Factors contributing to epidemic MRSA clones replacement in a hospital setting.
The mechanisms governing the epidemiology dynamics and success determinants of a specific healthcare-associated methicillin-resistant S. aureus (HA-MRSA) clone in hospital settings are still unclear. Important epidemiological changes have occurred in Europe since 2000 that have been related to the appearance of the ST22-IV clone. Between 2006 and 2010, we observed the establishment of the ST22-IV clone displacing the predominant Italian clone, ST228-I, in a large Italian university hospital. To investigate the factors associated with a successful spread of epidemic MRSA clones we studied the biofilm production, the competitive behavior in co-culture, the capacity of invasion of the A549 cells, and the susceptibility to infection in a murine model of acute pneumonia of the two major HA-MRSA clones, ST22-IV and ST228-I. We showed that persistence of ST22-IV is associated with its increased biofilm production and capacity to inhibit the growth of ST228-I in co-culture. Compared to ST228-I, ST22-IV had a significantly higher capacity to invade the A549 cells and a higher virulence in a murine model of acute lung infection causing severe inflammation and determining death in all the mice within 60 hours. On the contrary, ST228-I was associated with mice survival and clearance of the infection. ST22-IV, compared with ST228-I, caused a higher number of persistent, long lasting bacteremia. These data suggest that ST22-IV could have exploited its capacity to i) increase its biofilm production over time, ii) maintain its growth kinetics in the presence of a competitor and iii) be particularly invasive and virulent both in vitro and in vivo, to replace other well-established MRSA clones, becoming the predominant European clone.
Emerging Bacterial Pathogens Unit, San Raffaele Scientific Institute, Milan, Italy.
Rossella
R
Baldan
Francesca
F
Testa
Nicola I
NI
Lorè
Alessandra
A
Bragonzi
Paola
P
Cichero
Cristina
C
Ossi
Anna
A
Biancardi
Paola
P
Nizzero
Matteo
M
Moro
Daniela M
DM
Cirillo
D000368:Aged; D000818:Animals; D018441:Biofilms; D045744:Cell Line, Tumor; D018920:Coculture Techniques; D003428:Cross Infection; D006761:Hospitals; D006801:Humans; D007700:Kinetics; D008168:Lung / Q000382:microbiology; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D008875:Middle Aged; D013203:Staphylococcal Infections / Q000235:genetics / Q000382:microbiology*; D037521:Virulence Factors
D037521:Virulence Factors