Incidence of biofilm formation among MRSA and MSSA clinical isolates from hospitalized patients in Israel.

AIM: To assess the biofilm-producing capacities of Staphylococcus aureus strains isolated from hospitalized patients in Israel. METHODS AND RESULTS: A total of 16 S. aureus (80 MRSA and 83 MSSA) from screening (nasal swab) and clinical samples (blood and wounds) were characterized. Biofilm-producing capacities were determined using two different biofilm detection assays: Congo Red agar (CRA) and microtiter plate (MtP). In addition, a real-time PCR analysis was performed to detect the presence of biofilm-associated genes (icaA and icaD) and mecA gene. The two assays showed similar biofilm production pattern (28.2% agreement). MRSA strains tended to be greater biofilm-producers than MSSA strains. The presence of mecA was associated with biofilm production (p = 0.030). Additionally, bacteria isolated from blood samples produced less biofilm compared to those from other sources. Finally, no association was found between icaA and icaD presence and biofilm production. CONCLUSION: This study supports earlier assumptions that biofilm formation depends strongly on environmental conditions. SIGNIFICANCE AND IMPACT OF STUDY: This study significantly improved our knowledge on the biofilm production capacity of S. aureus strains in Israel. Moreover, it revealed an association between the mecA gene and biofilm production. Finally, this study underscores the importance of further research to evaluate risk factors for biofilm production.

In vitro activity of Tedizolid and Dalbavancin against MRSA strains is dependent on infection source.

OBJECTIVE: We tested the in vitro susceptibility to Tedizolid and Dalbavancin of Methicillin-resistant Staphylococcus aureus strains recovered from blood and wound cultures, and compared our results with studies conducted in the last four years. We examined whether the spa types affect the susceptibility of the different strains. METHODS: We analyzed 275 Methicillin-resistant S. aureus strains recovered from 128 blood and 147 wound samples. For each strain, we performed minimum inhibitory concentration for Tedizolid and Dalbavancin and spa typing. We also performed a non-systematic review of the worldwide literature from the last four years concerning the in vitro activity of Tedizolid and Dalbavancin using the PubMed database; results were restricted by date of publication, between January 2015 and January 2018. RESULTS: We found one Dalbavancin-resistant isolate (0.36%) and no resistance to Tedizolid. The minimum inhibitory concentration values were dependent in the strain source (wound vs. blood) for both antibiotics. For Dalbavancin, there was also dependence on the spa type. CONCLUSION: This study indicates Tedizolid and Dalbavancin have potent in vitro activity against the prevalent S. aureus clones in Israel. Further studies should be performed in order to uncover the factors contributing to reduced susceptibility of S. aureus strains to new drugs.