In this study, the majority of patients 29/50 (58%) were between 4th and 6th decade. The incidence of infectious keratitis is higher in males 27/50 (54%) than in females 23/50 (46%). Thirty-one out of 50 (62%) of cases live in rural areas. Housewives represented 38%, farmers 30%, and other jobs represented 32%. In similar findings, (Ravinder et al. 2016) found that infectious keratitis was more common in males (62%) than females (38%) more commonly observed in rural populations (65%), with higher prevalence in agricultural workers (47.5%) followed by industrial workers (23.75%), housewives (12.5%), and students (8.75%). Sedhu et al. 2017 showed that 70% of patients with infectious keratitis lived in urban areas mainly housewives (21%) followed by farmers (16.9%), laborers (13.6%), and carpenters (12.3%)
In this study, trauma was the most common predisposing factor observed in 15/50 (30%) of infectious keratitis; ocular trauma with organic material represents 9/15 (60%) and is more in male farmers living in rural areas. This is in agreement with (Ravinder et al. 2016) and (Choudhury et al. 2017) where ocular trauma was the most common predisposing factor with 46% and 69%, respectively. Also according to Basak et al. 2005 and Senthil Vadivu 2013, corneal injury with vegetable matter was the most common factor causing infectious keratitis with 59.6% and 47.817%, respectively. Ravinder et al. 2016 reported that farmers were more prone for ocular trauma with organic material. El Shabrawy et al. 2013 found history of ocular trauma to be the most important predisposing factor for fungal keratitis (63.6%). The above observations clearly show that in developing countries, agricultural workers are more prone to vegetative matter-induced ocular trauma as a major cause of infectious keratitis in rural populations more than urban populations.
While in developed countries wearing contact lense constitutes a major risk factor for infectious keratitis, according to Keay L et al. 2006, Jeng B. H. et al. 2010, and Mun et al. 2019, in our study, history of wearinf contact lens and using topical corticosteroids represented only 2/50 (4%) and 3/50 (6%), respectively.
In the present study, positive culture samples of infectious keratitis cases are 60% (30/50). Similar to our results, Marasini et al. 2016, found a positive culture rate of 57.8%. However, lower positive culture results were reported by Shoja and Manaviat 2004 and Amescua et al. 2012 with 40% and 38%, respectively. While Stefan and Nenciu 2006 and Al-Shakarchi et al. 2015 demonstrated higher results of positive corneal scraping culture samples with 86.7% and 70%, respectively.
Our study showed that fungal growth is the most prevalent pattern of growth 23/30 (77%), while bacterial growth is 7/30 (23%). This is in accordance with a study by EL Shabrawy et al. (2013) conducted in Egypt. Joshi et al. (2017) and Manikandan et al. (2019) who reported that 55%, 65%, and 98%, respectively, of culture positive cases were identified to be due to fungal causes while the remaining cases were due to bacterial causes. However, a study by Tewari et al. 2012 and Ghosh et al. 2016 reported that out of the positive isolates, 65% and 61% belonged to the bacteria, while 35% and 39% belonged to fungi, respectively.
In this study, Aspergillus spp. are being the most prevalent 21/23(91%), followed by Fusarium spp. 2/23(8%). This finding is in accordance with Al-Shakarchi 2007 and Tewari et al. 2012 who demonstrated that Aspergillus spp. was the most common isolate with 57% and 35% followed by Fusarium spp. with 27% and 22% among fungal pathogens, respectively. However, a study conducted in Egypt by EL-Shabrawy et al. 2013 revealed that the most frequent fungal pathogens were Penicillium spp. (24.2%) followed by Aspergillus fumigatus (21.2%) then Fusarium spp. (9%).
The incidence of fungal keratitis is on the rise in the densely populated continents of Asia and Africa (Ravinder et al. 2016). This can be explained by the difference in climatic conditions. A study done in the National Research Centre in Egypt to detect the association between fungal keratitis and the climatic changes concluded that the climatic conditions directly affect the frequency of fungal keratitis and that the incidence of this disease will continue to rise as long as the global warming is increasing and the greenhouse gases will continue to rise (EL Shabrawy et al. 2013). Species of Fusarium and Aspergillus are widespread in nature being important pathogens in fungal keratitis (Manikandan et al. 2019).
In the present study, the bacterial growth among positive culture cases is 7/30 (23%); 3/7 were S. aureus, 3/7 was Pseudomonas spp., and the remaining isolate was S. pneumoniae. A study conducted by AL-Yousuf, 2009 in Bahrain reported that Pseudomonas aeruginosa, Staphylococcus, and Streptococcus were the most frequent pathogens. This is near to a study by Tewari et al. 2012 and Mun et al. 2019 who reported that the most frequent bacterial isolates were S. aureus followed by Pseudomonas aeruginosa.
Proper diagnosis and treatment of bacterial keratitis are essential to achieve resolution of infection and minimize damage to the cornea. In our study, the antibiotic susceptibility pattern of the 3 isolates of S. aureus revealed (100%) susceptibility to cefoxitin (methicillin sensitive) and all quinolones (ciprofloxacin, ofloxacin, levofloxacin, gatifloxacin, and moxifloxacin). This is in accordance with Senthil Vadivu 2013 who founded 7/9 (77%) methicillin-sensitive S. aureus , with 77% sensitivity to ciprofloxacin and Mun et al. 2019 who reported 11/13(85%) methicillin-sensitive S. aureus with higher sensitivity to levofloxacin and moxifloxacin; 95.8% and 93.8%, respectively. Treatment of P. aeruginosa eye infections often becomes a challenge due to the ability of this bacterium to be resistant to antibiotics via intrinsic and acquired mechanisms (Subedi et al. 2018). In the present study, the 3 Pseudomonas isolates (100%) were susceptible to tobramycin, amikacin , ciprofloxacin, ofloxacin, levofloxacin, and gatifloxacin followed by gentamicin and polymyxin B 2/3(66.6%). This is similar to a study conducted by Marasini et al. 2016 where all Pseudomonas aeruginosa isolates were sensitive to gentamicin and ciprofloxacin. Mun et al. 2019 also found that all Pseudomonas species isolates were sensitive to amikacin and ciprofloxacin. While Cho and Lee, 2018 reported less than 10% resistance in P. aeruginosa to ciprofloxacin and gentamicin. According to SenthilVadivu, 2013, P. aeruginosa isolates showed lower sensitivity to ciprofloxacin (66%) and ofloxacin (83%).
Treatment of fungal keratitis is one of the most difficult problems encountered by ophthalmologists due to poor response to the therapy as well as the limited availability of antifungal agents. Although voriconazole and other triazoles have broad-spectrum activity against causative fungal isolates, clinically no single drug was found to be effective against fungal keratitis (Manikandan et al. 2019). In this study, antifungal susceptibility pattern of the 23 fungal isolates revealed that all isolates are 100% susceptible to ketoconazole and voriconazole. In accordance with our findings, a study conducted in Upper Egypt by Gharamah et al. 2014 showed that ketoconazole at 0.5% and 1% concentrations was effective against all fungal isolates, except for three Fusarium species tested. However, Sirisha et al. 2015 reported lower percentages of sensitivity to ketoconazole for Aspergillus fumigatus (85%), Fusarium spp. (83%), Aspergillus flavus (73%), and Aspergillus niger (50%).
A study conducted by (Saha et al. 2014) showed that voriconazole had the lowest minimal inhibitory concentration (MIC) against Aspergillus spp. and Fusarium spp., followed by amphotericin B, ketoconazole, itraconazole, and that it is still the first choice in the treatment of mould keratitis.
In the present study, susceptibility to itraconazole gave different results. Both A. fumigatus and Fusarium spp. show 100% susceptibility, while A. flavus and A. niger showed intermediate susceptibility with 21% and 75%, respectively. This finding is in partial agreement with Senthil vadivu 2013 where A. fumigatus and A. niger showed 100% susceptibility while A. flavus and Fusarium spp. showed 78% and 83%, respectively. Also a study conducted by Sirisha et al. 2015 showed that all 29 fungal isolates (Fusarium spp, A. flavus, and A.niger) were 100% susceptible to itraconazole except for A. fumigatus (85%).
In our study, 96% (22/23) are resistant to amphotericin B. However, Senthilvadivu 2013 reported in his study that A. fumigatus, Fusarium spp, A. flavus, and A. niger isolates were sensitive to Amphotericin B (70%), (66%), (64%), and (58%), respectively. Also, a study by Gharamah et al. (2014) showed that the (MIC) of amphotericin B was at 0.1% or 0.5% concentrations for most fungal species tested while there was no effect on the 3 Fusarium species. Amphotericin B was quite sensitive to genus Aspergillus and Fusarium but due to poor penetration in cornea and the requiring of high dosage, it was not used in such keratitis (Saha et al. 2014). In the present study, all isolates were resistant to fluconazole. This is in agreement with Senthil vadivu 2013, Sirisha et al. 2015, and Senthilvadivu and Stalin, 2018.