Skip to main content
PMC home page
UKPMC Funders Author Manuscripts logoLink to UKPMC Funders Author Manuscripts
. Author manuscript; available in PMC: 2012 Jul 24.
Published in final edited form as: Br J Ophthalmol. 2011 Apr 8;95(6):762–767. doi: 10.1136/bjo.2009.169607

Geographic Variations in Microbial Keratitis: An analysis of the Peer-Reviewed Literature

Ameet Shah 1, Arun Sachdev 2, David Coggon 3, Parwez Hossain 4
PMCID: PMC3403809  EMSID: UKMS49224  PMID: 21478201

summary

The epidemiology of microbial keratitis has been investigated in several studies by analysis of organisms cultured from corneal scrapes. However, a comparison of the frequency of different organisms causing keratitis in different parts of the world is lacking. We present a review incorporating an analysis of data from studies worldwide. The data provide a comparison of the frequency of culture-positive organisms found in different parts of the world.

The highest proportion of bacterial corneal ulcers was reported in studies from North America, Australia, the Netherlands and Singapore. The highest proportion of staphylococcal ulcers was found in a study from Paraguay whilst the highest proportion of pseudomonas ulcers was reported in a study from Bangkok. The highest proportions of fungal infections were found in studies from India and Nepal. Possible explanations for these observed geographic variations are discussed.

Keywords: cornea, keratitis, eye, infection, epidemiology

INTRODUCTION

Microbial keratitis is a potentially serious corneal infection and a major cause of visual impairment worldwide. A conservative estimate of the number of corneal ulcers occurring annually in the developing world alone is 1.5-2 million.[1] Permanent visual dysfunction has been reported in a significant proportion of patients in both developing [2] and developed [3] countries. Srinivasan et al [4] comment that ulceration of the cornea in south India ‘is a blinding disease of epidemic proportions’.

Various micro-organisms can cause microbial keratitis and predisposing risk factors vary from one geographic region to another. They include pre-existing corneal disease as well as other risk factors such as contact lens wear, surgical or non-surgical trauma and ocular surface disease.[5-7]

There is limited comparative information on international patterns of causative organisms in microbial keratitis. With increasing rates of migration and international travel, an awareness of these geographical variations is relevant for clinicians treating microbial keratitis, and especially for those planning to work in regions where they have not previously practised. The aim of this review is to summarise the published literature that provides information on the worldwide variation in organisms causing microbial keratitis.

METHODS

Search Strategy

A systematic review of the current literature pertaining to the prevalence of causative organisms responsible for microbial keratitis was conducted. Pubmed searches were performed and verified in April 2009 by two independent investigators. The terms ‘microbial keratitis’, ‘bacterial keratitis’ and ‘infectious keratitis’ were entered into Pubmed. Only papers presenting data that were collected after 1st January 1990 were examined, and the search was restricted to English Language and human studies. Only studies that cultured at least 50 organisms in total were included. Titles and abstracts were read and a judgement was made as to whether the paper provided culture results for microbial keratitis in a specified geographical location. If this was felt to be the case then a full text request was made to access the original published data.

Studies looking only at infections related to use of contact lenses were excluded, as were studies looking only at limited age groups.

Extraction and Recording of Data

Papers were read and information was abstracted on the following variables: number of patients in the study, time period of reporting, region, method by which organisms were isolated, method of culture, rate of positive cultures, and number of contact lens wearers in the study sample. These data were then entered then into a Microsoft Excel spread sheet.

With regard to the microorganisms cultured, the total numbers in each of the following categories were abstracted and recorded: gram positive organisms, staphylococcal species, streptococcal species, gram negative organisms, pseudomonal species, protozoa, fungi/yeasts, aspergillus species and candida species.

Classification of income levels and GNI subheading

The prevalence of different causative organisms was compared according to countries’ gross national incomes (GNIs) (source = http://web.worldbank.org). Income groups were defined by 2007 GNI per capita, calculated using the World Bank Atlas method.[8] The groups distinguished were: low income, $935 or less; lower middle income, $936 - $3,705; upper middle income, $3,706 - $11,455; and high income, $11,456 or more.

Statistical analysis

Statistical analysis was performed using ‘Analyse-it’ version 2.20 software. Spearman’s correlation coefficients were used to explore associations between:

  1. prevalence of certain types of organism and GNI; and between

  2. prevalence of contact lens wear and prevalence of pseudomonas.

RESULTS

3883 publications were identified through the preliminary Pubmed search. Of these, 37 papers met the inclusion criteria. One paper was excluded because it included a significant number of cases that the authors deemed to constitute an outbreak of suture-related infections.[9] Twelve of the included papers were from the Indian subcontinent, 7 from North America and Canada, 6 from the Far East, 5 from Australasia, 4 from Europe, 2 from Africa (both from Ghana) and 1 from South America. The mean GNI of the countries studied was $20834 (range $470 – $59880). The number of patients ranged from 73 to 3183. The time periods of study ranged from 3 – 192 months, although three studies did not specify the study period. The proportion of keratitis patients with a recent history of contact lens wear was reported in only 22 studies and ranged from 0.33% (West Bengal [10]) to 50.3% (Paris[11]). Three studies reported on only culture-positive cases and so appear to have 100% culture-positive rates in Table 1. In the remainder of the studies culture-positive rates ranged from 35% - 86%.

Table 1. Studies meeting criteria for inclusion in review.

Location of
study
(reference)		 GNI per
capita
($)		 Time
period
(months)		 Number of
patients		 Proportion (%) of
patients using
contact lenses		 Method of culture Proportion (%) of
patients with
positive cultures
Africa
Ghana(16) 590 24 290 unspecified 2 50
Accra,
Ghana(18)		 590 unspecified 199 unspecified Chocolate, Sabouraud 64
Indian
Subcontinent
Nepal, India(19) 340 36 447 unspecified Sheep’s blood agar, Chocolate, brain-
heart infusion, Sabouraud		 68
Chittagong,
Bangladesh(20)		 470 unspecified 151 unspecified Blood,
Chocolate,thiogylcollate,Sarbarouds		 63
Tamil Nadu(16) 950 24 800 unspecified 1 69
East Bengal(10) 950 36 1198 0.33 Blood, chocoloate, potatoe dextrose
agar, sabarouds dextrose		 68
New Delhi(2) 950 unspecified 100 2.0 Blood, chocolate, thioglycollate,
sabarouds		 65
Madurai,S.
India(4)		 950 3 434 unspecified Sheep’s blood agar, potato dextrose
agar, chocolate, brain-heart infusion		 68
Hyderabad,
India(21)		 950 95 1092 unspecified Sheep’s blood agar, Chocolate, Nonnutrient,
Sarbarouds, brain-heart infusion,
potato dextrose agar		 35
Tamil Nadu, India
(22)		 950 36 3183 1.04 unspecified 71
Hyderabad, India
(17)		 950 15 170 Unspecified Unspecified 69.4
Delhi, India (23) 950 12 1000 8.2 Unspecified 56.8
Riyadh, Saudi
Arabia** (24)		 15440 12 103 17.48 blood, chocolate, Sabouraud’s and
thioglycolate		 unspecified for 2005**
Baghdad,
Iraq†(25)		 2320 36 394 6.09 blood, chocolate, Sabouraud’s and brainheart
infusion		 58.6
South America
Asuncion,
Paraquay(14)		 1670 162 660 unspecified Blood,Chocolate thiogylcollate, sabarouds 79
Far East
Taipei, Taiwan(26) 16590 120 453 44.3* Chocolate,sheeps, sabarouds 56
Taipai,
Taiwan(27)		 16590 12 314 9.9 Blood,Chocolate, thiogylcollate, brainheart
infusion		 43
Singapore(28) 32470 60 80 22.5 Blood, chocolate,thioglycollate,
sabarouds, brain heart infusion		 100
Singapore(29) 32470 22 103 34 Blood,Chocolate, thiogylcollate,
Sabarouds		 50
Hong Kong(5) 31610 17 223 26.5 Blood,Chocolate, thiogylcollate,
Sabarouds ,non-nutrient Page’s saline
agar		 35
Bangkok,
Thailand (15)		 34000 47 127 24.4 sterile kimura spatula, blood, chocolate
agar, thoiglycolate		 100
Australasia
Auckland, NZ(3) 28780 24 98 26 Blood, sabarouds, thiogylcollate, brain-
heart infusion, Page’s amoebic saline		 71
Christchurch,
New
Zealand(30)		 28780 60 78 unspecified Sheep’s blood agar, Chocolate 59
Adelaide(14) 35960 61 211 unspecified Blood, chocolate, sabarouds 64
Victoria,
Australia(7)		 35960 24 291 33.7 Chocolate, Sabarouds 49
Brisbane,
Australia(6)		 35960 60 231 22.9 blood, MacConkey, Chocolate,
sabarouds		 65
North America
and Canada
Toronto(31) 39420 25 95 11.6 Blood, chocolate, inhibitory mould agar,
thioglycollate		 63
Miami(32) 46040 108 2920 10.4* Chocolate,sheep, sabouraud,
thioglycollate		 50
Pittsburgh(33) 46040 60 825 Unspecified 4 100
Los Angeles(12) 46040 31 81 Unspecified Blood, chocolate, thioglycollate,
sabarouds		 76
Texas (34) 46040 60 131 28.8 scalpel blade, calcium alginate swabs or
cotton tipped applicator. Chocolate,
blood, thiglycollate, sabourauds dextrose		 52.5
Durham, USA
(35)		 46040 84 453 unspecified calcium alginate swabs, blood,
chocolate,saborauds, thioglycolate		 68
Europe
Paris(11) 38500 21 291 50.3* 3 68
Laussanne,
Switzerland(36)		 59880 21 85 36 Blood, sarborauds, Chocolate, brain-heart
infusion		 86
Anatolia, Turkey
(37)		 8020 192 620 3.2 cotton-tipped swabs, chocolate, blood
agar, sarborauds		 48.4
Amsterdam
and Rotterdam
(38)		 45820 36 156 39.74 blood agar, chocolate agar, cooked
meat broth, Sabouraud agar		 58
Open in a new tab
1

sheeps blood agar, Sabarouds broth and sabarouds glucose agar and at tertiary centre brain heart infusion broth, chocolate agar and cysteine tryptone agar

2

sheeps blood agar, Sabarouds broth and inhibitory mould agar and at tertiary centre brain heart infusion broth, chocolate agar and cysteine tryptone agar

3

chocolate polyvitex agar, schaedler broth with globular extract, portagerm amies agar swab and sabouraud-chloramphencolgentamicin medium

4

sheep blood, chocolate, mannitol salt agar, sabourauds dextrose agar supplemented with gentamicin

*

paper did not specify the number of contact lens wearers. Instead they report on the number of isolates from contact lens wearers. The figure given in the table therefore represents the percentage of isolates retrieved from cases where CL wear was a risk factor

†

Estimated to be lower middle income ($936 to $3,705), value given in table is midpoint of this range

**

This paper presented paper for 1995 and 2005, only 2005 data have been extracted in our study

Among studies which looked at non-bacterial as well as bacterial organisms, Los Angeles [12] and Adelaide [13] had the highest percentages of bacterial cases (95% in both), with Paraguay [14] having the highest percentage of staphylococcal species (79%), and Bangkok [15] the highest proportion of pseudomonal infections (55%). Tamil Nadu [16] had the highest percentage of streptococcal infections (47%). The highest percentage of protozoal infections (7%) was found in a study from Hong Kong.[5]

East India [10] had the highest proportion of corneal infections attributable to fungi (67%). When considering those countries with a significant proportion of fungal ulcers (we have arbitrarily chosen a cut-off of 10% or more), East India also had the highest percentage of aspergillus (60% of all fungal cultures) whereas the highest percentage of fusarium (73% of all fungal cultures) was found in a study from Hyderabad [17].

Statistically significant correlations were found between Gross National Income and percentages of bacterial, fungal and streptococcal isolates (see Figures 1-3). Surprisingly there was no statistically significant correlation between percentage of pseudomonal isolates and percentage of contact lens wearers (see Figure 4). 95% confidence intervals and p values for these analyses are provided in table 4.

Figure 1.

Figure 1

Open in a new tab

Scatterplot showing percentage of bacterial isolates in studies not looking exclusively at bacterial causes of microbial keratitis plotted against gross national income (US Dollars per capita)

Figure 2.

Figure 2

Open in a new tab

Scatterplot to show percentage of fungal isolates plotted against gross national income (US Dollars per capita)

Figure 3.

Figure 3

Open in a new tab

Scatterplot to show streptococcal isolates (expressed as a percentage of total bacterial isolates) plotted against gross national income (US Dollars per capita)

Figure 4.

Figure 4

Open in a new tab

Scatterplot to show pseudomonas isolates (expressed as a percentage of total bacterial isolates) plotted against contact lens wearers (as a percentage of total number of patients included in study)

Table 4. 95% confidence intervals and p values for Spearman’s Correlation analysis.

Variables analysed Correlation coefficient 95% confidence limit 2 tailed p value
Prevalence of bacteria, GNI 0.83 0.68 to 0.91 <0.0001
Prevalence of fungi, GNI −0.81 −0.90 to −0.66 <0.0001
Prevalence of Streptococci, GNI −0.43 −0.66 to −0.12 0.009
Prevalence of pseudomonas,
prevalence of contact lens
wearers		 0.13 −0.31 to 0.52 0.6
Open in a new tab

DISCUSSION

We have found a wide variation in the causative organisms for microbial keratitis in different parts of the world. To some degree this variation is explained by economic factors as well as contact lens wear. A high proportion of bacterial ulcers were reported from centres in developed countries (North America, Australia, and Western Europe). In these countries, patients are far less likely to be agricultural workers, and so have a reduced risk of trauma from organic matter, which is known to be a risk factor for fungal infection.[28]

A high percentage of staphylococcus species (79%) was recorded in the study from Paraguay [14] although the reason for this is not clear. Of note, the authors comment that their patients have to make long journeys to their hospital. Thus, their data may reflect more severe cases of microbial keratitis.

The study from Tamil Nadu [16] found the highest proportion of streptococcus species (46.8%). The authors noted that this figure was only 18.5% in 1986 and suggest that the trend might represent a genuine change in the bacterial flora due to changes in the climate and environment.

The study from Bangkok [15] had the highest proportion of pseudomonas infections (55%). Interestingly, this study did not have the highest proportion of contact lens wearers (only 24%). Other studies reported far higher proportions of contact lens wearers, for example 44% in a study from Taiwan [26] and 50% in the study from Paris [11]. When we compared the percentage of contact lens wearers with the percentage of pseudomonal infections (figure 4), the Spearman correlation coefficient was not statistically significant. Interestingly, Cohen et al. [39] at Wills Eye Hospital reported a decline in contact lens-related ulcers: during 1998 to 1991, contact lens wear accounted for 44% of all ulcers, but during 1992 to 1995, it accounted for only 30%. The authors speculated that their figures might reflect a reduction in the number of referrals to their unit due to the increased availability of fluoroquinolones in the community.

Trauma was a major risk factor for corneal infection in certain countries. In Paraguay [14], the percentage of cases with preceding trauma was 48%, in Eastern Nepal[19], 53%, in Madurai, South India[4], 65% and 83% in Eastern India[11] (most commonly from injury by the paddy or its stalk). The authors of this last study noted an increase in keratitis during harvesting season.

The above studies also addressed the frequency of self-medication prior to presentation at a tertiary referral unit. In the Madurai study, 20% of patients had been to a village healer and 87% had been started on topical medication, of whom 8% were on topical corticosteroids. In the study from Eastern India, 18% of patients had used medication before coming to clinic, and in the Paraguay study the proportion was 83%.

Jeng and McLeod[40] commented on the emerging resistance of bacterial infections to fluoroquinolones. In addition to changes in resistance patterns, studies have also demonstrated changing patterns of causative organisms over time in a given geographical location. Varaprasathan et al.[41] reported that the proportion of S. pneumoniae and P. aeruginosa ulcers in Northern California had decreased over a 50 year period whilst that of S. marcescens had increased over the same period. Sun et al.[24] reported a rise in the percentage of gram positive cocci in North China from 25% in 1991 to 70.8% in 1997, as well as a decrease in gram negative bacilli from 69% to 23.4% over a similar period.

Leck et al.[16] have previously compared corneal ulcers in Ghana and South India, whilst Lam et al.[5] have discussed differences between Hong Kong, Europe and North America. However, the present study is the first to present a worldwide comparison of corneal infections.

In interpreting this comparison, a number of limitations must be considered. Variations existed in the definition of microbial keratitis between studies. Lam et al, reporting on cases from Hong Kong [5], included patients with ‘the clinical presentation of a corneal stromal infiltrate >1 mm2’. This differs from Srinivasan et al [4] who included patients with ‘loss of the corneal epithelium with underlying stromal infiltration and suppuration associated with signs of inflammation with or without hypopyon’. There were variations in methods of culture. For example, one study [21] used Sheep’s blood agar, Chocolate, Non-nutrient, Sarbarouds, brain-heart infusion and potato dextrose agar, whilst another [18] used only Chocolate and Sabourauds media. Some studies did not specify the media used [17, 22, 23]. All studies included bacterial infections, but not all included fungal, protozoal and yeast organisms. The majority of studies looked at all cases of microbial keratitis whilst some looked only at patients requiring hospital admission (Wong et al. and Cheung et al. [3,31]). It is likely that in these studies, particularly virulent organisms will be over-represented. Finally, data are only available from centres that have conducted studies on microbial keratitis, limiting the coverage of certain regions of the world.

Despite these limitations, we have presented to our knowledge, for the first time, a worldwide overview of causative organisms in microbial keratitis demonstrating associations between specific types of microbial keratitis and national income.

Table 2. Proportion of culture-positive patients who tested positively for bacteria by location.

Location of study Number of isolates
Gram +ve bacteria
 Gram −ve bacteria
Any Staphylococci Streptococci Other Any Pseudomonas Other
Africa
Ghana 17 4 8 5 21 21 0
Accra, Ghana 34 18 11 5 29 17 12
Indian Subcontinent
Nepal, India		 136 102 31 3 21 18 3
Chittagong, Bangladesh 27 2 23 2 39 34 5
Tamil Nadu 178 63 110 5 57 35 22
East Bengal 214 174 28 12 84 63 21
New Delhi 35 28 2 5 17 10 7
Madurai, S. India 132 26 76 30 35 24 11
Hyderabad, India 198 92 60 46 45 27 18
Tamil Nadu, India 814 259 492 63 325 236 89
Hyderabad, India 80 43 27 0 13 6 7
Delhi, India 223 200 10 13 152 88 64
Riyadh, Saudi Arabia 130 75 26 29 45 16 29
Baghdad, Iraq 88 70 15 3 74 68 6
South America
Asuncion, Paraquay 278 210 42 226 132 46 96
Far East
Taiwan 67 21 21 25 120 95 25
Taipai, Taiwan 57 39 12 6 106 56 50
Singapore unspecified 4 4 unspecified 41 23 18
Singapore 9 5 4 0 42 23 19
Hong Kong 37 9 3 25 42 28 14
Bangkok 23 11 12 0 unspecified 43 unspecified
Australasia
Auckland, NZ 75 41 11 13 13 7 6
Christchurch, New Zealand 45 19 11 15 18 2 16
Adelaide 89 65 12 12 38 17 21
Victoria, Australia 72 56 8 8 29 10 19
Brisbane, Australia 75 41 11 23 56 44 12
North America and Canada
Toronto 43 32 10 1 20 7 13
Miami 637 278 89 270 664 345 319
Pittsburgh 797 638 115 44 256 71 185
LA 48 34 9 5 30 13 17
Texas 45 25 12 8 32 18 14
Durham 314 197 57 78 74 40 34
Europe
Paris 172 116 19 37 35 21 14
Laussanne, Switzerland 57 45 10 2 18 7 11
Anatolia, Turkey 155 115 35 5 20 15 5
Amsterdam and Rotterdam 46 25 16 5 58 35 23
Open in a new tab

Table 3. Proportion of culture-positive patients who tested positively for protozoa or fungi and yeasts by location.

Location of study Number of isolates
Protozoa
 Fungi and yeasts
Any Any Aspergillus Candida Other
Africa
Ghana 1 82 19 1 62
Accra, Ghana unspecified 65 10 1 45
Indian Subcontinent
Nepal, India unspecified 200 75 9 116
Chittagong, Bangladesh unspecified 48 24 1 23
Tamil Nadu 7 296 76 0 220
East Bengal 4 623 373 7 243
New Delhi unspecified 13 6 0 7
Madurai, S. India 3 155 25 unspecified 116
Hyderabad, India unspecified 146 43 2 101
Tamil Nadu, India 33 1176 294 unspecified 882
Hyderabad, India 3 22 5 1 16
Delhi, India 11 358 149 30 179
Riyadh, Saudi Arabia unspecified unspecified unspecified unspecified unspecified
Baghdad, Iraq unspecified 74 42 4 28
South America
Asuncion, Paraquay unspecified 209 37 4 168
Far East
Taiwan 11 34 5 10 19
Taipai, Taiwan unspecified unspecified unspecified unspecified unspecified
Singapore unspecified 29 5 3 21
Singapore unspecified unspecified unspecified unspecified unspecified
Hong Kong 6 5 unspecified 1 4
Bangkok 3 46 9 2 37
Australasia
Auckland, NZ unspecified 7 unspecified unspecified unspecified
Christchurch,New Zealand unspecified unspecified unspecified unspecified Unspecified
Adelaide unspecified 7 3 2 2
Victoria, Australia 4 7 unspecified 1 6
Brisbane, Australia unspecified 13 unspecified unspecified unspecified
North America and Canada
Toronto unspecified unspecified unspecified unspecified unspecified
Miami unspecified unspecified unspecified unspecified unspecified
Pittsburgh unspecified Unspecified unspecified unspecified
LA unspecified 4 unspecified unspecified 4
Texas 4 8 unspecified 3 unspecified
Durham unspecified unspecified unspecified unspecified unspecified
Europe
Paris unspecified unspecified unspecified unspecified unspecified
Laussanne, Switzerland unspecified unspecified unspecified unspecified unspecified
Anatolia, Turkey unspecified 50 10 15 25
Amsterdam and Rotterdam unspecified 2 0 2 0
Open in a new tab

References

  • 1.Whitcher JP, Srinivasan M, Upadhyay MP. Corneal blindness: A global perspective. Bull World Health Organ. 2001;79:214–21. [PMC free article] [PubMed] [Google Scholar]
  • 2.Vajpayee RB, Dada T, Saxena R, et al. Study of the First Contact Management Profile of Cases of Infectious Keratitis: A Hospital-Based Study. Cornea. 2000;19(1):52–56. doi: 10.1097/00003226-200001000-00011. [DOI] [PubMed] [Google Scholar]
  • 3.Wong T, Ormonde S, Gamble G, et al. Severe infective keratitis leading to hospital admission in New Zealand. Br J Ophthalmol. 2003;87(9):1103–8. doi: 10.1136/bjo.87.9.1103. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 4.Srinivasan M, Gonzales CA, George C, et al. Epidemiology and aetiological diagnosis of corneal ulceration in Madurai, south India. Br J Ophthalmol. 1997;81(11):965–71. doi: 10.1136/bjo.81.11.965. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 5.Lam DS, Houang E, Fan DS, et al. Hong Kong Microbial Keratitis Study Group Incidence and risk factors for microbial keratitis in Hong Kong: comparison with Europe and North America. Eye. 2002;16(5):608–18. doi: 10.1038/sj.eye.6700151. [DOI] [PubMed] [Google Scholar]
  • 6.Green M, Apel A, Stapleton F. Risk factors and causative organisms in microbial keratitis. Cornea. 2008;27(1):22–7. doi: 10.1097/ICO.0b013e318156caf2. [DOI] [PubMed] [Google Scholar]
  • 7.Keay L, Edwards K, Naduvilath T, et al. Microbial keratitis predisposing factors and morbidity. Ophthalmology. 2006;113(1):109–16. doi: 10.1016/j.ophtha.2005.08.013. [DOI] [PubMed] [Google Scholar]
  • 8. [accessed 21st June 2009]; http://web.worldbank.org/WBSITE/EXTERNAL/DATASTATISTICS/0,,contentMDK:20452009~isCURL:Y~menuPK:64133156~pagePK:64133150~piPK:64133175~theSitePK:239419,00.html.
  • 9.Simcock PR, Butcher JM, Armstrong M, Lloyd IC, Tullo AB. Investigation of microbial keratitis: an audit from 1988-1992. Acta Ophthalmol Scand. 1996;74(2):183–6. doi: 10.1111/j.1600-0420.1996.tb00067.x. [DOI] [PubMed] [Google Scholar]
  • 10.Basak SK, Basak S, Mohanta A, Bhowmick A. Epidemiological and microbiological diagnosis of suppurative keratitis in Gangetic West Bengal, eastern India. Indian J Ophthalmol. 2005;53(1):17–22. doi: 10.4103/0301-4738.15280. [DOI] [PubMed] [Google Scholar]
  • 11.Bourcier T, Thomas F, Borderie V, Chaumeil C, Laroche L. Bacterial keratitis: predisposing factors, clinical and microbiological review of 300 cases. Br J Ophthalmol. 2003;87(7):834–8. doi: 10.1136/bjo.87.7.834. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 12.McLeod SD, Kolahdouz-Isfahani A, Rostamian K, Flowers CW, Lee PP, McDonnell PJ. The role of smears, cultures, and antibiotic sensitivity testing in the management of suspected infectious keratitis. Ophthalmology. 1996;103(1):23–8. doi: 10.1016/s0161-6420(96)30738-0. [DOI] [PubMed] [Google Scholar]
  • 13.Leibovitch I, Lai TF, Senarath L, Hsuan J, Selva D. Eur J Ophthalmol. 2005;15(1):23–6. Infectious keratitis in South Australia: emerging resistance to cephazolin. [PubMed] [Google Scholar]
  • 14.Laspina F, Samudio M, Cibils D, Ta CN, Fariña N, Sanabria R, Klauss V, Miño de Kaspar H. Epidemiological characteristics of microbiological results on patients with infectious corneal ulcers: a 13-year survey in Paraguay. Graefes Arch Clin Exp Ophthalmol. 2004;242(3):204–9. doi: 10.1007/s00417-003-0808-4. [DOI] [PubMed] [Google Scholar]
  • 15.Sirikul T, Prabriputaloong T, Smathivat A, Chuck RS, Vongthongsri A. Predisposing factors and etiologic diagnosis of ulcerative keratitis. Cornea. 2008;27(3):283–7. doi: 10.1097/ICO.0b013e31815ca0bb. [DOI] [PubMed] [Google Scholar]
  • 16.Leck AK, Thomas PA, Hagan M, Kaliamurthy J, Ackuaku E, John M, Newman MJ, Codjoe FS, Opintan JA, Kalavathy CM, Essuman V, Jesudasan CA, Johnson GJ. Aetiology of suppurative corneal ulcers in Ghana and south India, and epidemiology of fungal keratitis. Br J Ophthalmol. 2002;86(11):1211–5. doi: 10.1136/bjo.86.11.1211. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 17.Sharma S, Taneja M, Gupta R, Upponi A, Gopinathan U, Nutheti R, Garg P. Comparison of clinical and microbiological profiles in smear-positive and smear-negative cases of suspected microbial keratitis. Indian J Ophthalmol. 2007;55(1):21–5. doi: 10.4103/0301-4738.29490. [DOI] [PubMed] [Google Scholar]
  • 18.Hagan M, Wright E, Newman M, Dolin P, Johnson G. Causes of suppurative keratitis in Ghana. Br J Ophthalmol. 1995;79(11):1024–8. doi: 10.1136/bjo.79.11.1024. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 19.Khanal B, Deb M, Panda A, Sethi HS. Laboratory diagnosis in ulcerative keratitis. Ophthalmic Res. 2005;37(3):123–7. doi: 10.1159/000084273. [DOI] [PubMed] [Google Scholar]
  • 20.Dunlop AA, Wright ED, Howlader SA, Nazrul I, Husain R, McClellan K, Billson FA. Suppurative corneal ulceration in Bangladesh. A study of 142 cases examining the microbiological diagnosis, clinical and epidemiological features of bacterial and fungal keratitis. Aust N Z J Ophthalmol. 1994;22(2):105–10. doi: 10.1111/j.1442-9071.1994.tb00775.x. [DOI] [PubMed] [Google Scholar]
  • 21.Sharma S, Kunimoto DY, Gopinathan U, Athmanathan S, Garg P, Rao GN. Evaluation of corneal scraping smear examination methods in the diagnosis of bacterial and fungal keratitis: a survey of eight years of laboratory experience. Cornea. 2002;21(7):643–7. doi: 10.1097/00003226-200210000-00002. [DOI] [PubMed] [Google Scholar]
  • 22.Bharathi MJ, Ramakrishnan R, Meenakshi R, Padmavathy S, Shivakumar C, Srinivasan M. Microbial keratitis in South India: influence of risk factors, climate, and geographical variation. Ophthalmic Epidemiol. 2007;14(2):61–9. doi: 10.1080/09286580601001347. [DOI] [PubMed] [Google Scholar]
  • 23.Panda A, Satpathy G, Nayak N, Kumar S, Kumar A. Demographic pattern, predisposing factors and management of ulcerative keratitis: evaluation of one thousand unilateral cases at a tertiary care centre. Clin Experiment Ophthalmol. 2007;35(1):44–50. doi: 10.1111/j.1442-9071.2007.01417.x. [DOI] [PubMed] [Google Scholar]
  • 24.Al-Shehri A, Jastaneiah S, Wagoner MD. Changing trends in the clinical course and outcome of bacterial keratitis at King Khaled Eye Specialist Hospital. Int Ophthalmol. 2008 Apr 3; doi: 10.1007/s10792-008-9206-6. Epub ahead of print. [DOI] [PubMed] [Google Scholar]
  • 25.Al-Shakarchi F. Initial therapy for suppurative microbial keratitis in Iraq. Br J Ophthalmol. 2007 Dec;91(12):1583–7. doi: 10.1136/bjo.2007.123208. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 26.Fong CF, Tseng CH, Hu FR, Wang IJ, Chen WL, Hou YC. Clinical characteristics of microbial keratitis in a university hospital in Taiwan. Am J Ophthalmol. 2004;137(2):329–36. doi: 10.1016/j.ajo.2003.09.001. [DOI] [PubMed] [Google Scholar]
  • 27.Wang AG, Wu CC, Liu JH. Bacterial corneal ulcer: a multivariate study. Ophthalmologica. 1998;212(2):126–32. doi: 10.1159/000027291. [DOI] [PubMed] [Google Scholar]
  • 28.Wong TY, Ng TP, Fong KS, Tan DT. Risk factors and clinical outcomes between fungal and bacterial keratitis: a comparative study. CLAO J. 1997;23(4):275–81. [PubMed] [Google Scholar]
  • 29.Tan DT, Lee CP, Lim AS. Corneal ulcers in two institutions in Singapore: analysis of causative factors, organisms and antibiotic resistance. Ann Acad Med Singapore. 1995;24(6):823–9. [PubMed] [Google Scholar]
  • 30.Hall RC, McKellar MJ. Bacterial keratitis in Christchurch, New Zealand, 1997-2001. Clin Experiment Ophthalmol. 2004;32(5):478–81. doi: 10.1111/j.1442-9071.2004.00867.x. [DOI] [PubMed] [Google Scholar]
  • 31.Cheung J, Slomovic AR. Microbial etiology and predisposing factors among patients hospitalized for corneal ulceration. Can J Ophthalmol. 1995;30(5):251–5. [PubMed] [Google Scholar]
  • 32.Alexandrakis G, Alfonso EC, Miller D. Shifting trends in bacterial keratitis in south Florida and emerging resistance to fluoroquinolones. Ophthalmology. 2000;107(8):1497–502. doi: 10.1016/s0161-6420(00)00179-2. [DOI] [PubMed] [Google Scholar]
  • 33.Goldstein MH, Kowalski RP, Gordon YJ. Emerging fluoroquinolone resistance in bacterial keratitis: a 5-year review. Ophthalmology. 1999;106(7):1313–8. [PubMed] [Google Scholar]
  • 34.Pachigolla G, Blomquist P, Cavanagh HD. Microbial keratitis pathogens and antibiotic susceptibilities: a 5-year review of cases at an urban county hospital in north Texas. Eye Contact Lens. 2007;33(1):45–9. doi: 10.1097/01.icl.0000234002.88643.d0. [DOI] [PubMed] [Google Scholar]
  • 35.Yeh DL, Stinnett SS, Afshari NA. Analysis of bacterial cultures in infectious keratitis, 1997 to 2004. Am J Ophthalmol. 2006;142(6):1066–8. doi: 10.1016/j.ajo.2006.06.056. [DOI] [PubMed] [Google Scholar]
  • 36.Schaefer F, Bruttin O, Zografos L, Guex-Crosier Y. Bacterial keratitis: a prospective clinical and microbiological study. Br J Ophthalmol. 2001;85(7):842–7. doi: 10.1136/bjo.85.7.842. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 37.Yilmaz S, Ozturk I, Maden A. Microbial keratitis in West Anatolia, Turkey: a retrospective review. Int Ophthalmol. 2007;27(4):261–8. doi: 10.1007/s10792-007-9069-2. [DOI] [PubMed] [Google Scholar]
  • 38.van der Meulen IJ, van Rooij J, Nieuwendaal CP, Van Cleijnenbreugel H, Geerards AJ, Remeijer L. Age-related risk factors, culture outcomes, and prognosis in patients admitted with infectious keratitis to two Dutch tertiary referral centers. Cornea. 2008 Jun;27(5):539–44. doi: 10.1097/ICO.0b013e318165b200. [DOI] [PubMed] [Google Scholar]
  • 39.Cohen EJ, Fulton JC, Hoffman CJ, Rapuano CJ, Laibson PR. Trends in contact lens-associated corneal ulcers. Cornea. 1996;15(6):566–70. [PubMed] [Google Scholar]
  • 40.Jeng BH, McLeod SD. Microbial keratitis. Br J Ophthalmol. 2003;87(7):805–6. doi: 10.1136/bjo.87.7.805. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 41.Varaprasathan G, Miller K, Lietman T, Whitcher JP, Cevallos V, Okumoto M, Margolis TP, Yinghui M, Cunningham ET., Jr. Trends in the etiology of infectious corneal ulcers at the F. I. Proctor Foundation. Cornea. 2004;23(4):360–4. doi: 10.1097/00003226-200405000-00009. [DOI] [PubMed] [Google Scholar]
  • 42.Sun X, Deng S, Li R, Wang Z, Luo S, Jin X, Zhang W. Distribution and shifting trends of bacterial keratitis in north China (1989-98) Br J Ophthalmol. 2004;88(2):165–6. doi: 10.1136/bjo.2002.011205. [DOI] [PMC free article] [PubMed] [Google Scholar]

RESOURCES