Pseudomonas aeruginosa in vitro corneal isolate sensitivity to ofloxacin, ciprofloxacin, and trovafloxacin: a comparative study

In vitro fluoroquinolone susceptibility ofPseudomonas aeruginosaisolates from dogs with ulcerative keratitis

OBJECTIVE

To determine the in vitro fluoroquinolone susceptibility profiles of Pseudomonas aeruginosa isolates from dogs with ulcerative keratitis. Animals-27 dogs with P. aeruginosa-associated ulcerative keratitis.

PROCEDURES

P. aeruginosa isolates from dogs with ulcerative keratitis were collected during a 3-year period. Isolates were tested by use of the disk diffusion method for their susceptibility to 7 fluoroquinolones that are available as commercial ophthalmic preparations. The antimicrobials included second- (ciprofloxacin, ofloxacin, norfloxacin, and lomefloxacin), third- (levofloxacin), and fourth-generation (gatifloxacin and moxifloxacin) fluoroquinolones. Isolates were designated as susceptible, intermediate, or resistant to the various antimicrobials. The percentage of susceptible isolates was compared among individual fluoroquinolones and among fluoroquinolone generations.

RESULTS

None of the dogs had received topical or systemic fluoroquinolone treatment prior to referral. Twenty-seven P. aeruginosa isolates were collected during the study period. In vitro, bacterial resistance to the tested fluoroquinolones was infrequently identified (24/ 27 isolates were susceptible to all fluoroquinolones evaluated); susceptibility percentages ranged from 88.9% to 100% for individual antimicrobials. There were no significant differences among isolate susceptibilities to the individual antimicrobials or among generations of fluoroquinolones.

CONCLUSIONS AND CLINICAL RELEVANCE

On the basis of these in vitro data, none of the 7 evaluated fluoroquinolones (individually or collectively by generation) appeared to offer a clinically important advantage in the treatment of P. aeruginosa-associated ulcerative keratitis in dogs. Among the P. aeruginosa isolates collected from dogs with ulcerative keratitis in this study, the likelihood of susceptibility to the fluoroquinolones evaluated was high.

Infective keratitis in older patients: a 4 year review, 1998-2002

BACKGROUND/AIM

There are few clinical series in the literature of infective keratitis in the elderly, even though this age group constitutes a significant proportion of those affected by this condition. The authors aimed to determine the incidence and risk factors for infective keratitis in those over 60 years, the causative organisms, antibiotic susceptibilities, visual and tectonic outcome, and surgical intervention rate.

METHODS

A retrospective review of all patients aged 60 years and over admitted to the Sydney Eye Hospital with a diagnosis of infective keratitis, between September 1998 and December 2002.

RESULTS

190 patients were identified with a mean age of 75.5 (SD 9.6) years (range 60-101). Local risk factors were found in 93.7%, and systemic risk factors in 27.9%. Organisms were cultured in 62.8%, and 7.9% had positive herpes simplex virus (HSV) polymerase chain reaction (PCR). Perforation or severe thinning occurred in 36% overall, but in 80% with positive HSV PCR. Acute surgical intervention was required in 43.7%, with acute penetrating keratoplasty performed in 17.9%, and 8.9% required evisceration. Mean presenting visual acuity was 1.82 (SD 1.24), equivalent to 6/300, excluding 26.3% with vision of light perception (LP) or worse. Mean final visual acuity was 1.24 (SD 1.16), equivalent to 6/100, excluding 19.5% with vision of LP or worse (p<0.0005).

CONCLUSIONS

The elderly represent a distinct clinical group in the context of microbial keratitis. Predisposing factors are very common, they present with poor vision, have a high complication and surgical intervention rate, and a poor visual outcome compared to younger patients. The microbiological spectrum is similar to younger age groups, except that HSV is more common and may increase the risk of severe corneal thinning and perforation. Most bacterial isolates remain sensitive to currently available antibiotic preparations.

Comparative In Vitro Activity of Levofloxacin, Ofloxacin, and Ciprofloxacin Against Ocular Streptococcal Isolates

OBJECTIVE

To determine the in vitro efficacy of levofloxacin, ofloxacin, and ciprofloxacin against Streptococcus pneumoniae and Streptococcus viridans isolates recovered from clinical cases of keratitis and endophthalmitis.

METHODS

Streptococcal isolates recovered from keratitis and endophthalmitis cases between 1990 and 2001 were identified and extracted from the Microbiology Data Bank of the Bascom Palmer Eye Institute, Miami, FL. Comparative in vitro minimal inhibitory concentration (MIC90) susceptibility profiles for levofloxacin, ofloxacin, and ciprofloxacin against a select group (n = 65) of streptococcal isolates were documented using the E test methodology. Penicillin susceptibility profiles were also evaluated. chi 2 x 2 tables and McNemar's Paired-Sample Tests were used to established statistical significance.

RESULTS

MIC90 values for levofloxacin, ofloxacin, and ciprofloxacin against pneumococcal isolates were 1.5, 6, and 3 microg/mL. The corresponding values for the S. viridans group were 2, 8, and 24 microg/mL. Levofloxacin was 4 times more active in vitro than ofloxacin and 2 times more active in vitro than ciprofloxacin against S. pneumoniae. Levofloxacin was 4 times more active in vitro than ofloxacin and 12 times more active than ciprofloxacin for S. viridans group. Sixty-three percent of the S. pneumoniae and 57.9% of the S. viridans group isolates were intermediate or resistant to penicillin. Levofloxacin provides 100% coverage for penicillin-intermediate and penicillin-resistant isolates versus 33.8% for ofloxacin and 29.2% for ciprofloxacin.

CONCLUSION

Levofloxacin is highly active in vitro against streptococcal isolates recovered from keratitis and endophthalmitis patients, including penicillin-intermediate and penicillin-resistant strains.