Survival of Pseudomonas aeruginosa in M-K preserved corneas

AIM

To present seven eyes of suspected donor to host transmitted Pseudomonas sp corneal graft infection after corneal and scleral graft leading to corneal melting within 24 hours, in a span of 10 months.

METHODS

Case series. Seven eyes, operated for either penetrating or lamellar keratoplasty or scleral patch graft for different indications and which developed massive corneal/corneoscleral infection within 24 hours, were studied prospectively.

RESULTS

Pseudomonas aeruginosa, resistant to almost all antibiotics except polymyxin B in all and vancomycin in two, was identified as the causative organism from all the specimens obtained from the infected graft.

CONCLUSION

Post-keratoplasty infection is a disaster. The source of early infection is invariably iatrogenic. Use of empirical antibiotics in the media is not always sufficient to prevent such infection. Thus, measures must be taken in the form of strict maintenance of asepsis and revision of antibiotics added to the storage medium. Further, early recognition and energetic therapy for such infection could reduce the ophthalmic morbidity.

Laboratory diagnosis in ulcerative keratitis

AIMS

To identify the common bacterial and fungal isolates from corneal ulcers and to determine the antimicrobial susceptibility patterns of bacterial isolates to commonly used antibiotics at B.P. Koirala Institute of Health Sciences (BPKIHS), eastern Nepal. Culture and direct microscopic correlation and reliability were also compared.

METHODS

All patients with suspected corneal ulceration presenting to the Ophthalmology Department of BPKIHS from 1st August 1998 to 31st July 2001 were evaluated. Corneal scraping was performed and processed for direct microscopy and culture for bacterial and fungal isolates. Bacterial isolates were subjected to antimicrobial susceptibility testing.

RESULTS

Of 447 specimens examined direct microscopy was positive in 216 (48%) specimens. Culture positivity could be correlated with direct microscopy in 179 (83%) of specimens. Growth of etiologic agents was found in 303 (67.8%) samples. Of these 145 (47.8%) had pure fungal growth, 103 (34%) had pure bacterial growth and 55 (18.2%) had mixed fungal and bacterial infection. The commonest fungal pathogen was Aspergillus spp.in 78 (38.4%) followed by Fusarium spp. in 45 (22%). Aureobasidium sp. was isolated in 25 (12.3%) samples. Staphylococcus aureus (93, 56.7%) dominated the scene as the commonest bacterial agent. Streptococcus pneumoniae (33, 20%) was second in the list. Most of the bacterial isolates were sensitive to commonly used antibiotics.

CONCLUSION

This study emphasizes the importance and need of the continued surveillance of the agents and their antimicrobial susceptibility for the prevention and management of corneal ulcers and their complications.

Evaluating role of oxidative stress in determining the pathogenesis of falciparum malaria induced acute renal failure

Serum malondialdehyde was measured in sixty-one falciparum malaria cases, which include thirty uncomplicated, and thirty-one complicated with acute renal failure. Twenty-six healthy individuals were also studied as controls. Serum malondialdehyde level was found to be significantly elevated in falciparum malaria induced acute renal failure cases when compared with uncomplicated falciparum malaria (p<0.001) and healthy controls (p<0.001). A positive correlation with the raised urea, creatinine and bilirubin levels were significant (r=0.62, p<0.025; r=0.65, p<0.05 and r=0.72, p<0.001 respectively) indicating the severity of complication with rise of lipid peroxides in falciparum malaria induced acute renal failure cases.

Recombinant Newcastle disease virus as a vaccine vector

Veterinary vaccines remained conventional for more than fifty years. Recent advances in the recombinant genetic engineering techniques brought forward a leap in designing vaccines for veterinary use. A novel approach of delivering protective immunogens of many different pathogens in a single virus vector was made possible with the introduction of a "reverse genetics" system for nonsegmented negative-sense RNA viruses. Newcastle disease virus (NDV), a nonsegmented negative-sense virus, is one of the major viruses of economic importance in the poultry industry throughout the world. Despite the availability of live virus vaccines of good potency, the intrinsic ability of attenuated strains to revert in virulence makes control of this disease by vaccination difficult. Armed with the knowledge of virulence factors of this virus, it is now possible to produce genetically stable vaccines and to engineer mutations that enhance immunogenicity. The modular nature of the genome of this virus facilitates engineering additional genes from several different pathogens or tumor-specific antigens to design contemporary vaccines for animals and humans. This review will summarize the developments in using NDV as a vaccine vector and the potential of this approach in designing next generation vaccines for veterinary use.

CT in the diagnosis of isolated cysticercal infestation of extraocular muscle

AIM

To evaluate the use of computed tomography (CT) and ultrasound (US) to diagnose orbital cysticercosis, and present the diagnostic features.

METHOD

US and CT were used to evaluate patients with proptosis. Four patients were diagnosed as having orbital myocysticercosis and treated with oral albendazole and corticosteroid. Follow-up was undertaken with US and CT.

RESULT

US features were confirmatory of myocysticercosis in two eyes where as CT was effective in diagnosing the condition in all four eyes. In two patients the medial rectus was involved, in one the superior rectus and, in the other, the inferior rectus muscles. Serial US and CT revealed complete resolution of the lesions in 3 months.

CONCLUSION

CT is useful method in diagnosing isolated orbital myocysticercosis. Our report demonstrated that ophthalmic signs and symptoms in the presence of proptosis, especially in an endemic region, should alert the clinician to the possibility of myocysticercosis. Though CT is superior, US can be used as a economical follow-up investigation.

Role of aprotinin in the management of experimental fungal keratitis

In an experimentally induced Aspergillus fumigatus fungal keratitis in 20 rabbits, aprotinin, an antiplasmin agent, was studied to find out its role as an adjuvant when given along with other established antifungal agents like natamycin and fluconazole. The 20 rabbits included in this study were randomly divided into four equal treatment groups. Once the ulcer was produced after intrastromal injection of 0.03 ml of A. fumigatus (5.5 x 10(4) spores/ml), different drugs/agents in combination were used in a randomized manner. These were natamycin (5%) + placebo, natamycin + aprotinin (40 IU/ml), fluconazole (0.3%) + placebo and fluconazole + aprotinin. The rabbits were followed up every day to note the signs of healing which included subsidence of corneal infiltration, disappearance of stromal abscess and subsidence of corneal oedema till complete healing. Results showed that the average healing time was 28.2, 28.4, 49.8 and 49.0 days for natamycin + placebo, natamycin + aprotinin, fluconazole + placebo and fluconazole + aprotinin, respectively. It suggests that aprotinin as an adjuvant has no definite role in the management of fungal keratitis. The plasminogen activator-plasmin system which is inhibited by aprotinin may not be the pathway through which filamentous fungi like A. fumigatus cause tissue destruction.

Glutathione peroxidase-like antioxidant activity of diaryl diselenides: a mechanistic study

The synthesis, structure, and thiol peroxidase-like antioxidant activities of several diaryl diselenides having intramolecularly coordinating amino groups are described. The diselenides derived from enantiomerically pure R-(+)- and S-(-)-N,N-dimethyl(1-ferrocenylethyl)amine show excellent peroxidase activity. To investigate the mechanistic role of various organoselenium intermediates, a detailed in situ characterization of the intermediates has been carried out by (77)Se NMR spectroscopy. While most of the diselenides exert their peroxidase activity via selenol, selenenic acid, and selenenyl sulfide intermediates, the differences in the relative activities of the diselenides are due to the varying degree of intramolecular Se.N interaction. The diselenides having strong Se.N interactions are found to be inactive due to the ability of their selenenyl sulfide derivatives to enhance the reverse GPx cycle (RSeSR + H(2)O(2) = RSeOH). In these cases, the nucleophilic attack of thiol takes place preferentially at selenium rather than sulfur and this reduces the formation of selenol by terminating the forward reaction. On the other hand, the diselenides having weak Se.N interactions are found to be more active due to the fast reaction of the selenenyl sulfide derivatives with thiol to produce diphenyl disulfide and the expected selenol (RSeSR + PhSH = PhSSPh + RSeH). The unsubstituted diaryl diselenides are found to be less active due to the slow reactions of these diselenides with thiol and hydrogen peroxide and also due to the instability of the intermediates. The catalytic cycles of 18 and 19 strongly resemble the mechanism by which the natural enzyme, glutathione peroxidase, catalyzes the reduction of hydroperoxides.

Evaluation of techniques of single continuous suturing in penetrating keratoplasty

AIM

To evaluate the three techniques of single continuous suturing-namely, torque, antitorque, and no torque in penetrating keratoplasty.

METHODS

53 eyes of 53 patients underwent penetrating keratoplasty using torque (17 patients), antitorque (18 patients), and no torque (18 patients) suturing techniques in this prospective study. Patients were followed up at 4 weeks, 3 months, and 6 months. Keratometric, videokeratographic, refractive astigmatism, and best corrected visual acuity were determined in all the three groups at each follow up visit. Post-keratoplasty suture adjustment was done at 4 weeks, if the astigmatism was >3 dioptres.

RESULTS

The initial astigmatism in the torque group was higher than in the other two groups, although it was not statistically significant. Following suture adjustment, there was a significant decrease in astigmatism in all the three groups (p<0.0001). However, no significant difference in the postoperative astigmatism at 3 months and at 6 months was seen among the three groups.

CONCLUSIONS

The three techniques of single continuous suturing-that is, torque, antitorque, and no torque produce a similar final astigmatic results. Suture adjustment is an effective method of reducing post-penetrating keratoplasty astigmatism.

Outcome of extracapsular cataract surgery plus posterior chamber intraocular lens insertion for age-related cataract in eastern Nepal

As age-related cataract is the leading cause of blindness in Nepal, much more attention should be given to improving surgical outcomes. The aim of our study was to determine the effectiveness and risks of extracapsular cataract surgery (ECCE) for age-related cataract in a tertiary hospital of eastern Nepal. ECCE with posterior chamber intraocular lens (PC IOL) insertion on 797 eyes (754 patients) revealed improved visual acuity in 97.9%. In 595 (74.6%) the best corrected visual acuity was 6/18 or better, and 167 (20.9%) had 6/24 to 6/60 with negligible operative/postoperative complications. Thus it is concluded that ECCE with PC IOL could be performed safely and effectively even in developing countries where people are unaware that surgery is available and of the good surgical outcome.

Therapy of acanthamoeba keratitis--an experimental study

The study was conducted to determine the efficacy of various drugs/agents in the treatment of experimentally induced Acanthamoeba Keratitis (A. keratitis). Thirty rabbits were divided into 5 equal treatment groups and polyhexamethylene biguanide (PHMB) 0.02%, fluconazole 0.2%, povidone iodine 5%, aprotinin 40 IU/ml and normal saline were administered in a double blind manner, at a dose of one drop, 5 times/day. Neomycin 1700 U/ml was used as a common drug in all groups, with same frequency. Post therapy subsidence of lid oedema, mucopurulent discharge, conjunctival congestion, corneal epithelial defect and anterior chamber reactions were noted. Average healing time in days (Mean +/- S.D.) were 13.67 +/- 1.21, 22 +/- 1.41, 23.5 +/- 1.05, 17.0 +/- 1.41 and 28.0 +/- 1.90 for PHMB, fluconazole, povidone iodine, aprotinin and normal saline respectively. Lid oedema, mucopurulent discharge and conjunctival congestion improved faster in PHMB and aprotinin treated eyes. The results of this study suggest that PHMB is a better drug for A. keratitis, while aprotinin may be used as an adjuvant drug in the management of A. keratitis.

Endothelial dysfunction does not require loss of endothelial nitric oxide synthase

Whereas altered nitric oxide (NO.) formation from endothelial nitric oxide synthase (NOS) causes impaired vascular reactivity in a number of cardiovascular diseases, questions remain regarding how endothelial injury results in impaired NO. formation. It is unknown if loss of NOS expression or activity is required or if other factors are involved. Detergent treatment has been used to induce endothelial dysfunction. Therefore, NOS and NO. synthesis were characterized in a rat heart model of endothelial injury and dysfunction induced by the detergent Triton X-100. Cardiac NO. formation was directly measured by electron paramagnetic resonance spectroscopy. NOS activity was determined by the L-[(14)C]arginine conversion assay. Western blots and immunohistology were applied to define the amounts of NOS present in heart tissue before and after Triton treatment. Immunoelectron microscopy was performed to assess intracellular NOS distribution. A short bolus of Triton X-100, 0.25%, abolished responses to histamine and calcium ionophore while preserving response to nitroprusside. Complete blockade of NO. generation occurred after Triton treatment, but NOS activity assayed with addition of exogenous substrate and cofactors was unchanged, and identical 135-kDa NOS bands were seen on Western blots, indicating that NOS was not removed from the heart or structurally damaged by Triton. Immunohistochemistry showed no change in NOS localization after Triton treatment, and immunoelectron microscopy revealed similar NOS distribution in the plasma membrane and intracellular membranes. These results demonstrate that the endothelial dysfunction was due to decreased NO. synthesis but was not caused by loss or denaturation of NOS. Thus endothelial dysfunction due to mild endothelial membrane injury may occur in the presence of active NOS and is triggered by loss of NOS substrates or cofactors.

Massive corneal and conjunctival squamous cell carcinoma

A patient with massive, protuberant squamous cell carcinoma of conjunctiva invading the whole cornea, so as to hang from the surface, was referred with a visual acuity of hand motion near to face. A microscopically-controlled, frozen section guided excision, followed by double-freeze-thaw cryoapplication to the sclera and the edges of the conjunctival bed and lamello-lamellar sclerokeratoplasty, was performed. Three years later the patient's visual acuity was 20/60 with no evidence of recurrence of the lesion. Frozen section guided excision with adjuvant cryotherapy and lamellar sclerokeratoplasty is a viable therapy for massive squamous cell carcinoma of cornea and conjunctiva.

Intralamellar dissection techniques in lamellar keratoplasty

PURPOSE

To evaluate and compare the efficacy of the four adjunctive agents to facilitate recipient bed intralamellar dissection in cases of lamellar keratoplasty.

METHODS

Forty eyes with partial-thickness corneal opacities were recruited for this prospective, randomized clinical trial. The cases were divided into four groups per the intralamellar injection (i.e., air [group I], 2% hydroxypropyl methylcellulose [HPMC] [group II], balanced saline solution [BSS] [group III], and no adjunct [group IV] used to facilitate recipient intralamellar dissection). The intraoperative parameters evaluated were initial preparation time, dissection time, and total time. At each follow-up, visual acuity, refractive status, keratometry, and endothelial cell counts were also analyzed.

RESULTS

Initial preparation time, dissection time, and total time were significantly decreased with the use of an adjunct (p < 0.05) and were found to be least with the use of BSS. No difference in these time frames was noted between group I and group II. Corneal haze and incomplete air insufflation were seen in group I, and difficulty in injection of 2% HPMC and its incomplete spread were noted in group II. The mean spherical equivalent, astigmatism, endothelial cell counts, and visual acuity did not show any significant difference between any group.

CONCLUSION

Hydrodelamination with BSS is easy to perform and should be undertaken routinely to facilitate recipient intralamellar dissection.

Comparison of topical 0.3% ofloxacin with fortified tobramycin plus cefazolin in the treatment of bacterial keratitis

PURPOSE

Ofloxacin is a broad spectrum fluoroquinolone antibiotic with good ocular penetration. We compared ofloxacin 3% solution with a combination of fortified tobramycin sulphate and cefazolin sodium solutions in the treatment of culture-proven bacterial keratitis.

METHODS

Thirty eyes with culture-proven bacterial corneal ulcers were enrolled in a prospective randomised, controlled, double-masked study for comparison. The ofloxacin drop and saline were decanted into two identical-looking bottles to the tobramycin and cefazolin. The cases were randomly allocated into treatment with 0.3% ofloxacin solution or a combination of fortified antibiotics (1.5% tobramycin and 10% cefazolin solutions; control group) along with supportive cycloplegic, vitamins and anti-glaucoma therapy. Student's t-test was used to compare the results.

RESULTS

Staphylococcus aureus and coagulase-negative staphylococci were the two most common organisms isolated. Resolution of the ulcer was achieved in 93% and 87% of cases in the ofloxacin and control groups respectively. The mean time required for symptomatic relief was 7.8 +/- 1.54 days and for epithelial healing 15.0 +/- 3.86 days in ofloxacin group, compared with 8.33 +/- 1.54 days for symptomatic relief and 15.46 +/- 3.86 days for epithelial healing in the control group. Post-resolution best corrected visual acuity of 20/200 or better was achieved in all but one eye in both groups.

CONCLUSIONS

Ofloxacin and combined fortified tobramycin and cefazolin topical drops were comparable for treating cases of bacterial corneal ulcer. However, considering its easy availability and cost-effectiveness, monotherapy with ofloxacin is preferred over the combined fortified tobramycin and cefazolin therapy.

Risk factors for pediatric presumed microbial keratitis: a case-control study

PURPOSE

To evaluate risk factors for pediatric presumed microbial keratitis and to describe the clinical picture, microbiologic spectrum, treatment modalities, posttreatment sequelae, and visual outcome in cases of pediatric presumed microbial keratitis.

METHODS

A case-control study design was used to identify the risk factors associated with pediatric presumed microbial keratitis. Fifty cases of fresh corneal ulceration aged 12 years or younger were compared with 50 controls. The study variables included were age, gender, immunization status, nutritional status (weight for height), and socioeconomic status. The clinical presentation of the cases with corneal ulceration, microbiologic spectrum, and treatment modalities also were evaluated. All the cases were followed up for a minimum of 3 months, and the posttreatment sequelae and visual outcome were analyzed.

RESULTS

The mean (+/- standard deviation) age of children with corneal ulceration and controls was 4.8 (+/-3.8) years and 5.1 (+/-2.8) years, respectively. Incomplete immunization status (AOR [95% confidence interval (CI)], 1.34 [0.62-2.9]) and poor nutritional status [AOR (95% CI) 1.06 (0.68-1.6)] were not found to be the predictors of corneal ulceration. Lower socioeconomic status was significantly associated with the occurrence of corneal ulceration [AOR (95% CI) 1.52 (1.1-2.3)]. Corneal trauma (38%) and systemic illness (24%) were the most often associated predisposing factors. Seventy percent of the cases were culture positive. Staphylococcus (70%) species was the most frequently isolated, followed by Pseudomonas aeruginosa (10%). Fungi were isolated in five eyes. Postresolution visual acuity at 3 months could be recorded only in 31 eyes and a visual acuity of 6/18 or better was achieved in 22% of these cases.

CONCLUSION

Corneal ulceration in pediatric age group in India is associated with poverty.