Epidemiology and antifungal susceptibility of Candida species isolated from hospitalized patients

ObjectiveVoricanozole and caspofungin are new antifungal agents used in the treatment of Candida infections. However, the susceptibility of Candida species to these antifungal agents could be variable. The aim of this study was to investigate the distribution of the Candida species isolated from hospitalized patients and to determine their susceptibilities to some antifungal agents including voriconazole, caspofungin, fluconazole and amphotericin B.Material and MethodsA total of 164 Candida strains were isolated from clinical specimens obtained during the study period. Of 164 strains, 103 (62%) were C. albicans, followed by C. tropicalis (11%) and C. glabrata (8%). Other Candida species less frequently identified were C. parapsilosis, C. lusitaniae, C. kefyr, C. pelliculosa and C. norvegensis. Antifungal susceptibility testing of these isolates were performed according to the CLSI (formerly NCCLS) M27-A2 broth microdilution method and the results were read after 24 h.ResultsFluconazole resistance was seen in 21 (13%) isolates. All fluconazole-resistant isolates showed low MICs to caspofungin and amphotericin B. MIC values of voriconazole for Candida isolates were between 0.125 and 4 μg/ml.ConclusionAmphotericin B is still the major therapeutic agent for azole resistant Candida strains and caspofungin seems to be a good alternative.     

Molecular identification and antifungal susceptibility testing of Candida species isolated from dental plaques

Objective

The aim of the present study was to provide insight into the prevalence and susceptibility profiles of Candida species isolated from the dental plaque of Iranian immunocompetent patients. As a biofilm, Candida species are responsible for several disorders common to the oral cavity including gingivitis, dental caries, periodontitis, and the less common severe systemic infections specifically in immunosuppressed individuals.

Geographic distribution and antifungal susceptibility of the newly described species Candida orthopsilosis and Candida metapsilosis in comparison to the closely related species Candida parapsilosis

Candida orthopsilosis and Candida metapsilosis are recently described species, having previously been grouped with the more prevalent species Candida parapsilosis. Current literature contains very little data pertaining to the distributions and antifungal susceptibilities of these Candida species. We determined the species and antifungal susceptibilities of 1,929 invasive clinical isolates from the ARTEMIS antifungal surveillance program collected between 2001 and 2006 and identified as C. parapsilosis using Vitek and conventional methods. Of the 1,929 isolates of presumed C. parapsilosis tested, 117 (6.1%) were identified as C. orthopsilosis and 34 (1.8%) as C. metapsilosis. The percentage of presumed C. parapsilosis isolates found to be C. orthopsilosis varied greatly by region, with the highest percentage (10.9%) from South America and the lowest (0.7%) from Africa. The MIC distributions of the C. orthopsilosis and C. metapsilosis isolates were statistically significantly lower than those of C. parapsilosis for all drugs except fluconazole, for which they were significantly higher (P < 0.001 for all). No C. orthopsilosis or C. metapsilosis isolates were fluconazole resistant, and all were susceptible to caspofungin, anidulafungin, and micafungin.     

Modified colorimetric assay for susceptibility testing of azole antifungal drugs against Candida species

We modified a rapid susceptibility assay (RSA) for antifungal susceptibility testing of azoles based upon glucose utilization. This modified RSA method provides quantitative endpoint readings in 6 h. In this study, the modified RSA and the National Committee for Clinical Laboratory Standards M27-A methods were used to determine the MICs of fluconazole and itraconazole for 118 Candida isolates. Yeast nitrogen base containing 0.12 g of glucose per liter was used for the modified RSA method. For fluconazole, agreement among assays within one or two twofold dilutions was 72.9 and 88.1%, respectively; for itraconazole, agreement within one or two twofold dilutions was 82.2 and 89.8%, respectively. These data suggest that the modified RSA method is a reliable and rapid method for azole antifungal susceptibility testing against Candida species.     

Molecular identification and antifungal susceptibility testing of clinical isolates of the Candida rugosa species complex and proposal of the new species Candida neorugosa

Candida rugosa is a poorly known fungal species occasionally involved in human infections. A molecular analysis of the sequences of the D1/D2 domains and the internal transcribed spacer (ITS) region of the ribosomal genes of 24 clinical isolates phenotypically identified as C. rugosa demonstrated that only 10 (41.6%) isolates belonged to that species. The other isolates were identified as Candida pararugosa (41.6%) and Candida pseudorugosa (8.3%). The remaining two isolates, from human and equine infections, respectively, were clearly different from the others and represent a new species proposed here as Candida neorugosa. The closest species by D1/D2 sequences was the type strain of C. rugosa, with only 92.3% similarity. C. neorugosa can also be differentiated from all other species of the C. rugosa complex by phenotypic features. The eight antifungal drugs tested showed high in vitro activity against the 24 isolates included in the study.     

Pathogenicity and antifungal susceptibility ofChaetomium species

Several reports have been published implicatingChaetomium spp. as opportunistic pathogens. A critical review of these cases was made, and the majority of the responsible strains were studied.Chaetomium globosum was the most common species, being isolated in at least nine clinical cases of infection. Some of these clinical isolates and others from environmental sources were tested against six antifungal agents (5-fluorocytosine, fluconazole, amphotericin B, itraconazole, ketoconazole and miconazole). The 23 strains tested were totally resistant to the first two drugs, and none of the other antifungal agents demonstrated fungicidal activity. There were no significant differences between the susceptibility of the clinical strains and the other strains.     

Molecular characterization and antifungal susceptibility of the Candida parapsilosis species complex of clinical isolates from Monterrey, Mexico

Recently, it was proposed that the opportunistic yeast pathogen Candida parapsilosis was a complex composed of the following three species: Candida parapsilosis sensu stricto, Candida orthopsilosis, and Candida metapsilosis. A set of 344 clinical isolates of Candida parapsilosis from Monterrey, Mexico was re-identified by RFLP. Their antifungal susceptibility to fluconazole, caspofungin, anidulafungin and micafungin was determined using the Clinical and Laboratory Standards Institute M27-A3 protocol. Candida parapsilosis sensu stricto was the most frequent species, and was the only one which showed resistance to antifungals.     

Investigation of the possible association between nosocomial candiduria and candidaemia

This study aimed to determine whether candiduria is associated with the occurrence of nosocomial candidaemia. In the case-control part of the study, 115 cases (nosocomial candidaemia) and 115 controls (nosocomial bacteraemia) were similar in age, severity of condition and time of hospitalisation. There was a significant association of candidaemia with candiduria (OR 9.79; 95% CI 2.14-44.76). In the microbiology part of the study, 23 pairs of Candida-positive urine and blood cultures were obtained from 23 patients. In ten (43%) cases, the urine and blood culture isolates belonged to different species, and molecular typing showed a difference in two of the 13 cases yielding the same species from both specimens. Overall, there was a significant association between candiduria and candidaemia, but the Candida isolates from urine and blood were different for 52% of the patients. Thus, the data indicated that the urinary tract was probably not a source for the candidaemia.     

Candidaemia with uncommon Candida species: predisposing factors, outcome, antifungal susceptibility, and implications for management

The risk factors for and clinical features of bloodstream infection with uncommon Candida spp. (species other than C. albicans, C. glabrata, C. parapsilosis, C. tropicals and C. krusei) are incompletely defined. To identify clinical variables associated with these species that might guide management, 57 cases of candidaemia resulting from uncommon Candida spp. were analysed in comparison with 517 episodes of Candida albicans candidaemia (2001–2004). Infection with uncommon Candida spp. (5.3% of candidaemia cases), as compared with C. albicans candidaemia, was significantly more likely to be outpatient-acquired than inpatient-acquired (15 of 57 vs. 65 of 517 episodes, p 0.01). Prior exposure to fluconazole was uncommon (n = 1). Candida dubliniensis was the commonest species (n = 22, 39%), followed by Candida guilliermondii (n = 11, 19%) and Candida lusitaniae (n = 7, 12%). C. dubliniensis candidaemia was independently associated with recent intravenous drug use (p 0.01) and chronic liver disease (p 0.03), and infection with species other than C. dubliniensis was independently associated with age <65 years (p 0.02), male sex (p 0.03) and human immunodeficiency virus infection (p 0.05). Presence of sepsis at diagnosis and crude 30-day mortality rates were similar for C. dubliniensis-related, non-C. dubliniensis-related and C. albicans-related candidaemia. Haematological malignancy was the commonest predisposing factor in C. guilliermondii (n = 3, 27%) and C. lusitaniae (n = 3, 43%) candidaemia. The 30-day mortality rate of C. lusitaniae candidaemia was higher than the overall death rate for all uncommon Candida spp. (42.9% vs. 25%, p not significant). All isolates were susceptible to amphotericin B, voriconazole, posaconazole, and caspofungin; five strains (9%) had fluconazole MIC values of 16–32 mg/L. Candidaemia due to uncommon Candida spp. is emerging among hospital outpatients; certain clinical variables may assist in recognition of this entity.     

Vancomycin susceptibility of oxacillin-resistant Staphylococcus aureus isolates causing nosocomial bloodstream infections

Nosocomial oxacillin-resistant Staphylococcus aureus (ORSA) bloodstream isolates were tested to determine the prevalence of vancomycin heteroresistance. We screened 619 ORSA nosocomial bloodstream isolates from 36 hospitals between 1997 and 2000. Only one isolate exhibiting heterotypic resistance was detected. Thus, vancomycin heteroresistance in clinical bloodstream isolates remains rare in the United States.     

Honey has an antifungal effect against Candida species.

The incidence of Candida infections is escalating worldwide. The serious nature of these infections is compounded by increasing levels of drug resistance. We report that certain honeys have significant antifungal activity against clinical isolates of Candida species. Importantly, the minimum inhibitory concentration of these honeys would be achievable in a clinical setting.     

A review of Candida species causing blood stream infection

The incidence of candidemia has been on a rise worldwide. The epidemiology of invasive fungal infections in general and of candidemia in particular has changed in the past three decades because of a variety of factors like the AIDS epidemic, increased number of patients receiving immunosuppressive therapy for transplantation and the increasing use of antimicrobials in the hospital setups and even in the community. The important risk factors for candidemia include use of broad-spectrum antimicrobials, cancer chemotherapy, mucosal colonization by Candida species, indwelling vascular catheters like central venous catheters, etc. More than 90% of the invasive infections due to Candida species are attributed to five species-Candida albicans, Candida glabrata, Candida parapsilosis, Candida tropicalis and Candida krusei. However, the list of new species of Candida isolated from clinical specimens continues to grow every year. Early diagnosis and proper treatment is the key for management of candidemia cases.     

Colorimetric assay for antifungal susceptibility testing of Aspergillus species

A colorimetric assay for antifungal susceptibility testing of Aspergillus species (Aspergillus fumigatus, Aspergillus flavus, Aspergillus terreus, Aspergillus nidulans, and Aspergillus ustus) is described based on the reduction of the tetrazolium salt 2,3-bis(2-methoxy-4-nitro-5-[(sulphenylamino)carbonyl]-2H-tetrazolium-hydroxide (XTT) in the presence of menadione as an electron-coupling agent. The combination of 200 microg of XTT/ml with 25 microM menadione resulted in a high production of formazan within 2 h of exposure, allowing the detection of hyphae formed by low inocula of 10(2) CFU/ml after 24 h of incubation. Under these settings, the formazan production correlated linearly with the fungal biomass and less-variable concentration effect curves for amphotericin B and itraconazole were obtained.     

Epidemiology and antifungal susceptibility of Candida species isolated from blood: results of a 2-year multicentre study in Spain

This study, included in the prospective survey of candidaemia in Europe supported by the European Confederation of Medical Mycology, presents the epidemiological and antifungal susceptibility results of 290 cases of candidaemia (80 in children <15 years old) reported from September 1997 to August 1999 by 19 Spanish hospitals. Presence of an intravenous catheter and previous antibiotic therapy were the most frequent risk factors. The percentages of the four most common species isolated (adults/children) were as follows: Candida albicans (46/36.2), C. parapsilosis (21.9/50), C. tropicalis (12.8/3.75), and C. glabrata (10.1/5). As initial therapy, fluconazole was preferred in adults (54%) and liposomal amphotericin B in children (58%). The 30-day mortality rate was 40.6%, and the species most frequently associated with a fatal outcome was C. krusei (60%). The rates of susceptibility to antifungal agents were as follows: amphotericin B, 91%; flucytosine, 99%; fluconazole, 93.6%; itraconazole, 87.4%; and voriconazole, 92%. These results provide baseline data for future epidemiological and susceptibility studies and for evaluating the impact of new antifungal agents on the distribution of species and the mortality rates associated with candidaemia in Spain.     

Epidemiologic analysis and antifungal susceptibility of Candida blood isolates in southern Taiwan.

Candidemia is a clinically important disease which has increased in incidence worldwide in recent decades. In order to identify the risk factors for mortality in candidemic patients and to elucidate the role of antifungal susceptibility testing, a retrospective cohort study was performed of 56 episodes of candidemia in 1998 at a medical center in southern Taiwan. The minimal inhibitory concentration (MIC) of these isolates was determined by E-test. Malignancy and alimentary diseases (42.9%) were the most common underlying conditions of these patients. There was no difference of Candida spp. distribution among patients treated in medical or surgical departments, except that all 5 isolates of C. intermedia were found in patients treated in medical departments (p=0.02) and 50% of candidemic infants had C. parapsilosis isolates (p=0.046). Among all Candida isolates, 3 (5.4%) were fluconazole non-susceptible. C. tropicalis had a significantly higher rate of amphotericin B resistance than the other species (p=0.007). Thirty four patients died and 70.6% of these deaths were attributable to candidemia. Thrombocytopenia, septic shock at the date of candidemia onset, C-reactive protein > 100 mg/L, blood urea nitrogen > 20 mg/dL, length of stay < 60 days, and Acute Physiology and Chronic Health Evaluation II score > or = 10 points were significantly associated with the death attributable to candidemia. Thrombocytopenia was the only independent predictor for mortality in the multivariate analysis. When the breakpoint of fluconazole was set at 2 microg/mL, as opposed to 8 microg/mL as in the National Committee for Clinical Laboratory Standards (NCCLS) criteria, the clinical outcome of death was significantly correlated to the MICs of the blood isolates. The correlation between MIC of fluconazole determined by E-test data, which is more easily obtainable than with NCCLS methods, and outcome requires larger scale investigation.     

In vitro susceptibility of Candida species to lactoferrin.

Lactoferrin is an antimicrobial protein present in human mucosal secretions as well as saliva. As there is no information on the relative fungicidal activity of human and bovine lactoferrin, an oral isolate of Candida albicans was studied for its susceptibility to these two proteins. Exposure to a concentration of 20 micrograms ml-1 of either HLF or BLF at 37 degrees C inactivated the yeast to the same degree irrespective of the incubation time of 45, 90 or 150 min. A similar study, using 20 micrograms ml-1 BLF and an incubation time of 150 min, elicited varying anticandidal activity against 35 isolates belonging to six different Candida species. Thus, BLF was fungicidal for the six Candida species in the following decreasing order, C. tropicalis > C. krusei > C. albicans > C. guilliermondii > C. parapsilosis > C. glabrata; the latter being the most resistant. These Candida species also demonstrated significant intra-species variation in susceptibility to the protein (P < 0.05). When the yeast cells exposed to BLF were examined by cryo-scanning electron microscopy, profound cell wall changes such as cell surface blebs, swelling and cell collapse were noted. These findings suggest that lactoferrin, a constituent of saliva, may differentially modulate the carriage of Candida species in the oral cavity.