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Coagulase-negative staphylococci and its subtype Staphylococcus epidermidis are major indigenous Gram-positive inhabitants of the human skin. Colonization occurs in direct connection with birth and terrestrial adaptation. This study focuses on factors that may influence skin colonization of the newborn infant that relates to the immune status of both the bacteria and the host. Skin is an effective barrier against bacteria, and this function is partly mediated by the presence of antimicrobial peptides including human cathelicidin peptide LL37. Gram-positive bacteria have been described to have adhesive pili on their surface that mediates specific attachment to the host. Here, we identify, by negative staining transmission electron microscopy (EM), two different types of piluslike structures commonly expressed on S. epidermidis isolated from newborn infants. We also show that the cathelicidin antimicrobial peptide LL37, constitutively expressed in the skin barrier of the newborn, significantly inhibited growth of S. epidermidis indicating its importance for the ecological stability of the skin microbiota. Further studies are required to elucidate molecular mechanisms of host-microbe interactions, both for the maintenance of a mutually beneficial homeostatic relationship and for the protection of self when it results in overt disease. (Pediatr Res 66: 174-178, 2009) C oagulase-negative staphylococci (CoNS) are major skin commensals in humans (1). Within the first few hours of life colonization occurs (2), and by 1 d of age 84% of all healthy neonates have their skin colonized (3). Among the CoNS, particular attention has been focused on Staphylococcus epidermidis because it is the most common species responsible for infection causing significant morbidity, mortality, and incurring healthcare costs worldwide (4). In neonates, CoNS have emerged as prevalent and important pathogens, responsible for approximately 50% of all episodes of lateonset (Ͼ72 h) sepsis in very low birth weight infants (5). Recent evidence also links these bacteria to the pathogenesis of the immunologic skin reaction erythema toxicum, frequently seen in healthy newborns (3).Ecological stability of the commensal microflora is partly maintained by interactions with its human host. Our knowledge of how commensal bacteria interact with their host or how they communicate with each other is limited. We know that at birth commensals have to face the antimicrobial defense mechanisms of the skin and the vernix caseosa, a cream-like coating on newborns secreted by the fetal sebaceous glands. Human antimicrobial cathelicidin peptide LL37 is present in both vernix caseosa and the skin already at the time of birth, and the peptide is also up-regulated in the erythema toxicum lesions of the newborn infant (6). The presence of LL37 offers increased protection against bacterial infections in mice and humans (7,8). Thus, we hypothesized that LL37 is of importance for the microbial milieu of the skin, and we tested if it could influence growth of S. epi...

By collecting and analyzing diapers, we identified a >6-fold increase in carriage of extended-spectrum β-lactamase (ESBL)–producing Enterobacteriaceae for healthy preschool children in Sweden (p<0.0001). For 6 of the 50 participating preschools, the carriage rate was >40%. We analyzed samples from 334 children and found 56 containing >1 ESBL producer. The prevalence in the study population increased from 2.6% in 2010 to 16.8% in 2016 (p<0.0001), and for 6 of the 50 participating preschools, the carriage rate was >40%. Furthermore, 58% of the ESBL producers were multidrug resistant, and transmission of ESBL-producing and non–ESBL-producing strains was observed at several of the preschools. Toddlers appear to be major carriers of ESBL producers in Sweden.

The epidemiology and genetic variability of circulating respiratory syncytial virus (RSV) strains in Stockholm during the season 2002-2003 were studied in consecutive RSV isolates derived from respiratory samples and diagnosed in the laboratory. Two hundred thirty-four viruses were sequenced. The samples were mainly from children under 1 year old (79%). The phylogeny of the N-terminal part of the G gene was studied after amplification and sequencing. One hundred fifty-two viruses belonged to subgroup B and 82 to subgroup A. The subgroup A viruses could be further divided into genotypes GA2 (25) and GA5 (57) and the subgroup B viruses into GB3 (137) and SAB1 (15) strains. These strains clustered with subgroup A and subgroup B strains from Kenya from the same period, as well as with strains from Great Britain from 1995 to 1998. The dominance of subgroup B strains in Stockholm during 2002-2003 is in agreement with findings from other parts of the world during the same years. Only two genotypes of subgroup A, GA2 and GA5, were circulating during this time, and GA2 has been circulating in Sweden for more than 20 years. Consecutive strains from the same individual displayed no variability in the sequenced region, which was also true of strains that had been passaged in cell cultures.

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