High-throughput capsular serotyping of Staphylococcus aureus.

GRUNERT, T; WENNING, M; SORDELLI, DO; BUZZOLA, FR; EHLING-SCHULZ, M

Simposio; 16th International Symposium on Staphylococci and Staphylococcal Infections, ISSSI 2014; 2014

Staphylococcus aureus frequently causes chronic infections in humans (e.g. cystic fibrosis, osteomyelitis) and animals (e.g. bovine mastitis). Since, the prevalence of non-encapsulated strains was found to be higher in chronic than in acute infections, down-regulation of capsular polysaccharide (CP) production could be a survival strategy during staphylococcal host adaptive processes. Thus, loss of CP expression might represent an important indicator for persistence and a continuous monitoring of CP expression could provide information about the progression of bacterial adaptation to its host niche. We therefore developed a high-throughput method for discrimination of the clinically important S. aureus capsular serotypes 5, 8 and non-typeable (NT) based on metabolic fingerprinting by Fourier-transform infrared (FTIR) spectroscopy and chemometrics. A comprehensive set of human and animal derived clinical isolates, representative for each CP type, were used to develop an artificial neural network assisted FTIR typing system. Our study could demonstrate that FTIR spectroscopy allows a fast and reliable discrimination of capsule expressing and non-expressing strains from human as well as from bovine origin. Furthermore, we were able to follow the transition from encapsulated to non-encapsulated subpopulations during a three months, weekly monitoring of a chronically infected dairy cow. These naturally selected strains represent an ideal starting point for an in depth analysis of factors contributing to the persistence of S. aureus in the bovine mammary gland.