Bilateral methicillin-resistant staphylococcus aureus keratitis in a medical resident following an uneventful bilateral photorefractive keratectomy

Infectious Keratitis After Keratorefractive Surgery: Update and Review of the Literature

OBJECTIVES

To summarize the clinical manifestations, microbiological profile, treatment, and prognosis of corneal infections after different keratorefractive surgery.

METHODS

To obtain relevant studies, English-language databases, including PubMed, Ovid Embase, Web of Science, and CLNAHL, were searched from January 1979 to March 2022. The fundamentals of the literature, clinical characteristics, pathogens, and treatments were retrieved for each included article.

RESULTS

Eighty-four studies involving 306 infectious eyes were included in this review. Risk factors of potential infection included a history of blepharitis, contact lens usage, and contaminated surgical instruments. The mean onset time was 22.9±38.7 days (range: 1 day to 3 years). The most common organism isolated from infectious keratitis after keratorefractive surgery were Staphylococcus aureus , followed by Mycobacterium and coagulase-negative Staphylococcus . Most of the infections after refractive procedures were sensitive to medical treatment alone, and the ultimate best-corrected visual acuity after medical treatment was as follows: 20/20 or better in 82 cases (37.0%), 20/40 or better in 170 cases (76.5%), and worse than 20/40 in 52 cases (23.5%). Surgical interventions including flap lift, flap amputation, ring removal, and keratoplasty were performed in 120 eyes (44.5%).

CONCLUSIONS

Most infections after keratorefractive surgery occur within a week, whereas more than half of the cases after laser-assisted in situ keratomileusis happen after about a month. Gram-positive cocci and mycobacterium are the most common isolates. Infections after LASIK, intracorneal ring (ICR) implantation, and small incision lenticule extraction, which primarily occur between the cornea layers, require irrigation of the tunnels or pocket with antibiotics.

A Pyrrhic Victory: The PMN Response to Ocular Bacterial Infections

Some tissues of the eye are susceptible to damage due to their exposure to the outside environment and inability to regenerate. Immune privilege, although beneficial to the eye in terms of homeostasis and protection, can be harmful when breached or when an aberrant response occurs in the face of challenge. In this review, we highlight the role of the PMN (polymorphonuclear leukocyte) in different bacterial ocular infections that invade the immune privileged eye at the anterior and posterior segments: keratitis, conjunctivitis, uveitis, and endophthalmitis. Interestingly, the PMN response from the host seems to be necessary for pathogen clearance in ocular disease, but the inflammatory response can also be detrimental to vision retention. This "Pyrrhic Victory" scenario is explored in each type of ocular infection, with details on PMN recruitment and response at the site of ocular infection. In addition, we emphasize the differences in PMN responses between each ocular disease and its most common corresponding bacterial pathogen. The in vitro and animal models used to identify PMN responses, such as recruitment, phagocytosis, degranulation, and NETosis, are also outlined in each ocular infection. This detailed study of the ocular acute immune response to infection could provide novel therapeutic strategies for blinding diseases, provide more general information on ocular PMN responses, and reveal areas of bacterial ocular infection research that lack PMN response studies.

The trend of resistance to antibiotics for ocular infection of Staphylococcus aureus, coagulase-negative staphylococci, and Corynebacterium compared with 10-years previous: A retrospective observational study

OBJECTIVE

To retrospectively identify epidemiological trends of infection on the ocular surface and investigate trends of resistance to bacterial antibiotics compared with 10-years previous for Staphylococcus aureus, coagulase-negative staphylococci (CNS), and Corynebacterium in Japan.

MATERIALS AND METHODS

Bacterial isolate samples were collected from the conjunctival sacs of eyes afflicted with conjunctivitis, keratitis, dacryocystitis, and hordeolum from September 2004 through November 2005 (n = 145 isolates) and September 2014 through November 2015 (n = 195 isolates) at the Baptist Eye Institute, Kyoto, Japan. The prevalence of methicillin-resistant S. aureus (MRSA), methicillin-resistant CNS (MR-CNS), and fluoroquinolone-resistant Corynebacterium were examined, and susceptibility of isolated bacteria to levofloxacin (LVFX), cefmenoxime (CMX), chloramphenicol (CP), erythromycin (EM), vancomycin (VCM), and arbekacin (ABK) were compared between both time periods using the disc susceptibility method.

RESULTS

Over the 10-year period from initial to final examination, the prevalence of MRSA and MR-CNS significantly decreased from 52% to 22% (P < 0.05) and from 47% to 25% (P < 0.05), respectively, yet there was no change in the prevalence of fluoroquinolone-resistant Corynebacterium (60% and 54%; P = 0.38). Antibiotic-resistance trend analysis revealed that susceptibility to antibiotics in 2014-2015 was similar to that in 2004-2005. MRSA and MR-CNS were susceptible to CP (88%), VCM (100%), and ABK (100%), while fluoroquinolone-resistant Corynebacterium was susceptible to CMX (100%), VCM (100%), and ABK (96%).

CONCLUSION

The prevalence of MRSA and MR-CNS significantly decreased between the two time periods, yet more than 50% of the Corynebacterium isolates were still resistant to LVFX. Although no increase in bacterial resistance to antibiotics was found, a cautionary use of fluoroquinolone eye drops should be considered.

Nasal and conjunctival screening prior to refractive surgery: an observational and cross-sectional study

OBJECTIVES

To investigate bacterial flora of clinically healthy conjunctiva and nasal cavity among patients prior to refractive surgery, as well as the characteristics of patients with methicillin-resistant Staphylococcus aureus (MRSA) colonisation.

DESIGN

Observational and cross-sectional study.

SETTING

A single-centre study in Japan.

PARTICIPANTS

120 consecutive patients pre-refractive surgery.

PRIMARY AND SECONDARY OUTCOME MEASURES METHODS

Samples were obtained from the right conjunctival sac and the nasal cavity of 120 consecutive patients prior to refractive surgery and were then measured for the levels of the minimum inhibitory concentration (MIC) of antibiotics. Patients were interviewed regarding their occupation, family living situation and any personal history of atopic dermatitis, asthma, smoking or contact lens wear.

RESULTS

Propionibacterium acnes (P. acnes) (32.5%) and Staphylococcus epidermidis (4.2%) were detected from the conjunctival sac. S. epidermidis was the most commonly isolated (68.3%) in the nasal cavity. Of the 30 patients (25.0%) with colonisation by S. aureus, 2 patients, both of whom were healthcare workers with atopic dermatitis, were found to be positive for MRSA in the nasal cavity. A history of contact lens wear, asthma or smoking, as well as patient gender and age, was not associated with MRSA colonisation.

CONCLUSIONS

There were only 2 patients who were colonised with MRSA, both of whom were healthcare workers with atopic dermatitis. P. acnes was predominantly found in the conjunctival sac. Further study is needed to investigate the involvement between nasal and conjunctival flora, and risk factors for infectious complications.

Current knowledge about and recommendations for ocular methicillin-resistant Staphylococcus aureus

Staphylococcus aureus is the most important and common pathogen that infects patients following cataract surgery, laser in situ keratomileusis, and photorefractive keratectomy. It is reported to be the second most common pathogen causing bacterial keratitis around the world. Of special concern are increasing reports of postoperative methicillin-resistant S aureus (MRSA) infection. For example, MRSA wound infections have been reported with clear corneal phacoemulsification wounds, penetrating keratoplasty, lamellar keratoplasty, and following ex vivo epithelial transplantation associated with amniotic membrane grafts. These and other data suggest that MRSA has become increasingly prevalent worldwide. In this article, we review the current medical literature and describe the current challenge of ocular MRSA infections. Recommendations are made based on an evidence-based review to identify, treat, and possibly reduce the overall problem of this organism.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Pharmacological treatment for infectious corneal ulcers

INTRODUCTION

Cornea ulceration and infectious keratitis are leading causes of corneal morbidity and blindness. Infectious causes are among the most frequent and most severe. Management strategies for bacterial corneal ulcers have changed significantly over the last decades, however with a more limited progress in the treatment and management of nonbacterial, infectious ulcers.

AREAS COVERED

This paper provides an overview of the current principles, strategies and treatment choices for infectious corneal ulcers in adults.

EXPERT OPINION

Topical application with a broad-spectrum antimicrobial remains the preferred method for the pharmacological management of infectious corneal ulcers. Increasing reports of clinical failures and in vitro resistance to antibiotics to treat the most common infectious (bacterial) corneal ulcers are increasing concerns. New approaches for improvement in the pharmacological management of corneal ulcers should focus on strategies for a more rational and evidence-based use of current antimicrobials and development of products to modulate the host immune response and to neutralize microbial toxins and other immune modulators.

Ocular microbiology trends in Edmonton, Alberta: a 10-year review

OBJECTIVE

Methicillin-resistant Staphylococcus aureus (MRSA) has been recognized as an increasingly common cause of nosocomial infections since the 1980s.(1) Reports of ocular infections due to MRSA are composed primarily of case reports. But a recent report from the United States suggests that ocular infections due to MRSA are about to become more common than methicillin-sensitive S. aureus (MSSA).(2) However, this observation is not consistent with anecdotal experience at the University of Alberta. The purpose of this study is to evaluate the ocular microbiology trends in a tertiary care eye center in Canada.

METHODS

Cross-sectional study using a computer search of the DynaLIFE(DX) Diagnostic Laboratory Services database for all positive ocular microbiology cultures and in vitro antibiotic susceptibilities performed in the Edmonton area.

RESULTS

Over a 10-year period, between 2000 and 2010, 6.4% of S. aureus isolates were MRSA; there were 2030 MSSA and 129 MRSA isolates, including 46 MSSA and 4 MRSA isolates from deep eye cultures. The prevalence of MRSA over the total number of S. aureus isolates, regardless of specimen source, steadily increased in the 10-year period, from 0.5% in 2002 to 12.6% in 2010. Gram-positive cocci were the most common organisms to cause ocular infections (82.6%). In vitro susceptibility of ocular MSSA and MRSA samples demonstrated 100% sensitivity to vancomycin.

CONCLUSIONS

The prevalence of MRSA ocular infections, although still uncommon, appears to be increasing in Edmonton, Alberta.

Bilateral methicillin-resistant Staphylococcus aureus keratitis following hyperopic photorefractive surgery

To report clinical manifestations of a female patient with bilateral bacterial keratitis following photorefractive keratectomy (PRK). Bilateral PRK was performed for moderate hyperopia. Bandage contact lenses were fitted at the conclusion of the surgery. Bilateral infectious keratitis with hypopion was diagnosed within 4 days after surgery. Smear and culture were obtained and showed the presence of methicillin-resistant Staphylococcus aureus (MRSA). The patient was treated with systemic prednisone and topical antibiotics (vancomycin, tobramycin and netylmicin) and betamethasone. After 1 month corneal leukoma was still present and remained unchanged during the following 7 months. Infectious keratitis is a rare complication of PRK that appears early in the postoperative period. MRSA keratitis may determine long-term visual impairment despite prompt therapeutic intervention.

Microbial keratitis after corneal laser refractive surgery

Corneal laser refractive surgery is increasingly being performed on patients with the aim of improving unaided vision. Most candidates for surgery have excellent spectacle- or contact lens-corrected vision. Although microbial keratitis following refractive surgery is a rare complication, and usually has a good visual outcome, it can be sight-threatening. The spectrum of pathogens differs to other causes of microbial keratitis, such as contact lens-associated keratitis, and a different management approach is required. Postoperatively, patients are prescribed topical steroids and broad-spectrum topical antibiotics, typically fluoroquinolones. These do not cover unusual organisms, such as fungi, Nocardia, Acanthamoeba and some atypical mycobacteria. In post-laser-assisted in situ keratomileusis microbial keratitis, the lamellar flap should be lifted to acquire samples for specific microbiological examination, including these atypical organisms. Confocal microscopy is a noninvasive test that provides morphological information, and is operator dependent, but may assist in the rapid diagnosis of fungal, Acanthamoeba or Norcardia keratitis. PCR is not in widespread use, but has high sensitivity and specificity, and may facilitate early diagnosis and specific treatment of the causative organism, which is critical in obtaining the best clinical outcome.

Review of moxifloxacin hydrochloride ophthalmic solution in the treatment of bacterial eye infections

Moxifloxacin hydrochloride ophthalmic solution 0.5% (Vigamox((R))) is the ocular formulation/adaptation of moxifloxacin. Moxifloxacin is a broad spectrum 8-methoxyfluoroquinolone which terminates bacterial growth by binding to DNA gyrase (topoisomerase II) and topoisomerase IV, essential bacterial enzymes involved in the replication, translation, repair and recombination of deoxyribonucleic acid. Affinity for both enzymes improves potency and reduces the probability of selecting resistant bacterial subpopulations. Vigamox is a bactericidal, concentration dependent, anti-infective. It is preservative free, and well tolerated with minimal ocular side effects. It provides increased penetration into ocular tissues and fluids with improved activity against Streptococci and Staphylococci species and moderate to excellent activity against clinically relevant, gram-negative ocular pathogens.

Surface ablation techniques

The ongoing quest for a safe, simple, effective, minimally invasive, and stable refractive surgical procedure to correct refractive errors has stimulated the development of surface ablation techniques and laser in situ keratomileusis. In this review, we describe the history, patient assessment, techniques, outcomes, and complications of surface ablation (photorefractive keratectomy, laser-assisted sub-epithelial keratectomy, epithelial laser-assisted in situ keratomileusis) and compare the results of various surface techniques. Surface ablation procedures will continue to evolve, with potential improvements in outcomes accompanying future sophisticated ablation profiles and laser technology.

In vitro susceptibility patterns of methicillin-resistant Staphylococcus aureus and coagulase-negative Staphylococcus corneal isolates to antibiotics

PURPOSE

To determine the in vitro susceptibility of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative Staphylococcus (MRCNS) isolates to various antibiotics.

METHODS

All cases of bacterial keratitis caused by Staphylococcus species during 2006 and 2007 were identified. The isolates were divided according to species and susceptibility to methicillin into 4 groups: methicillin-susceptible S. aureus, methicillin-susceptible coagulase-negative Staphylococcus, MRSA, and MRCNS. Routine susceptibility testing for Staphylococcus species to methicillin and 19 other antibiotics was performed using the MicroScan POS Breakpoint Combo Panel Type 20.

RESULTS

One hundred fifty-seven isolates were identified. Forty isolates were S. aureus, including 21 MRSA, and 117 isolates were coagulase-negative Staphylococcus, including 29 MRCNS. All MRSA isolates were susceptible to gentamicin, linezolid, rifampin, tetracycline, and vancomycin and were resistant to penicillin, cefazolin, cefepime, azithromycin, erythromycin, and ofloxacin. Ninety percent of MRSA isolates were resistant to fourth-generation fluoroquinolones. All MRCNS isolates were susceptible to vancomycin, chloramphenicol, linezolid, and rifampin and were resistant to penicillin, cefazolin, cefepime, and azithromycin. Sixty-five percent of the MRCNS isolates were susceptible to fourth-generation fluoroquinolones and gentamicin.

CONCLUSIONS

All MRSA and MRCNS isolates were sensitive to vancomycin, linezolid, and rifampin. MRSA isolates were generally sensitive to gentamicin and tetracycline and resistant to fourth-generation fluoroquinolones. MRCNS isolates were not consistently sensitive to gentamicin, tetracycline, or fourth-generation fluoroquinolones.

[Multiresistant bacteria in ophthalmology]

Multidrug-resistant bacteria have emerged as an increasing threat in many areas of medicine. The most prominent multidrug-resistant pathogens are methicillin-resistant S. aureus (MRSA), vancomycin-resistant MRSA (VMRSA), vancomycin-resistant enterococci (VRE), and Enterobacteriaceae with extended-spectrum beta-lactamase (ESBL). In particular, MRSA and VRE cause infections seen in ophthalmology. The lids, lacrimal duct, and ocular surface are frequently involved.

Increasing prevalence of methicillin resistance in serious ocular infections caused by Staphylococcus aureus in the United States: 2000 to 2005

PURPOSE

To report the nationwide prevalence of methicillin resistance in serious ocular infections involving Staphylococcus aureus and profile in vitro antimicrobial susceptibility of S aureus from ocular isolates over time.

SETTING

Mount Sinai School of Medicine, New York, New York, USA.

METHODS

Data on S aureus submitted to The Surveillance Network (TSN) by more than 200 laboratories in the United States from January 2000 to December 2005 were reviewed. The prevalence of methicillin resistance in S aureus ocular infections and in vitro susceptibility to antibiotic agents commonly used to treat or prevent ocular infections were determined.

RESULTS

The proportion of S aureus infections culture-positive for methicillin-resistant S aureus (MRSA) increased from 29.5% in 2000 to 41.6% in 2005. The MRSA ocular isolates were multidrug resistant; that is, in vitro resistance to 3 antibiotic agents or more, including all fluoroquinolones tested.

CONCLUSIONS

Multidrug-resistant MRSA is increasing in serious ocular infections. Based on the rate of increase in the TSN database, MRSA cultures from serious ocular infections could be more common than methicillin-susceptible S aureus within 2 to 3 years. Large-scale national surveillance programs are needed to monitor in vitro antimicrobial resistance trends in ocular isolates.

Methicillin-resistant Staphylococcus aureus infectious keratitis following refractive surgery

PURPOSE

To elucidate risk factors, clinical course, visual outcomes, and treatment of culture-proven methicillin-resistant Staphylococcus aureus (MRSA) infectious keratitis following refractive surgery.

DESIGN

Interventional case series.

METHODS

Multicenter chart review of 13 cases of MRSA keratitis following refractive surgery and literature review.

RESULTS

Thirteen eyes of 12 patients, nine of whom were either healthcare workers or exposed to a hospital surgical setting, developed MRSA keratitis following refractive surgery. All patients presented with a decrease in visual acuity and complaints of pain or irritation in the affected eye. Common signs on slit-lamp biomicroscopy were corneal epithelial defects, focal infiltrates with surrounding edema, conjunctival injection, purulent discharge, and hypopyon. All patients were diagnosed with infectious keratitis on presentation and treated with two antibiotics. All eyes were culture-positive for MRSA.

CONCLUSIONS

According to a computerized MEDLINE literature search, this is the first case series of MRSA infectious keratitis following refractive surgery, the first reports of MRSA keratitis after refractive surgery in patients with no known exposure to a healthcare facility, the first report of MRSA keratitis after a laser in situ keratomileusis (LASIK) enhancement, and the first reports of MRSA keratitis after prophylaxis with fourth-generation fluoroquinolones. MRSA keratitis is a serious and increasing complication following refractive surgery. Patients with exposure to a healthcare environment should be considered at additional risk for developing MRSA keratitis. However, in addition, surgeons should now be vigilant for community-acquired MRSA. Prompt identification with culturing and appropriate treatment of MRSA keratitis after refractive surgery is important to improve visual rehabilitation.

Bilateral methicillin-resistant Staphylococcus aureus keratitis after photorefractive keratectomy

A 52-year-old woman with a history of liver transplantation developed bilateral corneal infiltrates 1 week after uneventful photorefractive keratectomy (PRK). Cultures grew methicillin-resistant Staphylococcus aureus (MRSA), resistant to fluoroquinolone antibiotics. The infections responded to topical vancomycin and resolved bilaterally over 3 weeks. Three months postoperatively, the uncorrected visual acuity (UCVA) was 20/20 in the right eye and 20/25 in the left eye; the best spectacle-corrected visual acuity (BSCVA) was 20/20 in both eyes. During the course of treatment, the patient reported chronic intermittent prophylactic use of oral ciprofloxacin. While fluoroquinolones typically provide excellent postoperative coverage, Staphylococcus organisms have a growing antibiotic resistance to fluoroquinolones, and MRSA may become a more prevalent organism in corneal infections. Chronic subtherapeutic fluoroquinolone use can increase the mutational resistance of Staphylococcus to fluoroquinolone and methicillin. The patient's frequent hospital visits placed her at high risk for MRSA colonization. This case represents the fifth reported case of MRSA keratitis after PRK.

In vitro activity of fluoroquinolones, vancomycin, and gentamicin against methicillin-resistant Staphylococcus aureus ocular isolates

PURPOSE

To determine the antibacterial activity of fluoroquinolones, vancomycin, and gentamicin against methicillin-resistant Staphylococcus aureus (MRSA) ocular surface isolates.

DESIGN

Retrospective review.

METHODS

MRSA isolates were obtained from 21 patients. The MIC(50) (mean inhibitory concentration)(microg/ml) values of 31 MRSA ocular surface isolates were determined for gatifloxacin, moxifloxacin, ciprofloxacin, ofloxacin, vancomycin, and gentamicin using the Etest (AB Biodisk, Solna, Sweden) or the VITEK system (bioMérieux, Inc, Durham, North Carolina, USA). Susceptibility data were interpreted based on criteria specified by the Clinical and Laboratory Standards Institute (CLSI).

MAIN OUTCOME MEASURES

MIC(50) values in microg/ml and interpretation of susceptibility or resistance.

RESULTS

In vitro resistance rates and median MIC(50) in microg/ml for the MRSA isolates were: gatifloxacin (71%, 8.0), moxifloxacin (68%, 8.0), ciprofloxacin (94%, 8.0), ofloxacin (94%, 8.0), vancomycin (0%, 1.0), and gentamicin (3%, 0.5).

CONCLUSIONS

MRSA ocular isolates exhibited a relatively high rate of in vitro resistance to all fluoroquinolones tested, including the fourth generation. In contrast, MRSA isolates were found to be highly sensitive to vancomycin and gentamicin.

Staphylococcus aureus-induced corneal inflammation is dependent on Toll-like receptor 2 and myeloid differentiation factor 88

Toll-like receptors (TLRs) expressed by the corneal epithelium represent a first line of host defense to microbial keratitis. The current study examined the role of TLR2, TLR4, and TLR9 and the common adaptor molecule myeloid differentiation factor 88 (MyD88) in a Staphylococcus aureus model of corneal inflammation. The corneal epithelia of C57BL/6, TLR2(-/-), TLR4(-/-), TLR9(-/-), and MyD88(-/-) mice were abraded using a trephine and epithelial brush and were exposed to heat- or UV-inactivated S. aureus clinical strain 8325-4 and other clinical isolates. Corneal thickness and haze were measured by in vivo confocal microscopy, neutrophil recruitment to the corneal stroma was quantified by immunohistochemistry, and cytokine production was measured by enzyme-linked immunosorbent assay. The exposure of corneal epithelium to S. aureus induced neutrophil recruitment to the corneal stroma and increased corneal thickness and haze in control C57BL/6 mice but not in TLR2(-/-) or MyD88(-/-) mice. The responses of TLR4(-/-) and TLR9(-/-) mice were similar to those of C57BL/6 mice. S. aureus-induced cytokine production by corneal epithelial cells and neutrophils was also significantly reduced in TLR2(-/-) mice compared with that in C57BL/6 mice. These findings indicate that S. aureus-induced corneal inflammation is mediated by TLR2 and MyD88 in resident epithelial cells and infiltrating neutrophils.

Ophthalmic Manifestations of Infections Caused by the USA300 Clone of Community-Associated Methicillin-Resistant Staphylococcus aureus

PURPOSE

To report the microbiological, clinical, and pathological characteristics of community-associated methicillin-resistant Staphylococcus aureus (CAMRSA) infections of the eye and orbit.

DESIGN

Prospective case series.

PARTICIPANTS

Nine patients with CAMRSA infections of the eye and orbit were identified during a 6-month period at 2 tertiary care hospitals in San Francisco.

METHODS

Case identification was by prospective case selection and retrospective laboratory review of 549 MRSA cultures collected in the 2 hospitals. Ophthalmic microbial isolates were analyzed by pulsed-field gel electrophoresis and compared with a control CAMRSA clone (USA300). Clinical characteristics of patients infected with CAMRSA were reviewed, and all surgical specimens underwent pathological examination.

MAIN OUTCOME MEASURES

Pulsed-field gel electrophoresis banding patterns of MRSA isolates, antibiotic sensitivity profiles, patient demographics, systemic and ocular complications of infection, and posttreatment visual acuities.

RESULTS

Nine ophthalmic isolates were CAMRSA clone USA300. The infections included orbital cellulitis, endogenous endophthalmitis, panophthalmitis, lid abscesses, and septic venous thrombosis. Patients were treated with trimethoprim-sulfamethoxazole, rifampin, clindamycin, or vancomycin based on microbial sensitivity studies and severity of infection. Eight of the 9 patients had no history of hospitalization. Seven patients required hospitalization, 3 required surgery, and an additional 4 required invasive procedures. Eight patients had good visual outcomes, but 1 deteriorated to no light perception. Pathological analyses showed extensive necrosis in eyelid and orbital specimens, and disorganized atrophy bulbi in an enucleated eye.

CONCLUSION

The USA300 CAMRSA clone, which carries Panton-Valentine leukocidin genes, can cause aggressive infections of the eye and orbit in hospital-naive patients. Treatment of infections often required debridement of necrotic tissues in addition to non-beta-lactam class antibiotics. In communities where CAMRSA is prevalent, ophthalmologists should obtain microbial cultures and sensitivity studies to help guide antibiotic therapy for severe ophthalmic infections.

Fourth-generation fluoroquinolone-resistant bacterial keratitis after refractive surgery

We report the first 2 cases of bacterial keratitis resistant to fourth-generation fluoroquinolones after laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK). The first patient had Pseudomonas aeruginosa keratitis after PRK despite treatment with moxifloxacin. The second patient was on gatifloxacin post-LASIK when she had methicillin-resistant Staphylococcus aureus (MRSA) keratitis diagnosed. In both cases, culture susceptibilities showed isolates resistant to moxifloxacin and gatifloxacin, and treatment with topical aminoglycosides and surgical intervention was necessary to effect a cure. These cases show the potential limitations in the coverage of these antibiotics.

Treatment of rabbit corneal infections with ophthalmic gatifloxacin: a concentration dependence study

This study was designed to determine the most effective dose of gatifloxacin in ophthalmic solution for control of methicillin-resistant Staphylococcus aureus (MRSA) corneal infections in rabbits. Rabbits were inoculated by injecting 9300 colony-forming units of MRSA into the corneal stroma of the eye (n=43). They were then randomly assigned to topical administration of saline, ofloxacin 0.3%, or gatifloxacin 0.02%, 0.1%, 0.3%, or 0.5% ophthalmic solutions. Infection severity 48 hours postinoculation was assessed by masked observers using standard scales. After treatment completion, viable MRSA in corneal tissue were counted, and pathologic examinations of ocular tissues were conducted. Relative to saline, treatment with gatifloxacin 0.3% or 0.5% decreased mean infection scores at every time point from 16 to 48 hours after inoculation (P < or = .012) and reduced area-under-the-curve values for infection scores by 50.3% and 54.2%, respectively (P = .00005). Rabbits treated with gatifloxacin 0.3% and 0.5% had lower area-under-the-curve values than those treated with ofloxacin 0.3% (P < or = .039). Viable MRSA in corneal tissue after gatifloxacin 0.3% or 0.5% treatment were decreased to less than 1% of those found after ofloxacin 0.3% treatment. Gram-positive colony formation and abscesses found in saline-treated corneas were distinctly alleviated by treatment with gatifloxacin 0.3% or 0.5%. No significant differences were observed between treatments with gatifloxacin 0.3% or 0.5% ophthalmic formulations and they were equally effective. Topical administration of gatifloxacin 0.3% or 0.5% ophthalmic solutions controlled MRSA corneal infections in rabbits significantly better than saline or ofloxacin 0.3%.