Purpose: To identify bacterial agents in the aqueous humor of patients with postoperative endophthalmitis using eubacterial polymerase chain reaction (PCR) and conventional culture.
Setting: University Hospital of Lyon E. Herriot, Lyon, France.
Methods: Broad-range eubacterial PCR amplification followed by direct sequencing was used to identify microbial pathogens in ocular samples from 30 patients with acute or delayed-onset endophthalmitis, mainly after cataract surgery. Ocular samples included aqueous humor collected before the first intravitreal injection of antibiotics and vitreous samples collected at the time of the therapeutic pars plana vitrectomy.
Results: Cultures were positive in 32% of cases and PCR in 61% of cases with aqueous humor samples. When associated, culture and PCR of aqueous humor samples allowed for a microbiological diagnosis in 71% of cases. Microorganisms cultured by conventional techniques matched those identified by PCR. When applied on vitreous pretreated with intravitreal antibiotics, PCR increased the identification rate from 18% to 62%.
Conclusions: Polymerase chain reaction assay of initial aqueous humor samples contributed to the diagnosis of endophthalmitis in 30% of cases. Previous use of intravitreal antibiotics did not seem to affect the ability to PCR-amplify DNA in the short term. Polymerase chain reaction-based technology was a useful adjunct to conventional culture because when used with aqueous humor samples only, the association of both techniques allowed for a microbiological diagnosis in 71% of cases of postoperative acute and delayed-onset endophthalmitis.