GBS Infection Prevention

GBS Infection Prevention

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Disease & Incidence:

1)   Disease

a.     Maternal: UTI, Intrauterine Infection or Inflammation (Triple-I; also sometimes referred to as chorioamnionitis and/or endometritis), Sepsis and (rarely) meningitis

b.     Fetal:

                                               i.     Early-Onset

1.     <24hrs usually, but defined as <1wk

2.     Due to transmission from colonization in vagina/rectum during delivery

3.     90% of neonatal GBS infections

4.     Sepsis, Pneumonia, Meningitis

                                              ii.     Late-Onset

1.     >1wk

2.     Bacteremia without a focus, FUO, Meningitis, Septic Arthritis, Osteomyelitis, Cellulitis

2)   Prevalence

a.     Group B Strep (Streptococcus agalactiae) colonizes 10-30% of pregnant women.

b.     EO GBS was 1.7 per 1000, screening has reduced this 80% to 0.4 per 1000 cases.

c.      No changes in Late-Onset GBS

3)   Risk Factors

a.     Maternal +GBS, GA <37wks, Intra-amniotic infection, Young maternal age, Black race, Mom had previous GBS-infected newborn

Screening

1)   Population

a.     All women 35-37wks GA

                                               i.     May skip if management unchanged with a positive test

1.     +GBS in urine this pregnancy

2.     Previous newborn with GBS infection

b.     Women at risk of delivering earlier

                                               i.     Preterm Labor

                                              ii.     PPROM

                                            iii.     Sample is good for 5wks; should recollect later if expires

2)   Procedure

a.     Swab posterior vagina and posterior fourchette

b.     Swab the rectum (through anal sphincter)

c.      Place swab in non-nutritive transport medium

                                               i.     Stuart or Ames media w/out charcoal

                                              ii.     Samples may remain viable for several days at room temp but recovery of isolates declines over 1-4d, worse at elevated temps leading to false-neg results

Prophylaxis

1)   Women with +GBS:

a.     Urine positive this pregnancy

b.     Infection in prior neonate

c.      Positive culture this pregnancy within the last 5 weeks

d.     GBS unknown and

                                               i.     Prolonged ROM >18hrs

                                              ii.     Preterm Delivery <37wks

                                            iii.     Chorio or Temp >100.4F

                                            iv.     No risk factors, but positive NAAT – risk factors trump NAAT

e.     No GBS Prophylaxis:

                                               i.     Planned C-section w/out ROM or Labor

1.     At any gestational age

2.     Known GBS+

                                              ii.     They get Abx PPx per surgical management

2)   Antibiotics

a.     Penicillin G IV 2.5-3 million U q4h until delivery

                                               i.     Ampicillin IV also acceptable 2g initial dose then 1g q4h until delivery

                                              ii.     Erythromycin no longer recommended

1.     Resistance increasing (~32%)

                                            iii.     PCN allergy

1.     Not severe:

a.     Cefazolin 2g IV initial, then 1g IV q8hr until delivery

2.     Severe: (Anaphylaxis, Angioedema, Resp Distress, Urticaria

a.     Risk of anaphylaxis is 4/10,000-4/100,000

b.     May give Clindamycin

                                                                                                     i.     Must do D-zone test

                                                                                                    ii.     GBS not resistant (neg D-zone test)

1.     Erythromycin induces production of erythromycin ribosomal methylase, which also provides resistance against clindamycin

2.     A/w clindamycin failure

                                                                                                  iii.     Clindamycin IV 900mg q8h until delivery

c.      If cannot give Clindamycin

                                                                                                     i.      Vancomycin 1g IV q12hr until delivery

Obstetrical Management

1)   No data on FSE, scalp pH, or membrane stripping in GBS+

Newborn management

1)   If sepsis, give full evaluation and abx

a.     Abx to cover E Coli and gram-, GBS

b.     Full eval: BCx, CBC/diff, CXR, LP

2)   If maternal chorio, give limited evaluation and abx

a.     Limited eval: BCx, CBC/diff

3)   If mom received >4hrs GBS abx prior to delivery, obs x48hrs

a.     If <4hrs GBS abx, but >37wks GA and <18hrs ROM, obs x48hrs

b.     If <4hrs GBS abx, and either <37wks GA or >18hrs ROM obs x48hrs and limited evaluation

 

Image 1: GBS is susceptible to both erythromycin and clindamycin. There are full circles ('zones of inhibition') around each antibiotic-impregnated tab. Erythromycin is on the left, clindamycin is on the right.

 

Image 2: GBS is resistant to erythromycin, as the bacteria can grow right up to the erythromycin, so a D-zone test is required. Here, there is a full circle around the clindamycin, so this is a negative D-zone test, in that there is no erythromycin-induced clindamycin resistance. 

 Image 3: Here, again, the GBS is resistant to erythromycin, so a D-zone test is required. However, you can see that there isn't a full circular zone of inhibition around the clindamycin - the zone is D-shaped. This is a positive D-zone test, indicating that there is erythromycin-induced clindamycin resistance in this GBS isolate. Recall that, generally, when a test is reported as being positive, that indicates that the test result is abnormal.

Images from Khan Academy.