The intraphagocytic killing of Staphylococcus aureus, Streptococcus pyogenes, and Corynebacterium group D2 by ciprofloxacin (0.1, 1 and 5 mg/L) within human neutrophils was determined. The organisms showed different susceptibility to neutrophil killing mechanisms. The neutrophils with intact and impaired (by phenylbutazone treatment) O2-dependent killing mechanisms were studied. The minimum concentrations of ciprofloxacin to kill 90% of phagocytosed bacteria within untreated neutrophils after 2 h were 1 mg/L for S. aureus and Corynebacterium group D2, and 0.1 mg/L for S. pyogenes. In contrast, exposure for 3 h was required to achieve similar cidal effects within phenylbutazone treated neutrophils. Synergic interaction between ciprofloxacin and the O2-dependent mechanisms of phagocytes was found. The reactive oxygen metabolites produced in the respiratory burst did not affect the intraphagocytic activity of ciprofloxacin. Phenylbutazone treatment of phagocytes would be a good experimental model to study intraphagocytic killing by drugs in situations where the oxidative mechanisms of neutrophils are impaired (for example AIDS and chronic granulomatous disease).

Purpose To demonstrate antibiotic susceptibility and genomic virulence factor profiles of Pseudomonas aeruginosa isolates from patients with culture-confirmed endophthalmitis. Methods Clinical isolates from patients diagnosed with pseudomonas endophthalmitis were included. Laboratory antibiotic susceptibility testing and whole genome sequencing was performed on all isolates. Results In the current study, 8 patients had vitreous culture-confirmed endophthalmitis due to P. aeruginosa. All isolates were multi-drug resistant but sensitive to ceftazidime and each fluoroquinolone tested. Whole genome sequencing revealed a total of 179 unique genes. The most common type of virulence genes included those involved in adherence and the secretion system. Seven of 8 (88%) isolates were of the cytoinvasive phenotype (exoST) and no isolates contained exoU. Conclusions P. aeruginosa associated endophthalmitis is often multi-drug resistant and demonstrates a variety of virulence factors with those involved in adherence and the secretion system being the most common.