Group B streptococcus is associated with pneumonia and meningitis in infants exposed to the bacteria during labor. The American College of Obstetricians and Gynecologists advises that all women be screened for GBS by vaginal and rectal swabs at 35 to 37 weeks, and for intravenous antibiotics to be administered if the test is positive, or if the test has not been done. This decreases the risk of the baby contracting GBS to 1:4000.
Penicillin G
When a mother tests positive for GBS or has not been tested, the safest course of action is the administration of intravenous penicillin G. Mothers delivering at a hospital or freestanding birth center who are GBS-positive are advised to come to that site early in labor to assure that there is time to administer the antibiotics before delivery, and mothers delivering at home should make arrangements to come to a hospital's emergency department solely to receive these antibiotics when labor begins, before returning home for delivery. Intravenous penicillin G has a potential for an allergic reaction even if the mother has never had a prior problem, so administration in a hospital, where medications, equipment and staff are available to treat a respiratory emergency is necessary.
Ampicillin
When ampicillin is substituted for penicillin the reduction in the risk to newborns is unchanged according to a Cochrane Review, and women allergic to either one will react to both. Giving either medication to the mother by mouth will not lower the risk of GBS infection in the infant, but oral ampicillin given to a baby after birth can be used to prevent infection in cases where the mom has had less than two hours between receiving the medication and birth. However, if ampicillin is given to the mother during labor, instead of penicillin G, the bacteria infecting the child will be resistant to this drug, according to research by Drs. Karen M. Puopolo of Harvard University and Eric C. Eichenwald from Baylor College of Medicine, as reported in the May 2010 issue of "Pediatrics." For this reason, these researchers join the American Academy of Pediatrics in recommending penicillin G as the drug of choice for GBS positive moms.
Erthromycin and Clindamycin
When a mother is allergic to penicillin two other antibiotics are options: erythromycin and clindamycin. Either can administered safely, but 22 percent of GBS cultures prove resistant to the more commonly used erythromycin according to a study by Brown University's Judith S. Heelan, Ph.D., reported in the March 2004 issue of the "Journal of Clinical Microbiology." This occurs because a woman allergic to penicillin is likely to have had multiple prescriptions of erythromycin for ear, respiratory and throat infections by the time she reaches her childbearing years. Group B strep lives in the intestinal and bladder of many women throughout their lives and those bacteria that survive are erythromycin resistant. The American College of Obstetricians and Gynecologists advises sensitivity testing be done on the sample taken from all women with a penicillin allergy.
References
- American College of Obstetricians and Gynecologists: GBS, Compliance with Guidelines
- Cochrane Review; Intrapartum Antibiotics for Known Maternal Group B Streptococcal Colonization; Arne Ohlsson and Vibhuti S Shah; April 2009
- "Pediatrics"; No Change in the Incidence of Ampicillin-Resistant, Neonatal, Early-Onset Sepsis Over 18 Years; Karen M. Puopolo, MD, Ph.D. and Eric C. Eichenwald, M.D.; May 2010
- "Journal of Clinical Microbiology"; Resistance of Group B Streptococcus to Selected Antibiotics, Including Erythromycin and Clindamycin; J. Heelen, Ph.D. et al; March 2004
