In the light of increasing antimicrobial resistance among gram-negative bacteria and the lack of new more potent antimicrobial agents, new strategies have been explored. Old antibiotics, such as ...colistin, temocillin, fosfomycin, mecillinam, nitrofurantoin, minocycline, and chloramphenicol, have attracted the attention since they often exhibit in vitro activity against multi-drug-resistant (MDR) gram-negative bacteria, such as Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. The current review provides a summary of the in vitro activity, pharmacokinetics and PK/PD characteristics of old antibiotics. In silico modelling was then performed using Monte Carlo simulation in order to combine all preclinical data with human pharmacokinetics and determine the probability of target (1-log kill in thigh/lung infection animal models) attainment (PTA) of different dosing regimens. The potential of clinical efficacy of a drug against severe infections by MDR gram-negative bacteria was considered when PTA was >95% at the epidemiological cutoff values of corresponding species. In vitro potent activity against MDR gram-negative pathogens has been shown for colistin, polymyxin B, temocillin (against E. coli and K. pneumoniae), fosfomycin (against E. coli), mecillinam (against E. coli), minocycline (against E. coli, K. pneumoniae, A. baumannii), and chloramphenicol (against E. coli) with ECOFF or MIC90 ≤ 16 mg/L. When preclinical PK/PD targets were combined with human pharmacokinetics, Monte Carlo analysis showed that among the old antibiotics analyzed, there is clinical potential for polymyxin B against E. coli, K. pneumoniae, and A. baumannii; for temocillin against K. pneumoniae and E. coli; for fosfomycin against E. coli and K. pneumoniae; and for mecillinam against E. coli. Clinical studies are needed to verify the potential of those antibiotics to effectively treat infections by multi-drug resistant gram-negative bacteria.
Azole-resistant Aspergillus fumigatus is emerging worldwide. Reference susceptibility testing methods are technically demanding and no validated commercial susceptibility tests for moulds currently ...exist. In this multicentre study a 4-well azole-containing screening agar method was evaluated using clinically relevant isolates.
Forty WT and 39 cyp51A mutant A. fumigatus G54 (n = 10), M220 (n = 10), TR34/L98H (n = 9) and TR46/Y121F/T289A (n = 10) were tested individually and as simulated mixed samples (sampling 4 WT and 1 mutant colonies). EUCAST MICs were determined following E.Def 9.3. In-house and commercial 4-well plates containing agars supplemented with 4 mg/L itraconazole, 1 mg/L voriconazole, 0.5 mg/L posaconazole and no antifungal, respectively, were evaluated. Growth was scored (0-3) by two independent observers in three laboratories. Inter-plate, inter-observer, essential and categorical agreement, sensitivity and specificity were calculated.
CYP51A genotype and antifungal compound-specific MICs and growth patterns were documented. The inter-observer agreement was excellent with 86%-99% identical scores (range 80%-100%) for both plates. The qualitative agreement (no growth versus growth) was excellent (median 95%-100%, range 87%-100%, overall). The overall sensitivity and specificity for the 4-well plate (no growth versus growth) was 99% (range 97%-100%) and 99% (95%-100%), respectively. The sensitivity for simulated WT/mutant specimens was 94% (range 83%-100%) for the WT-TR34/L98H combination, but 100% for the WT/G54W combination. The performance remained unchanged using only itraconazole- and voriconazole-containing agars, but was lower for the other combinations.
Implementation of the 4-well screening plate in routine laboratories will allow easy and reliable detection of the most common azole-resistant A. fumigatus.
The severe respiratory insufficiency observed during COVID-19 infection may not be directly related to a cytopathogenic effect induced by the virus itself, but to an exaggerated and inappropriate ...immune response. In an effort to reduce the severity of organ dysfunction, including respiratory insufficiency, monoclonal antibodies (Mabs) that block the interleukin-6 receptor, such as tocilizumab, sarilumab, and siltuximab, are under investigation for the treatment of COVID-19. However, blocking of just one of the many cytokines involved in the inflammatory reaction may not slow down the magnitude of the process. Since timing is important, the immune deficiency induced by IL6 blockade at the late immunodeficiency phase of sepsis that follows the initial inflammatory response may be detrimental. Finally, monitoring the degree and duration of IL6 blockade may be challenging because of the long half-life of Mabs (2–3 weeks). Pro- and anti-inflammatory cytokines act through a common JAK-STAT signaling pathway, which can be inhibited by JAK-STAT inhibitors. Ruxolitinib, a tyrosine kinase inhibitor selective for JAK1, 2, blocks many pro- and anti-inflammatory cytokines including IL6. Ruxolitinib has favorable pharmacodynamics and an acceptable safety profile. The short half-life (4–6 h) of the drug offers the opportunity for ideal monitoring of the degree and duration of cytokine blocking, simply by the adjusting dose and duration of therapy. From a theoretical point of view, the balanced control of cytokine blockade throughout the course of the septic process should be the cornerstone of modern management. According to this hypothesis, maximization of blocking should be attempted at the phase of hyper-inflammation for preventing severe organ damage, while pro-inflammatory blockade should be minimized at the late phase of immunoparalysis for prevention of secondary infections. Based on the above considerations, we consider that the efficacy and safety of this drug deserves testing in the context of a controlled randomized trial.
Commercial tests are often employed in clinical microbiology laboratories for antifungal susceptibility testing of filamentous fungi. Method-dependent epidemiological cutoff values (ECVs) have been ...defined in order to detect non-wild-type (NWT) isolates harboring resistance mechanisms. We reviewed the literature in order to find studies where commercial methods were used to evaluate for in vitro susceptibility of filamentous fungi and assess their ability to detect NWT isolates according to the available ECVs. Data were found for the gradient concentration strips Etest and MIC Test Strips (MTS), broth microdilution Sensititre YeastOne (SYO), Micronaut-AM and the agar dilution VIPcheck assays. Applying itraconazole, voriconazole and posaconazole Etest ECVs for
, Etest was able to detect 90.3% (84/93), 61.2% (90/147) and 86% (31/36) of isolates with known
mutations, respectively. Moreover, Etest also was able to detect 3/3
mutants using caspofungin ECVs and 2/3 micafungin mutant isolates. Applying the voriconazole and posaconazole SYO ECVs, 57.7% (67/116) and 100% (47/47) of mutants with known
substitutions were classified as NWT, respectively. VIPcheck detected 90.3% (159/176), 80.1% (141/176) and 66% (141/176)of mutants via itraconazole, voriconazole and posaconazole, respectively, whereas Micronaut-AM detected 88% (22/25). In conclusion, Etest posaconazole and itraconazole, as well as micafungin and caspofungin ECVs, detected
mutants. On the other hand, while the posaconazole SYO ECV was able to detect
mutants, similar data were not observed with the SYO voriconazole ECV.
Abstract
Background
Systemic infections caused by the black yeast-like fungus
Exophiala dermatitidis
are rare, but are associated with high mortality especially in immunocompromised patients. We ...report the first case of
E. dermatitidis
fungemia in a premature extremely low birth weight (ELBW) neonate who succumbed despite antifungal therapy with liposomal amphotericin (AMB) and fluconazole. A systematic review of all fungemia cases due to
E. dermatitidis
was also conducted aiming for a better understanding of the risk factors, treatment strategies and outcomes.
Case presentation
A male, ELBW premature neonate, soon after his birth, developed bradycardia, apnoea and ultimately necrotizing enterocolitis with intestinal perforation requiring surgical intervention. Meanwhile, he had also multiple risk factors for developing bloodstream infection, such as intubation, mechanical ventilation, central venous catheter (CVC), parenteral nutrition, empirical and prolonged antibiotic use. His blood cultures were positive, firstly for
Acinetobacter junii
and then for
Klebsiella pneumoniae
together with
E. dermatitidis
while on fluconazole prophylaxis and antibiotic empiric therapy. Despite the treatment with broad spectrum antibiotics, liposomal AMB and fluconazole, the newborn succumbed. A literature review identified another 12
E. dermatitidis
bloodstream infections, mainly in patients with hematologic malignancies and solid organ transplant recipients (61%), with overall mortality 38% despite CVC removal and antifungal therapy.
Conclusions
Due to the rarity of
E. dermatitidis
infections, little is known about the characteristics of this yeast, the identification methods and the optimal therapy. Identification by common biochemical tests was problematic requiring molecular identification. Resolution of neonatal fungemia is difficult despite proper antifungal therapy especially in cases with multiple and severe risk factors like the present one. Therapeutic intervention may include CVC removal and treatment for at least 3 weeks with an azole (itraconazole or fluconazole after susceptibility testing) or AMB monotherapy but not echinocandins or AMB plus azole combination therapy.
The objectives of this study were to investigate the incidence of candidemia, as well as the factors associated with Candida species distribution and fluconazole resistance, among patients admitted ...to the intensive care unit (ICU) during the COVID-19 pandemic, as compared to two pre-pandemic periods. All patients admitted to the ICU due to COVID-19 from March 2020 to October 2021, as well as during two pre-pandemic periods (2005–2008 and 2012–2015), who developed candidemia, were included. During the COVID-19 study period, the incidence of candidemia was 10.2%, significantly higher compared with 3.2% and 4.2% in the two pre-pandemic periods, respectively. The proportion of non-albicans Candida species increased (from 60.6% to 62.3% and 75.8%, respectively), with a predominance of C. parapsilosis. A marked increase in fluconazole resistance (from 31% to 37.7% and 48.4%, respectively) was also observed. Regarding the total patient population with candidemia (n = 205), fluconazole resistance was independently associated with ICU length of stay (LOS) before candidemia (OR 1.03; CI: 1.01–1.06, p = 0.003), whereas the presence of shock at candidemia onset was associated with C. albicans (OR 6.89; CI: 2.2–25, p = 0.001), and with fluconazole-susceptible species (OR 0.23; CI: 0.07–0.64, p = 0.006). In conclusion, substantial increases in the incidence of candidemia, in non-albicansCandida species, and in fluconazole resistance were found in patients admitted to the ICU due to COVID-19, compared to pre-pandemic periods. At candidemia onset, prolonged ICU LOS was associated with fluconazole-resistant and the presence of shock with fluconazole-susceptible species.
Background
Although voriconazole reached the bedside 10 years ago and became the standard care in the treatment of invasive aspergillosis, reliable clinical breakpoints are still in high demand. ...Moreover, this has increased due to the recent emergence of azole resistance.
Methods
Four clinical wild-type and non-wild-type A. fumigatus isolates with voriconazole CLSI MICs in the range of 0.125–2 mg/L were tested in an in vitro pharmacokinetic (PK)/pharmacodynamic (PD) model. Mouse PK was simulated and in vitro data were compared with in vivo outcome. Human PK was simulated and susceptibility breakpoints and trough levels required for optimal treatment were determined for the CLSI and EUCAST methods after 48 h and the gradient concentration MIC test strip (MTS) method after 24 h using the in vitro PK/PD relationship and Monte Carlo simulation.
Results
The in vitro PK/PD target (95% CI) associated with 50% of the maximal antifungal activity (EC50) was 28.61 (16.18–50.61), close to the in vivo EC50 of 14.67 (9.31–21.58) fAUC0–24/CLSI MIC. When human PK was simulated, the EC50 was 24.7 (17.9–35.6) fAUC0–12/CLSI MIC and it was associated with 6 week survival in clinical studies of invasive pulmonary aspergillosis. Target attainment rates were ≤5% (0%–24%), 42% (16%–58%), 68% (54%–75%) and ≥79% (73%–86%) for isolates with CLSI MICs ≥2, 1, 0.5 and ≤0.25 mg/L, respectively. A trough/CLSI MIC ratio of 2 was required for optimal treatment. The susceptible/intermediate/resistant breakpoints were determined to be 0.25/0.5–1/2 mg/L for CLSI, 0.5/1–2/4 mg/L for EUCAST and 0.25/0.375–1/1.5 mg/L for MTS.
Conclusions
These susceptibility breakpoints and target values for therapeutic drug monitoring could be used to optimize voriconazole therapy against A. fumigatus.
The in vitro/in vivo correlation of antifungal combination testing is necessary in order to assess the efficacy of combination regimens. We, therefore, attempted to correlate in vitro chequerboard ...testing of posaconazole (POS) and amphotericin B (AMB) with the in vivo outcome of combination therapy against experimental candidiasis in a neutropenic murine model. The AMB + POS combination was tested against a
isolate. In vitro, a broth microdilution 8 × 12 chequerboard method with serial two-fold drug dilutions was used. In vivo, CD1 female neutropenic mice with experimental disseminated candidiasis were treated with i.p. AMB and p.o. POS alone and in combination at three effective doses (ED20, ED50 and ED80 corresponding to 20%, 50% and 80% of maximal effect, respectively). CFU/kidneys after 2 days were determined. The pharmacodynamic interactions were assessed based on Bliss independence interaction analysis. In vitro, a Bliss antagonism of -23% (-23% to -22%) was observed at 0.03-0.125 mg/L of AMB with 0.004-0.015 mg/L of POS, while a Bliss synergy of 27% (14%-58%) was observed at 0.008-0.03 mg/L of AMB with 0.000015-0.001 mg/L of POS. In vivo, Bliss synergy (13 ± 4%) was found when an AMB ED20 of 1 mg/kg was combined with all POS ED 0.2-0.9 mg/kg, while Bliss antagonism (35-83%) was found for the combinations of AMB ED50 2 mg/kg and ED80 3.2 mg/kg with POS ED80 of 0.9 mg/kg. Free drug serum levels of POS and AMB in in vivo synergistic and antagonistic combinations were correlated with the in vitro synergistic and antagonistic concentrations, respectively. Both synergistic and antagonistic interactions were found for the AMB + POS combination. POS compromised the efficacy of high effective AMB doses and enhanced low ineffective AMB doses. In vitro concentration-dependent interactions were correlated with in vivo dose-dependent interactions of the AMB + POS combination. In vivo interactions occurred at free drug serum levels close to in vitro interacting concentrations.
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