FIRT CASE SERIES OF POST-OPERATIVE OCULAR INFECTION DUE TO STREPTOCOCCUS DYSGALACTIAE SUBSP. EQUISIMILIS IN HUMANS

Clinical infection due to Streptococcus dysgalactiae ssp. equisimilis (S. equisimilis), including primary bacteraemia, pneumonia, endocarditis, arthritis, and streptococcal toxic shock syndrome are increasing; however, there has hitherto been only one report of ocular infection. In the present report, infection due to S. equisimilis is described in three immunocompetent patients after ocular surgery and in one theatre nurse. The three patients had a history of uncomplicated small incision cataract surgery with posterior chamber intraocular lens implantation. They developed pain and reduced vision in the operated eye 48 hours after surgery. On examination the affected eyes revealed dense peripheral corneal infiltrates with exudates in the anterior chamber. Gram-stained smears of vitreous fluid samples revealed numerous Gram-positive cocci in pairs and short chains, culture of these samples grew beta-haemolytic streptococci provisionally identified as Streptococcus dysgalactiae ssp. equisimilis by biochemical methods. The identification was confirmed by PCR for a 16S rRNA sequence specific to the species S. dysgalactiae and for a sequence of the streptokinase precursor gene specific to human isolates of the subspecies equisimilis. Intravitreal cefazolin and amikacin along with topical ofloxacin and tobramycin for a few days resulted in resolution of infection in the patients. The organism was also isolated from a throat swab sample collected from a 35-year-old healthy nurse who had assisted at the three surgeries. The nurse did not give a history of systemic infection and had no signs of upper respiratory tract infection or other diseases. This is the first case series of postoperative ocular infection due to S. equisimilis. The infection may have been transmitted during surgery or the healthy carrier (theatre nurse) may also have transmitted the infection. Epidemiology of this organism is probably undervaluated and antibiotic treatment without bacterial identification is often done. Bacterial culture and identification by PCR followed by antimicrobial sensitivity testing are recommended in order to better investigate the spread and pathogenic potential of S. equisimilis and to evaluate the risk of nosocomial infections due to asymptomatic carriers.