Treatment of experimental methicillin-resistant Staphylococcus epidermidis endophthalmitis with intravitreal vancomycin

Clinical Profile, Antibiotic Resistance and Outcomes in Bacterial Endophthalmitis: Coagulase-Negative Staphylococcus Endophthalmitis as Compared to Other Organisms

BACKGROUND

To evaluate the clinical profile, outcomes and antibiotic resistance in bacterial endophthalmitis.

METHODS

This was a post-hoc analysis of a study conducted at a tertiary centre, where 60 consecutive cases of culture-proven bacterial endophthalmitis were included prospectively. Group 1 included coagulase-negative Staphylococcus endophthalmitis (CNSE), while group 2 included the remaining cases. Clinical features, antibiotic resistance and visual outcomes were compared. Visual acuity >3/60 at six months of follow-up was defined as a good visual outcome.

RESULTS

Group 1 had 31 cases, while group 2 had 29. Group 2 included 12 gram-positive and 17 gram-negative isolates. Among the groups, group 2 had more patients with presenting visual acuity below hand motions close to the face (25 vs. 12, p<0.001), poor visual outcomes (26 vs. 3, p<0.001) and retinal detachment (RD) (10 vs. 2, p=0.007). Pseudomonas was most commonly resistant to antibiotics, and ceftazidime (p=0.005) and cefazolin (p=0.009) resistance were higher in group 2 isolates. In group 1, five isolates were resistant to any one of the antibiotics, whereas in group 2, 13 isolates were resistant to any one of the antibiotics (p=0.024).

CONCLUSIONS

In the current study, eyes in the group of endophthalmitis caused by CNSE achieved better visual acuities at the last follow-up compared to eyes with endophthalmitis caused by other bacteria. Antibiotic resistance in isolates other than CNSE is a cause of concern.

Bacterial Burden Declines But Neutrophil Infiltration and Ocular Tissue Damage Persist in Experimental Staphylococcus epidermidis Endophthalmitis

Coagulase-negative staphylococci (CoNS), including Staphylococcus (S) epidermidis, are responsible for ~70% of all post-surgical endophthalmitis, a potentially blinding eye infection. However, the pathobiology of CoNS endophthalmitis is limited to epidemiological and clinical case studies with few experimental studies. Here, we report both in vitro and in vivo models to study the pathobiology of S. epidermidis endophthalmitis in mice. We found that S. epidermidis is rapidly cleared from mouse eyes, and a relatively higher dose (i.e., 10⁷ CFU/eye) was needed to cause endophthalmitis. Our time-course study revealed that bacterial load peaked at 24 h post-infection followed by a gradual decline up to 72 h. A similar time-dependent decrease in levels of inflammatory mediators and Toll-like receptor (TLR) expression was also observed. In contrast, neutrophil infiltration continued to increase up to 72 h coinciding with significant retinal tissue damage and loss of visual function. In vitro, S. epidermidis induced the activation of various inflammatory signaling pathways (i.e., NF-kB, ERK, and P38) and the production of both cytokines and chemokines in mouse BMDMs, human RPE, and retinal Muller glia. Altogether, we show that bacterial burden is reduced in S. epidermidis endophthalmitis, while tissue damage and visual function loss continue. Thus, our study provides new insights into the pathogenesis of CoNS endophthalmitis.

Vancomycin in infusion during vitrectomy in surgical treatment of acute postoperative and posttraumatic endophthalmitis

Background

Endophthalmitis is potentially devastating intraocular inflammation following eye trauma or surgery. We describe the visual outcomes and causative pathogens in acute bacterial postoperative and posttraumatic endophthalmitis treated with immediate pars plana vitrectomy (PPV) with Vancomycin dissolved in the infusion fluid.

Methods

Clinical records of consecutive 30 patients with postoperative endophthalmitis and 15 patients with posttraumatic endophthalmitis were evaluated. Vancomycin was administered constantly in the infusion fluid at the time of complete PPV. Cultures were prepared from anterior chamber paracentesis. The mean follow-up period was 13 months.

Results

The visual acuities were improved in 38 cases (84 %) and remained stable in seven cases (16 %). Median post-PPV visual acuity was 1.0 logMAR in a group with postoperative endophthalmitis and 1.3 logMAR in a group with posttraumatic endophthalmitis (p < 0.05). Twenty cases (44 %) were culture-positive (Staphylococcus, Streptococcus, Enterococcus and Bacillus spp).

Conclusions

Early PPV with Vanomycin in infusion leads to vision improvement in patients with both posttraumatic and postoperative endophthalmitis. In our series of 45 cases culture was positive only in half of the cases.

Intraocular penetration of systemic antibiotics in eyes with penetrating ocular injury

PURPOSE

To determine whether penetrating scleral or corneal injury can enhance intraocular penetration of systemic moxifloxacin, vancomycin, and ceftazidime.

METHODS

Thirty rabbits were divided into 3 groups for each antibiotic and then further subdivided to receive either scleral or corneal injury to the right eye. The left eye served as a control. Intravenous antibiotics were given following injury, and eyes were subsequently enucleated. Vitreous antibiotic concentration was determined by high-performance liquid chromatography analysis. Plasma concentration was measured for comparison.

RESULTS

Intravitreal moxifloxacin concentration was unchanged by injury. Minimum inhibitory concentration (MIC90) was achieved in the vitreous against the most common gram-positive endophthalmitis-causing organisms. Intravitreal vancomycin levels were not enhanced by injury and did not reach the MIC90 for gram-positive organisms commonly causing intraocular infection. Intravitreal ceftazidime was increased in the injured eyes, 67% and 73% higher in scleral and corneal injury eyes. It reached MIC90 of many gram-negative bacteria.

CONCLUSIONS

Intravitreal antibiotic penetration of systemic antibiotics with or without penetrating ocular injury varies depending on the antibiotic. For prevention or treatment of gram-positive-bacteria-causing endophthalmitis, intravitreal vancomycin is necessary and provides the most reliable coverage. Systemic ceftazidime can be used for many gram-negative bacteria, but intravitreal injection is recommended for better coverage, especially for more-potent organisms. Systemic moxifloxacin can be considered for most gram-positive and -negative infections due to its excellent intraocular penetration and broad coverage, but the patient's previous history of its topical use and increasing resistance patterns must be considered.

Caffeic acid phenethyl ester: its protective role against certain major eye diseases

As an effective compound found mainly in the honeybee product propolis, caffeic acid phenethyl ester (CAPE) has been commonly utilized as a medicine and remedial agent, in a number of countries. Specifically, it might inhibit nuclear factor kappa B at micromolar concentrations and demonstrate antioxidant, antineoplastic, antiproliferative, cytostatic, antiviral, antibacterial, antifungal, and anti-inflammatory features. This review article summarizes the recent progress regarding the favorable effects of CAPE on a number of eye disease models, including cataract and posterior capsule opacification, corneal diseases, retina and optic nerve-related diseases, ischemia/reperfusion injury of retina, inflammation and infection-related diseases. CAPE has been found to exhibit promising efficacy, with minimal adverse effects, in animal and cell culture studies of several eye diseases.

Daptomycin versus vancomycin in a methicillin-resistant Staphylococcus aureus endophthalmitis rabbit model: bactericidal effect, safety, and ocular pharmacokinetics

Staphylococcus aureus is a frequent cause of acute endophthalmitis, and infection with this virulent bacterium is often associated with a poor visual outcome. In this study, we investigated the bactericidal efficacy and the safety of intravitreal daptomycin (DAP), a lipopeptide antibiotic with broad-spectrum activity against Gram-positive bacteria, compared with those of intravitreal vancomycin (VAN) in a methicillin-resistant S. aureus endophthalmitis rabbit model. The pharmacokinetics and pharmacodynamics of daptomycin in the infected eyes were also studied. Rabbits were randomly divided into three treatment groups (n = 8) and one untreated group (n = 4), to compare the effect of single intravitreal injections of 0.2 mg and 1 mg of daptomycin (DAP 0.2 and DAP 1 groups, respectively) with that of 1 mg of intravitreal vancomycin (VAN 1 group). Vitreal aspirates were regularly collected and grading of ocular inflammation was regularly performed until euthanasia on day 7. In the DAP 0.2 group, 62.5% of the eyes were sterilized and the mean bacterial count presented a reduction of 1 log unit. In the DAP 1 and VAN 1 groups, the infection was eradicated (100% and 87.5% of eyes sterilized, respectively), with a 4-log-unit reduction of the mean bacterial count. The bactericidal efficacy in the DAP 1 group was not inferior to that in the VAN 1 group and was superior to that of the other regimens in limiting the ocular inflammation and preserving the architecture of the ocular structures (P < 0.05). The elimination half-life (t(1/2β)) of daptomycin was independent of the administered dose (38.8 ± 16.5 h and 40.9 ± 6.7 h, respectively, for the DAP 0.2 and DAP 1 groups) and was significantly longer than the t(1/2β) of vancomycin (20.5 ± 2.0 h for the VAN 1 group) (P < 0.05). This antibiotic could therefore be considered for the treatment of intraocular infections caused by Gram-positive bacteria.

[Intravitreal injection of antibiotics in endophthalmitis]

Early diagnosis and appropriate treatment with intravitreous antibiotics are the most important factors for the successful management of endophthalmitis. The intraocular concentration of antibiotics after intravitreous injection is far greater than that achieved by any other modality. The organisms in postoperative endophthalmitis are usually Gram-positive cocci and less commonly Gram-negative bacteria. Drug combinations are necessary to cover the full range of bacteria causing endophthalmitis. Vancomycin (1 mg/0.1 ml) is considered the drug of choice for Gram-positive organisms. Controversy remains concerning the best choice against Gram-negative bacteria. Aminoglycosides (amikacin, 0.4 mg/0.1 ml) have traditionally been recommended for Gram-negative coverage. However, because of their possible role in macular toxicity, recent trends have shifted to using ceftazidime (2.25 mg/0.1 ml) in combination with vancomycin.

Retinal Toxicity of Intraocular Vancomycin and Ceftazidime in Vitrectomized Rabbit Eyes

The purpose of this study was to evaluate the retinal toxicity of vancomycin and ceftazidime combined into an infusion solution that was intraoculary given after or during vitrectomy. Forty albino rabbits were divided into 4 groups of 10 each. Vitrectomized right eyes of groups 1, 2, and 3 were given recommended doses of vancomycin and ceftazidime alone or combined, while right eyes in the fourth group were vitrectomized using an infusion solution to which was added ceftazidime and vancomycin combination. Toxicity was tested with electroretinography (ERG) and light microscopy. ERG and light microscopy did not show any toxicity signs associated with vancomycin or ceftazidime alone or with combined therapy. Vancomycin and/or ceftazidime can reliably and effectively be used combined in an infusion solution at recommended doses after and during vitrectomy. This treatment modality does not have any toxic effects to retinal structures and is an alternative method to separate injections of the two antimicrobial agents.

Effect of caffeic acid phenethyl ester on treatment of experimentally induced methicillin-res??stantStaphylococcus epidermidis endophthalmitis in a rabbit model

This study investigated the anti-inflammatory effects of caffeic acid phenethyl ester (CAPE), a natural bee-produced compound, and compared it with corticosteroids in the treatment of experimentally induced methicillin-resistant Staphylococcus epidermidis (MRSE) endophthalmitis in addition to intravitreal antibiotics. An experimental endophthalmitis model was produced in 24 New Zealand albino rabbits by unilateral intravitreal injection of 0.1 ml of 4.7 x 10(4) colony-forming units (CFU) methicillin-resistant S. epidermidis. The animals were then divided randomly into three treatment groups and a control group, group 1 (six rabbits), received only intravitreal vancomycin (1.0 mg/0.1 ml); group 2 (six rabbits), received both intravitreal vancomycin (1.0 mg/0.1 ml) and intravitreal dexamethasone (400 microg/0.1 ml) and group 3 (six rabbits), received both intravitreal vancomycin (1.0 mg/0.1 ml) and subtenon CAPE (10 mg/0.3 ml) after 24 h post-infection. No treatment was given to the control group. Treatment efficacy was assessed by clinical examination, vitreous culture and histopathology. There were no statististically significant differences between clinical scores of all groups in examinations at 24 and 48 h post-infection (p = 0.915 and p = 0.067 respectively), but in examinations at 72 h post-infection and after 7 days post-infection, although the clinical scores of treatment groups were not significantly different from each other, they were significantly lower than the control group (p < 0.05). The culture results of all groups were sterile. As a result, CAPE was found to be as effective as dexamethasone in reducing inflammation in the treatment of experimental MRSE endophthalmitis when used with antibiotics. More studies are needed to determine the optimal administration route and effective dosage of this compound.

Susceptibilities of Propionibacterium acnes ophthalmic isolates to ertapenem, meropenem, and cefepime

We investigated the in vitro susceptibilities of 23 Propionibacterium acnes ophthalmic isolates to ertapenem, meropenem, and cefepime by utilizing the Etest. The MICs ranged from 0.094 microg/ml to 0.75 microg/ml, 0.094 microg/ml to 1.5 microg/ml, and 1 microg/ml to 12 microg/ml for ertapenem, meropenem, and cefepime, respectively. Based on our excellent in vitro carbapenem susceptibility results, in vivo studies using ertapenem and meropenem in a rabbit model of P. acnes endophthalmitis are warranted.

The effectiveness of lysostaphin therapy for experimental coagulase-negative Staphylococcus endophthalmitis

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.

Treatment of Staphylococcus epidermidis endophthalmitis with intravitreal moxifloxacin in a rabbit model

Staphylococcus epidermidis is one of the most common causes of postoperative infectious endophthalmitis, which is a serious complication of ocular surgery and penetrating trauma. Moxifloxacin is a newly developed fluoroquinolone with a potent antimicrobial activity. Corticosteroids are used in endophthalmitis to suppress devastating intraocular inflammatory response. This study was designed to assess the efficacy of intravitreal moxifloxacin alone and in combination with intravitreal dexamethasone. To the best of our knowledge, there is no published report demonstrating the effect of intravitreal moxifloxacin on bacterial endophthalmitis. One eye of each rabbit (n=24) was infected by inoculation of 10(5) colony-forming units (CFU) of S. epidermidis into the vitreus cavity. Rabbits received intravitreal injection of moxifloxacin (50 microg) or a combination of moxifloxacin (50 microg) and dexamethasone (400 microg). No treatment was given to control group. Clinical and histopathological examination scores and microbiological analysis of vitreus aspirates were compared. In the treatment groups, the clinical and histopathological scores and mean CFU were significantly lower than those in the control group (p <0.05) but showed no significant difference between the treatment groups. These results suggest that intravitreal injection of moxifloxacin is effective against S. epidermidis in this experimental rabbit model. Moxifloxacin may be a promising agent in the treatment of bacterial endophthalmitis.

Intravitreal taurolidine against experimental Staphylococcus epidermidis endophthalmitis in rabbits

PURPOSE

Taurolidine is a broad spectrum, non-antibiotic antimicrobial agent, not previously tested against infectious endophthalmitis. The efficacy of intravitreal taurolidine in the treatment of experimental Staphylococcus epidermidis endophthalmitis was evaluated and compared with vancomycin in a rabbit model.

METHODS

The right eyes of 34 albino rabbits were infected with an intravitreal inoculum of S. epidermidis (10(5) colony-forming units/0.1 ml). The right eyes of four rabbits (group 7) were not infected and served as uninfected controls. 24 hours after inoculation of bacteria the animals were divided into the following treatment groups: group 1 (7 rabbits) received intravitreal taurolidine at 24 hours and group 2 (7 rabbits) received at 48 hours. Group 3 (7 rabbits) received vancomycin at 24 hours and group 4 (7 rabbits) at 48 hours. Group 5 (3 rabbits) received polyvinylpyrrolidone at 24 hours and group 6 (3 rabbits) at 48 hours. Clinical scoring was performed at 24, 48 and 72 hours. At 72 hours post inoculation, vitreous samples were collected for quantitative microbiological studies and then, the eyes were enucleated for histopathological scorings.

RESULTS

The clinical and histopathological examinations revealed significant amelioration of inflammation in eyes treated with taurolidine and vancomycin when compared with polyvinylpyrrolidone. The eyes treated with taurolidine also had significantly lower colony forming units than the eyes treated with polyvinylpyrrolidone and taurolidine rendered many eyes sterile.

CONCLUSION

Taurolidine is expected to be a potential agent for treatment of S. epidermidis endophthalmitis.

Human corneal stromal tissue concentration after consecutive doses of topically applied 3.3% vancomycin

AIMS

To evaluate vancomycin penetration into human corneal stromal tissue in patients treated with topical vancomycin eyedrops before penetrating keratoplasty (PKP).

METHODS

Twenty four patients who underwent PKP, seven patients with keratoconus (group 1) and 17 patients with corneal scar or corneal decompensation (group 2). All patients received topical application of vancomycin eyedrops (concentration: 33 mg/ml) 10, 3, 2, 1 hour, and 15 minutes before the operation. Corneal cumulative vancomycin levels were assessed by bioassay.

RESULTS

Mean vancomycin corneal stromal tissue concentration was 46.7 (SE 4.11) microg/g tissue. This value was four to 20-fold in excess of the MIC90 of vancomycin in Staphylococcus aureus (2-10 microg/ml).

CONCLUSIONS

Vancomycin reached high corneal tissue concentrations that significantly exceeded the MIC90 (2-10 microg/ml) for most key Gram positive corneal pathogens. The ratio of vancomycin stromal concentration to protein concentration was statistically higher in group 2 (non-keratoconus).

Intravitreal vancomycin and gentamicin concentrations in patients with postoperative endophthalmitis

BACKGROUND/AIMS

To study the intravitreal antibiotic concentrations and the efficacy of an intravitreal dosing regimen to treat patients with postoperative bacterial endophthalmitis. This regimen, based on pharmacokinetic/pharmacodynamic considerations, relies on a repeat antibiotic injection of a lower dose than is generally used.

METHODS

In consecutive patients with suspected postoperative endophthalmitis a vitreous biopsy for bacterial culture was taken before 0.2 mg vancomycin and 0.05 mg gentamicin were injected intravitreally. After 3 or 4 days a second biopsy was taken for bacteriological culture and to measure intravitreal vancomycin and gentamicin concentrations, followed by a repeat injection of 0.2 mg vancomycin.

RESULTS

17 patients entered the study. In 11 patients the initial bacterial culture was positive, predominantly coagulase negative staphylococci. All second vitreous biopsies were sterile. Intravitreal vancomycin levels varied between 2.6 and 18.0 microg/ml (mean 10.3 (SD 4.1) microg/ml) after 3 days and between 3.1 and 16.6 microg/ml (mean 7.5 (6.2) microg/ml) after 4 days which is well above the minimal inhibitory concentration for most micro-organisms. Concentrations of intravitreal gentamicin varied between 0.90 and 3.3 microg/ml (mean 1.6 (0.72) microg/ml) after 3 days and between 1.2 and 2.6 microg/ml (mean 1.9 (0.99) microg/ml) after 4 days.

CONCLUSION

This dosing regimen resulted both in adequate intravitreal vancomycin and gentamicin levels for over a week as well as in negative second cultures. This study also provides new information on intravitreal vancomycin and gentamicin concentration over time in patients with postoperative endophthalmitis.

Lysostaphin is effective in treating methicillin-resistant Staphylococcus aureus endophthalmitis in the rabbit

PURPOSE

To determine the effectiveness of lysostaphin treatment of experimental endophthalmitis caused by methicillin-resistant Staphylococcus aureus (MRSA).

METHODS

In one experiment, rabbits were injected in the mid-vitreous with 50 or 200 CFU of S. aureus; untreated groups and groups injected intra-vitreally at 8 or 24 hours postinfection with vehicle or lysostaphin (0.1 mg/ml) were compared in terms of CFU/ml vitreous at 24 or 48 hours postinfection. Histopathology of untreated and treated eyes was also compared. To quantify the potency of lysostaphin, additional rabbits were injected with 50 CFU of S. aureus and untreated eyes and eyes treated at 8 hours with 0.001, 0.01 or 0.05 mg/ml were compared in terms of CFU/ml vitreous at 24 hours postinfection.

RESULTS

Vitreous of untreated eyes or vehicle-treated eyes injected with 50 or 200 CFU of S. aureus contained 5-10 million CFU/ml at 24 or 48 hours postinfection. All eyes treated with lysostaphin at 8 hours postinfection had less than 1 log CFU/ml in the vitreous (P >or= 0.0001). Similarly, eyes treated with lysostaphin at 24 hours postinfection had approximately 1 log of CFU/ml at 48 hours postinfection. None of the untreated eyes were sterile and 88% or 50% of the eyes treated at 8 or 24 hours postinfection, respectively, were sterile. Eyes treated with lysostaphin at 8, but not 24, hours postinfection had less pronounced pathologic changes than the untreated eyes (P = 0.002). A significant reduction in the CFU/ml vitreous at 24 hours postinfection was obtained by treating infected eyes at 8 hours postinfection with lysostaphin at concentrations of >or=0.001 mg/ml (P <or= 0.0034).

CONCLUSIONS

Lysostaphin is effective in treating experimental endophthalmitis mediated by MRSA.

Pharmacokinetics of 0.5 mg of a single and a multiple dose of intravitreal vancomycin in infected rabbit eyes

The purpose of this study was to determine the pharmacokinetics governing distribution and elimination of 0.5 mg of intravitreal vancomycin in a single dose and in a multiple therapeutic regime in infected rabbit eyes. A total of 96 rabbits was injected with approximately 200 CFU of S. aureus intravitreally. Four days later, a single dose of 0.5 mg of vancomycin was administered to Group I (n=36). Group II (n=60) was injected with a maximum of 4 doses of 0.5 mg every 36 hr. Four animals were sacrificed at different time points in each group. Samples of vitreous, aqueous and blood were taken from each animal for analyses by HPLC. These results were evaluated using the RSTRIP program. High vancomycin concentrations were demonstrated in the vitreous of Group I, with a calculated half-life of 12 hr. In Group II, vancomycin levels were within the therapeutic range during the entire experiment. There was minimal accumulation of the drug, and the half-life did not seem to be longer with multiple doses. In conclusion, the pharmacokinetics do not change significantly when a multidose regime is used compared with a single dose. Therapeutic intravitreal concentrations of vancomycin can be achieved by using repeated doses of 0.5 mg of vancomycin.

Pharmacokinetics of intravitreal vancomycin in normal and infected rabbit eyes

The purpose of this study was to determine the pharmacokinetics governing the distribution and elimination of intravitreally injected vancomycin in normal and infected rabbit eyes. Two groups each of 36 pigmented animals were used. Group 1 served as control. In Group 2, experimental endophthalmitis was induced in the right vitreous by inoculation with Staphylococcus aureus. Once endophthalmitis developed, a vancomycin solution was injected. Four animals from each group were killed at nine time points post-injection, the vitreous and aqueous were removed, and blood samples were taken for HPLC analysis. Data analysis was performed using the RSTRIP program. The half-lives were 69 hours in normal vitreous and 14.53 hours in infected vitreous. Therapeutic drug levels were present in the vitreous 84 hours post-injection in all eyes; they were detected from 2 to 48 hours in normal aqueous but at lower levels in the infected ones. Kv and Ca/Cv ratios suggested that the primary route of elimination was across the retina and the anterior chamber in normal eyes, and via the retina in infected eyes. Results indicate that pharmacokinetic parameters change in pathological conditions, which may help establish better treatment guidelines for endophthalmitis.

Intravitreal penetration of teicoplanin

Teicoplanin is a glycopeptide antibiotic, similar to vancomycin, but safer and better tolerated. The purpose of this study was to evaluate the penetration of teicoplanin into the vitreous when administered topically and intravenously. Twenty-five patients undergoing routine vitrectomy were recruited. Twenty were given intravenous teicoplanin: five 1 h pre-operatively, five 12 h pre-operatively, five 24 h pre-operatively and five 24 h as well as 48 h pre-operatively. Five received teicoplanin drops half-hourly for the 6 h immediately preceding vitrectomy. Undiluted vitreous specimens were obtained at the beginning of each vitrectomy procedure. Teicoplanin levels were measured using a biological assay with Staphylococcus aureus as the indicator organism. Teicoplanin activity was detected in 8 of the 20 specimens from those patients receiving the intravenous antibiotic. Teicoplanin did not penetrate readily into the vitreous cavities in these eyes despite the blood-ocular barrier being compromised in some patients, although there was evidence of accumulation with time. No activity was detected in the vitreous of those patients who received topical teicoplanin.

Pharmacokinetics of sparfloxacin in the serum and vitreous humor of rabbits: physicochemical properties that regulate penetration of quinolone antimicrobials

We have used a recently described animal model to characterize the ocular pharmacokinetics of sparfloxacin in vitreous humor of uninfected albino rabbits following systemic administration and direct intraocular injection. The relationships of lipophilicity, protein binding, and molecular weight to the penetration and elimination of sparfloxacin were compared to those of ciprofloxacin, fleroxacin, and ofloxacin. To determine whether elimination was active, elimination rates following direct injection with and without probenecid or heat-killed bacteria were compared. Sparfloxacin concentrations were measured in the serum and vitreous humor by a biological assay. Protein binding and lipophilicity were determined, respectively, by ultrafiltration and oil-water partitioning. Pharmacokinetic parameters were characterized with RSTRIP, an iterative, nonlinear, weighted, least-squares-regression program. The relationship between each independent variable and mean quinolone concentration or elimination rate in the vitreous humor was determined by multiple linear regression. The mean concentration of sparfloxacin in the vitreous humor was 59.4% +/- 12.2% of that in serum. Penetration of sparfloxacin, ciprofloxacin, fleroxacin, and ofloxacin into, and elimination from, the vitreous humor correlated with lipophilicity (r2 > 0.999). The linear-regression equation describing this relationship was not improved by including the inverse of the square root of the molecular weight and/or the degree of protein binding. Elimination rates for each quinolone were decreased by the intraocular administration of probenecid. Heat-killed Staphylococcus epidermidis decreased the rate of elimination of fleroxacin. Penetration of sparfloxacin into the noninflamed vitreous humor was greater than that of any quinolone previously examined. There was an excellent correlation between lipophilicity and vitreous entry or elimination for sparfloxacin as well as ciprofloxacin, fleroxacin, and ofloxacin. There are two modes of quinolone translocation into and out of the vitreous humor: diffusion into the eye and both diffusion and carrier-mediated elimination out of the vitreous humor.

An investigation of the hospital charges related to the treatment of endophthalmitis in the Endophthalmitis Vitrectomy Study

PURPOSE

The purpose of the study is to assess the hospital charges associated with the treatment of endophthalmitis using a sample of patients from the Endophthalmitis Vitrectomy Study (EVS).

METHODS

The Endophthalmitis Vitrectomy Study was a multicenter, randomized clinical trial with a two-by-two factorial design to compare immediate pars plana vitrectomy to tap-biopsy and to compare the use of systemic antibiotics (intravenous) to no intravenous antibiotics in the management of postoperative endophthalmitis. Hospital charge data were collected retrospectively from 129 patients from the 4 clinical centers participating in this ancillary study. This represents 31% of the total Endophthalmitis Vitrectomy Study population. An analysis of variance was used to compare hospital charges across center and treatment. A charge-effectiveness analysis compared measures the effectiveness across treatment groups. The annual savings of hospital charges in the United States was estimated for a range of annual incidence rates of endophthalmitis.

RESULTS

The use of intravenous antibiotics significantly increased hospital charges. Patients undergoing vitrectomy had significantly higher hospital charges than did patients undergoing tap-biopsy. The most charge-effective treatment for patients presenting with light perception only vision was immediate vitrectomy, whereas the most charge-effective treatment for patients presenting with better vision was tap-biopsy. Factors other than treatment independently associated with hospital charges were female sex, history of diabetes, symptom of red eye, and baseline vision of light perception only.

CONCLUSIONS

Assuming the results of the Endophthalmitis Vitrectomy Study were used as a guide for the treatment of endophthalmitis, the estimated annual nationwide reduction of hospital charges would be between $7.6 million and $40.0 million.

Anterior chamber concentrations of vancomycin in the irrigating solution at the end of cataract surgery

PURPOSE

To verify that therapeutic levels of vancomycin were present in the irrigating solution at the end of cataract surgery.

SETTING

Service d'ophtalmologie, Université de Limoges, France.

METHODS

An irrigating solution that contained 20 mg/L of vancomycin was used in 15 patients having phacoemulsification. Antibiotic concentrations in the phacoemulsification handpiece and in the aqueous humor were measured at the end of surgery.

RESULTS

Passage through the phacoemulsifier did not affect antibiotic concentration. In the aqueous humor, after wound closure, the concentration constantly exceeded the minimal inhibitory concentration of the principal gram-positive bacteria responsible for human endophthalmitis.

CONCLUSION

Vancomycin added to the irrigating solution used during cataract surgery was found in effective concentrations in the anterior chamber at the end of surgery.

Spectrum and susceptibilities of microbiologic isolates in the Endophthalmitis Vitrectomy Study

PURPOSE

To determine the microbiologic spectrum and antibiotic susceptibilities of infecting organisms in postoperative endophthalmitis and to evaluate the effects of operative factors on the microbiologic spectrum.

METHODS

Patients with bacterial endophthalmitis presenting within six weeks of cataract extraction or secondary intraocular lens implantation (IOL) were evaluated. Cultures and Gram stains were performed on intraocular specimens and susceptibility tests on the isolates.

RESULTS

Confirmed microbiologic growth was demonstrated from intraocular specimens from 291 of 420 patients (69.3%). Gram-positive bacteria were isolated from 274 patients (94.2%) with confirmed growth and gram-negative bacteria from 19 (6.5%). Two hundred twenty-six of the 323 isolates obtained (70.0%) were gram-positive, coagulase-negative micrococci, 32 (9.9%) Staphylococcus aureus, 29 (9.0%) Streptococcus species, seven (2.2%) Enterococcus species, ten (3.1%) miscellaneous gram-positive species, and 19 (5.9%) gram-negative species. All gram-positive isolates tested were susceptible to vancomycin. Seventeen gram-negative isolates (89%) were susceptible to both amikacin and ceftazidime and two (11%) were resistant to both. Anterior chamber or secondary IOL implantations were associated with higher rates of infection with gram-positives other than coagulase-negative micrococci than were posterior chamber IOL implantations (P = .022) or primary cataract extractions (P = .024).

CONCLUSIONS

Gram-positive, coagulase-negative micrococci predominated in this series. Vancomycin was active against all gram-positive isolates tested. Amikacin and ceftazidime showed equivalent activity against gram-negative isolates. Secondary or anterior chamber lens implantations were associated with a possible spectrum shift toward gram-positive organisms other than the coagulase-negative micrococci.

Vancomycin levels in the vitreous cavity after intravenous administration

PURPOSE

We studied the effects of inflammation, repeated antibiotic doses, and the surgical status of the eye on penetration of vancomycin hydrochloride into the rabbit vitreous cavity after intravenous administration.

METHODS

We studied three anatomic states (phakic, aphakic, and aphakic, vitrectomy-treated eyes) subdividing each into inflamed and noninflamed groups. Intravenous vancomycin hydrochloride (15 mg/kg of body weight) was administered every 12 hours for 48 hours. Eyes were harvested for the assay of vitreous cavity antibiotic levels at various intervals from one to 49 hours. We determined concentrations and calculated mean values and S.E.M.

RESULTS

Therapeutic levels were not established in the vitreous cavity at any time period in the two phakic groups. At 25 hours, the inflamed aphakic eyes had concentrations of 5.05 +/- 1.9 micrograms/ml and the control noninflamed aphakic eyes 4.5 +/- 1.23 micrograms/ml; slight increases were found by 49 hours. Concentrations tested in the aphakic, vitrectomy-treated eyes at two, 13, 25, and 49 hours demonstrated progressive increases both in the inflamed eyes (5.4 +/- 2.4 micrograms/ml, 9.64 +/- 4.25 micrograms/ml, 9.2 +/- 3.96 micrograms/ml, 10.34 +/- 4.49 micrograms/ml) and noninflamed eyes (3.52 +/- 2.1 micrograms/ml, 5.4 +/- 1.96 micrograms/ml, 6.8 +/- 2.53 micrograms/ml, 8.7 +/- 5.44 micrograms/ml).

CONCLUSIONS

Vitreous vancomycin concentrations in aphakic and aphakic, vitrectomy-treated eyes after intravenous administration exceed the minimal inhibitory concentrations for the usual gram-positive pathogens that create endophthalmitis, suggesting a role for intravenous vancomycin in the treatment of bacterial endophthalmitis.

Minimum bactericidal concentrations of Propionibacterium acnes isolates from cases of chronic endophthalmitis

Six isolates of Propionibacterium acnes recovered from cases of chronic infectious endophthalmitis following extracapsular cataract extraction were tested for antibiotic susceptibility. All isolates were susceptible to penicillin, cefazolin, and vancomycin with a macrobroth dilution method. Minimum bactericidal concentrations testing at 72 h revealed that six of six isolates were killed by < or = 1.0 micrograms of vancomycin/ml, one of six isolates by < or = 1.0 micrograms of penicillin/ml, and zero of six isolates by < or = 1.0 micrograms cefazolin/ml.

Endophthalmitis in Auckland 1983-1991

A review was made of 58 cases of suspected endophthalmitis presenting to Auckland Public Hospital between January 1983 and July 1991 (103 months). Thirty culture positive cases were found comprising 13 early onset postoperative, six delayed onset postoperative, five bleb-associated, four post-traumatic and two endogenous cases. The most frequent organism grown in postoperative endophthalmitis was Staphylococcus epidermidis. No conclusion could be reached as to the effectiveness of early versus delayed vitrectomy. Endophthalmitis due to S. epidermidis usually had a good prognosis while streptococcal endophthalmitis had a poor prognosis. Delayed-onset postoperative endophthalmitis most often had a good prognosis while bleb-associated endophthalmitis had a uniformly poor visual outcome. Two isolates responsible for cases of delayed-onset postoperative endophthalmitis, Propionibacterium acnes and Rhodococcus species, did not grow on agar plates until the seventh day of culture. Significant bacterial resistance to cephazolin was identified with 33% of Gram-positive and 75% of Gram-negative isolates resistant. Prevention of postoperative endophthalmitis is discussed.

Methicillin-resistant Staphylococcus aureus keratitis in the rabbit: therapy with ciprofloxacin, vancomycin and cefazolin

To determine the efficacy of a fluoroquinolone antibiotic in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) keratitis, topical administration of 0.3% ciprofloxacin was compared with topical 5.0% vancomycin or 5.0% cefazolin in experimental infections in the rabbit eye. The infections were established by intrastromal injection of 100 colony forming units (CFU) of MRSA, which resulted in greater than 10(6) CFU per cornea by 12 hr postinfection. Chemotherapy (one drop every 15 min) was given from 4-9, 10-15, or 10-20 hr postinfection. Early therapy (4-9 hr postinfection) with ciprofloxacin rendered all eyes free of bacteria; ciprofloxacin was significantly more effective than vancomycin or cefazolin. When treatment was initiated 6 hr later (10-15 hr postinfection), no corneas became free of bacteria, but ciprofloxacin was again more effective than vancomycin or cefazolin. Bacterial killing by ciprofloxacin after treatment from 10-20 hr postinfection was also significantly greater than that of vancomycin. Overall, the results show that ciprofloxacin is effective in killing methicillin-resistant staphylococcus aureus, and is most effective when applied during the very early stages of infection.

Intravitreal antibiotic therapy with vancomycin and aminoglycoside: examination of the retinal toxicity of repetitive injections after vitreous and lens surgery

The combination of vancomycin and an aminoglycoside antibiotic is frequently injected into aphakic/vitrectomized eyes for the treatment of endophthalmitis. At 2 weeks after lens and vitreous removal, rabbit eyes received an injection of a combination of 1 mg vancomycin and either 400 micrograms amikacin or 100 micrograms gentamicin. Furthermore, the effects of repeating the same combination a second and third time at intervals of 48 h were examined by light and transmission electron microscopy at 7 days to 4 months after the last injection. A single injection of either combination produced no toxicity. After 2 or 3 sets of injections of either combination, 13 of 16 eyes displayed retinal toxicity manifested by macrophages in the subretinal space, disorganization of the outer segments and retinal pigment epithelium, and discontinuities in Bruch's membrane. These results indicate that whereas a single injection of these combinations is not toxic to aphakic/vitrectomized eyes, repetitive injections may result in increasing toxicity.

Effect of intravitreal dexamethasone on ocular histopathology in a rabbit model of endophthalmitis

The histologic and clinical effect of intravitreal dexamethasone was studied in a rabbit model of experimentally induced gentamicin sensitive Staphylococcal epidermidis endophthalmitis. The study compared four treatment groups: vitrectomy alone (group I), vitrectomy plus intravitreal gentamicin (group II), vitrectomy plus intravitreal gentamicin and dexamethasone (group III), and intravitreal gentamicin and dexamethasone without vitrectomy (group IV). All eyes treated with dexamethasone, with or without vitrectomy, exhibited less clinical and histologic manifestations of inflammation. This study suggests that suppression of inflammation through the use of intravitreal dexamethasone leads to preservation of ocular architecture with potentially improved retinal function and visual benefit.

Effects of intravitreal dexamethasone on concentration of intravitreal vancomycin in experimental methicillin-resistant Staphylococcus epidermidis endophthalmitis

Intravitreal corticosteroids in the treatment of bacterial endophthalmitis remain controversial. We utilized an experimental rabbit model of methicillin-resistant Staphylococcus epidermidis endophthalmitis (i) to calculate the intravitreal vancomycin concentration in rabbit eyes receiving intravitreal vancomycin alone or in combination with intravitreal dexamethasone and (ii) to determine whether an intravitreal steroid has any effect on intravitreal vancomycin levels. All right eyes were infected and all left eyes were uninfected. The rabbits were divided into two treatment groups: (i) 32 eyes (group I) were injected with intravitreal vancomycin, 1.0 mg (0.1 ml); (ii) 32 additional eyes (group II) were injected with intravitreal dexamethasone, 400 micrograms (0.1 ml), in addition to vancomycin. Measurement of intravitreal vancomycin concentration was performed following sacrifice, utilizing a microbiologic agar diffusion assay. Analyses of intravitreal vancomycin concentrations were performed by using model-independent parameters, with area under the concentration-time curves derived by trapezoidal approximation. The intravitreal vancomycin concentration was significantly lower in both uninfected and infected group II eyes (P less than 0.002). Analysis of intravitreal vancomycin concentration-time relationships was performed by using a nonlinear least-squares regression program; data best fit a one-compartment model. In addition, no vancomycin-dexamethasone interaction could be demonstrated. The reduced level of intravitreal vancomycin in the presence of intravitreal dexamethasone may have important clinical implications.

Delayed-onset pseudophakic endophthalmitis

We reviewed 19 cases of delayed-onset pseudophakic endophthalmitis in which diagnostic cultures were performed at one month or more after cataract extraction with posterior chamber intraocular lens implantation. We isolated four different organisms in these 19 cases: 12 Propionibacterium species (63%), three Candida parapsilosis (16%), three Staphylococcus epidermidis (16%), and one Corynebacterium species (5%). Because of the unusual delayed-onset features of these cases and the retrospective nature of this study, a variety of treatment regimens were used. Twelve patients had recurrence of marked inflammation despite an apparent initial cure, and ten of these patients had positive culture results on repeat examination of intraocular fluids. Nine patients continued to be treated with topical corticosteroids postoperatively to suppress low-grade inflammation. Of the 19 patients, 16 had final visual acuity of 20/400 or better. Delayed-onset pseudophakic endophthalmitis had a more favorable visual prognosis, compared to acute-onset endophthalmitis.

The treatment of postoperative endophthalmitis. Results of differing approaches to treatment

The authors treated 26 patients with postoperative endophthalmitis over a 4-year period, between 1983 and 1986. Nineteen patients were culture-positive and seven were culture-negative. All patients received intravitreal antibiotics as part of their treatment regimen. Culture-negative patients generally responded well to a single intravitreal antibiotic injection. Five of seven (71.4%) culture-positive patients who were treated with a single intravitreal antibiotic injection and no vitrectomy suffered either a recurrence of their infection or did not respond to treatment. Four of five patients who received a vitrectomy in addition to a single intravitreal antibiotic injection were cured of their infections; the one patient who received repeated intravitreal antibiotic injections alone and all six patients who received repeated intravitreal antibiotic injections in combination with vitrectomy were cured of their infections. Although the intravitreal injection of antibiotics provides an extremely high initial level of antibiotics inside the eye, a single intravitreal antibiotic injection may only partially treat bacterial endophthalmitis. In culture-negative cases, a single intravitreal injection of antibiotics appears to be sufficient treatment. In culture-positive cases, a higher cure rate is achieved with an aggressive approach which includes the use of repeated intravitreal antibiotic injections and/or vitrectomy.

Coagulase-negative staphylococcal endophthalmitis. Increase in antimicrobial resistance

The predicted sensitivities of common organisms guide initial antibiotic therapy in endophthalmitis. The authors suspected a change in the expected sensitivity of coagulase-negative staphylococci when three cases of endophthalmitis due to multiply resistant organisms failed to respond to intravitreal cefazolin and gentamicin. The authors reviewed 48 cases from 1982 to 1986, compared these with 28 cases from 1973 to 1981, they found increased resistance to gentamicin (35 versus 0%, P less than 0.05) and increased resistance to methicillin (27 versus 19%). Eight cases were resistant to both antibiotics, including the three clinical failures. Final vision was unrelated to antimicrobial resistance. Since cephalosporins may be ineffective clinically against methicillin-resistant staphylococci, concomitant gentamicin resistance may render intravitreal cefazolin and gentamicin inadequate for their treatment. No isolates were resistant to vancomycin. Vancomycin and aminoglycoside, used intravitreally in the initial management of endophthalmitis, would be anticipated to provide better coverage than cefazolin and aminoglycoside for endophthalmitis due to the staphylococci, as well as for infections due to streptococcal and bacillus species.