**12. Quinolones**

European Society of Cardiology (ESC) Clinical Practice Guidelines include Ceftriaxone in their recommendations for treatment of endocarditis caused by *A. defectiva* or *Granulicatella* slightly differing from AHA recommendations. ESC recommendation for treatment of IE caused by *A. defectiva or Granulicatella* is Penicillin G, Ceftriaxone or Vancomycin for 6 weeks,

Iv Vancomycin is recommended as an alternative regimen to iv penicillin for those patients

Bouvet et al. by using an experimental animal model found that Vancomycin alone was as good as combination of Vancomycin and Gentamicin for treatment of endocarditis caused by NVS [58]. Vancomycin susceptibility breakpoint is typically MIC <1 μg/ml and no resistance to Vancomycin among NVS has been reported thus far [62, 64, 66]. It is notable however that MIC90 for Vancomycin is 2 times higher for *G. adiacens* compared to *A. defectiva* or *G. elegans* [62, 66].

NVS remains susceptible to aminoglycosides (MICs for Gentamicin and streptomycin ≤4 μg/ml), high level aminoglycoside resistance has not been reported. As per AHA and BSAC guidelines for treatment of infective endocarditis caused by *Abiotrophia* or *Granulicatella*

Macrolide resistance is common among *Abiotrophia* and *Granulicatella species* (49.2% of all isolates sensitive to erythromycin vs. 87% of all isolates sensitive to Clindamycin) [62]. Resistance mechanisms include efflux among *mef*(A) positive isolates and *erm*(B) gene causing resistance to both Erythomycin and Clindamycin [64]. It was shown that *erm*(B) gene is located on Tn916-related transposon in *A. defectiva* similar to the pneumococcal transposon Tn3872, enabling Abiotrophia to act as a donor and recipient of antibiotic resistance [72]. Macrolide resistance pattern of NVS is suggestive of constitutive macrolide-lincosamide-streptogramin B (cMLSB) phenotype. Zheng et al. noted that all three isolates of NVS that carried erm(B) (*G. adiacens* and *G. elegans*) also carried *tet*(M), tetracycline resistance gene which is carried on the same transposon as ermB gene [62, 64].

Resistance to Meropenem or Imipenem among *Abiotrophia* and *Granulicatella species* is rare. Review of 132 isolates by Albierti showed 100% sensitivity to Meropenem and Imipenem

species, iv gentamicin is combined with iv penicillin (first line treatment) [33, 56].

combined with an aminoglycoside at least for the first 2 weeks [71].

who are not able to tolerate penicillin or ampicillin [33].

**8. Vancomycin**

50 Advanced Concepts in Endocarditis

**9. Aminoglycosides**

**10. Macrolides**

**11. Carbapenems**

Resistance to quinolones among NVS is rare. 8 *G. adiacens* [62] and one *G. elegans* [70] isolates have been reported to be resistant to Levafloxacin. The case of *G. elegans* resistant to Levafloxacin was isolated from a patient with neutropenic fever with bacteremia who had previously received Levafloxacin therapy. Mechanism of NVS resistance to quinolones is yet to be determined [62].
