Relationship between maternal and neonatal Staphylococcus aureus colonization.

OBJECTIVE: The study aimed to assess whether maternal colonization with Staphylococcus aureus during pregnancy or at delivery was associated with infant staphylococcal colonization. METHODS: For this prospective cohort study, women were enrolled at 34 to 37 weeks of gestation between 2007 and 2009. Nasal and vaginal swabs for culture were obtained at enrollment; nasal swabs were obtained from women and their infants at delivery and 2- and 4-month postbirth visits. Logistic regression was used to determine whether maternal colonization affected infant colonization. RESULTS: Overall, 476 and 471 mother-infant dyads had complete data for analysis at enrollment and delivery, respectively. Maternal methicillin-resistant S aureus (MRSA) colonization occurred in 10% to 17% of mothers, with the highest prevalence at enrollment. Infant MRSA colonization peaked at 2 months of age, with 20.9% of infants colonized. Maternal staphylococcal colonization at enrollment increased the odds of infant staphylococcal colonization at birth (odds ratio; 95% confidence interval: 4.8; 2.4-9.5), hospital discharge (2.6; 1.3-5.0), at 2 months of life (2.7; 1.6-4.3), and at 4 months of life (2.0; 1.1-3.5). Similar results were observed for maternal staphylococcal colonization at delivery. Fifty maternal-infant dyads had concurrent MRSA colonization: 76% shared isolates of the same pulsed-field type, and 30% shared USA300 isolates. Only 2 infants developed staphylococcal disease. CONCLUSIONS: S aureus colonization (including MRSA) was extremely common in this cohort of maternal-infant pairs. Infants born to mothers with staphylococcal colonization were more likely to be colonized, and early postnatal acquisition appeared to be the primary mechanism.

Vaccination as infection control: a pilot study to determine the impact of Staphylococcus aureus vaccination on nasal carriage.

BACKGROUND: There is a critical need for an effective Staphylococcus aureus vaccine for the prevention of staphylococcal disease. In this study, we investigated the impact of S. aureus conjugate vaccine comprised of capsular polysaccharides 5 and 8 (CP5, CP8) on nasal colonization with S. aureus. METHODS: Healthy adults recruited from one academic medical center to participate in a lot consistency trial of StaphVAX (S. aureus capsular polysaccharide 5 and 8 conjugate vaccine) were assessed for S. aureus nasal colonization at two weekly points prior to vaccination and again at six weeks post-vaccination. Serum anti-capsular antibody titers to CP5 and CP8 were obtained prior to vaccination and 42 days post-vaccination and measured by ELISA. RESULTS: Thirty of 88 enrolled subjects (34%) had S. aureus isolated from at least one of the pre-immunization cultures. Of these, 20 were termed persistent carriers due to two positive cultures one week apart; 19 of the 20 were evaluable at Day 42. Baseline anti-CP8 concentrations were higher in persistent carriers of CP8+ S. aureus; however, baseline anti-CP5 levels were not significantly higher in individuals persistently colonized with CP5+ S. aureus. Statistically significant rises in antibody concentrations were noted after vaccination. At Day 42, 14 of 19 persistent carriers remained colonized; 5 subjects did not have evidence of S. aureus colonization. Ten additional subjects were positive for S. aureus at Day 42 who were not persistently colonized at baseline. Serum antibody concentrations were not statistically different between those with persistent carriage vs. those that lost carriage or those with newly acquired carriage. CONCLUSIONS: Immune responses to vaccine were brisk and comparable in subjects with or without persistent colonization. Despite a substantial rise in anti-CP5 and anti-CP8 antibody concentrations post-vaccination, S. aureus nasal colonization rates did not significantly change.

Increasing rates of nasal carriage of methicillin-resistant Staphylococcus aureus in healthy children.

BACKGROUND: Prior studies, including one from our institution performed in 2001, suggest that nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) occurs infrequently in the healthy pediatric population (0.2-2.2%). However, infections caused by community-associated MRSA have increased remarkably in recent years. As a result, we restudied the prevalence of MRSA nasal colonization in healthy children, comparing results from 2001 and 2004. PATIENTS AND METHODS: Nasal swabs were collected from 500 children presenting for health maintenance visits. Samples were cultured quantitatively, and MRSA isolates were confirmed by growth on selective media, coagulase testing and the presence of the mecA resistance gene. MRSA isolates were further analyzed for antibiotic susceptibilities, genetic relatedness by pulsed field gel electrophoresis and polymerase chain reaction for the detection of the gene encoding Panton-Valentine leukocidin. RESULTS: There were 182 children (36.4%) colonized with S. aureus, and 46 (9.2%) colonized with MRSA. This is significantly higher than the MRSA colonization rate in 2001 (0.8%; P < 0.001). There were no significant associations between potential risk factors and MRSA colonization except for having a family member work in a hospital (odds ratio, 2.0; 95% confidence interval, 1.03-4.1). Pulsed field gel electrophoresis revealed heterogeneity of circulating strains, and the Panton-Valentine leukocidin gene locus was detected in 10 of 46 MRSA isolates (22%). CONCLUSION: Nasal MRSA colonization in healthy children in Nashville has increased significantly in the past 3 years. As colonization typically precedes infection, this increase may be a major factor in the emergence of community-associated MRSA as a pathogen of healthy children.