Daptomycin activity against multi-resistant Staphylococcus haemolyticus bloodstream isolates from severe infections
Abstract number: p1585
Campanile F., Venditti M., Borbone S., Bongiorno D., Penni A., Stefani S.
Daptomycin, a new cyclic lipopeptide with activity against multidrug-resistant Gram-positive pathogens including MRSA, is approved for use in cSSST infections (US-FDA) and is being reviewed by EMEA for approval in EU member countries. The rapid bactericidal activity of daptomycin, due to its unique mechanism of action, makes it an attractive antibiotic for serious Gram-positive infections. The study was performed: (i) to evaluate the activity of daptomycin and other drugs against 50 multi-resistant clinically relevant Staphylococcus haemolyticus (MRSH), isolated from bloodstream infections in various hospitals in Italy (ii) to determine epidemiologic and genetic correlation among strains, and (iii) to characterize the SCCmec DNA of these strains.
The MRSH strains were tested against a panel of antimicrobial agents, by broth microdilution method performed according to CLSI (Clinical Laboratory Standards Institute) guidelines, including supplementation of 50 mg/L calcium for daptomycin. Moreover, phenotypic tests and antibiotic susceptibility profiling were carried out and the results compared with molecular typing analysis by using SmaI-PFGE fingerprints and PCR to characterize the mec-complex.
All isolates were resistant to erythromycin, gentamicin, ciprofloxacin, 16 strains showed reduced susceptibility to vancomycin (MICs 2 mg/L), 24 strains were resistant to cotrimoxazole, 16 strains to clindamycin, 6 strains to chloramphenicol and 3 strains to tetracycline. Almost all isolates were inhibited by <=1 mg/L of daptomycin, and only four strains exhibited a MIC value of 2 mg/L. PFGE analyses showed the existence of at least two multi-resistant S. haemolyticus clones widespread in different hospitals. Methicillin-resistance was correlated to the presence of the mecA and preliminary results regarding the genetic element carrying the gene, showed an organization of the mec-complex of class A and class C.
Our results suggest that daptomycin has excellent activity against multiresistant MR S. haemolyticus isolates, which represent a serious threat in catheter-related bloodstream infections. Furthermore, the emergence of S. haemolyticus exhibiting reduced susceptibility to vancomycin is of particular concern, probably due to the common use of vancomycin as initial therapy for such infections. Moreover, the use of additional molecular techniques to fingerprint isolates makes this study of clinically important CoNS more accurate.
|Session name:||XXIst ISTH Congress|
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