Abstract
PurposeDetermination of the association between ica genes and phenotypic biofilm formation in staphylococcal isolates involved in conjunctivitis, their antibiotic resistance as well as detection of selected virulence characteristics: adhesion to epithelial cells and in vitro cytotoxicity.MethodsThe study included 26 Staphylococcus aureus (SA) and 26 Staphylococcus epidermidis (SE) isolates. The presence of icaAD genes and ica operon was determined by the PCR assay. Phenotypic biofilm formation was verified using the microtitre plate assay. Antibiotic resistance was performed using the disc diffusion method. Staphylococcal ability to attach to host cells was assessed by flow cytometry. Cytotoxicity on epithelial cells was evaluated by LDH assay.ResultsThe ica genes were detected in 26.9% of SE and in 42.3% of SA isolates. Only 15.3% of isolates (SE) were positive for both the icaAD and the ica operon. Phenotypically, 19.2% of SE isolates were strong biofilm producers, among which three were both icaAD- and ica operon-positive. About 26.9% of SA isolates were strong biofilm producers. Methicillin resistance (MR) was detected in 34.6% of SE and 26.9% of SA isolates. About 75% of MR isolates were multidrug resistant. SA isolates adhered to host cells more extensively than SE. SA isolates released higher level of LDH than SE.ConclusionsAdherence abilities were commonly observed in staphylococci associated with conjunctivitis. However, low prevalence of isolates positive for a complete and functional ica locus and low prevalence of strong biofilm producers was detected. SA adhered to a greater extent to eukaryotic cells than SE and were more cytotoxic.
Highlights
Staphylococcal species including Staphylococcus aureus (SA) and Staphylococcus epidermidis (SE) are among the most common bacterial pathogens involved in the aetiology of acute conjunctivitis [1].Important aspects of pathogenic potential of staphylococci linked to their ability to cause conjunctivitis include initial adherence, inherent virulence, cytotoxicity, as well as evasion of the host immune system and antimicrobial tolerance/resistance facilitated by the biofilm production [2,3,4].Adherence to host cells is a preliminary step necessary to initiate and establish infection
Adherence abilities were commonly observed in staphylococci associated with conjunctivitis
The ica genes detection by PCR and its correlation to the phenotypic biofilm production Overall, the ica genes were detected by PCR in seven (26.9%) out of 26 SE isolates and in 11 (42.3%) out of 26 SA isolates included in the study
Summary
Staphylococcal species including Staphylococcus aureus (SA) and Staphylococcus epidermidis (SE) are among the most common bacterial pathogens involved in the aetiology of acute conjunctivitis [1].Important aspects of pathogenic potential of staphylococci linked to their ability to cause conjunctivitis include initial adherence, inherent virulence, cytotoxicity, as well as evasion of the host immune system and antimicrobial tolerance/resistance facilitated by the biofilm production [2,3,4].Adherence to host cells is a preliminary step necessary to initiate and establish infection. Staphylococcal species including Staphylococcus aureus (SA) and Staphylococcus epidermidis (SE) are among the most common bacterial pathogens involved in the aetiology of acute conjunctivitis [1]. Important aspects of pathogenic potential of staphylococci linked to their ability to cause conjunctivitis include initial adherence, inherent virulence, cytotoxicity, as well as evasion of the host immune system and antimicrobial tolerance/resistance facilitated by the biofilm production [2,3,4]. Staphylococci express a series of proteins/adhesins, such as the microbial surface components recognizing adhesive matrix molecules (MSCRAMMs) that bind fibrinogen, fibronectin, collagen, laminin and play a prominent role in the initial adhesion [5,6,7]. The important matrix components in the staphylococcal biofilm include the polysaccharide intercellular adhesin (PIA), extracellular DNA (eDNA), teichoic acids, and proteins [8, 9]
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