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Elizabeth Shen, Fung-Rong Hu; Association of Type III Secretion System, Serotype, and Antibiotic Susceptibility of P. aeruginosa from Ocular Isolates. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2885. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the association between serotypes, antibiotic susceptibility, and the Type III secretion system (T3SS) genotype among ocular isolates of P. aeruginosa.
Clinical ocular isolates of P. aeruginosa collected from 2001-2011 were serotyped and analyzed with multiplex PCR for exoS, exoU, and exoT genes. Minimum inhibitory concentrations (MIC) were determined using agar dilutions containing gentamicin, amikacin, ceftazidime, piperacillin, ciprofloxacin, gatifloxacin, and moxifloxacin. The Fisher Exact Test was used to compare the antibiotic susceptibility between different serotypes and genotypes of P. aeruginosa.
Among a total of 119 ocular isolates collected, 37 isolates were from contact lens-related microbial keratitis (CLMK) and 48 were from non-CLMK. Genotype distribution found 62.2% of CLMK strains were cytotoxic (expressing exoU) while only 18.8% of non-CLMK strains were cytotoxic (P<0.01). Among CLMK isolates, serotypes 11(51%), 2(16%), and 6(11%) were most commonly found. Serotypes 2(40%), 11(23%),6(15%) were more prevalent in non-CLMK isolates. Among the antibiotics tested, 13% of the invasive strains were resistant to gentamicin and next highest was to moxifloxacin at 10%. Cytotoxic strains comparatively had lower resistance rate to all the antibiotics tested compared to invasive strains although not reaching statically significant difference. Invasive strains with serotype 2 from CLMK isolates had 50% sensitivity to fluroquinolones.There were 5 multiple drug resistant (MDR) strains: 2 of cytotoxic genotype and 3 of invasive genotype.
Contrary to previously reports, our cytotoxic strains did not show a statistical significant increase in antibiotic resistance compared to invasive strains. Invasive strains with serotype 2, in particular, showed a higher resistance to fluroquinolone antibiotics. Clinician should be aware of increased fluroquinolone resistance especially among contact lens associated corneal infections.
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