31 Streptococcal and staphylococcal infections

Simple infections pending antibiotic sensitivities:

Found in 12–37% of ♀ attending GUM clinics. Usually not pathogenic (except in pregnancy) but associated with bacterial vaginosis.

Carriage rate is 6–28%. Intra-amniotic infection and postpartum endometritis if heavily colonized. ~35% of babies of carriers become colonized, with ~1% developing invasive neonatal infection with an incidence of 1 in 2000 births. GBS is the most frequent cause of any severe infection in infants aged <7 days. Septicaemia, meningitis, pulmonary infection, and shock may follow in up to 50% of infected infants with a mortality of 6% if full term and 18% if preterm.

Risk factors for neonatal infection are:

In the UK, women identified with these risk factors are offered intrapartum antibiotics to prevent neonatal infection (Box 31.1). Recommended regimen is iv benzyl penicillin 3g (5mu) at onset of labour, then 1.5g (2.5mu) 4 hourly until delivery. Clindamycin 900mg should be given iv 8 hourly to those allergic to penicillin.

Practice varies worldwide, e.g. US guidelines recommend that all women are screened (vaginal/rectal swabs) at 35–37 weeks for GBS and prophylactic intrapartum antibiotics offered to those testing positive (or not tested). This results in 30–50% of women receiving IV prophylactic antibiotics during labour. Risk-factor-based approach is estimated to ↓ early onset of GBS disease of the neonate by 50–69%, while prophylaxis based on routine swabs may ↓ it by 86%.

Urethral colonization in 38–46% of ♂ attending GUM clinics. GBS may cause balanitis, usually mild but rarely progressing to cellulitis. GBS also occasionally implicated in balanitis.

Vaginal carriage rate is ~10%.