eMedicine Specialties > Infectious Diseases > Bacterial Infections

Streptococcus Group B Infections: Treatment & Medication

Author: Christian J Woods, MD, Fellow, Infectious Diseases Program, Department of Pulmonary Critical Care, Georgetown University Hospital, Washington Hospital Center
Coauthor(s): Charles S Levy, MD, Associate Professor, Department of Medicine, Section of Infectious Disease, George Washington University School of Medicine
Contributor Information and Disclosures

Updated: Nov 11, 2009

Treatment

Medical Care

Group B streptococci are uniformly sensitive to penicillin and ampicillin. Although resistance to penicillin or ampicillin has not be documented, some isolated have shown minimum inhibitory concentrations (MICs) approaching the upper limits of susceptibility for some of the beta-lactam agents.⁵ Group B streptococci have never been as exquisitely sensitive to penicillin as group A beta-hemolytic streptococci; therefore, the initial therapy for group B streptococcal infection has always been high-dose parenteral penicillin or ampicillin.

Penicillin or ampicillin plus an aminoglycoside has demonstrated synergy but has not been shown to provide 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 sensitive to aminoglycosides. Keep in mind that given 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. One large study that examined the susceptibility patterns of over 4800 group B streptococcal isolates found that 32% were resistant to erythromycin, 15% were resistant to clindamycin, and 99% of clindamycin-resistant strains were also resistant to erythromycin.⁵ As a result, sensitivity testing is important before these agents are used. Oral clindamycin remains an excellent agent to follow a course of parenteral therapy for bone, soft-tissue, and lung infections if the isolate is susceptible.

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

While fluoroquinolones appear to have efficacy against isolates of group B streptococci, resistance to fluoroquinolones has recently been reported.⁸

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 studies have evaluated linezolid in group B streptococcal infections.

Surgical Care

Surgical opinion and intervention is important.

• Pneumonia may require empyema drainage.
• 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 various consultations for an optimal outcome. An infectious disease specialist is often helpful in choosing the antibiotic and duration of therapy. Appropriate surgical support is critical for a good outcome.

• Pneumonia may require a pulmonologist or surgeon for empyema drainage.
• Bacteremia, endocarditis, and line-related sepsis may require a cardiovascular surgeon for valve replacement.
• Soft-tissue infection, osteomyelitis, epidural abscess, discitis, and arthritis 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 abscess drainage.

Medication

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

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.

Penicillin G (Pfizerpen)

Interferes with synthesis of cell wall mucopeptide during active multiplication, resulting in bactericidal activity against susceptible microorganisms. Penicillin remains the drug of choice for group B streptococcal infection.

Cefazolin (Ancef, Kefzol, Zolicef)

First-generation semisynthetic cephalosporin that arrests bacterial cell wall synthesis, inhibiting bacterial growth. Primarily active against skin flora, including Staphylococcus aureus. Typically used alone for skin and skin structure coverage. IV and IM dosing regimens are similar.
Cefazolin is alternative therapy to penicillin for group B streptococcal infection. Cefazolin would not be effective for meningitis.

Vancomycin (Vancocin)

Potent antibiotic directed against gram-positive organisms. Useful in the treatment of septicemia and skin structure infections. Indicated for patients who cannot receive or who have failed to respond to penicillins and cephalosporins or who have infections with resistant staphylococci.
To avoid toxicity, the current recommendation is to assay vancomycin trough levels after the third dose drawn 0.5 h prior to next dosing. Use creatinine clearance to adjust dose in patients diagnosed with renal impairment.
May need to adjust dose in renal impairment. Vancomycin is the initial treatment of choice for group B streptococcal infection in the penicillin-allergic individual.

Telavancin (Vibativ)

Lipoglycopeptide antibiotic that is a synthetic derivative of vancomycin. Inhibits bacterial cell wall synthesis by interfering with polymerization and cross-linking of peptidoglycan. Unlike vancomycin, telavancin also depolarizes the bacterial cell membrane and disrupts its functional integrity. Indicated for complicated skin and skin structure infections caused by susceptible gram-positive bacteria, including Staphylococcus aureus (both methicillin-resistant and methicillin-susceptible strains), Streptococcus pyogenes, Streptococcus agalactiae, Streptococcus anginosus group, and Enterococcus faecalis (vancomycin-susceptible isolates only).

Gentamicin (Gentacidin, Garamycin)

Aminoglycosides show synergy when used with penicillin for group B streptococcus. In neonates, the ill patient with sepsis and in certain situations, such as endocarditis, adding an aminoglycoside as a second drug may be helpful. The possible benefit must be weighed against the toxicity of renal and eighth nerve dysfunction, particularly in elderly people. The benefit of 2-drug therapy for group B streptococci has not been proven in terms of a better clinical outcome compared to penicillin therapy alone. The aminoglycoside needs to be tested against the isolate because only sensitive isolates can provide synergy.

Clindamycin (Cleocin)

Not for use as initial therapy because a small percent of group B streptococci will be resistant to clindamycin. Should not be used for endocarditis, bacteremia, or meningitis. If bacteria are sensitive, it can be used for pneumonia, osteomyelitis, and soft tissue infection. May also be useful as oral therapy to follow a course of parenteral therapy or if access becomes an issue.

• Search for CME/CE on This Topic »