Discussion
Aortic valve fungal infections, although rare, represent a critical and
life-threatening complication in patients with predisposing risk factors
such as intravenous drug use, prosthetic heart valve implantation, and
immunosuppression [7,8]. Candida species have emerged as significant
etiological agents of these infections, with Candida parapsilosis being
increasingly reported in recent years [9,10]. For instance, a
multicenter study conducted by Lefort et al. found that C.
parapsilosis accounted for 16% of all Candida species isolated from
patients with fungal endocarditis [11]. Furthermore, a review by
Pasha et al. reported a rise in the incidence of C. parapsilosisendocarditis, particularly in settings with high rates of prosthetic
valve implantation [12]
C. parapsilosis is an opportunistic organism which is a normal commensal
of the human gastrointestinal tract and the human skin, commonly found
underneath the nails of the hands [13, 14]. Unlike other fungal
causes of invasive disease such as C. tropicalis and C.
albicans , invasive infections with C. parapsilosis can occur in
the absence of prior colonization with the organisms. Notable risk
factors in these cases are patients with preceding surgeries, usually of
the gastrointestinal tract, immunocompromised patients such as those
with Human Immunodeficiency Virus/Acquired-Immunodeficiency Disease
Syndrome, critically-ill patients requiring long-term placement of
invasive vascular lines; and neonates with very low birth weights
[13]. Intravenous drug use is a known risk factor for invasive
fungal infections with Candida species, particularly infections caused
by C. parapsilosis [13].
C. parapsilosis has been recognized as an important pathogen in
various invasive fungal infections, such as candidemia, meningitis,
peritonitis, ocular infections, and endocarditis [9]. In cases ofC. parapsilosis endocarditis, the aortic valve is most commonly
affected, with a demonstrated predilection for prosthetic aortic valves
[15,16]. In the rare cases of C. parapsilosis endocarditis of
a native valve, a history of intravenous drug use is usually present
[17]. In both scenarios, endocarditis secondary to C.
parapsilosis is usually preceded by fungemia [16, 17].
Distinguishing between candida and bacterial endocarditis during the
initial assessment can pose significant challenges, as both can present
with non-specific symptoms [18, 19]. Candida endocarditis typically
presents as subacute endocarditis, and C. parapsilopasendocarditis is frequently associated with septic emboli, which may
involve many organs due to its predilection for the aortic valve
[19].
Definitive therapy for both native valve and prosthetic valve Candida
endocarditis involves medical management, generally with long-term
antifungal therapy and surgical management. The 2016 Infectious Diseases
Society of America (IDSA) guidelines recommend amphotericin B with or
without the addition of flucytosine or high-dose echinocandins
(micafungin, caspofungin) as the initial therapy for Candida native
valve and prosthetic valve endocarditis. Following this initial therapy,
long-term therapy with fluconazole (400–800 mg per day) is recommended
to ensure clearance of fungemia [20]. In addition to medical
therapy, valvular replacement is also recommended, with continued
antifungal therapy with fluconazole for at least six weeks following
surgery or even longer in those patients with perivalvular abscesses for
native valve endocarditis. Chronic suppressive therapy with daily
high-dose fluconazole is recommended for patients with prosthetic valve
endocarditis [20]. For those patients who are high-risk surgical
candidates, long-term daily suppressive therapy with fluconazole in
doses of 400–800 mg is recommended [20].
One of the challenges to definitive treatment in cases of Candida
endocarditis, particularly with C. parapsilosis, is the increased
risk of recurrence, which is most often due to inadequate clearance of
fungemia (resulting in persistent fungemia) and the use of inappropriate
antifungal therapy [21]. C. parapsilosis fungemia has been
identified as a specific risk factor for the recurrence of endocarditis,
as demonstrated in a retrospective case-control study by Munoz et al,
mainly attributed to its ability to form biofilms [22]. Biofilms
impede the therapeutic actions of antifungal agents, rendering organisms
relatively resistant to antimicrobial agents [23]. Antimicrobial
sensitivities obtained in our case revealed that the C.
parapsilosis was sensitive to the first-line antifungal therapies used
in her treatment. Therefore, the persistent fungemia and relapsing
endocarditis encountered in our case is likely the result of inadequate
clearance of the organism due to its biofilm production, as supported in
the literature.
One of the challenges experienced in this case is the limited
evidence-based guidance on managing persistent Candidemia despite
appropriate antifungal therapy and recurrent C. parapsilosis
endocarditis, as seen in our case. Notably, recurrent aortic valve
infections caused by C. parapsilosis are associated with high
morbidity and mortality rates. The mortality rate of C.
parapsilosis endocarditis approaches 40%, necessitating a
comprehensive understanding of this pathogen and its propensity for
recurrence [18, 24].