Abstract
Staphylococcus haemolyticus is the second most frequently isolated CoNS from ocular infections and human blood cultures. In this study, we examined 18 ocular S. haemolyticus isolates for their capacity to form biofilm and conducted detachment assay to determine the composition of the biofilm matrix and involvement of various elements in cell lysis. PCR identified the presence of biofilm-associated genes, and ica operon and CLSM visualized the components of the biofilm matrix. We found that PIA-independent biofilm formation is the characteristic feature of S. haemolyticus isolates, irrespective of the sources of isolation, and protein or DNA or both are the major components of the biofilm matrix. Cell lysis enabling DNA release was an essential step for biofilm attachment during the initial stages of biofilm development. The srtA transcript expression study indicates its role in the early stages of biofilm development. We found the presence of antibiotic resistance genes in the eDNA and gDNA thus suggesting the possible role of biofilm in horizontal gene transfer of antibiotic resistance determinants. The overall study indicates that S. haemolyticus formed the biofilm comprising of protein or DNA or both and srtA play a role in the initial development of biofilm.
Highlights
Staphylococcus haemolyticus is the second most frequently isolated pathogen from ocular infections and blood cultures among the coagulase-negative staphylococci (CoNS) (Takeuchi et al, 2005; Makki et al, 2011; Becker et al, 2014)
We found all the ocular S. haemolyticus isolates belonging to the infected eye, and healthy conjunctiva formed a biofilm on polystyrene microtiter plates
Four strains did not show any detachment upon NaIO4 or DNase I treatment. This finding suggests that either the protein or extracellular DNA (eDNA) or both are the primary component of the biofilm matrix in most of the isolates
Summary
Staphylococcus haemolyticus is the second most frequently isolated pathogen from ocular infections and blood cultures among the coagulase-negative staphylococci (CoNS) (Takeuchi et al, 2005; Makki et al, 2011; Becker et al, 2014). This organism is implicated in hospital-acquired infections occurring through implanted medical devices (Mehta and Kumari, 1997; Mack et al, 2006) and exhibits the highest level of multidrug resistance including hetero-resistance to glycopeptides thereby limiting the therapeutic options (Fredheim et al, 2009; Czekaj et al, 2015). Both Fbe (Cucarella et al, 2001) and AtlE (Heilmann et al, 1997) bind to the host factors fibrinogen and vitronectin and Bhp
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