Clinical aspects and prognosis of mixed microbial (bacterial and fungal) keratitis

Purpose: To investigate the predisposing factors, clinical presentations, treatment results, and prognosis of keratitis caused by mixed infectious agents (bacteria and fungi). Methods: This is a retrospective study of cases with mixed bacterial and fungal keratitis, presented between January 2000 and December 2007 at a tertiary referral hospital. The study was performed to identify and analyze its risk factors, causative microbial organisms, clinical features, and therapeutic outcomes. Results: Thirty-three cases of mixed bacterial and fungal keratitis in 33 patients were identified. Twenty-one cases (64%) were men, and the mean age was 64.3 ± 10.3 years. The average follow-up time was 7.2 ± 6.6 months. The most common predisposing factor for mixed keratitis was a history of ocular trauma (46%), followed by ocular surface diseases (27%). The mean pretreatment infiltration size was 11.7 ± 12.7 mm. The most common causative organisms were Staphylococcus epidermidis and Fusarium species. Seventeen cases (52%) underwent various surgical interventions: evisceration in 7 eyes (21%), penetrating keratoplasty in 5 eyes (15%), amniotic membrane transplantation in 5 eyes (15%), and so on. Seventeen cases (52%) were included in the initial treatment failure group. The significant risk factor for initial treatment failure was a large ulcer size (size over 15 mm) (P = 0.031). Conclusions: The most common risk factor for mixed bacterial and fungal keratitis was ocular trauma, and the most common combination was Staphylococcus epidermidis and Fusarium species. Usually, patients with mixed bacterial and fungal keratitis have poor prognosis. Thus, when the infectious keratitis is running an atypical course or found unresponsive to the initial medical treatment, the possibility of a mixed infection by bacterial and fungal organisms should be considered.