Abstract
Purpose:
Acinetobacter baumannii is an opportunistic pathogen that most frequently causes nosocomial infections. Although few clinical studies have documented A. baumannii as a causative agent of keratitis and endophthalmitis, the detailed characterization of ocular isolates remains to be determined. In this study, we assessed the antibiotic-resistant pattern, genetic relatedness and plasmid profiles of ocular isolates from South East Michigan.
Methods:
Ocular A. baumannii isolates (n=12) were taken from the clinical microbiology laboratory of Detroit Medical Center. The minimum inhibitory concentration (MIC) of various antibiotics was determined against each isolate using Micro scan. Plasmid profiling and conjugation experiments were carried out to determine the transfer of antibiotic resistant genes. PFGE was performed to determine the clonal relatedness of various isolates. RT-PCR was used to check the expression of virulence genes (omp A, bap, PholC and PholD). Biofilm assay was carried out in a 96 well plate using crystal violet. The cytotoxicity, internalization and adherence assay was performed on immortalized human corneal epithelial cell line(HCEC).
Results:
Majority of the isolates were multidrug resistant. However, none of them were β-lactamase producers. All isolates harbored multiple plasmids and ten distinct plasmid profiles were observed. Multiple antibiotic resistance genes transferred from donor resistant bacteria to recipient E. coli. J53. PFGE analysis of Apa I-digested genomic DNA showed the presence of distinct genotypes among all isolates. Biofilm formation assay revealed that 10 isolates were strong and two were moderate biofilm producers. Moreover, all isolates induced cytotoxicity and showed strong affinity towards adherence and internalization in HCECs. Virulence genes ompA and bap were constitutively expressed whereas the expression of PholC and PholD varied among the isolates.
Conclusions:
This study highlights an importance of A. baumannii as a potential ocular pathogen which can cause aggressive infections in the eye. Considering the highly resistant nature and their presence on ocular surface warrants further investigation to assess the pathogenesis of A. baumannii ocular infections.
Keywords: 422 antibiotics/antifungals/antiparasitics •
482 cornea: epithelium •
533 gene/expression