Prevalence of Staphylococcus aureus in Parturient Women

Background: Low MRSA colonization levels in a neonatal care facility are an expected occurrence. Due to the rising levels of CA-MRSA, we promoted this research to evaluate the parturients as a potential source of MSSA and MRSA in the neonatal unit.

Objective: Evaluate the prevalence of Staphylococcus aureus colonization in parturients at the moment of birth and determine factors associated with carriage.

Methods: From March to August 2009, 148 parturients admitted to the Hospital das Clínicas of University of São Paulo were prospectively evaluated and swabs were taken from four different sites (nasal, oropharyngeal, anal and perineal). Swabs were transported in a Stuart medium to the laboratory and inoculated in agar manitol growth medium. Gram stain, catalase and DNase tests were performed to identify S. aureus which were further tested for methicillin resistance. Clinical and epidemiological data were obtained from the parturients and their neonates including: maternal underlying diseases, obstetric history, labour, prenatal care data and socioeconomic information. The data were analyzed for factors associated with colonization.

Results: The prevalence of S. aureus colonization in the parturients was 55% (n=81), 2,5% (n=2) were MRSA and 1,2% (n=1) MRSA and MSSA colonized. Ten neonates (7%) were MSSA colonized. Factors such as age (p=0,17), schooling (p=0,6), and use of alcohol (p=0,26 and 0,55), tobacco (p=0,78 and 0,73) and intravenous drugs (p=0,3 and 0,45), previously or during pregnancy respectively, had no statistical relevance towards S. aureus colonization. Factors associated with hospital care also did not influence the prevalence of S. aureus; as well as origin of patients (outpatient clinic, emergency room and elective admission) (p=0,46); ruptured membranes (p=0,48); type of labour (p=0,88); duration of labour (p=0,42); anaesthesia (p=0,21); number of vaginal touches (p=0,4); obstetric history [number of pregnancies (p=0,64), labours (p=0,41), and abortions (p=0,7)]; and number of visits during prenatal care (p=0,51). Underlying diseases did not influence colonization. Skin infections in the residents of the same household seemed to have a protective effect against S. aureus colonization (OR=0,18; CI=0,04-0,9; p=0,02). Maternal colonization with S. aureus was not associated with birthweight (p=0,51), gestational age at birth (p=0,63), characteristics of amniotic fluid (p=0,39), Apgar scale score in the 1^st (p=0,78), 5^th (p=0,89), and 10^th (p=0,78) minute, and neonatal colonization (p=0,5).

Conclusions: There was a very high prevalence of S. aureus colonization among the parturients. This may have been due to the use of four different culture sites. There was no apparent association of colonization with maternal and hospital factors. Although the majority was MSSA colonized, almost 4% of S. aureus were MRSA.