Microbiological factors influencing the outcome of nosocomial bloodstream infections: a 6-year validated, population-based model

Candida glabrata and Candida krusei fungemia after high-risk allogeneic marrow transplantation: no adverse effect of low-dose fluconazole prophylaxis on incidence and outcome

Candidemia is a serious complication in patients following allogeneic blood, marrow, and organ transplantation. Fourteen patients developed nosocomial fungemia among 204 allogeneic marrow transplants performed during 1997-1999. Incidence of hematogenous candidiasis was 6.8 per 100 allogeneic BMT. All 14 had an indwelling central venous catheter (CVC) and fluconazole (100-200 mg daily) was given prophylactically. In 11 (78.5%) neutropenic patients, duration between agranulocytosis and diagnosis of fungemia was (median, +/- s.d.) 10 +/- 8 days. Candida glabrata (53.3%) was the most common yeast species, followed by C. krusei (33.3%), and C. parapsilosis (13.3%). Candida albicans was conspicuously absent. Ten patients (71.4%) had primary transplant-related complication (>2 days) including hemolytic uremic syndrome/thrombotic thrombocytopenic purpura (HUS/TTP) (n = 5), severe hemorrhagic cystitis (n = 3), and bacteremia (n = 2). Seven (50.0%) patients expired and in three (21.4%) deaths were attributed to fungemia. The impact of a primary transplant-related complication on short-term survival in this setting was not significant (P = 0.07) (HUS/TTP (P > 0.5); neutropenia (P > 0.5); GVHD (P = 0.35)). Removal of CVC did not alter outcome in our group (P > or = 0.5) although in patients with persistent fungemia (>72 h), and those with preceding bacteremia, mortality was significantly higher (P = 0.002). Conventional prognosticators of poor outcome did not adversely effect short-term survival in our transplant recipients with hematogenous candidiasis. The predominance of C. glabrata and C. krusei breakthrough infections was similar to what is seen with high-dose fluconazole (400 mg) prophylaxis, and no adverse effects of low-dose fluconazole in terms of increased incidence of non-susceptible Candida species was seen.

Rationale for combination antifungal therapy

The relentless increase of invasive fungal infections and poor outcomes associated with available antifungal agents prompted the search for better therapeutic strategies. Combining antifungal drugs was recommended as a means to enhance efficacy in a variety of invasive infections including cryptococcosis, candidiasis, and aspergillosis. With the exception of cryptococcal meningitis, data from controlled clinical trials supporting such combinations are sparse. Moreover, little consensus exists regarding which combinations are synergistic or antagonistic in vitro and in vivo. Based on available data, several principles underlie these combinations.

Prospective study of Candida species in patients at a comprehensive cancer center

Since most nosocomial systemic yeast infections arise from the endogenous flora of the patient, we prospectively evaluated the species stratification and antifungal susceptibility profile of Candida spp. associated with heavy colonization and systemic infection in patients at Memorial Sloan-Kettering Cancer Center in New York. A total of 349 Candida isolates were obtained from 223 patients during the later half of 1998. Cancer was the most common underlying disease, occurring in 91% of the patients, including 61.8% with organ and 23.7% with hematological malignancies; 4.4% of the patients had AIDS. Candida albicans was the predominant species (67.3%); among 114 non-albicans Candida spp., C. glabrata (45.6%) was the most frequent, followed by C. tropicalis (18.4%), C. parapsilosis (16.6%), and C. krusei (9.6%). The overall resistance to triazole-based agents among all yeast isolates was 9.4 and 10.8% for fluconazole and itraconazole, respectively. A total of 5% of C. albicans strains were resistant to triazole antifungals, whereas 30.8 and 46.2% of C. glabrata strains were resistant to fluconazole (MIC > or = 64 microg/ml) and itraconazole (MIC > or = 1 microg/ml), respectively. A significant association was observed between prior treatment with triazole and isolation of fluconazole-resistant C. albicans (P = 0.005, OR 36), although this relationship was not seen in C. glabrata isolates (P = 0.4). This study reinforces the importance of periodic, prospective surveillance of clinical fungal isolates to determine appropriate prophylactic, empiric, and preemptive antifungal therapy for the highly susceptible patient population.

Outcomes of primary and catheter-related bacteremia. A cohort and case-control study in critically ill patients

We studied a cohort of 2201 patients hospitalized in 15 French intensive care units (ICUs) for > or = 48 h during a 4-mo period to assess the incidence and outcomes of primary and definite catheter-related bloodstream (CRB) or secondary nosocomial bloodstream infection (NBSI). Variables associated with ICU death and duration of stay were determined by logistic regression, and attributable mortality and length of stay (LOS) from a nested matched case-control (96 pairs) study, stratified on the source of bacteremia. Bacteremia occurred in 5% (95% CI 4.1-6%) of patients with > or = 48 h ICU stay. Primary, CRB, and secondary NBSI accounted for 29%, 26%, and 45% of the 111 episodes, respectively. NBSI was associated with a markedly increased risk of death (OR = 4.6; 95% CI 2.9-7.1) and an attributable mortality of 35% (95% CI, 28%-47%). In the case-control study, the excess mortality was 20% (p = 0.03) in patients with primary bacteremia and CRB, and 55% (p < 0.001) for secondary bacteremia; in patients with CRB only, the excess mortality was 11.5%. The median excess ICU LOS in survivors of NBSI was 9.5 d, and was similar, irrespective of its source. The risk of mortality associated with primary and catheter-related bacteremia appears much lower than that of secondary bacteremia, but is sizable, and the excess LOS incurred by the various categories of bacteremia is comparable. Differentiating catheter-related bacteremia from both primary and other secondary bacteremia appears warranted in studies conducted in critically ill patients.

[Candidiasis among non-neutropenic patients: from colonization to infection]

Invasive candidiasis is a dread complication in hospitalized patients, characterized by a mortality comparable to that of septic shock (40% to 60%). Its incidence in hospitalized patients is 0.5/1000 admissions, but it complicates about 10 per 1,000 admissions in critical care where it represents 10% to 15% of all nosocomial infections. Although a high proportion of hospitalized patients may become colonized with Candida spp, the clinical signs of infection manifest only late, rending it difficult to diagnose. A better knowledge of their pathophysiology and the availability of triazoles compounds, less toxic than amphotericin B, allowed the concept of early empirical or preemptive treatment. These strategies are based on the prompt identification of risk factors and require continuous attention from skilled physicians. However, the prescription of triazoles has to be restricted to carefully selected groups of patients to avoid the emergence and the dissemination of resistant strains.

Real-time identification of Pseudomonas aeruginosa direct from clinical samples using a rapid extraction method and polymerase chain reaction (PCR)

Pseudomonas aeruginosa has emerged as one of the most problematic Gram-negative nosocomial pathogens. Bacteremia caused by P. aeruginosa is clinically indistinguishable from other Gram-negative infections although the mortality rate is higher. This microorganism is also inherently resistant to common antibiotics. Standard bacterial identification and susceptibility testing is normally a 48-hour process and difficulty sometimes exists in rapidly and accurately identifying antimicrobial resistance. The Polymerase Chain Reaction (PCR) is a rapid and simple process for the amplification of target DNA sequences. However, many sample preparation methods are unsuitable for the clinical laboratory because they are not cost effective, take too long to perform, or do not provide a good template for PCR. Our goal was to provide same-day results to facilitate rapid diagnosis. In this report, we have utilized our rapid DNA extraction method to generate bacterial DNA direct from clinical samples for PCR. The lower detection level for P. aeruginosa was estimated to be 10 CFU/ml. In addition, we wanted to compare the results of a new rapid-cycle DNA thermocycler that uses continuous fluorescence monitoring with the results of standard thermocycling. We tested 40 clinical isolates of P. aeruginosa and 18 non-P. aeruginosa isolates received in a blinded fashion. Coded data revealed that there was 100% correlation in both the rapid-cycle DNA thermocycling and standard thermocycling when compared to standard clinical laboratory results. In addition, total results turn-around time was less than 1 hour. Specific identification of P. aeruginosa was determined using intragenic primer sets for bacterial 16S rRNA and Pseudomonas outer-membrane lipoprotein gene sequences. The total cost of our extraction method and PCR was $2.22 per sample. The accuracy and rapidness of this DNA-extraction method, with its PCR-based identification system, make it an ideal candidate for use in the clinical laboratory.

Four year prospective evaluation of nosocomial bacteremia: epidemiology, microbiology, and patient outcome

A prospective study of all patients with clinically significant nosocomial bacteremia at one institution from 1994 to 1997 was performed to: (1) describe the epidemiology and microbiology of nosocomial bacteremias; (2) determine the crude mortality associated with such infections; and (3) identify independent predictors of mortality. Four hundred four episodes of bacteremia occurred in 322 patients; the crude in-hospital mortality was 31%. Coagulase-negative staphylococci, Staphylococcus aureus, and enterococci were the leading pathogens, and intravascular catheters were the most frequently identified source. The highest mortality occurred in patients with candidemia (67%). Independent predictors of mortality included evidence of shock at the time of infection, acquisition of bacteremia in an intensive care unit, a "Do Not Attempt Resuscitation" order, and the presence of certain comorbid conditions (e.g., malignancy, HIV infection). Because many of these infections may be preventable, education of health care providers and strict adherence to established infection control practices are critical.

Epidemiology of bloodstream infections at a cancer center

CONTEXT

Cancer patients are at unusually high risk for developing bloodstream infections (BSI), which are a major cause of in-hospital morbidity and mortality.

OBJECTIVE

To describe the epidemiological characteristics and the etiology of BSI in cancer patients.

DESIGN

Descriptive study.

SETTING

Terciary Oncology Care Center.

PARTICIPANTS

During a 24-month period all hospitalized patients with clinically significant BSI were evaluated in relation to several clinical and demographic factors.

RESULTS

The study enrolled 435 episodes of BSI (349 patients). The majority of the episodes occurred among non-neutropenic patients (58.6%) and in those younger than 40 years (58.2%). There was a higher occurrence of unimicrobial infections (74.9%), nosocomial episodes (68.3%) and of those of undetermined origin (52.8%). Central venous catheters (CVC) were present in 63.2% of the episodes. Overall, the commonest isolates from blood in patients with hematology diseases and solid tumors were staphylococci (32% and 34.7%, respectively). There were 70 episodes of fungemia with a predominance of Candida albicans organisms (50.6%). Fungi were identified in 52.5% of persistent BSI and in 91.4% of patients with CVC. Gram-negative bacilli prompted the CVC removal in 45.5% of the episodes. Oxacillin resistance was detected in 26.3% of Staphylococcus aureus isolates and in 61.8% of coagulase-negative Staphylococcus. Vancomycin-resistant enterococci were not observed. Initial empirical antimicrobial therapy was considered appropriate in 60.5% of the cases.

CONCLUSION

The identification of the microbiology profile of BSI and the recognition of possible risk factors in high-risk cancer patients may help in planning and conducting more effective infection control and preventive measures, and may also allow further analytical studies for reducing severe infectious complications in such groups of patients.

Nosocomial bloodstream infections: organisms, risk factors, and implications

In the last 30 years, the frequency, etiology, and epidemiology of bloodstream infections (BSIs) have changed with the evolution of medical care, particularly among the increasing number of hospitalized patients who require intensive care. Although gram-negative bacilli were the predominant nosocomial pathogens in the 1970s, gram-positive cocci have emerged as a more frequent cause of nosocomial BSIs during the 1980s and 1990s. Many gram-positive cocci associated with nosocomial BSIs are now resistant to commonly used antibiotics. Currently, the 3 most common causes of nosocomial BSIs in the United States are coagulase-negative staphylococci, Staphylococcus aureus, and enterococci. The emergence of vancomycin-resistant staphylococcal infections is of particular concern. In addition, the incidence of methicillin-resistant S. aureus (MRSA) infections appears to be increasing; however, the effect of MRSA infection on mortality in hospitalized patients remains unclear. Therefore, newer, more effective antimicrobial therapies are needed to treat BSIs caused by gram-positive cocci are needed.

Significance of blood stream infection after lung transplantation: analysis in 176 consecutive patients

BACKGROUND

Although infection is a leading cause of death after lung transplantation, very little is known about the incidence, epidemiology, and clinical significance of bloodstream infections in lung transplant recipients.

METHODS

All blood cultures were reviewed in 176 consecutive lung transplant recipients over a 6-year period. Data were obtained from a prospectively collected microbiological database.

RESULTS

Bloodstream infection (BSI) occurred in 25% (44/176) of all lung transplant recipients over the 6-year study period. Staphylococcus aureus, Pseudomonas aeruginosa, and Candida species were the most common bloodstream isolates after lung transplantation. The epidemiology of posttransplant BSI, however, varied considerably between early and late posttransplant time periods and also differed between cystic fibrosis (CF) and non-CF patients. BSI infection after transplantation was associated with significantly worse survival by Kaplan-Meir analysis (P value log rank test=0.0001). In a multivariable logistic regression model, posttransplant BSI was a significant predictor of posttransplant death (odds ratio 5.62, CI 2.41-13.11, P=0.001), independent of other pre- and posttransplant factors.

CONCLUSIONS

Bloodstream infection represents a serious complication after lung transplantation, occurring more frequently than previously recognized, and independently contributing to posttransplant mortality.

Failure of an automated blood culture system to detect nonfermentative gram-negative bacteria

During a 1-year study we observed that both aerobic and anaerobic blood culture bottles from patients were negative by the BacT/Alert system during a 7-day incubation period. However, upon subcultivation of negative bottles, growth of Pseudomonas aeruginosa was detectable. In an attempt to explain this observation, aerobic BacT/Alert Fan bottles were seeded with a defined inoculum (0.5 McFarland standard; 1 ml) of Escherichia coli, Klebsiella pneumoniae, Serratia marcescens, P. aeruginosa, Stenotrophomonas maltophilia, or Acinetobacter baumannii. Half of the inoculated bottles were loaded into the BacT/Alert system immediately, and the remainder were preincubated for 4, 8, 16, and 24 h at 36 degrees C. With preincubation all bottles seeded with the Enterobacteriaceae signaled positive during the next 1.5 h. Organisms in bottles seeded with the nonfermentative species P. aeruginosa and A. baumannii remained undetected by the BacT/Alert system for 7 days. S. maltophilia was detected if the preincubation time was equal or less than 8 h. Without preincubation all bottles seeded with the Enterobacteriaceae or nonfermentative species signaled positive. Since nonfermentative species seem to enter a state of bacteriostasis within the preincubation period, we reasoned that an unknown factor is consumed. Accordingly, a smaller inoculum should allow the detection of nonfermentative species, even after preincubation, and serial dilutions of P. aeruginosa were detected in preincubated bottles. In this case preincubated bottles signaled positive faster than bottles without preincubation. We conclude that all bottles from clinical settings should be subcultured prior to loading to avoid false negatives. An alternative may be preincubation at room temperature.

Bloodstream infections due to Candida species: SENTRY antimicrobial surveillance program in North America and Latin America, 1997-1998

An international program of surveillance of bloodstream infections (BSI) in the United States, Canada, and Latin America detected 306 episodes of candidemia in 34 medical centers (22 in the United States, 6 in Canada, and 6 in Latin America) in 1997 and 328 episodes in 34 medical centers (22 in the United States, 5 in Canada, and 7 in Latin America) in 1998. Of the 634 BSI, 54.3% were due to Candida albicans, 16.4% were due to C. glabrata, 14.9% were due to C. parapsilosis, 8.2% were due to C. tropicalis, 1.6% were due to C. krusei, and 4.6% were due to other Candida spp. The percentage of BSI due to C. albicans decreased very slightly in the United States between 1997 and 1998 (56.2 to 54.4%; P = 0.68) and increased in both Canada (52.6 to 70.1%; P = 0.05) and Latin America (40.5 to 44. 6%; P = 0.67). C. glabrata was the second most common species observed overall, and the percentage of BSI due to C. glabrata increased in all three geographic areas between 1997 and 1998. C. parapsilosis was the third most prevalent BSI isolate in both Canada and Latin America, accounting for 7.0 and 18.5% of BSI, respectively. Resistance to fluconazole (MIC, >/=64 microgram/ml) and itraconazole (MIC, >/=1.0 microgram/ml) was observed infrequently in both 1997 (2.3 and 8.5%, respectively) and 1998 (1.5 and 7.6%, respectively). Among the different species of Candida, resistance to fluconazole and itraconazole was observed in C. glabrata and C. krusei, whereas isolates of C. albicans, C. parapsilosis, and C. tropicalis were all highly susceptible to both fluconazole (98.9 to 100% susceptible) and itraconazole (96.4 to 100% susceptible). Isolates from Canada and Latin America were generally more susceptible to both triazoles than U.S. isolates were. Continued surveillance appears necessary to detect these important changes.

A one-year prospective study of nosocomial bacteraemia in ICU and non-ICU patients and its impact on patient outcome

A one-year, prospective, two-observational cohort study was performed to evaluate the incidence and outcome in hospitalized patients (ICU and non-ICU) of nosocomial bacteraemia, and to assess its prognostic value in the ICU group. A group of 18 098 hospitalized patients and a group of 291 consecutive ICU patients were followed. Prognostic factors were determined using single and multivariable analyses. 109 (90 non-ICU and 19 ICU) patients developed 118 nosocomial bacteraemic episodes. The incidence of nosocomial bacteraemia was 6.0 per 1000 admissions (95% confidence interval (CI): 5-7%) and 65 per 1000 admissions in ICU patients (95% CI: 4.5-8.5%). Gram-positive and Gram-negative bacteria were 63/133 (47%) and 70/133 (53%) of the isolated micro-organisms respectively. Crude mortality rates were 41/109 (38%) with adverse outcome associated with mechanical ventilation (OR: 3.6; 95% CI: 1.4-9.2, P =0.01), neutropenia (OR: 7.7; 95% CI: 0.8-73.1;P =0.07) while gastro-intestinal surgery was associated with an improved outcome (OR: 0.4; 95% CI: 0.16-0.96;P =0.04). Of the 291 ICU patients, 19 acquired 22 episodes of nosocomial bacteraemia, and 18 were referred from the wards with documented nosocomial bacteraemia. Of these 37 bacteraemic patients, 17 (46%) died. When adjusting for predictors of death (SAPS II>/=40, cardiac and neurological failure), nosocomial bacteraemia markedly influence the outcome in ICU patients (OR: 3.4; 95% CI: 1.3-8.7;P =0.010). This study suggests that the outcome of nosocomial bacteraemia in hospitalized patients is poor in ventilated and neutropenic patients and that nosocomial bacteraemia per se influenced outcome in ICU patients.

Rapid identification of bacteria from positive blood cultures by fluorescence-based PCR-single-strand conformation polymorphism analysis of the 16S rRNA gene

Bacteremia continues to result in significant morbidity and mortality, particularly in patients who are immunocompromised. Currently, patients with suspected bacteremia are empirically administered broad-spectrum antibiotics, as definitive diagnosis relies upon the use of blood cultures, which impose significant delays in and limitations to pathogen identification. To address the limitations of growth-based identification, the sequence variability of the 16S rRNA gene of bacteria was targeted for rapid identification of bacterial pathogens isolated directly from blood cultures using a fluorescence-based PCR-single-strand conformation polymorphism (SSCP) protocol. Species-specific SSCP patterns were determined for 25 of the most common bacterial species isolated from blood cultures; these isolates subsequently served as a reference collection for bacterial identification for new cases of bacteremia. A total of 272 blood-culture-positive patient specimens containing bacteria were tested. A previously determined SSCP pattern was observed for 251 (92%) specimens, with 21 (8%) specimens demonstrating SSCP patterns distinct from those in the reference collection. Time to identification from blood culture positivity ranged from 1 to 8 days with biochemical testing, whereas identification by fluorescence-based capillary electrophoresis was obtained as early as 7 h at a calculated cost of $10 (U.S. currency) per specimen when tested in batches of 10. Limitations encountered included the inability to consistently detect mixed cultures as well as some species demonstrating identical SSCP patterns. This method can be applied directly to blood cultures or whole-blood specimens, where early pathogen identification would result in a timely diagnosis with possible implications for patient management costs and the mortality and morbidity of infections.

Trends in antimicrobial susceptibility of bacterial pathogens isolated from patients with bloodstream infections in the USA, Canada and Latin America. SENTRY Participants Group

From January through June of 1998, 4579 bloodstream infections (BSI) due to bacterial pathogens were reported from SENTRY hospitals in Canada, the USA and Latin America. Staphylococcus aureus, Escherichia coli, and coagulase-negative staphylococcus (CoNS) were the most common pathogens, together accounting for 55.2% of all BSI during this time period. Compared with the 5794 BSI reported from SENTRY from January through June of 1997, no major change was seen in the frequencies of occurrence of the most common bacterial causes of BSI. Between 1997 and 1998, the major change in antimicrobial resistance was an increase in oxacillin-resistance in both S. aureus and CoNS in all regions. These data demonstrate widespread antimicrobial resistance in Canada, Latin America and the USA, with a notable increase in oxacillin-resistance among staphylococci. Ongoing surveillance remains essential, and will enhance efforts to limit the scope of this worldwide problem.

Detection of Candida albicans in blood by PCR in a rabbit animal model of disseminated candidiasis

A model of acute disseminated Candida albicans infection in New Zealand rabbits was developed to determine the sensitivity and accuracy of polymerase chain reaction (PCR) assay compared with the lysis-centrifugation blood culture method. Primers used amplify a DNA fragment from the multicopy gene coding for the small subunit rRNA, highly conserved in fungi. The sensitivity of PCR achieved in rabbit blood samples spiked with Candida albicans was 10-50 CFU/100 microL. A nested-PCR increased the limit of detection 10-fold. The sensitivity achieved exclusively with the lysis-centrifugation method (37.5%) was higher than that obtained with PCR (25%), but lower than nested PCR (52.5%). The combination of both techniques, lysis-centrifugation and nested PCR, increased the overall sensitivity rate to 62.5%. These results have demonstrated that, globally, the nested PCR was more sensitive than both single PCR and lysis-centrifugation culture in detecting C. albicans in blood from immunecompetent rabbits with acute disseminated candidosis. PCR could be a useful complementary technique to traditional methods in the early diagnosis of candidemia.

Fluconazole prophylaxis prevents intra-abdominal candidiasis in high-risk surgical patients

OBJECTIVE

To evaluate the efficacy and safety of intravenous fluconazole for the prevention of intra-abdominal Candida infections in high-risk surgical patients.

DESIGN

Randomized, prospective, double-blind, placebo-controlled study.

SETTING

Two university-affiliated hospitals in Switzerland.

PATIENTS

Forty-nine surgical patients with recurrent gastrointestinal perforations or anastomotic leakages.

INTERVENTIONS

Prophylaxis with intravenous fluconazole (400 mg per day) or placebo continued until resolution of the underlying surgical condition.

MEASUREMENTS AND MAIN RESULTS

Patients were evaluated daily, and specimens for culture were obtained three times per week during prophylaxis. The primary study end points were the frequency of and the time to intra-abdominal Candida infections. Secondary end points were the frequency of candidiasis (intra-abdominal and extra-abdominal) and the emergence or persistence of Candida colonization. Among patients who were not colonized at study entry, Candida was isolated from surveillance cultures during prophylaxis in 15% of the patients in the fluconazole group and in 62% of the patients in the placebo group (relative risk, 0.25; 95% confidence interval, 0.07 to 0.96; p = .04). Candida peritonitis occurred in one of 23 patients (4%) who received fluconazole and in seven of 20 patients (35%) who received placebo (relative risk, 0.12; 95% confidence interval, 0.02 to 0.93; p = .02). In addition, one catheter-related Candida albicans sepsis occurred in a fluconazole-treated patient. Thus, overall, candidiasis developed in two fluconazole patients and seven placebo patients (relative risk, 0.25; 95% confidence interval, 0.06 to 1.06; p = .06). C. albicans accounted for 87% of the Candida species isolated before or during prophylaxis, and all C. albicans strains were susceptible to fluconazole. Fluconazole was well tolerated, and adverse events occurred at similar frequencies in both treatment groups.

CONCLUSIONS

Fluconazole prophylaxis prevents colonization and invasive intra-abdominal Candida infections in high-risk surgical patients.

Rapid identification of fungi by using the ITS2 genetic region and an automated fluorescent capillary electrophoresis system

Invasive fungal disease often plays an important role in the morbidity and mortality of immunocompromised patients. The poor sensitivity of current fungal blood culture and histological practices has led to the development of highly sensitive and specific molecular techniques, such as the PCR. Sequence variability of the internal transcribed spacer 2 (ITS2) region of fungi is potentially useful in rapid and accurate diagnosis of clinical fungal isolates. PCR with fungus-specific primers targeted toward conserved sequences of the 5.8S and 28S ribosomal DNA (rDNA) results in amplification of the species-specific ITS2 regions, which are variable in amplicon length. We have made use of the ABI PRISM 310 genetic analyzer and the ABI PRISM 310 GeneScan analysis software for the determination of variable size differences of the ITS2 region of clinically important fungi, including Candida and non-Candida yeasts, Aspergillus species, and a variety of dermatophytes. No cross-reaction occurred when samples were tested against human and bacterial genomic DNA. We have found that most clinically significant fungal isolates can be differentiated by this method, and it therefore serves to be a promising tool for the rapid (<7 h) diagnosis of fungemia and other invasive fungal infections.

Survey of blood stream infections attributable to gram-positive cocci: frequency of occurrence and antimicrobial susceptibility of isolates collected in 1997 in the United States, Canada, and Latin America from the SENTRY Antimicrobial Surveillance Program. SENTRY Participants Group

The SENTRY Antimicrobial Surveillance Program was established in January, 1997 to monitor the predominant pathogens and antimicrobial resistance patterns of nosocomial and community-acquired infections via a network of sentinel hospitals in the United States (30 sites), Canada (eight sites), Latin America (10 sites), and Europe (24 sites). During the first 12-month study period (January to December, 1997), a total of 9519 blood stream infections (BSI) were reported by SENTRY participants in the U.S. (6150), Canada (1727), and Latin America (1642). The Gram-positive cocci, Staphylococcus aureus, coagulase-negative staphylococci (CoNS), enterococci, and streptococci accounted for 53.9% (5131 infections) of all BSI (56.5% U.S., 55.7% Canada, and 42.9% Latin America). The staphylococci, Enterococcus spp., S. pneumoniae, beta-hemolytic streptococci, and viridans group streptococci accounted for 6 of the top 11 BSI pathogens in the U.S. and Canada, whereas only S. aureus (1st), CoNS (3rd), and Enterococcus spp. (9th) were among the top 11 pathogens in Latin American hospitals. The results of this survey affirm the importance of Gram-positive cocci as causes of BSI in both North America and Latin America and demonstrate that important antimicrobial resistance exists among isolates of staphylococci, streptococci, and enterococci from all three geographic regions. This includes oxacillin-resistance among S. aureus (26.9% U.S., 29.2% Latin America, and 4.0% Canada) and CoNS (71.5% U.S., 68.4% Latin America, and 65.6% Canada), penicillin resistance among viridans group streptococci (48.5% U.S., 45.1% Canada, and 33.3% Latin America) and pneumococci (36.1% U.S., 27.5% Canada, and 65.6% Latin America), high-level resistance (HLR) to aminoglycosides among enterococci (27.2 to 70.1% U.S., 33.3 to 75.7% Canada and 16.7 to 51.5% Latin America), and macrolide resistance among beta-hemolytic streptococci (12.4 to 14.2% U.S., 10.5 to 12.3% Canada, and 0.0 to 4.0% Latin America), viridans group streptococci (32.4 to 39.7% U.S., 22.5-35.2% Canada, and 20.0% Latin America), and pneumococci (10.0 to 10.6% U.S., 9.8-10.8% Canada, and 9.4-18.7% Latin America). BSI isolates of Gram-positive cocci from the U.S. and Latin America were considerably more resistant than those from Canada. New agents with Gram-positive activity will be essential for optimal treatment of BSI attributable to Gram-positive cocci in both North and Latin America.

Lipid-based amphotericin B for the treatment of fungal infections

The frequency of life-threatening fungal infections has increased dramatically over the past few decades. For more than 30 years amphotericin B has been the standard treatment for systemic and deep-seated fungal infections, primarily because of its broad spectrum of activity. Its usefulness is limited by a relatively high frequency of significant adverse events including infusion-related reactions and nephrotoxicity. In an effort to overcome these side effects, a number of lipid-based formulations were developed, each with its own composition and pharmacokinetic behavior. The clinical significance of these differences is unknown. Available clinical data suggest the formulations have a reduced propensity for causing nephrotoxicity. However, considering limited efficacy data, they should be reserved as second-line therapy for patients who cannot tolerate or fail an adequate trial of conventional amphotericin B or cannot benefit from other antifungal agents.

Nosocomial bloodstream infections in HIV-infected patients: attributable mortality and extension of hospital stay

A 3-year prospective matched case-control study was performed to investigate the potential risk factors, prognostic indicators, extension of hospital stay, and attributable mortality of nosocomial bloodstream infections in HIV-infected patients. Matching variables were: age, gender, number of circulating CD4+ T lymphocytes, cause of hospital admission, hospitalization in the same ward within the 6 weeks of diagnosis of the case, and length of stay before the day of infection in the case. Eighty-four cases and 168 matched controls were studied. Nosocomial bloodstream infections complicated about 3 of 1000 hospital days per patient in the study period. With step-wise logistic regression analysis, the most important predictors for developing nosocomial bloodstream infections were: increasing value of Acute Physiology and Chronic Health Evaluation (APACHE II) score (p = .001) and use of central venous catheter (CVC) (p = .002). The excess of hospital stay attributable to nosocomial bloodstream infections was 17 days. The crude mortality rate was 43%. The attributable mortality rate was estimated to be 27% (95% confidence interval [CI] = 13%-48%). The estimated risk ratio for death was 3.91 (95% CI = 2.06-7.44). Multivariate analysis identified two prognostic indicators that were significantly associated with unfavorable outcome of bloodstream infections: number of circulating CD4+ T cells <100/mm3 (p = .002) and APACHE II score >15 (p = .01). Nosocomial bloodstream infections are more common in patients with advanced HIV disease. Important cofactors are high APACHE II score and use of CVC. These infections can cause an excess mortality and significantly prolong the hospital stay of HIV-infected patients.

Therapy of Candida infections: susceptibility testing, resistance, and therapeutic options

OBJECTIVE

Review the epidemiology of fungal infections, approved susceptibility testing methods, the scope of antifungal resistance, and advances in the treatment of fungal infections.

DATA SOURCES

MEDLINE databases (from 1966 to March 1998) were searched for literature pertaining to the epidemiology and management of fungal infections.

STUDY SELECTION AND DATA EXTRACTION

Articles were selected to assist in providing the reader an understanding of the epidemiology and management of fungal infections.

DATA SYNTHESIS

Fungi have emerged as an important class of pathogens. Even though fungi rank as the fourth most commonly encountered nosocomial bloodstream pathogen, and are associated with the highest mortality of commonly encountered pathogens, only within the past year have methods for conducting and guidelines for interpreting in vitro susceptibility tests been approved. Under the guidance of these standards, we have begun to understand important issues regarding fungi such as the scope and mechanisms of antifungal resistance. Although there has not been a significant addition to our antifungal armamentarium since 1992, advances in antifungal therapy have been realized with the reformulation of available agents and the delineation of the pharmacodynamic characteristics of several antifungals. Additionally, several new agents, including a new class of antifungals, probably will enter into clinical use within the next 5 years.

CONCLUSIONS

We have entered an era in which our understanding of fungi is increasing tremendously. Clinicians need to familiarize themselves with the current concepts surrounding the management of fungal infections in order to provide optimal care for their patients.

Bacterial pathogens isolated from patients with bloodstream infection: frequencies of occurrence and antimicrobial susceptibility patterns from the SENTRY antimicrobial surveillance program (United States and Canada, 1997)

The SENTRY Program was established in January 1997 to measure the predominant pathogens and antimicrobial resistance patterns of nosocomial and community-acquired infections over a broad network of sentinel hospitals in the United States (30 sites), Canada (8 sites), South America (10 sites), and Europe (24 sites). During the first 6-month study period (January to June 1997), a total of 5,058 bloodstream infections (BSI) were reported by North American SENTRY participants (4,119 from the United States and 939 from Canada). In both the United States and Canada, Staphylococcus aureus and Escherichia coli were the most common BSI isolates, followed by coagulase-negative staphylococci and enterococci. Klebsiella spp., Enterobacter spp., Pseudomonas aeruginosa, Streptococcus pneumoniae, and beta-hemolytic streptococci were also among the 10 most frequently reported species in both the United States and Canada. Although the rank orders of pathogens in the United States and Canada were similar, distinct differences were noted in the antimicrobial susceptibilities of several pathogens. Overall, U.S. isolates were considerably more resistant than those from Canada. The differences in the proportions of oxacillin-resistant S. aureus isolates (26.2 versus 2.7% for U.S. and Canadian isolates, respectively), vancomycin-resistant enterococcal isolates (17.7 versus 0% for U.S. and Canadian isolates, respectively), and ceftazidime-resistant Enterobacter sp. isolates (30.6 versus 6.2% for U.S. and Canadian isolates, respectively) dramatically emphasize the relative lack of specific antimicrobial resistance genes (mecA, vanA, and vanB) in the Canadian microbial population. Among U.S. isolates, resistance to oxacillin among staphylococci, to vancomycin among enterococci, to penicillin among pneumococci, and to ceftazidime among Enterobacter spp. was observed in both nosocomial and community-acquired pathogens, although in almost every instance the proportion of resistant strains was higher among nosocomial isolates. Antimicrobial resistance continues to increase, and ongoing surveillance of microbial pathogens and resistance profiles is essential on national and international scales.

National surveillance of nosocomial blood stream infection due to Candida albicans: frequency of occurrence and antifungal susceptibility in the SCOPE Program

Surveillance of nosocomial blood stream infections (BSI) in the USA between April 1995 and June 1996 revealed that Candida was the fourth leading cause of nosocomial BSI, accounting for 8% of all infections. Fifty-two percent of 379 episodes of candidemia were due to Candida albicans. In vitro susceptibility studies using the 1997 National Committee for Clinical Laboratory Standards reference method demonstrated that 92% of C. albicans isolates were susceptible to 5-fluorocytosine and 90% were susceptible to fluconazole and itraconazole. Geographic variation in susceptibility of fluconazole and itraconazole was observed. Isolates from the Northwest and Southeast regions were more frequently resistant to fluconazole (13.3-15.5%) and to itraconazole (17.2-20.0%) than those from the Northeast and Southwest regions (2.9-5.5% resistant to fluconazole and itraconazole). Continued surveillance for infections caused by C. albicans and other species of Candida among hospitalized patients is recommended.

Thirteen-year evolution of azole resistance in yeast isolates and prevalence of resistant strains carried by cancer patients at a large medical center

Drug resistance is emerging in many important microbial pathogens, including Candida albicans. We performed fungal susceptibility tests with archived isolates obtained from 1984 through 1993 and fresh clinical isolates obtained from 1994 through 1997 by testing their susceptibilities to fluconazole, ketoconazole, and miconazole and compared the results to the rate of fluconazole use. All isolates recovered prior to 1993 were susceptible to fluconazole. Within 3 years of widespread azole use, we detected resistance to all agents in this class. In order to assess the current prevalence of resistant isolates in our hematologic malignancy and transplant patients, we obtained rectal swabs from hospitalized, non-AIDS, immunocompromised patients between June 1995 and January 1996. The swabs were inoculated onto sheep's blood agar plates containing 10 microg of vancomycin and 20 microg of gentamicin/ml of agar. One hundred one yeasts were recovered from 97 patients and were tested for their susceptibilities to amphotericin B, fluconazole, flucytosine, ketoconazole, and miconazole. The susceptibility pattern was then compared to those for all clinical isolates obtained throughout the medical center. The antifungal drug histories for each patient were also assessed. The yeasts from this surveillance study were at least as susceptible as the overall hospital strains. There did not appear to be a direct linkage between prior receipt of antifungal agent therapy and carriage of a new, drug-resistant isolate. Increased resistance to newer antifungal agents has occurred at our medical center, but it is not focal to any high-risk patient population that we studied. Monitoring of susceptibility to antifungal agents appears to be necessary for optimizing clinical therapeutic decision making.

Controlled clinical laboratory comparison of two supplemented aerobic and anaerobic media used in automated blood culture systems to detect bloodstream infections

A 20-ml blood sample was collected from adult patients with suspected bloodstream infections and distributed equally into the four volume-controlled bottles of a blood culture set consisting of aerobic and anaerobic BACTEC Plus/F bottles and aerobic and anaerobic BacT/Alert FAN bottles. All bottles were incubated in their respective instruments for a standard 5-day protocol or until the instruments signalled positivity. Samples in all bottles with negative results by these instruments were terminally subcultured. A total of 8,390 blood culture sets were obtained during the study period, of which 4,402 (52.5%) met the study criteria. Of these, 946 (21.5%) were positive either by instrument signal or by additional terminal subculture of all negative bottles and yielded growth of microorganisms. Five hundred eighty-nine (13.4%) blood culture sets were considered to have recovered 663 clinically significant organisms. When both the BACTEC and the BacT/Alert systems were used, 465 positive sets were detected; BACTEC alone detected 52 positive sets and BacT/Alert alone detected 72 (P = 0.09). No differences were found between the two systems in microbial recovery rate from blood cultures obtained from patients on antibiotic therapy. Significantly more members of the family Enterobacteriaceae (P < 0.01) were detected from patients without antimicrobial therapy by BacT/Alert than by BACTEC. The false-negative rates were 0.20% for BACTEC and 0.32% for BacT/Alert. A significantly higher false-positive rate was found for BACTEC (P < 0.0001). Both systems were comparable for the time to detection of microorganisms. However, gram-positive bacteria were detected faster by BACTEC and Enterobacteriaceae were detected faster on average by BacT/Alert. We concluded that both systems are comparable in their abilities to recover aerobic and anaerobic organisms from blood cultures and a terminal subculture might not be necessary for either of the two systems. The increased positivity rate when using an anaerobic bottle in a two-bottle blood culture set is due to the additional blood volume rather than to the use of an anaerobic medium.