Aspergillus Endophthalmitis: Epidemiology, Pathobiology, and Current Treatments.

Fungal endophthalmitis is one of the leading causes of vision loss worldwide. Post-operative and traumatic injuries are major contributing factors resulting in ocular fungal infections in healthy and, more importantly, immunocompromised individuals. Among the fungal pathogens, the Aspergillus species, Aspergillus fumigatus, continues to be more prevalent in fungal endophthalmitis patients. However, due to overlapping clinical symptoms with other endophthalmitis etiology, fungal endophthalmitis pose a challenge in its diagnosis and treatment. Hence, it is critical to understand its pathobiology to develop and deploy proper therapeutic interventions for combating Aspergillus infections. This review highlights the different modes of Aspergillus transmission and the host immune response during endophthalmitis. Additionally, we discuss recent advancements in the diagnosis of fungal endophthalmitis. Finally, we comprehensively summarize various antifungal regimens and surgical options for the treatment of Aspergillus endophthalmitis.

Occurrence of extended-spectrum ß-lactamase-producing bacteria in urban Clinton River habitat.

OBJECTIVE: The aim of this study was to determine whether Clinton River water is contaminated with antibiotics and is a reservoir of antimicrobial-resistant bacteria. METHODS: Water samples were taken from two sites of Clinton River. Antimicrobial-resistant bacteria were enumerated on agar plates supplemented with six commonly used antibiotics. Extended-spectrum ß-lactamase (ESBL)-producing bacteria were identified using a BD Phoenix™ System and by 16S rRNA gene sequencing. Antimicrobial resistance gene transfer was performed by conjugation studies and the location of genes was determined by Southern hybridisation. Virulence properties of ESBL-producing isolates were determined by assessing their biofilm-forming ability, cellular toxicity, and induction of an inflammatory response in intestinal epithelial (Caco-2) cells. RESULTS: 16S rRNA analysis of water samples showed the presence of potentially pathogenic bacteria (e.g. Shigella flexneri, Klebsiella pneumoniae, Aeromonas punctata and Pseudomonas aeruginosa). Among 64 biochemically identified bacterial isolates tested, 42% were resistant to cefotaxime, 34% to chloramphenicol, 9% to tetracycline, 11% to ciprofloxacin and 9% to gentamicin. Of 27 cefotaxime-resistant isolates, 11 (41%) were ESBL-positive and possessed either blaCTX-M (n=9), blaTEM (n=1) or blaKPC (n=1). Comparative analysis of ESBL gene sequences from Clinton River water bacteria showed 98-100% identity with clinical isolates. ESBL-producing isolates from Clinton River water were found to form biofilms, induced inflammatory cytokines and caused toxicity to epithelial cells. CONCLUSIONS: Clinton River water contains isolates with ESBL genes identical to clinical isolates and possessing virulence properties, thus it could be a potential reservoir in causing human infections.

Zika virus infects cells lining the blood-retinal barrier and causes chorioretinal atrophy in mouse eyes.

Zika virus (ZIKV) is an important pathogen that causes not only neurologic, but also ocular, abnormalities. Thus, it is imperative that models to study ZIKV pathogenesis in the eye are developed to identify potential targets for interventions. Here, we studied ZIKV interactions with human retinal cells and evaluated ZIKV's pathobiology in mouse eyes. We showed that cells lining the blood-retinal barrier (BRB), the retinal endothelium, and retinal pigment epithelium (RPE) were highly permissive and susceptible to ZIKV-induced cell death. Direct inoculation of ZIKV in eyes of adult C57BL/6 and IFN-stimulated gene 15 (ISG15) KO mice caused chorioretinal atrophy with RPE mottling, a common ocular manifestation of congenital ZIKV infection in humans. This response was associated with induced expression of multiple inflammatory and antiviral (IFNs) response genes in the infected mouse retina. Interestingly, ISG15 KO eyes exhibited severe chorioretinitis, which coincided with increased retinal cell death and higher ZIKV replication. Collectively, our study provides the first evidence to our knowledge that ZIKV causes retinal lesions and infects the cells lining the BRB and that ISG15 plays a role in retinal innate defense against ZIKV infection. Our mouse model can be used to study mechanisms underlying ZIKV-induced chorioretinitis and to gauge ocular antiviral therapies.

Muller glia in retinal innate immunity: a perspective on their roles in endophthalmitis.

Muller cells are the predominant glial cell type in the retina and have a unique anatomy, with processes that span the entire retinal thickness. Although extensive morphological and physiological studies of Muller glia have been performed, much less is known about their role in retinal innate immunity, specifically in infectious endophthalmitis. They were found to express toll-like receptors (TLRs), a major family of pattern recognition receptors that mediate innate responses and provide an important mechanism by which Muller glia are able to sense both pathogen- and host-derived ligands in the vitreous and the retina. An increasing body of evidence suggests that TLR-signaling mediates beneficial effects in the retina via production of proinflammatory cytokines/chemokines, antimicrobial peptides, and neuroprotective growth factors to restore tissue homeostasis. In this review, we discussed retinal innate immunity in general with emphasis on the role of Muller glia in initiating retinal innate defense.

Metabolic memory and diabetic retinopathy: role of inflammatory mediators in retinal pericytes.

Diabetic retinopathy shares many characteristics features of a low grade chronic inflammatory disease. Its progression resists arrest when good metabolic control is re-established after a period of poor metabolic control, suggesting a 'metabolic memory' phenomenon. The aim of this study is to investigate the effect of reversal of high glucose to normal glucose on the inflammatory mediators in pericytes, the site of histopathology in diabetic retinopathy. Bovine retinal pericytes were incubated in high glucose (20 mM) for 2 days followed by normal glucose (5 mM) for 4 days (2 --> 4), or in high glucose for 4 days followed by normal glucose for 4 days (4 --> 4) or 8 days (4 --> 8). Pericytes incubated in continuous normal or high glucose for 2-12 days served as controls. Continuous high glucose exposure for 2-12 days significantly elevated gene expressions and protein concentrations of IL-1 beta, NF-kB, VEGF, TNF-alpha, TGF-beta and ICAM-1 in retinal pericytes. Four days of normal glucose that followed 2 days of high glucose (2 --> 4) had marginal, but significant, beneficial effect on the increases in these inflammatory mediators. Four days of normal glucose in 4 --> 4 group failed to reverse increases in inflammatory mediators and cell apoptosis remained elevated, but addition of dexamethasone during normal glucose exposure ameliorated such increases. However, when normal glucose exposure, after 4 days of high glucose was extended to 8 days (4 --> 8), increases in these mediators were significantly decreased. Hyperglycemia-induced elevations in inflammatory mediators in retinal microvascular cells resist reversal after re-institution of normal glucose conditions. Both, the duration of the initial exposure to high glucose, and normal glucose that follows high glucose, are critical in determining the outcome of the alterations in the inflammatory mediators.

Role of mitochondrial DNA damage in the development of diabetic retinopathy, and the metabolic memory phenomenon associated with its progression.

Diabetic retinopathy does not halt after hyperglycemia is terminated; the retina continues to experience increased oxidative stress, suggesting a memory phenomenon. Mitochondrial DNA (mtDNA) is highly sensitive to oxidative damage. The goal is to investigate the role of mtDNA damage in the development of diabetic retinopathy, and in the metabolic memory. mtDNA damage and its functional consequences on electron transport chain (ETC) were analyzed in the retina from streptozotocin-diabetic rats maintained in poor control (PC, glycated hemoglobin >11%) for 12 months or PC for 6 months followed by good control (GC, GHb < 6.5%) for 6 months. Diabetes damaged retinal mtDNA and elevated DNA repair enzymes (glycosylase). ETC proteins that were encoded by the mitochondrial genome and the glycosylases were compromised in the mitochondria. Re-institution of GC after 6 months of PC failed to protect mtDNA damage, and ETC proteins remained subnormal. Thus, mtDNA continues to be damaged even after PC is terminated. Although the retina tries to overcome mtDNA damage by inducing glycosylase, they remain deficient in the mitochondria with a compromised ETC system. The process is further exacerbated by subsequent increased mtDNA damage providing no relief to the retina from a continuous cycle of damage, and termination of hyperglycemia fails to arrest the progression of retinopathy.

Resistance of retinal inflammatory mediators to suppress after reinstitution of good glycemic control: novel mechanism for metabolic memory.

Diabetic retinopathy resists arrest of its progression after reestablishment of good glycemic control that follows a profound period of poor glycemic control. The objective of this study was to elucidate the role of inflammation in the resistance of retinopathy to arrest after termination of hyperglycemia. Streptozotocin-diabetic rats were (a) maintained either in poor glycemic control [PC group; glycated hemoglobin (GHb)>11%] or in good glycemic control (GC group; GHb<7%) for 12 months or (b) allowed to be in poor glycemic control for 6 months followed by good glycemic control for 6 additional months. At 12 months, retina was analyzed for pro-inflammatory mediators. Twelve months of PC increased retinal interleukin 1beta (IL-1beta) mRNA by 2-fold and its protein expression by 25% compared with the values obtained from normal rat retina. Tumor necrosis factor alpha (TNF-alpha) was elevated approximately 3-fold (both mRNA and protein), and the receptors for IL-1beta and TNF-alpha were increased by 40% each. The concentrations of intercellular cell adhesion molecule 1 and vascular cell adhesion molecule 1 were elevated by 40% and 150%, respectively, and inducible nitric oxide synthase transcripts were elevated by 6-fold. Six months of good glycemic control that followed 6 months of poor glycemic control failed to reverse the elevations in IL-1beta, TNF receptor type I, and intercellular cell adhesion molecule 1 but had some beneficial effects on TNF-alpha, inducible nitric oxide synthase, and vascular cell adhesion molecule 1, however these mediators remained significantly elevated. However, the GC group showed no significant change in the retinal pro-inflammatory mediators compared with the normal rats. Failure to reverse retinal inflammatory mediators supports their important role in the resistance of retinopathy to arrest after cessation of hyperglycemia.

Translocation of H-Ras and its implications in the development of diabetic retinopathy.

H-Ras, a small molecular weight G-protein, undergoes post-translational modifications enabling its translocation from cytosol to the membrane. Hyperglycemia increases apoptosis of retinal capillary cells via activation of H-Ras, which can be ameliorated by farnesylation inhibitors. Our aim is to investigate the mechanism of retinal H-Ras activation in diabetes. H-Ras and Raf-1 were quantified in the retinal membrane and cytosol fractions obtained from streptozotocin-induced diabetes rats, and the role of post-translation modification was determined by investigating the effect of simvastatin on diabetes-induced alterations. The effect of H-Ras-siRNA on membrane translocation and apoptosis was also determined in bovine retinal endothelial cells (BRECs). Diabetes increased expressions of H-Ras and Raf-1 in the retinal membranes, and simvastatin prevented such translocation. Glucose-exposure of BRECs increased membrane H-Ras expression and H-Ras-siRNA prevented this translocation, and also decreased their apoptosis. Thus, membrane translocation of H-Ras is a plausible mechanism responsible for accelerated apoptosis of retinal capillary cells in diabetes.

Oxidative stress and the development of diabetic retinopathy: contributory role of matrix metalloproteinase-2.

Matrix metalloproteinases (MMPs) degrade extracellular matrix and regulate many functions including cell signaling. Oxidative stress is implicated in the development of diabetic retinopathy, and MMP-2, the most ubiquitous member of the MMP family, is sensitive to oxidative stress. This study aimed to determine the regulation of MMP-2 by oxidative stress in the development of diabetic retinopathy and the role of MMP-2 in the apoptosis of retinal capillary cells. The effects of mitochondrial superoxide scavenger on glucose-induced alterations in MMP-2, and its proenzyme activator MT1-MMP and physiological inhibitor TIMP-2, were determined in retinal endothelial cells, and the regulation of their glucose-induced accelerated apoptosis by the inhibitors of MMP-2 was accessed. To confirm in vitro results, the effects of antioxidant supplementation on MMP-2, MT1-MMP, and TIMP-2 were investigated in the retina of streptozotocin-induced diabetic rats. Glucose-induced activation of retinal capillary cell MMP-2 and MT1-MMP and decrease in TIMP-2 were inhibited by superoxide scavengers, and their accelerated apoptosis was prevented by the inhibitors of MMP-2. Antioxidant therapies, which have been shown to inhibit oxidative stress, capillary cell apoptosis, and retinopathy in diabetic rats, ameliorated alterations in retinal MMP-2 and its regulators. Thus, MMP-2 has a proapoptotic role in the loss of retinal capillary cells in diabetes, and the activation of MMP-2 is under the control of superoxide. This suggests a possible use of MMP-2-targeted therapy to inhibit the development of diabetic retinopathy.

Role of glyceraldehyde 3-phosphate dehydrogenase in the development and progression of diabetic retinopathy.

OBJECTIVE: Mitochondrial superoxide levels are elevated in the retina in diabetes, and manganese superoxide dismutase overexpression prevents the development of retinopathy. Superoxide inhibits glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which activates major pathways implicated in diabetic complications, including advanced glycation end products (AGEs), protein kinase C, and hexosamine pathway. Our aim is to investigate the role of GAPDH in the development and progression of diabetic retinopathy and to elucidate the mechanism. RESEARCH DESIGN AND METHODS: Rats with streptozotocin-induced diabetes were in a state of poor control (GHb >11%) for 12 months, good control (GHb <7) soon after induction of diabetes, or poor control for 6 months with 6 months' good control. Retinal GAPDH, its ribosylation and nitration, AGEs, and PKC activation were determined and correlated with microvascular histopathology. RESULTS: In rats with poor control, retinal GAPDH activity and expressions were subnormal with increased ribosylation and nitration (25-30%). GAPDH activity was subnormal in both cytosol and nuclear fractions, but its protein expression and nitration were significantly elevated in nuclear fraction. Reinstitution of good control failed to protect inactivation of GAPDH, its covalent modification, and translocation to the nucleus. PKC, AGEs, and hexosamine pathways remained activated, and microvascular histopathology was unchanged. However, GAPDH and its translocation in good control rats were similar to those in normal rats. CONCLUSIONS: GAPDH plays a significant role in the development of diabetic retinopathy and its progression after cessation of hyperglycemia. Thus, therapies targeted toward preventing its inhibition may inhibit development of diabetic retinopathy and arrest its progression.

Inhibition of retinopathy and retinal metabolic abnormalities in diabetic rats with AREDS-based micronutrients.

OBJECTIVES: To investigate whether the micronutrients that were shown to reduce the risk of development of age-related macular degeneration in the Age-Related Eye Disease Study (AREDS) can have the same effect on the development of diabetic retinopathy in rats, and to understand the possible mechanisms. METHODS: Streptozotocin-induced diabetic rats received a powdered diet with or without supplemental micronutrients (ascorbic acid, vitamin E, beta-carotene, zinc, and copper). The retina was used after the rats had diabetes for 12 months to detect vascular histopathology and to measure the biochemical parameters and messenger RNA levels of the genes involved in oxidative and nitrative stress. RESULTS: The AREDS-based micronutrients prevented a diabetes-induced increase in the number of retinal acellular capillaries. In the same rats, micronutrients inhibited increases in retinal oxidatively modified DNA and nitrotyrosine and decreases in manganese superoxide dismutase. Diabetes-induced alterations in the messenger RNA expression of mitochondrial electron transport complex III (coenzyme Q cytochrome-c reductase) and inducible nitric oxide synthase were also prevented. CONCLUSION: Age-Related Eye Disease Study-based micronutrients inhibit the development of diabetic retinopathy in rodents by inhibiting oxidative and nitrative stress. CLINICAL RELEVANCE: Micronutrients that slow down the onset and progression of age-related macular degeneration have the potential to inhibit the development of diabetic retinopathy.

Diabetes regulates small molecular weight G-protein, H-Ras, in the microvasculature of the retina: implication in the development of retinopathy.

Retinopathy, a largely microvascular complication, affects over 80% of patients with diabetes for 20 years. The purpose of this study is to investigate the effect of diabetes on the activation of H-Ras, a small molecular weight G-protein that regulates cell fate, in the retinal microvessels. Microvessels were prepared from freshly isolated retina from streptozotocin diabetic rats or 30% galactose-fed rats by hypotonic lysis method. Ras activation was quantified by Raf-1 binding assay, and the activation of the signaling proteins, Raf-1 and mitogen activated protein (MAP) kinase, by quantifying their gene transcripts (RTPCR) and/or by protein expression (western blot). Two months of diabetes or experimental galactosemia activated H-Ras (Raf-binding assay) in the retinal microvessels by over 40% and 70% respectively compared to the values obtained from normal rat retinal microvessels. In the same diabetic rats the gene transcripts of H-Ras and its effector protein Raf-1 were elevated by 30% and 135% respectively with their protein expressions elevated by about 25% each, and this was paralleled by similar increases in the protein expressions of H-Ras and Raf-1 in experimentally galactosemic rats. Diabetes increased the gene expression of Ras-Raf-1 downstream signaling protein MAP kinase by over 50%, and that of nuclear transcriptional factor by 25-30%. This activation of H-Ras in retinal microvessels implies that its signaling pathway, in part, could be contributing to the microvascular pathology characteristic of diabetic retinopathy. Comparable activation of H-Ras and its signaling cascade in the retinal microvessels from experimentally galactosemic rats suggests that H-Ras activation is not due to insulin deficiency. Regulation of Ras function could provide important target in the complex approach to inhibit the pathogenesis of diabetic retinopathy.

Metabolic memory phenomenon and accumulation of peroxynitrite in retinal capillaries.

AIM: Diabetic retinopathy resists reversal after good glycemic control (GC) is reinitiated, and preexisting damage at the time of intervention is considered as the major factor in determining the outcome of the GC. This study is to investigate the role of peroxynitrite accumulation in the retinal capillaries in the failure of retinopathy to reverse after reestablishment of GC, and to determine the effect of this reversal on the activity of the enzyme responsible for scavenging mitochondrial superoxide, MnSOD. METHODS: In streptozotocin-diabetic rats, 6 months of poor glycemic control (PC, glycated hemoglobin, GHb > 12.0%) was followed by 6 additional months of GC (GHb about 6%). The trypsin-digested retinal microvessels were prepared for immunostaining of nitrotyrosine (a measure of peroxynitrite) and for counting the number of acellular capillaries (a measure of histopathology). The retina from the other eye was used to quantify nitrotyrosine concentration, MnSOD activity and the total antioxidant capacity. RESULTS: Reversal of hyperglycemia after 6 months of PC had no significant effect on nitrotyrosine concentration in the retina, on the nitrotyrosine-positive retinal capillary cells and on the number of acellular capillaries; the values were similar in PC-GC and PC groups. In the same rats retinal MnSOD activity remained inhibited and the total antioxidant capacity was subnormal 6 months after cessation of PC. CONCLUSIONS: Peroxynitrite accumulation in the retinal microvasculature, the site of histopathology, fails to normalize after reversal of hyperglycemia, and superoxide remains inadequately scavenged. This failure of reversal of peroxynitrite accumulation could be, in part, responsible for the resistance of diabetic retinopathy to reverse after termination of PC.

Oxidative damage in the retinal mitochondria of diabetic mice: possible protection by superoxide dismutase.

PURPOSE: Superoxide levels are elevated in the retina in patients with diabetes, and cytochrome c is released from the mitochondria. The purpose of this study was to elucidate the mechanism involved in the oxidative damage of retinal mitochondria in diabetes and to determine whether mitochondrial superoxide dismutase (MnSOD) provides protection. METHODS: Effects of diabetes were investigated on superoxide and GSH levels, electron transport complexes I and III, and membrane permeability in the isolated mitochondria prepared from the retinas of streptozotocin diabetic mice. To investigate the effect of MnSOD, retinal mitochondrial oxidative stress and electron transport complexes were determined in mice overexpressing MnSOD (MnSOD-Tg). Histopathology was evaluated in trypsin-digested retina. RESULTS: Retinal mitochondria had twofold increase in superoxide levels in nontransgenic (wild-type [WT]) diabetic mice compared with WT nondiabetic mice. In the same retina, diabetes decreased mitochondrial GSH levels by 40% and complex III activity by approximately 20%, and it increased mitochondrial membrane permeability (swelling) by more than twofold; however, complex I activity was not affected. Overexpression of MnSOD inhibited diabetes-induced increases in mitochondrial superoxide levels and membrane permeability and the decrease in complex III activity. GSH values, however, were not statistically different in WT and MnSOD-Tg diabetic mice. In contrast to the diabetes-induced increase in the number of degenerate (acellular) capillaries in WT diabetic mice, the numbers of acellular capillaries in MnSOD-Tg nondiabetic and diabetic mice were similar to those in WT nondiabetic mice. CONCLUSIONS: Retinal mitochondria experience increased oxidative damage in diabetes, and complex III is one of the sources of increased superoxide. MnSOD protects the retina from diabetes-induced abnormalities in the mitochondria and prevents vascular histopathology, strongly implicating the role for MnSOD in the pathogenesis of retinopathy in diabetes.

Effects of curcumin on retinal oxidative stress and inflammation in diabetes.

BACKGROUND: Oxidative stress and inflammation are implicated in the pathogenesis of retinopathy in diabetes. The aim of this study is to examine the effect of curcumin, a polyphenol with antioxidant and anti-inflammatory properties, on diabetes-induced oxidative stress and inflammation in the retina of rats. METHODS: A group of streptozotocin-induced diabetic rats received powdered diet supplemented with 0.05% curcumin (w/w), and another group received diet without curcumin. The diets were initiated soon after induction of diabetes, and the rats were sacrificed 6 weeks after induction of diabetes. The retina was used to quantify oxidative stress and pro-inflammatory markers. RESULTS: Antioxidant capacity and the levels of intracellular antioxidant, GSH (reduced form of glutathione) levels were decreased by about 30-35%, and oxidatively modified DNA (8-OHdG) and nitrotyrosine were increased by 60-70% in the retina of diabetic rats. The levels of interleukin-1beta (IL-1beta) and vascular endothelial growth factor (VEGF) were elevated by 30% and 110% respectively, and the nuclear transcription factor (NF-kB) was activated by 2 fold. Curcumin administration prevented diabetes-induced decrease in the antioxidant capacity, and increase in 8-OHdG and nitrotyrosine; however, it had only partial beneficial effect on retinal GSH. Curcumin also inhibited diabetes-induced elevation in the levels of IL-1beta, VEGF and NF-kB. The effects of curcumin were achieved without amelioration of the severity of hyperglycemia. CONCLUSION: Thus, the beneficial effects of curcumin on the metabolic abnormalities postulated to be important in the development of diabetic retinopathy suggest that curcumin could have potential benefits in inhibiting the development of retinopathy in diabetic patients.

Small molecular weight G-protein, H-Ras, and retinal endothelial cell apoptosis in diabetes.

We have demonstrated that the expressions of small molecular weight G-protein, H-Ras, and its effector protein, Raf-1, are increased in the retina in diabetes, and the specific inhibitors of Ras function inhibit glucose-induced apoptosis of retinal capillary cells. This study is to examine the contributory roles for H-Ras in glucose-induced apoptosis of retinal endothelial cells by genetic manipulation of functionally active H-Ras levels. Bovine retinal endothelial cells were transfected with the plasmids of either wild type (WT), constitutively active (V12) or dominant-negative (N17) H-Ras. Glucose-induced increase in apoptosis, nitric oxide (NO) levels and activation of NF-kappaB and caspase-3 were determined in these genetically manipulated cells. Exposure of bovine retinal endothelial cells to 20 mM glucose significantly increased H-Ras activation as determined by Raf-1 binding assay. Overexpression of V12 in the endothelial cells further increased their glucose-induced apoptosis by 40%, NO levels by about 50%, and activated NF-kappaB and caspase-3 by about 30-40% compared to the untransfected cells incubated in 20 mM glucose. In contrast, overexpression of the inactive mutant, N17, inhibited glucose-mediated increases in apoptotic cell death, NO levels and NF-kappaB and caspase-3 activation; the values were significantly different (p < 0.02) compared to those obtained from the untransfected cells incubated under similar conditions. Our findings demonstrate that H-Ras activation is important in the activation of the specific signaling events leading to the accelerated retinal capillary cell apoptosis in hyperglycemic conditions, suggesting the possible use of H-Ras inhibitors to inhibit the pathogenesis of diabetic retinopathy.

Analysis of genetic diversity among Staphylococcus aureus isolates from patients with deep-seated and superficial staphylococcal infections using pulsed-field gel electrophoresis.

Molecular typing was performed to reveal the genetic diversity among Staphylococcus aureus strains causing deep-seated versus superficial staphylococcal infections. Pulsed-field gel electrophoresis with cluster analysis, plasmid and antimicrobial susceptibility profiling of 50 S. aureus strains collected from these 2 groups of patients were undertaken. A total of 19 (designated A through S) distinct genotypes were identified by PFGE of Sma I-digested genomic DNA. The most prevalent PFGE type was L, which accounted for 30% of isolates and was detected among superficial isolates only. The second most prevalent PFGE type, type A (18%), was predominant among deep-seated isolates. Remaining PFGE types varied in distribution between the 2 groups. Plasmid profile analysis revealed that deep isolates harbour plasmids more frequently (comprising 64% of isolates) than superficial isolates (4%) and showed 10 and 2 distinct patterns, respectively, with pattern 1 being the dominant among deep isolates. Antimicrobial susceptibility data suggested an increased prevalence of antibiotic resistance among deep isolates with the majority (40%) exhibiting identical antibiograms compared to superficial isolates. No resistance was detected against clindamycin and vancomycin. The results of our study indicate a previously unrecognized dichotomy of S. aureus strains, causing deep-seated and superficial infections.

A comparative analysis of antibody repertoire against Staphylococcus aureus antigens in patients with deep-seated versus superficial staphylococcal infections.

Immunoblot and an enzyme-linked immunosorbent assays were used to evaluate and compare IgG antibodies against S. aureus whole cell lysate, cell wall peptidoglycan and lipoteichoic acid to discriminate between deep-seated and superficial S. aureus infection. Serum samples were examined from patients with deep-seated (n = 25) and superficial (n = 25) S. aureus infections and 15 healthy controls. Patients with deep-seated infections exhibited a large number of immuno-reactive bands in their IgG immunoblot profile as compared to those with superficial infections and healthy controls. Anti-staphylococcal IgG antibodies that reacted with two antigens of apparent molecular weight 110 and 98 kDa were specifically present in 96% (24/25) of patients with deep-seated infections, and were absent in, superficial and control sera. Moreover other Gram-positive and Gram-negative bacteria did not share these two unique antigens. The ELISA assays revealed significantly elevated levels of IgG antibodies to peptidoglycan (PG) in 18 of 25 (72%) patients with deep infection and 15 of 25 (60%) patients with superficial staphylococcal infection. The elevated levels of IgG antibodies to teichoic acid (TA) antigen were detected in all (100%) deep-seated group patients and among 40% (10/25) patients with superficial infection. An increase in levels of antibodies to PG showed a positive correlation trend with levels of IgG antibodies to TA only in deep infection group. Thus immunoblot detection of these two unique antigens as well as detection of elevated antibodies against PG and TA may be useful for the discrimination of staphylococcal deep-seated and superficial infection in humans.