Barry Preuett

The Prevalence of Infections With Trichophyton tonsurans in Schoolchildren: the CAPITIS Study

BACKGROUND: Although Trichophyton tonsurans has become the leading cause of tinea capitis in the United States, reported infection rates vary widely, and prevalence estimates for the pediatric population at large remain poorly characterized. METHODS: A prospective, cross-sectional, surveillance study of children attending kindergarten through fifth grade in 44 schools across the bi-state (Kansas/Missouri), Kansas City metropolitan area was conducted. Fungal cultures were collected from all participants, and molecular analyses were used to characterize the patterns of infection within the population. RESULTS: Of 10514 children (age: 8.3 ± 1.9 years) examined for the presence of T tonsurans on their scalps, 6.6% exhibited positive cultures. Infection rates at participating schools ranged from 0% to 19.4%, exceeding 30% at a given grade level in some schools. Black children demonstrated the highest rates of infection (12.9%), with prevalence estimates for the youngest members of this racial group approaching 18%. Infection rates for Hispanic (1.6%) and white (1.1%) children were markedly lower. A single genetic strain of T tonsurans was identified in only 16.6% of classrooms, whereas each child harbored a unique genetic strain in 51.4%. CONCLUSIONS: We report a large-scale, citywide, surveillance study of T tonsurans infection rates among children in primary school in a metropolitan area. The striking prevalence rates and genetic heterogeneity among the fungal isolates confirm the relatively large degree to which this pathogen has become integrated into metropolitan communities.

Lectin as a marker for staining and purification of embryonic pancreatic epithelium

The embryonic pancreatic epithelium, and later the ductal epithelium, is known to give rise to the endocrine and exocrine cells of the developing pancreas, but no specific surface marker for these cells has been identified. Here, we utilized Dolichos Biflorus Agglutinin (DBA) as a specific marker of these epithelial cells in developing mouse pancreas. From the results of an immunofluorescence study using fluorescein-DBA and pancreatic specific cell markers, we found that DBA detects specifically epithelial, but neither differentiating endocrine cells nor acinar cells. We further applied this marker in an immunomagnetic separation system (Dynabead system) to purify these putative multi-potential cells from a mixed developing pancreatic cell population. This procedure could be applied to study differentiation and cell lineage selections in the developing pancreas, and also may be applicable to selecting pancreatic precursor cells for potential cellular engineering.

Divergence among an international population of Trichophyton tonsurans isolates.

Trichophyton tonsurans is a widely distributed pathogen that demonstrates a significant degree of genetic and phenetic heterogeneity. To date, the degree of genetic relatedness among geographically segregated isolates has not been explored. This investigation evaluates the extent of genetic variation among an international population of T. tonsurans isolates and examines the relatedness of isolates within and between countries. Molecular strain typing was performed on 198 isolates obtained from 14 countries. A mixed-marker strategy utilizing 27 sequence variations in 13 gene loci was applied to all isolates and cluster analysis was performed to examine the relationship between strains. Phylogenetic analysis was used to corroborate the findings of the cluster analysis with T. equinum strains serving as an out-group. In total, 47 distinct strain types were identified represented by seven clusters and one singleton. There appeared to be a moderate degree of clustering among isolates obtained from North America, Asia and Australia, although European isolates were uniformly distributed among the majority of clusters. The degree of genetic variation observed in this study coupled with the geographic localization would support the argument for allopatric divergence within this species.

A large outbreak of Trichophyton tonsurans among health care workers in a pediatric hospital

BACKGROUND Although Trichophyton tonsurans remains a major cause of dermataophytoses in US children, nosocomial spread may go unrecognized in health care settings. We describe a staff outbreak of T tonsurans infection among health care workers in a freestanding pediatric hospital. METHODS Epidemiologic evaluation (retrospective and prospective) was performed in the health care providers and ancillary staff assigned to a 27-bed inpatient medical unit in which the suspected outbreak occurred. RESULTS Twenty-one individuals, including staff, a hospital volunteer, and a patient, developed tinea corporis during a 5-month period. All infections coincided with multiple admissions of a 2-year-old suspected index patient who demonstrated persistent infections of the scalp and arm. Fungal isolates obtained from the index patient and affected staff (when available) were subjected to multilocus strain typing, which revealed an identical genetic match between the index case and infected hospital personnel. CONCLUSION T tonsurans can spread widely among staff members caring for children with recalcitrant dermatophyte infections. Recognition that workplace transmission may be the etiology of a succession of infections occurring in a single inpatient unit is necessary to limit the number of infected individuals.

Synergistic endocrine induction by GLP-1 and TGF-β in the developing pancreas

Objectives: Glucagon-like peptide-1 (GLP-1) is known to stimulate glucose-dependent insulin production and secretion by pancreatic β-cells. Preliminary evidence suggests that GLP-1 may also influence endocrine differentiation from pancreatic progenitor cells. Additionally, TGF-β signaling can also control endocrine differentiation by both inhibiting proliferation and enhancing differentiation of endocrine progenitor cells to become mature β-cells. Here we document synergy of these two signaling pathways in the differentiation of endocrine cells in the developing pancreas. Methods: Embryonic pancreas was harvested from mice at day 11.5 and cultured for six days with GLP-1 agonist, exendin-4, and/or TGF-β1 ligand. Also, a pan-neutralizing TGF-β isoform antibody was used alone or with exendin-4 to study TGF-β inhibition in this system. Pancreatic cultures were processed for immunohistochemistry. Results: Exogenous TGF-β1 and exendin-4 each individually enhanced both insulin and glucagon differentiation dose-dependently. However, when combined there was an additive effect to a 4.5-fold increase in insulin-positive differentiation. We also saw suppression of amylase-positive differentiation. Surprisingly, TGF-β pan-neutralizing antibody also gave an augmentation of endocrine differentiation by 1.5 to 2-fold, but no synergistic effect was seen with exendin-4. Conclusion: We conclude that TGF-β isoforms have a specific synergistic role with GLP-1 pathway signaling in early pancreatic development, toward endocrine differentiation and away from acinar differentiation.

Mesenchymal epimorphin is important for pancreatic duct morphogenesis

Epithelial–mesenchymal interactions are crucial for the proper development of many organs, including the pancreas. Within the pancreas, the ducts are thought to harbor stem/progenitor cells, and possibly to give rise to pancreatic ductal carcinoma. Little is known about the mechanism of formation of pancreatic ducts in the embryo. Pancreatic mesenchyme contains numerous soluble factors which help to sustain the growth and differentiation of exocrine and endocrine structures. Here, we report that one such morphoregulatory mesenchymal protein, epimorphin, plays an important role during pancreatic ductal proliferation and differentiation. We found that epimorphin is expressed in pancreatic mesenchyme during early stages of development, and at mesenchymal–epithelial interfaces surrounding the ducts at later stages. Strong upregulation of epimorphin expression was seen during in vitro pancreatic duct differentiation. Similarly, in vitro pancreatic duct formation was inhibited by a neutralizing antibody against epimorphin, whereas addition of recombinant epimorphin partially rescued duct formation. Together, our study demonstrates the role of epimorphin in pancreatic ductal morphogenesis.

Complete discontinuity of the distal fistula tract from the developing gut: Direct histologic evidence for the mechanism of tracheoesophageal fistula formation

The embryogenesis of tracheoesophageal anomalies remains controversial. The purpose of this study was to better define the embryogenesis of developing esophageal atresia with tracheoesophageal fistula (EA/TEF), with specific attention to the controversial issue of whether a discontinuity exists in the foregut during its development of EA/TEF. Pregnant outbred rats were injected with adriamycin (2 mg/kg i.p.) on days 6–9 of gestation (E6–E9). At E12.5 and 13.5, microdissection of the entire foregut was performed. Foreguts were examined by phase microscopy, and serial, precisely transverse sections were created for hematoxylin and eosin (H&E) staining. Gross microdissection of the developing foregut at E12.5 (n = 9) revealed a blind‐ending, bulbous fistula tract arising from the middle branch of the tracheal trifurcation (as seen by direct and phase microscopy). No connection with the gut could be appreciated at E12.5, but by E13.5 (n = 10) there was an obvious connection between the fistula and the stomach. Serial H&E transverse sections also demonstrated a blind‐ending fistula tract arising from the trachea at E12.5. This fistula tract was clearly discontinuous from the developing stomach, which appeared much further caudal to the end of the fistula tract. These results strongly support a model of experimental TEF wherein the fistula tract arises from a trifurcation of the trachea, and (only during a specific gestational window between days 12.5 and 13.5) there is discontinuity between the fistula tract and the stomach. By day 13.5, the fistula joins with the stomach anlage. These observations in the developing EA/TEF should help to resolve the controversy about the mechanism of EA/TEF formation. Anat Rec 267:220–224, 2002.

Multilocus Genotyping Identifies Infections by Multiple Strains of Trichophyton tonsurans

ABSTRACT Acquisition of multiple genetic strains of a single dermatophyte species should not be unexpected in areas of high endemicity, and yet multistrain infections are infrequently reported. This communication details mixed Trichophyton tonsurans infections and highlights the need to confirm the presence of multiple strains in a clinical single isolate by use of a multilocus approach.

Genetic predictors of susceptibility to cutaneous fungal infections: A pilot genome wide association study to refine a candidate gene search

BACKGROUND Trichophyton tonsurans is the foremost fungal pathogen of minority children in the U.S. Despite overwhelming infection rates, it does not appear that this fungus infects children in a non-specific manner. OBJECTIVE This study was designed to identify genes that may predispose or protect a child from T. tonsurans infection. METHODS Children participating in an earlier longitudinal study wherein infection rates could be reliably determined were eligible for inclusion. DNA from a subset (n=40) of these children at the population extremes underwent whole genome genotyping (WGG). Allele frequencies between cases and controls were examined and significant SNPs were used to develop a candidate gene list for which the remainder of the cohort (n=115) were genotyped. Cumulative infection rate was examined by genotype and the ability of selected genotypes to predict the likelihood of infection explored by multivariable analysis. RESULTS 23 genes with a putative mechanistic role in cutaneous infection were selected for evaluation. Of these, 21 demonstrated significant differences in infection rate between genotypes. A risk index assigned to genotypes in the 21 genes accounted for over 60% of the variability observed in infection rate (adjusted r(2)=0.665, p<0.001). Among these, 8 appeared to account for the majority of variability that was observed (r(2)=0.603, p<0.001). These included genes involved in: leukocyte activation and migration, extracellular matrix integrity and remodeling, epidermal maintenance and wound repair, and cutaneous permeability. CONCLUSIONS Applying WGG to individuals at the extremes of phenotype can help to guide the selection of candidate genes in populations of small cohorts where disease etiology is likely polygenic in nature.

Comparative analysis of secreted enzymes between the anthropophilic-zoophilic sister species Trichophyton tonsurans and Trichophyton equinum

Trichophyton tonsurans (TT) and Trichophyton equinum (TE) are two closely related dermatophytes with very different host preferences. This study was designed to examine the genetic and transcript level variations of secreted enzymes between TT and TE. Thirty-one genes representing 10 gene families were selected for comparison and complete genomic and cDNA sequences were elucidated. Sequence analyses of the selected genes identified 104 polymorphisms between the two dermatophytes, 37 of which are expected to encode changes in their polypeptide sequence. Quantitative RT-PCR was used to examine the differences in levels of transcript between TT and TE grown over 14d in aqueous keratin medium. Differences in transcript expression between TT and TE were gene specific and ranged from 1.1-fold to 33-fold. Intra-specific variability across all genes ranged from 41% to 250%. Despite their overall genetic similarity, TT and TE exhibit a moderate degree of variability in the genomic make-up of their secreted enzymes and the extent to which they are transcribed when grown in an aqueous keratin medium. Such differences may contribute to how these genetically similar organisms have adapted to infect divergent host organisms.