Clinical aspects and prognosis of polymicrobial keratitis caused by different microbial combinations: a retrospective comparative case study

Purpose The purpose of this study is to compare the predisposing factors, clinical findings, treatment results, and prognosis for polymicrobial keratitis. Methods In this retrospective comparative case study, we identified the cases of polymicrobial keratitis from the microbiological records ( n = 649) at Balcalı Hospital, Çukurova University (Adana, Turkey; October 2010–2018). We included all the cases of infectious keratitis with two different types of microbial agents and grouped them as follows: group 1 ( n = 25), bacterium–fungus coexistence; group 2 ( n = 12), herpes simplex virus (HSV) or Acanthamoeba with bacterial infection; and group 3 ( n = 7), HSV or Acanthamoeba with fungal infection. We compared the clinical and microbiological characteristics, and treatment outcomes among the groups. Results In our study, we found that 44 infectious keratitis cases (6.7%) were of polymicrobial nature. The mean follow-up period was 11.4 ± 17.8 months. In total, 17 different bacteria along with 3 different fungi, HSV, and Acanthamoeba were isolated. The most common bacterium was Staphylococcus epidermidis (25%). Most of the fungal pathogens were filamentous. Patients with initial treatment failure and requiring surgical intervention had larger infiltrates ( p = 0.023, p = 0.003, respectively) than other patients. Older age was associated with delayed recovery and poor visual prognosis. Conclusions Bacterial–fungus coexistence is the most common combination among patients, but other combinations should also be considered for suspected polymicrobial etiology. The corneal infiltrate size may be an important indicator of the course of disease and response to treatment. A closer and longer follow-up period should be planned for older patients.