Repellency of the Components of the Essential Oil, Citronella, to Triatoma rubida, Triatoma protracta, and Triatoma recurva (Hemiptera: Reduviidae: Triatominae).

The kissing bugs--Triatoma rubida (Uhler), Triatoma protracta (Uhler), and Triatoma recurva (Stal)--are common hematophagous bugs in southeastern Arizona and responsible for severe allergic reactions in some individuals who are bitten. They also possess the potential to transmit the blood parasite, Trypanosoma cruzi. We previously found the essential oil, citronella, to be an excellent deterrent of feeding of T. rubida on a restrained mouse. In this work, we tested major components--alcohols, aldehydes, and monoterpenes--of citronella oil for repellency against the three common triatome species endemic in southern Arizona. The following citronella oil components--geraniol, citronellol, limonene, and citronellal--in different concentrations and combinations were tested. All components of citronella oil demonstrated some inhibition of feeding, ranging from very weak inhibition (limonene) to significant inhibition (geraniol and citronellol). A mixture of geraniol and citronellol was found to be repellant at concentrations of .165 and .165 vol%, respectively, for all three triatome species. Citronellal and limonene had no significant repellent activity. The repellent activity of citronella oil appears to be acting through direct contact with the bugs rather than diffusion of vapors.

Repellency of DEET, picaridin, and three essential oils to Triatoma rubida (Hemiptera: Reduviidae: Triatominae).

The kissing bug, Triatoma rubida (Uhler) is a common hematophagous bug in Tucson, AZ, and is responsible for causing severe allergic reactions in some bitten individuals. DEET, picaridin, tea tree oil, peppermint oil, and citronella oil were tested for repellency to T. rubida and its ability to probe and feed on a small restrained rat. No long range repellency was observed with any of the test materials. The lowest repellent concentrations observed were: 10% DEET, 7% picaridin; 30% tea tree oil, 3.3% peppermint oil, and 0.165% citronella oil. Only citronella oil was able to stop all probing and feeding by T. rubida. Citronella oil appears to be a promising potential repellent to prevent sleeping people from being bitten by kissing bugs.

Antibodies to alpha5beta1 and alpha(v)beta3 integrins react with Candida albicans alcohol dehydrogenase.

It has been hypothesized that Candida albicans possesses integrin-like receptors on its cell surface. This is because C. albicans binds numerous fluid-phase extracellular matrix (ECM) proteins on its cell surface and adheres to the same ECM proteins when immobilized. In addition, numerous antibodies to human integrins (receptors for ECM proteins) bind to the fungal cell surface and in so doing inhibit the binding of the respective proteins. To demonstrate the presence of such a cell surface integrin, a cDNA library of C. albicans yeast cells was screened with polyclonal antiserum to the human fibronectin receptor (alpha5beta1 integrin). Clones isolated by this screening technique also reacted specifically to antiserum against the human vitronectin receptor (alpha(v)beta3 integrin). DNA sequence analysis of the cloned insert predicted a 350 aa protein (37 kDa). This predicted protein showed 75% homology at the nucleotide sequence level to alcohol dehydrogenase (ADH) of Saccharomyces cerevisiae. In vitro transcription/translation of the cloned inserts yielded a 37 kDa protein that was immunoprecipitated with antibodies to the alpha5beta1 and alpha(v)beta3 integrins and an antibody to a C. albicans fibronectin receptor. These antibodies and an mAb to the human vitronectin receptor demonstrated an antigen of -37 kDa present in the cell-wall preparations of C. albicans and in spent growth medium. All four antibodies reacted with authentic ADH. The possible significance of these results in relation to C. albicans adherence is discussed.

Fungal and parasitic infections of the eye.

The unique structure of the human eye as well as exposure of the eye directly to the environment renders it vulnerable to a number of uncommon infectious diseases caused by fungi and parasites. Host defenses directed against these microorganisms, once anatomical barriers are breached, are often insufficient to prevent loss of vision. Therefore, the timely identification and treatment of the involved microorganisms are paramount. The anatomy of the eye and its surrounding structures is presented with an emphasis upon the association of the anatomy with specific infection of fungi and parasites. For example, filamentous fungal infections of the eye are usually due to penetrating trauma by objects contaminated by vegetable matter of the cornea or globe or, by extension, of infection from adjacent paranasal sinuses. Fungal endophthalmitis and chorioretinitis, on the other hand, are usually the result of antecedent fungemia seeding the ocular tissue. Candida spp. are the most common cause of endogenous endophthalmitis, although initial infection with the dimorphic fungi may lead to infection and scarring of the chorioretina. Contact lens wear is associated with keratitis caused by yeasts, filamentous fungi, and Acanthamoebae spp. Most parasitic infections of the eye, however, arise following bloodborne carriage of the microorganism to the eye or adjacent structures.

Two unusual presentations of urogenital histoplasmosis and a review of the literature.

Two unusual clinical presentations of urogenital histoplasmosis are described. A review of the literature on urogenital histoplasmosis is provided.

Overexpression of the Candida albicans ALA1 gene in Saccharomyces cerevisiae results in aggregation following attachment of yeast cells to extracellular matrix proteins, adherence properties similar to those of Candida albicans.

Candida albicans maintains a commensal relationship with human hosts, probably by adhering to mucosal tissue in a variety of physiological conditions. We show that adherence due to the C. albicans gene ALA1 when transformed into Saccharomyces cerevisiae, is comprised of two sequential steps. Initially, C. albicans rapidly attaches to extracellular matrix (ECM) protein-coated magnetic beads in small numbers (the attachment phase). This is followed by a relatively slower step in which cell-to-cell interactions predominate (the aggregation phase). Neither of these phases is observed in S. cerevisiae. However, expression of the C. albicans ALA1 gene from a low-copy vector causes S. cerevisiae transformants to attach to ECM-coated magnetic beads without appreciable aggregation. Expression of ALA1 from a high-copy vector results in both attachment and aggregation. Moreover, transcriptional fusion of ALA1 with the galactose-inducible promoters GALS, GALL, and GAL1, allowing for low, moderate, and high levels of inducible transcription, respectively, causes attachment and aggregation that correlates with the strength of the GAL promoter. The adherence of C. albicans and S. cerevisiae overexpressing ALA1 to a number of protein ligands occurs over a broad pH range, is resistant to shear forces generated by vortexing, and is unaffected by the presence of sugars, high salt levels, free ligands, or detergents. Adherence is, however, inhibited by agents that disrupt hydrogen bonds. The similarities in the adherence and aggregation properties of C. albicans and S. cerevisiae overexpressing ALA1 suggest a role in adherence and aggregation for ALA1 and ALA1-like genes in C. albicans.

Expression, cloning, and characterization of a Candida albicans gene, ALA1, that confers adherence properties upon Saccharomyces cerevisiae for extracellular matrix proteins.

Adherence of Candida albicans to host tissues is a necessary step for maintenance of its commensal status and is likely a necessary step in the pathogenesis of candidiasis. The extracellular matrix (ECM) proteins are some of the host tissue and plasma proteins to which C. albicans adheres through adhesins located on the fungal cell surface. To isolate genes encoding ECM adhesins, an assay was developed based on the ability of yeast cells to adhere to magnetic beads coated with the ECM protein fibronectin, type IV collagen, or laminin. A C. albicans genomic library was constructed by cloning XbaI-partially-digested and size-selected fragments into pAUR112, an Escherichia coli-yeast low-copy-number shuttle vector. The C. albicans library was transformed into Saccharomyces cerevisiae YPH 499, and clones capable of adherence were selected by using ECM protein-coated magnetic beads. A plasmid containing an approximately 8-kb insert was isolated from 29 adherent clones. These clones exhibited adherence to all ECM protein-coated magnetic beads and to human buccal epithelial cells. The ALA1 gene (for agglutinin-like adhesin) was localized by subcloning it into a 5-kb XbaI fragment which retained the adherence phenotype in both orientations. The complete DNA sequence of the 5-kb insert was determined, and an open reading frame (ORF) encoding 1,419 amino acid residues was identified. Deletions from the 5' and 3' ends extending into the DNA sequence encoding the 1,419-amino-acid ORF product inactivated the adherence phenotype, suggesting that it is the coding region of the ALA1 gene. A database search identified ALA1 to be similar to the C. albicans ALS1 (for agglutinin-like sequence 1) protein and the S. cerevisiae agglutinin protein (AG alpha1), although the homology at the primary amino acid sequence level is limited to the first half of each of these proteins. ALA1 contains a central domain of six tandem repeats of 36 amino acids. We discuss the significance of various predicted ALA1 structural motifs and their relationships to function in the adherence process.

Anthrax pneumonia.

Inhalation anthrax is a rare and almost uniformly fatal form of human anthrax caused by the inhalation of spores of Bacillus anthracis. A clue to the diagnosis is provided by taking a work history which will disclose patient exposure to contaminated animal products, most often animal hair and wool used in the textile industry. It is an illness with a biphasic course marked by the presence of a widened mediastinum on chest radiograph and often accompanied by hemorrhagic meningitis. The pathogenesis of this disease as well as the differential diagnosis of inhalation anthrax in the context of other zoonotic pneumonias is discussed. Therapy has been ineffectual probably because it has begun too late, but includes intravenous high dose penicillin G and perhaps vaccination to prevent relapse.

Infection due to Paecilomyces lilacinus: a challenging clinical identification.

We describe a case of noninvasive sinusitis caused by Paecilomyces lilacinus in a patient with diabetes mellitus. Cure was achieved by endoscopic drainage and aspiration of the fungal mass. We discuss the difficulty in and clinical importance of distinguishing Paecilomyces from Aspergillus.

A pseudoepidemic of Rhodotorula rubra: a marker for microbial contamination of the bronchoscope.

Rhodotorula rubra was isolated from bronchoscopy specimens from 11 patients. An investigation of the bronchoscopy equipment and the bronchoscopy suite revealed contamination of the suction channel with R rubra, as well as potentially pathogenic bacteria. Disinfection control methods included gas sterilization of the bronchoscope and the institution of an alcohol and air flush through the suction channel to allow complete drying of the scope between each patient use. We have had no further isolates of R rubra from bronchoscopy specimens since these measures were instituted, and repeat cultures from the suction channel have been negative.

Gelatin fragments block adherence of Candida albicans to extracellular matrix proteins.

The adherence of Candida albicans to extracellular matrix proteins may be a critical step in the pathogenesis of candidiasis. Yeast cell adherence to type I and IV collagen, fibronectin and laminin was blocked by peptide fragments from denatured type I collagen (gelatin). Gelatin fragments were obtained by digestion of the reduced protein with trypsin or CNBr. The fragments did not have antifungal properties, presumably inhibiting adherence by blocking receptors (adhesins) on the surface of the fungus. A 10-mer (GQRGVVGLPG) fashioned from the alpha-1 chain of type I collagen reduced adherence by 68%. However, a gelatin peptide possessing 47 amino acids reduced fungal adherence to type I collagen by 100%. Peptides derived from the biocompatible protein gelatin, therefore, may have a potential role in reducing the adherence of the fungus to host proteins.

Adherence of Candida albicans to host cells.

Research devoted to uncovering the mechanisms of adherence of Candida albicans to human tissue is reviewed. The physical aspects of adherence of the fungus to host cells and the biochemical and molecular features, as far as they are known, are discussed. Relevant pre- and post-adherence events in the pathogenesis of disease caused by this fungus are also noted. Putative adhesins and surface receptors of C. albicans for host proteins are discussed in detail.

Binding of plasma fibronectin to Candida albicans occurs through the cell binding domain.

Candida albicans yeast cells bind soluble human plasma fibronectin (Fn) through a glycoprotein receptor (adhesin) located on the cell surface. This work demonstrates that a 120 kDa proteolytic fragment of Fn encompassing the cell binding domain binds more avidly to the yeast cell adhesin than does the parent Fn molecule. The presence of binding of Fn fragments containing heparin- and gelatin-binding domains of Fn could not be detected. The binding of the 120 kDa fragment is inhibited by a monoclonal antibody to the cell binding domain containing the amino acid sequence, Arginine-Glycine-Aspartic acid (RGD) as well as by an RGD-containing approximately 23-mer Fn peptide, but not with heparin or GRGDSPL. The fact that the cell binding domain of soluble Fn binds more avidly than does the parent molecule may explain the difference in the interaction of soluble Fn and immobilized Fn with Candida. It is possible that, upon immobilization, Fn may expose domains of the molecule previously unexposed when the molecule is in the soluble state.

The fibronectin adhesin of Candida albicans.

Candida albicans possesses on its cell surface an adhesin which binds the whole viable fungus to subendothelial extracellular matrix and matrix proteins. The adhesin is composed of 75 to 80% carbohydrate and approximately 20 to 25% protein by weight. High-performance liquid chromatography of material eluted from a fibronectin-agarose affinity column demonstrates the presence of three peaks, all of which on sodium dodecyl sulfate-polyacrylamide gel electrophoresis show the presence of one protein of approximately 60 kDa. Molecular weight sizing column chromatography, however, demonstrates that the adhesin elutes with an apparent molecular mass of 42 kDa. The N terminus of the 60-kDa glycoprotein is blocked to Edman degradation. The fibronectin adhesin of C. albicans is a glycoprotein that may be present and functional as an aggregate or multimer of a 60-kDa protein.

The contribution of electrostatic forces to the process of adherence of Candida albicans yeast cells to substrates.

The contribution of electrostatic interactions to the adherence process of Candida albicans and other Candida species was investigated by mixing cationic or anionic exchange resins possessing free -COO- or -NH+4 groups, respectively, on their surface. The adherence process of yeast cells to the anionic exchange resin is a saturable event that is essentially complete by 60 min. There is no measurable interaction of yeast cells with the cationic exchange resin. All clinical isolates of C. albicans, C. pseudotropicalis, one isolate each of C. tropicalis and Torulopsis glabrata possessed electrostatic charge as defined by this method, whereas two clinical isolates of C. parapsilosis, C. krusei and one isolate of C. tropicalis did not have measurable electrostatic surface charge. The adherence process to the exchange resin with the free -NH+4 group was dependent upon the pH of the suspending medium and varied from one isolate to another. Fixing yeast cells, or alternatively, endothelial cells, in such a manner as to change the surface charge of both and then measuring adherence of yeast cells to the target cells was an event that was not controlled by electrostatic interactions as they are defined herein. It appears that whatever contribution electrostatic charges make to the adherence process, that at best, it is a minor contribution.