Bacterial susceptibility to topical antimicrobials and clinical outcome in bacterial keratitis.
OBJECTIVE
To investigate the relationship between the susceptibility of bacteria to topical antimicrobials and clinical outcome in microbial keratitis.


METHODS
Clinical outcome data were collected from patients with microbial keratitis from whom a bacterium had been isolated during the period 2003 to 2006. The minimum inhibitory concentration (MIC) was determined for the isolates against 10 antimicrobials. The determinants of the primary clinical outcome, the ratio of healing time (closure of epithelial defect) to ulcer size (HT/UA), was analyzed in a general linear model.


RESULTS
Complete clinical outcome and MIC data were available for 421 patients. Sixteen (4%) patients required enucleation and 23 (5%) surgical treatment; in 382 (91%) the ulcer healed with intensive topical antimicrobial therapy. There were significant correlations between HT/UA and organism type (P = 0.001), nearest distance of the ulcer to the limbus (0.02), and MIC of the first antimicrobial used or lowest MIC of combined therapy (P = 0.006). In a model including patients who received monotherapy with a fluoroquinolone who had no subsequent change in their treatment and whose ulcers healed without surgical intervention, there were significant linear associations between clinical outcome and MIC for Pseudomonas spp. (P = 0.047), Staphylococcus aureus (P = 0.04), and Enterobacteriaceae (P = 0.045), but not for Streptococcus spp. (P = 0.85) and coagulase-negative staphylococci (CNS) (P = 0.88).


CONCLUSIONS
With fluoroquinolone monotherapy, there was significant association between the MIC of the antimicrobial prescribed and the clinical outcome with all bacteria except CNS and Streptococcus spp. The approach used in this study, if used prospectively, could allow topical breakpoint susceptibility concentrations to be determined for individual antimicrobial and bacterial combinations.
Kaye
Stephen
S
Department of Ophthalmology, Royal Liverpool University Hospital, Liverpool, United Kingdom. s.b.kaye@liverpool.ac.uk
Tuft
Stephen
S
Neal
Timothy
T
Tole
Derek
D
Leeming
John
J
Figueiredo
Francisco
F
Armstrong
Malcolm
M
McDonnell
Peter
P
Tullo
Andrew
A
Parry
Christopher
C
D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D000891:Anti-Infective Agents, Local / Q000627:therapeutic use*; D001419:Bacteria / Q000187:drug effects* / Q000302:isolation & purification; D003320:Corneal Ulcer / Q000188:drug therapy / Q000382:microbiology*; D004359:Drug Therapy, Combination; D015818:Eye Infections, Bacterial / Q000188:drug therapy / Q000382:microbiology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D012307:Risk Factors; D016896:Treatment Outcome; D014945:Wound Healing
D000900:Anti-Bacterial Agents; D000891:Anti-Infective Agents, Local