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Table 1. 
Cultures of Corneal Scrapings and Contact Lenses Among 49 Patients With Contact Lens–Related Microbial Keratitisa
Cultures of Corneal Scrapings and Contact Lenses Among 49 Patients With Contact Lens–Related Microbial Keratitisa
Table 2. 
Culture Results From Corneal Scrapings and Contact Lenses
Culture Results From Corneal Scrapings and Contact Lenses
1.
Wong  TYNg  TPFong  KSTan  DT Risk factors and clinical outcomes between fungal and bacterial keratitis: a comparative study. CLAO J 1997;23 (4) 275- 281
PubMed
2.
Dart  JK Predisposing factors in microbial keratitis: the significance of contact lens wear. Br J Ophthalmol 1988;72 (12) 926- 930
PubMedArticle
3.
Ruben  M Acute eye disease secondary to contact lens wear. Lancet 1976;1 (7951) 138- 140
PubMedArticle
4.
Cooper  RLConstable  I Infective keratitis in soft contact lens wearers. Br J Ophthalmol 1977;61 (4) 250- 254
PubMedArticle
5.
Donnenfeld  EDCohen  EArentsen  JGenvert  GILaibson  PR Changing trends in contact lens associated corneal ulcers: an overview of 116 cases. CLAO J 1986;12 (3) 145- 149
PubMed
6.
Poggio  ECGlynn  RJSchein  OD  et al.  The incidence of ulcerative keratitis among users of daily-wear and extended-wear soft contact lenses. N Engl J Med 1989;321 (12) 779- 783
PubMedArticle
7.
Lim  LLoughnan  MSullivan  L Microbial keratitis associated with wear of silicone hydrogel contact lenses. Br J Ophthalmol 2002;86 (3) 355- 357
PubMedArticle
8.
Smith  REMcRae  SM Contact lenses: convenience and complications. N Engl J Med 1989;321 (12) 824- 826
PubMedArticle
9.
Microbial Keratitis Study Group,Schein  ODGlynn  RJPoggio  ECSeddon  JMKenyon  KR The relative risk of ulcerative keratitis among users of daily-wear and extended-wear soft contact lenses: a case-control study. N Engl J Med 1989;321 (12) 773- 778
PubMedArticle
10.
Keay  LEdward  KNadhuvilath  T  et al.  Microbial keratitis: predisposing factors and morbidity. Ophthalmology 2006;113 (1) 109- 116
PubMedArticle
11.
Galentine  PGCohen  EJLaibson  PRAdams  CPMichaud  RArentsen  JJ Corneal ulcer associated with contact lens wear. Arch Ophthalmol 1984;102 (6) 891- 894
PubMedArticle
12.
Schein  ODOrmerod  DBarraquer  E  et al.  Microbiology of contact lens–related keratitis. Cornea 1989;8 (4) 281- 285
PubMedArticle
13.
Liesegang  TJ Contact lens–related microbial keratitis, part I: epidemiology. Cornea 1997;16 (2) 125- 131
PubMedArticle
14.
Stapleton  FDart  JKMinassian  D Risk factors with contact lens related suppurative keratitis. CLAO J 1993;19 (4) 204- 210
PubMed
15.
Morgan  PBEfron  NHill  EARaynor  MKWhiting  MATullo  AB Incidence of keratitis of varying severity among contact lens wearers. Br J Ophthalmol 2005;89 (4) 430- 436
PubMedArticle
16.
Schein  ODMcNally  JJKatz  J  et al.  The incidence of microbial keratitis among wearers of a 30-day silicone hydrogel extended-wear contact lens. Ophthalmology 2005;112 (12) 2172- 2179
PubMedArticle
17.
Liesegang  TJ Contact lens–related microbial keratitis, part II: pathophysiology. Cornea 1997;16 (3) 265- 273
PubMedArticle
18.
Donzis  PBMondino  BJWeissman  BABruckner  DA Microbial contamination of contact lens care system. Am J Ophthalmol 1987;104 (4) 325- 333
PubMed
19.
Wilson  LASawant  ADSimmons  RBAhearn  DG Microbial contamination of contact lens storage cases and solutions. Am J Ophthalmol 1990;110 (2) 193- 198
PubMed
20.
DiGaetano  MStern  GAZam  ZS The pathogenesis of contact lens–associated Pseudomonas aeruginosa corneal ulceration, II: an animal model. Cornea 1986;5 (3) 155- 158
PubMedArticle
21.
Fowler  SAGreiner  JVAllansmith  MR Attachment of bacteria to soft contact lenses. Arch Ophthalmol 1979;97 (4) 659- 660
PubMedArticle
22.
Dang  YNRao  AKastl  PRBlake  RCSchurr  MJBlake  DA Quantifying Pseudomonas aeruginosa adhesion to contact lenses. Eye Contact Lens 2003;29 (2) 65- 68
PubMedArticle
23.
Stern  GAZam  ZS The effect of enzymatic contact lens cleaning on adherence of Pseudomonas aeruginosa to soft contact lenses. Ophthalmology 1987;94 (2) 115- 119
PubMedArticle
24.
Fowler  SAAllansmith  MR The effect of cleaning soft contact lenses: a scanning electron microscopic study. Arch Ophthalmol 1981;99 (8) 1382- 1386
PubMedArticle
25.
John  TDesai  DSahm  D Adherence of Acanthamoeba castellani cysts and trophozoites to unworn soft contact lenses. Am J Ophthalmol 1989;108 (6) 658- 664
PubMed
26.
Jeng  BHMcLeod  SD Microbial keratitis. Br J Ophthalmol 2003;87 (7) 805- 806
PubMedArticle
27.
Levey  SBKatz  HRAbrams  DAHirschbein  MJMarsh  MJ The role of cultures in the management of ulcerative keratitis. Cornea 1997;16 (4) 383- 386
PubMedArticle
28.
Hong Kong Microbial Keratitis Study Group,Lam  DSCHouang  EFan  DSP Incidence and risk factors for microbial keratitis in Hong Kong: comparison with Europe and North America. Eye 2002;16 (5) 608- 618
PubMedArticle
29.
Bourcier  TThomas  FBorderie  VChaumeil  CLaroche  L Bacterial keratitis: predisposing factors, clinical and microbiological review of 300 cases. Br J Ophthalmol 2003;87 (7) 834- 838
PubMedArticle
30.
Bennett  HGBHay  JKirkness  CMSeal  DVDevonshire  P Antimicrobial management of presumed microbial keratitis: guidelines for treatment of central and peripheral ulcers. Br J Ophthalmol 1998;82 (2) 137- 145
PubMedArticle
31.
Mela  EKGiannelou  IPKoliopoulos  JXGartaganis  SP Ulcerative keratitis in contact lens wearers. Eye Contact Lens 2003;29 (4) 207- 209[published correction appears in Eye Contact Lens. 2004;30(1):following table of contents]
PubMedArticle
32.
Mayo  MSSchlitzer  RLWard  MAWilson  LAAhearn  DG Association of Pseudomonas and Serratia corneal ulcers with use of contaminated solutions. J Clin Microbiol 1987;25 (8) 1398- 1400
PubMed
33.
Alexandrakis  GAlfonso  ECMiller  D Shifting trends in bacterial keratitis in south Florida and emerging resistance to fluoroquinolones. Ophthalmology 2000;107 (8) 1497- 1502
PubMedArticle
34.
Cohen  EJFulton  JCHoffman  CJRapuano  CJLaibson  PR Trends in contact lens–associated corneal ulcers. Cornea 1996;15 (6) 566- 570
PubMedArticle
35.
Mah-Sadorra  JHNajjar  DMRapuano  CJLaibson  PRCohen  EJ Serratia corneal ulcers: a retrospective clinical study. Cornea 2005;24 (7) 793- 800
PubMedArticle
36.
Hume  EBStapleton  FWilcox  MD Evasion of cellular ocular defenses by contact lens isolates of Serratia marcescens. Eye Contact Lens 2003;29 (2) 108- 112
PubMedArticle
37.
Martins  ENFarah  MEAlvarenga  SYu  MCHöflin-Lima  AL Infectious keratitis: correlation between corneal and contact lens cultures. CLAO J 2002;28 (3) 146- 148
PubMed
Clinical Sciences
September 2007

Association Between Cultures of Contact Lens and Corneal Scraping in Contact Lens–Related Microbial Keratitis

Author Affiliations

Author Affiliations: Centre for Eye Research Australia, University of Melbourne, and Corneal Unit, Royal Victorian Eye and Ear Hospital (Drs Das, Taylor, and Vajpayee), and Department of Microbiology, St Vincent's Hospital (Dr Sheorey), Melbourne, Australia.

Arch Ophthalmol. 2007;125(9):1182-1185. doi:10.1001/archopht.125.9.1182
Abstract

Objective  To study the association between cultures of contact lens and corneal scraping in contact lens–related microbial keratitis.

Methods  A retrospective analysis of the culture results of corneal scrapings and contact lenses of patients with contact lens–related microbial keratitis who were initially seen at Royal Victorian Eye and Ear Hospital, Melbourne, Australia, between January 1, 2001, and December 31, 2004, was conducted.

Results  Fifty eye specimens of 49 patients were included in the study. Corneal scrapings and contact lenses were culture positive in 17 eyes (34%) and in 35 eyes (70%), respectively. In 13 eyes, corneal scrapings and contact lenses yielded identical organisms. Serratia marcescens was the most common organism isolated from the corneal scrapings and from the contact lenses.

Conclusion  Contact lens culture may sometimes give a clue to the organism involved in cases of microbial keratitis in which the corneal scraping is culture negative and may help in choosing the appropriate antimicrobial therapy.

Contact lens wear is associated with a significant risk of microbial keratitis leading to severe sight-threatening complications.1,2 Microbial keratitis has been seen in all types of lenses, including rigid gas-permeable lenses, hard or polymethylmethacrylate lenses, and high- and low-oxygen transmissibility soft lenses, as well as with all modes of wear, including daily wear, extended wear, therapeutic wear, and continuous wear.37 Patients using soft contact lenses are at greater risk of developing microbial keratitis than those using other lenses.8

Different organisms have been associated with contact lens–related microbial keratitis. Compared with non–contact lens–related microbial keratitis, gram-negative rods are more prevalent in contact lens–related microbial keratitis.2,9 We undertook this study to investigate the association between cultures of contact lens and cultures of corneal scraping in cases of contact lens–related microbial keratitis.

METHODS

The clinical records of all soft contact lens–related microbial keratitis at the Royal Victorian Eye and Ear Hospital, Melbourne, Australia, where the corneal scrapings and the contact lenses were sent for culture from January 1, 2001, to December 31, 2004, were reviewed. Patients using therapeutic contact lenses were excluded from this study. The following data were collected from each medical record: age, sex, clinical manifestation, microbiological results, and any predisposing factor (other than the routine contact lens care).

All patients had undergone detailed clinical evaluation and slitlamp examination. The ulcers were routinely scraped for Gram-stained and fluorescent brightener–stained (Blankophor; Bayer, Wuppertal, Germany) smears and for plating on blood agar, chocolate agar, Saboraud dextrose agar, thioglycolate broth, and nonnutrient agar. For culture, contact lenses were sent in sterile water in a sterile container. If the patient was not wearing the contact lenses during the initial visit, contact lenses were sent in the patient's contact lens case for the culture. In the laboratory, the contact lens cases were opened without touching the interior, and a sterile swab or loop was used to culture the solution in the case. If the contact lens case was dry, a sterile cotton-wool swab moistened with sterile isotonic sodium chloride solution was used to swab the interior of the case. Intensive topical antimicrobial therapy was initiated immediately after the corneal scrapings were sent for microbiological investigations. Treatment was modified according to the microbiological findings, whenever required.

RESULTS

Fifty eyes of 49 patients with contact lens–related microbial keratitis were included in the present study. One patient had simultaneous involvement of both eyes. The mean ± SD age was 34 ± 12 years (age range, 17-59 years).

Seventeen corneal scrapings (34%) and 35 contact lenses (70%) were culture positive (Table 1), and of these, 13 corneal scrapings (76%) yielded organisms identical to the ones grown in their contact lens cultures. In 2 eyes, different organisms were isolated from the corneal scrapings and the contact lenses. In 2 eyes, only the corneal scrapings were culture positive.

Serratia marcescens was the most common organism in the corneal scrapings (n = 9) and in the contact lenses (n = 19), followed by Pseudomonas aeruginosa (Table 2). In 1 corneal scraping (2%) and in 8 contact lenses (16%), multiple organisms were isolated.

Fluorescent brightener–stained smears were positive for Acanthamoeba cysts in the corneal scrapings and in the contact lenses of 2 eyes. Acanthamoeba species was cultured from 1 corneal scraping and from 2 contact lenses. Four contact lenses (1 Candida albicans, 2 yeasts other than C albicans, and 1 Paecilomyces species) were culture positive for fungus.

In 11 eyes, ulcer was restricted to the peripheral cornea. Of these, corneal scrapings were culture positive in 1 eye (9%). In the remaining 39 eyes, infiltrate was localized to the central cornea or to the midperipheral to peripheral cornea, and of these, corneal scrapings were culture positive in 16 of 39 cases (41%).

In 27 patients, contact lenses of both eyes were sent for culture. Of these, identical organisms were cultured for the contact lenses of both eyes in 21 patients. In 5 patients, the contact lenses of both eyes did not yield any organism, and in 1 patient, the contact lenses yielded different organisms. Among 10 patients who were using topical antibiotics at the initial visit, 4 corneal scrapings and 7 contact lenses were culture positive.

COMMENT

Various risk factors that can lead to microbial keratitis include ocular trauma, contact lens wear, eyelid malalignment, ocular surface diseases, and corticosteroid use (including topical corticosteroids).10 Contact lens–related corneal infections continue to be a major challenge to ophthalmologists and to lens care practitioners. With continuous improvement in the lens material and design, as well as in disinfecting and storing solutions, contact lens use is on the rise. However, it has become a major predisposing factor for microbial keratitis, contributing to more than 30% of cases in some published studies.11,12

The major risk factor for contact lens–related microbial keratitis is overnight use of soft contact lenses; the risk increases incrementally with the number of nights of continuous wear. Higher risks have also been related to smoking, male sex, and lower socioeconomic status.13 However, in our series, there were more women (27 of 49 [55%]) with contact lens–related microbial keratitis. Patient sex and duration of overnight wear have been reported to be associated with microbial keratitis, whereas patient age and socioeconomic status were associated with sterile keratitis.14 Silicone hydrogel lenses carry 5 times decreased risk of developing severe keratitis associated with extended wear compared with hydrogel lenses.15 The incidence of loss of visual acuity caused by microbial keratitis is low in silicone hydrogel contact lens users.16 Compliance of patients and contamination of contact lenses and contact lens products are significant risk factors.17 The most frequently contaminated item used in the care of contact lenses is the disinfectant and storage case.18,19

The propensity of bacteria to adhere to soft contact lenses in areas of deposits has been noted by some authors.20,21 Bacterial adhesion to contact lenses may depend on the soft contact lens material.22 Effective enzymatic cleaning of mucin-coated hydrogel lenses has been shown to reduce the adherence of Pseudomonas to the lens.23 However, electron microscopic findings have shown that the contact lens coating on worn soft contact lenses is not completely removed using surfactant or enzymatic cleaners.24 Firm adherence of Acanthamoeba cysts and trophozoites to soft contact lenses has also been demonstrated.25

Standard investigations of microbial keratitis include corneal scraping. Incidences of negative culture results from corneal scrapings of suspected bacterial keratitis and of ulcerative keratitis have been reported to be 23%26 and 53%,27 respectively. Lam et al28 found 36% of corneal scrapings to be culture positive in cases of contact lens–related microbial keratitis, which is comparable to our percentage (34% [17 of 50 specimens]), whereas Bourcier et al29 reported it to be 63%. Patients with peripheral infiltrates tend to have fewer positive results of corneal scraping cultures, varying from 9%28 to 25%.30 In our series, corneal scraping cultures were positive in 1 of 11 cases with peripheral infiltrates (9%).

In the event of contact lens–related microbial keratitis, we have an additional diagnostic technique of contact lens culture in our armamentarium. Mela et al31 demonstrated the importance of culture of contact lenses and of contact lens storage solutions in addition to the corneal scrapings. They found that 67% of the negative corneal scraping cases were positive on contact lens culture. In our series, 20 of the 50 negative corneal scraping cases (40%) were positive on contact lens culture. Conversely, in 2 eyes, corneal scraping culture was positive, but contact lens culture was negative. This may be because the contact lenses were sent in isotonic sodium chloride solution (washing off a small number of organisms on it) rather than in their case.

Contact lens culture helps in providing some vital clues, especially in the situation in which corneal scraping results are negative and the patient is already taking a broad-spectrum antibiotic at the initial visit. However, these results should be interpreted with caution, keeping common contaminants in mind.

Although P aeruginosa is the most frequently isolated pathogen from contact lens–related corneal infections,2,5 in our study S marcescens was the most common organism isolated from corneal scrapings and from contact lenses. Serratia marcescens can survive in solutions preserved with chlorhexidine gluconate and benzalkonium chloride.32 Alexandrakis et al33 identified S marcescens as the second most common gram-negative isolate in microbial keratitis. However, among the contact lens wearers, it equaled Pseudomonas as the most common isolates. These authors documented a shifting trend in the type of organism (the number of Pseudomonas cases seems to be decreasing over time) in contact lens–associated ulcerative keratitis. Cohen et al34 also documented a decrease in the number of Pseudomonas infections in contact lens patients. This may be owing to the fact that more emphasis is being given to developing strategies aimed at Pseudomonas elimination; hence, the incidence of other water-borne organisms such as Serratia and others is increasing.

Serratia marcescens keratitis is known to be associated with abnormal ocular surface, use of topical medication, and contact lens wear.35 The ability of S marcescens to resist phagocytosis and to grow to high levels in the presence of polymorphonuclear leucocytes, particularly when grown as a biofilm on contact lenses, may be a mechanism by which this bacterium can survive the ocular defense system.36 Like Pseudomonas, Serratia is inherently resistant to several antimicrobial agents and is capable of readily acquiring resistance.35

Martins et al37 reported an overall concordance of 84% between cultures obtained from corneal scrapings and from contact lenses. Our results demonstrate an association between the corneal scraping culture and contact lens culture (P < .001). In our study, the lower positive rate of corneal scraping culture compared with contact lens culture might be partly owing to culture of all the corneal scrapings in presumed contact lens–related microbial keratitis irrespective of their size. Prior use of antibiotics before the corneal scraping is taken, as well as the propensity of bacterial adherence to contact lens, could be responsible for the discrepancy between the culture results of corneal scrapings and contact lenses. Furthermore, this is a retrospective analysis of data, and a prospective study may help clarify some discrepancies.

Donzis et al18 found that in 52 of 100 asymptomatic patients, some elements of the contact lens care system were contaminated with microorganisms. In our study, 21 patients' contact lenses of the unaffected eyes grew similar organisms as those of the affected eyes.

Our study highlights the fact that contact lens culture may help in identification of the causative organism in many cases of contact lens–related microbial keratitis. Also, contact lens culture may give a clue regarding the identity of the causative organism in situations in which the corneal scarping is culture negative and may help in choosing the appropriate antimicrobial agent. However, contact lens cultures cannot replace the corneal scraping cultures, a gold standard for the causative diagnosis of microbial keratitis, and caution must be exercised in interpreting these results.

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Article Information

Correspondence: Rasik B. Vajpayee, MS, FRCS(Edin), FRANZCO, Centre for Eye Research Australia, University of Melbourne, and Corneal Unit, Royal Victorian Eye and Ear Hospital, Locked Bag 8, East Melbourne, VIC 8002, Australia (rasikv@unimelb.edu.au).

Submitted for Publication: November 24, 2006; final revision received February 13, 2007; accepted February 17, 2007.

Financial Disclosure: None reported.

References
1.
Wong  TYNg  TPFong  KSTan  DT Risk factors and clinical outcomes between fungal and bacterial keratitis: a comparative study. CLAO J 1997;23 (4) 275- 281
PubMed
2.
Dart  JK Predisposing factors in microbial keratitis: the significance of contact lens wear. Br J Ophthalmol 1988;72 (12) 926- 930
PubMedArticle
3.
Ruben  M Acute eye disease secondary to contact lens wear. Lancet 1976;1 (7951) 138- 140
PubMedArticle
4.
Cooper  RLConstable  I Infective keratitis in soft contact lens wearers. Br J Ophthalmol 1977;61 (4) 250- 254
PubMedArticle
5.
Donnenfeld  EDCohen  EArentsen  JGenvert  GILaibson  PR Changing trends in contact lens associated corneal ulcers: an overview of 116 cases. CLAO J 1986;12 (3) 145- 149
PubMed
6.
Poggio  ECGlynn  RJSchein  OD  et al.  The incidence of ulcerative keratitis among users of daily-wear and extended-wear soft contact lenses. N Engl J Med 1989;321 (12) 779- 783
PubMedArticle
7.
Lim  LLoughnan  MSullivan  L Microbial keratitis associated with wear of silicone hydrogel contact lenses. Br J Ophthalmol 2002;86 (3) 355- 357
PubMedArticle
8.
Smith  REMcRae  SM Contact lenses: convenience and complications. N Engl J Med 1989;321 (12) 824- 826
PubMedArticle
9.
Microbial Keratitis Study Group,Schein  ODGlynn  RJPoggio  ECSeddon  JMKenyon  KR The relative risk of ulcerative keratitis among users of daily-wear and extended-wear soft contact lenses: a case-control study. N Engl J Med 1989;321 (12) 773- 778
PubMedArticle
10.
Keay  LEdward  KNadhuvilath  T  et al.  Microbial keratitis: predisposing factors and morbidity. Ophthalmology 2006;113 (1) 109- 116
PubMedArticle
11.
Galentine  PGCohen  EJLaibson  PRAdams  CPMichaud  RArentsen  JJ Corneal ulcer associated with contact lens wear. Arch Ophthalmol 1984;102 (6) 891- 894
PubMedArticle
12.
Schein  ODOrmerod  DBarraquer  E  et al.  Microbiology of contact lens–related keratitis. Cornea 1989;8 (4) 281- 285
PubMedArticle
13.
Liesegang  TJ Contact lens–related microbial keratitis, part I: epidemiology. Cornea 1997;16 (2) 125- 131
PubMedArticle
14.
Stapleton  FDart  JKMinassian  D Risk factors with contact lens related suppurative keratitis. CLAO J 1993;19 (4) 204- 210
PubMed
15.
Morgan  PBEfron  NHill  EARaynor  MKWhiting  MATullo  AB Incidence of keratitis of varying severity among contact lens wearers. Br J Ophthalmol 2005;89 (4) 430- 436
PubMedArticle
16.
Schein  ODMcNally  JJKatz  J  et al.  The incidence of microbial keratitis among wearers of a 30-day silicone hydrogel extended-wear contact lens. Ophthalmology 2005;112 (12) 2172- 2179
PubMedArticle
17.
Liesegang  TJ Contact lens–related microbial keratitis, part II: pathophysiology. Cornea 1997;16 (3) 265- 273
PubMedArticle
18.
Donzis  PBMondino  BJWeissman  BABruckner  DA Microbial contamination of contact lens care system. Am J Ophthalmol 1987;104 (4) 325- 333
PubMed
19.
Wilson  LASawant  ADSimmons  RBAhearn  DG Microbial contamination of contact lens storage cases and solutions. Am J Ophthalmol 1990;110 (2) 193- 198
PubMed
20.
DiGaetano  MStern  GAZam  ZS The pathogenesis of contact lens–associated Pseudomonas aeruginosa corneal ulceration, II: an animal model. Cornea 1986;5 (3) 155- 158
PubMedArticle
21.
Fowler  SAGreiner  JVAllansmith  MR Attachment of bacteria to soft contact lenses. Arch Ophthalmol 1979;97 (4) 659- 660
PubMedArticle
22.
Dang  YNRao  AKastl  PRBlake  RCSchurr  MJBlake  DA Quantifying Pseudomonas aeruginosa adhesion to contact lenses. Eye Contact Lens 2003;29 (2) 65- 68
PubMedArticle
23.
Stern  GAZam  ZS The effect of enzymatic contact lens cleaning on adherence of Pseudomonas aeruginosa to soft contact lenses. Ophthalmology 1987;94 (2) 115- 119
PubMedArticle
24.
Fowler  SAAllansmith  MR The effect of cleaning soft contact lenses: a scanning electron microscopic study. Arch Ophthalmol 1981;99 (8) 1382- 1386
PubMedArticle
25.
John  TDesai  DSahm  D Adherence of Acanthamoeba castellani cysts and trophozoites to unworn soft contact lenses. Am J Ophthalmol 1989;108 (6) 658- 664
PubMed
26.
Jeng  BHMcLeod  SD Microbial keratitis. Br J Ophthalmol 2003;87 (7) 805- 806
PubMedArticle
27.
Levey  SBKatz  HRAbrams  DAHirschbein  MJMarsh  MJ The role of cultures in the management of ulcerative keratitis. Cornea 1997;16 (4) 383- 386
PubMedArticle
28.
Hong Kong Microbial Keratitis Study Group,Lam  DSCHouang  EFan  DSP Incidence and risk factors for microbial keratitis in Hong Kong: comparison with Europe and North America. Eye 2002;16 (5) 608- 618
PubMedArticle
29.
Bourcier  TThomas  FBorderie  VChaumeil  CLaroche  L Bacterial keratitis: predisposing factors, clinical and microbiological review of 300 cases. Br J Ophthalmol 2003;87 (7) 834- 838
PubMedArticle
30.
Bennett  HGBHay  JKirkness  CMSeal  DVDevonshire  P Antimicrobial management of presumed microbial keratitis: guidelines for treatment of central and peripheral ulcers. Br J Ophthalmol 1998;82 (2) 137- 145
PubMedArticle
31.
Mela  EKGiannelou  IPKoliopoulos  JXGartaganis  SP Ulcerative keratitis in contact lens wearers. Eye Contact Lens 2003;29 (4) 207- 209[published correction appears in Eye Contact Lens. 2004;30(1):following table of contents]
PubMedArticle
32.
Mayo  MSSchlitzer  RLWard  MAWilson  LAAhearn  DG Association of Pseudomonas and Serratia corneal ulcers with use of contaminated solutions. J Clin Microbiol 1987;25 (8) 1398- 1400
PubMed
33.
Alexandrakis  GAlfonso  ECMiller  D Shifting trends in bacterial keratitis in south Florida and emerging resistance to fluoroquinolones. Ophthalmology 2000;107 (8) 1497- 1502
PubMedArticle
34.
Cohen  EJFulton  JCHoffman  CJRapuano  CJLaibson  PR Trends in contact lens–associated corneal ulcers. Cornea 1996;15 (6) 566- 570
PubMedArticle
35.
Mah-Sadorra  JHNajjar  DMRapuano  CJLaibson  PRCohen  EJ Serratia corneal ulcers: a retrospective clinical study. Cornea 2005;24 (7) 793- 800
PubMedArticle
36.
Hume  EBStapleton  FWilcox  MD Evasion of cellular ocular defenses by contact lens isolates of Serratia marcescens. Eye Contact Lens 2003;29 (2) 108- 112
PubMedArticle
37.
Martins  ENFarah  MEAlvarenga  SYu  MCHöflin-Lima  AL Infectious keratitis: correlation between corneal and contact lens cultures. CLAO J 2002;28 (3) 146- 148
PubMed
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