Demonstration of mother-to-infant transmission of Staphylococcus aureus by pulsed-field gel electrophoresis

Randomized Placebo-Controlled Trial of Topical Mupirocin to Reduce Staphylococcus aureus Colonization in Infants in the Neonatal Intensive Care Unit

OBJECTIVE

To evaluate the efficacy of topical mupirocin in reducing Staphylococcus aureus colonization in infants in the neonatal intensive care unit (NICU).

STUDY DESIGN

A prospective double-blind randomized controlled trial of mupirocin vs placebo in S aureus-colonized infants was conducted in a tertiary care NICU between October 2016 and December 2019. Weekly universal active surveillance with polymerase chain reaction screening identified colonized infants. Colonized infants received a 5-day course of mupirocin (mupirocin group) or petroleum jelly (control group). Repeat courses were given for additional positive screens.

RESULTS

A total of 216 infants were enrolled; 205 were included in data analyses. Primary decolonization was more successful for mupirocin-treated infants (86 of 104 [83%]) than for controls (20 of 101; 20%) (P < .001). Although recurrent S aureus colonization occurred frequently (59 of 81 [73%] mupirocin-treated and 26 of 33 [79%] controls), subsequent decolonization remained more successful for mupirocin-treated infants than for controls (38 of 49 [78%] vs 2 of 21 [10%]; P < .001). Subgroup analyses of infants of ≤30 weeks' gestational age yielded similar results; decolonization occurred more often in mupirocin-treated infants compared with control infants (63 of 76 [83%] vs 13 of 74 [18%]; P < .001). Bacterial sterile site infections tended to be less frequent in mupirocin-treated infants compared with controls (2 of 104 [2%] vs 8 of 101 [8%]; P = .057). No invasive S aureus infections occurred in mupirocin-treated infants, but 50% of infections in controls were from S aureus, and 1 resulted in death.

CONCLUSIONS

Universal active surveillance and targeted treatment with topical mupirocin is a successful decolonization strategy for NICU infants and may prevent S aureus infection. However, S aureus colonization frequently recurs, necessitating repeat treatment.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT02967432.

Epidemiology of Staphylococcus aureus in neonates on admission to a Chinese neonatal intensive care unit

Purpose

Little is known about the molecular epidemiology of Staphylococcus aureus in Chinese neonatal intensive care units (NICUs). We describe the molecular epidemiology of S. aureus isolated from neonates on admission to Beijing Children's Hospital.

Methods

From May 2015-March 2016, nasal swabs were obtained on admission from 536 neonates. Cultures were also obtained from body sites with suspected infections. S. aureus isolates were characterized by staphylococcal chromosomal cassette (SCCmec) type, staphylococcal protein A (spa) type, multilocus sequence type (MLST), sasX gene, antimicrobial susceptibility and cytotoxicity. Logistic regression assessed risk factors for colonization.

Results

Overall, 92 (17%) infants were colonized with S. aureus and 20 (3.7%) were diagnosed with culture-positive S. aureus infection. Of the colonized infants, 70% (64/92) harbored methicillin-susceptible S. aureus (MSSA), 30% (28/92) harbored methicillin-resistant S. aureus (MRSA) while 70% (14/20) of infected infants were culture-positive for MRSA, 30% (6/20) were culture-positive for MSSA. Risk factors for colonization included female sex, age 7–28 days, higher birthweight (3270 IQR [2020–3655] grams) and vaginal delivery (p<0.05). The most common MRSA and MSSA clones were community-associated ST59-SCCmecIVa-t437 (60%) and ST188-t189 (15%), respectively. The sasX gene was not detected. Some MSSA isolates (16%) were penicillin-susceptible and some MRSA isolates (18%) were oxacillin-susceptible. MRSA and MSSA had similar cytotoxicity, but colonizing strains were less cytotoxic than strains associated with infections.

Conclusions

S. aureus colonization was common in infants admitted to our NICU and two community-associated clones predominated. Several non-modifiable risk factors for S. aureus colonization were identified. These results suggest that screening infants for S. aureus upon admission and targeting decolonization of high-risk infants and/or those colonized with high-risk clones could be useful to prevent transmission.

Effect of Treating Parents Colonized With Staphylococcus aureus on Transmission to Neonates in the Intensive Care Unit: A Randomized Clinical Trial

IMPORTANCE

Staphylococcus aureus is a leading cause of health care-associated infections in the neonatal intensive care unit (NICU). Parents may expose neonates to S aureus colonization, a well-established predisposing factor to invasive S aureus disease.

OBJECTIVE

To test whether treating parents with intranasal mupirocin and topical chlorhexidine compared with placebo would reduce transmission of S aureus from parents to neonates.

DESIGN, SETTING, AND PARTICIPANTS

Double-blinded randomized clinical trial in 2 tertiary NICUs in Baltimore, Maryland. Neonates (n = 236) with S aureus-colonized parent(s) were enrolled. The study period was November 7, 2014, through December 13, 2018.

INTERVENTIONS

Parents were assigned to intranasal mupirocin and 2% chlorhexidine-impregnated cloths (active treatment, n = 117) or petrolatum intranasal ointment and nonmedicated soap cloths (placebo, n = 119) for 5 days.

MAIN OUTCOMES AND MEASURES

The primary end point was concordant S aureus colonization by 90 days, defined as neonatal acquisition of an S aureus strain that was the same strain as a parental strain at time of screening. Secondary outcomes included neonatal acquisition of any S aureus strain and neonatal S aureus infections.

RESULTS

Among 236 randomized neonates, 208 were included in the analytic sample (55% male; 76% singleton births; mean birth weight, 1985 g [SD, 958 g]; 76% vaginal birth; mean parent age, 31 [SD, 7] years), of whom 18 were lost to follow-up. Among 190 neonates included in the analysis, 74 (38.9%) acquired S aureus colonization by 90 days, of which 42 (56.8%) had a strain concordant with a parental baseline strain. In the intervention and placebo groups, 13 of 89 neonates (14.6%) and 29 of 101 neonates (28.7%), respectively, acquired concordant S aureus colonization (risk difference, -14.1% [95% CI, -30.8% to -3.9%]; hazard ratio [HR], 0.43 [95.2% CI, 0.16 to 0.79]). A total of 28 of 89 neonates (31.4%) in the intervention group and 46 of 101 (45.5%) in the control group acquired any S aureus strain (HR, 0.57 [95% CI, 0.31 to 0.88]), and 1 neonate (1.1%) in the intervention group and 1 neonate (1.0%) in the control group developed an S aureus infection before colonization. Skin reactions in parents were common (4.8% intervention, 6.2% placebo).

CONCLUSIONS AND RELEVANCE

In this preliminary trial of parents colonized with S aureus, treatment with intranasal mupirocin and chlorhexidine-impregnated cloths compared with placebo significantly reduced neonatal colonization with an S aureus strain concordant with a parental baseline strain. However, further research is needed to replicate these findings and to assess their generalizability.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02223520.

A prospective cohort study of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus carriage in neonates: the role of maternal carriage and phenotypic and molecular characteristics

Background

Staphylococcus aureus, particularly methicillin-resistant S. aureus (MRSA), in mothers can cause serious outcomes in neonates. We aimed to elucidate the associations of S. aureus and MRSA carriage between mothers and neonates.

Methods

A prospective cohort study was conducted between August and November 2015 in two hospitals in Shenzhen, China. Chinese pregnant women and their neonates who met the inclusion criteria were included in this study; samples and relevant information were collected. We assessed maternal–neonatal associations by using Poisson regression models.

Results

Overall, 1834 mothers and their neonates were included in this study. The prevalence of isolate carriage among the mothers was as follows: S. aureus (nasal, 25.8%; vaginal, 7.3%; and nasal and vaginal, 3.3%) and MRSA (nasal, 5.7%; vaginal, 1.7%; and nasal and vaginal, 0.5%). The incidences of S. aureus and MRSA carriage among neonates were 3.3% and 0.8%, respectively. Of the 21 maternal–neonatal pairs with S. aureus carriage, 14 were concordant pairs with the same phenotypic and molecular characteristics. After adjustment, the relative risks and 95% confidence intervals (CIs) between the S. aureus carriage of neonates and nasal S. aureus carriage, vaginal S. aureus carriage, and both nasal and vaginal S. aureus carriage of mothers were 2.8 (95% CI, 1.6–4.8), 7.1 (95% CI, 4.1–12.4), and 9.6 (95% CI, 4.2–22.4), respectively.

Conclusion

S. aureus carriage in mothers increases the risk for neonates.

Clinical evaluation of early acquisition of Staphylococcus aureus carriage by newborns

BACKGROUND

Little is known about neonatal Staphylococcus aureus carriage. Sites and clinical outcomes of S. aureus colonization during the first month of life were evaluated in this study.

METHODS

A cohort of 279 infants born at term to 277 mothers was included. Maternal S. aureus colonization status was examined before labor. Newborns were screened for nasal, auricular, umbilical, and rectal colonization, one to three times within 100h after birth, and infants of carrier mothers were re-screened at 1 month. Medical data were recorded from the medical charts at discharge and at the 1-month follow-up interview.

RESULTS

Overall 43 out of 279 (15.4%) infants acquired S. aureus within the first days of life. The only two predictors of S. aureus carriage in the postnatal period were maternal S. aureus carriage (odds ratio 7.905, 95% confidence interval 3.182-19.638) and maternal antibiotic treatment during labor (odds ratio 0.121, 95% confidence interval 0.016-0.949). Among colonized children, the nose (56%) and rectum (40%) were more frequently colonized, while ear (26%) and umbilicus (16%) colonization were less common. Co-colonization at two sites was rare (4%), but always predicted carriage at 1 month of age. Maternal and neonatal characteristics, including neonatal outcomes, were similar between S. aureus carrier and non-carrier infants during the first month of life.

CONCLUSIONS

Maternal carriage is the major predictor of neonatal S. aureus carriage. The nose and rectum are the main sites of neonatal carriage. S. aureus carriage was not associated with neonatal complications throughout the first month of life. The long-term significance of early S. aureus carriage is yet to be determined.

Treating Parents to Reduce NICU Transmission of Staphylococcus aureus (TREAT PARENTS) trial: protocol of a multisite randomised, double-blind, placebo-controlled trial

INTRODUCTION

More than 33,000 healthcare-associated infections occur in neonatal intensive care units (NICUs) each year in the USA. Parents, rather than healthcare workers, may be a reservoir from which neonates acquire Staphylococcus aureus (S. aureus) colonisation in the NICU. This study looks to measure the effect of treating parents with short course intranasal mupirocin and topical chlorhexidine antisepsis on acquisition of S. aureus colonisation and infection in neonates.

METHODS AND ANALYSIS

The TREAT PARENTS trial (Treating Parents to Reduce Neonatal Transmission of S. aureus) is a multicentre randomised, masked, placebo-controlled trial. Shortly after a neonate is admitted to the NICU, parents will be tested for S. aureus colonisation. If either parent screens positive for S. aureus, then both parents as a pair will be enrolled and randomised to one of the two possible masked treatment arms. Arm 1 will include assignment to intranasal 2% mupirocin plus topical antisepsis with chlorhexidine gluconate impregnated cloths for 5 days. Arm 2 will include assignment to placebo ointment and placebo cloths for skin antisepsis for 5 days. The primary outcome will be neonatal acquisition of an S. aureus strain that is concordant to the parental baseline S. aureus strain as determined by periodic surveillance cultures or a culture collected during routine clinical care that grows S. aureus. Secondary outcomes will include neonatal acquisition of S. aureus, neonatal S. aureus infection, eradication of S. aureus colonisation in parents, natural history of S. aureus colonisation in parents receiving placebo, adverse reactions to treatment, feasibility of intervention, and attitudes and behaviour in consented parents. Four hundred neonate-parent pairs will be enrolled.

ETHICS AND DISSEMINATION

The study was approved by Johns Hopkins University IRB in June 2014 (IRB number 00092982). Protocol V.7 was approved in November 2014. Findings will be published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT02223520.

Molecular typing of toxic shock syndrome toxin-1- and Enterotoxin A-producing methicillin-sensitive Staphylococcus aureus isolates from an outbreak in a neonatal intensive care unit

Outbreaks of Staphylococcus aureus are common in neonatal intensive care units (NICUs). Usually they are documented for methicillin-resistant strains, while reports involving methicillin-susceptible S. aureus (MSSA) strains are rare. In this study we report the epidemiological and molecular investigation of an MSSA outbreak in a NICU among preterm neonates. Infection control measures and interventions were commissioned by the Local Public Health Authority and supported by the Robert Koch Institute. To support epidemiological investigations molecular typing was done by spa-typing and Multilocus sequence typing; the relatedness of collected isolates was further elucidated by DNA SmaI-macrorestriction, microarray analysis and bacterial whole genome sequencing. A total of 213 neonates, 123 healthcare workers and 205 neonate parents were analyzed in the period November 2011 to November 2012. The outbreak strain was characterized as a MSSA spa-type t021, able to produce toxic shock syndrome toxin-1 and Enterotoxin A. We identified seventeen neonates (of which two died from toxic shock syndrome), four healthcare workers and three parents putatively involved in the outbreak. Whole-genome sequencing permitted to exclude unrelated cases from the outbreak and to discuss the role of healthcare workers as a reservoir of S. aureus on the NICU. Genome comparisons also indicated the presence of the respective clone on the ward months before the first colonized/infected neonates were detected.

Zebrafish phosvitin is an antioxidant with non-cytotoxic activity

Antioxidants, or anti-oxidant agents, have attracted a great deal of attention in recent years because of their roles in prevention of chronic diseases and utilization as preservatives in food and cosmetics. In this study, we clearly demonstrated that zebrafish recombinant phosvitin (rPv) is an antioxidant agent capable of inhibiting the oxidation of the linoleic acid, and scavenging the 2,2-diphenyl-1-picrylhydrazyl radical. We also showed that zebrafish rPv is a cellular antioxidant capable of protecting radical-mediated oxidation of cellular biomolecules. Importantly, zebrafish rPv is non-cytotoxic to murine macrophage RAW264.7 cells. It is the first report that showed the antioxidant activities of Pv in fishes, suggesting that zebrafish Pv can be an important antioxidant, which can be used as preservatives in food and cosmetics and even as supplementary mediator in different diseased states.

Prevalence of early-onset neonatal infection among newborns of mothers with bacterial infection or colonization: a systematic review and meta-analysis

BACKGROUND

Although neonatal infections cause a significant proportion of deaths in the first week of life, little is known about the burden of neonatal disease originating from maternal infection or colonization globally. This paper describes the prevalence of vertical transmission--the percentage of newborns with neonatal infection among newborns exposed to maternal infection.

METHODS

We searched Pubmed, Embase, Scopus, Web of Science, Cochrane Library, and WHO Regional Databases for studies of maternal infection, vertical transmission, and neonatal infection. Studies that measured prevalence of bacterial vertical transmission were included. Random effects meta-analyses were used to pool data to calculate prevalence estimates of vertical transmission.

RESULTS

122 studies met the inclusion criteria. Only seven studies (5.7%) were from very high neonatal mortality settings. Considerable heterogeneity existed between studies given the various definitions of infection (lab-confirmed, clinical signs), colonization, and risk factors of infection. The prevalence of early onset neonatal lab-confirmed infection among newborns of mothers with lab-confirmed infection was 17.2% (95%CI 6.5-27.9). The prevalence of neonatal lab-confirmed infection among newborns of colonized mothers was 0% (95% CI 0.0-0.0). The prevalence of neonatal surface colonization among newborns of colonized mothers ranged from 30.9-45.5% depending on the organism. The prevalence of neonatal lab-confirmed infection among newborns of mothers with risk factors (premature rupture of membranes, preterm premature rupture of membranes, prolonged rupture of membranes) ranged from 2.9-19.2% depending on the risk factor.

CONCLUSIONS

The prevalence of early-onset neonatal infection is high among newborns of mothers with infection or risk factors for infection. More high quality studies are needed particularly in high neonatal mortality settings to accurately estimate the prevalence of early-onset infection among newborns at risk.

Transmission of Methicillin-ResistantStaphylococcus aureusto Preterm Infants Through Breast Milk

Objective:

To determine a potential source of MRSA colonization and infection among preterm infants in a neonatal intensive care unit (NICU) using molecular analysis of breast milk samples.

Design:

Case report, outbreak investigation.

Results:

Preterm triplets were delivered at 26 weeks' gestation via cesarean section when routine active surveillance for MRSA was performed for all infants in a NICU. Surveillance consisted of swabbing the throat, nose, and umbilicus (TNU) weekly. Although infants A and B initially had negative TNU swabs, repeat cultures were positive for MRSA on day of life (DOL) 10 and DOL 18, respectively. Surveillance and clinical cultures for infant C were negative. Infant A developed sepsis, and multiple blood cultures were positive for MRSA beginning on DOL 14. Infant B developed conjunctivitis and a conjunctival exudate culture was positive for MRSA on DOL 70. Both infants were fed breast milk via nasogastric tube. Cultures of breast milk samples for infants A and B dated prior to either infant's first positive surveillance culture were positive for MRSA. All MRSA isolates had identical results on antibiotic susceptibility testing. PFGE demonstrated identical banding patterns for the MRSA isolates from the blood culture of infant A, breast milk for infants A and B, and a surveillance swab from infant B. At no time did the mother develop evidence of mastitis or other local breast infection.

Conclusions:

MRSA can be passed from mother to preterm infant through contaminated breast milk, even in the absence of maternal infection. Colonization and clinical disease can result.

Decolonization to prevent Staphylococcus aureus transmission and infections in the neonatal intensive care unit

Staphylococcus aureus (S. aureus) continues to be a leading cause of outbreaks and health-care-associated infections in neonatal intensive care units. In the first few months of life, many neonates acquire S. aureus as part of their delicate and evolving microbiota. Neonates that asymptomatically acquire S. aureus colonization are at increased risk of developing a subsequent S. aureus infection. This review discusses the epidemiology and prevention of S. aureus disease in neonates and how decolonization to eradicate S. aureus may decrease S. aureus transmission and infections in the neonatal intensive care unit.

The mother as most important risk factor for colonization of very low birth weight (VLBW) infants with extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E)

OBJECTIVES

This study aimed to determine the prevalence of and risk factors for colonization with extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) and methicillin-resistant Staphylococcus aureus (MRSA) in very low birth weight (VLBW; <1500 g) infants and their mothers.

METHODS

This investigation was conducted in the perinatal centre at the Charité Berlin between May 2012 and June 2013. VLBW infants and their mothers were screened for colonization with ESBL-E and MRSA. Demographic and clinical data were obtained from the German nationwide surveillance system for nosocomial infections in VLBW infants (NEO-KISS) and used to perform univariate and multivariate analyses.

RESULTS

Of 209 VLBW infants, 12 (5.7%) were colonized with ESBL-E. Eighteen of 209 (8.6%) ESBL-E-tested neonates were related to an ESBL-E-positive mother. Univariate analysis, strain typing and multivariate analysis (OR 7.4, 95% CI 2.1-26.7, P = 0.002) identified an ESBL-E-positive mother and maternal-neonatal transmission as a main source of colonization. The prevalence of MRSA was 2.3% (5 of 221) among VLBW infants. One of the 221 (0.5%) MRSA-tested neonates was related to an MRSA-positive mother. No risk factors for transmission of MRSA could be detected in this study.

CONCLUSIONS

Our study demonstrated that maternal-neonatal transmission of ESBL-E from mother to child is an important risk factor for colonization of VLBW infants. As a consequence, routine ESBL-E screening of neonates and mothers should be considered as a means of reducing neonatal morbidity and mortality.

Utility of surveillance cultures for antimicrobial resistant organisms in infants transferred to the neonatal intensive care unit

BACKGROUND

Infections with antibiotic resistant organisms (AROs) are an important source of morbidity and mortality among infants hospitalized in the neonatal intensive care unit (NICU). To identify potential reservoirs of AROs in the NICU, active surveillance strategies have been adopted by many NICUs to detect infants colonized with AROs. However, the yield, risks, benefits and costs of different strategies have not been fully evaluated.

METHODS

We conducted a retrospective study in 2 level III NICUs from 2004 to 2010 to investigate the yield of surveillance cultures obtained from infants transferred to the NICU from other hospitals. Cultures were processed for methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci and antibiotic-resistant gram-negative rods. Risk factors, selected outcomes and laboratory costs associated with ARO colonization were assessed.

RESULTS

Among 1751 infants studied, the rate of colonization for methicillin-resistant S. aureus, vancomycin-resistant enterococci and antibiotic-resistant gram-negative rods was 3%, 1.7% and 1%, respectively. Age at transfer was the strongest predictor of ARO colonization; infants transferred at ≥ 7 days of life had 5.8 increased odds of ARO colonization compared with infants <7 days of age. Transferred infants who were colonized had similar rates of mortality, ARO infection and duration of hospitalization compared with those who were not colonized. The laboratory cost of surveillance cultures during the study period was $58,425.

CONCLUSIONS

The rate of colonization with AROs at transfer was low particularly in infants <7 days old. Future studies should examine the safety of targeted surveillance strategies focused on older infants.

Risk of early-onset neonatal infection with maternal infection or colonization: a global systematic review and meta-analysis

BACKGROUND

Neonatal infections cause a significant proportion of deaths in the first week of life, yet little is known about risk factors and pathways of transmission for early-onset neonatal sepsis globally. We aimed to estimate the risk of neonatal infection (excluding sexually transmitted diseases [STDs] or congenital infections) in the first seven days of life among newborns of mothers with bacterial infection or colonization during the intrapartum period.

METHODS AND FINDINGS

We searched PubMed, Embase, Scopus, Web of Science, Cochrane Library, and the World Health Organization Regional Databases for studies of maternal infection, vertical transmission, and neonatal infection published from January 1, 1960 to March 30, 2013. Studies were included that reported effect measures on the risk of neonatal infection among newborns exposed to maternal infection. Random effects meta-analyses were used to pool data and calculate the odds ratio estimates of risk of infection. Eighty-three studies met the inclusion criteria. Seven studies (8.4%) were from high neonatal mortality settings. Considerable heterogeneity existed between studies given the various definitions of laboratory-confirmed and clinical signs of infection, as well as for colonization and risk factors. The odds ratio for neonatal lab-confirmed infection among newborns of mothers with lab-confirmed infection was 6.6 (95% CI 3.9-11.2). Newborns of mothers with colonization had a 9.4 (95% CI 3.1-28.5) times higher odds of lab-confirmed infection than newborns of non-colonized mothers. Newborns of mothers with risk factors for infection (defined as prelabour rupture of membranes [PROM], preterm <37 weeks PROM, and prolonged ROM) had a 2.3 (95% CI 1.0-5.4) times higher odds of infection than newborns of mothers without risk factors.

CONCLUSIONS

Neonatal infection in the first week of life is associated with maternal infection and colonization. High-quality studies, particularly from settings with high neonatal mortality, are needed to determine whether targeting treatment of maternal infections or colonization, and/or prophylactic antibiotic treatment of newborns of high risk mothers, may prevent a significant proportion of early-onset neonatal sepsis. Please see later in the article for the Editors' Summary.

Hormonal contraceptive use and persistent Staphylococcus aureus nasal carriage

BACKGROUND

Human nares colonized with Staphylococcus aureus are the most important reservoir for this pathogen. We studied the influence of sex and hormonal contraceptive use on persistent S. aureus nasal carriage.

METHODS

We conducted a cohort study in healthy volunteers and determined carriage status at baseline and again at follow-up by using the results of 2 swab samples at each time point. We applied logistic regression to analyze associations of interest.

RESULTS

At baseline, 266 of 1180 volunteers (22.5%) were classified as persistent nasal carriers. Compared with women not using hormonal contraceptives, women taking reproductive hormones (odds ratio [OR]. 1.88; 95% confidence interval [CI], 1.29-2.75; P = .001) and men (OR., 1.57; 95% CI, 1.08-2.28; P = .02) were more likely to be persistent carriers. These associations remained stable after adjusting for known risk factors of nasal carriage. Women taking hormonal contraceptives and being persistent carriers at baseline were more likely to remain carriers after a median follow-up time of 70 days than women not using such medication (OR, 3.25; 95% CI, 1.44-7.34; P = .005). No patterns of association could be observed between persistent carriage among women and type of progestin or dose of estrogen used. Assuming causality and using estimates from multivariable logistic regression, we approximated that 20% (95% CI, 2.4%-34.9%) of persistent nasal carriage among women represented by our sample is attributable to hormonal contraception (population-attributable fraction).

CONCLUSIONS

The widespread use of hormonal contraception may substantially increase the human S. aureus reservoir with potential impact on S. aureus infection and transmission.

Staphylococcus pseudintermedius in the dog: taxonomy, diagnostics, ecology, epidemiology and pathogenicity

The dog is the natural host of Staphylococcus pseudintermedius. Many research efforts are currently being undertaken to expand our knowledge and understanding of this important canine commensal and opportunistic pathogen. The objective of this review is to summarize the current knowledge of the species, including the latest research outcomes, with emphasis on taxonomy, diagnostics, ecology, epidemiology and pathogenicity. Despite the important taxonomic changes that have occurred over the past few years, the risk of misidentification in canine specimens is low and does not have serious consequences for clinical practice. Staphylococcus pseudintermedius carriage in the dog is more frequent and genetically heterogeneous compared with that of Staphylococcus aureus in man. It appears that these staphylococcal species have evolved separately through adaptation to their respective natural hosts and differ with regard to various aspects concerning ecology, population structure and evolution of antibiotic resistance. Further understanding of the ecology and epidemiology of S. pseudintermedius is hampered by the lack of a standard method for rapid and discriminatory typing and by the limited data available on longitudinal carriage and population structure of meticillin-susceptible strains. With regard to pathogenicity, it is only now that we are starting to explore the virulence potential of S. pseudintermedius based on genomic and proteomic approaches, and more research is needed to assess the importance of individual virulence factors and the possible existence of hypervirulent strains.

A cluster of methicillin-sensitive Staphylococcus aureus colonization in a nursery

BACKGROUND

Staphylococcus aureus is among the most important pathogens of bacteremia in hospitals. Colonizing strains may spread to other patients.

METHODS

Ninety-two mothers visiting delivery rooms were included in this study. From the mothers, specimens were obtained from the nares and vagina for the detection of S. aureus. From the babies, specimens were obtained from the nares and umbilicus within 24 h in the nursery.

RESULTS

The carriage rates of S. aureus were 25% in the parturient mothers and 30.9% in their babies. The majority (55 isolates, 94.8%) of the isolates were methicillin-sensitive S. aureus (MSSA). Of the 55 MSSA isolates, 11 genotypes were identified for isolates from the mothers and five geno-types for isolates from the infants. A major clone was identified and accounted for 82% of 34 isolates from the babies. Nine pairs of mothers and babies were colonized with MSSA; by molecular methods, the paired isolates were indistinguishable in two pairs.

CONCLUSION

Newborn babies acquire S. aureus colonization soon after birth, partly from their mothers. Once S. aureus is introduced into a nursery, spread of the strain may occur if health-care workers do not execute infection control measures strictly.

Transmission of Staphylococcus aureus from mothers to newborns

BACKGROUND

The study objective was to define the risk factors and the route of Staphylococcus aureus transmission between mother and newborn.

METHODS

Women at late pregnancy were screened for nasal and vaginal S. aureus colonization. Newborns were screened for nasal, auricular, umbilical, and rectal colonization at birth and before discharge. Carrier mothers and their newborns were rescreened at 1 month. Pulse-field gel electrophoresis was used to assess strain genetic relatedness.

RESULTS

Of the 208 women screened, 34% were colonized with S. aureus. Overall, by 72-100 hours after birth, the cumulative incidence of S. aureus acquisition was 42.6/100 newborns of carrier mothers versus 7.4/100 newborns of noncarrier mothers (adjusted risk ratio = 5.7; 95% confidence interval [CI], 2.3-13.9). The risk to acquire a maternal strain was significantly higher than nonmaternal strain (adjusted risk ratio = 1.5; 95% CI, 1.3-1.9); Newborns to carrier mothers were also at a risk to acquire nonmaternal S. aureus strains compared with newborns to noncarrier mothers (adjusted risk ratio = 2.9; 95% CI, 1.6-5.4). The cumulative incidence of S. aureus acquisition was similar among newborns delivered by cesarean versus vaginal delivery (24.5 vs. 23.0/100 cases). At 1-month follow-up, the cumulative incidence of S. aureus acquisition reached 69.7/100 newborns of carrier mothers.Genetically identical strains were isolated in 32/40 (80%) mother-newborn pairs, among these, the source of the newborn strain was a maternal nasal strain in 29/32 (90%).

CONCLUSIONS

Newborns of carrier mothers are at risk to acquire S. aureus colonization. Most newborns of carrier mothers are colonized within the first month of life. Horizontal transmission from the mother is probably the major source for S. aureus carriage in newborns.

Maternal vaginal colonisation by Staphylococcus aureus and newborn acquisition at delivery

We studied 1139 mother-infant pairs where the mother had had at least one vaginal swab in the month before delivery and their babies had had gastric and ear swabs taken immediately after delivery. The prevalence of vaginal carriage of Staphylococcus aureus was 5.9% among 1139 pregnant women within 1 month of delivery. The colonisation rate of S. aureus in newborns was tenfold higher when the mother was a vaginal carrier than when she was not (31.3% vs. 2.7%; relative risk 11.6 [95% CI 7.0, 19.2]; P < 0.05). Among carriers, delivery by caesarean section compared with the vaginal route, significantly decreased the likelihood of S. aureus colonisation in the newborns (15.4% vs. 41.5%; relative risk 0.35 [95% CI 0.14, 0.98]; P < 0.03). No S. aureus colonisation was detected in the mothers of 58% of the colonised newborns suggesting extra-delivery colonisation routes. Consequences for newborns were unclear as only one case of S. aureus neonatal sepsis was observed.

Prevalence of MRSA colonization in peripartum mothers and their newborn infants

Methicillin-resistant Staphylococcus aureus (MRSA) cultures were obtained from 288 mother-infant pairs. A questionnaire given to mothers and medical record review assessed risk factors for colonization. Only 2.1% of mothers and 0.7% of infants carried MRSA. There were no identical MRSA mother-newborn pairs. MRSA colonization by expectant mothers is uncommon and transmission to newborns from vaginal delivery did not occur.

Emergence of and risk factors for methicillin-resistant Staphylococcus aureus of community origin in intensive care nurseries

OBJECTIVE

The goal of this study was to define more clearly the impact of community-acquired methicillin-resistant Staphylococcus aureus clones (eg, USA300 and USA400) on colonization and infection in infants in intensive care nurseries and potential modes of transmission of community-acquired methicillin-resistant S aureus clones.

METHODS

Prospective surveillance for methicillin-resistant S aureus colonization and infection was performed among infants in the intensive care nurseries at Grady Memorial Hospital (Atlanta, GA) between 1993 and 2006. Beginning in September 2004, nares surveillance cultures were collected at admission. Methicillin-resistant S aureus isolates were genotyped by using pulsed-field gel electrophoresis and multiplex polymerase chain reaction assays for staphylococcal chromosomal cassette mec gene complex type and Panton-Valentine leukocidin genes. Prevalence of and risk factors for colonization with community-acquired versus health care-associated methicillin-resistant S aureus clones (eg, USA100) were assessed.

RESULTS

Between 1993 and 2006, 130 (3.5%) of 3707 infants were identified to be colonized with methicillin-resistant S aureus. Twelve (1.2%) of 996 admission nares cultures were positive for methicillin-resistant S aureus (since initiation of admission cultures in September 2004). Community-acquired methicillin-resistant S aureus clones were first recovered in 1998; the proportion of methicillin-resistant S aureus clones of community origin increased significantly between 1998 and 2004. Multivariate analysis identified vaginal delivery and maternal smoking, both among infants of mothers receiving systemic antibiotic treatment before delivery, as independent predictors for neonatal colonization with community-acquired methicillin-resistant S aureus. Systemic antibiotic therapy before delivery for nonsmoking mothers delivering through cesarean section and possibly endotracheal intubation were associated with the recovery of health care-associated methicillin-resistant S aureus clones.

CONCLUSIONS

Community-acquired methicillin-resistant S aureus clones have emerged as a major cause of methicillin-resistant S aureus colonization in high-risk newborns. Community-acquired methicillin-resistant S aureus recovery was associated with acquisition during birth, whereas health care-associated methicillin-resistant S aureus clones seemed to be transmitted nosocomially.

Methicillin-resistant Staphylococcus aureus infections among healthy full-term newborns

OBJECTIVE

Methicillin-resistant Staphylococcus aureus (MRSA) strains have emerged in the community, causing disease among healthy people lacking traditional risk factors for MRSA infection. This article describes an outbreak of MRSA among healthy full-term newborns.

DESIGN

Cases were identified and corresponding medical information collected. Telephone interviews were conducted with mothers of cases and surveillance cultures from mothers and newborns were performed. MRSA isolates were genotyped.

SETTING

Hospital in Chicago, Illinois, USA.

PARTICIPANTS

Newborns, their mothers and hospital healthcare workers.

INTERVENTION

Nursery infection control practices were enhanced. The MRSA-colonised healthcare workers received intranasal mupirocin.

MAIN OUTCOME

Within 4-23 days of birth, 11 newborns were identified with pustules, vesicles or blisters located on the head, groin, perineum, ears, legs, chin and trunk. All received antimicrobials and recovered without incident.

RESULTS

None of 432 peripartum women, one of 399 newborns, and two of 135 healthcare workers were nasal MRSA carriers. Available isolates from six patients, two healthcare workers, and one from an MRSA-colonised newborn were similar by pulsed-field gel electrophoresis. Other than contact with the hospital, no common exposures of MRSA transmission were identified.

CONCLUSIONS

MRSA strains that initially emerged in the community are now causing disease in healthcare settings. Providers should be aware that MRSA can cause skin infections among healthy newborns. Adherence to standard infection control practices is important to prevent transmission of MRSA in nurseries.

Épidermolyse staphylococcique et impétigo bulleux chez des jumeaux nouveau-nés contaminés par le lait maternel

Staphylococcus aureus is often responsible for late septic infections, more rarely of toxinic ones, occurring in neonatal period. We report a case of staphylococcal scalded skin syndrome and bullous impetigo in newborn twins infected by breast milk from their asymptomatic mother. This transmission was confirmed by molecular biology method. This case emphasizes the potential part of the mother in staphylococcal nosocomial infections and the complexity of toxinic mechanisms.

Prevalence of Methicillin-Sensitive and Methicillin-Resistant Staphylococcus aureus in Pregnant Women

OBJECTIVE

To estimate the extent of Staphylococcus aureus vaginal-rectal colonization among pregnant women as severe S aureus infections have emerged in pregnant and postpartum women and infants.

METHODS

We conducted a prospective surveillance study for methicillin-sensitive S aureus and methicillin-resistant S aureus on all routine de-identified vaginal-rectal prenatal group B streptococcus (GBS) screening cultures submitted to the microbiology laboratory of a tertiary-care facility from January to July 2005. Standard microbiologic techniques and molecular analyses were used to detect community-associated methicillin-resistant S aureus strains. As opposed to health care-associated methicillin-resistant S aureus isolates, community-associated methicillin-resistant S aureus isolates were defined as those possessing the type IV or type V staphylococcal chromosomal cassette mec element and usually lacking a multidrug-resistant phenotype.

RESULTS

A total of 2,963 GBS screening cultures were analyzed, from which 743 (25.1%, 95% confidence interval [CI] 23.5-26.7%) GBS isolates and 507 (17.1%, 95% CI 15.7-18.5%) S aureus isolates were identified. Group B streptococcus colonization was significantly associated with S aureus colonization (prevalence odds ratio 2.1, 95% CI 1.7-2.5, P < .001). Of the S aureus isolates, 14 (2.8%, 95% CI 1.4-4.2%) were methicillin-resistant, and 13 of these were determined to be community-associated methicillin-resistant S aureus.

CONCLUSION

The prevalence of S aureus colonization identified in GBS screening cultures from pregnant women was substantial and associated with GBS co-colonization. Although we do not advocate routine screening of pregnant women for methicillin-sensitive S aureus and methicillin-resistant S aureus colonization, we recommend continued monitoring of both methicillin-sensitive S aureus and methicillin-resistant S aureus infections in this population and their infants.

Choc toxique staphylococcique maternofœtal sur chorioamniotite

We report a rare case of mother-infant pair with Staphylococcal Toxic Shock Syndrome (TSS). A term neonate was born by caesarean section for maternal septic syndrome during per-partum. He presented with respiratory distress complicated by pulmonary hypertension, skin rash, and multiple organ system involvement. Staphylococcus aureus was isolated from placenta, surface swabs and gastric aspirate. He received adapted antibiotics, respiratory support by high frequency ventilation and NO. The mother had shock, skin rash and inflammatory syndrome. Outcome was good in both cases. The isolate produced enterotoxin C and L. Shock, exanthematous disease and multi-organ involvement complicating a staphylococcal infection in neonate must lead to suspect a TSS.

Father-to-infant transmission of community-acquired methicillin-resistant Staphylococcus aureus in a neonatal intensive care unit

Methicillin-resistant Staphylococcus aureus (MRSA) is increasingly being recognized as a cause of community-acquired infection. Its transmission in neonatal intensive care units (NICUs) has reportedly been linked to a few cases of community-acquired MRSA (CA-MRSA) infection. Here, I describe a case of CA-MRSA transmission from a father to his child in a NICU. Recognition that CA-MRSA may be transmitted in a hospital setting raises important issues for MRSA infection control and treatment options.

Transmission of Staphylococcus aureus between healthy, lactating mothers and their infants by breastfeeding

The authors have investigated Staphylococcus aureus transmission between healthy, lactating mothers without mastitis and their infants by breastfeeding using both bacteriological and molecular-epidemiological methods. They studied 8 healthy, lactating mothers without clinical signs of mastitis and their infants who were less than 3 months old. They collected samples of breast milk, swabs of the mothers' nipples, the infants' nares, and the infants' oral cavities. There was a 50% transmission rate between the pairs. As the result of 12 antibiotics' susceptibility, Methicillin-resistant S. aureus was isolated from 2 of the 4 pairs. Using pulsed-field gel electrophoresis, the authors determined chromosomal DNA restriction patterns of the S. aureus isolated from 4 mother-infant pairs. The DNA fragment patterns of the organism within a given mother-infant pair were indistinguishable or closely related. The results suggest that methicillin-resistant S. aureus or methicillin-sensitive S. aureus may be transmitted between healthy, lactating mothers without mastitis and their infants by breastfeeding.

Nosocomial transmission of methicillin-resistant Staphylococcus aureus from a mother to her preterm quadruplet infants

BACKGROUND

Patient-to-patient transmission of methicillin-resistant Staphylococcus aureus (MRSA) in neonatal intensive care units (NICUs) has been well described. We report the first documented outbreak of probable transmission of MRSA from a mother to 3 of her preterm quadruplet infants postnatally.

METHODS

Routine surveillance of clinical microbiologic laboratory reports revealed an increased incidence of MRSA infections in our NICU, including 3 of 4 preterm quadruplets. Surveillance cultures of the anterior nares of all patients and the quadruplets' parents were performed to detect MRSA carriage. The isolates were typed by pulsed-field gel electrophoresis with the restriction endonuclease SmaI. Infection control strategies included mupirocin treatment and contact isolation precautions for infected/colonized infants.

RESULTS

Clinical cultures from infants A, C, and D and surveillance cultures of the quadruplets' mother and 2 additional unrelated infants grew the same clone of MRSA. The mother's only identified risk factors for MRSA acquisition were 2 prepartum hospitalizations related to the multiple gestation and previous treatment with antibiotics. All anterior nares cultures were negative for MRSA after mupirocin treatment.

CONCLUSIONS

Use of gowns and gloves by the family members of women with multiple gestations should be recommended to prevent transmission of potential pathogens in the NICU.

DNA heterogeneity of Staphylococcus aureus strains evaluated by SmaI and SgrAI pulsed-field gel electrophoresis in patients with impetigo

To our knowledge, no studies have previously been carried out on the heterogeneity and intrafamily colonization of impetigo Staphylococcus aureus strains obtained by powerful discriminating methods such as pulsed-field gel electrophoresis (PFGE). To explore this topic, macrorestriction patterns of S. aureus strains were analyzed after SmaI and SgrAI digestion. The two enzymes provided superimposable results. A total of ninety-seven S. aureus strains was found in the 26 families whose lesions and nasal and pharyngeal samples were examined. There were 39 strains which were different by PFGE, and of these, 24 were found in the lesions. Although 85% of impetigo patients showed nasal colonization and 58% showed pharyngeal colonization, only 54% of the patients had the same PFGE strain in the lesion and in the nose, and 35% in the lesion and the pharynx. In half of the 26 families, at least one member (mother, father, or relative) presented a S. aureus strain identical, by PFGE, to strains isolated in patients' lesions. Nineteen percent of mothers, 15% of fathers, and 19% of the other relatives presented nasal colonization with strains identical to those isolated in the children's lesions. Lesional strains showed higher antimicrobial resistance than nonlesional isolates.

The influence of methicillin-resistant Staphylococcus aureus (MRSA) carriers in a nursery and transmission of MRSA to their households

We examined two persistent MRSA-carrier nurses in a maternity hospital to elucidate the transmission of methicillin-resistant Staphylococcus aureus (MRSA) from healthcare providers to newborn infants and to the nurses' own families. Genotyping of the MRSA strains was performed by analyzing genomic DNA restriction length polymorphisms from pulsed-field gel electrophoresis (PFGE-RFLPs). The children of these nurses were carrying genotypically identical MRSA strains as their mother. Both MRSA carrier families remained asymptomatic over a two-year follow-up period. Eradication of nasal MRSA carriage from the two nurses resulted in declining MRSA carriage rates among infants in the nursery. Healthcare providers may become transient or persistent MRSA carriers whilst working in hospitals in which MRSA is endemic. They may then become a source of infection for patients as well as their own families. We recommend that healthcare providers should be examined for MRSA if an MRSA epidemic occurs in a hospital. The families of any such carriers should also be examined for MRSA.