The connection between agr and SCCmec elements of Staphylococcus aureus strains and their response to photodynamic...

The aim of this work was to analyze the presence of specific types of agr and SCCmec in Staphylococcus aureus strains and to determine the correlation between these types of genes and the response of S. aureus strains to photodynamic inactivation.

S. aureus is an important human pathogen that is still one of the most common etiological factors of nosocomial infections. The genetic factor connected with high pathogenicity of S. aureus strains is the agr locus, which encodes a molecule responsible for activation of virulence genes. The characteristic feature of strains resistant to methicillin (MRSA) is the presence of the gene determining the resistance to β-lactam antibiotics. This gene is a part of a mobile genetic element known as Staphylococcal Chromosome Cassette mec (SCCmec). Polymorphic differences in the agr locus and SCCmec cassette enable classification of strains into different groups.

We cultured and incubated each strain with defined dose of photosensitizer (protoporphyrin diarginate). Next, strains were irradiated with a red light at a dose of 12  J/cm(2). After an 18-h incubation, the Colony Forming Units were counted and the results were analyzed statistically. Furthermore, the genetic profile of the studied strains was determined with the use of the Multiplex PCR reaction both for agr and SCCmec elements.

The results agreed with previous data, confirming that the response to photodynamic inactivation varies among different S. aureus strains. We also found a connection between some of the agr and SCCmec groups and the response of analyzed S. aureus strains to photoinactivation.

Unfortunately, those relations are not specific enough to determine a diagnostically important pattern, which could enable predictions of strain response to PDI. Nevertheless, we can conclude that the connection between the response of S. aureus strains to photoinactivation and the strain specific agr/SCCmec pattern could be observed.