Successful fluoroquinolone-based salvage therapy in the conservative management of refractory infective endocarditis caused by <i>Streptococcus anginosus</i> in an elderly patient: a case report

Infective endocarditis (IE) is a life-threatening condition, often requiring surgical intervention; however, in cases where surgery is contraindicated, conservative management relies on appropriate antibiotic therapy. Moreover, modification of antibiotics can be critical, as certain agents may be superior in resolving infection and associated complications. We present the case of an 88-year-old woman with IE due to <i>Streptococcus anginosus</i>, successfully treated with oral antibiotics. Transthoracic echocardiography revealed vegetations on the mitral and aortic valves, along with moderate-to-severe valvular dysfunction. Despite 6-week treatment with intravenous ampicillin, her condition showed limited improvement. A strategic switch to levofloxacin led to remarkable clinical progress, with significantly reduced vegetation size and normalized inflammatory markers. The effectiveness of levofloxacin, due to its biofilm penetration and bactericidal activity, indicates the potential for customized antibiotic regimens to achieve positive outcomes. This case illustrates that even when standard treatment is unsuccessful, careful antibiotic adjustment can significantly impact the therapeutic course.