An experimental model for study of Candida survival and transmission in human volunteers

Intra-clade Heterogeneity in Candida auris: Risk of Management

Candida auris has emerged as a significant nosocomial fungal pathogen with a high risk of pathogenicity. Since the initial detection of C. auris in 2009, it gained lots of attention with a recent alert by the Centers for Disease Control and Prevention (CDC) due to its high infectivity and drug resistance. Several studies showed the capability of C. auris to secrete lytic enzymes, germinate, and form a biofilm that eventually results in interactions with the host cells, leading to serious infections. Other studies demonstrated a decrease in susceptibility of C. auris strains to available antifungals, which may be caused by mutations within the target genes, or the drug efflux pumps. However, the contribution of C. auris heterogeneity in pathogenicity and drug resistance is not well studied. Here, we shed light on the factors contributing to the development of heterogeneity in C. auris. These include phenotypic changes, biofilm formation, mechanisms of drug resistance, host invasion, mode of transmission, and expression of virulence factors. C. auris exhibits different phenotypes, particularly aggregative, and non-aggregative forms that play an important role in fungal heterogeneity, which significantly affects drug resistance and pathogenicity. Collectively, heterogeneity in C. auris significantly contributes to ineffective treatment, which in turn affects the fungal pathogenicity and drug resistance. Therefore, understanding the underlying reasons for C. auris heterogeneity and applying effective antifungal stewardship could play a major role in controlling this pathogen.

Lack of fermentation in antemortem blood samples stored unstoppered in various locations

A common defense challenge when antemortem blood ethanol results are presented at trial is the assertion that ethanol was formed in the blood tube after the blood draw through fermentation of the blood glucose by Candida albicans (C. Albicans). In contrast, decades of research into the stability of ethanol in antemortem blood collected for forensic purposes have consistently shown that any analytically significant change in ethanol concentration is a decrease and initially, ethanol-negative blood remains ethanol-negative with storage. For there to be any possibility of fermentation to occur by C. Albicans in an antemortem blood sample there must be a plausible mechanism for introduction of C. Albicans into the blood. One mechanism proffered at trial is environmental contamination resulting from ambient air drawn into the evacuated blood collection tube. Blood was drawn from ethanol-free individuals into 6 and 10-ml gray-top Vacutainer® tubes containing sodium fluoride and 6-ml Vacutainer® tubes without a preservative. Following the blood draws, the tubes were stored unstoppered at room temperature for 24 or 48 h in various locations. Following unstoppered storage, the tubes were stoppered and stored refrigerated (~4°C), left at room temperature (~22°C), or placed in an oven (37°C). The refrigerated blood was analyzed for ethanol using headspace gas chromatography after both 5 days and 32 months. Unrefrigerated blood samples were analyzed after being stored at room temperature or in an oven for up to 30 days. Ethanol was not detected in any of the blood tubes after storage regardless of storage time, storage temperature, or preservative concentration.

Epidemiological Characterization of Clinical Fungal Isolates from Pauls Stradinš Clinical University Hospital, Latvia: A 4-Year Surveillance Report

Nosocomial fungal infections are an emerging global public health threat that requires urgent attention and proper management. With the limited availability of treatment options, it has become necessary to understand the emerging epidemiological trends, mechanisms, and risk factors. However, very limited surveillance reports are available in the Latvian and broader European context. We therefore conducted a retrospective analysis of laboratory data (2017-2020) from Pauls Stradinš Clinical University Hospital (PSCUH), Riga, Latvia, which is one of the largest public multispecialty hospitals in Latvia. A total of 2278 fungal isolates were analyzed during the study period, with Candida spp. comprising 95% of the isolates, followed by Aspergillus spp. and Geotrichum spp. Amongst the Candida spp., C. albicans and C. glabrata made up about 75% of the isolates. The Department of Lung Diseases and Thoracic Surgery had the highest caseload followed by Intensive Care Department. Majority of the fungal isolates were collected from the bronchoalveolar lavage (37%), followed by urine (19%) and sputum (18%) samples. A total of 34 cases of candidemia were noted during the study period with C. albicans being the most common candidemia pathogen. Proper surveillance of emerging epidemiological trends serve as the most reliable and powerful cornerstone towards tackling this emerging threat.

Microbial Air Quality in Healthcare Facilities

There is increasing evidence that indoor air quality and contaminated surfaces provide an important potential source for transmission of pathogens in hospitals. Airborne hospital microorganisms are apparently harmless to healthy people. Nevertheless, healthcare settings are characterized by different environmental critical conditions and high infective risk, mainly due to the compromised immunologic conditions of the patients that make them more vulnerable to infections. Thus, spread, survival and persistence of microbial communities are important factors in hospital environments affecting health of inpatients as well as of medical and nursing staff. In this paper, airborne and aerosolized microorganisms and their presence in hospital environments are taken into consideration, and the factors that collectively contribute to defining the infection risk in these facilities are illustrated.

Persistence of Pathogens on Inanimate Surfaces: A Narrative Review

For the prevention of infectious diseases, knowledge about transmission routes is essential. In addition to respiratory, fecal-oral, and sexual transmission, the transfer of pathogens via surfaces plays a vital role for human pathogenic infections-especially nosocomial pathogens. Therefore, information about the survival of pathogens on surfaces can have direct implications on clinical measures, including hygiene guidelines and disinfection strategies. In this review, we reviewed the existing literature regarding viral, bacterial, and fungal persistence on inanimate surfaces. In particular, the current knowledge of the survival time and conditions of clinically relevant pathogens is summarized. While many pathogens persist only for hours, common nosocomial pathogens can survive for days to weeks under laboratory conditions and thereby potentially form a continuous source of transmission if no adequate inactivation procedures are performed.

Recontamination of Healthcare Surfaces by Repeated Wiping with Biocide-Loaded Wipes: "One Wipe, One Surface, One Direction, Dispose" as Best Practice in the Clinical Environment

The wiping of high-touch healthcare surfaces made of metals, ceramics and plastics to remove bacteria is an accepted tool in combatting the transmission of healthcare-associated infections (HCAIs). In practice, surfaces may be repeatedly wiped using a single wipe, and the potential for recontamination may be affected by various factors. Accordingly, we studied how the surface to be wiped, the type of fibre in the wipe and how the presence of liquid biocide affected the degree of recontamination. Experiments were conducted using metal, ceramic and plastic healthcare surfaces, and two different wipe compositions (hygroscopic and hydrophilic), with and without liquid biocide. Despite initially high removal efficiencies of >70% during initial wiping, all healthcare surfaces were recontaminated with E. coli, S. aureus and E. faecalis when wiped more than once using the same wipe. Recontamination occurred regardless of the fibre composition of the wipe or the presence of a liquid biocide. The extent of recontamination by E. coli, S. aureus and E. faecalis bacteria also increased when metal healthcare surfaces possessed a higher microscale roughness (<1 μm), as determined by Atomic Force Microscopy (AFM). The high propensity for healthcare surfaces to be re-contaminated following initial wiping suggests that a “One wipe, One surface, One direction, Dispose” policy should be implemented and rigorously enforced.

Candida auris: an Emerging Fungal Pathogen

Candida auris has emerged globally as a multidrug-resistant health care-associated fungal pathogen. Recent reports highlight ongoing challenges due to organism misidentification, high rates of antifungal drug resistance, and significant patient mortality. The predilection for transmission within and between health care facilities possibly promoted by virulence factors that facilitate skin colonization and environmental persistence is unique among Candida species. This minireview details the global emergence of C. auris and discusses issues relevant to clinical microbiology laboratories, hospital infection control, and antimicrobial stewardship efforts.

Water quality and antifungal susceptibility of opportunistic yeast pathogens from rivers

Yeasts from water sources have been associated with diseases ranging from superficial mucosal infections to life threatening diseases. The aim of this study was to determine the water quality as well as diversity and antifungal susceptibility of yeasts from two rivers. Yeast levels and physico-chemical parameter data were analyzed by principal component analysis to determine correlations between physico-chemical data and yeast levels. Yeast morphotypes were identified by biochemical tests and 26S rRNA gene sequencing. Disk diffusion antifungal susceptibility tests were conducted. Physico-chemical parameters of the water were within target water quality range (TWQR) for livestock farming. For irrigational use, total dissolved solids and nitrates were not within the TWQR. Yeast levels ranged between 27 ± 10 and 2,573 ± 306 cfu/L. Only non-pigmented, ascomycetous yeasts were isolated. Saccharomyces cerevisiae and Candida glabrata were most frequently isolated. Several other opportunistic pathogens were also isolated. A large number of isolates were resistant to azoles, especially fluconazole, but also to other antifungal classes. Candida species were resistant to almost all the antifungal classes. These water sources are used for recreation and religious as well as for watering livestock and irrigation. Of particular concern is the direct contact of individuals with opportunistic yeast, especially the immune-compromised. Resistance of these yeast species to antifungal agents is a further health concern.

Paper money and coins as potential vectors of transmissible disease

Paper currency and coins may be a public health risk when associated with the simultaneous handling of food and could lead to the spread of nosocomial infections. Banknotes recovered from hospitals may be highly contaminated by Staphylococcus aureus. Salmonella species, Escherichia coli and S. aureus are commonly isolated from banknotes from food outlets. Laboratory simulations revealed that methicillin-resistant S. aureus can easily survive on coins, whereas E. coli, Salmonella species and viruses, including human influenza virus, Norovirus, Rhinovirus, hepatitis A virus, and Rotavirus, can be transmitted through hand contact. Large-scale, 16S rRNA, metagenomic studies and culturomics have the capacity to dramatically expand the known diversity of bacteria and viruses on money and fomites. This review summarizes the latest research on the potential of paper currency and coins to serve as sources of pathogenic agents.

Calcineurin controls hyphal growth, virulence, and drug tolerance of Candida tropicalis

Candida tropicalis, a species closely related to Candida albicans, is an emerging fungal pathogen associated with high mortality rates of 40 to 70%. Like C. albicans and Candida dubliniensis, C. tropicalis is able to form germ tubes, pseudohyphae, and hyphae, but the genes involved in hyphal growth machinery and virulence remain unclear in C. tropicalis. Recently, echinocandin- and azole-resistant C. tropicalis isolates have frequently been isolated from various patients around the world, making treatment difficult. However, studies of the C. tropicalis genes involved in drug tolerance are limited. Here, we investigated the roles of calcineurin and its potential target, Crz1, for core stress responses and pathogenesis in C. tropicalis. We demonstrate that calcineurin and Crz1 are required for hyphal growth, micafungin tolerance, and virulence in a murine systemic infection model, while calcineurin but not Crz1 is essential for tolerance of azoles, caspofungin, anidulafungin, and cell wall-perturbing agents, suggesting that calcineurin has both Crz1-dependent and -independent functions in C. tropicalis. In addition, we found that calcineurin and Crz1 have opposite roles in controlling calcium tolerance. Calcineurin serves as a negative regulator, while Crz1 plays a positive role for calcium tolerance in C. tropicalis.

Candida tropicalis in human disease

Candida tropicalis is one of the more common Candida causing human disease in tropical countries; the frequency of invasive disease varies by geography causing 3--66% of candidaemia. C. tropicalis is taxonomically close to C. albicans and shares many pathogenic traits. C. tropicalis is particularly virulent in neutropenic hosts commonly with hematogenous seeding to peripheral organs. For candidaemia and invasive candidiasis amphotericin B or an echinocandin are recommended as first-line treatment, with extended-spectrum triazoles acceptable alternatives. Primary fluconazole resistance is uncommon but may be induced on exposure. Physicians in regions where C. tropicalis is common need to be mindful of this lesser-described pathogen.

Are computer keyboards a cross-infection risk in a dental clinic?

Computers in dental surgeries located within the patient treatment room could potentially pose a risk of cross-infection of patients and operators. The aims of this investigation were to determine the degree of contamination of computer keyboards located in clinics and study rooms in a teaching dental hospital, to determine the survival time of micro-organisms on keyboards and to compare the efficiency of two common disinfectants in disinfecting keyboards. All keyboards were found to be contaminated with a variety of micro-organisms including Staphylococcus aureus, coagulasenegative staphylococci, Gram-negative rods and cocci. A range of Gram-positive and -negative bacteria and Candida albicans were able to survive up to 10 days in dried suspensions on computer keys. Seventy per cent isopropanol wipes proved effective in reducing the numbers of viable test organisms on keys by at least 96% and reducing contamination of keyboards in routine use. The data suggest that computers in dental study areas and clinics act as reservoirs of potentially pathogenic organisms including S. aureus and should be regularly disinfected to reduce the risk of cross-infection.

Biometric fingerprinting for visa application: device and procedure are risk factors for infection transmission

BACKGROUND

Biometric fingerprint identity verification is currently introduced in visa application and entry screening at border control. The system implies physical contact between the skin and the surface of the fingerprint-capturing and reading devices.

AIM

To assess the risk of infection transmission through fingerprinting.

METHODS

The medical literature was reviewed for the potential of microorganisms to be carried on the skin of hands in the community, to be transferred from hands to inanimate surfaces, to survive on surfaces, and to be transferred in doses exceeding the infectious dose. The fingerprinting procedures as currently applied were reviewed.

RESULTS

Factors that favor transfer of microorganisms are large skin-surface contact between flat fingers (2 x 20 cm(2)) and fingerprint-capturing device, nonporous contact surface, large overlap of contact surface and short turnaround time between successive applicants, high contact pressure, and difficulties to disinfect devices. Transmission risk exists for enteric viruses (rotavirus, norovirus, and hepatitis A virus), respiratory viruses (respiratory syncytial virus, rhinovirus, influenza virus, etc.), and enteropathogenic bacteria with low infectious doses (Shigella dysenteriae, Enterohemorrhagic Escherichia coli, etc.). Using Monte Carlo risk analysis on US data, transmission of human rotavirus is estimated at 191 [95% credible intervals (CI) 0-289] per million fingerprint-capturing procedures. Application of 70% isopropyl hand rub and 85% ethanol hand gel reduces the risk to 77 (95% CI 0-118) and 0.3 (95% CI 0-0.3) transmissions per million procedures, respectively.

CONCLUSIONS

The fingerprinting procedure as currently used is associated with a risk of infection transmission. Simple hygienic measures can considerably reduce this transmission risk.

How long do nosocomial pathogens persist on inanimate surfaces? A systematic review

BACKGROUND

Inanimate surfaces have often been described as the source for outbreaks of nosocomial infections. The aim of this review is to summarize data on the persistence of different nosocomial pathogens on inanimate surfaces.

METHODS

The literature was systematically reviewed in MedLine without language restrictions. In addition, cited articles in a report were assessed and standard textbooks on the topic were reviewed. All reports with experimental evidence on the duration of persistence of a nosocomial pathogen on any type of surface were included.

RESULTS

Most gram-positive bacteria, such as Enterococcus spp. (including VRE), Staphylococcus aureus (including MRSA), or Streptococcus pyogenes, survive for months on dry surfaces. Many gram-negative species, such as Acinetobacter spp., Escherichia coli, Klebsiella spp., Pseudomonas aeruginosa, Serratia marcescens, or Shigella spp., can also survive for months. A few others, such as Bordetella pertussis, Haemophilus influenzae, Proteus vulgaris, or Vibrio cholerae, however, persist only for days. Mycobacteria, including Mycobacterium tuberculosis, and spore-forming bacteria, including Clostridium difficile, can also survive for months on surfaces. Candida albicans as the most important nosocomial fungal pathogen can survive up to 4 months on surfaces. Persistence of other yeasts, such as Torulopsis glabrata, was described to be similar (5 months) or shorter (Candida parapsilosis, 14 days). Most viruses from the respiratory tract, such as corona, coxsackie, influenza, SARS or rhino virus, can persist on surfaces for a few days. Viruses from the gastrointestinal tract, such as astrovirus, HAV, polio- or rota virus, persist for approximately 2 months. Blood-borne viruses, such as HBV or HIV, can persist for more than one week. Herpes viruses, such as CMV or HSV type 1 and 2, have been shown to persist from only a few hours up to 7 days.

CONCLUSION

The most common nosocomial pathogens may well survive or persist on surfaces for months and can thereby be a continuous source of transmission if no regular preventive surface disinfection is performed.

Epidemiologic and molecular characterization of an outbreak of Candida parapsilosis bloodstream infections in a community hospital

Candida parapsilosis is an important cause of bloodstream infections in the health care setting. We investigated a large C. parapsilosis outbreak occurring in a community hospital and conducted a case-control study to determine the risk factors for infection. We identified 22 cases of bloodstream infection with C. parapsilosis: 15 confirmed and 7 possible. The factors associated with an increased risk of infection included hospitalization in the intensive care unit (adjusted odds ratio, 16.4; 95% confidence interval, 1.8 to 148.1) and receipt of total parenteral nutrition (adjusted odds ratio, 9.2; 95% confidence interval, 0.9 to 98.1). Samples for surveillance cultures were obtained from health care worker hands, central venous catheter insertion sites, and medical devices. Twenty-six percent of the health care workers surveyed demonstrated hand colonization with C. parapsilosis, and one hand isolate was highly related to all case-patient isolates by tests with the DNA probe Cp3-13. Outbreak strain isolates also demonstrated reduced susceptibilities to fluconazole and voriconazole. This largest known reported outbreak of C. parapsilosis bloodstream infections in adults resulted from an interplay of host, environment, and pathogen factors. Recommendations for control measures focused on improving hand hygiene compliance.

Epidemiologic background of hand hygiene and evaluation of the most important agents for scrubs and rubs

The etiology of nosocomial infections, the frequency of contaminated hands with the different nosocomial pathogens, and the role of health care workers' hands during outbreaks suggest that a hand hygiene preparation should at least have activity against bacteria, yeasts, and coated viruses. The importance of efficacy in choosing the right hand hygiene product is reflected in the new Centers for Disease Control and Prevention guideline on hand hygiene (J. M. Boyce and D. Pittet, Morb. Mortal. Wkly. Rep. 51:1-45, 2002). The best antimicrobial efficacy can be achieved with ethanol (60 to 85%), isopropanol (60 to 80%), and n-propanol (60 to 80%). The activity is broad and immediate. Ethanol at high concentrations (e.g., 95%) is the most effective treatment against naked viruses, whereas n-propanol seems to be more effective against the resident bacterial flora. The combination of alcohols may have a synergistic effect. The antimicrobial efficacy of chlorhexidine (2 to 4%) and triclosan (1 to 2%) is both lower and slower. Additionally, both agents have a risk of bacterial resistance, which is higher for chlorhexidine than triclosan. Their activity is often supported by the mechanical removal of pathogens during hand washing. Taking the antimicrobial efficacy and the mechanical removal together, they are still less effective than the alcohols. Plain soap and water has the lowest efficacy of all. In the new Centers for Disease Control and Prevention guideline, promotion of alcohol-based hand rubs containing various emollients instead of irritating soaps and detergents is one strategy to reduce skin damage, dryness, and irritation. Irritant contact dermatitis is highest with preparations containing 4% chlorhexidine gluconate, less frequent with nonantimicrobial soaps and preparations containing lower concentrations of chlorhexidine gluconate, and lowest with well-formulated alcohol-based hand rubs containing emollients and other skin conditioners. Too few published data from comparative trials are available to reliably rank triclosan. Personnel should be reminded that it is neither necessary nor recommended to routinely wash hands after each application of an alcohol-based hand rub. Long-lasting improvement of compliance with hand hygiene protocols can be successful if an effective and accessible alcohol-based hand rub with a proven dermal tolerance and an excellent user acceptability is supplied, accompanied by education of health care workers and promotion of the use of the product.

Investigation of single-use versus reusable infectious waste containers as potential sources of microbial contamination

BACKGROUND

Laws require that infectious waste be segregated from noninfectious waste. Companies certified to dispose of infectious waste offer both reusable and single-use containers. The focus of this study was to determine if there would be a microbiologic advantage to the use of one type of container over another in a burn hospital.

METHODS

Monthly swab cultures were taken from the tops of >250 infectious waste containers during 2 years. Bacteria and fungi were identified. In a substudy swab cultures were taken from an area of reusable tops before and after cleaning to evaluate the efficacy of cleaning on both the number and type of microbes present. Infection rates for acute patients were compared before and after control measures were instituted to decrease microbial transfer from infectious waste containers to patients.

RESULTS

Cultures taken from reusable boxes when received from the container company showed that >99% were contaminated with bacteria or fungi; most were normal environmental or skin flora, but some cultures showed microorganisms that can be potentially harmful to patients with compromised immunity. Wiping the lids with a phenolic disinfectant decreased both the total microbial load (P <.001) and the variety of microbes present (P <.001). In contrast, only 10% of the incoming single-use boxes showed any contamination. Infection rates dropped from 5.8 to 3.2 per 100 burn patients (P <.05) after the institution of cleaning and other changes made to decrease the possibility of microbial transfer from the infectious waste boxes to the patients.

CONCLUSIONS

Upon delivery, significantly fewer single-use infectious waste boxes were contaminated than reusable ones (P <.001). Extra infection control measures were needed when reusable infectious waste boxes were used in areas housing patients with compromised immunity. Facilities need be aware of the possible contamination of reusable infectious waste containers with microorganisms capable of causing nosocomial infections in patients who are compromised.

Electrophoretic karyotyping of Candida albicans strains isolated from premature infants and hospital personnel in a neonatal intensive care unit

Electrophoretic karyotyping was used to compare DNA probes of yeasts isolated from blood of preterm neonates (n = 66) in a neonatal intensive care unit (NICU) and from the hands of healthy hospital personnel (n = 10). The yeasts were identified as Candida albicans using standard laboratory methods. DNA was extracted from yeasts and isolation of identical DNA strains from the pairs nurse-neonate suggested that one nurse transmitted one yeast strain by her hands to three neonates. Four neonates harbored two identical strains originating from two nurses, i.e. each nurse transmitted the same strain to two neonates. In the additional 7 cases transmission of 1 yeast strain by 1 nurse to 1 neonate was observed. Our data suggest that nonperinatal nosocomial transmission of C. albicans occurs in neonates, possibly via cross-contamination being transferred on hands of health care workers. The importance of careful hand washing of staff (health care workers) and other infection-control procedures (to prevent the nosocomial transmission of pathogens in the NICU environment) is emphasized.

A quantitative study of the survival of two species of Candida on porous and non-porous environmental surfaces and hands

AIMS

In spite of the importance of many species of Candida as human pathogens, little is known about their ability to survive on animate and inanimate surfaces. Such information is essential in understanding the vehicles and modes of their spread, and in designing proper infection control strategies against them. The aim of this study was to generate comparative quantitative data in this regard.

METHODS AND RESULTS

The survival of one clinical isolate each of Candida albicans and C. parapsilosis on two types of hard inanimate surfaces (glass and stainless steel) and two types of fabrics (100% cotton and a blend of 50% cotton and 50% polyester) was evaluated under ambient conditions (air temperature 22 +/- 2 degrees C; relative humidity 45-62%) using quantitative test protocols. The survival of C. albicans was also assessed on human skin, using the fingerpads of adult volunteers as carriers. Each carrier surface received 10 microl of the test suspension containing a soil load to simulate body fluids. When dried on glass and stainless steel carriers, C. albicans and C. parapsilosis remained viable for at least three and 14 days, respectively. Both species could survive for at least 14 days on both types of fabric. On the skin, 20% of the viable C. albicans remained detectable one hour post-inoculation.

SIGNIFICANCE AND IMPACT OF THE STUDY

This quantitative and comparative study demonstrated the potential for, and differences in the ability of clinically significant species of Candida to remain viable on porous and non-porous inanimate surfaces as well as on human hands. These results should help in understanding the epidemiology of nosocomial infections due to Candida, and in designing better prevention and control strategies against them.

Basic microbiologic and infection control information to reduce the potential transmission of pathogens to patients via computer hardware

Computer technology from the management of individual patient medical records to the tracking of epidemiologic trends has become an essential part of all aspects of modern medicine. Consequently, computers, including bedside components, point-of-care testing equipment, and handheld computer devices, are increasingly present in patients' rooms. Recent articles have indicated that computer hardware, just as other medical equipment, may act as a reservoir for microorganisms and contribute to the transfer of pathogens to patients. This article presents basic microbiological concepts relative to infection, reviews the present literature concerning possible links between computer contamination and nosocomial colonizations and infections, discusses basic principles for the control of contamination, and provides guidelines for reducing the risk of transfer of microorganisms to susceptible patient populations.

Survival of some medically important fungi on hospital fabrics and plastics

Tests of the survival of Candida spp., Aspergillus spp., a Fusarium sp., a Mucor sp., and a Paecilomyces sp. on hospital fabrics and plastics indicated that viability was variable, with most fungi surviving at least 1 day but many living for weeks. These findings reinforce the need for appropriate disinfection and conscientious contact control precautions.

[The role of the laboratory in the diagnosis and prevention of fungal infections]

Fungal infections account for an increasing fraction of nosocomial infections. The laboratory is essential to ascertain the diagnosis. Significant progress has been recently achieved in direct diagnostic tools (better sensitivity of direct examination, development of chromogenic identification media). Diagnostic sensitivity of blood cultures can be increased with the use of special fungal media for culture. However, indirect diagnostic methods remain unsatisfactory, even though some new data support the usefulness of simultaneous detection of circulating antigens and corresponding antibodies. In the future, the contribution of molecular biology techniques could be of great interest, either in the diagnostic (detection of fungal DNA in the serum) or in the identification of species. Last but not least, molecular typing allows a precise monitoring of fungal ecology that could prove useful to the understanding of the physiopathology of infections and to the anticipation and prevention of epidemic outbreaks.

[Epidemiology and prognostic factors of systemic candidiasis in intensive care units]

The incidence of systemic Candida infections in patients requiring intensive care has substantially increased in recent years. Epidemiologic evidence for this trend is consistent in american as european studies. An emergence of non-albicans species is also demonstrated. Systemic Candida infections are associated with a high mortality and morbidity, an increased length of stay and a heavy workload for the ICU staff. A number of studies have identified risk factors for transition from mere colonisation to infection and prognostic factors for mortality. A review of published data is given.

Oral colonization by Candida albicans

Candida albicans is a commensal yeast normally present in small numbers in the oral flora of a large proportion of humans. Colonization of the oral cavity by C. albicans involves the acquisition and maintenance of a stable yeast population. Micro-organisms are continually being removed from the oral cavity by host clearance mechanisms, and so, in order to survive and inhabit this eco-system, C. albicans cells have to adhere and replicate. The oral cavity presents many niches for C. albicans colonization, and the yeast is able to adhere to a plethora of ligands. These include epithelial and bacterial cell-surface molecules, extracellular matrix proteins, and dental acrylic. In addition, saliva molecules, including basic proline-rich proteins, adsorbed to many oral surfaces promote C. albicans adherence. Several adhesins present in the C. albicans cell wall have now been partially characterized. Adherence involves lectin, protein-protein, and hydrophobic interactions. As C. albicans cells evade host defenses and colonize new environments by penetrating tissues, they are exposed to new adherence receptors and respond by expressing alternative adhesins. The relatively small number of commensal Candida cells in the oral flora raises the possibility that strategies can be devised to prevent oral colonization and infection. However, the variety of oral niches and the complex adherence mechanisms of the yeast mean that such a goal will remain elusive until more is known about the contribution of each mechanism to colonization.

Nosocomial fungal infections: candidemia

Candida species are frequently encountered as part of the human commensal flora. Colonization mostly precedes candidemia and is an independent risk factor for the development of candidemia. Genotyping methods showed the similarity between colonizing and infecting strains, thus making endogenous origin likely, though exogenous sources like total parenteral nutrition also have been described. Health care workers (HCWs) play an important role in the transmission of yeasts. Candida species are frequently isolated from the hands of HCWs and can be transmitted from hands to patients. Granulocytopenia and damage of the mucosal lining resulting from intensive chemotherapy due to cancer, the increasing use of broad spectrum antibiotics, and the use of intravenous catheters are other important risk factors for the development of candidemia. Candidemia is associated with a high mortality and prolonged hospitalization. Therefore, and because of the high frequency of dissemination, all candidemias should be treated. Amphotericin B was considered the standard drug for the systemic treatment of candidemia. Fluconazole has been shown to be an effective and safe alternative in non-neutropenic patients. 5-Fluorocytosine has been used in combination with amphotericin B in the treatment of deep-seated infections. Liposomal formulations of amphotericin B and other new antifungal drugs currently are under investigation. C. albicans is the most frequently isolated Candida species, although the proportion of infections caused by non-C. albicans species is increasing. Also, there are reports of development of resistance to amphotericin B. C. lusitaniae is known for primary resistance and the development of resistance to amphotericin B. Development of resistance to fluconazole is mainly seen in AIDS patients with recurrent oropharyngeal candidiasis who receive longer courses of therapy.

Prophylaxis of fungal infections

Considering the high morbidity and mortality of deep-seated opportunistic mycoses in severely immunosuppressed patients, strategies for prophylaxis appear to be indicated. Exposure to Aspergillus spp. can be prevented by air filtration which has been shown to reduce the rate of infection. However, Candida infections are predominantly caused by colonizing fungi; therefore drug prophylaxis is more promising. Prospective randomized studies proved the effectiveness of fluconazole (FLU) to prevent infections in patients after bone marrow transplantation.

Epidemiology of candidiasis

The increase in infections due to Candida over the past decade is significant. This is particularly true for hospitalized patients where the rate of blood-stream infection due to Candida spp. has increased by almost 500% over the decade of the 1980s. This increase is accompanied by a significant excess mortality and a prolonged length of stay in the hospital. This trend continues into the 1990s where in the US Candida spp. remains the fourth most common blood-stream pathogen, accounting for 8% of all hospital-acquired blood-stream infections. Notably, more than one-third of candidal blood-stream infections are caused by species other than C. albicans. The majority of these infections arise from an endogenous focus of colonization; however, the documentation of nosocomial transmission or 'cross-infection' and the recognition of resistance to antifungal agents pose new and significant problems. Recent studies indicate that Candida may be isolated from the hands of 15-54% of health care workers in the intensive care unit setting and that the strain of Candida carried on the hands may be shared by infected patients. These studies are facilitated by molecular typing and careful epidemiological investigation and suggest that cross-infection is an important and preventable feature of candidal blood-stream infection. Both endogenous and exogenous sources of infection are now well-documented and such information should help direct measures to prevent infections in high risk individuals.