22Methicillin-resistant Staphylococcus aureus (MRSA) acquisition in cystic fibrosis (CF) patients 23 confers a worse clinical outcome with increased rate of declined lung function. Telavancin, an 24 approved lipoglycopeptide used to treat infections due to S. aureus has a dual mode of action 25 causing inhibition of the peptidoglycan synthesis and membrane depolarization. CF-associated 26 MRSA infections remain an important problem with no foreseeable decline in prevalence rates. 27 Although telavancin is currently in clinical use for complicated skin infections and hospital-28 acquired pneumonia, the activity against CF-associated S. aureus infections has not been 29 investigated. In this work, we studied the activity of telavancin against CF S. aureus strains 30 collected from diverse geographical CF centers in the USA. We found that telavancin-MIC90 was 31 0.06 g/ml, 8-fold lower than ceftaroline or daptomycin and 25-fold lower than linezolid and 32 vancomycin. We demonstrate that telavancin at serum-free concentrations has rapid bactericidal 33 activity with a decrease of more than 3 log10 CFU/ml during the first 4 to 6 hours of treatment, 34 performing better in this assay than vancomycin and ceftaroline, including S. aureus resistant to 35 ceftaroline.
36Telavancin resistance was infrequent (0.3%), although we found that it can occur in-vitro in both 37 CF-and non-CF S. aureus strains by progressive passages with sub-inhibitory concentrations.
38Genetic analysis of telavancin in-vitro mutants showed gene polymorphisms in cell wall and 39 virulence genes, and increased survival in a Galleria mellonella infection model. Thus, we 40 conclude that telavancin represents a promising therapeutic option for CF infections with potent 41 in-vitro activity and low resistance potential. 42 43 48for β-lactams and can mediate cell wall assembly when the normal staphylococcal PBPs (PBP1 to 49 4) are inactivated by these agents (1). S. aureus is one of the earliest and more prevalent pathogens 50 colonizing respiratory tracts and then causing infection in people with cystic fibrosis (CF). This 51 severe, autosomal recessive disease affects several organs, notably the lungs, predisposing these 52 patients to reduced respiratory function and infections with potentially severe consequences.
53According to recent data from the CF Foundation Patient Registry, the prevalence in USA of 54 MSSA is around 70%, while MRSA is 26%. These values compare to 13% in Europe, 6% in 55 Canada and 3% in Australia (2, 3). Emerging research has demonstrated that MRSA infections 56 have a significant clinical impact on individuals with underlying chronic diseases such as CF, 57 where antibiotic pressure and metabolic adaptions may favor the ability of S. aureus to establish 58 long persistence and resistance (4). Additional mechanisms reported in CF lung and other chronic 59 MRSA infections reduce antibiotic activity including small colonies variant adaptation, biofilm 60 formation and growth under anaerobic conditions, which are associat...