Biofilm synthesis and its relationship with genetic characteristics in clinical methicillin-resistant staphylococci

• Main Authors: Nikolaos Giormezis, Konstantinos Papakonstantinou, Fevronia Kolonitsiou, Eleanna Drougka, Antigoni Foka, Styliani Sarrou, Evangelos D. Anastassiou, Efthimia Petinaki, Iris Spiliopoulou
• Format: Article
• Language: English
• Published: AIMS Press 2015-09-01
• Series: AIMS Bioengineering
• Subjects: methicillin-resistant staphylococci; biofilm, adhesins; bacteraemia; device-associated infections; clones
• Online Access: http://www.aimspress.com/Bioengineering/article/451/fulltext.html

<i>Staphylococcus aureus</i> can cause a broad range of infections, including skin infections, pneumonia and bacteraemia. Coagulase-negative staphylococci (CNS), mainly <i>S. epidermidis</i>, have also emerged as important pathogens, especially in immunocompromised patients or those with prosthetic devices, such as intravascular catheters or biomaterials. Of great importance in the initiation of these infections is the ability of staphylococci to adhere to various surfaces, such as host tissues and prosthetic devices and to form biofilm. The staphylococcal adhesins are encoded by a number of genes such as <i>fnbA</i> (<i>S. aureus</i> fibronectin binding protein A), <i>sasG</i> (<i>S. aureus </i>surface protein G),<i> aap </i>(<i>S. epidermidis</i> accumulation associated protein), <i>bhp</i> (Bap homologue protein) and <i>fbe</i> (fibrinogen binding protein epidermidis). In this study, 106 methicillin-resistant <i>S. aureus</i> (MRSA), 145 methicillin-resistant <i>S. epidermidis</i> (MRSE) and 70 non-epidermidis methicillin-resistant CNS (MR-CNS; 58 <i>S. haemolyticus</i>, 10 <i>S. hominis</i> and two <i>S. lugdunensis</i>) were compared in terms of biofilm formation, antimicrobial resistance, clonal distribution and adhesin genes carriage. Isolates were classified into pulsotypes by PFGE and assigned to sequence types by MLST. In total, 121/321 isolates (37.7%) produced biofilm and 219 (68.2%) carried <i>ica</i> operon. The majority was multidrug resistant (94.7%) and carried one or more adhesin genes. MRSE and all other MR-CNS prevailed in biofilm formation (<i>P</i> &lt; 0.001) and antimicrobial resistance (<i>P</i> &lt; 0.05) as compared to MRSA. MRSE also prevailed in<i> ica</i> carriage compared to the other methicillin-resistant staphylococci (<i>P</i> ≤ 0.007) Among MRSE, isolates from bacteraemias prevailed in biofilm formation (<i>P</i> = 0.031), whereas, strains from prosthetic device-associated infections carried more frequently <i>aap </i>(<i>P</i> = 0.003). Even though PFGE showed genetic diversity among MRSE, MLST revealed three major clones (ST2, ST5, ST16). MRSA isolates were less diverse, with five PFGE types and, among them, one major PFGE type (C) consisting of 77/106 strains (72.6%). MLST identified five sequence types: ST5, ST30, ST80, ST225 and ST239. One major PFGE type (h) was identified in <i>S. haemolyticus.</i> A clonal relationship was found concerning <i>fnbA</i> carriage in MRSA, <i>ica</i> carriage in MRSE, and antimicrobial susceptibility in both groups reinforcing the aspect of clonal expansion in hospital settings.