title: Virulence properties of multidrug resistant ocular isolates of Acinetobacter baumannii.
abstract: OBJECTIVE
  Acinetobacter (A.) baumannii is an opportunistic pathogen and has been reported as a causative agent of ocular infections. The aim of this study is to identify virulence properties (biofilm formation, adhesion, invasion and cytotoxicity) and antibiotic resistance among A. baumannii isolates recovered from the eye.
  
  
  METHODS
  The Microscan Walk-Away®, an automated bacterial identification and susceptibility testing system was used to determine antibiotic resistance. Clonal relatedness was assessed by Pulsed-field gel electrophoresis (PFGE) and plasmid profile analysis. Conjugation experiments were carried out to determine the transfer of antibiotic resistance genes and PCR was used to confirm gene transfer. Virulence properties of the isolates were determined by biofilm formation using crystal violet and immunofluorescence staining, adherence and internalization using cultured corneal epithelial cells, and cytotoxicity by TUNEL-staining and LDH release assays.
  
  
  RESULTS
  All ocular isolates (n = 12) exhibited multidrug resistant (MDR) phenotype and one of the isolate (AB12) was resistant to 18 antibiotics (β-lactam, aminoglycosides, tetracycline, chloramphenicol and quinolones). The plasmid profile analysis showed the presence of multiple plasmids in each isolate and a total of 10 different profiles were observed. However, PFGE analysis was more discriminatory which revealed 12 distinct genotypes. Antibiotic resistance (tetracycline and quinolone) was transferable from the isolate AB12 to a recipient Escherichia coli J53. Ten isolates were strong biofilm producers and the remaining two (AB5 and AB7) were moderate producers. All isolates demonstrated adherence and invasive properties towards HCECs. A similar trend was observed in their ability to cause cell death and toxicity.
  
  
  CONCLUSIONS
  Our results indicate that ocular isolates of A. baumannii are biofilm producers and adherent and invasive to corneal epithelium, a first step in the pathogenesis of ocular infection. In addition, they demonstrated plasmid-mediated transfer of MDR traits making them a reservoir of resistance genes at ocular surface.
authors: Kresge Eye Institute, Wayne State University , Detroit, MI , USA .
authors: Deepa
authors: D
authors: Talreja
authors: Chithra
authors: C
authors: Muraleedharan
authors: Gayathri
authors: G
authors: Gunathilaka
authors: Yifan
authors: Y
authors: Zhang
authors: Keith S
authors: KS
authors: Kaye
authors: Satish K
authors: SK
authors: Walia
authors: Ashok
authors: A
authors: Kumar
mesh_terms: D000151:Acinetobacter Infections / Q000188:drug therapy / Q000382:microbiology* / Q000473:pathology; D040981:Acinetobacter baumannii / Q000187:drug effects / Q000302:isolation & purification / Q000472:pathogenicity*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017209:Apoptosis; D018441:Biofilms; D015169:Colony Count, Microbial; D024901:Drug Resistance, Multiple, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D019573:Epithelium, Corneal / Q000187:drug effects / Q000382:microbiology* / Q000473:pathology; D015818:Eye Infections, Bacterial / Q000188:drug therapy / Q000382:microbiology* / Q000473:pathology; D006801:Humans; D020287:In Situ Nick-End Labeling; D012189:Retrospective Studies; D014774:Virulence
chemical_list: D000900:Anti-Bacterial Agents
keywords: A. baumannii; adherence; biofilm; corneal epithelium; multidrug resistant; ocular infection