Ceftriaxone has commonly been used to treat HACEK IE220 and is reason- able for treatment (Table 16). The duration of therapy for NVE of 4 weeks is reasonable; for PVE, the duration of therapy of 6 weeks is reasonable. Gentamicin is no longer recommended because of its nephrotoxicity risks. The HACEK group is usually susceptible in vitro to fluo- On the basis of these susceptibility data, a flu- oroquinolone (ciprofloxacin, levofloxacin, or moxifloxacin) may be considered as an alternative agent in patients unable to tolerate ceftriaxone (or other third- or fourth-generation cephalosporins) therapy. There are only a few case reports of HACEK IE treated with a fluoroquinolone, however. In addi- tion, ampicillin-sulbactam may be considered a treatment option, although HACEK resistance to this agent in vitro has Accordingly, patients with HACEK IE who cannot tolerate ceftriaxone therapy should be treated in con- sultation with an infectious diseases specialist. Recommendations 1. Unless growth is adequate in vitro to obtain suscep- tibility testing results, HACEK microorganisms are considered ampicillin resistant, and penicillin and ampicillin should not be used for the treatment of patients with IE (Class III; Level of Evidence C). 2. Ceftriaxone is reasonable for treatment of HACEK IE (Class IIa; Level of Evidence B). 3. The duration of therapy for HACEK NVE of 4 weeks is reasonable (Class IIa; Level of Evidence B); for HACEK PVE, the duration of therapy of 6 weeks is reasonable (Class IIa; Level of Evidence C). 4. Gentamicin is not recommended because of its nephrotoxicity risks (Class III; Level of Evidence C). 5. A fluoroquinolone (ciprofloxacin, levofloxacin, or moxifloxacin) may be considered an alternative agent for patients unable to tolerate ceftriaxone (or other third- or fourth-generation cephalosporins) (Class IIb; Level of Evidence C). 6. 