The symbiosis polysaccharide locus, syp, is required for Vibrio fischeri to form a symbiotic association with the squid Euprymna scolopes. It is also required for biofilm formation induced by the unlinked regulator RscS. The syp locus includes 18 genes that can be classified into four groups based on putative function: 4 genes encode putative regulators, 6 encode glycosyltransferases, 2 encode export proteins, and the remaining 6 encode proteins with other functions, including polysaccharide modification. To understand the roles of each of the 14 structural syp genes in colonization and biofilm formation, we generated nonpolar inframe deletions of each gene. All of the deletion mutants exhibited defects in their ability to colonize juvenile squid, although the impact of the loss of SypB or SypI was modest. Consistent with their requirement for colonization, most of the structural genes were also required for RscS-induced biofilm formation. In particular, the production of wrinkled colonies, pellicles, and the matrix on the colony surface was eliminated or severely decreased in all mutants except for the sypB and sypI mutants; in contrast, only a subset of genes appeared to play a role in attachment to glass. Finally, immunoblotting data suggested that the structural Syp proteins are involved in polysaccharide production and/or export. These results provide important insights into the requirements for the syp genes under different environmental conditions and thus lay the groundwork for a more complete understanding of the matrix produced by V. fischeri to enhance cell-cell interactions and promote symbiotic colonization.T he initial interactions between microbes and their hosts are critical to the establishment of both symbiotic and pathogenic associations. The adherence of the microbe to its host and bacterial cell-cell aggregation are two processes that can mediate these initial interactions. The roles of polysaccharides in promoting adherence and cell-cell interactions in pathogenic and symbiotic colonization are well recognized (29, 37). Bacterial lipopolysaccharides (LPS), for example, can mediate the adherence of bacterial cells to various cellular components, such as mannose receptors and mucus (17,34). Capsular polysaccharides (CPS) and/or exopolysaccharides (EPS), present on the bacterial surface and secreted, respectively, can promote adherence to host or abiotic surfaces by facilitating the formation of biofilms and thus increasing colonization efficiency (4).To understand bacterium-host and bacterium-bacterium interactions during the colonization of a host, we have used the symbiosis between the bacterium Vibrio fischeri and its host, the squid Euprymna scolopes, as a model system (30). We previously obtained evidence that one or more polysaccharides are important for the ability of V. fischeri to colonize its host (5, 36, 49, 50). In particular, V. fischeri depends upon the 18-gene symbiosis polysaccharide (syp) locus for efficient colonization: the insertional mutation of several syp genes reduced ...

Owing to the rare, yet serious nature of toxic epidermal necrolysis (TEN) and Stevens-Johnson syndrome (SJS), the authors would like to describe our experience with 41 pediatric patients to contribute to the current clinical understanding of the disease. From records at a single institution, 41 patients ≤18 years of age with a diagnosis of SJS or TEN were retrospectively identified. Data were obtained from the hospital's medical record, and a variety of variables were collected, including causative agent, percentage of total body surface area (%TBSA) slough, ocular involvement, medical treatment, operative procedures, time to wound closure, ventilator days, intensive care unit length of stay, and associated hospital mortality. Of the pediatric TEN patients included, the mean epidermal sloughing was 39.7 ± 26% TBSA. The presumptive inciting agent was a medication in 90% of cases. Mycoplasma pneumoniae was implicated in two cases (5%). The average time between onset of symptoms and burn intensive care unit admission was 3.6 ± 2.0 days. Acutely, 73% of patients exhibited ocular involvement, 90% needed supplemental enteral nutritional support, and 51% required mechanical ventilation. On average, subjects spent 19.9 ± 13.9 days in the intensive care unit. While acute mortality was 0%, 100% of patients still experienced long-term complications and 30% required follow-up procedures. When compared to current literature, the outcomes of our patients were similar to that of pediatric TEN at other institutions. While acute mortality is typically better within the pediatric population, patients still experience a significant level of morbidity and have serious long-term sequelae.

Biofilms are multicellular communities of bacteria attached to a surface and embedded in a protective matrix. In many cases, the signals that induce biofilm formation are unknown. Here, we report that biofilm formation by the marine bacterium Vibrio fischeri can be induced by the addition of arabinose to LBS (Luria-Bertani-salt), a tryptone-based medium. Growth of cells in the presence of 0.2% arabinose, but not other sugars, induced the production of a pellicle at the air/liquid interfaces of static cultures. V. fischeri failed to grow on arabinose as the sole carbon source, suggesting that pellicle production did not occur as a result of increased growth, but experiments using the acid/base indicator phenol red suggested that V. fischeri may partially metabolize arabinose. Pellicle production was independent of the syp polysaccharide locus but was altered upon disruption of the bcs cellulose locus. Through a screen for mutants defective for pellicle production, we found that loss of motility disrupted the formation of the arabinose-induced pellicle. Among the ϳ20 mutants that retained motility were strains with insertions in a putative msh pilus locus and a strain with a defect in yidK, which is involved in galactose catabolism. Mutants with the msh gene disrupted grew poorly in the presence of arabinose, while the yidK mutant appeared to be "blind" to the presence of arabinose. Finally, arabinose impaired symbiotic colonization by V. fischeri. This work thus identifies a novel signal and new pathways involved in control of biofilm formation by V. fischeri.

Toxic epidermal necrolysis (TEN) and Stevens-Johnson Syndrome (SJS) are rare yet severe exfoliative skin disorders. The authors examined the efficacy of predictive models for their use as prognostic indicators in pediatric SJS or TEN. Over a 15-year period, 41 patients ≤18 years of age were identified and reviewed. Predictive models compared retrospectively to the observed mortality in the population included: SCORTEN (Score of Toxic Epidermal Necrolysis), Pediatric Index of Mortality 2, Pediatric Risk of Mortality III-24, and Abbreviated Burn Severity Index. Correlation coefficients and 95% confidence intervals were calculated for the following: acute hospital length of stay, days until wound closure, days of mechanical ventilation, number of infectious complications, and number of acute operative procedures. When calculated within the first 24 hours of admission, the four models predicted low rates of mortality, approaching our 0% observed mortality, and also demonstrated a significant correlation between higher scores and the five chosen indicators of morbidity (P < .05). SCORTEN on day 3 of admission was statistically significant (P < .05) only when predicting the number of infectious complications and days of mechanical ventilation and was therefore felt to be less predictive than use of SCORTEN on admission. When calculated within the first day of admission of pediatric SJS or TEN patients, SCORTEN, Abbreviated Burn Severity Index, Pediatric Index of Mortality 2, and Pediatric Risk of Mortality III all significantly predict acute morbidity. This is the first time scoring systems have been assessed for their ability to predict mortality and morbidity in pediatric SJS or TEN despite its widely recognized, severe acute course of disease.