Staphylococcus aureus (SA) is a significant cause of community and hospital acquired infections. SA is carried by approximately 30% of healthy adults. Similar carriage rates have been reported in very young infants and newborns. Previous studies have suggested that the source of SA carriage in young children is SA carried by their mothers. Possible modes of transmission from mother to child are transmission during passage through a colonized birth canal, through lactation and/or close contact.

We aim to 1) Define the route of transmission between mother and newborn. 2) Assess the dynamics of S. aureus carriage during the first years of life and specifically determine risk factors for becoming a persistent carrier of S. aureus

Design:

prospective cohort study which will examine the risk of exposure to S. aureus carrier mother on the outcome: S. aureus carriage by newborns following delivery and at discharge.

1. Risk of vertical transmission during delivery will be assessed by comparing a cohort of newborns to vaginal S. aureus carrier mothers to a cohort of newborns of mothers not carrying S. aureus vaginally.
2. Risk of horizontal transmission during the first days of life will be assessed by following a cohort of newborns not colonized on delivery day. The main exposure of interest is maternal nasal SA carriage.Target populations: 300 mother - newborn pairs.

Setting:

Sheba Medical Center obstetrical unit and nursery Gravid women will be recruited during antenatal visit at the Sheba medical Center, 1-4 weeks prior to labor. Women who will agree to participate and sign an informed consent will be screened for nasal and vaginal carriage of S. aureus. Newborns will be screened on delivery day and on discharge day.

Inclusion criteria:

1. Gravid women expected to deliver within 4 weeks.
2. Women who agree to participate and sign an informed consent
3. Women who are S. aureus carriers at the time of recruit.

Exclusion criteria:

1. Prolonged (>6 days) newborn hospitalization.
2. Women who did not give birth eventually at the Sheba Medical Center.
3. Women who's newborns were not screened at least once during delivery hospitalization.

Enrollment:

300 consecutive women who are defined as S. aureus carriers (see definitions below).

Screening will include:

Stage I before discharge:

1. Women - nasal screenings:

   A) On recruitment day (~1-4 weeks before labor), B) During hospitalization for delivery. Vaginal screening will be performed during the routine gynecologic examination on delivery day.

2. Newborns - will be screened A) On birth day, at entrance to the nursery. B) On discharge day. Screening will include nasal nares, umbilical, ear and rectal swabbing on each screening while hospitalized.

3. Data collection by questionnaires filled by recruited women.

4. Data collection from medical files of the maternity ward.

Stage II after discharge until age 5 years:

1. Mothers - monthly nasal swab for 12 months.
2. Children - monthly nasal, nasopharyngeal and rectal swabs for 12 months.
3. Same screen annually until the child is 5years old.
4. Data collection by questionnaires filled by the mothers.

Inclusion Criteria:

1. Gravid women expected to deliver within 4 weeks.
2. Women who agree to participate and sign an informed consent
3. Women who are S. aureus carriers at the time of recruit.

Exclusion Criteria:

1. Prolonged (>6 days) newborn hospitalization.
2. Women who did not give birth eventually at the Sheba Medical Center.
3. Women who's newborns were not screened at least once during delivery hospitalization.

Enrollment:

300 consecutive women who are defined as S. aureus carriers (see definitions below).

300 mother - newborn pairs.