Pseudomonas aeruginosa induced ocular infection. A histological comparison of two bacterial strains of different virulence.

The purpose of this study was to compare and characterize histopathologically the virulence of two bacterial strains in a naturally susceptible animal host. One of the strains Pseudomonas aeruginosa ATCC 19660, routinely used in this laboratory, produces endopthalmitis and phthisis bulbi in C57BL/6 mice within 3-4 weeks. The other bacterial strain, a clinical isolate from a 70-year-old patient with Pseudomonas corneal infection was found to be less virulent in the patient and thus was examined for virulence in the susceptible mouse model. The strain also proved to be less virulent in the normally susceptible mouse when compared with ATCC 19660. In general, when comparing the histopathological response of the mice to the two bacterial strains, it was found that in contrast to ATCC 19660, fewer polymorphonuclear neutrophils migrated into the cornea at 24-72 h, endothelial and epithelial necrosis was delayed, few free bacteria were observed in the cornea and animals recovered corneal clarity by 21-25 days following infection.