Heterogeneity of methicillin-resistant Staphylococcus aureus strains (MRSA) characterized by flow cytometry.

We used fluorescent penicillin Bocillin FL for characterization of control methicillin-resistant Staphylococcus aureus (MRSA) strains belonging to one of four heterogenic classes and comparing them with clinical MRSA isolates. Significant differences in percentage of fluorescent cells and reduction of Bocillin FL binding after incubation with methicillin between control strains from classes I and IV were observed, whereas the strains from classes II and III were differed after incubation with methicillin. According to this criteria, 55.8% of the clinical isolates population were similar to the strain of class IV or homogenic resistant, 11.8% was found as I, and 32.3% were categorized as class II or III. However, continuous diversity of measured features was also discussed.