Group B streptococcus (GBS), also known as Streptococcus agalactiae, causes serious, life-threatening dysfunctions such as bloodsteam infections and meningitis in newborns. According to Clinical Infectious Diseases, this same organism causes a variety of infections in older adults and those with chronic medical conditions, especially diabetes mellitus. Skin and osteoarticular infections and pneumonia can also be caused by GBS, along with meningitis and endocarditis, which may pose serious morbidity and mortality risks. To treat it, penicillin is the drug of choice, but other antibiotics are also available.
Prophylactic Antibiotics During Labor
Group B streptococci can be transmitted from a mother to her baby during labor. In 2002, the Centers for Disease Control and Prevention recommended intravenous antibiotic prophylaxis for pregnant women who have vaginal-rectal colonization with group B streptococci at 35 to 37 weeks gestation, since clinical trials showed that antibiotics given to women in labor drastically reduced invasive GBS infections in neonates.
Women without penicillin allergy should be given aqueous penicillin G, 5 million units intravenously as the first dose, then 2.5 million units intravenously every 4 hours until delivery. An alternative regimen is ampicillin, a first dose of 2 grams (g) intravenously, then 1 g intravenously every four hours until delivery.
Women with a high risk of anaphylaxis should be given either 900 milligrams (mg) of clindamycin intravenously every eight hours until delivery, or 500 mg of erythromycin intravenously every six hours until delivery.
Penicillin
According to Harrison's Principles of Internal Medicine, group B streptococci, like group A streptococci are susceptible to penicillin G, ampicillin and other penicillins, including oxacillin. However, it takes higher doses of penicillin to kill group B streptococci.
Alternative Antibiotics
According to Clinical Infectious Diseases, vancomycin, chloramphenicol and most cephalosporins are effective alternatives. Aminoglycosides have poor activity against GBS when used alone but are effective in combination with penicillin G or ampicillin.
Newer Antibiotics
Diagnostic Microbiology Infectious Diseases states tigecycline, a member of the glyclcycline class of antibiotics, was active against the most prevalent pathogens in diabetic foot infections, including GBS.
According to the journal Antimicrobial Agents and Chemotherapy, linezolid, a type of oxazolidinone, was active against all streptococci tested, including GBS.
The International Journal of Antimicrobial Agents states ceftobiprole, a cephalosporin, was highly active against penicillin-resistant S. pneumoniae and group B streptococci.
According to the journal Antimicrobial Agents and Chemotherapy, telavancin, a type of novel lipoglycopeptide, was highly active against GBS.
References
- "Antimicrobial Agents and Chemotherapy"; In Vitro Activity of Telavancin; WTM Jansen; Sept 2007
- "Clinical Infectious Diseases"; Group B Streptococcal Disease; Monica M. Farley; July 2001
- "Diagnostic Microbiology Infectious Disease"; In vitro activity of tigecycline; PJ Peterson; Apr 2010
- "Antimicrobial Agents and Chemotherapy"; Comparative In Vitro Activities of Linezolid; Carmen Betriu; July 2000
- International Journal of Antimicrobial Agents: Comparative in vitro activity of ceftobiprole against Gram-positive cocci; C. Betriu; May 27, 2010
