Trends in resistance to ciprofloxacin, cefazolin, and gentamicin in the treatment of bacterial keratitis.
OBJECTIVE
The aim of this study was to evaluate the microbial profile, resistance patterns, and antibiotic sensitivity of bacterial keratitis to three commonly used ocular antibiotics.


METHODS
All cases of bacterial keratitis referred to the Massachusetts Eye and Ear Infirmary Microbiology Laboratory from two consecutive annual 10-month periods were reviewed. The bacterial profile and resistance to ciprofloxacin, cefazolin, and gentamicin was evaluated within the two intervals.


RESULTS
Of the 485 cultures analyzed, 66.4% (322) were positive for bacterial isolates. Of these, 19.2% were polymicrobial, 87.5% were gram-positive, and 12.5% were gram-negative. The most prevalent isolate was coagulase-negative Staphylococcus (45.5%), followed by S. aureus (15.2%). The resistance patterns for gram-positive bacteria for ciprofloxacin for the first versus second time interval were 12% and 22% (P = 0.04) respectively, for cefazolin 13% and 23% (P = 0.04), and for gentamicin 4% and 7% (P = 0.36). The resistance patterns for gram-negative bacteria for ciprofloxacin, cefazolin, and gentamicin were not significantly different in the two tested time periods (all P > 0.05).


CONCLUSIONS
There was increased resistance of gram-positive organisms to ciprofloxacin and cefazolin, but not gentamicin, in the two examined time periods. Increased resistance to these commonly used antibiotics emphasizes the need for close follow-up after initial empiric treatment, and maintaining a low threshold for selecting alternative therapy.
Afshari
Natalie A
NA
Duke University Eye Center, Duke University Medical Center, Durham, NC 27710, USA. afsha003@duke.edu
Ma
Joseph J K
JJ
Duncan
Scott M
SM
Pineda
Roberto
R
Starr
Christopher E
CE
Decroos
Francis Char
FC
Johnson
Carl S
CS
Adelman
Ron A
RA
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002437:Cefazolin / Q000494:pharmacology; D002939:Ciprofloxacin / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D015818:Eye Infections, Bacterial / Q000188:drug therapy*; D005839:Gentamicins / Q000494:pharmacology; D016905:Gram-Negative Bacterial Infections / Q000188:drug therapy; D016908:Gram-Positive Bacterial Infections / Q000188:drug therapy; D006801:Humans; D066298:In Vitro Techniques; D007634:Keratitis / Q000188:drug therapy*; D008826:Microbial Sensitivity Tests; D012189:Retrospective Studies
D000900:Anti-Bacterial Agents; D005839:Gentamicins; D002939:Ciprofloxacin; D002437:Cefazolin