Triazole and echinocandin MIC distributions with epidemiological cutoff values for differentiation of wild-type strains from non-wild-type strains of six uncommon species of Candida

Otomycosis: The foremost aetiological agent causing otitis externa and the antifungal susceptibility pattern in North-Western Iran

BACKGROUND

Otomycosis is considered a recurring fungal ear infection. The external auditory canal provides an appropriate and optimal situation for fungal growth.

OBJECTIVES

The study aimed to identify the causative agents of otomycosis and determine corresponding antifungal drug susceptibility patterns in north-western Iran.

METHODS

From October 2020 until November 2021, 200 patients attended an otolaryngology referral centre with otitis externa, and their ear discharge and debris were examined and cultured. The identification of the fungal agents was implemented by polymerase chain reaction-restriction fragment length polymorphism and sequencing. In vitro antifungal susceptibility testing of the isolates was conducted in accordance with the CLSI broth microdilution protocols.

RESULTS

The prevalence of otomycosis was measured 50.5% (n = 101/200). The majority of patients were in their forties (n = 35, 34.6%) and female (n = 57, 56.4%), and the most prevalent symptom was otalgia (56.4%). The most underlying factor was remarked manipulation employing a cotton swab (65.3%). Regarding fungus, Aspergillus section Nigri (58.57%) was the foremost isolate, followed by Aspergillus section Flavi (19.23%) and Candida parapsilosis (14.96%). The predominance of Aspergillus isolates had minimal in vitro sensitivity to tioconazole and nystatin. Candida species represented higher geometric mean minimum inhibitory concentrations (MIC) against nystatin. The MIC of three Aspergillus species isolates shown above the epidemiologic cut-off values (ECV) against itraconazole.

CONCLUSIONS

Otomycosis incidence surpassed in comparison with the previous study as the most common cause of otitis externa. The MIC distribution of Aspergillus species isolates against triazole antifungals is close to the defined ECVs and likely outrun it over time.

In Vitro Assessment of Azole and Amphotericin B Susceptibilities of Malassezia spp. Isolated from Healthy and Lesioned Skin

Malassezia yeasts have recently gained medical importance as emerging pathogens associated with a wide range of dermatological and systemic infections. Since standardized methods for in vitro antifungal susceptibility testing have not yet been established for Malassezia spp., related diseases are always treated empirically. As a result, a high rate of recurrence and decreased antifungal susceptibility have appeared. Thus, the aims of the study were to assess and analyze the in vitro susceptibility of Malassezia isolated from pityriasis versicolor (PV) lesions and healthy controls. A total of 58 Malassezia strains isolated from PV patients and healthy controls were tested. In vitro antifungal susceptibility testing was conducted using the CLSI broth microdilution with some modifications. Candida spp. criteria established in accordance with CLSI guidelines were used for data interpretation. Ketoconazole and posaconazole seemed to be the most effective molecules against Malassezia species. However, considerable percentages of itraconazole, fluconazole, and amphotericin B ‘‘resistant’’ strains (27.6%, 29.3%, and 43.1%, respectively) were revealed in this study. Malassezia furfur, M. sympodialis, and M. globosa showed different susceptibility profiles to the drugs tested. These results emphasize the importance of accurately identifying and evaluating the antifungal susceptibility of Malassezia species in order to guide a specific and effective treatment regimen.

Spectrum and Antifungal Resistance of Candidemia in Neonates With Early- and Late-Onset Sepsis in Pakistan

BACKGROUND

Neonatal candidemia leads to high morbidity and mortality in developing countries. We studied the trends, spectrum and antifungal resistance in neonatal candidemia isolates from the year 2014 to 2019.

METHODS

This was a cross-sectional study conducted at the Aga Khan University, Pakistan. Neonates with positive blood cultures with Candida species were retrospectively identified from the laboratory database (2014-2018) and prospectively in 2019 where clinical information was also collected as part of routine laboratory reporting.

RESULTS

We identified 669 neonates with Candida species in blood cultures. Three hundred forty-six neonates had early-onset disease (EOD age ≤7 days) and 323 had late-onset disease (LOD age >7 days). Non-albicans Candida species (86.7%) were predominant versus C. albicans (13.3%; P-value 0.024) with Candida tropicalis being most common in both EOD and LOD. Candida pelliculosa and Candida guilliermondii were associated with EOD and C. albicans with LOD. Isolation of fluconazole nonsusceptible non-albicans Candida species was significantly higher in early-onset (5.9%) versus late-onset (2%) neonatal candidemia (P-value 0.005; crude odds ratio [COR] 2.73, 95% CI: 1.34-5.53). LOD in neonates was more likely associated with the use of vancomycin (COR 3.89, 95% CI: 1.39-10.89). EOD was more likely seen in patients with vaginal delivery (COR 4.16, 95% CI: 1.42-12.23) and in neonates with respiratory distress leading to intensive care unit admission (COR 3.31, 95% CI: 1.05-10.42).

CONCLUSIONS

Non-albicans Candida species were increasingly isolated from neonates with candidemia during recent years from Pakistan. Amphotericin remains first-line option for neonatal candidemia in our setting as fluconazole nonsusceptible Candida species are commonly isolated.

Molecular and genetic basis of azole antifungal resistance in the opportunistic pathogenic fungus Candida albicans

Candida albicans is an opportunistic yeast and the major human fungal pathogen in the USA, as well as in many other regions of the world. Infections with C. albicans can range from superficial mucosal and dermatological infections to life-threatening infections of the bloodstream and vital organs. The azole antifungals remain an important mainstay treatment of candidiasis and therefore the investigation and understanding of the evolution, frequency and mechanisms of azole resistance are vital to improving treatment strategies against this organism. Here the organism C. albicans and the genetic changes and molecular bases underlying the currently known resistance mechanisms to the azole antifungal class are reviewed, including up-regulated expression of efflux pumps, changes in the expression and amino acid composition of the azole target Erg11 and alterations to the organism's typical sterol biosynthesis pathways. Additionally, we update what is known about activating mutations in the zinc cluster transcription factor (ZCF) genes regulating many of these resistance mechanisms and review azole import as a potential contributor to azole resistance. Lastly, investigations of azole tolerance in C. albicans and its implicated clinical significance are reviewed.

Candidemia and Invasive Candidiasis

Invasive candidiasis (IC) is a collective term that refers to a group of infectious syndromes caused by a variety of species of Candida, 6 of which cause most cases globally. Candidemia is probably the most commonly recognized syndrome associated with IC; however, Candida can cause invasive infection of any organ, especially visceral organs, vasculature, bones and joints, the eyes and central nervous system. Targeted prevention and empirical therapy are important interventions for patients at high risk for IC, and the current approach should be based on a combination of clinical risk factors and non-culture-based diagnostics, when available.

In vitro activity of rezafungin against common and rare Candida species and Saccharomyces cerevisiae

BACKGROUND

Rezafungin is a novel echinocandin with excellent activity against common Candida species; however, limited data are available regarding rare Candida species.

METHODS

We determined the in vitro susceptibility of 689 clinical isolates of 5 common and 19 rare Candida species, as well as Saccharomyces cerevisiae. The activity of rezafungin was compared with that of anidulafungin, caspofungin, micafungin, amphotericin B and fluconazole, using CLSI broth microdilution methodology (Fourth Edition: M27).

RESULTS

Rezafungin MIC90 values were 0.06 mg/L for Candida albicans (n=125), Candida tropicalis (n=51), Candida dubliniensis (n=22), Candida inconspicua (n=41), Candida sojae (n=10), Candida lipolytica (n=10) and Candida pulcherrima (n=10), 0.12 mg/L for Candida glabrata (n=81), Candida krusei (n=53), Candida kefyr (n=52) and Candida fabianii (n=15), 0.25 mg/L for Candida lusitaniae (n=46) and Candida auris (n=19), 0.5 mg/L for Candida metapsilosis (n=15) and S. cerevisiae (n=21), 1 mg/L for Candida orthopsilosis (n=15) and Candida guilliermondii (n=27) and 2 mg/L for Candida parapsilosis sensu stricto (n=59). Caspofungin MIC90 values were 0.25-2 mg/L for all species, while micafungin and anidulafungin MIC90 values were similar to those of rezafungin. Fluconazole resistance was found in C. albicans (5.6%) and C. glabrata (4.9%); rezafungin was effective against these isolates as well. Amphotericin B MIC values did not exceed 2 mg/L.

CONCLUSIONS

Rezafungin showed excellent in vitro activity against both WT and azole-resistant Candida species, as well as against S. cerevisiae. Rezafungin had similar activity to other echinocandins (excluding caspofungin) against common Candida species and, notably, against clinically relevant uncommon Candida species.

Epidemiology of bloodstream Candida species in a Spanish tertiary care hospital as a guide for implementation of T2MR (T2CANDIDA®) for rapid diagnosis of candidemia

The aim of this work was to study the epidemiology of candidemia in our hospital in order to determine whether the T2MR system might be a useful tool for early diagnosis of candidemia in selected units. We perform a retrospective review of all candidemia episodes registered in the last 12 years in selected units of our hospital in adult and pediatric patients. Candida species and antifungal susceptibility patterns were registered. A total of 686 isolates were registered, of which 625 were infections due to the five most common species of Candida. C. albicans (45.6%) and C. parapsilosis (33.1%) were the predominant species found in our institution. In adults these species were closely followed by C. glabrata (12-21%) in all units. While in pediatric medical and intensive care units (PICU), these species were followed by other uncommon yeasts. Resistance rates to triazoles were low in C. albicans and C. parapsilosis. In C. glabrata and C. tropicalis the resistance rates to fluconazole ranged from 10.86 to 6.67%. Resistance rates for echinocandins were very low and all strains were susceptible to amphotericin B. T2Candida® might be useful to guide antifungal targeted treatment and discontinuation of antifungal empirical treatment in those units where the five most common Candida species represent more than the ninety percent of the isolates. The selection of medical and surgical units should be based on local epidemiology and antifungal susceptibility patterns. Incidence should be taken into account in order to make clinical decisions based on negative results.

LAY ABSTRACT

T2Candida® might be useful selectively in clinical units according to their local epidemiology, antifungal resistance patterns, and incidence of candidemia. It optimizes the clinical value of positive results supporting decisions about targeted therapies or discontinuations based on negative results.

Comparative evaluation of E-test and CLSI methods for Itraconazole, Fluconazole and Ketoconazole susceptibilities of Microsporum canis strains

The incidence of resistance to antifungal agents for dermatophytes is increasing, but most of the methods currently available to test the antifungal susceptibility of Microsporum canis still require standardization. The aims of this study were: (i) to evaluate the antifungal susceptibility of M. canis strains recovered from animals to ketoconazole (KTZ), fluconazole (FLZ) and itraconazole (ITZ) using a modified CLSI broth microdilution (CLSI M38-A2-BMD) and the E-test® protocols and (ii) to estimate the agreement between the methods. Tentative azole epidemiological cutoff values (ECVs) were also proposed in order to interpret the results of in vitro susceptibility tests and to establish the agreement between the E-test and CLSI BMD methods. A total of forty clinical M. canis strains from animals with skin lesions were tested, and the essential (EA) and categorical agreement (CA) between the two methods were determined. KTZ displayed the lowest MIC values, while ITZ and FLZ the highest. The ECV for KTZ and ITZ were 4 μg/ml, while those of FLZ was 64 μg/ml. Based on ECVs, about 88% of M. canis strains were susceptible to all azoles being a cross-resistance with ITZ-FLZ registered for one strain. A total of five M. canis strains showed MIC > ECV for FLZ using CLSI, while one strain showed MIC > ECV for ITZ using both tests. KTZ, ITZ and FLZ showed EA ranging from 92.5 to 95%, for all azoles and CA > 97% except for FLZ (87.5%). The good CA between the E-test and the CLSI BMD provides evidence of the reliability of the former method to test the antifungal susceptibility of M. canis for ITZ and KTZ and not for FLZ.

MIC distributions for amphotericin B, fluconazole, itraconazole, voriconazole, flucytosine and anidulafungin and 35 uncommon pathogenic yeast species from the UK determined using the CLSI broth microdilution method

Background

Epidemiological cut-off values and clinical interpretive breakpoints have been developed for a number of antifungal agents with the most common Candida species that account for the majority of infections due to pathogenic yeasts species. However, less-common species, for which susceptibility data are limited, are increasingly reported in high-risk patients and breakthrough infections.

Methods

The UK National Mycology Reference Laboratory performs routine antifungal susceptibility testing of clinical yeast isolates submitted from across the UK. Between 2002 and 2016, >32 000 isolates representing 94 different yeast species were referred to the laboratory. Here we present antifungal susceptibility profiles generated over this period for amphotericin B, fluconazole, voriconazole, itraconazole, anidulafungin and flucytosine against 35 species of uncommon yeast using CLSI methodologies. MIC data were interpreted against epidemiological cut-off values and clinical breakpoints developed with Candida albicans, in order to identify species with unusually skewed MIC distributions that potentially indicate resistance.

Results

Potential resistance to at least one antifungal agent (>10% of isolates with MICs greater than the epidemiological cut-off or clinical breakpoint) was evidenced for 29/35 species examined here. Four species exhibited elevated MICs with all of the triazole antifungal drugs against which they were tested, and 21 species exhibited antifungal resistance to agents from at least two different classes of antifungal agent.

Conclusions

This study highlights a number of yeast species with unusual MIC distributions and provides data to aid clinicians in deciding which antifungal regimens may be appropriate when confronted with infections with rarer yeasts.

Fluconazole Resistance in Isolates of Uncommon Pathogenic Yeast Species from the United Kingdom

The triazole drug fluconazole remains one of the most commonly prescribed antifungal drugs, both for prophylaxis in high-risk patients and also as a second-line treatment option for invasive Candida infections. Established susceptibility profiles and clinical interpretive breakpoints are available for fluconazole with Candida albicans, Candida glabrata, Candida tropicalis, and Candida parapsilosis, which account for the majority of infections due to pathogenic yeast species. However, less common species for which only limited susceptibility data are available are increasingly reported in high-risk patients and from breakthrough infections. The UK National Mycology Reference Laboratory performs routine antifungal susceptibility testing of clinical isolates of pathogenic yeast submitted from across the United Kingdom. Between 2002 and 2016, ∼32,000 isolates were referred, encompassing 94 different yeast species. Here, we present fluconazole antifungal susceptibility data generated using a CLSI methodology over this 15-year period for 82 species (2,004 isolates) of less common yeast and yeast-like fungi, and amphotericin B, fluconazole, itraconazole, voriconazole, posaconazole, and anidulafungin, with members of the Nakaseomyces clade (C. glabrata, Candida nivariensis, and Candida bracarensis). At least 22 different teleomorph genera, comprising 45 species, exhibited high MICs when tested with fluconazole (>20% of isolates with MICs higher than the clinical breakpoint [≥8 mg/liter] proposed for C. albicans). Since several of these species have been reported anecdotally from breakthrough infections and therapeutic failures in patients receiving fluconazole, the current study underscores the importance of rapid and accurate yeast identification and may aid clinicians dealing with infections with rarer yeasts to decide whether fluconazole would be appropriate.

Efficacy of humanized single large doses of caspofungin on the lethality and fungal tissue burden in a deeply neutropenic murine model against Candida albicans and Candida dubliniensis

Background

Echinocandins are the first-line therapy for treatment of invasive Candida infections, but the mortality rate remains high, calling for novel strategies. Giving single larger echinocandin doses infrequently is an alternative regimen. Our aim was to test this novel approach in a neutropenic murine model.

Materials and methods

We compared the in vivo efficacy of single 10 and 40 mg/kg of caspofungin (2.5× and 10× the normal humanized dose) to that of the same cumulative doses of daily 2 and 8 mg/kg doses for 5 days against 2 each of wild-type C. albicans and C. dubliniensis as well as echinocandin resistant C. albicans. As a comparator, we tested daily 1 mg/kg amphotericin B.

Results

In lethality experiments, all caspofungin and amphotericin B regimens improved survival against wild-type C. albicans and C. dubliniensis clinical isolates (P<0.0001) and decreased the mean fungal kidney burdens of both species compared to controls. However, fungal kidney burden decreases were not always statistically significant, especially with single 10 or 40 mg/kg caspofungin doses. Amphotericin B was the least active drug against wild-type C. albicans. Against echinocandin-resistant strains, monodose 40 mg/kg caspofungin and 1 mg/kg of daily amphotericin B were effective in lethality experiments. Although, significant kidney CFU decreases were never found, except for amphotericin B against one of the isolates (p<0.05 at day 3 and p<0.001 at day 6).

Conclusion

Single 40 mg/kg caspofungin and 1 mg/kg amphotericin B proved to be effective in the lethality experiments against wild-type and echinocandin-resistant C. albicans and wild-type C. dubliniensis. This was not always shown regarding fungal tissue burdens. Single caspofungin doses used in mice in this study are attainable in humans as well, suggesting a potential place of this dosing strategy not only in prevention but also in curative treatment of evolved invasive Candida infections.

Epidemiology and antifungal susceptibility testing of non-albicansCandida species colonizing mucosae of HIV-infected patients in Yaoundé (Cameroon)

Non-albicans Candida (NAC) species have emerged as potent pathogenic yeasts among HIV-infected patients. Authors evaluated the epidemiology and antifungal susceptibility testing of non-albicansCandida species colonizing Yaoundé (capital of the Republic of Cameroon, Central Africa) HIV-infected patients. The mucosal specimens were collected and submitted to the mycological diagnosis. Yeast isolates were identified by the Matrix Assisted Laser Desorption Ionisation - Time of Flight Mass Spectrometry (MALDI-TOF MS). The antifungal susceptibility testing was achieved by the CLSI-M27 protocols, and the interpretation of clinical break points (CBPs) and epidemiological cutoff values were in accordance with the CLSI-M60 and M59 recommendations. Four hundred and two patients were recruited and 1218 samples collected. The colonisation frequency was 24.1% and 304 yeasts isolated. Yeast isolates were 113 (37.2%) C. albicans, 2 (0.7%) C. africana and 172 (56.6%) NAC isolates. The NAC isolates were grouped into 13 species including C. krusei (18.1%), C. glabrata (10.9%), C. tropicalis (8.5%) and C. parapsilosis (5.9%) as the major ones. All the isolates appeared to be wild-type for amphotericin B and itraconazole. One (1/33) isolate of C. glabrata was resistant to fluconazole. C. arapsilosis isolates appeared all susceptible to fluconazole. C. tropicalis isolates presented 50% (13/26) resistance to fluconazole. The achieved results bring out new insights about epidemiology of NAC species in Cameroon. The results also highlight the resistance of NAC species to current antifungal drugs.

Resistant cutoff values and optimal scheme establishments for florfenicol against Escherichia coli with PK-PD modeling analysis in pigs

Florfenicol, a structural analog of thiamphenicol, has broad-spectrum antibacterial activity against gram-negative and gram-positive bacteria. This study was conducted to investigate the epidemiological, pharmacokinetic-pharmacodynamic cutoff, and the optimal scheme of florfenicol against Escherichia coli (E. coli) with PK-PD integrated model in the target infectious tissue. 220 E. coli strains were selected to detect the susceptibility to florfenicol, and a virulent strain P190, whose minimum inhibitory concentration (MIC) was similar to the MIC₅₀ (8 μg/ml), was analyzed for PD study in LB and ileum fluid. The MIC of P190 in the ileum fluid was 0.25 times lower than LB. The ratios of MBC/MIC were four both in the ileum and LB. The characteristics of time-killing curves also coincided with the MBC determination. The recommended dosages (30 mg/kg·body weight) were orally administrated in healthy pigs, and both plasma and ileum fluid were collected for PK study. The main pharmacokinetics (PK) parameters including AUC_24 hr , AUC_0-∞ , T_max , T_1/2 , C_max , CL_b, and K_e were 49.83, 52.33 μg*h/ml, 1.32, 10.58 hr, 9.12 μg/ml, 0.50 L/hr*kg, 0.24 hr^-1 and 134.45, 138.71 μg*hr/ml, 2.05, 13.01 hr, 16.57 μg/ml, 0.18 L/hr*kg, 0.14 hr^-1 in the serum and ileum fluid, respectively. The optimum doses for bacteriostatic, bactericidal, and elimination activities were 29.81, 34.88, and 36.52 mg/kg for 50% target and 33.95, 39.79, and 42.55 mg/kg for 90% target, respectively. The final sensitive breakpoint was defined as 16 μg/ml. The current data presented provide the optimal regimens (39.79 mg/kg) and susceptible breakpoint (16 μg/ml) for clinical use, but these predicted data should be validated in the clinical practice.

Comparison of Killing Activity of Micafungin Against Six Candida Species Isolated from Peritoneal and Pleural Cavities in RPMI-1640, 10 and 30% Serum

Currently echinocandins are recommended in Candida peritonitis and pleuritis. We determined micafungin killing rates (k values) at therapeutic concentrations (0.25-2 mg/L) in RPMI-1640 with and without 10 and 30% serum mimicking in vivo conditions against six Candida species isolated from peritoneal and pleural fluid. In RPMI-1640, micafungin was fungicidal against C. glabrata, C. krusei and C. kefyr within 2.27 ± 10.68, 2.69 ± 10.29 and 3.10 ± 4.41 h, respectively, while was fungistatic against C. albicans, C. tropicalis and C. parapsilosis. In 10% serum, ≥ 0.25, ≥ 0.5, ≥ 0.5 and ≥ 1 mg/L micafungin produced positive k values (killing) for all C. albicans, C. glabrata, C. kefyr and C. krusei, respectively. In 30% serum, 2 mg/L micafungin produced killing against all C. albicans, C. glabrata and C. kefyr isolates, but was ineffective against C. krusei, C. parapsilosis and 2 of 3 C. tropicalis. Micafungin exposure should be increased against non-albicans species to eradicate fungi from peritoneal and pleural cavities.

Antifungal Susceptibility and Clinical Outcome in Neonatal Candidiasis

BACKGROUND

Invasive candidiasis is an important cause of sepsis in extremely low birth weight infants (ELBW, < 1000 g), is often fatal, and frequently results in neurodevelopmental impairment (NDI) among survivors. We sought to assess the antifungal minimum inhibitory concentration (MIC) distribution for Candida in ELBW infants and evaluate the association between antifungal resistance and death or NDI.

METHODS

This was a secondary analysis of a National Institute of Child Health and Human Development Neonatal Research Network study. MIC values were determined for fluconazole, amphotericin B and micafungin. NDI was assessed at 18-22 months adjusted age using the Bayley Scales of Infant Development. An infant was defined as having a resistant Candida isolate if ≥ 1 positive cultures from normally sterile sites (blood, cerebrospinal fluid, or urine) were resistant to ≥ 1 antifungal agent. In addition to resistance status, we categorized fungal isolates according to MIC values (low and high). The association between death/NDI and MIC level was determined using logistic regression, controlling for gestational age and Bayley Scales of Infant Development (II or III).

RESULTS

Among 137 ELBW infants with IC, MICs were determined for 308 isolates from 110 (80%) infants. Three Candida isolates from 3 infants were resistant to fluconazole. None were resistant to amphotericin B or micafungin. No significant difference in death, NDI, or death/NDI between groups with low and high MICs was observed.

CONCLUSIONS

Antifungal resistance was rare among infecting Candida isolates, and MIC level was not associated with increased risk of death or NDI in this cohort of ELBW infants.

Optimal Regimens and Cutoff Evaluation of Tildipirosin Against Pasteurella multocida

Pasteurella multocida (PM) can invade the upper respiratory tract of the body and cause death and high morbidity. Tildipirosin, a new 16-membered-ring macrolide antimicrobial, has been recommended for the treatment of respiratory diseases. The objective of this research was to improve the dose regimes of tildipirosin to PM for reducing the macrolides resistance development with the pharmacokinetic/pharmacodynamic (PK/PD) modeling approach and to establish an alternate cutoff for tildipirosin against PM. A single dose (4 mg/kg body weight) of tildipirosin was administered via intramuscular (i.m.) and intravenous (i.v.) injection to the pigs. The minimum inhibitory concentration (MIC) values of clinical isolates (112) were measured in the range of 0.0625–32 μg/ml, and the MIC₅₀ and MIC₉₀ values were 0.5 and 2 μg/ml, respectively. The MIC of the selected PM04 was 2 and 0.5 μg/ml in the tryptic soy broth (TSB) and serum, respectively. The main pharmacokinetic (PK) parameters including the area under the curve at 24 h (AUC_{24 h}), AUC, terminal half-life (T_1/2), the time to peak concentration (T_max), peak concentration (C_max), relative total systemic clearance (CL_b), and the last mean residence time (MRT_last) were calculated to be 7.10, 7.94 μg^∗h/ml, 24.02, NA h, NA μg/ml, 0.46 L/h^∗kg, 8.06 h and 3.94, 6.79 μg^∗h/ml, 44.04, 0.25 h, 0.98 μg/ml, 0.43 L/h^∗kg, 22.85 h after i.v. and i.m. induction, respectively. Moreover, the bioavailability of i.m. route was 85.5%, and the unbinding of tildipirosin to serum protein was 78%. The parameters AUC_{24 h}/MIC in serum for bacteriostatic, bactericidal, and elimination activities were calculated as 18.91, 29.13, and 34.03 h based on the inhibitory sigmoid E_max modeling. According to the Monte Carlo simulation, the optimum doses for bacteriostatic, bactericidal, and elimination activities were 6.10, 9.41, and 10.96 mg/kg for 50% target and 7.86, 12.17, and 14.57 mg/kg for 90% target, respectively. The epidemiological cutoff value (ECV) was calculated to be 4 μg/ml which could cover 95% wild-type clinical isolates distribution. The PK-PD cutoff (CO_PD) was analyzed to be 0.25 μg/ml in vitro for tildipirosin against PM based on the Monte Carlo simulation. Compared with these two cutoff values, the finial susceptible breakpoint was defined as 4 μg/ml. The data presented now provides the optimal regimens (12.17 mg/kg) and susceptible breakpoint (4 μg/ml) for clinical use, but these predicted data should be validated in the clinical practice.

Prevalence, virulence factors and antifungal susceptibility of Candida spp. isolated from bloodstream infections in a tertiary care hospital in Brazil

Candida spp. are responsible for 80% of all systemic fungal infections and are associated with high mortality rates. This study characterised 79 bloodstream isolates of C. albicans, C. glabrata, C. orthopsilosis, C. parapsilosis and C. tropicalis from patients in a Brazilian hospital. The susceptibility to amphotericin B, caspofungin, fluconazole and voriconazole was determined; virulence factor production was assessed based on haemolysin, phospholipase and proteinase activities, and the patients' clinical characteristics were analysed. C. albicans was the predominant species (44%), followed by C. glabrata (19%), C. tropicalis (19%), C. parapsilosis (14%) and C. orthopsilosis (4%). The candidemia incidence was 1.52 per 1000 admissions, and the crude mortality rate was 52%. One C. albicans isolate was resistant to fluconazole and voriconazole. Moreover, 20.2%, 2.5% and 3.8% of the isolates exhibited dose-dependent susceptibility to fluconazole, voriconazole and caspofungin, respectively. In conclusion, although the C. glabrata incidence was higher than that usually described in Brazil, its increase was previously observed in studies conducted worldwide. Furthermore, the azole resistance of the C. albicans isolate could be due to previous exposure to these antifungals. These results highlight the importance of epidemiological studies and will facilitate an improved understanding of candidemia in the studied hospital.

Minimal inhibitory concentration distributions and epidemiological cutoff values of five antifungal agents against Sporothrix brasiliensis

BACKGROUND

Sporothrix brasiliensis is the most virulent sporotrichosis agent. This species usually responds to antifungal drugs, but therapeutic failure can occur in some patients. Antifungal susceptibility tests have been performed on this species, but no clinical breakpoints (CBPs) are available. In this situation, minimal inhibitory concentration (MIC) distributions and epidemiological cutoff values (ECVs) support the detection of identification of resistant strains.

OBJECTIVES

To study the MIC distributions of five antifungal drugs against S. brasiliensis and to propose tentative ECVs.

METHODS

MICs of amphotericin B (AMB), itraconazole (ITR), ketoconazole (KET), posaconazole (POS), and terbinafine (TRB) against 335 S. brasiliensis strains were determined by the Clinical and Laboratory Standards Institute broth microdilution method.

FINDINGS

The proposed ECV, in µg/mL, for AMB, ITR, KET, POS, and TRB were 4.0, 2.0, 1.0, 2.0, and 0.25, respectively. Percentages of wild-type strains in our population for the above antifungal drugs were 98.48, 95.22, 95.33, 100, and 97.67%, respectively.

MAIN CONCLUSIONS

These ECVs will be useful to detect strains with resistance, to define CBPs, and to elaborate specific therapeutic guidelines for S. brasiliensis. Rational use of antifungals is strongly recommended to avoid the emergence of resistant strains and ensure the therapeutic effectiveness of sporotrichosis.

The identification of Meyerozyma guilliermondii from blood cultures and surveillance samples in a university hospital in Northeast Turkey: A ten-year survey

Meyerozyma (Pichia) guilliermondii exists in human skin and mucosal surface microflora. It can cause severe fungal infections like candidemia, which is an opportunistic pathogen. One hundred and forty-one M. guilliermondii isolates, consisting of 122 blood culture isolates, belonging to 126 patients; 13 total parenteral nutrition solution isolates; and two rectal swab isolates were identified according to carbohydrate assimilation reactions in a university hospital in Turkey between January 2006 and December 2015. Following Candida albicans (34.0%) and C. parapsilosis (21.2%), the third yeast species most commonly isolated from blood cultures in the Farabi Hospital was M. guilliermondii (20.6%). The patients were hospitalised in 27 different departments. A total of 50% of the patients were in pediatric departments, 49.2% were in intensive care units, and 17.2% were in haematology-oncology departments. Molecular identification of the isolates was performed using DNA sequence analysis of ribosomal ITS gene regions and IGS amplification-AluI fingerprinting (IGSAF). With molecular identification, 140 isolates were identified as M. guilliermondii and one isolate was identified as Candida membranifaciens. It was observed that the ITS1 region specifically helps in identifying these species. It was demonstrated that biochemical and molecular methods were 99.3% consistent in identifying M. guilliermondii. The Wild-Type (WT) Minimum Inhibitory Concentrations (MICs) distribution of fluconazole, voriconazole, itraconazole, and flucytosine were determined using the Sensititre YeastOne YO2V system after 24h of incubation. One M. guilliermondii strain was determined to be non-WT for fluconazole, voriconazole, itraconazole and flucytosine. In total, three M. guilliermondii strains, for fluconazole, were determined to be non-WT in this study.

Killing Activity of Micafungin Against Candida albicans, C. dubliniensis and Candida africana in the Presence of Human Serum

We compared killing activity of micafungin in time-kill experiments in RPMI-1640 with and without 50% serum against Candida albicans, Candida dubliniensis and Candida africana reference strains and clinical isolates. Killing rates (k values) were determined for each strain and concentration. In RPMI-1640 MIC ranges were 0.015-0.03, 0.015-0.03 and 0.015 mg/L against C. albicans, C. dubliniensis and C. africana, respectively. In 50% serum MIC values for the three species increased 16- to 64-fold. In RPMI-1640 micafungin was fungicidal against two of three C. albicans isolates at 16 and 32 mg/L within 14.54 h and fungistatic against all C. africana and C. dubliniensis. Fifty per cent serum significantly decreased the growth rate of C. africana, but not of the other two species; weak in vivo replication ability of C. africana was confirmed in murine model. In 50% serum micafungin at 0.25 and 1 mg/L did not inhibit any of the three species (k values were always negative). Micafungin killing rate in 50% serum at 4, 16 and 32 mg/L was significantly decreased for C. albicans, but increased for C. dubliniensis compared to RPMI-1640. Killing activity of micafungin against C. africana was comparable or higher in 50% serum than in RPMI-1640. Although micafungin is a highly protein-bound drug, it was equally effective against the species of the C. albicans complex in 50% serum at therapeutic trough concentration (4 mg/L). Both in vitro and in vivo data confirmed the low virulence of C. africana compared to the two sibling species.

Rapid Evaporative Ionisation Mass Spectrometry (REIMS) Provides Accurate Direct from Culture Species Identification within the Genus Candida

Members of the genus Candida, such as C. albicans and C. parapsilosis, are important human pathogens. Other members of this genus, previously believed to carry minimal disease risk, are increasingly recognised as important human pathogens, particularly because of variations in susceptibilities to widely used anti-fungal agents. Thus, rapid and accurate identification of clinical Candida isolates is fundamental in ensuring timely and effective treatments are delivered. Rapid Evaporative Ionisation Mass Spectrometry (REIMS) has previously been shown to provide a high-throughput platform for the rapid and accurate identification of bacterial and fungal isolates. In comparison to commercially available matrix assisted laser desorption ionisation time of flight mass spectrometry (MALDI-ToF), REIMS based methods require no preparative steps nor time-consuming cell extractions. Here, we report on the ability of REIMS-based analysis to rapidly and accurately identify 153 clinical Candida isolates to species level. Both handheld bipolar REIMS and high-throughput REIMS platforms showed high levels of species classification accuracy, with 96% and 100% of isolates classified correctly to species level respectively. In addition, significantly different (FDR corrected P value < 0.05) lipids within the 600 to 1000 m/z mass range were identified, which could act as species-specific biomarkers in complex microbial communities.

Clinical Practice Guideline for the Management of Candidiasis: 2016 Update by the Infectious Diseases Society of America

It is important to realize that guidelines cannot always account for individual variation among patients. They are not intended to supplant physician judgment with respect to particular patients or special clinical situations. IDSA considers adherence to these guidelines to be voluntary, with the ultimate determination regarding their application to be made by the physician in the light of each patient's individual circumstances.

Invasive Candidiasis

Invasive candidiasis is a collective term that refers to a group of infectious syndromes caused by a variety of species of Candida, 5 of which cause most cases. Candidemia is the most commonly recognized syndrome associated with invasive candidiasis. Certain conditions may influence the likelihood for one species versus another in a specific clinical scenario, and this can have important implications for selection of antifungal therapy and the duration of treatment. Molecular diagnostic technology plays an ever-increasing role as an adjunct to traditional culture-based diagnostics, offering significant potential toward improvement in patient care.

Agreement of Direct Antifungal Susceptibility Testing from Positive Blood Culture Bottles with the Conventional Method for Candida Species

Early availability of antifungal susceptibilities can ensure timely institution of targeted therapy in candidemia, which can improve patient outcomes. This study prospectively determines the agreement between the results of direct testing of antifungal susceptibilities from blood culture bottles by disk diffusion and Etest and the results of standardized susceptibility testing methods; direct testing would allow susceptibility results to be available 1 to 2 days earlier. A total of 104 blood cultures with different Candida species (28% C. albicans, 27% C. parapsilosis, 26% C. tropicalis, etc.) were evaluated between January 2012 and May 2013 for agreement of fluconazole, voriconazole, and amphotericin B susceptibility results by disk diffusion. Agreement in MICs obtained by Etest was determined for fluconazole (21 isolates), voriconazole (28 isolates), amphotericin (29 isolates), and caspofungin (29 isolates). The kappa scores for categorical agreement were highest for fluconazole by disk diffusion (0.902, standard error [SE] = 0.076) and Etest (1.00, SE = 0.218) and for amphotericin B by disk diffusion (1.00, SE = 0.098). The Pearson correlation (r) of zone diameters was strongest for fluconazole (0.69) and amphotericin (0.70) and moderate for voriconazole (0.60), and the Pearson correlation of MICs was strongest for fluconazole (0.94) and caspofungin (0.88). However, the moderate correlation of amphotericin MICs with zone diameters (-0.42) precludes the use of amphotericin B disk diffusion for susceptibility testing. There were no very major errors; however, there were 1 (1%) major and 5 (4.8%) minor errors with disk diffusion and 4 (13.3%) minor errors with Etest. Thus, antifungal disk diffusion directly from blood culture bottles is a rapid and easy method for fluconazole and voriconazole susceptibility testing for timely tailoring of candidemia therapy.

Rapid identification of 6328 isolates of pathogenic yeasts using MALDI-ToF MS and a simplified, rapid extraction procedure that is compatible with the Bruker Biotyper platform and database

Rapid and accurate identification of yeast isolates from clinical samples is essential, given their innately variable antifungal susceptibility profiles, and the proposal of species-specific antifungal susceptibility interpretive breakpoints. Here we have evaluated the utility of MALDI-ToF MS analysis for the identification of clinical isolates of pathogenic yeasts. A simplified, rapid extraction method, developed in our laboratory, was applied to 6343 isolates encompassing 71 different yeast species, which were then subjected to MALDI-ToF MS analysis using a Bruker Microflex and the resulting spectra were assessed using the supplied Bruker database. In total, 6328/6343 (99.8%) of isolates were correctly identified by MALDI-ToF MS. Our simplified extraction protocol allowed the correct identification of 93.6% of isolates, without the need for laborious full extraction, and a further 394 (6.2%) of isolates could be identified after full extraction. Clinically relevant identifications with both extraction methods were achieved using the supplied Bruker database and did not require the generation of bespoke, in-house databases created using profiles obtained with the adapted extraction method. In fact, the mean LogScores obtained using our method were as robust as those obtained using the recommended, published full extraction procedures. However, an in-house database can provide a useful additional identification tool for unusual or rarely encountered organisms. Finally, the proposed methodology allowed the correct identification of over 75% of isolates directly from the initial cultures referred to our laboratory, without the requirement for additional sub-culture on standardised mycological media.

Candida lusitaniae MICs to the echinocandins are elevated but FKS-mediated resistance is rare

MIC values were generated for caspofungin, micafungin, and anidulafungin against 106 isolates of C. lusitaniae, and these values were compared to established epidemiologic cutoff values. The majority of isolates were wild type both by MIC value as well as by FKS1 hotspot sequencing. Although C. lusitaniae isolates have MIC values to the echinocandins that are elevated compared to other common species, with regard to known mechanisms of resistance to the echinocandins, isolates with MIC values at or below the epidemiological cutoff values of 0.5 and 1 μg/mL for micafungin and anidulafungin, respectively, should be considered wild type.

Candida dubliniensis and Candida albicans differentiation by colony morphotype in Sabouraud-triphenyltetrazolium agar

BACKGROUND

Candida dubliniensis is a germ tube and chlamydoconidia producing Candida species that may be misidentified as Candida albicans. Molecular-based methods are the most reliable techniques for C. albicans and C. dubliniensis differentiation. However, accurate, quick and inexpensive phenotypic tests are needed to be used in low-complexity mycology laboratories.

AIMS

To evaluate colony morphotypes on Sabouraud-triphenyltetrazolium agar as a tool for C. dubliniensis and C. albicans differentiation.

METHODS

The morphology of 126 C. albicans and C. dubliniensis strains was evaluated and compared with their identification by molecular methods.

RESULTS

The method showed 100% sensitivity and specificity when color and the presence or absence of large white mycelial halo was evaluated.

CONCLUSIONS

Colony morphotype on Sabouraud-triphenyltetrazolium agar should be considered as a new tool to differentiate C. dubliniensis and C. albicans.

Target enzyme mutations confer differential echinocandin susceptibilities in Candida kefyr

Candida kefyr is an increasingly reported pathogen in patients with hematologic malignancies. We studied a series of bloodstream isolates that exhibited reduced echinocandin susceptibilities (RES). Clinical and surveillance isolates were tested for susceptibilities to all three echinocandins, and those isolates displaying RES to one or more echinocandins were selected for molecular and biochemical studies. The isolates were analyzed for genetic similarities, and a subset was analyzed for mutations in the echinocandin target gene FKS1 and glucan synthase echinocandin sensitivities using biochemical methods. The molecular typing did not indicate strong genetic relatedness among the isolates except for a series of strains recovered from a single patient. Two unrelated isolates with RES had previously uncharacterized FKS1 mutations: R647G and deletion of amino acid 641 (F641Δ). Biochemical analysis of the semipurified R647G glucan synthase generated differential echinocandin sensitivity (resistance to micafungin only), while the deletion of F641 resulted in a glucan synthase highly insensitive to all three echinocandins. The consecutive isolates from a single patient with RES all harbored the common S645P mutation, which conferred resistance to all three echinocandins. The MIC values paralleled the glucan synthase inhibition kinetic data, although the S645P isolates displayed relatively higher susceptibility to caspofungin (2 μg/ml) than the other two echinocandins (>8 μg/ml). These findings highlight novel and common FKS1 mutations in C. kefyr isolates. The observation of differential susceptibilities to echinocandins may provide important mechanistic insights for echinocandin antifungals.

Antifungal susceptibilities of Candida isolates causing bloodstream infections at a medical center in Taiwan, 2009-2010

We used the Sensititre YeastOne (SYO) method (Trek Diagnostic Systems) to determine the MICs of nine antifungal agents against 474 nonduplicate blood Candida isolates. The MIC results were interpreted according to updated clinical breakpoints (CBPs) recommended by the Clinical and Laboratory Standards Institute (CLSI; document M27-S4) or epidemiology cutoff values (ECVs). The rates of fluconazole susceptibility were 99.2% (234/236) in Candida albicans, 86.7% (85/98) in C. tropicalis, and 97.7% (42/43) in C. parapsilosis. Among the 77 isolates of C. glabrata, 90.9% showed dose-dependent susceptibility (S-DD) to fluconazole. Nearly all isolates of C. albicans, C. parapsilosis, and C. krusei were susceptible to voriconazole; however, rates of voriconazole susceptibility were 78.6% in C. tropicalis. Few isolates of C. albicans (n = 5; 2.1%) and C. glabrata (n = 3; 3.9%), no isolates of C. parapsilosis, C. krusei, and C. guilliermondii, but 62.2% (n = 51) of C. tropicalis isolates were non-wild type for posaconazole susceptibility. For itraconazole susceptibility, 98.3% of C. albicans isolates were wild type, and 3.9% (n = 3) of C. glabrata isolates were non-wild type. Almost all of the isolates tested (>97% for all species) were susceptible to both micafungin and anidulafungin. All isolates tested were found to be wild type for amphotericin B susceptibility, with MICs of <1 μg/ml. Further evaluation is needed to establish CBPs of antifungal agents by the 24-h SYO method for the management of patients with candidemia or other invasive candida infections.

Therapies against murine Candida guilliermondii infection, relationship between in vitro antifungal pharmacodynamics and outcome

BACKGROUND

Candida guilliermondii has been recognized as an emerging pathogen showing a decreased susceptibility to fluconazole and considerably high echinocandin MICs.

AIMS

Evaluate the in vitro activity of anidulafungin in comparison to amphotericin B and fluconazole against different isolates of C. guilliermondii, and their efficacy in an immunosuppressed murine model of disseminated infection.

METHODS

The in vitro susceptibility of four strains against amphotericin B, fluconazole and anidulafungin was performed by using a reference broth microdilution method and time-kill curves. The in vivo efficacy was evaluated by determination of fungal load reduction in kidneys of infected animals receiving deoxycholate AMB at 0,8 mg/kg i.v., liposomal amphotericin B at 10 mg/kg i.v., fluconazole at 50 mg/kg, or anidulafungin at 10 mg/kg.

RESULTS

Amphotericin B and anidulafungin showed fungicidal activity, while fluconazole was fungistatic for all the strains. In the murine model, liposomal amphotericin B at 10 mg/kg/day was effective in reducing the tissue burden in kidneys of mice infected with any of the tested strains. However, amphotericin B, anidulafungin and fluconazole were only effective against those strains showing low MIC values.

CONCLUSIONS

Liposomal amphotericin B showed the higher activity and efficacy against the two strains of C. guilliermondii, in contrast to the poor effect of fluconazole and anidulafungin. Further studies with more isolates of C. guilliermondii representing a wider range of MICs should be carried out to assess whether there is any relationship between MIC values and anidulafungin efficacy.

Background changing patterns of neonatal fungal sepsis in a developing country

BACKGROUND

Candida albicans is the predominant isolate in many neonatal fungal bloodstream infections (BSIs), so fluconazole is used as empiric antifungal therapy.

AIM

To determine the predominant organisms, antifungal sensitivity patterns, clinical and demographic risk factors and crude mortality rate in neonatal fungal BSI cases.

SUBJECTS AND METHODS

This is a review of all neonatal fungal BSI cases between January 2007 and December 2011.

RESULTS

Fifty-nine patients were included in the study. Candida parapsilosis (54.2%) was isolated in majority of the cases, followed by C. albicans (27.1%). Fluconazole resistance was present in 16 of 32 cases of C. parapsilosis versus 1 of 16 cases of C. albicans (P = 0.003). Mortality rate was 45.8%. Surgical problems were present in 55.9%. Death was significantly associated with lower birth weight (P = 0.046) and necrotizing enterocolitis (P = 0.034).

CONCLUSIONS

The increase in neonatal fungal BSI and resistant organisms highlights the need to review use of routine empiric fluconazole and to implement preventive measures.

Multicenter study of anidulafungin and micafungin MIC distributions and epidemiological cutoff values for eight Candida species and the CLSI M27-A3 broth microdilution method

Since epidemiological cutoff values (ECVs) using CLSI MICs from multiple laboratories are not available for Candida spp. and the echinocandins, we established ECVs for anidulafungin and micafungin on the basis of wild-type (WT) MIC distributions (for organisms in a species-drug combination with no detectable acquired resistance mechanisms) for 8,210 Candida albicans, 3,102 C. glabrata, 3,976 C. parapsilosis, 2,042 C. tropicalis, 617 C. krusei, 258 C. lusitaniae, 234 C. guilliermondii, and 131 C. dubliniensis isolates. CLSI broth microdilution MIC data gathered from 15 different laboratories in Canada, Europe, Mexico, Peru, and the United States were aggregated to statistically define ECVs. ECVs encompassing 97.5% of the statistically modeled population for anidulafungin and micafungin were, respectively, 0.12 and 0.03 μg/ml for C. albicans, 0.12 and 0.03 μg/ml for C. glabrata, 8 and 4 μg/ml for C. parapsilosis, 0.12 and 0.06 μg/ml for C. tropicalis, 0.25 and 0.25 μg/ml for C. krusei, 1 and 0.5 μg/ml for C. lusitaniae, 8 and 2 μg/ml for C. guilliermondii, and 0.12 and 0.12 μg/ml for C. dubliniensis. Previously reported single and multicenter ECVs defined in the present study were quite similar or within 1 2-fold dilution of each other. For a collection of 230 WT isolates (no fks mutations) and 51 isolates with fks mutations, the species-specific ECVs for anidulafungin and micafungin correctly classified 47 (92.2%) and 51 (100%) of the fks mutants, respectively, as non-WT strains. These ECVs may aid in detecting non-WT isolates with reduced susceptibility to anidulafungin and micafungin due to fks mutations.

Frequency of fks mutations among Candida glabrata isolates from a 10-year global collection of bloodstream infection isolates

Among 119 echinocandin non-wild-type (non-WT) Candida glabrata strains from two global surveys, mutations in fks hot spots (HSs) were detected in 28 (from 7 countries and 8 U.S. states): 24 strains (85.7%) had non-WT MICs for micafungin, 22 (78.6%) for anidulafungin, and 25 (89.3%) for caspofungin. The most common FKS substitutions among non-WT strains were at positions F659 (n = 7) and S663 (n = 7). Three isolates displaying WT MIC results had F625Y, L630I, and D632Y substitutions or non-HS mutations. Mutations that have been reported to decrease the echinocandin binding to the 1,3-β-d-glucan synthase were categorized as resistant by applying the new CLSI breakpoint criteria for all three echinocandins.

Epidemiological cutoff values for fluconazole, itraconazole, posaconazole, and voriconazole for six Candida species as determined by the colorimetric Sensititre YeastOne method

In the absence of clinical breakpoints (CBP), epidemiological cutoff values (ECVs) are useful to separate wild-type (WT) isolates (without mechanisms of resistance) from non-WT isolates (those that can harbor some resistance mechanisms), which is the goal of susceptibility tests. Sensititre YeastOne (SYO) is a widely used method to determine susceptibility of Candida spp. to antifungal agents. The CLSI CBP have been established, but not for the SYO method. The ECVs for four azoles, obtained using MIC distributions determined by the SYO method, were calculated via five methods (three statistical methods and based on the MIC50 and modal MIC). Respectively, the median ECVs (in mg/liter) of the five methods for fluconazole, itraconazole, posaconazole, and voriconazole (in parentheses: the percentage of isolates inhibited by MICs equal to or less than the ECVs; the number of isolates tested) were as follows: 2 (94.4%; 944), 0.5 (96.7%; 942), 0.25 (97.6%; 673), and 0.06 (96.7%; 849) for Candida albicans; 4 (86.1%; 642), 0.5 (99.4%; 642), 0.12 (93.9%; 392), and 0.06 (86.9%; 559) for C. parapsilosis; 8 (94.9%; 175), 1 (93.7%; 175), 2 (93.6%; 125), and 0.25 (90.4%; 167) for C. tropicalis; 128 (98.6%; 212), 4 (95.8%; 212), 4 (96.0%; 173), and 2 (98.5; 205) for C. glabrata; 256 (100%; 53), 1 (98.1%; 53), 1 (100%; 33), and 1 (97.9%; 48) for C. krusei; 4 (89.2%; 93), 0.5 (100%; 93), 0.25 (100%; 33), and 0.06 (87.7%; 73) for C. orthopsilosis. All methods included ≥94% of isolates and yielded similar ECVs (within 1 dilution). These ECVs would be suitable for monitoring emergence of isolates with reduced susceptibility by using the SYO method.

In vitro fluconazole and voriconazole susceptibilities of Candida bloodstream isolates in Korea: use of the CLSI and EUCAST epidemiological cutoff values

Background

At present, the clinical breakpoints (CBPs) of both fluconazole and voriconazole are available only for 3 common Candida species in the Clinical and Laboratory Standards Institute (CLSI) and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) methods. Epidemiological cutoff values (ECVs) were recently applied to both methods to detect the emergence of acquired resistance (i.e., non-wild-type isolates) among 5 common Candida species.

Methods

We performed a nationwide study to determine the fluconazole and voriconazole susceptibility of Candida bloodstream isolates (BSIs) using both the CLSI and EUCAST methods. A total of 423 BSIs of 5 Candida species were collected from 8 hospitals. The azole susceptibilities were assessed on the basis of the species-specific CBPs and ECVs.

Results

Of the 341 BSIs of 3 common Candida species (i.e., C. albicans, C. tropicalis, and C. parapsilosis), 0.3% and 0.9%, 0.0% and 1.5% of isolates were categorized as fluconazole and voriconazole resistant according to the CLSI and EUCAST CBPs, respectively. Of 423 total BSIs, 1.4% and 2.6% had fluconazole minimum inhibitory concentrations (MICs) exceeding the ECVs according to the CLSI and EUCAST, respectively; 1.0% and 2.1% had voriconazole MICs exceeding the ECVs according to the CLSI and EUCAST, respectively. Categorical agreement between the methods using ECVs was 98.3% for fluconazole and 98.3% for voriconazole.

Conclusions

The EUCAST and CLSI methods using ECVs provide highly concordant results. Moreover, non-wild-type isolates with possibly acquired azole resistance were rare among the BSIs of 5 common Candida species in Korea.

Nanoscale analysis of caspofungin-induced cell surface remodelling in Candida albicans

The advent of fungal pathogens that are resistant to the classic repertoire of antifungal drugs has increased the need for new therapeutic agents. A prominent example of such a novel compound is caspofungin, known to alter cell wall biogenesis by inhibiting β-1,3-D-glucan synthesis. Although much progress has been made in understanding the mechanism of action of caspofungin, little is known about its influence on the biophysical properties of the fungal cells. Here, we use atomic force microscopy (AFM) to demonstrate that caspofungin induces major remodelling of the cell surface properties of Candida albicans. Caspofungin causes major morphological and structural alterations of the cells, which correlate with a decrease of the cell wall mechanical strength. Moreover, we find that the drug induces the massive exposure of the cell adhesion protein Als1 on the cell surface and leads to increased cell surface hydrophobicity, two features that trigger cell aggregation. This behaviour is not observed in yeast species lacking Als1, demonstrating the key role that the protein plays in determining the aggregation phenotype of C. albicans. The results show that AFM opens up new avenues for understanding the molecular bases of microbe-drug interactions and for developing new therapeutic agents.

Invasive candidiasis in Pakistan: clinical characteristics, species distribution and antifungal susceptibility

This study reports for the first time, to our knowledge, descriptive epidemiological data for 188 invasive Candida isolates from Pakistan, including species identification and antifungal susceptibility against fluconazole, itraconazole, voriconazole, caspofungin, micafungin, anidulafungin and amphotericin. Risk factors for invasive candidiasis (IC) were determined for 96 patients from Karachi, Pakistan. In adults and neonates, Candida tropicalis (38 and 36 %, respectively) was the most common species, followed in adults by Candida parapsilosis (17.8 %), Candida glabrata (15.9 %) and Candida albicans (12.3 %). C. albicans (21 %) was the second most common in neonates. In children, C. albicans (31.9 %), C. tropicalis (26.4 %) and C. parapsilosis (19.4 %) were the most common. C. albicans IC was significantly associated with paediatric age [crude odds ratio (COR) 3.46, 95 % confidence interval (CI) 1.63-7.32]. Rare species made up 17.5 % of the total isolates studied. Resistance to fluconazole was seen in C. glabrata (15 .0%) and Candida krusei (100 .0%). Only one isolate (C. glabrata) was resistant to all three echinocandins. Low MICs of fluconazole for 98 % (184/188) of isolates tested support its continued use as an empiric therapy for IC. Non-C. albicans IC was associated with the use of β-lactam inhibitor combinations (COR 3.16, 95 % CI 1.05-9.57). Use of healthcare devices was documented in 85.4 % of IC patients, whilst 75 .0% had been admitted to special care units. Surprisingly, 66.7 % of patients with IC were not obviously immunosuppressed. The high frequency of modifiable risk factors in this population indicates that candidaemia can be reduced with stringent antibiotic and infection control measures. These data will be useful for empiric selection of antifungals in Karachi, and contribute to global assessments of antifungal resistance.

Candida guilliermondii and other species of candida misidentified as Candida famata: assessment by vitek 2, DNA sequencing analysis, and matrix-assisted laser desorption ionization-time of flight mass spectrometry in two global antifungal surveillance programs

Candida famata (teleomorph Debaryomyces hansenii) has been described as a medically relevant yeast, and this species has been included in many commercial identification systems that are currently used in clinical laboratories. Among 53 strains collected during the SENTRY and ARTEMIS surveillance programs and previously identified as C. famata (includes all submitted strains with this identification) by a variety of commercial methods (Vitek, MicroScan, API, and AuxaColor), DNA sequencing methods demonstrated that 19 strains were C. guilliermondii, 14 were C. parapsilosis, 5 were C. lusitaniae, 4 were C. albicans, and 3 were C. tropicalis, and five isolates belonged to other Candida species (two C. fermentati and one each C. intermedia, C. pelliculosa, and Pichia fabianni). Additionally, three misidentified C. famata strains were correctly identified as Kodomaea ohmeri, Debaryomyces nepalensis, and Debaryomyces fabryi using intergenic transcribed spacer (ITS) and/or intergenic spacer (IGS) sequencing. The Vitek 2 system identified three isolates with high confidence to be C. famata and another 15 with low confidence between C. famata and C. guilliermondii or C. parapsilosis, displaying only 56.6% agreement with DNA sequencing results. Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) results displayed 81.1% agreement with DNA sequencing. One strain each of C. metapsilosis, C. fermentati, and C. intermedia demonstrated a low score for identification (<2.0) in the MALDI Biotyper. K. ohmeri, D. nepalensis, and D. fabryi identified by DNA sequencing in this study were not in the current database for the MALDI Biotyper. These results suggest that the occurrence of C. famata in fungal infections is much lower than previously appreciated and that commercial systems do not produce accurate identifications except for the newly introduced MALDI-TOF instruments.

Elevated chitin content reduces the susceptibility of Candida species to caspofungin

The echinocandin antifungal drugs inhibit synthesis of the major fungal cell wall polysaccharide β(1,3)-glucan. Echinocandins have good efficacy against Candida albicans but reduced activity against other Candida species, in particular Candida parapsilosis and Candida guilliermondii. Treatment of Candida albicans with a sub-MIC level of caspofungin has been reported to cause a compensatory increase in chitin content and to select for sporadic echinocandin-resistant FKS1 point mutants that also have elevated cell wall chitin. Here we show that elevated chitin in response to caspofungin is a common response in various Candida species. Activation of chitin synthesis was observed in isolates of C. albicans, Candida tropicalis, C. parapsilosis, and C. guilliermondii and in some isolates of Candida krusei in response to caspofungin treatment. However, Candida glabrata isolates demonstrated no exposure-induced change in chitin content. Furthermore, isolates of C. albicans, C. krusei, C. parapsilosis, and C. guilliermondii which were stimulated to have higher chitin levels via activation of the calcineurin and protein kinase C (PKC) signaling pathways had reduced susceptibility to caspofungin. Isolates containing point mutations in the FKS1 gene generally had higher chitin levels and did not demonstrate a further compensatory increase in chitin content in response to caspofungin treatment. These results highlight the potential of increased chitin synthesis as a potential mechanism of tolerance to caspofungin for the major pathogenic Candida species.

Pseudomembranous candidiasis in HIV/AIDS patients in Cali, Colombia

Candida albicans is the most frequently isolated yeast from the oral cavity of HIV/AIDS individuals. The use of fluconazole has increased the number of resistant or less-sensitive Candida species different than C. albicans. The purpose of this study was to identify the Candida species producing pseudomembranous candidiasis in patients suffering from AIDS, their relationship with CD4(+) counts and their sensitivity to fluconazole and itraconazole. We studied 71 patients at a hospital in the city of Cali. Samples of white plaque were seeded on CHROMagar Candida, yeast identification was done with API 20C Aux, and susceptibility testing was determined by E test. Ninety-three yeast isolates were obtained, 52 single and 41 mixed. C. albicans was the most isolated, followed by C. glabrata. An increased frequency of isolates and variety of Candida species occurred in patients with a CD4(+) cell count ≤100 cells/mm(3) without significant differences (p = 0.29). The susceptibility study showed that 8 (8.6%) isolates were resistant to fluconazole and 11 (11.8%) to itraconazole, while 6 (8.8%) C. albicans were simultaneously resistant. No association was found between the isolates of C. albicans or Candida species different than C. albicans and the use of fluconazole (p = 0.21). The results of this study indicate that in the tested population, fluconazole continues to be the best treatment option for oropharyngeal candidiasis in patients suffering from AIDS (HIV/AIDS); however, susceptibility tests are necessary in patients who present therapeutic failure.

Comparison of three statistical methods for establishing tentative wild-type population and epidemiological cutoff values for echinocandins, amphotericin B, flucytosine, and six Candida species as determined by the colorimetric Sensititre YeastOne method

The Sensititre YeastOne (SYO) method is a widely used method to determine the susceptibility of Candida spp. to antifungal agents. CLSI clinical breakpoints (CBP) have been reported for antifungals, but not using this method. In the absence of CBP, epidemiological cutoff values (ECVs) are useful to separate wild-type (WT) isolates (those without mechanisms of resistance) from non-WT isolates (those that can harbor some resistance mechanisms), which is the goal of any susceptibility test. The ECVs for five agents, obtained using the MIC distributions determined by the SYO test, were calculated and contrasted with those for three statistical methods and the MIC(50) and modal MIC, both plus 2-fold dilutions. The median ECVs (in mg/liter) (% of isolates inhibited by MICs equal to or less than the ECV; number of isolates tested) of the five methods for anidulafungin, micafungin, caspofungin, amphotericin B, and flucytosine, respectively, were as follows: 0.25 (98.5%; 656), 0.06 (95.1%; 659), 0.25 (98.7%; 747), 2 (100%; 923), and 1 (98.5%; 915) for Candida albicans; 8 (100%; 352), 4 (99.2%; 392), 2 (99.2%; 480), 1 (99.8%; 603), and 0.5 (97.9%; 635) for C. parapsilosis; 1 (99.2%; 123), 0.12 (99.2%; 121), 0.25 (99.2%; 138), 2 (100%; 171), and 0.5 (97.2%; 175) for C. tropicalis; 0.12 (96.6%; 174), 0.06 (96%; 176), 0.25 (98.4%; 188), 2 (100%; 209), and 0.25 (97.6%; 208) for C. glabrata; 0.25 (97%; 33), 0.5 (93.9%; 33), 1 (91.9%; 37), 4 (100%; 51), and 32 (100%; 53) for C. krusei; and 4 (100%; 33), 2 (100%; 33), 2 (100%; 54), 1 (100%; 90), and 0.25 (93.4%; 91) for C. orthopsilosis. The three statistical methods gave similar ECVs (within one dilution) and included ≥ 95% of isolates. These tentative ECVs would be useful for monitoring the emergence of isolates with reduced susceptibility by use of the SYO method.

Candida mesorugosa sp. nov., a novel yeast species similar to Candida rugosa, isolated from a tertiary hospital in Brazil

Candida rugosa is a yeast species that is emerging as a causative agent of invasive infection, particularly in Latin America. Recently, C. pseudorugosa was proposed as a new species closely related to C. rugosa. We evaluated in this investigation the genetic heterogeneity within the C. rugosa species complex. All clinical isolates used in this study were identified phenotypically as C. rugosa but were genotypically different from the C. rugosa type, ATCC 10571. RAPD marker analysis revealed less than 83% similarity between our clinical isolates and the C. rugosa type strain. The D1/D2 region sequences of our clinical isolates showed 98% identity with C. rugosa but only 94-95% identity with C. pseudorugosa. The ITS rDNA sequences of the Brazilian isolates showed 91% identity with the C. rugosa ATCC 10571 ITS sequence. Network and Bayesian analyses of ITS and housekeeping gene sequences separated our clinical isolates into different branches from C. rugosa type strain. These differences are sufficient to reassign our isolates to a distinct species, named C. mesorugosa.

Progress in antifungal susceptibility testing of Candida spp. by use of Clinical and Laboratory Standards Institute broth microdilution methods, 2010 to 2012

Antifungal susceptibility testing of Candida has been standardized and refined and now may play a useful role in managing Candida infections. Important new developments include validation of 24-h reading times for all antifungal agents and the establishment of species-specific epidemiological cutoff values (ECVs) for the systemically active antifungal agents and both common and uncommon species of Candida. The clinical breakpoints (CBPs) for fluconazole, voriconazole, and the echinocandins have been revised to provide species-specific interpretive criteria for the six most common species. The revised CBPs not only are predictive of clinical outcome but also provide a more sensitive means of identifying those strains with acquired or mutational resistance mechanisms. This brief review serves as an update on the new developments in the antifungal susceptibility testing of Candida spp. using Clinical and Laboratory Standards Institute (CLSI) broth microdilution (BMD) methods.

Aspergillus section Versicolores: nine new species and multilocus DNA sequence based phylogeny

β-tubulin, calmodulin, internal transcribed spacer and partial lsu-rDNA, RNA polymerase 2, DNA replication licensing factor Mcm7, and pre-rRNA processing protein Tsr1 were amplified and sequenced from numerous isolates belonging to Aspergillus sect. versicolor. The isolates were analyzed phylogenetically using the concordance model to establish species boundaries. Aspergillus austroafricanus, A. creber, A. cvjetkovicii, A. fructus, A. jensenii, A. puulaauensis, A. subversicolor, A. tennesseensis and A. venenatus are described as new species and A. amoenus, A. protuberus,A. sydowii, A. tabacinus and A. versicolor are accepted as distinct species on the basis of molecular and phenotypic differences. PCR primer pairs used to detect A. versicolor in sick building syndrome studies have a positive reaction for all of the newly described species except A. subversicolor.