Investigation of biofilm formation on contact eye lenses caused by methicillin resistant Staphylococcus aureus

Abstract

Objective: The objective was to investigate the biofilm‑forming capacity of methicillin resistant Staphylococcus aureus (MRSA) isolated from eye lenses of infected patients.
Materials and Methods: A total of 32 MRSA isolated from contact lenses of patients with ocular infections were screened for their biofilm‑forming capacity using tube method (TM), Congo red agar (CRA), and microtiter plate (MtP) methods. The effect of some stress factor on the biofilm formation was studied. The biofilm‑forming related genes, icaA, icaD and 10 microbial surface components that recognize adhesive matrix molecule (MSCRAMM), of the selected MRSA were also detected using polymerase chain reaction.
Results: Of 32 MRSA isolates, 34.37%, 59.37%, and 81.25% showed positive results using CRA, TM or MtP, respectively. Biofilm production was found to be reduced in the presence of ethanol or ethylenediaminetetraacetic acid and at extreme pH values. On the other hand, glucose or heparin leads to a concentration dependent increase of biofilm production by the isolates. The selected biofilm producing MRSA isolate was found to harbor the icaA, icaD and up to nine of 10 tested MSCRAMM genes, whereas the selected non biofilm producing MRSA isolate did not carry any of the tested genes.
Conclusions: The MtP method was found to be the most effective phenotypic screening method for detection of biofilm formation by MRSA. Furthermore, the molecular approach should be taken into consideration for the rapid and correct diagnosis of virulent bacteria associated with contact eye lenses.

Key words: Biofilm formation, eye lenses, methicillin resistant Staphylococcus aureus, microtiter plate, polymerase chain reaction