremia, and sepsis may require heart valve replacement.
• Soft tissue infection, septic arthritis, osteomyelitis, discitis, and epidural abscess often require surgery combined with parenteral antibiotics for cure.
• Necrotizing fasciitis and septic arthritis are surgical emergencies.
• Epidural abscess may require emergency surgery.
• Urinary tract infection and pelvic abscess may require relief of genitourinary obstruction and abscess drainage for cure.

Consultations

Group B streptococcal infection may require a variety of professionals for the best outcome. An infectious disease specialist often is helpful in choosing the antibiotic and duration of therapy. Appropriate surgical support is critical for a good outcome.

• Pneumonia may require a pulmonary specialist or surgeon to drain an empyema.
• Bacteremia, endocarditis, and line-related sepsis may require a cardiovascular surgeon for valve replacement secondary to endocarditis.
• Soft tissue infection, osteomyelitis, epidural abscess, discitis, and arthritis will require a rheumatologist for arthrocentesis and an orthopedic surgeon or neurosurgeon for possible surgical opinion and intervention.
• Urinary tract infection or pelvic abscess may require a urologist or gynecologist for surgical opinion and possible relief of obstruction and drainage of abscess.

MEDICATION

Section 7 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• References

The goals of pharmacotherapy are to reduce morbidity and to prevent complications.

Drug Category: Antibiotics

Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting. Therapy should begin immediately after blood cultures are obtained.

FOLLOW-UP

Section 8 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• References

Deterrence/Prevention

• Both chemoprophylaxis and immunoprophylaxis have been studied in neonates.
• While vaccine therapy to prevent group B streptococcal infection in women of childbearing age has been studied, no Food and Drug Administration (FDA)–licensed vaccines are available. Investigational vaccine studies are in early stages.
• Chemoprophylaxis has been shown to be efficacious in neonates. A significant decline in neonatal infections over the past decade may be a result of this national standard.
• The only approach to prevent group B streptococcal infection in the nonpregnant adult is to adhere to infection control practices because a significant number of these infections are nosocomial. What percent of these infections are preventable remains to be determined because single nosocomial cases are common but a clustering of cases is rare.

Complications

• Group B streptococcal infection in healthy women usually is amenable to therapy without major sequelae.
• Neonatal infection, which still has significant morbidity and mortality, has become less common and has a better outcome as a result of chemoprophylaxis and early recognition of the infected infant.
• Group B streptococcal infection in the nonpregnant adult carries a high morbidity and a high mortality rate even with early and appropriate therapy. Having a high clinical suspicion, starting early therapy after cultures are obtained, and having the patient receive an appropriate surgical opinion and adequate surgical intervention when necessary are important.

Prognosis

• The prognosis for healthy women is excellent. For neonates, prognosis is better than in the past but still carries significant morbidity and mortality. Nonpregnant adults with group B streptococcal infection are elderly, with comorbid conditions. Therefore, high mortality rates are inherent in those who develop infection.
• The nonpregnant adults who survive group B streptococcal infection should have a good prognosis from the infection; however, they continue to have the comorbidity that put them at risk for infection and therefore are an extremely ill group of patients.

MISCELLANEOUS

Section 9 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• References

Medical/Legal Pitfalls

• Having an early clinical suspicion for group B streptococcal infection is important.
• Early and appropriate parenteral antibiotics continued for a long time and surgical intervention adequate to cure the infection are critical.
• • Relapsing infection because of inadequate antibiotic or inadequate surgery can be observed.
  • Recurrent infection can be observed, even with satisfactory medical and surgical care.

ACKNOWLEDGMENTS

Section 10 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• References

The authors and editors of eMedicine gratefully acknowledge the contributions of previous coauthor Mohamad Ossiani, MD, to the development and writing of this article.

REFERENCES

Section 11 of 11

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• References

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• Schuchat A. Group B streptococcus. Lancet. Jan 2 1999;353(9146):51-6. [Medline].
• Schwartz B, Schuchat A, Oxtoby MJ. Invasive group B streptococcal disease in adults. A population-based study in metropolitan Atlanta. JAMA. 1991;266:1112-4. [Medline].
• Trivalle C, Martin E, Martel P. Group B streptococcal bacteraemia in the elderly. J Med Microbiol. 1998;47:649-52. [Medline].
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Article Last Updated: Mar 24, 2006