Invasive bacterial and fungal infections in paediatric patients with cancer: incidence, risk factors, aetiology and outcomes in a UK regional cohort 2009-2011

Comparing the clinical characteristics and outcomes of septic shock children with and without malignancies: a retrospective cohort study

OBJECTIVE

There is an amelioration in mortality rates of septic shock patients with malignancies over time, but it remains uncertain in children. Therefore, the authors endeavored to compare the clinical characteristics, treatment needs, and outcomes of septic shock children with or without malignancies.

METHODS

The authors retrospectively analyzed the data of children admitted to the PICU due to septic shock from January 2015 to December 2022 in a tertiary pediatric hospital. The main outcome was in-hospital mortality.

RESULTS

A total of 508 patients were enrolled. The proportion of Gram-negative bacteria and fungal infections in children with malignancies was significantly higher than those without malignancies. Septic shock children with malignancies had a longer length of stay (LOS) in the hospital (21 vs. 11 days, p<0.001). However, there were no statistically significant differences in the LOS of PICU (5 vs. 5 days, p = 0.591), in-hospital mortality (43.0 % vs. 49.4 %, p = 0.276), and 28-day mortality (49.2 % vs. 44.7 %, p = 0.452). The 28-day survival analysis (p = 0.314) also showed no significant differences.

CONCLUSION

Although there are significant differences in the bacterial spectrum of infections, the septic shock children with or without malignancies showed a similar mortality rate. The septic shock children with malignancies had longer LOS of the hospital.

Invasive fungal disease in children with solid tumors: An Australian multicenter 10-year review

Invasive fungal disease (IFD) occurs less frequently during treatment for solid compared to hematological malignancies in children, and risk groups are poorly defined. Retrospective national multicenter cohort data (2004-2013) were analyzed to document prevalence, clinical characteristics, and microbiology of IFD. Amongst 2067 children treated for solid malignancy, IFD prevalence was 1.9% overall and 1.4% for proven/probable IFD. Of all IFD episodes, 42.5% occurred in patients with neuroblastoma (prevalence 7.0%). Candida species comprised 54.8% of implicated pathogens in proven/probable IFD. In children with solid tumors, IFD is rare, and predominantly caused by yeasts.Routine prophylaxis may not be warranted.

Characterization of Febrile Neutropenia Management in Children With Malignancies: A Single-Center Evaluation

OBJECTIVE

Current recommendations for febrile neutropenia (FN) include initiation of broad-spectrum antibiotics without clear indications of when or how to de-escalate or target therapy, especially in those without microbiologically defined bloodstream infections (MD-BSIs). The purpose of this study is to characterize a pediatric FN population, FN management, and identify the proportion of patients with MD-BSI.

METHODS

This study was a single-center, retrospective chart review of patients admitted to the University of North Carolina Children's Hospital between January 1, 2016, and December 31, 2019, with a diagnosis of FN.

RESULTS

There were 81 unique encounters included in this study. MD-BSI was the etiology of fever in 8 FN episodes (9.9%). The most common empiric antibiotic regimen was cefepime (62%) followed by cefepime and vancomycin (25%). The most common de-escalation type was the discontinuation of vancomycin (83.3%), and the most common type of escalation was the addition of vancomycin (50%). The median antibiotic total duration in patients without MDI-BSI was 3 days (IQR, 5-9).

CONCLUSIONS

In this single-center, retrospective review, most FN episodes were not due to an MD-BSI. There were inconsistencies in practice of when discontinuation of antibiotic therapy occurred in patients without MD-BSI. De-escalation or cessation of antibiotic therapy before neutropenia resolution did not result in any documented complication. These data suggest a role for implementing an institutional guideline to improve consistency in antimicrobial use in pediatric patients with febrile neutropenia.

Children with malignancies and septic shock - an attempt to understand the risk factors

OBJECTIVES

To explain the high mortality of septic shock in children with cancer.

METHODS

A retrospective cohort from 2016 to 2020, of children aged 0 to 18 years, and septic shock.

RESULTS

The authors included 139 patients. Acute lymphocytic leukemia was the most frequent diagnosis (16.5%), and Gram-negative bacteria were the most frequent blood culture isolates (22.3%). There were 57 deaths in ICU (41%), 10 in the first 24 hours of shock (early death). A LASSO model with variables: neutropenia (coefficient 0.215), respiratory (0.81), hematological (1.41), and neurological (0.72) dysfunctions, age (-0.002) and solid tumor recurrence (0.34) generated AUC = 0.79 for the early death outcome. Survivors had significant differences in the PRISM-IV score (mean ± SD 10.9 ± 6.2 in the survivors, 14.1 ± 6.5 in the deceased, p = 0.004), and in the mean number of organ dysfunctions (3.2 ± 1.1 in the survivors, 3.8 ± 6.5 in the deceased, p < 0.001). A positive fluid balance in the first 24 hours of sepsis between 2% and 6% of body weight showed a reduction effect on the probability of death in ICU (hazard ratio 0.47, 95% CI 0.24-0.92, p = 0.027). The recurrence of any cancer was a predictor of in-hospital death, regardless of severity.

CONCLUSIONS

Recurrence of any cancer is an important risk of sepsis-related death. A positive fluid balance between 20 and 60 mL/kg or 2% and 6% of body weight in the first 24 hours after the onset of sepsis is related to lower mortality.

Bacteremia in Children with Solid Tumors: Etiology, Antimicrobial Susceptibility, Factors Associated with Multidrug Resistance, and Mortality

This retrospective study aims to describe the etiology and resistance patterns of pathogens causing bacteremia in children with solid tumors in a tertiary pediatric hematology-oncology center in Jerusalem, Israel (2011-2019). Factors associated with multidrug-resistant (MDR) bacteremia and mortality were analyzed. A total of 228 pathogens were isolated in 126 patients; 61.0% were gram-negative rods (GNR) and 38.2% were gram-positive cocci (GPC). The most common pathogens were Klebsiella pneumoniae (19.3%), Escherichia coli (17.5%), and coagulase-negative staphylococci (16.2%). The proportion of MDR-GNR was 18.2%, while the proportion of MDR-GPC was 55.2%. In logistic regression analysis, breakthrough bacteremia on a penicillin-group antibiotic (odds ratio [OR] 5.69, [95% confidence interval 1.42-22.76], p-value = 0.014) was associated and underlying diagnosis of neuroblastoma was inversely associated (OR 0.17, [0.04-0.81], p-value = 0.026) with MDR-GNR bacteremia; while the previous hospitalizations' duration (OR 1.032/day, [1.01-1.06], p-value = 0.007) and oncologic treatment intensity (OR 2.19, [1.08-4.45, p-value = 0.03) were associated with MDR-GPC bacteremia. Shock, prolonged profound neutropenia, and pediatric intensive care unit (PICU) admission were associated with 7-day mortality; and relapsed disease, oncologic treatment intensity, prolonged profound neutropenia, and PICU admission-with 30-day mortality in the univariate analyses. Empirical antibiotic choice should be based on factors associated with MDR infections in this specific population.

Predictive Factors for Gram-negative Versus Gram-positive Bloodstream Infections in Children With Cancer

BACKGROUND

Identifying potential predictive factors for the type of bacteremia (Gram-negative vs. Gram-positive) in children with cancer would be crucial for the timely selection of the appropriate empiric antibiotic treatment.

MATERIALS AND METHODS

Demographic, clinical, and laboratory characteristics of children with cancer and a bacterial bloodstream infection (BSI) (February 1, 2011 to February 28, 2018) in a tertiary pediatric oncology department were retrospectively examined and were correlated with the type of isolated bacteria.

RESULTS

Among 224 monomicrobial bacterial BSI episodes, Gram-negative and Gram-positive bacteria were isolated in 110 and 114 episodes, respectively. Gram-negative bacteria were isolated significantly more frequently in girls (Gram-negative/Gram-positive ratio 1.7:1) versus boys (Gram-negative/Gram-positive ratio 0.72:1), P=0.002, in patients with previous BSI episodes (1.4:1) versus those without (0.8:1), P=0.042, and in children with hematologic malignancy (1.3:1) versus those who suffered from solid tumors (0.52:1), P=0.003. Gram-negative BSI episodes were more frequently correlated with a lower count of leukocytes, P=0.009, neutrophils, P=0.009 and platelets, P=0.002, but with significantly higher C-reactive protein (CRP) levels, P=0.049. Female sex, hematologic malignancy, and higher CRP levels remained independent risk factors for Gram-negative BSI in the multivariate analysis. Among neutropenic patients, boys with solid tumors and a recent central venous catheter placement appear to be at increased risk for Gram-positive BSI in the multivariate analysis.

CONCLUSIONS

Although Gram-negative and Gram-positive BSIs are close to balance in children with cancer, Gram-negative bacteria are more likely to be isolated in girls, children with hematologic malignancies and those with higher CRP level at admission. In contrast, neutropenic boys with solid tumors and a recently placed central venous catheter may be at increased risk for Gram-positive BSI indicating probably the need for initially adding antibiotics targeting Gram-positive bacteria.

Patient Outcomes With Febrile Neutropenia Based on Time to Antibiotics in the Emergency Department

OBJECTIVE

Although bacteremia in pediatric oncology patients with febrile neutropenia (FN) is not uncommon, sepsis and mortality are rare. Because of the lack of clinically meaningful decision tools to identify high-risk patients with bacteremia, time to antibiotic administration (TTA) is increasingly considered an important quality and safety measure in the emergency department. Because little evidence exists suggesting that this benchmark is beneficial, we sought to determine whether TTA of 60 minutes or less is associated with improved outcomes.

METHODS

We retrospectively reviewed patients presenting to a pediatric emergency department with FN from November 2013 to June 2016. Clinical outcomes including mortality, pediatric intensive care unit admission, imaging, fluid resuscitation of 40 mL/kg or greater in the first 24 hours, and length of stay were compared between TTA of 60 minutes or less and more than 60 minutes.

RESULTS

One hundred seventy-nine episodes of FN were analyzed. The median TTA was 76 minutes (interquartile range, 58-105). The incidence of bacteremia was higher in patients with TTA of more than 60 minutes (12% vs 2%, P = 0.04), but without impact on mortality, pediatric intensive care unit admission, fluid resuscitation, or median length of stay. The median TTA was not different for those who were and were not bacteremic (91 vs 73 minutes, P = 0.11).

CONCLUSIONS

Time to antibiotic administration of more than 60 minutes did not increase mortality in pediatric oncology patients with FN. Our study adds to the existing literature that TTA of 60 minutes or less does not seem to improve outcomes in pediatric FN. Further larger studies are required to confirm these findings and determine which features predispose pediatric FN patients to morbidity and mortality.

The current state of immunization against Gram-negative bacteria in children: a review of the literature

PURPOSE OF REVIEW

Gram-negative bacteria (GNB) are a major cause of infection worldwide and multidrug resistance in infants and children. The major pathogens include Klebsiella pneumoniae, Escherichia coli, Enterobacter spp., Pseudomonas aeruginosa and Acinetobacter baumannii. With new antibiotic options limited, immunization is likely to play a critical role in prevention. This review discusses their epidemiology, the current state of vaccine research and potential immunization strategies to protect children. A comprehensive review of the literature, conference abstracts along with web searches was performed to identify current and investigational vaccines against the major GNB in children.

RECENT FINDINGS

Phase I--III vaccine trials have been undertaken for the major Gram-negative bacteria but not in infants or children. E. coli is a common infection in immune-competent children, including neonatal sepsis. Several vaccines are in late-phase clinical trials, with some already licensed for recurrent urinary tract infections in women. Klebsiella spp. causes community-acquired and hospital-acquired infections, including sepsis in neonates and immunocompromised children although no vaccine trials have extended beyond early phase 2 trials. P. aeruginosa is a common pathogen in patients with cystic fibrosis. Phase 1--3 vaccine and monoclonal antibody trials are in progress, although candidates provide limited coverage against pathogenic strains. Enterobacter spp. and A. baumannii largely cause hospital-acquired infections with experimental vaccines limited to phase 1 research.

SUMMARY

The current immunization pipelines for the most prevalent GNB are years away from licensure. Similar to incentives for new antibiotics, global efforts are warranted to expedite the development of effective vaccines.

Infectious Morbidity in Pediatric Patients Receiving Neoadjuvant Chemotherapy for Sarcoma

Simple Summary

Infections are an important cause of morbidity and mortality in childhood cancer treatment. The aim of our retrospective study was to assess the infectious burden in pediatric sarcoma patients during neoadjuvant chemotherapy administered according to the EWING 2008, CWS SoTiSaR and EURAMOS clinical trial or registry. Our analyses indicate a substantial infectious morbidity in this group of patients, with 58.8% experiencing at least one episode of febrile neutropenia (FN) and 20.6% at least one microbiologically documented infection (MDI). We also identified parameters that impact on the occurrence of FN and MDIs, including treatment protocol, patient age, and mucositis. These findings may contribute to a better risk stratification for prevention and management of FN and infections as well as for maintaining quality of life, cost control, and optimum outcomes of anticancer treatment.

Abstract

The purpose of this retrospective, single-center cohort study was to assess the infectious burden in pediatric sarcoma patients during neoadjuvant chemotherapy. The review included all patients with a new diagnosis of Ewing sarcoma, osteosarcoma or soft tissue sarcoma between September 2009 and December 2018 who were enrolled in the EWING 2008, CWS SoTiSaR and EURAMOS clinical trial or registry. Primary endpoints were the occurrence of febrile neutropenia (FN) and microbiologically documented infection (MDI). Parameters with a potential impact on FN and MDI were also analyzed. A total of 170 sarcoma patients (median age: 13 years, range: 0–21; 96 m/74 f) received 948 chemotherapy courses (median: 6; range: 2–8). Of these patients, 58.8% had ≥1 FN episode and 20.6% ≥ 1 MDI. FN occurred in 272/948 courses (28.7%) with fever of unknown origin (FUO) in 231 courses and 45 MDI and 19 clinically documented infections (CDI) occurring in a total of 57 courses. Patients enrolled in EWING 2008 had significantly more FN (p < 0.001), infections (p = 0.02) and MDI (p = 0.035). No infection-related deaths were observed. Younger age, tumor type and localization, and higher median and maximum mucositis grades were significantly associated with higher numbers of FN (p < 0.001), and younger age (p = 0.024) and higher median mucositis grade (p = 0.017) with MDI. The study shows substantial infectious morbidity in sarcoma patients during neoadjuvant chemotherapy treatment and opportunities to improve prevention and management.

Microbiologically Documented Bloodstream Infection in Children With Malignancies: A Single-center Experience

BACKGROUND

Bloodstream infection (BSI) remains a considerable cause of morbidity and mortality for cancer patients. With a better understanding of it, better methods can be used. The primary objective of this study was to describe the characteristics of BSIs in our institution, and the second was to determine the possible risk factors associated with them.

MATERIALS AND METHODS

Data of cancer patients from 2009 to 2015 at our institution were included. Medical information and blood cultures were analyzed to determine the BSI rate. The χ and Fisher exact tests were used for categorical data and to determine risk factors associated with BSIs and pathogens.

RESULTS

A total of 565 (8.6%) events were diagnosed with BSIs. Although Gram-negative bacteria (52.6%) were the most commonly isolated pathogens, Gram-positive microorganisms (45.0%) were also prevalent. Oral and gastrointestinal organisms were common. Pathogens were more likely to be identified in patients with central venous catheters and in patients with prolonged neutropenia (P<0.05).

CONCLUSIONS

This study provides updated epidemiology in BSIs and helps with the prevention and management of suspected BSIs in vulnerable patients. Better anti-infection therapy could be provided to these patients based on the isolated pathogens.

Prevalence, Epidemiology, Etiology, and Sensitivity of Invasive Bacterial Infections in Pediatric Patients Undergoing Oncological Treatment: A Multicenter Nationwide Study

Background: Infectious complications (IC) caused by bacterial strains often impede anticancer therapy. The study aimed to retrospectively analyze bacterial IC that could help predict the risk and optimize the empirical treatment for bacterial infections in pediatric cancer patients. Patients and Methods: Over a 72-month period, all-in 5,599 children with cancer: 2,441 patients with hematological malignancy (HM including acute leukemias, Hodgkin and non-Hodgkin lymphomas [NHLs], and Langerhans cell histiocytosis) and 3,158 with solid tumors (STs including central nervous system tumors, neuroblastoma, Wilms' tumor, soft tissue sarcoma, germ cell tumors, Ewing sarcoma, osteosarcoma, hepatoblastoma, and others) were enrolled into the study. Episodes of bacterial infectious complications (EBICs) confirmed by microbiological findings were reported by each hospital and analyzed centrally. Results: At least 1 EBIC was diagnosed in 2,155 (36.8%) children (1,281 [59.4%] with HM and 874 [40.6%] with ST; p < 0.001). All-in 4,860 EBICs were diagnosed including 62.2% episodes in children with HM and 37.8% in children with ST (p < 0.001). Having analyzed the source of infections, blood stream infections predominated, apart from NHL patients in whom the most common type was gut infections. The profile of bacteria strains was different in HM and ST groups (p < 0.001). However, in both groups the most common Gram-negative pathogen was Enterobacteriaceae, with the rate being higher in the HM group. Among Gram-negative strains low susceptibility to ceftazidime, whereas among Enterococcus spp. low susceptibility to vancomycin was noticed. The rate of multidrug-resistant (MDR) pathogens was high, especially for Gram negatives (47.7% vs. 23.9%; p < 0.001). The survival after infections was comparable for HM and ST patients (p = 0.215). Conclusions: The risk of bacterial IC in HM patients was higher than in the ST group. The high rate of MDR strains was detected in pediatric cancer patients, especially in those with HM.

Blood Stream Infections and Antibiotic Utilization in Pediatric Leukemia Patients With Febrile Neutropenia

BACKGROUND

Frequent surveillance of bacterial pathogens responsible for microbiologically defined-blood stream infections (MD-BSI), and their respective antibiotic susceptibilities is central to tailoring empiric antibiotic therapy in febrile neutropenia (FN) episodes in pediatric patients with leukemia. The safety of deescalating antibiotic therapy in pediatric patients with leukemia and neutropenia is incompletely understood.

METHODS

A retrospective chart review of 194 FN episodes occurred between the years of 2013 and 2016 in 67 patients with leukemia. Clinical and microbiologic data were recorded.

RESULTS

MD-BSI occurred in 36 of 194 (18%) of FN episodes. Deescalation of empiric antibiotic therapy based on antibiotic susceptibilities was possible in 25 of 36 (69.4%) episodes. In those 25 episodes, where there was an opportunity to deescalate the antibiotic spectrum, it was clinically appropriate to do so in 19. Deescalation occurred in 9 (47.4%) of these episodes without complication. The remaining 10 patients received a median of 20 additional days of broad-spectrum antibiotic therapy (range, 12 to 30 d).

CONCLUSIONS

In our small cohort of patients, deescalation of antibiotic therapy based on antimicrobial susceptibilities did not result in complication. Larger prospective studies are needed to address the safety of deescalating antibiotic therapy in this population.

Effect of amphotericin B and voriconazole on the outgrowth of conidia of Aspergillus fumigatus followed by time-lapse microscopy

Studies of morphological measurements from the outgrowth of cells to a network of hyphae have been extended from Candida albicans (Nagy et al. in Appl Microbiol Biotechnol 98(11):5185-5194. https://doi.org/10.1007/s00253-014-5696-5 , 2014) to invasive conidiospores of Aspergillus fumigatus upon treatment with antifungal agents. The understanding of mycelial processes is important to optimize industrial processes such as fermentation and contributes to the fight against pathogenic fungi. This brief study combines TLS with digital image analysis. The TLS system was adapted to get information related to the adherence and growth dynamics of filamentous fungi. This approach was used earlier to distinguish among subphases of bacterial and fungal infections of mammal cells by detecting Mycoplasma infection in cell cultures causing serious damages in cell cultures. We describe changes in adherence, germination of spores, and hyphal growth of A. fumigatus, taking place in the absence and presence of amphotericin B (AMB) and voriconazole (VRC). These growth parameters were measured by TLS in CO₂ incubator under physiological Photomicrography by TLS and extended for a longer period of time up to several weeks combined with image analysis represents a comfortable and reliable means to characterize the growth dynamism of A. fumigatus. The most important observation of medical importance related to the pathomechanism of VRC was that it did not adhere to conidiospores, i.e. that it did not contribute to the attachment of spores to the growth surface, and did not prevent germination but delayed hypha protrusion and elongation. In contrast AMB adhered to conidia, inhibited germination, hypha elongation and branching. It was concluded that AMB was efficient against the therapy of growth but not against the prevention of fungal infection.

Early central line-associated blood stream infections in children with cancer pose a risk for premature catheter removal

AIM

This study examined the clinical characteristics of central line-associated blood stream infections occurring within 30 days after insertion versus later infections in paediatric cancer patients and the subsequent risk for premature catheter removal.

METHODS

This was a retrospective study of children aged 0-18 years who were diagnosed with cancer from 2013 to 2014 at the Astrid Lindgren Children Hospital, Sweden. Clinical and microbiology data for each patient were collected for 365 days after the central venous catheter (CVC) was inserted.

RESULTS

During the study period, 154 children received a CVC. The overall incidence of central line associated blood stream infections was 2.0 per 1000 catheter days. A total of 108 infectious episodes were identified in 44/154 (29%) patients. Of those, 15/44 children (29%) had an early infection within 30 days and alpha-haemolytic Streptococci and coagulase-negative Staphylococci dominated. Children with early infections were more likely to have a haematological malignancy and to need premature removal of the CVC due to repeated infections.

CONCLUSION

We observed a high prevalence of early CVC associated blood stream infection mainly in patients with haematological malignancies. Our study highlights the importance of preventive measures in reducing infections in paediatric cancer patients.

The in vitro effects of interferon-gamma, alone or in combination with amphotericin B, tested against the pathogenic fungi Candida albicans and Aspergillus fumigatus

Objective

Recent studies into the antifungal activity of NK-cells against the Aspergillus fumigatus have presented differing accounts on their mode of antifungal activity. One of these mechanisms proposed that NK-cells may kill the fungus via the direct effects of exposure to Interferon gamma (IFN-γ).

Results

In this study we investigated the direct antifungal effects of recombinant human IFN-γ against a range of pathogenic fungi by measuring cellular damage using an XTT-based assay and cell viability through plate counts. It was found that 32 pg/ml of IFN-γ exhibited a significant but small antifungal effect on A. fumigatus (p = 0.02), Aspergillus flavus (p = 0.04) and Saccharomyces cerevisiae (p = 0.03), inhibiting growth by 6, 11 and 17% respectively. No significant inhibitory effects were observed in Candida species (p > 0.05 for all species tested) or Cryptococus neoformans (p = 0.98). Short term exposure (3 h) to a combination of amphotericin B (1 µg/ml) and IFN-γ (32 pg/ml) increased the effectiveness of amphotericin B against A. fumigatus and S. cerevisiae but not Candida albicans. These data suggest that IFN-γ does not possess strong antifungal activity but can enhance the effect of amphotericin B under some testing conditions against Aspergillus species.

Risk factors for sepsis-related death in children and adolescents with hematologic and malignant diseases

BACKGROUND

The aim of this study was to elucidate risk factors for mortality after developing sepsis in pediatric patients with hematologic and malignant disorders.

METHODS

A total of 90 patients (43 boys, 47 girls) with various hematologic and malignant diseases who experienced sepsis between June 2006 and March 2014 were enrolled. Clinical and laboratory features of 134 episodes of sepsis observed in the 90 patients were compared between those with and without sepsis-related death which was defined as death within 14 days after sepsis.

RESULTS

Age at hospitalization, sex, and type of underlying disease did not differ between patients with and without sepsis-related death. Sepsis episode-based univariate analysis identified patients with a history of relapse or in a refractory state of underlying disease (p<0.01), those with high C-reactive protein concentrations (≥50 mg/L) at the beginning of fever (p<0.01), those who had undergone hematopoietic stem cell transplantation (p<0.01), and those who were forced to change initial antibiotics (p = 0.02) because of being at high risk of sepsis-related death. The former two factors were further confirmed by multivariate analysis. More than half (52.9%) the isolates from sepsis-related death were Gram-positive cocci resistant to β-lactam antibiotics, but susceptible to vancomycin.

CONCLUSION

It was found that a history of relapse, a refractory state of underlying disease, and high C-reactive protein concentrations at the beginning of fever were significant risk factors for mortality after developing sepsis. Survival rate of patients with risk factors raised in this study might be improved by early introduction of vancomycin.

Synthetic organotelluride compounds induce the reversal of Pdr5p mediated fluconazole resistance in Saccharomyces cerevisiae

Background

Resistance to fluconazole, a commonly used azole antifungal, is a challenge for the treatment of fungal infections. Resistance can be mediated by overexpression of ABC transporters, which promote drug efflux that requires ATP hydrolysis. The Pdr5p ABC transporter of Saccharomyces cerevisiae is a well-known model used to study this mechanism of antifungal resistance. The present study investigated the effects of 13 synthetic compounds on Pdr5p.

Results

Among the tested compounds, four contained a tellurium-butane group and shared structural similarities that were absent in the other tested compounds: a lateral hydrocarbon chain and an amide group. These four compounds were capable of inhibiting Pdr5p ATPase activity by more than 90%, they demonstrated IC₅₀ values less than 2 μM and had an uncompetitive pattern of Pdr5p ATPase activity inhibition. These organotellurides did not demonstrate cytotoxicity against human erythrocytes or S. cerevisiae mutant strains (a strain that overexpress Pdr5p and a null mutant strain) even in concentrations above 100 μM. When tested at 100 μM, they could reverse the fluconazole resistance expressed by both the S. cerevisiae mutant strain that overexpress Pdr5p and a clinical isolate of Candida albicans.

Conclusions

We have identified four organotellurides that are promising candidates for the reversal of drug resistance mediated by drug efflux pumps. These molecules will act as scaffolds for the development of more efficient and effective efflux pump inhibitors that can be used in combination therapy with available antifungals.