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MS WordPerinatologist Corner - C.E.U/C.M.E. Modules
Group B Streptococcal Disease in the Perinatal Period
Sponsored by The Indian Health Service Clinical Support Center
6. Other Clinical Pearls: Frequently Asked GBS questions
Q. For how many weeks is the information from the GBS cultures valid?
A. There is a 95 % likelihood that a negative GBS culture will remain negative for 4-5 weeks. Therefore if your patients goes postdates, or it has been longer than 5 weeks between culture and delivery, then the culture should be repeated. (Yancey et al)
Q. How should the cultures be obtained?
A. This involves swabbing the lower vagina and rectum (i.e., through the anal sphincter). Cultures should not be collected by speculum examination because lower vaginal as opposed to cervical cultures are recommended. (CDC 2002). Specimens should be placed in a nonnutritive transport medium (e.g., Amies or Stuart's without charcoal). Specimen labels should clearly identify that specimens are for group B streptococcal culture.
Q. My patient had a negative GBS culture that was performed
properly <5 weeks ago and she is in labor now. She has had ROM > 18
hours
and doesn’t have a fever, but I think she may fit into the risk
based treatment arm now. What should I do?
A. From the perspective of GBS, her risk if very small. There has been a fair amount of confusion about this among providers.
On the hand, the guidelines are quite clear on this. If she is GBS negative, then there is no need to treat this patient.
Q. A patient comes in labor. There are no culture results available. What do I do?
A. The patient should receive intrapartum antibiotic prophylaxis based on:
Risk factors (< 37 weeks, ROM > 18hrs, or >100.4 degrees F)
Other patients that should receive treatment without a culture are:
- History of previous infant with invasive GBS
- History of GBS UTI in this pregnancy
Surprisingly, in a multicenter trial of programs with screening programs implemented, this scenario happens less than 5% of the time. (Schrag et al)
Q. What if a patient with a long labor receiving GBS prophylaxis develops a fever?
A. The antibiotic coverage should be broadened according to the clinical scenario.
- For patients progressing well in labor and anticipating a vaginal delivery, then penicillin plus and aminoglycoside has stood the test of time.
- For cesarean delivery patients, clindamycin or metronidazole should be added to improve the anaerobic coverage. Using penicillin and gentamicin has an unacceptably high failure rate with cesarean delivery.
Q. Name 3 common scenarios which are often mistaken to need prophylaxis, e.g.,
which patients should NOT receive GBS prophylaxis.
A. 1.) Positive GBS culture in a previous pregnancy
A 2.) Panned cesarean delivery performed in absence of labor or ROM
A 3.) Negative GBS culture within 5 weeks in this pregnancy and now presenting with risk factors (< 37 weeks, ROM > 18hrs, or >100.4 degrees F)
Q. My patient was a GBS carrier in her last 2 pregnancies. Should I re-screen her or just treat her in labor?
A. You should re-screen her. GBS carriage can come and go. The rare exceptions are the patients who had a previous infant with invasive GBS disease, e.g., bacteremia or meningitis. These latter women will need treatment in labor no matter what, so they don’t need to be screened. So once positive for invasive GBS disease, then the patient maintain an ‘at risk status’.
Q. Do women who have GBS bacteriuria during this pregnancy need a vaginal and rectal screening done at 35-37 weeks too?
A. No, they just need intrapartum antibiotic prophylaxis
Q. My patient doesn't want an IV in labor. Can I just treat her with oral or IM penicillin?
A. Those methods have not been satisfactorily been studied and they are not recommended.
Preterm labor
Q. My patient is less than 37 weeks has regular uterine contractions
or rupture
of membranes
and has a positive GBS culture. What do I do?
A. Begin treatment with the appropriate intrapartum prophylaxis.
Q. My patient is less than 37 weeks has regular uterine
contractions or rupture
of membranes
and a GBS culture hasn’t been done yet. What do I do?
A. Obtain a vaginal and rectal swab for GBS culture and begin the appropriate intrapartum prophylaxis for at least 48 hours or until the GBS culture results return.
Q. My patient is less than 37 weeks has regular uterine
contractions or rupture
of membranes
and has a negative GBS culture done within 5 weeks. What do
I do?
A. There is no need for intrapartum prophylaxis.
Q. My patient is less than 37 weeks has rupture
of membranes
but not regular uterine contractions. What do I do?
A. #1. If she has a positive GBS culture, then treat her for 48 hours.
A. #2 If she hasn’t had a GBS culture, then obtain a rectovaginal swab for GBS and treat with the appropriate intrapartum prophylaxis until the GBS culture comes back.
Q. My patient is less than 37 weeks has regular uterine
contractions but no rupture
of membranes.
She has received the appropriate intrapartum prophylaxis for
48 hours, but is still undelivered. What do I do?
A. #1. Obtain a follow-up culture. If it still positive and delivery is anticipated, then treat again for 48 hours.
A. #2. Obtain a follow-up culture. If it still negative, then discontinue antibiotics
Q. What if the patient above goes into labor soon after her treatment is finished?
A. Then treat with the appropriate intrapartum prophylaxis in labor, too.
If the culture was positive and the labor stops, then stop the antibiotics and resume them when labor resumes.
Allergies to medication
Q. My patient isn’t sure if she is penicillin allergic. Should she be skin tested?
A. Skin testing can be awkward to complete in a timely fashion, plus it doesn’t tell you about cephalosporin allergy. History is the best way to get appropriate information. Only about 4 in 10,000 to 4 in 100,000 people develop anaphylaxis on exposure to penicillin. On the other hand, mild reactions are much more common – about 1 in 10 people, e.g., headache or nausea.
For those at low risk of immediate hypersensitivity, then cefazolin is the drug of choice. Penicillin and cephalosporins do have a cross-reactivity, but only 10% of women who have penicillin allergies will actually have allergies to cephalosporin. Luckily most cross reactions are mild, e.g., rash.
Q. My patient has had immediate hypersensitivity or anaphylaxis to penicillin. What are my options?
A. The first option is to actually test the susceptibility of the GBS isolate to see if erythromycin or clindamycin might be reasonable alternatives. Since 1996 about 15% of the isolates are resistant to clindamycin and 25% are resistant to erythromycin.
If the isolate is resistant to both clindamycin and erythromycin, the patient should be treated with vancomycin.
Dosing intervals
Q. Let me get this straight now, I can use any of 6 drugs.
How can I keep the dosing intervals straight?
A. You may want to create some pre-printed orders that spell out the options. In the meantime the intervals for the main two agents are:
The intervals for the others agents are:
- penicillin is q 4 hours (penicillin G, 5 million units initial dose, then 2.5 million units q 4 hours until delivery)
- cefazolin is q 8 hours (cefazolin, 2 g initial dose, then 1 g every 8 hours until delivery)
- ampicillin is q 4 hours (same dosing interval as penicillin) (ampicillin, 2 g initial dose, then 1 g intravenously every 4 hours until delivery)
- erythromycin is q 6 hours (erythromycin, 500 mg intravenously every 6 hours until delivery)
- clindamycin is q 8 hours (clindamycin, 900 mg intravenously every 8 hours until delivery)
- vancomycin is q 12 hours (vancomycin, 1 g intravenously every 12 hours until delivery)
Induction of labor
Q. My patient was a GBS carrier in her last 2 pregnancies and is a GBS carrier again. Should I induce her so she can be assured of getting her antibiotics at least 4 hours before delivery?
A. Induce labor for standard obstetric indications, regardless of GBS status. Although 4 hours provides optimal benefit, shorter intervals also do provide some benefit. GBS carriers should be encouraged to come in early in labor.
Invasive procedures
Q. Can I use a scalp electrode in a GBS carrier?
A. Do not change any obstetric practices based on the patient’s GBS status. There are some invasive obstetric procedures associated with increased risk of infection. Use good clinical judgment to determine if the benefit of the intervention outweighs the risk. The same judgment should apply to GBS carriers.
Q. Can you strip the membranes in a GBS carrier?
A. The studies of membrane striping were done regardless to the GBS status. There has been no significant increase in chorioamnionitis or postpartum infection from membrane stripping.
By the way, routine use of sweeping of membranes from 38 weeks of pregnancy onwards does not seem to produce clinically important benefits. (Boulvain et al - Cochrane Library) When used as a means for induction of labour, the reduction in the use of more formal methods of induction needs to be balanced against women's discomfort and other adverse effects.
Cesarean delivery
Q. My patient is planning a repeat cesarean delivery. Should I even screen her for GBS?
A. Yes, she may rupture her membranes or go into labor prior to her planned cesarean delivery and might need prophylaxis.
Q. My patient is a GBS carrier and is about to receive an elective cesarean delivery. She is afebrile, not in labor and has not ruptured her membranes. Should I give antibiotic prophylaxis?
A. No. On the other hand, if she is GBS positive in labor or has ROM, then yes she should receive antibiotic prophylaxis.
Q. My patient is a GBS carrier and wants to avoid any risk to her fetus at all. Should I perform a cesarean delivery to avoid GBS disease?
A. Cesarean delivery should be performed for standard obstetric indications. GBS carriage is not an indication for cesarean delivery. Intrapartum antibiotic prophylaxis is the appropriate intervention for GBS carriage, or for standard GBS risk factors, if culture results aren’t available.
Public Health
Q. Aren’t we going to create more antibiotic resistance by using the screen and treat method of GBS prevention?
A. Bacterial resistance is always a concern, so you should not overtreat and you should use the narrowest spectrum possible, e.g., Penicillin.
As it turns out, if you use the screening based method, then about 24% of women will get antibiotics in labor. That is just about the same percent of women who will get antibiotics using the risk-based method.
Q. I heard that while we have decreased early onset GBS disease by 70% since the early 1990’s that we are increasing other neonatal infections. Should I really begin a process whereby I ultimately give 25% of all my pregnant patients antibiotics?
A. While the incidence of early onset GBS disease has decreased since the early 1990’s, it has plateaued recently, hence the new guidelines.
There is conflicting data on the incidence of other infections in neonates, e.g., E. coli. There is concern about ampicillin resistant E. coli in very-preterm, or very low birth weight infants, which should be monitored. (Stoll et al.) At this point there is no concern in the term population.
In the meantime, it is best to use the narrowest spectrum possible, e.g., penicillin rather than ampicillin, and do not use intrapartum prophylaxis when not indicated by the guidelines, e.g., in the GBS negative woman with ROM > 18 hours
Q. Why don’t we just treat women with GBS with oral antibiotics for their whole pregnancy to just get rid of GBS entirely?
A. Oral therapy has not been found to effective to eliminate GBS carriage.
Q. Why do we treat women with GBS bacteriuria remote from delivery if oral antibiotics don’t treat GBS carriage?
A. GBS bacteriuria is a bone fide urinary tract infection. We treat it to avoid ascending urinary tract infection. They should also receive intrapartum prophylaxis.
Q. If a 1st generation cephalosporin, like cefazolin, is good, wouldn’t a 2nd or 3rd generation cephalosporin be better?
A. No, the other generation cephalosporins are not as active against GBS, as the 1st generation. In addition, you would unnecessarily increase the incidence of gram positive antibiotic resistance.
Q. Is there any benefit of GBS intrapartum prophylaxis for the laboring woman, herself?
A. Yes, they have 20% less incidence of chorioamnionitis and maternal endomyometritis.
Q. Which is more important to the infant, to have gotten two doses in utero, or to have had at least 4 hours of exposure to GBS intrapartum prophylaxis?
A. You should all GBS carriers to come in as early in labor as possible. The patient can be her own advocate. When she arrives she should say, "I am beta strep positive, I need my antibiotics." Based on the use of penicillin or ampicillin, the emphasis should be to treat for at least 4 hours, rather than the 1996 emphasis for at least 2 doses. (Lin et al)
Q. Is there a role for antepartum GBS prophylaxis?
A. The revised guidelines emphasize there is no role for antepartum treatment of GBS carriage. On the other hand, GBS urinary tract infections should be treated when diagnosed.
Q. How can I best implement and monitor this program?
A. It is best to involve all the possible parties from the outset: clinic staff, family physicians, laboratory, L/D staff, medical records, midwives, OB/GYNs, and pediatrics.
- You should also monitor the program on a periodic basis. Neonatal GBS infection will hopefully be such a rare event, that it might be more meaningful to follow the percent of maternal cultures that are positive for GBS. The rate should be in the range of 25%.
- Another way to monitor the program’s effectiveness is to perform periodic chart review to determine how many patients for whom intratpartum prophylaxis was indicated, actually received it.
- Another way to monitor is follow the clinical outcomes and length of stay for those infants from mothers with GBS carriage.
Lab methods
Q. How do I know if my lab is performing the cultures properly?
A. You should involve your laboratory colleagues in the implementation of the GBS prevention program from the very start. The result from the selective media for GBS should be GBS present, or GBS not present.
A couple of pearls that might indicate that the laboratory or collection methods may need to be re-evaluated are:
- If you see lab reports with lactobacilli or Staph epidermidis - that may mean the lab is not using selective media
- If your overall rate of positive GBS cultures is 5-7 %, like some sexually transmitted diseases - The rate of GBS carriage from a wide number of settings is approximately 25%, so if you rate widely varies from 25%, then you may want to evaluate if the providers are doing both vaginal AND rectal sampling? Is selective media being used in the lab or are they performing direct plating?
- If you explore these or other issues and you have further questions, then you should consult your local epidemiology department.
Q. Which patients should NOT receive GBS prophylaxis
A #1. Previous pregnancy with a positive GBS culture, unless it is positive again this pregnancy
A #2. Planned cesarean delivery performed in absence of labor or ROM
A #3. Negative GBS culture in late gestation of this pregnancy and now presents with risk factors
Q. My patient was a GBS carrier in her last 2 pregnancies. Should I re-screen her or just treat her in labor?
A. You should re-screen her. GBS carriage can come and go. The rare exceptions are the patients who had a previous infant with invasive GBS disease, e.g., bacteremia or meningitis. These latter women will need treatment in labor no matter what, so they don’t need to be screened.
Q. My patient doesn't want an IV in labor. Can I just treat her with oral or IM penicillin?
A. Those methods have not been satisfactorily been studied and they are not recommended.
