The new 6-unit individualized curriculum for pediatric residents: the perspective of neonatology fellowship program directors

OBJECTIVE

Starting in 2013, all pediatric residents entering fellowship must be provided six educational units whose structure is to be determined by their individual career plans. We sought to determine whether (1) neonatology fellowship program directors (PDs) consistently identify certain weaknesses among incoming fellows and (2) neonatology fellowship PDs agree on the most beneficial activities in which pediatric residents should participate to improve preparation for entry into neonatology fellowships.

STUDY DESIGN

We sent a 21-question survey focused on the structure and implementation of the 6-unit curriculum to all members of the Organization of Neonatology Training Program Directors.

RESULTS

Sixty-seven percent of PDs responded. Seventy-five percent cited insufficient procedural skills as the primary weakness of incoming fellows. More than 80% rated additional training in clinical neonatology, including procedural and resuscitation training, as 'beneficial' or 'highly beneficial'. In contrast, fewer than 40% of PDs gave the same positive ratings to activities broadly focused on scholarship.

CONCLUSIONS

The results of the survey may help guide pediatric residency programs as they undertake development of these new curricular initiatives for individual residents entering neonatology.

Gastrointestinal colonization by Candida albicans mutant strains in antibiotic-treated mice

Antibiotic-treated mice orally inoculated with one of three Candida albicans strains (including two mutant strains) or indigenous Candida pelliculosa showed levels of candidal gastrointestinal colonization that were strain specific. However, regardless of strain, the numbers of viable candida were intermediate to high in the stomach, were consistently lowest in the upper small intestine, and increased progressively down the intestinal tract.

The Candida albicans INT1 gene facilitates cecal colonization in endotoxin-treated mice

Increased intestinal colonization with Candida albicans is believed to be a major predisposing factor to systemic candidiasis. Previous evidence has implicated the C. albicans INT1 gene in hyphal development, epithelial adherence, and mouse virulence. The effect of INT1 on mouse cecal colonization was measured using a parent strain (CAF2, INT1/INT1), an int1 deletion homozygote (CAG3, int1/int1), and a heterozygous reintegrant (CAG5, int1/int1 + INT1). Forty-eight hours after oral inoculation of 10(7) C. albicans into normal mice, only low numbers of each strain were recovered from the cecal flora. In mice pretreated with oral bacitracin/streptomycin, cecal colonization of each C. albicans strain was increased compared to the corresponding strain inoculated into untreated mice, with the CAF2 parent strain greater (P < 0.01) than the two mutant strains, and with the heterozygous and homozygous mutants not different from each other. In mice pretreated with parenteral lipopolysaccharide (LPS), in addition to oral antibiotics, numbers of cecal CAF2, CAG5, and CAG3 were increased (P < 0.01) compared to the corresponding strain inoculated into mice treated with antibiotics alone. In LPS-treated mice, numbers of cecal C. albicans CAF2 (INT1/INT1) were greater (P < 0.05) than C. albicans CAG3 (int1/int1). Thus, parenteral LPS had an additive effect on C. albicans cecal colonization in antibiotic-treated mice, and the presence of two functional copies of the INT1 gene appeared to facilitate colonization in both antibiotic-treated mice and in mice treated with antibiotics plus parenteral endotoxin.

Effect of INT1 gene on Candida albicans murine intestinal colonization

BACKGROUND

Increased intestinal colonization with Candida albicans is believed to be a major factor predisposing immunocompromised and postsurgical patients to systemic candidiasis, although the mechanisms facilitating C. albicans colonization remain unclear. Because previous studies have linked the C. albicans INT1 gene to filament formation, epithelial adherence, and mouse virulence, experiments were designed to evaluate the effect of INT1 on intestinal colonization.

MATERIALS AND METHODS

Mice were orally inoculated with either the parent strain (CAF2, INT/INT1), an int1 heterozygote (CAG1, INT1/int1), an int1 homozygote (CAG3, int1/int1), or a reintegrant (CAG5, int1/int1 + INT1), and sacrificed 3 and 7 days later for quantitative analysis of cecal C. albicans.

RESULTS

Following oral inoculation with 10(3) C. albicans, only small numbers of each strain were recovered from the cecal flora of normal mice. However, in mice pretreated with oral antibiotics, cecal colonization of each strain was increased (P < 0.01). In addition, cecal colonization was reduced for all int1 mutant strains compared with the parent strain (P < 0.05). By light microscopy, all four C. albicans strains were easily observed in the ileal lumen as both budding yeast and filamentous forms, although only occasional yeast forms appeared adherent to the intestinal epithelium.

CONCLUSIONS

C. albicans readily colonized and replicated in the ceca of antibiotic-treated mice. The presence of two functional copies of INT1 appeared to facilitate C. albicans cecal colonization, suggesting that intestinal colonization may be another virulence factor associated with INT1 and that the gene product may be an attractive target to control C. albicans intestinal colonization.

Systemic infection following intravenous inoculation of mice with Candida albicans int1 mutant strains

The Candida albicans gene INT1 is associated with epithelial adhesion, hyphal formation, and virulence. C. albicans strains carrying two, one, or no functional INT1 alleles were used to assess the association between mortality and C. albicans persistence in the liver and kidney of intravenously inoculated mice. Mice were injected with 10(5) C. albicans CAF2 (parent strain, INT1/INT1), C. albicans CAG3 (homozygous disruptant, Int1/int1), or C. albicans CAG5 (heterozygous reintegrant, int1/int1 + INT1). Mortality was monitored and mice were sacrificed on Days 1, 7, 14, and 21 for quantitative analysis of kidney and liver microbes, with histologic analysis of these tissues as well. Mortality was highest for mice injected with the wild-type strain CAF2 (INT1/INT1) and lowest for mice injected with the homozygous disruptant CAG3 (int/int1). Yeast were readily cleared from the liver of all mice injected with any of the three C. albicans strains. Although the mutant strains CAG3 and CAG5 are defective for hyphal formation in vitro, there was histological evidence of abundant hyphal formation in the renal pelvis of mice injected with these strains. Compared to the wild-type strain, mutant strains were associated with reduced mortality but increased C. albicans persistence in the kidney. Thus, the absolute ability to form hyphae in the kidney did not appear to modulate either C. albicans-induced mortality or the course of progressive infection in the kidney. In addition, reduced virulence was paradoxically associated with increased, not decreased, persistence of C. albicans in the kidney.

Linkage of adhesion, filamentous growth, and virulence in Candida albicans to a single gene, INT1

Adhesion and the ability to form filaments are thought to contribute to the pathogenicity of Candida albicans, the leading cause of fungal disease in immunocompromised patients. Int1p is a C. albicans surface protein with limited similarity to vertebrate integrins. INT1 expression in Saccharomyces cerevisiae was sufficient to direct the adhesion of this normally nonadherent yeast to human epithelial cells. Furthermore, disruption of INT1 in C. albicans suppressed hyphal growth, adhesion to epithelial cells, and virulence in mice. Thus, INT1 links adhesion, filamentous growth, and pathogenicity in C. albicans and Int1p may be an attractive target for the development of antifungal therapies.

Epithelial adhesion in yeast species: correlation with surface expression of the integrin analog

Epithelial adhesion and expression of the integrin analog, a putative candidal adhesion, were correlated for 33 clinical and laboratory isolates of Candida albicans, other Candida species, and Saccharomyces cerevisiae. On flow cytometry with saturating concentrations of the monoclonal antibody OKM1, surface fluorescence was highest for C. albicans at 67.8% +/- 1.7% and significantly reduced for Candida tropicalis (32.0% +/- 2.6%), Candida parapsilosis (18.3% +/- 2.4%), Candida glabrata (3.3% +/- 0.8%), Candida lusitaniae (2.9% +/- 1.0%), Candida krusei (0.7% +/- 0.1%), and Saccharomyces cerevisiae (1.7% +/- 0.2%) (P < .006 for all other species vs. C. albicans). Adhesion to a human epithelial cell line was highest for C. albicans at 49.8% +/- 3.5%, lower for C. tropicalis (44.7% +/- 4.6%), and incrementally reduced for all other species (< 25%) (P < .012). The correlation between integrin expression and epithelial adhesion was highly significant (P = .0066; r2 = .8). Surface expression of the integrin analog predicts epithelial adhesion for yeast species isolated in opportunistic infections.

Distinct mechanisms of epithelial adhesion for Candida albicans and Candida tropicalis. Identification of the participating ligands and development of inhibitory peptides

The yeast Candida albicans is the leading cause of disseminated fungal infection in neonates, immunocompromised hosts, diabetics, and postoperative patients; Candida tropicalis is the second most frequent isolate. Because the integrin analogue in C. albicans shares antigenic, structural, and functional homologies with the beta 2-integrin subunits alpha M and alpha X, we investigated the role of integrin analogues in epithelial adhesion of C. albicans and C. tropicalis. On flow cytometry with the monoclonal antibody (mAb) OKM1, surface fluorescence was highest for C. albicans and significantly reduced for C. tropicalis (P < 0.001). However, adhesion to the human epithelial cell line HeLa S3 did not differ for these two candidal species: specific adhesion was highest for C. albicans at 44.0 +/- 1.8%, and only slightly lower for C. tropicalis at 38.8 +/- 3.6% (P = NS). The disparity between expression of the integrin analogue and epithelial adhesion suggested distinct mechanisms for this process in C. albicans versus C. tropicalis. Preincubation of C. albicans with anti-alpha M mAbs, with purified iC3b (the RGD ligand for the integrin analogue), or with 9-15-mer RGD peptides from iC3b all inhibited epithelial adhesion significantly (P < 0.001-0.04). Purified fibronectin or fibronectin-RGD peptides failed to block C. albicans adhesion. In contrast, epithelial adhesion of C. tropicalis was significantly inhibited by purified fibronectin and its RGD peptides (P < or = 0.021), but not by iC3b nor the iC3b-RGD peptides. Both iC3b and fibronectin were identified on the surface of epithelial cells after growth in serum-free medium. A polyclonal antibody to C3 inhibited C. albicans adhesion while a control antibody to fibronectin was ineffective; the converse was true for C. tropicalis. These results indicate that the pathogenic yeasts C. albicans and C. tropicalis recognize distinct RGD ligands present at the surface of the epithelial cell and that these interactions can be differentially inhibited by defined RGD peptides containing appropriate flanking sequences.

Molecular mimicry in Candida albicans. Role of an integrin analogue in adhesion of the yeast to human endothelium

Hematogenous infection with the yeast Candida albicans now occurs with increasing frequency in the neonate, the immunocompromised patient, and the hyperglycemic or hyperalimented host. Yeast-phase C. albicans expresses a protein that is antigenically and structurally related to CD11b/CD18, a member of the beta 2 integrins and a well-characterized adhesin for mammalian neutrophils. Both the neutrophil protein and its analogue in C. albicans have an identical affinity for the C3 ligand iC3b, and both proteins are significantly increased in expression at 37 degrees C. Given these several similarities, we therefore studied the role of the integrin analogue on C. albicans in the adhesion of the yeast to human umbilical vein endothelium (HUVE). After growth of C. albicans in 20 mM D-glucose, as opposed to 20 mM L-glutamate, flow cytometric analysis with monoclonal antibodies recognizing the alpha-subunit of CD11b/CD18 demonstrated a 25.0% increase in mean channel fluorescence (range 18.4-31.8%), as well as an increased percentage of yeasts fluorescing (P less than 0.02). This increased intensity of fluorescence, which corresponds to increased expression of the integrin analogue, also correlated with a significant increase of 30-80% in adhesion of glucose-grown C. albicans to HUVE (P less than 0.02). Blockade of the integrin analogue on C. albicans by monoclonal antibodies recognizing adhesive epitopes on neutrophil CD11b/CD18 inhibited glucose-enhanced adhesion of C. albicans to HUVE. Incubation of glucose-grown C. albicans with saturating concentrations of purified human iC3b, the ligand for CD11b/CD18, reduced adhesion of the yeast to HUVE by 49.7%, whereas BSA in equimolar concentration had no effect (P less than 0.001). These results identify a glucose-responsive integrin analogue on C. albicans as one of possibly several cellular structures that mediate adhesion of the yeast to human endothelium.

Hypopigmentation in the Prader-Willi syndrome

Cutaneous and ocular pigmentation were evaluated in 29 individuals with the Prader-Willi syndrome (PWS). Criteria for hypopigmentation included the presence of type I or II skin, the lightest skin type in the family by history, and iris translucency on globe transillumination. On the basis of these criteria, 48% of the PWS individuals were hypopigmented. The presence of hypopigmentation correlated with a small interstitial deletion on the proximal long arm of chromosome 15; however, this deletion was also found in individuals who did not meet the full criteria for hypopigmentation. Hairbulb tyrosinase activity and glutathione content, as well as urine cysteinyldopa excretion, were low in PWS individuals with and without hypopigmentation and did not separate these two groups. We conclude that hypopigmentation is found in a significant proportion of individuals with PWS and that the hypopigmentation may be associated with a deletion of the long arm of chromosome 15. The mechanism for the hypopigmentation is unknown.

Abnormalities of the central visual pathways in Prader-Willi syndrome associated with hypopigmentation

Patients with oculocutaneous or ocular albinism have misrouting of optic fibers, with fibers from 20 degrees or more of the temporal retina crossing at the chiasm instead of projecting to the ipsilateral hemisphere. Misrouting can result in strabismus and nystagmus. Because patients with the Prader-Willi syndrome may also have hypopigmentation and strabismus, we wondered whether they too might have misrouting of optic fibers. We therefore studied six patients with Prader-Willi syndrome selected for a history of strabismus, using pattern-onset visually evoked potentials with binocular and monocular stimulation to look for evidence of misrouted retinal-ganglion fibers. Four had hypopigmentation, and three of these four had abnormal evoked potentials indistinguishable from those recorded in human albinos. The two with normal pigmentation had normal responses. These findings indicate that patients with Prader-Willi syndrome who have hypopigmentation have a brain abnormality characterized by misrouting of retinal-ganglion fibers at the optic chiasm--a finding previously reported only in forms of albinism.