**11. Treatment of Invasive** *Candida* **Infections**

Mortality associated with *Candida* sepsis involves about half of infants, while survivors could develop severe long-term neurosensory impairment, including ocular, hearing, and cognitive impairment, cerebral palsy, and periventricular leukomalacia. Initial therapy is therefore often empirical, and the combination of prematurity, thrombocytopenia, and prolonged use of broad-spectrum antibiotics generally guides the initiation of empiric antifungal therapy [5].

Current Infectious Diseases Society of America guidelines recommend amphotericin B deoxycholate and fluconazole first-line therapies in infants with IC [44], while European guidelines recommend formulations of amphotericin B, fluconazole, and micafungin. Amphotericin B exists in various formulations, amphotericin B deoxycholate (D-AMPH-B), and liposomal amphotericin B (L-AMPH-B) [7]. The recommended dose for D-AMPH-B starts from 0.5–0.7 mg/kg/day up to 1.5 mg/kg/day. The recommended dose for L-AMPH-B is 3–5 mg/kg/day [97,98].

In neonates, the dose of fluconazole administered as therapy is 12 mg/kg/day regardless of birth weight or gestational age. The measurement of the blood levels reached (therapeutic drug monitoring) could help in establishing the drug concentrations actually reached during therapy. In fact, for many antifungal drugs, changes in clearance associated with changes in birth weight and gestational age of newborns, especially preterm, have been observed [99]. In fact, in full-term infants, the plasma half-life of fluconazole is approximately 70 h (30 h in adults) while in premature infants it is 73 h at birth, 53 h at 6 days of age, and 46 h at 12 days of age. These pharmacokinetic characteristics make fluconazole a more attractive candidate for the prevention of ICI, mainly in premature infants, allowing for infrequent administration [100].

Although L-AMPH-B and D-AMPH-B are the most commonly used antifungal drugs in newborns, there are no prospective randomized neonatal studies that provide reliable information on the pharmacokinetic properties of these drugs and their safety.

All of these antifungals have unsatisfactory levels of evidence to support their use in neonates and, when used in this special patient population, they have limits ranging from renal and bone marrow toxicity to uncertain optimal dosage regimens, increased resistance of some *Candida* spp. and, finally, suboptimal spread to the kidneys or brain tissue. There is a need for alternative antifungal drugs with greater specificity and reduced toxicity in neonatal populations than those commonly used in the treatment of invasive neonatal infections.

Echinocandins could have a prominent role in contexts where there is a wide use of prophylaxis with fluconazole and resistance of *Candida* strains to azoles could emerge. Pharmacokinetic studies demonstrated excellent tolerability, safety, and efficacy of echinocandins in neonates. Furthermore, with their ability to target 1,3-beta-D-glucan synthesis as a means of inhibiting excess production of extracellular matrix, echinocandins represent an attractive therapy against *Candida* biofilms formation [101]. The in vitro efficacy of echinocandins in treating catheter biofilms was confirmed by Cateau et al., who found that lock solutions of 2 and 5 mg/L, respectively, of caspofungin and micafungin used to treat biofilms forming on a silicone catheter led to a significant and persistent reduction of yeast metabolic activity of intermediate and mature biofilms [102]. Additionally, biofilm impairment mediated by echinocandins would trigger a larger proinflammatory response from phagocytes, due to an increase in 1,3-beta-D-glucan exposure [103].

Some problems could emerge in the therapy against *Candida parapsilosis*. Echinocandins have in fact a high minimum inhibitory concentration against *Candida parapsilosis*. Despite this awareness, no clinical failures have been reported to date. Consequently, the resistance of *Candida parapsilosis* to echinocandins remains unexplored. Micafungin is the echinocandin with the more reliable evidence in neonatal population. It is the only

echinocandin approved for neonates and young infants. The therapy at 8 mg/kg/day achieved a high response in a phase 2 study on 35 neonates with medical and surgical underlying diseases and confirmed or suspected ICIs [8].

### **12. Future Research Considerations**

Prospective studies are needed to determine the clinical implications of new diagnostic molecular tools (T2MR and CAGTA) in neonatal age and their potential use in antimicrobial stewardship.

Empiric antifungal therapy needs further evidence sustaining the efficacy in reducing mortality and long-term neurodevelopmental disabilities in preterm infants and other categories of patients. Neonatal pharmacokinetics and pharmacodynamics data of the most-used antifungal drugs are still inconclusive, due to the complexity of carrying out this type of studies in the neonatal age. Furthermore, the clearing time of fungal infection in neonates and the microbiological criteria used to define clearance are currently ambiguous.

Concerning neonates with major surgical needs, admitted in NICUs, there is lack of a precise assessment of the incidence of fungal colonization and invasive infections and lack of evidence that may, or may not, support the benefits of antifungal prophylaxis. As of 9 January 2021, no trials on ICIs are enrolling infants after major surgery, according to clinical trial registries such as: https://clinicaltrials.gov (accessed on 9 March 2021) and https://www.umin.ac.jp/ctr (accessed on 9 March 2021).

Therefore, we are currently recruiting study subjects in a multicenter prospective observational study to assess the real incidence of ICIs in surgical neonates and infants up to three months of life in NICUs. The study involves 13 of the major Italian NICUs and it is coordinated by our group at Bambino Gesù Children's Hospital (Rome, Italy). The primary outcome of the study is to assess the real incidence and risk factors of ICIs in neonates and infants up to three months of life requiring major surgery. We hope to provide the results of this research as soon as possible.

### **13. Conclusions**

Infants requiring surgery carry many risk factors for candidemia and are likely to benefit from antifungal prophylaxis. To date, guidelines for the prevention of ICIs recommend intravenous or oral fluconazole prophylaxis in ELBW infants, while no specific recommendation is available for infants requiring major surgery. This finding should not be extrapolated from previous studies, and further epidemiologic data are needed to identify possible preventive strategies against candidemia in preterm and term infants who undergo major surgery.

**Author Contributions:** Conceptualization, D.U.D.R. and C.A.; methodology, D.U.D.R. and C.A.; formal analysis, D.U.D.R., A.S., M.P.R., L.M. and C.A.; investigation and interpretation, D.U.D.R., A.S., M.P.R., L.M. and C.A.; data curation, D.U.D.R., A.S., M.P.R., L.M. and C.A.; writing—original draft preparation, D.U.D.R., A.S., M.P.R. and L.M.; writing—review and editing, L.S., P.B. (Pasqua Betta), M.M., F.C., I.C., L.P., E.B., C.T., M.G., J.B., B.D.T., G.N., D.M., P.M., A.D., P.B. (Pietro Bagolan) and C.A.; supervision, C.A.; project administration, C.A. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.

### **References**

