Bacteriology of external ocular infections in Aba, South Eastern Nigeria

Bacteria are microbial agents that frequently cause infections of the eye and possible loss of vision.

The common isolates were studied in 298 bacterial infections of the anterior eye, consisting of 35 blepharitis, 208 conjunctivitis and 55 keratitis. Isolates were cultured in blood agar and chocolate agar. Each strain's susceptibility to the antibiotics was determined using a standard table of antibiotic susceptibility.

In decreasing order of frequency, the implicated bacteria were Staphylococcus aureus 80 (23.7 per cent), Staphylococcus albus 65 (19.2 per cent), Pseudomonas aeruginosa 34 (10.1 per cent), Streptococcus pneumoniae 29 (8.6 per cent), Haemophilus influenzae 26 (7.7 per cent), Streptococcus pyogene 20 (6.2 per cent), Klebsiella pneumoniae 18 (6.2 per cent), Escherichia coli 15 (4.4 per cent), Neisseria gonorrhoeae 13 (3.9 per cent), Streptococcus viridans 11 (3.5 per cent), Moraxella catarrhalis 10 (3.0 per cent), Streptococcus faecalis 5 (1.5 per cent), Proteus mirabilis 5 (1.5 per cent) and Neisseria meningitides 1 (0.3 per cent). Bacteria were isolated most frequently from infections of the conjunctiva (222, 66.7 per cent), then the cornea (65, 20.1 per cent) and least from the eyelids (44, 13.2 per cent). Bacterial isolates varied in their clinical features (p < 0.01). The age distribution showed isolations of 77 (23.2 per cent) and 79 (23.7 per cent) in the age groups of newborn to under three years and three to under 12 years, respectively. This was comparable to 66 (19.8 per cent) for the 12 to under 18 years, 61 (18.3 per cent) for the 18 to under 40 years age group and 50 (15 per cent) for those 40 years and above. Bacterial isolates had no predilection for the age of patients (p < 0.95). Conjunctivitis was diagnosed more in children, 60 (28.8 per cent) in the newborn to under three years and 53 (25.5 per cent) in the three to under 12 years age groups. Blepharitis was diagnosed most frequently (15, 42.8 per cent) in adolescents 12 to under 18 years, while keratitis was more in adults (20, 36.4 per cent) in the 18 to under 40 years and (15, 27.3 per cent) in the 40 years and above. Diagnosis varied among age groups but there was no relationship between sex and diagnosis (p < 0.75). Klebsiella pneumoniae was the most resistant to all the anti-bacterial preparations. The bacterial isolates were more susceptible to the second generation quinolones than the first.

The study recommends that quinolones be available as ophthalmic preparations to be prescribed by the qualified practitioners to avoid development of resistance from indiscriminate use.