RESUMEN
PURPOSE: To determine the ability of diverse S. aureus strains to infect the rabbit cornea following topical inoculation, with special emphasis on a strain of unusual virulence. MATERIALS AND METHODS: S. aureus strains (5 × 10(5) colony forming units; CFU) were topically applied onto scarified rabbit corneas or 100 CFU were intrastromally injected into rabbit corneas. Eyes were scored by slit lamp examination (SLE) and corneas were cultured to determine the log CFU. Polymorphonuclear leukocytes (PMN) were quantified by myeloperoxidase assays and corneas underwent histopathological analysis. Hemolysin titers of S. aureus strains were determined and S. aureus interactions with rabbit tears or human corneal epithelial cells were investigated. RESULTS: All strains injected into the cornea produced high SLE scores and multi-log increases in CFU. Following topical inoculation, four strains produced low SLE scores with no bacterial replication. One strain (UMCR1) topically infected the cornea, causing high SLE scores, extensive PMN infiltration, and multi-log increases in CFU. Histopathologic analysis demonstrated a PMN influx into the UMCR1-infected cornea, destruction of the corneal epithelium, and severe edema. Strain UMCR1 did not demonstrate a high hemolysin titer or resistance to the bactericidal activity of rabbit tears, but did invade human corneal epithelial cells with relatively high efficiency. CONCLUSIONS: One S. aureus strain demonstrated the ability to topically infect the rabbit cornea. This strain was previously found to be unique in its ability to infect the anterior chamber and conjunctiva, suggesting that a key mechanism may be employed to overcome the host defenses of these three ocular sites.
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Úlcera de la Córnea/microbiología , Modelos Animales de Enfermedad , Infecciones Bacterianas del Ojo/microbiología , Infecciones Estafilocócicas/microbiología , Staphylococcus aureus/patogenicidad , Administración Tópica , Animales , Recuento de Colonia Microbiana , Sustancia Propia/microbiología , Úlcera de la Córnea/patología , Infecciones Bacterianas del Ojo/patología , Enfermedades del Sistema Inmune , Trastornos Leucocíticos , Neutrófilos/enzimología , Peroxidasa/metabolismo , Conejos , Infecciones Estafilocócicas/patología , VirulenciaRESUMEN
PURPOSE: To determine the virulence of Staphylococcus aureus strains in the rabbit conjunctiva. METHODS: Three strains of methicillin-sensitive S. aureus (8325-4, Newman, and UMCR1) and two strains of methicillin-resistant S. aureus (70490 and MW2) were analyzed. Rabbit bulbar conjunctivas (n ≥ 6 per group) were injected with 10(5) colony forming units (CFU) in 10 µl. Eyes were photographed and analyzed for pathology at 20 hr postinfection (PI) using slit lamp examination (SLE) to measure five parameters on a scale from 0 (normal) to 4 (severe): injection, chemosis, iritis, corneal edema, and pinpoint conjunctival hemorrhages. The parameter grades were added to produce a SLE score. Bacteria were enumerated and histopathological analysis was done at 20 hr PI. Myeloperoxidase assays were performed on conjunctival swabs (n ≥ 3 per strain) at 0 and 20 hr PI. RESULTS: Conjunctivas injected with 8325-4 or Newman had SLE scores of 1.67 ± 0.12 and 0.81 ± 0.16, respectively. Strain 70490 produced an average SLE score of 2.94 ± 0.47, whereas MW2 produced a score of 5.04 ± 0.73. UMCR1 produced severe conjunctivitis having a SLE score of 13.25 ± 0.80. Only strain UMCR1 grew in the conjunctiva showing a 2.7 log increase in CFU; all other strains remained near the inoculated numbers or decreased as much as 1.85 logs. Myeloperoxidase activity was greatest in the tear film of UMCR1 infected eyes with over one million PMN present at 20 hr PI. CONCLUSIONS: Only one S. aureus strain, UMCR1, was able to cause a reproducible severe conjunctivitis. This conjunctival infection could be used to test new antimicrobials and to help understand the pathogenesis of conjunctivitis, especially in terms of overcoming the host defenses.
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Conjuntivitis Bacteriana/microbiología , Staphylococcus aureus Resistente a Meticilina/patogenicidad , Infecciones Estafilocócicas/microbiología , Animales , Recuento de Colonia Microbiana , Modelos Animales de Enfermedad , Meticilina/farmacología , Staphylococcus aureus Resistente a Meticilina/aislamiento & purificación , Neutrófilos/enzimología , Peroxidasa/metabolismo , Conejos , Staphylococcus aureus/efectos de los fármacos , Staphylococcus aureus/patogenicidad , VirulenciaRESUMEN
INTRODUCTION: antibiotic and steroid combination therapies, such as tobramycin with dexamethasone, are often used in ophthalmology to treat or prevent infection and inflammation. The purpose of this study was to use a model of Staphylococcus aureus keratitis to quantify and compare the effectiveness of a standard tobramycin and dexamethasone combined therapy, with each drug individually, and with a new formulation of the two drugs in a xanthan gum vehicle. METHODS: rabbit corneas were intrastromally injected with a methicillin-sensitive S. aureus (MSSA) or a methicillin-resistant S. aureus (MRSA) strain. Rabbit eyes were treated every hour from 10 to 15 hours postinfection (PI) with 0.1% dexamethasone, 0.3% tobramycin, 0.3% tobramycin with 0.1% dexamethasone, or 0.3% tobramycin with 0.05% dexamethasone in a xanthan gum vehicle (ST). Slit lamp examinations (SLE) were performed on infected eyes and pathology scored at 15 hours PI. At 16 hours PI, colony forming units (CFUs) per cornea were quantified. RESULTS: the CFUs in eyes treated with dexamethasone alone were similar to untreated control eyes for MSSA or MRSA infections. All other treatment groups had significantly less CFUs per cornea than untreated eyes. The eyes treated with the ST formulation had significantly fewer CFUs per cornea than all other treatment groups when infected with MSSA or MRSA. The SLE scores of MSSA or MRSA infected eyes treated with tobramycin alone were similar to untreated control eyes. All other treatment groups had significantly lower SLE scores than untreated controls eyes, but were not significantly different from each other. CONCLUSION: the results of this study demonstrated that the tobramycin and dexamethasone combination therapy with a xanthan gum vehicle has an improved bactericidal effectiveness compared to the commercially available formulation, and maintains a similar anti-inflammatory effect while containing half the amount of steroid.
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Antibacterianos/administración & dosificación , Infecciones Bacterianas del Ojo/tratamiento farmacológico , Queratitis/tratamiento farmacológico , Polisacáridos Bacterianos/administración & dosificación , Prednisolona/administración & dosificación , Infecciones por Pseudomonas/tratamiento farmacológico , Tobramicina/administración & dosificación , Animales , Recuento de Colonia Microbiana , Córnea/efectos de los fármacos , Dexametasona/administración & dosificación , Modelos Animales de Enfermedad , Quimioterapia Combinada , Queratitis/microbiología , ConejosRESUMEN
PURPOSE: Staphylococcus aureus is an important cause of ocular infections including endophthalmitis. The purpose of this study was to determine the ability of a relatively large molecule, such as lysostaphin, to remain in the rabbit aqueous humor for extended periods while retaining its bactericidal activity. METHODS: Lysostaphin, gatifloxacin, or Tris-buffered saline (TBS) was injected into the rabbit anterior chamber. Aqueous humor was sampled at 0.5, 1, 2, 3, and 4 days after injection, and then assayed for bactericidal activity against S. aureus. The anterior chamber of treated eyes was also challenged 2 days after treatment by an infection of S. aureus. The surviving bacteria were quantified to determine bactericidal effectiveness in the anterior chamber. The aqueous humor of lysostaphin injected eyes was assayed by western blot for the presence of the molecule 2 days post-injection. RESULTS: The bactericidal activity of lysostaphin was confirmed by lysis of S. aureus and sensitivity to zinc. Eyes injected with lysostaphin showed no adverse reactions. Aqueous humor of gatifloxacin injected eyes demonstrated no greater effectiveness than that of TBS injected eyes in vitro at any time point assayed, whereas lysostaphin injected eyes retained potent bactericidal activity for at least 3 days. In an in vivo challenge, the anterior chamber of lysostaphin injected eyes retained significant bactericidal activity for at least 2 days after treatment, whereas gatifloxacin injected eyes demonstrated no significant difference from those injected with TBS. Western blot analysis demonstrated the presence of lysostaphin in the aqueous humor 2 days post-injection. CONCLUSIONS: Lysostaphin demonstrated the ability to remain in the aqueous humor for days while maintaining its bactericidal activity, an indication that a high molecular weight antimicrobial can provide prolonged prophylactic protection of the anterior chamber.
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Antiinfecciosos Locales/administración & dosificación , Humor Acuoso/microbiología , Lisostafina/administración & dosificación , Infecciones Estafilocócicas/tratamiento farmacológico , Staphylococcus/efectos de los fármacos , Animales , Antiinfecciosos/administración & dosificación , Antiinfecciosos Locales/farmacocinética , Humor Acuoso/metabolismo , Western Blotting , Fluoroquinolonas/administración & dosificación , Gatifloxacina , Técnicas In Vitro , Inyecciones Intraoculares , Lisostafina/farmacocinética , Pruebas de Sensibilidad Microbiana , Conejos , Factores de TiempoRESUMEN
PURPOSE: To describe and characterize a Staphylococcus aureus strain with unique virulence that overcomes host defenses of the rabbit anterior chamber and mimics clinical cases of postcataract surgery endophthalmitis. METHODS: Nine isolates of S. aureus were tested to determine their viability in the rabbit anterior chamber. Growth of UMCR1 in the anterior chamber was established and expressed as log colony-forming units per milliliter of aqueous humor. Pathologic changes produced by UMCR1 were documented by photographs, slit lamp examination, histopathologic analysis, and quantification of neutrophils. UMCR1 was characterized by antibiotic susceptibility, biochemical tests, ribotyping, genome restriction mapping, and multilocus sequence typing (MLST). RESULTS: UMCR1 was the only S. aureus strain that grew within the anterior chamber, reaching log 6.97 ± 0.18 CFU/mL by 16 hours after infection. Pathologic changes included conjunctival injection, chemosis, corneal edema, severe iritis, fibrin accumulation, and a 193-fold increase in neutrophils by 16 hours after infection. UMCR1 was only resistant to sulfamethoxazole and, like other S. aureus isolates, polymyxin B. UMCR1 also had biochemical reactions and a ribotype pattern typical of S. aureus. The genomic reconstruction analysis of UMCR1 was most similar to strains MW2 and MSSA476. MLST revealed a 1 in 3198 nucleotide difference between UMCR1 and strains MW2 and MSSA476. CONCLUSIONS: This study describes a unique S. aureus strain that overcomes host defenses and replicates in the anterior chamber. The survival and growth of this organism could be used for studies of S. aureus pathogenesis, host defenses, and effectiveness of antibiotics within the anterior chamber.
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Cámara Anterior/microbiología , Endoftalmitis/microbiología , Infecciones Bacterianas del Ojo/microbiología , Infecciones Estafilocócicas/microbiología , Staphylococcus aureus/genética , Staphylococcus aureus/patogenicidad , Animales , Antibacterianos/farmacología , Humor Acuoso/inmunología , Secuencia de Bases , Recuento de Colonia Microbiana , Edema Corneal/microbiología , Farmacorresistencia Bacteriana , Endoftalmitis/patología , Infecciones Bacterianas del Ojo/patología , Iritis/microbiología , Pruebas de Sensibilidad Microbiana , Datos de Secuencia Molecular , Neutrófilos/inmunología , Reacción en Cadena de la Polimerasa , Conejos , Ribotipificación , Organismos Libres de Patógenos Específicos , Infecciones Estafilocócicas/patología , VirulenciaRESUMEN
BACKGROUND: Streptococcus pneumoniae is a common cause of bacterial keratitis, and models to examine the ocular pathogenesis of this bacterium would aid in efforts to treat pneumococcal keratitis. The aim of this study was to establish a murine model of pneumococcal keratitis. METHODS: The corneas of A/J, BALB/c or C57BL/6 mice were scratched and topically infected with a clinical strain of S. pneumoniae. Slitlamp examination (SLE), enumeration of bacteria in the corneas and histology were performed. RESULTS: Bacteria were recovered from the eyes of A/J mice on postinfection (PI) days 1 [1.96 +/- 0.61 log(10) colony-forming units (CFU)] and 3 (1.41 +/- 0.71 log(10) CFU). SLE scores were significantly higher in the infected A/J mice as compared to the BALB/c or C57BL/6 mice on PI day 3 (p < 0.0001) and steadily increased over time, reaching a maximal value of 3.00 +/- 0.35 on PI day 10. Histopathology revealed stromal edema and the influx of polymorphonuclear leukocytes on PI days 7 and 10, and corneal disruption on PI day 7. CONCLUSIONS: S. pneumoniae keratitis was established in A/J mice, but not BALB/c or C57BL/6 mice.
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Modelos Animales de Enfermedad , Infecciones Bacterianas del Ojo/microbiología , Queratitis/etiología , Infecciones Neumocócicas/microbiología , Streptococcus pneumoniae/aislamiento & purificación , Animales , Córnea/microbiología , Córnea/patología , Edema Corneal/etiología , Edema Corneal/patología , Infecciones Bacterianas del Ojo/complicaciones , Infecciones Bacterianas del Ojo/patología , Interacciones Huésped-Patógeno , Humanos , Queratitis/patología , Ratones , Ratones Endogámicos , Neutrófilos/patología , Infecciones Neumocócicas/complicaciones , Infecciones Neumocócicas/patologíaRESUMEN
PURPOSE: To analyze PASP in terms of its gene distribution and expression, its corneal pathologic effects, its enzymatic properties, and the protectiveness of the immune response to this protease. METHODS: Twenty-five strains of P. aeruginosa were analyzed for the PASP gene and secreted protein by PCR and Western blot analysis, respectively. Active recombinant (r)PASP (10 microg/20 microL) or heat-inactivated rPASP was intrastromally injected into rabbit corneas. Pathologic changes were monitored by slit lamp examination (SLE) and histopathology. Purified rPASP was assayed for cleavage of collagens and susceptibility to TLCK. Rabbit antibody to rPASP was produced and tested for enzyme inactivation, and actively immunized rabbits were challenged by intrastromal injection of active rPASP (5 microg). RESULTS: All 25 strains of P. aeruginosa analyzed were positive for the PASP gene and protein. SLE scores of eyes injected with active rPASP were significantly higher than control eyes at all postinjection times (PI; P
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Enfermedades de la Córnea/microbiología , Infecciones Bacterianas del Ojo/microbiología , Regulación Bacteriana de la Expresión Génica/fisiología , Infecciones por Pseudomonas/microbiología , Pseudomonas aeruginosa/genética , Serina Endopeptidasas/fisiología , Animales , Western Blotting , Quimiotaxis de Leucocito , Colágeno/metabolismo , Córnea/efectos de los fármacos , Córnea/metabolismo , Enfermedades de la Córnea/enzimología , Ensayo de Inmunoadsorción Enzimática , Infecciones Bacterianas del Ojo/enzimología , Inyecciones , Neutrófilos/fisiología , Reacción en Cadena de la Polimerasa , Infecciones por Pseudomonas/enzimología , Conejos , Proteínas Recombinantes/farmacologíaRESUMEN
PURPOSE: alpha-Toxin mediates extreme corneal damage during Staphylococcus aureus keratitis. Chemical inhibition of this toxin was sought to provide relief from toxin-mediated pathology. METHODS: Inhibition of alpha-toxin by phosphate-buffered saline (PBS), 0.1% methyl-beta-cyclodextrin (CD), or CD plus cholesterol (0.1%, CD-cholesterol) was assayed by hemolysis of rabbit erythrocytes. Pathologic changes in rabbit corneas injected with 12 hemolytic units of alpha-toxin suspended in PBS, 1% CD, or 1% CD-cholesterol were compared over time. Rabbit corneas injected with 10(2) colony forming units (CFU) of S. aureus were treated from 7 to 13 hours postinfection (PI) with a total of 15 drops of CD-cholesterol, CD, or PBS. Slit lamp examination (SLE) and measurement of erosions were performed at 13 hours PI and bacteria were quantified at 14 hours PI. RESULTS: Toxin-mediated lysis of erythrocytes was inhibited up to 16,000-fold in the presence of CD-cholesterol compared with CD or PBS. Eyes injected with alpha-toxin mixed with CD-cholesterol had, at 7 hours postinjection, significantly smaller erosions than eyes injected with alpha-toxin in PBS or alpha-toxin mixed with CD (P = 0.0090 and P = 0.0035, respectively). Eyes infected with S. aureus and treated with CD-cholesterol had significantly lower SLE scores than eyes treated with CD or PBS (P
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Toxinas Bacterianas/antagonistas & inhibidores , Colesterol/farmacología , Úlcera de la Córnea/prevención & control , Infecciones Bacterianas del Ojo/prevención & control , Proteínas Hemolisinas/antagonistas & inhibidores , Toxoide Estafilocócico/antagonistas & inhibidores , Factores de Virulencia/antagonistas & inhibidores , beta-Ciclodextrinas/farmacología , Animales , Córnea/microbiología , Úlcera de la Córnea/microbiología , Úlcera de la Córnea/patología , Modelos Animales de Enfermedad , Quimioterapia Combinada , Eritrocitos/efectos de los fármacos , Exotoxinas/antagonistas & inhibidores , Infecciones Bacterianas del Ojo/microbiología , Infecciones Bacterianas del Ojo/patología , Hemólisis , Conejos , Cloruro de Sodio/farmacología , Infecciones Estafilocócicas/microbiología , Infecciones Estafilocócicas/patología , Infecciones Estafilocócicas/prevención & control , Staphylococcus aureus/fisiología , Virulencia/fisiologíaRESUMEN
PURPOSE: To develop a rabbit model of post-laser in situ keratomileusis (LASIK) methicillin-resistant Staphylococcus aureus (MRSA) keratitis for studying fluoroquinolone prophylaxis and treatment. SETTING: Department of Microbiology, University of Mississippi Medical Center, Jackson, Mississippi, USA. METHODS: An MRSA keratitis isolate (5 microL, 500 colony forming units [CFU]) was inoculated underneath a corneal flap. Bacterial growth and pathology were determined by quantitative cultures (CFU) and slitlamp examination, respectively. The effectiveness of commercial moxifloxacin and gatifloxacin formulations was compared in 3 regimens: prophylaxis (4 drops before inoculation), early therapy (single drop hourly from 4 to 9 hours postinfection), and late therapy (single drop hourly from 10 to 15 hours postinfection). Zones of bacterial inhibition to known in vivo antibiotic concentrations were determined. RESULTS: Bacteria grew to a maximum of approximately 10(6) CFU/cornea within 10 hours postinfection. The slitlamp examination scores showed pathologic changes beginning 10 hours postinfection and progressed throughout the infection. For prophylaxis, eyes treated with moxifloxacin had significantly fewer CFU than gatifloxacin-treated eyes or untreated controls (both P < or = .0001). During early treatment, the antibiotics were equally effective in reducing CFU relative to untreated controls (P < or = .0001). In late treatment, gatifloxacin and moxifloxacin caused significant reductions in CFU relative to untreated controls (P < or = .0007 and P < or = .0001, respectively). Moxifloxacin produced zones of bacterial inhibition significantly larger than those produced by gatifloxacin. CONCLUSIONS: Methicillin-resistant S aureus inoculation beneath a rabbit corneal flap produced an infection that was useful for quantitative microbiological studies. A significant advantage in using moxifloxacin relative to gatifloxacin was observed in prophylaxis of keratitis (P = .0001).
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Antiinfecciosos/uso terapéutico , Úlcera de la Córnea/tratamiento farmacológico , Modelos Animales de Enfermedad , Infecciones Bacterianas del Ojo/tratamiento farmacológico , Fluoroquinolonas/uso terapéutico , Resistencia a la Meticilina , Infecciones Estafilocócicas/tratamiento farmacológico , Animales , Compuestos Aza/uso terapéutico , Recuento de Colonia Microbiana , Sustancia Propia/microbiología , Úlcera de la Córnea/microbiología , Infecciones Bacterianas del Ojo/microbiología , Gatifloxacina , Queratomileusis por Láser In Situ , Moxifloxacino , Complicaciones Posoperatorias , Quinolinas/uso terapéutico , Conejos , Organismos Libres de Patógenos Específicos , Infecciones Estafilocócicas/microbiología , Staphylococcus aureus/efectos de los fármacos , Staphylococcus aureus/fisiología , Colgajos Quirúrgicos/microbiologíaRESUMEN
PURPOSE: To analyze age-related changes in susceptibility to experimental Staphylococcus aureus keratitis and purified alpha-toxin in rabbits. METHODS: Intrastromal injection of S. aureus (100 colony-forming units [CFUs]) induced keratitis in young (6-8 weeks) and aged (approximately 30 months) New Zealand White rabbits. Bacteria and polymorphonuclear leukocytes (PMNs) per cornea were quantified. Purified alpha-toxin at 1, 10, 25, or 50 hemolytic units (HU) or heat-inactivated alpha-toxin was intrastromally injected into corneas, and pathologic changes were determined by slit lamp examination (SLE) and histopathologic analysis. alpha-Toxin hemolysis assays were performed using erythrocytes from young and aged rabbits. RESULTS: S. aureus keratitis produced significantly higher SLE scores in young rabbits than in aged rabbits at 15, 20, and 25 hours postinfection (PI; P < or = 0.001); aged rabbits essentially recovered from S. aureus keratitis by 7 days PI. At 25 hours PI, numbers of CFUs and PMNs in corneas of young and aged rabbits were equivalent (P > or = 0.6); the bacterial burden in aged rabbits declined by 5 logs per cornea from day 1 to day 7 PI. Intrastromal injection of > or =10 HU alpha-toxin also produced significantly more disease in young than in aged rabbit corneas (P < or = 0.05), whereas 1 HU or heat-inactivated toxin yielded negligible pathologic changes in either group. Hemolysis assays of erythrocytes from young rabbits demonstrated greater susceptibility to alpha-toxin compared with those from aged rabbits. CONCLUSIONS: Corneas and erythrocytes of young rabbits, relative to aged rabbits, are significantly more susceptible to S. aureus keratitis and to alpha-toxin.
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Envejecimiento/fisiología , Úlcera de la Córnea/microbiología , Modelos Animales de Enfermedad , Infecciones Bacterianas del Ojo/microbiología , Infecciones Estafilocócicas/microbiología , Staphylococcus aureus/patogenicidad , Animales , Toxinas Bacterianas/administración & dosificación , Recuento de Colonia Microbiana , Sustancia Propia/efectos de los fármacos , Sustancia Propia/inmunología , Sustancia Propia/microbiología , Úlcera de la Córnea/patología , Susceptibilidad a Enfermedades , Infecciones Bacterianas del Ojo/patología , Proteínas Hemolisinas/administración & dosificación , Inyecciones , Neutrófilos/fisiología , Peroxidasa/metabolismo , Conejos , Infecciones Estafilocócicas/patología , Staphylococcus aureus/aislamiento & purificación , Staphylococcus aureus/fisiología , VirulenciaRESUMEN
PURPOSE: The purpose of this study was to determine whether cholesterol, the host cell receptor for pneumolysin of Streptococcus pneumoniae, could effectively treat pneumococcal keratitis. METHODS: New Zealand White rabbits were intrastromally injected with 10(5) colony-forming units (CFUs) of S. pneumoniae D39. Corneas were treated with topical drops of 1% cholesterol every 2 hours beginning 25 hours after infection and were examined by slit lamp microscopy 24, 36, and 48 hours after infection. Rabbits were killed, and CFUs were recovered from the corneas after the final slit lamp examination (SLE). Minimal inhibitory concentration (MIC) assays of cholesterol against bacteria were performed. Specific inhibition of pneumolysin by cholesterol in the rabbit cornea was tested by intrastromal injection of pneumolysin with or without cholesterol and was compared with cholesterol inhibition of pneumolysin in vitro using hemolysis assays with rabbit erythrocytes. RESULTS: Corneas treated with cholesterol had significantly lower SLE scores 48 hours after infection than corneas treated with vehicle (P = 0.0015). Treated corneas also had significantly less log(10) CFUs than vehicle-treated corneas (P = 0.0006). Cholesterol at a 1% concentration was bactericidal to bacteria in vitro, and lower concentrations of cholesterol were partially inhibitory in a concentration-dependent manner. Cholesterol also specifically inhibited 1 mug pneumolysin in vivo and up to 50 ng pneumolysin in vitro. CONCLUSIONS: Topical cholesterol is an effective treatment for S. pneumoniae keratitis. Cholesterol not only inhibits pneumolysin, it is also bactericidal.
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Colesterol/uso terapéutico , Úlcera de la Córnea/tratamiento farmacológico , Infecciones Bacterianas del Ojo/tratamiento farmacológico , Infecciones Neumocócicas/tratamiento farmacológico , Streptococcus pneumoniae/aislamiento & purificación , Estreptolisinas/antagonistas & inhibidores , Animales , Proteínas Bacterianas/antagonistas & inhibidores , Colesterol/administración & dosificación , Colesterol/farmacología , Recuento de Colonia Microbiana , Córnea/efectos de los fármacos , Córnea/microbiología , Úlcera de la Córnea/microbiología , Infecciones Bacterianas del Ojo/microbiología , Pruebas de Sensibilidad Microbiana , Soluciones Oftálmicas/administración & dosificación , Soluciones Oftálmicas/farmacología , Soluciones Oftálmicas/uso terapéutico , Infecciones Neumocócicas/microbiología , Conejos , Streptococcus pneumoniae/crecimiento & desarrolloRESUMEN
PURPOSE: To quantitatively determine the effectiveness of lysostaphin therapy for experimental endophthalmitis mediated by coagulase-negative Staphylococcus species, the leading cause of postsurgical endophthalmitis. METHODS: Minimal inhibitory concentrations (MIC) of lysostaphin were determined for 54 isolates representing the following species: S. epidermidis, S. warneri, S. haemolyticus, S. cohnii, S. simulans, and S. capitis. The effectiveness of lysostaphin therapy was tested in an experimental model of endophthalmitis by intravitreally injecting log phase bacteria (100 colony-forming units; cfu) into rabbit eyes (n = 3 eyes per group). At 8 hr postinfection (PI), lysostaphin (250 microg) was injected intravitreally, and the number of cfu/ml of vitreous was determined at 24 hr PI. RESULTS: Average MIC for S. epidermidis was 0.7 microg/ml for 90% of the 33 strains tested. Six methicillin-resistant strains of S. epidermidis (MRSE) had an average MIC of 0.74 micro g/ml. All other species had MIC values of =1.1 microg/ml, except for one strain of S. capitis (MIC = 15.6 microg/ml) and one S. haemolyticus (MIC = 1.41 microg/ml). At 24 hr PI, all untreated eyes had between 5.7 and 8.08 log cfu/ml vitreous humor. Treatment with lysostaphin significantly reduced the cfu/ml as compared with untreated eyes for 13 strains tested in vivo (p = 0.020), but not for two S. haemolyticus strains (p = 0.13), two MRSE strains (p = 0.544), or one S. cohnii strain (p = 0.1366). Treatment with lysostaphin reduced the cfu/ml of methicillin-sensitive S. epidermidis strains by 6 logs; for S. warneri, there was a 2 log reduction; and for the other species a 4 log reduction in cfu/ml relative to untreated eyes. CONCLUSIONS: Lysostaphin was mostly effective in treating coagulase-negative staphylococcal experimental endophthalmitis.
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Antiinfecciosos Locales/uso terapéutico , Endoftalmitis/tratamiento farmacológico , Infecciones Bacterianas del Ojo/tratamiento farmacológico , Lisostafina/uso terapéutico , Infecciones Estafilocócicas/tratamiento farmacológico , Animales , Antiinfecciosos Locales/administración & dosificación , Modelos Animales de Enfermedad , Endoftalmitis/microbiología , Infecciones Bacterianas del Ojo/microbiología , Inyecciones , Lisostafina/administración & dosificación , Conejos , Infecciones Estafilocócicas/microbiología , Staphylococcus/aislamiento & purificación , Resultado del Tratamiento , Cuerpo Vítreo/microbiologíaRESUMEN
PURPOSE: Determine the ocular virulence of noncapsular Streptococcus pneumoniae in a rabbit keratitis model. METHODS: Mice were infected intraperitoneally with 10(5) colony-forming units (CFUs) of Avery's strain (capsular type 2) or strain R6 (a noncapsular derivative of type 2), and mortality was monitored daily. In addition, 10(5) CFU of each strain was injected into rabbit corneas. Bacterial loads in rabbit corneas were determined at 20 or 48 hours after infection. Slit lamp examination (SLE) of rabbit eyes was performed at 24, 36, and 48 hours after infection. Controls included corneas inoculated with bacterial suspension medium and UV-killed bacteria. RESULTS: One hundred percent mortality was observed in mice infected intraperitoneally with the encapsulated strain at 2 days after infection, whereas all mice infected with the nonencapsulated strain survived for 21 days. The nonencapsulated strain caused the same pathologic effects in the rabbit cornea as the encapsulated strain at 24, 36, and 48 hours after infection (P > or = 0.080). Control corneas showed no pathologic effects and had significantly lower SLE scores than corneas infected with live bacteria (P < or = 0.001). Mean bacteria log CFU +/- SEM recovered at 20 hours after infection were 7.069 +/- 0.094 for the encapsulated and 6.533 +/- 0.116 for the nonencapsulated strain (P = 0.001). Bacteria recovered from the corneas at 48 hours after infection were 6.712 +/- 0.349 and 1.807 +/- 0.462 for the encapsulated and nonencapsulated strains, respectively (P < 0.001). CONCLUSIONS: The S. pneumoniae noncapsular strain was as virulent in the rabbit cornea as was the encapsulated strain, but unlike the encapsulated strain, was avirulent in the mouse peritoneum.