Antibiotic Susceptibility and Biofilm Formation of Bacterial and Fungal Isolates from Infected Eyes of Individuals Resident in Enugu and Ebonyi States

Abstract

Bacteria and fungi are the major causes of ocular infections which may sometimes lead to loss of vision. The emergence of antimicrobial resistant bacteria and fungi and their ability to form biofilms increase the risk of treatment failure with potentially serious consequences. The aim of this study was to isolate and identify bacterial and fungal isolates causing external ocular infections in individuals resident in Enugu and Ebonyi states, to check their antibiotic susceptibility profile and ability to form biofilms on catheter discs. Corneal and lid margin samples in addition to conjuctival scrapings were collected and plated on blood, nutrient, MaCconkey, Eosin methylene blue and Saboraud dextrose agar respectively. Relevant biochemical tests were also performed on all distinct colonies. Overall, 133 eye infected cases, consisting of 23 blepharitis, 97 conjunctivitis and 13 keratitis cases were sampled. A total of 113 bacterial and 9 fungal isolates were recovered. Out of these, Staphylococcus aureus (36.1%) was the most predominant species followed by Pseudomonas aeruginosa (31.9%), Escherichia coli (13.9%) and Bacillus cereus (10.7 %). Aspergillus fumigatus (7.4 %) was the only fungal species recovered from the samples. Bacterial isolates varied in the clinical pictures especially in conjunctivitis cases (P˂0.05). The type of bacteria isolate(s) recovered and their clinical features did not vary according to age or sex of the patients (P< 0.05). Multi-drug resistance was observed in 33.3 % of the bacterial isolates. These isolates were subsequently tested for their ability to form biofilms. Aspergillus fumigates isolates were resistant to all antifungal agents tested. Based on the classification categories, results of the biofilm formation assay indicates that of the 14 P. aeruginosa isolates examined, 8 (57.1%) were non-adherent, 2 (14.3%) were weakly while 4 (28.6%) were moderately adherent. On the other hand, all the S. aureus (n = 11) isolates were classified as non-adherent. Significantly (P<0.05) more biofilms were produced by P. aeruginosa isolates compared to S. aureus isolates. Gram positive isolates (S. aureus) were more susceptible to gentamicin (MIC ≤ 4µg/ml, MBC ≥ 16µg/ml), levofloxacin and streptomycin while Gram negative isolates were more susceptible to ciprofloxacin, perfloxacin and ofloxacin. Specifically, 31 out of 39 (79.49 %) P. aeruginosa isolates were susceptible to ciprofloxacin (MIC ≤ 1µg/ml, MBC ≥ 32µg/ml) while the E. coli isolates, 16 of 17 (94.12 %) were sensitive to gentamicin (MIC ≤ 2 µg/ml, MBC ≥ 16µg/ml). The study recommends them to be available as ophthalmic suspensions to be dispensed by qualified practitioners.