Fungal urinary tract infection in burn patients with long-term foley catheterization

Amino Acid Sensing and Assimilation by the Fungal Pathogen Candida albicans in the Human Host

Nutrient uptake is essential for cellular life and the capacity to perceive extracellular nutrients is critical for coordinating their uptake and metabolism. Commensal fungal pathogens, e.g., Candida albicans, have evolved in close association with human hosts and are well-adapted to using diverse nutrients found in discrete host niches. Human cells that cannot synthesize all amino acids require the uptake of the “essential amino acids” to remain viable. Consistently, high levels of amino acids circulate in the blood. Host proteins are rich sources of amino acids but their use depends on proteases to cleave them into smaller peptides and free amino acids. C. albicans responds to extracellular amino acids by pleiotropically enhancing their uptake and derive energy from their catabolism to power opportunistic virulent growth. Studies using Saccharomyces cerevisiae have established paradigms to understand metabolic processes in C. albicans; however, fundamental differences exist. The advent of CRISPR/Cas9-based methods facilitate genetic analysis in C. albicans, and state-of-the-art molecular biological techniques are being applied to directly examine growth requirements in vivo and in situ in infected hosts. The combination of divergent approaches can illuminate the biological roles of individual cellular components. Here we discuss recent findings regarding nutrient sensing with a focus on amino acid uptake and metabolism, processes that underlie the virulence of C. albicans.

Nosocomial Candiduria in the Elderly: Microbiological Diagnosis

Candiduria is associated with high morbidity, mortality, and long hospitalization, involving high costs for the healthcare system. The use of increasingly aggressive treatments has prolonged the lives of patients susceptible to candiduria, namely the immunosuppressed, the premature, and the elderly. Our objective was to evaluate the incidence of nosocomial candiduria and the implicated species in hospitalized patients aged over 80 years old from three Spanish centers during 2012 and 2013. Urine samples received from these patients were cultured and analyzed by flow cytometry in search of leukocyturia, hematuria, proteinuria, and microbial nitrate reductase activity. The isolated yeast species were identified microscopically, by germ tube formation in serum, colony morphology after subculture onto CHROMagar Candida (Becton-Dickinson, UK), assimilation of carbon compounds ID32C (bioMérieux, France), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDITOF) (Bruker Daltonics, Germany) and, in case of inconsistency, by sequencing of the ITS regions of ribosomal DNA (ITS1-5, 8S-ITS2). Susceptibility tests were also performed. The incidence of candiduria in the elderly population was 10.3%. A total of 155 strains of yeasts were isolated. The predominant species was Candida albicans, followed by Candida glabrata and then Candida tropicalis. Several infrequent species were found; among them, the first isolate of candiduria-producing Candida pulcherrima described in the literature. Our finding should raise concerns about the elderly population, which is probably the most important risk group for candiduria in the present moment, and the emergence of unusual yeast species producing candiduria, which are resistant against the commonly used antifungal agents.

Specific Human and Candida Cellular Interactions Lead to Controlled or Persistent Infection Outcomes during Granuloma-Like Formation

A delayed type of multicellular process could be crucial during chronic candidiasis in determining the course of infection. This reaction, consisting of organized immune cells surrounding the pathogen, initiates an inflammatory response to avoid fungal dissemination. The goal of the present study was to examine, at an in vitro cellular scale, Candida and human immune cell interaction dynamics during a long-term period. By challenging human peripheral blood immune cells from 10 healthy donors with 32 Candida albicans and non-albicans (C. glabrata, C. tropicalis, C. parapsilosis, C. dubliniensis, C. lusitaniae, C. krusei, and C. kefyr) clinical isolates, we showed that Candida spp. induced the formation of granuloma-like structures within 6 days after challenge, but their sizes and the respective fungal burdens differed according to the Candida species. These two parameters are positively correlated. Phenotypic characteristics, such as hypha formation and higher axenic growth rate, seem to contribute to yeast persistence within granuloma-like structures. We showed an interindividual variability of the human response against Candida spp. Higher proportions of neutrophils and elevated CD4⁺/CD8⁺ T cell ratios during the first days after challenge were correlated with early production of gamma interferon (IFN-γ) and associated with controlled infection. In contrast, the persistence of Candida could result from upregulation of proinflammatory cytokines such as interleukin-6 (IL-6), IFN-γ, and tumor necrosis factor alpha (TNF-α) and a poor anti-inflammatory negative feedback (IL-10). Importantly, regulatory subsets of NK cells and CD4^lo CD8^hi doubly positive (DP) lymphocytes at late stage infiltrate granuloma-like structures and could correlate with the IL-10 and TNF-α production. These data offer a base frame to explain cellular events that guide infection control or fungal persistence.

Epidemiology of nosocomial fungal infections in the National Center for Burns in Casablanca, Morocco

Fungal infection is a leading cause of death in burns patients and incurs significant costs for burn units. Our aim was to determine epidemiology of these infections, and analyze risk factors in the burns intensive care unit of the National Center for Burns and Plastic Surgery at Ibn-Rochd University Hospital, Casablanca. It is a retrospective review of all patients admitted from 2011-2014 who developed cultures positive for fungal organisms. Criteria for nosocomial fungal infections were those of the Center for Disease Control in Atlanta (1988, revised 1992, 2004). Microbiological surveillance was carried out daily. Patient demographic data, % TBSA, type of infection, site(s), species and number of cultures, and risk factors for fungal infections were collected. Mean age of patients was 24.5 +/- 27.3 years; 63% were female. Mean % TBSA was 30.7 +/- 23.4%, and % FTSA was 21.7 +/- 20.1%. Injury due to flame was most common (82%), followed by scald (10%), contact (4%), electrical (3%) and chemical (1%). Incidence of nosocomial fungal infection was 10%. The fungal pathogen most frequently isolated was Candida albicans (65.7%), followed by other Candida species (18.6%). Aspergillus spp was present in 3.9% and was statistically associated with mortality (3.2%) and morbidity. In our study, risk factors for these infections were mostly degree of burn (mean TBSA = 30.7%) and prolonged broad-spectrum antibiotic therapy. These two factors were associated with a higher incidence of multiple positive cultures, and significantly increased mortality (21.6%). Amphotericin B and fluconazole were the most frequently used antifungal agents. Fungi are emerging as important nosocomial pathogens. The main clinical implications are thinking faster about fungi infections and being more careful with antibiotic prescriptions.

New procedure for rapid identification of microorganisms causing urinary tract infection from urine samples by mass spectrometry (MALDI-TOF)

INTRODUCTION

Matrix assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry is widely established as a technique in clinical microbiology laboratories for the identification of microorganisms. Using this technique, it is also possible to obtain the identification of microorganisms from untreated urine samples.

METHODS

In this study, a differential centrifugation protocol and a criterion for validation of the results in order to achieve microbial identification from untreated urine samples are proposed. Additionally, the sensitivity of the analytical procedure in monobacterial urine samples has been evaluated.

RESULTS

A 90% sensitivity (confidence interval of 81.96%-94.84%) was obtained in urine samples with bacterial counts of ≥1×10(5)CFU/ml, and it was possible to improve the percentages of direct identifications from urine samples with bacterial counts of <1×10(5)CFU/ml.

CONCLUSION

It is concluded that the MALDI-TOF system is both fast and reliable in the identification of individual microorganisms from untreated urine samples with counts of ≥1×10(5)CFU/ml.