The adherence of microorganisms to contact lenses may be an important initial step in the pathoge... more The adherence of microorganisms to contact lenses may be an important initial step in the pathogenesis of contact lens-associated infectious keratitis. Using a strain of Candida albicans whose interaction with various polymers has been well characterized we systematically investigated the adherence of this pathogen to hard hydrophobic and soft hydrophilic extended-wear contact lenses. Yeasts adhere to the hydrophobic lenses in direct proportion to the wetting angle of the lens whereas yeasts adhere to the hydrophilic lenses in direct proportion to the water content of the lens. Tear proteins such as albumin, lactoferrin, and lysozyme in addition to fibronectin enhance yeast adherence to both types of lenses (P less than 0.01). Concanavalin A reduces adherence of yeasts to both lens types (P less than 0.01). Among tear components however, only mucin (0.5%) consistently reduced yeast adherence to both lens types. Hydrophilic extended wear lenses worn for at least 28 days by normal patients consistently had greater adherence of yeasts than unworn lenses of the same type, often as much as ten-fold or greater yeasts/mm2 of lens surface area (P less than 0.05). These investigations indicate that tear components both in solution and adsorbed to the lens surface enhance microorganism adherence to contact lenses.
ABSTRACT Chagas disease caused by T. cruzi is an emerging infectious disease in the United States... more ABSTRACT Chagas disease caused by T. cruzi is an emerging infectious disease in the United States due to the immigration of infected individuals from endemic Mexico, Central and South American countries. The American Southwests growing human population has encroached upon the habitat of local triatomines, several of which are competent vectors of T. cruzi among resident small mammals. Human residents are accidental blood meal hosts of these hematophagous bugs. Many human victims suffer anaphylaxis after being bitten by the bugs. We are currently studying the rate of infection by T. cruzi of T. rubida and T. protracta, identifying their blood meal hosts and gathering data on the incidence of anaphylaxis to triatomine bites.
Coupled gas-liquid boundary-layer problems have direct engineering relevance to the design and op... more Coupled gas-liquid boundary-layer problems have direct engineering relevance to the design and operation of industrial process equipment and are important in meteorological and geophysical applications requiring knowledge about the transport processes at the air-ocean interface. The boundary-layer equations of heat, mass, and momentum in turbulent flow above and below an air-water interface roughened by wind-waves are solved numerically using the efficient and versatile Keller Box scheme and compared with experimental data acquired in a laboratory research facility.
... In Florida, we studied Camponotlts abdomina lis floridanus in a subtropical sandhill habitat.... more ... In Florida, we studied Camponotlts abdomina lis floridanus in a subtropical sandhill habitat. We discovered significant differences in the adaptations of these two species to their re-spective environments. Nest sites of carpenter ants, their colony size, and the dimensions of their ...
Ten isolates of Pseudomonas aeruginosa obtained from the corneas of patients with Pseudomonas ker... more Ten isolates of Pseudomonas aeruginosa obtained from the corneas of patients with Pseudomonas keratitis adhered to soft contact lenses in significantly greater numbers than did six isolates from other body sites (P less than .05). However, there was no predominant serotype among the 10 corneal isolates tested. Isolates grown statically in broth at 37 degrees C formed a pellicle and adhered two times as much to contact lenses as did isolates grown in broth while shaking which did not form a pellicle (P less than .01). The more adherent isolates (grown at 37 degrees C) were shown to be more hydrophobic than the less adherent bacteria (grown at 26 degrees C) by their propensity to accumulate at the interface between hexadecane and saline and their movement into polyethylene glycol from dextran. These corneal isolates agglutinated erythrocytes, a process that was inhibited by dilute solutions (as low as 0.01%) of three commonly used surfactants. These same surfactants inhibited the adherence of Pseudomonas aeruginosa to soft contact lens surfaces by as much as 52%. It is concluded that hydrophobic interactions may significantly contribute to the ability of Pseudomonas aeruginosa to adhere to contact lenses.
The adherence ofCandida yeasts to monolayers of human intestinal epithelium was studied in order ... more The adherence ofCandida yeasts to monolayers of human intestinal epithelium was studied in order to determine the specific and nonspecific mechanisms that might contribute to yeast adherence. Multiple factors were shown to significantly affect the adherence of yeasts to intestinal cells. It was demonstrated that hydrophobic yeasts adhered two times greater than normal yeasts, and positively charged yeasts adhered ten
Kissing bugs (Triatoma spp.) frequently enter homes and bite human and pet occupants. Bites may l... more Kissing bugs (Triatoma spp.) frequently enter homes and bite human and pet occupants. Bites may lead to severe allergic reactions and, in some cases, death. Kissing bugs are also vectors of Trypanosoma cruzi, the cause of Chagas disease. In general, modern houses in the United States are not conducive to domiciliation of kissing bugs (bugs living out their entire life within the home with the presence of eggs, nymphs, adults, and exuviae). Construction features such as concrete foundations, solid walls and ceilings, window screens, tight thresholds for doors and windows, and other measures impede bug entry into homes, and air conditioning reduces the need for open doors and windows. Where Chagas disease is endemic in Mexico and Central and South America, homes often have thatch roofs, adobe walls, and open doors and windows. We investigated numerous instances of kissing bug intrusions into homes in Southern Arizona, California, and Louisiana and documented the reactions to kissing b...
Journal of the International Association of Providers of AIDS Care, Jan 15, 2014
Frailty is common in HIV-infected patients, but its causes are elusive. We assessed 122 clinic pa... more Frailty is common in HIV-infected patients, but its causes are elusive. We assessed 122 clinic patients for frailty using the 5-measure Fried Frailty criteria. The prevalence of frailty was 19% (n = 23) and all frail patients reported exhaustion with a Center for Epidemiologic Studies Depression Scale score >16 indicating depression. The next most common criterion was low physical activity (expenditure of kcal/week). Markers of sarcopenia such as decreased grip strength and decreased gait speed, hallmarks of frailty in the elderly, were the least common of the 5 criteria. Frailty was reversible: 6 frail patients returned for reassessment and only 2 were frail. We conclude that frailty in the HIV-infected patients is potentially reversible and strongly associated with depression and low physical activity, whereas frailty in the elderly is associated with aging-related sarcopenia and is often irreversible.
We have demonstrated the presence of Candida cell surface amyloids that are important in aggregat... more We have demonstrated the presence of Candida cell surface amyloids that are important in aggregation of fungi and adherence to tissue. Fungal amyloid was present in invasive human candidal infections and host serum amyloid P component (SAP) bound to the fungal amyloid. SAP is a protease-resistant glycoprotein that binds avidly to amyloid and interferes with host defence, especially against bacterial pathogens for which neutrophils are important. In this study, we investigated whether biofilm of fungal amyloid and SAP was a feature of other disseminated fungal infections. Tissue specimens from 15 autopsies were systematically evaluated with multiple histochemical stains including thioflavin T and Congo red (dyes that stain amyloid), as well as antibody to SAP. We studied specimens with disseminated aspergillosis, mucormycosis and coccidioidomycosis. The structure of the lesions, host inflammatory cells and the presence of fungal amyloid and SAP were determined. The structure of the lesions was characteristic in aspergillosis ('starburst') and mucormycosis (closely apposed bundles of hyphae). Host inflammatory cells were absent or few in number within these lesions. In Coccidioides lesions, host inflammation was sparse as well. Fungal amyloid was a prominent feature of all lesions along with abundant SAP bound to hyphae and spherules. Fungal amyloid and SAP perhaps contributed to persistence in caseous necrosis lesions. SAP also bound to Aspergillus and Mucorales amyloid in vitro. A biofilm including amyloid and SAP is present in invasive fungal infections. This biofilm may dampen host defence leading to the characteristic sparse inflammatory reaction found in these infections.
Chagas disease caused by T. cruzi is an emerging infectious disease in the United States due to t... more Chagas disease caused by T. cruzi is an emerging infectious disease in the United States due to the immigration of infected individuals from endemic Mexico, Central and South American countries. The American Southwests growing human population has encroached upon the habitat of local triatomines, several of which are competent vectors of T. cruzi among resident small mammals. Human residents are accidental blood meal hosts of these hematophagous bugs. Many human victims suffer anaphylaxis after being bitten by the bugs. We are currently studying the rate of infection by T. cruzi of T. rubida and T. protracta, identifying their blood meal hosts and gathering data on the incidence of anaphylaxis to triatomine bites.
Chagas disease remains the most serious parasitic disease in Latin America with an estimated 10 m... more Chagas disease remains the most serious parasitic disease in Latin America with an estimated 10 million people currently infected with Trypanosoma cruzi, the causative agent. Most people become infected via triatomine insect vectors. Traditionally, taxonomists have attempted to classify the more than 130 species of triatomines by morphological characters to understand their evolutionary relationships and to infer the vector capacity of the species from their shared traits. Morphologically similar species have been organized into species complexes. Although the evolutionary relationships of many South American species have been inferred by extensive molecular studies, North and Central American species have received much less attention. The purpose of this study was to clarify the evolutionary relationships of 10 species of triatomines from North and Central America using two distinct molecular markers. A 339 base pair fragment of the 16S mitochondrial ribosomal subunit and the entir...
The adherence of microorganisms to contact lenses may be an important initial step in the pathoge... more The adherence of microorganisms to contact lenses may be an important initial step in the pathogenesis of contact lens-associated infectious keratitis. Using a strain of Candida albicans whose interaction with various polymers has been well characterized we systematically investigated the adherence of this pathogen to hard hydrophobic and soft hydrophilic extended-wear contact lenses. Yeasts adhere to the hydrophobic lenses in direct proportion to the wetting angle of the lens whereas yeasts adhere to the hydrophilic lenses in direct proportion to the water content of the lens. Tear proteins such as albumin, lactoferrin, and lysozyme in addition to fibronectin enhance yeast adherence to both types of lenses (P less than 0.01). Concanavalin A reduces adherence of yeasts to both lens types (P less than 0.01). Among tear components however, only mucin (0.5%) consistently reduced yeast adherence to both lens types. Hydrophilic extended wear lenses worn for at least 28 days by normal patients consistently had greater adherence of yeasts than unworn lenses of the same type, often as much as ten-fold or greater yeasts/mm2 of lens surface area (P less than 0.05). These investigations indicate that tear components both in solution and adsorbed to the lens surface enhance microorganism adherence to contact lenses.
ABSTRACT Chagas disease caused by T. cruzi is an emerging infectious disease in the United States... more ABSTRACT Chagas disease caused by T. cruzi is an emerging infectious disease in the United States due to the immigration of infected individuals from endemic Mexico, Central and South American countries. The American Southwests growing human population has encroached upon the habitat of local triatomines, several of which are competent vectors of T. cruzi among resident small mammals. Human residents are accidental blood meal hosts of these hematophagous bugs. Many human victims suffer anaphylaxis after being bitten by the bugs. We are currently studying the rate of infection by T. cruzi of T. rubida and T. protracta, identifying their blood meal hosts and gathering data on the incidence of anaphylaxis to triatomine bites.
Coupled gas-liquid boundary-layer problems have direct engineering relevance to the design and op... more Coupled gas-liquid boundary-layer problems have direct engineering relevance to the design and operation of industrial process equipment and are important in meteorological and geophysical applications requiring knowledge about the transport processes at the air-ocean interface. The boundary-layer equations of heat, mass, and momentum in turbulent flow above and below an air-water interface roughened by wind-waves are solved numerically using the efficient and versatile Keller Box scheme and compared with experimental data acquired in a laboratory research facility.
... In Florida, we studied Camponotlts abdomina lis floridanus in a subtropical sandhill habitat.... more ... In Florida, we studied Camponotlts abdomina lis floridanus in a subtropical sandhill habitat. We discovered significant differences in the adaptations of these two species to their re-spective environments. Nest sites of carpenter ants, their colony size, and the dimensions of their ...
Ten isolates of Pseudomonas aeruginosa obtained from the corneas of patients with Pseudomonas ker... more Ten isolates of Pseudomonas aeruginosa obtained from the corneas of patients with Pseudomonas keratitis adhered to soft contact lenses in significantly greater numbers than did six isolates from other body sites (P less than .05). However, there was no predominant serotype among the 10 corneal isolates tested. Isolates grown statically in broth at 37 degrees C formed a pellicle and adhered two times as much to contact lenses as did isolates grown in broth while shaking which did not form a pellicle (P less than .01). The more adherent isolates (grown at 37 degrees C) were shown to be more hydrophobic than the less adherent bacteria (grown at 26 degrees C) by their propensity to accumulate at the interface between hexadecane and saline and their movement into polyethylene glycol from dextran. These corneal isolates agglutinated erythrocytes, a process that was inhibited by dilute solutions (as low as 0.01%) of three commonly used surfactants. These same surfactants inhibited the adherence of Pseudomonas aeruginosa to soft contact lens surfaces by as much as 52%. It is concluded that hydrophobic interactions may significantly contribute to the ability of Pseudomonas aeruginosa to adhere to contact lenses.
The adherence ofCandida yeasts to monolayers of human intestinal epithelium was studied in order ... more The adherence ofCandida yeasts to monolayers of human intestinal epithelium was studied in order to determine the specific and nonspecific mechanisms that might contribute to yeast adherence. Multiple factors were shown to significantly affect the adherence of yeasts to intestinal cells. It was demonstrated that hydrophobic yeasts adhered two times greater than normal yeasts, and positively charged yeasts adhered ten
Kissing bugs (Triatoma spp.) frequently enter homes and bite human and pet occupants. Bites may l... more Kissing bugs (Triatoma spp.) frequently enter homes and bite human and pet occupants. Bites may lead to severe allergic reactions and, in some cases, death. Kissing bugs are also vectors of Trypanosoma cruzi, the cause of Chagas disease. In general, modern houses in the United States are not conducive to domiciliation of kissing bugs (bugs living out their entire life within the home with the presence of eggs, nymphs, adults, and exuviae). Construction features such as concrete foundations, solid walls and ceilings, window screens, tight thresholds for doors and windows, and other measures impede bug entry into homes, and air conditioning reduces the need for open doors and windows. Where Chagas disease is endemic in Mexico and Central and South America, homes often have thatch roofs, adobe walls, and open doors and windows. We investigated numerous instances of kissing bug intrusions into homes in Southern Arizona, California, and Louisiana and documented the reactions to kissing b...
Journal of the International Association of Providers of AIDS Care, Jan 15, 2014
Frailty is common in HIV-infected patients, but its causes are elusive. We assessed 122 clinic pa... more Frailty is common in HIV-infected patients, but its causes are elusive. We assessed 122 clinic patients for frailty using the 5-measure Fried Frailty criteria. The prevalence of frailty was 19% (n = 23) and all frail patients reported exhaustion with a Center for Epidemiologic Studies Depression Scale score >16 indicating depression. The next most common criterion was low physical activity (expenditure of kcal/week). Markers of sarcopenia such as decreased grip strength and decreased gait speed, hallmarks of frailty in the elderly, were the least common of the 5 criteria. Frailty was reversible: 6 frail patients returned for reassessment and only 2 were frail. We conclude that frailty in the HIV-infected patients is potentially reversible and strongly associated with depression and low physical activity, whereas frailty in the elderly is associated with aging-related sarcopenia and is often irreversible.
We have demonstrated the presence of Candida cell surface amyloids that are important in aggregat... more We have demonstrated the presence of Candida cell surface amyloids that are important in aggregation of fungi and adherence to tissue. Fungal amyloid was present in invasive human candidal infections and host serum amyloid P component (SAP) bound to the fungal amyloid. SAP is a protease-resistant glycoprotein that binds avidly to amyloid and interferes with host defence, especially against bacterial pathogens for which neutrophils are important. In this study, we investigated whether biofilm of fungal amyloid and SAP was a feature of other disseminated fungal infections. Tissue specimens from 15 autopsies were systematically evaluated with multiple histochemical stains including thioflavin T and Congo red (dyes that stain amyloid), as well as antibody to SAP. We studied specimens with disseminated aspergillosis, mucormycosis and coccidioidomycosis. The structure of the lesions, host inflammatory cells and the presence of fungal amyloid and SAP were determined. The structure of the lesions was characteristic in aspergillosis ('starburst') and mucormycosis (closely apposed bundles of hyphae). Host inflammatory cells were absent or few in number within these lesions. In Coccidioides lesions, host inflammation was sparse as well. Fungal amyloid was a prominent feature of all lesions along with abundant SAP bound to hyphae and spherules. Fungal amyloid and SAP perhaps contributed to persistence in caseous necrosis lesions. SAP also bound to Aspergillus and Mucorales amyloid in vitro. A biofilm including amyloid and SAP is present in invasive fungal infections. This biofilm may dampen host defence leading to the characteristic sparse inflammatory reaction found in these infections.
Chagas disease caused by T. cruzi is an emerging infectious disease in the United States due to t... more Chagas disease caused by T. cruzi is an emerging infectious disease in the United States due to the immigration of infected individuals from endemic Mexico, Central and South American countries. The American Southwests growing human population has encroached upon the habitat of local triatomines, several of which are competent vectors of T. cruzi among resident small mammals. Human residents are accidental blood meal hosts of these hematophagous bugs. Many human victims suffer anaphylaxis after being bitten by the bugs. We are currently studying the rate of infection by T. cruzi of T. rubida and T. protracta, identifying their blood meal hosts and gathering data on the incidence of anaphylaxis to triatomine bites.
Chagas disease remains the most serious parasitic disease in Latin America with an estimated 10 m... more Chagas disease remains the most serious parasitic disease in Latin America with an estimated 10 million people currently infected with Trypanosoma cruzi, the causative agent. Most people become infected via triatomine insect vectors. Traditionally, taxonomists have attempted to classify the more than 130 species of triatomines by morphological characters to understand their evolutionary relationships and to infer the vector capacity of the species from their shared traits. Morphologically similar species have been organized into species complexes. Although the evolutionary relationships of many South American species have been inferred by extensive molecular studies, North and Central American species have received much less attention. The purpose of this study was to clarify the evolutionary relationships of 10 species of triatomines from North and Central America using two distinct molecular markers. A 339 base pair fragment of the 16S mitochondrial ribosomal subunit and the entir...
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Papers by Stephen Klotz