Bacteriophage Resistance, Adhesin’s and Toxin’s Genes Profile of Staphylococcus aureus Causing Infections in Children and Adolescents

<i>Staphylococcus aureus</i> is a common pathogen, often recovered from children's infections. Βiofilm formation, antimicrobial resistance and production of adhesins and toxins contribute to its virulence. As resistance to antimicrobials rises worldwide, alternative therapies like bacteriophages (among them the well-studied Bacteriophage K) can be helpful. The aim of this study was to determine the bacteriophage and antimicrobial susceptibility and the presence of virulence genes among <i>S. aureus</i> from infections in children and adolescents. Eighty <i>S. aureus</i> isolates were tested for biofilm formation and antimicrobial susceptibility. The presence of two genes of the <i>ica</i> operon (<i>icaA</i>, <i>icaD</i>), adhesin's (<i>fnbA</i>, <i>fnbB</i>, <i>sasG</i>) and toxin's genes (<i>PVL</i>, <i>tst</i>, <i>eta</i>, <i>etb</i>) was tested by PCRs. Susceptibility to Bacteriophage K was determined using a spot assay. Thirteen isolates were methicillin-resistant (MRSA) and 41 were multi-resistant. Twenty-five <i>S. aureus</i> (31.3%) were resistant to Bacteriophage K, mostly from ocular and ear infections. Twelve <i>S. aureus</i> (15%) were PVL-positive, seven (8.8%) positive for <i>tst</i>, 18 (22.5%) were <i>eta</i>-positive and 46 were (57.5%) <i>etb</i>-positive. A total of 66 (82.5%) isolates carried <i>fnbA</i>, 16 (20%) <i>fnbB</i> and 26 (32.5%) <i>sasG</i>. PVL, <i>tst</i> and <i>sasG</i> carriage were more frequent in MRSA. Bacteriophage-susceptible isolates carried more frequently <i>eta</i> (32.7%) and <i>etb</i> (69.1%) compared to phage-resistant <i>S. aureus</i> (0% and 32%, respectively). Although mainly methicillin-sensitive, <i>S. aureus</i> from pediatric infections exhibited high antimicrobial resistance and carriage of virulence genes (especially for exfoliative toxins and <i>fnbA</i>). MRSA was associated with PVL, <i>tst</i> and <i>sasG</i> carriage, whereas Bacteriophage susceptibility was associated with <i>eta</i> and <i>etb</i>. The high level of Bacteriophage K susceptibility highlights its potential use against staphylococcal infections.