¡¡¡¡Microbiology Results

¡¡¡¡Gram stain  Of the 87 eyes, 69 (79%) had corneal scrapings done. 52 slides (75%) were reported as negative. The positive results are shown in Table 2. Gram negative bacilli were seen in 13 cases (19%).

¡¡¡¡Culture and sensitivity  Positive growth of organism was seen in 51 cases (74%); 16 cases (23%) being polymicrobial and 35 cases (51%) involving single microbes. There was negative growth in 18 cultures (26%).

¡¡¡¡Nineteen types of organisms were isolated from the culture plates, as listed in Table 3. The most common organism detected was Pseudomonas aeruginosa, seen in 40 cultures (58%). Aspergillus sp. was the most frequently reported fungal pathogen. There were more gram negative organisms isolated (68%) than gram positive bacteria.

¡¡¡¡Treatment  In this study, 36 eyes (41%) were started on intravenous antibiotics, 17 eyes (20%) had oral antibiotics alone and 34 eyes (39%) were not started on any systemic antibiotics. All but 1 (2%) of Pseudomonas aeruginosa cultures were sensitive to gentamicin. One case was resistant to chloramphenicol. There was one culture of gentamicinª²resistant Stenotrophomonas maltophilia and one of methicillinª²resistant Staphylococcus epidermidis.

¡¡¡¡Gentamicin (69%) was the commonest intravenous antibiotic given, followed by cefuroxime (67%) and ciprofloxacin (31%). Intravenous ceftazidime was used in 14% of cases. The most commonly used systemic antifungal was oral ketoconazole (4 cases).

¡¡¡¡All eyes were started on topical treatment of variable combination. The fluoroquinolones ciprofloxacin 3g/L and lomefloxacin 3g/L were used in 68 eyes (78%) as they have broad spectrum coverage, are well tolerated and are widely available commercially. Cefuroxime 50g/L was used in 21 eyes (24%). The fortified gentamicin 10g/L formulation was used in 65 eyes (75%), more than the weaker gentamicin 3g/L in 8 eyes (9%). Topical antifungals commonly used were amphotericin B 5g/L and itraconazole. Acyclovir ointment 30g/L was used in cases suspected of herpetic origin, in combination with antibiotic coverage.

¡¡¡¡Outcome

¡¡¡¡Corneal opacity  There were 75 eyes (88%) which eventually developed corneal opacity after ulcer healing. Four cases had vascularisation, of which one developed uncontrolled secondary glaucoma and needed trabeculectomy.

¡¡¡¡Severe complications  Endophthalmitis with impending perforation was seen in one case. Pseudomonas aeruginosa was isolated from it and treatment was with intravitreal amikacin and ceftazidime. It eventually healed with scarring. 2 other cases of endophthalmitis eventually required evisceration. Of these, 1 patient had a chronic psychiatric disorder and also had bilateral below knee amputations for gangrene. The other had rubeotic glaucoma in the same eye, as well as hypertension

¡¡¡¡Table 2  Distribution of gram stain results

¡¡¡¡Gram stain resultFrequency%Gram negative cocci23Gram negative bacilli1319Gram positive bacilli11.5Gram positive cocci11.5Negative5275Not done1821Total87100
Table 3  Frequency of organism cultured

¡¡¡¡MicroorganismsFrequencyGram positive bacteria    Staphylococcus coagulase negative3    Streptococcus viridans2    Staphylococcus epidermidis1Gram negative bacteria    Pseudomonas aeruginosa40    Enterobacter sp.4    Stenotrophomonas maltophilia4    Alcaligenes sp.3    Acinetobacter baumanii3    Serratia marcescan2    Klebsiella sp.1    Klebsiella pneumoniae1    Aeromonas sp.1    Acinetobacter sp.1    Citrobacter sp.1    Flavobacterium meningosepticum1    Mycobacterium sp.1Fungi    Aspergillus sp.3    Curvularia lunata1    Paecilomyces lilaicinus1and chronic osteomyelitis of the right foot. Staphylococcus coagulase negative sensitive to methicillin was isolated from the former while the latter had a negative culture.

¡¡¡¡Perforation occurred in 4 eyes; one eye had a Gunderson conjunctival flap done while 2 others healed with cyanoacrylate tissue adhesive and bandage contact lens application. The final one was infected with the rare Paecilomyces lilaicinus which proved resistant to our treatment. The patient opted for alternative treatment at another centre but eventually developed perforation and had to have an enucleation done. He had SLE and AIHA, and was on systemic steroids.

¡¡¡¡Outcome and risk factors  The rate for developing endophthalmitis was 8% while perforation leading to endophthalmitis occurred in 3.5%. The rate of evisceration and enucleation was 3.5%. Statistical analysis showed that the risk of perforation and endophthalmitis was significantly higher in eyes with previous ocular surgery (P<0.05) and ocular surface disease (P<0.01) but not in the contact lens wear, trauma or glaucoma groups. There was also no significant association with diabetes or hypertension.

¡¡¡¡DISCUSSION

¡¡¡¡Demographics and Risk Factors  The slight female preponderance (1.2¡Ã1) in this series differs from a few other studies where there were more males affected[4,5]. Considering the predominant predisposing factor in this study population was contact lens wear, the probable reason for the female preponderance was due to the popular use of contact lenses by this gender. Previously, most cases of microbial keratitis were associated with ocular trauma or ocular surface disease but the widespread use of contact lenses has changed the order of importance of these risk factors[6]. Contact lens wear is now the major cause of ulcerative keratitis in developed countries where there is a significant number of contact lens wearers. However, in the Malaysian state of Kelantan, where a significant part of the population is involved in the agriculture industry, trauma/ foreign body entry (52%) was the major risk factor associated with corneal infection. Only 4 patients (2%) were contact lens wearers[5].

¡¡¡¡Older average ages were seen in patients who had preª²existing ocular surface disease (48.8 years), previous surgery (62.3 years) and glaucoma (71.6 years). This was also seen in the cases with diabetes mellitus (65.3 years) and hypertension (64.3 years).

¡¡¡¡Clinical Features  Visual prognosis after bacterial keratitis has been reported to be affected by presence of associated risk factors, locality, anterior chamber reaction and depth of the ulcer[7]. In this study, best corrected vision 2 months after discharge was correlated with site and size of the ulcer. Ocular surface disease, previous surgery and glaucoma were also associated with poorer outcome. These factors appear to have an added destructive effect to the epithelial disruption and stromal derangement caused by the infection.

¡¡¡¡Microbiological Profile  This study showed a good yield for culture and sensitivity inoculations, comparable to other published studies which reported incidences of 27ª²67% for positive gram stains and 36ª²76% for positive culture results[8]. Sensitivity testing has a place in following trends in antibiotic resistance that can guide the selection of the appropriate antibiotics for specific organisms.

¡¡¡¡Pseudomonas aeruginosa was the most frequently isolated bacteria (57%) in the cultures and it was also the main causative organism seen in the 3 main ocular risk factor groups. Contact lens wear (31 cases) contributed to the highest proportion of Pseudomonas ulcers. It has been suggested that this is due to a combination of minor trauma followed by corneal contamination with this soil and water based organism[9]. The dominance of pseudomonas keratitis has also been shown in other studies done in this region[5,9].

¡¡¡¡Aspergillus sp was the most frequently isolated fungi in this series. It is the most frequently reported fungal pathogen isolated in the tropics, together with Fusarium sp.[10]. Differences in the incidence of fungi are known to exist with respect to geographic locations, thus selecting antimycotics should take this into account. In temperate climates, Candida is most frequent, followed by Aspergillus.

¡¡¡¡It is interesting that only one case each of Pseudomonas aeruginosa and Stenotrophomonas maltophilia were resistant to gentamicin, which is the first line antibiotic for gram negative ocular infections used locally. Although treatment outcomes with fluoroquinolone monotherapy compare favourably with conventional combined therapy of fortified antibiotics[11], it appears that gentamicin may remain effective as the initial antibiotic of choice for gram negative cover in our local context.

¡¡¡¡Treatment and Outcome  In this study, the most commonly used eyedrop was of the fluoroquinolone group (78%) followed by fortified gentamicin (75%) and then cefuroxime 5% (24%).

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