Aims: To study the distribution and shifting trends of bacterial keratitis.
Methods: The data of 2220 corneal isolates from 1 January 1989 to 31 December 1998 were reviewed retrospectively.
Results: Positive culture was recovered in 490 isolates. Gram positive cocci and Gram negative bacilli represented 51% and 39.4%, respectively. Pseudomonas aeruginosa was the most common pathogen (32.2%). A gradual increase in the percentage of Gram positive cocci coupled with a decrease of Gram negative bacilli.
Conclusion:Pseudomonas aeruginosa and coaculase negative Staphylococcus were the most common pathogens in bacterial keratitis in north China.
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Keratitis caused by bacteria usually results in various corneal lesions, and even severe visual loss. In developing countries, bacterial keratitis has become the most common cause of corneal blindness.1 Based on data over 10 years (1989–1998), we carried out a detailed aetiologic analysis.
MATERIAL AND METHODS
From 1 January 1989 to 31 December 1998, bacterial cultures were carried out on 2220 cases. Culture media: blood agar plate, routine culture media, and identified culture media. Specimens were inoculated on culture media in 35°C for 24–48 hours.
Of the 2220 corneal isolates, mono-bacterial positive culture was recovered in 490 isolates (table 1). Gram positive cocci were found in 250 isolates (51.0%); most of these were coagulase negative Staphylococcus. Gram positive bacilli isolates accounted for 45 (9.2%). Gram negative bacilli isolates were found in 193 (39.4%), mainly Pseudomonas spp (see table 2).
The gradual increase in the percentage of Gram positive cocci (25% in 1991 v 70.8% in 1997, p<0.01), and decreasing trend in Gram negative bacilli (69% in 1990 v 23.4% in 1997, p<0.01), are shown in figure 1.
The percentage of Pseudomonas spp followed a trend of decrease (58.6% in 1990 v 24% in 1998, p<0.01), as shown in figure 2.
According to our study, Gram positive cocci is still the leading causative organism of bacteria keratitis, and the percentage of Gram positive cocci showed an increased trend. Pseudomonas spp accounted for 32.2% of the total corneal positive cultures, but it decreased year by year. The data from America showed that P aeruginosa accounted for 25.7% of total positive bacterial isolates.2
A study in India showed that Gram positive organisms accounted for 82.4%, while Gram negative organisms 16.1%3. Compared with that study, our data from north China have shown a lower percentage of Gram positive bacteria and a relatively higher percentage of Gram negative for ketatitis.