Nosocomial bloodstream infections: secular trends in a statewide surveillance program in Virginia

Implantable Device-Related Infection

Over half of the nearly two million healthcare-associated infections can be attributed to indwelling medical devices. In this review, we highlight the difficulty in diagnosing implantable device-related infection and how this leads to a likely underestimate of the prevalence. We then provide a length-scale conceptualization of device-related infection pathogenesis. Within this conceptualization we focus specifically on biofilm formation and the role of host immune and coagulation systems. Using this framework, we describe how current and developing preventative strategies target specific processes along the entire length-scale. In light of the significant time horizon for the development and translation of new preventative technologies, we also emphasize the need for parallel development of in situ treatment strategies. Specific examples of both preventative and treatment strategies and how they align with the length-scale conceptualization are described.

Nosocomial Outbreak of Systemic Candidosis Associated With Parenteral Nutrition

Eight patients in two surgical units developed systemic candidosis during a 40-day period from June 5 to July 13, 1987 (in five cases Candida albicans was identified). Three of them died. All cases belonged to a group of 27 patients receiving parenteral nutrition (PN), while among the 108 patients who did not receive PN, no cases were observed (p = .000001). Candida was cultured from two PN bags administered to the cases. A specialized nutrition nurse was responsible for the PN compounding and for maintaining administration sets in the two wards involved.

An epidemiological investigation in which 19 uninfected patients who had had PN were used as controls, showed no significant difference between cases and controls except that lipids were more frequently added to bags administered to cases (p = .0005). Furthermore, the bags administered to cases contained a higher average number of multidose constituents (p = .0008) when the comparison was focused on the two days before the onset of symptoms.Given the favorable medium provided by lipids, even a low level contamination of PN solutions during compounding and/or administration could have been responsible for the outbreak. The finding of a more frequent exposure of cases to multidose vials suggests, although not conclusively, that an extrinsic contamination occurred during compounding. Six isolates of C albicans were available from four cases. C albicans was cultured from the pharyngeal swabs of two physicians and three nurses, including the specialized nutrition nurse. According to DNA restriction pattern analysis, a single strain was responsible for all the cases of systemic candidosis, with only the specialized nutrition nurse harboring the same strain. DNA fingerprinting provided a reliable system for typing C albicans strains. This was the first outbreak of C albicans systemic infection associated with PN.

Guideline for Prevention of Intravascular-Device–Related Infections

The “Guideline for Prevention of Intravascular Device-Related Infections” is designed to reduce the incidence of intravascular device-related infections by providing an over view of the evidence for recommendations considered prudent by consensus of Hospital Infection Control Practices Advisor y Committee (HICPAC) members. This two-part document updates and replaces the previously published Centers for Disease Control's (CDC) Guideline for Intravascular Infections (Am J Infect Control1983;11:183-199). Part I, “Intravascular Device-Related Infections: An Over view” discusses many of the issues and controversies in intravascular-device use and maintenance. These issues include definitions and diagnosis of catheter-related infection, appropriate barrier precautions during catheter insertion, inter vals for replacement of catheters, intravenous (IV) fluids and administration sets, catheter-site care, the role of specialized IV personnel, and the use of prophylactic antimi-crobials, flush solutions, and anticoagulants. Part II, “Recommendations for Prevention of Intravascular Device-Related Infections” provides consensus recommendations of the HICPAC for the prevention and control of intravascular device-related infections. A working draft of this document also was reviewed by experts in hospital infection control, internal medicine, pediatrics, and intravenous therapy. However, all recommendations contained in the guideline may not reflect the opinion of all reviewers.

Epidemiology of bacteraemia in Hamad general hospital, Qatar: a one year hospital-based study

We conducted a one-year observational study from July 2007 to June 2008 to describe the epidemiology of bacteraemia at Hamad general hospital. During this period, a total of 452 episodes of bacteraemia occurred, which corresponds to a rate of 19/1000 hospital admissions. Most patients 58.8% (266/452) had community acquired bacteraemia, and primary bacteraemia accounted for 62.2% (281/452) of the cases. The most common source of bacteraemia was intravenous catheterization in 19.2% (87/452) but no source was identified in 42.9% (194/452) of the episodes. Gram-negative organisms were isolated in 63.1% (285/452) episodes with Escherichia coli being the most frequent 21.5% (97/452). Multidrug resistance was observed in 33.3% (7/21) of all Pseudomonas aeruginosa isolates, 50% (6/12) of Acinetobacter isolates and 28.6% (6/21) of Enterobacter isolates, whereas all ESBL producing Klebsiella spp. and E. coli were multiresistant. The percentages of oxacillin resistant coagulase negative Staphylococci isolates and methicillin-resistant Staphylococcus aureus isolates were 81.8% (27/33) and 13.2% (7/53) respectively. In hospital mortality was 22.5% (102/452), and inadequate treatment and septic shock were found to be independent predictors of mortality. Therefore, bloodstream infection surveillance is crucial to produce meaningful guidelines for prevention (e.g., catheter-related) and empirical treatment of bacteraemia in Qatar.

Long term trends in the occurrence of nosocomial blood stream infection

OBJECTIVE

To determine trends in the occurrence of nosocomial blood stream infection at the University of Alberta Hospital.

METHODS

A prospective survey of nosocomial blood stream infection was conducted; cases from August 1986 to December 1996 were reviewed. Cases were detected by a review of positive blood cultures reported by the microbiology laboratory. Centers for Disease Control and Prevention definitions of nosocomial infection were used to categorize isolates as nosocomial, community acquired or contaminant.

RESULTS

There were 2389 cases; primary bacteremia was the most common source (57%), followed by urinary tract, respiratory tract and surgical site sources (10% each). The nosocomial blood steam infection rate rose progressively from 6.0/1000 admissions and 4.59/10,000 patient days in 1986 to 11.2/1000 admissions and 14.31/10,000 days in 1996 (P<0.01); 48% of the total increase in rate occurred between 1995 and 1996. Significant increases occurred between 1986 and 1996 in primary infections (from 3.2 to 7.5/1000 admissions, P<0.01) and infections from all secondary sources (from 2.5 to 3.8/1000 admissions, P=0.01). Coagulase-negative staphylococci (27%), Staphylococcus aureus (19%) and enterococci (9%) were the most common microbial causes. Aerobic Gram-negative bacilli accounted for 28% and candida for 6%. Coagulase-negative staphylococci, enterococci and candida all became more prevalent as causes of infection over the study period.

CONCLUSIONS

The nosocomial blood stream infection rate in the hospital has nearly doubled in the past 10 years, largely due to increased primary bacteremia.

Salvage Therapy of Refractory Chronic Disseminated Candidiasis in a Patient with Acute Myeloid Leukaemia and Secondary Prophylaxis During Allogeneic Stem Cell Transplantation

We report on the treatment course of a 27-year-old male patient with acute myeloid leukaemia M1 and chronic disseminated candidiasis. After induction chemotherapy, the patient developed oesophageal candidiasis while participating in a voriconazole vs. placebo prophylaxis trial. He was then switched to oral fluconazole 400 mg q.i.d. After 6 days of futile fluconazole therapy he was switched to caspofungin 50 mg q.i.d. Caspofungin dose was later increased to 100 mg q.i.d after disseminated candidiasis with involvement of lung, spleen and liver was diagnosed. Following 63 days of caspofungin without resolution of symptoms, i.e. being persistently febrile, and emergence of soft tissue Candida abscesses, he was included into a trial allowing compassionate use of posaconazole as salvage therapy for refractory invasive fungal infections. Symptoms rapidly resolved under posaconazole 200 mg q.i.d. treatment and the patient was able to undergo allogeneic haematopoietic stem cell transplantation on secondary prophylaxis with posaconazole.

Diagnosis and treatment of Candida vertebral osteomyelitis: Clinical experience with a short course therapy of amphotericin B lipid complex

BACKGROUND

Musculoskeletal candidiasis occurs in some patients with candidemia resulting from organ infection, IV drug use, or indwelling central venous catheters. Diagnosis is often difficult because of vague symptomatology and a frequent afebrile course.

CASE DESCRIPTION

Three patients with Candida vertebral osteomyelitis are presented. All followed the use of indwelling central venous access catheters and antimicrobial therapy between 6 months and 3 years earlier. In 2, fungemia with the same Candida spp. preceded the spondylodiskitis. These 3 patients bring to nearly 75 the number of reported individuals with what was once quite rare. Although IV amphotericin B doxycholate and fluconazole have usually been effective therapy over prolonged periods of time, we used liposomal amphotericin B to treat 2 of our 3 patients. Both received 5 mg/kg daily for 18-42 days that resulted in total disappearance of signs and symptoms.

CONCLUSION

This relatively brief duration of therapy reduces treatment time and is cost-effective.

Trends in the epidemiology of Candida bloodstream infections in Northern Ireland between January 1984 and December 2000

OBJECTIVE

To describe the epidemiology of Candida bloodstream infections (BSI) in Northern Ireland.

METHODS

Retrospective collation of data relating to all clinically significant BSI in a university teaching hospital, which had been recorded prospectively, between 1984 and 2000.

RESULTS

One hundred and forty five episodes of candidaemia occurred in 144 patients (of mean age 56.6 years). The contribution of Candida spp. towards all significant BSI increased from 2.0% to 2.5%. C. albicans was the most frequently isolated species, however, its incidence fell from 70% to 53% during the study period. The greatest increase in incidence was seen with C. glabrata which was the most common non-albicans species. Twenty-nine per cent of isolates occurred in patients from an intensive care unit and, surprisingly, a further 25.5% occurred in patients from a surgical service.

CONCLUSION

There appears to be several subtle differences in the epidemiology of candidal BSI between Northern Ireland and other countries.

Problems and solutions in hospital-acquired bacteraemia

Despite infection control efforts, bacteraemia remains one of the most frequent and challenging hospital-acquired infections and is associated with high attributable morbidity and mortality and additional use of healthcare resources. Prevention and control of hospital-acquired blood-stream infection requires improved detection methods, better definition of patient populations at risk, more refined guidelines for the interpretation of positive blood cultures and a better discrimination between sporadic contaminants and true bacteraemia. These issues are addressed in the current review together with those related to the diagnosis, management and recent advances in the prevention of cathether-related bacteraemia, the leading cause of hospital-acquired blood-stream infection. Finally, the reasons and perspectives for blood-stream infection surveillance are briefly discussed.

Rapid, sensitive and simple detection of candida deep mycosis by amplification of 18S ribosomal RNA gene; comparison with assay of serum beta-D-glucan level in clinical samples

We evaluated the clinical usefulness of a polymerase chain reaction (PCR) assay amplifying the 18S ribosomal RNA gene of fungi for the diagnosis of deep candidiasis, compared with that of the beta-glucan test or Cand-Tec test. Thirty critically ill patients who had received prolonged care with intravenous hyperalimentation and endotracheal intubation in the intensive care unit and were suspected of having deep fungal infections were examined. Twenty-one were fungi positive in the PCR assay (70%). Among 24 samples in which the PCR assay, beta-glucan test and Cand-Tec test were performed simultaneously, 75% of the samples (18/24) were fungi positive in the PCR assay, whereas only 54% (13/24) had positive reactions in the beta-glucan test and 21% (5/24) in the Cand-Tec test. The results of the Cand-Tec test showed no relationship with those of the PCR or beta-glucan test. The lower limit of detection in the PCR assay was 4-5 CFU/ml of C. albicans in blood. No fungal organism was amplified from the serum of 20 healthy individuals. The results of the PCR assay and beta-glucan test showed a significant correlation in this study, but the PCR assay proved to be more sensitive than the beta-glucan test (p < 0.05), and to be more useful for the clinical diagnosis and monitoring of deep Candidiasis.

Detection and identification of fungal pathogens in blood by using molecular probes

A PCR assay was developed for the detection and identification of Candida and Aspergillus species. The design of the oligonucleotide primer pair as well as the species-specific probes used for species identification was derived from a comparison of the sequences of the 18S rRNA genes of various fungal pathogens. The primers targeted a consensus sequence for a variety of fungal pathogens. The assay was tested for sensitivity and specificity with 134 fungal and 85 nonfungal isolates. To assess clinical applicability, 601 blood samples from four defined groups were tested: group A (n = 35), controls; groups B to D (n = 86), patients with febrile neutropenia, without fungal colonization (group B; n = 29) and with fungal colonization (group C; n = 36); and patients with documented invasive fungal infection (IFI) (group D; n = 21). The assay detected and, by species-specific hybridization, identified most of the clinically relevant Candida and Aspergillus species at 1 CFU/ml of blood. Amplification was 100% sensitive for all molds and yeasts tested, with Histoplasma capsulatum being the only non-Aspergillus species hybridizing with the Aspergillus spp. probe. None of 35 group A patients and only 3 of 65 group B and C patients were PCR positive. The sensitivity of the assay for specimens from patients with IFI (21 patients in group D) was 100% if two specimens were tested. For specificity, 3 of 189 specimens from patients at risk but with negative cultures were positive by the assay, for a specificity of 98%. PCR preceded radiological signs by a median of 4 days (range, 4 to 7 days) for 12 of 17 patients with hepatosplenic candidiasis or pulmonary aspergillosis. For the 10 patients with IFI responding to antifungal therapy, PCR assays became persistently negative after 14 days of treatment, in contrast to the case for 11 patients, who remained PCR positive while not responding to antifungal therapy. Thus, the described PCR assay allows for the highly sensitive and specific detection and identification of fungal pathogens in vitro and in vivo. Preliminary data from the screening of a selected group of patients revealed some value in the early diagnosis and monitoring of antifungal therapy.

Nosocomial Candida. Epidemiology, transmission, and prevention

The NNIS and the newly established SCOPE data indicate that the relative proportion of organisms causing nosocomial bloodstream infections has changed over the last decade, with Candida species now being firmly established as one of the most frequent agents. The epidemiology of nosocomial candidemia is continually being refined, but established predisposing factors including immunosuppression and malignancies, use of broad spectrum antibiotics, and use of indwelling central catheters remain as significant risk factors. The high cost of health care and greater attention to continuous quality improvement will stimulate better and more effective ways of diagnosing and treating candida infections using combined clinical and microbiologic acumen. There is room for optimism as newer antifungal agents with reduced toxicities have impact on therapy of candidal infections. Aggressive development of still more agents and reformulations of older agents continue in earnest. Even greater consolation comes from the increased awareness of lay and medical personnel alike regarding the appropriate and judicious use of antimicrobial agents.

Enterococcus faecium in hospitals

Most of the characteristics that have ensured the success of enterococci as nosocomial pathogens were described early in this century. Enterococcus faecium and Enterococcus faecalis, the enterococci most frequently isolated from clinical material, differ fundamentally. The intrinsic antimicrobial resistance of Enterococcus faecium, supplemented by acquired resistance mechanisms, can generate a glycopeptide-multiply-resistant nosocomial pathogen that survives on hands and in the environment, and has the potential for intra-hospital and inter-hospital spread. The use of terms such as 'an enterococcus', 'faecal streptococci' and 'group D streptococci' have hindered, and still hinder, our understanding of a species rapidly emerging as the most problematic of nosocomial pathogens.

New and emerging yeast pathogens

The most common yeast species that act as agents of human disease are Candida albicans, Candida tropicalis, Candida glabrata, Candida parapsilosis, and Cryptococcus neoformans. The incidence of infections by other yeasts has increased during the past decade. The most evident emerging pathogens are Malassezia furfur, Trichosporon beigelii, Rhodotorula species, Hansenula anomala, Candida lusitaniae, and Candida krusei. Organisms once considered environmental contaminants or only industrially important, such as Candida utilis and Candida lipolytica, have now been implicated as agents of fungemia, onychomycosis, and systemic disease. The unusual yeasts primarily infect immunocompromised patients, newborns, and the elderly. The role of central venous catheter removal and antifungal therapy in patient management is controversial. The antibiograms of the unusual yeasts range from resistant to the most recent azoles and amphotericin B to highly susceptible to all antifungal agents. Current routine methods for yeast identification may be insufficient to identify the unusual yeasts within 2 days after isolation. The recognition of unusual yeasts as agents of sometimes life-threatening infection and their unpredictable antifungal susceptibilities increase the burden on the clinical mycology laboratory to pursue complete species identification and MIC determinations. Given the current and evolving medical practices for management of seriously ill patients, further evaluations of the clinically important data about these yeasts are needed.

Candida colonization and subsequent infections in critically ill surgical patients

OBJECTIVE

The authors determined the role of Candida colonization in the development of subsequent infection in critically ill patients.

DESIGN

A 6-month prospective cohort study was given to patients admitted to the surgical and neonatal intensive care units in a 1600-bed university medical center.

METHODS

Patients having predetermined criteria for significant Candida colonization revealed by routine microbiologic surveillance cultures at different body sites were eligible for the study. Risk factors for Candida infection were recorded. A Candida colonization index was determined daily as the ratio of the number of distinct body sites (dbs) colonized with identical strains over the total number of dbs tested; a mean of 5.3 dbs per patient was obtained. All isolates (n = 322) sequentially recovered were characterized by genotyping using contour-clamped homogeneous electrical field gel electrophoresis that allowed strain delineation among Candida species.

RESULTS

Twenty-nine patients met the criteria for inclusion; all were at high risk for Candida infection; 11 patients (38%) developed severe infections (8 candidemia); the remaining 18 patients were heavily colonized, but never required intravenous antifungal therapy. Among the potential risk factors for candida infection, three discriminated the colonized from the infected patients--i.e., length of previous antibiotic therapy (p < 0.02), severity of illness assessed by APACHE II score (p < 0.01), and the intensity of Candida spp colonization (p < 0.01). By logistic regression analysis, the latter two who were the independent factors that predicted subsequent candidal infection. Candida colonization always preceded infection with genotypically identical Candida spp strain. The proposed colonization indexes reached threshold values a mean of 6 days before Candida infection and demonstrated high positive predictive values (66 to 100%).

CONCLUSIONS

The intensity of Candida colonization assessed by systematic screening helps predicting subsequent infections with identical strains in critically ill patients. Accurately identifying high-risk patients with Candida colonization offers opportunity for intervention strategies.

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

In order to determine the potential for cross-transmission of Candida spp. between health-care workers and patients, the survival of clinical isolates of five species of Candida on the palms of human volunteers was tested. One hundred microliters of a McFarland 1.0 density suspension (5 x 10(5) cfu) from an overnight culture of Candida albicans, Candida krusei, Candida parapsilosis, Candida tropicalis and Candida glabrata was used as inoculum. The degree of hydrophobicity of the different Candida species was also tested and did not influence the survival. The half-lives were brief, being 9.5, 12.4, 7.4, 12.8, 9.6 min for Candida albicans, Candida krusei, Candida glabrata, Candida parapsilosis, and Candida tropicalis, respectively, but at 45 min 2.6 x 10(3) to 3 x 10(4) organisms remained on the hands. Survival of Candida albicans for as long as 24 h on inanimate surfaces was observed. Transmission from one hand to a second hand occurred in 69% of the experiments and from the first to a third hand in 38%. Transmission to and from inanimate surfaces was successful in most of the experiments (90%). This experimental model aids in the biological study of Candida spp. and suggests some of the potential mechanisms of transmission.

Investigation of the sequence of colonization and candidemia in nonneutropenic patients

Among neutropenic patients with hematologic malignancies, candidemia has been shown to arise typically from autoinfection after colonization. In patients without neutropenia, we examined the similarities of strains colonizing or infecting various body sites and those subsequently causing Candida bloodstream infections. Strain similarity was examined by karyotyping and restriction endonuclease analysis of genomic DNA (REAG) by using two restriction enzymes (SfiI and BssHII). The banding patterns of 42 isolates from 19 patients were independently evaluated in a blinded fashion by three observers. The interobserver reliability measured with a generalized kappa statistic was 0.59 for karyotyping, 0.84 for REAG with SfiI, and 0.88 for REAG with BssHII (P < 0.001 for each). REAG classified the initial colonizing or infecting isolate and subsequent blood isolates as identical in 16 patients (84%). The mean duration of colonization or infection prior to a positive blood culture was 5 and 23 days in patients infected with related and unrelated isolates, respectively (P = 0.14; 95% confidence interval = -14.5 to 50.5). Karyotyping results matched the REAG results for isolates from 14 of the 19 patients (74%). In patients infected with identical isolates, the initial isolate was most frequently recovered from the urine (n = 5) or vascular catheter tips (n = 4). In the five subjects with organisms showing disparate results between the methods, karyotyping revealed different banding patterns, whereas REAG suggested that the isolates were identical. Candida colonization or infection with an identical strain frequently precedes bloodstream infection in nonneutropenic patients. Future studies should evaluate whether patients at high risk for candidemia and who have vascular catheter or urine samples that are positive for a Candida on culture should be treated empirically.

Effect of polyurethane catheters and bacterial biofilms on the in-vitro activity of antimicrobials against Staphylococcus epidermidis

The effect of two polyurethane ['Cavafix Certo' (CAV); 'Viacath' (VIA)] catheters on the in-vitro activity of amikacin (AN), clindamycin (CM), cloxacillin (CX), ciprofloxacin (CIP), vancomycin (VA), teicoplanin (TEI) and daptomycin (DAP) against slime producing and non-producing Staphylococcus epidermidis strains was determined using a microdilution assay. None of the antimicrobial agents was significantly affected in the presence of the catheters. The susceptibility of S. epidermidis attached to CAV and VIA catheters was also evaluated. Minimum inhibitory concentration (MIC) values were similar when planktonic and attached bacteria were compared. Minimum bactericidal concentrations (MBCs) markedly increased in the presence of 6 and 48 h bacterial biofilms. These increases in MBC values occurred when either slime producing or non-producing strains were used, and in most cases were higher for CAV catheters than for VIA catheters. This phenomenon was shown not to be due to differences in bacterial adherence. It is concluded that the in-vitro bactericidal activity of certain antimicrobials markedly decreased when bacteria adhered to plastic catheters, but this effect could have been dependent partially on the nature of the catheters.

Relative frequency of nosocomial pathogens at a university hospital during the decade 1980 to 1989

BACKGROUND

We compared the relative frequency of pathogens isolated from 1985 to 1989 (N = 4358) with those isolated from 1980 to 1984 (N = 5290) in a university hospital to determine trends in the relative importance of pathogens causing nosocomial infection.

METHODS

Our study was based on surveillance data prospectively obtained between 1980 and 1989 from a 600-bed university hospital. Statistically significant trends occurring from 1980 to 1984 to 1985 to 1989 were determined by chi 2 tests with Bonferroni corrections (i.e., p less than [0.05/17]).

RESULTS

Overall an increased frequency of isolation occurred for Candida and other yeasts and for Haemophilus species. A decreased frequency was noted for Proteus species, non-Bacteroides anaerobes, and Serratia species. Comparison of 1985 to 1989 with 1980 to 1984 revealed that the most significant change in nosocomial pathogens was the marked increase in infections with yeast, principally Candida species. Candida and other yeast infections increased 40%, from 7.6% (rank, 5) to 10.6% (rank, 3) of all pathogens isolated. Increases, which occurred in urine, blood, and wound isolates, were especially marked among surgical patients. In addition, a significant increase was noted among blood isolates in the isolation of yeast other than Candida albicans.

CONCLUSIONS

We conclude that Candida and other yeasts are being isolated increasingly as causative agents of nosocomial infection.

Critical assessment of blood culture techniques: analysis of recovery of obligate and facultative anaerobes, strict aerobic bacteria, and fungi in aerobic and anaerobic blood culture bottles

Recent reports have documented a decrease in anaerobic bacteremias and have questioned the need for routine anaerobic blood cultures. At the same time, we and others have noted an increase in fungal bloodstream infections. In this two-part study, we first compared recoveries of obligate anaerobic bacteria with those of fungi over a 13-year period and then examined the recoveries of all bacteria and fungi in aerobic and anaerobic blood culture bottles during a 12-month period. During the 13-year period, the number of patients with anaerobic bacteremia remained relatively constant (average, 39 patients per year), while the incidence of fungemia steadily increased, from 12 patients in 1978 to 117 patients in 1990. Of the 1,090 anaerobic isolates, 55.1 and 90.2% were recovered in aerobic and anaerobic bottles, respectively, compared with 98.6 and 37.0% of the 2,582 fungi. During the 12-month period of evaluation, 2,980 bacteria and fungi were recovered in cultures collected from 1,555 patients. Overall, 21.1% more organisms were recovered in aerobic bottles than in anaerobic bottles, including significantly more Staphylococcus species; gram-positive aerobic bacilli; Escherichia, Enterobacter, Pseudomonas, Xanthomonas, and Acinetobacter species; miscellaneous gram-negative bacilli; and yeasts. Only anaerobic gram-negative bacilli and non-spore-forming gram-positive bacilli were isolated more commonly in anaerobic bottles. These data support the concepts that bacteremia caused by obligate anaerobic bacteria is decreasing relative to sepsis caused by other bacteria and fungi and that the routine use of unvented anaerobic blood culture bottles reduces the recovery of common aerobic bloodstream pathogens.

[Systemic candidiasis]

Candida proliferate within the body of patients with deficient cellular immunity either by the haematogenous route or by adjacency. This condition is often found in hospital patients. It explains the increasing incidence of disseminated candidiasis. They are preferentially found in patients who have had complicated surgery, mostly of the gastrointestinal tract and the heart, or transplant surgery (except for kidney transplants), or who have had prolonged intensive care. Other patients concerned are neonates with a low birth weight, haemato-oncology patients, heroin addicts and AIDS patients. Clinical signs are usually unspecific. When there is widespread involvement, clinical signs can be defined by the secondary locations, especially within the kidneys, lung, endocardium and brain in surgical patients, and liver and spleen in haemato-oncology patients. Eye, skin, gastrointestinal tract, and indeed, muscle lesions which are easily accessible, should be looked for routinely. This helps to ascertain the diagnosis, by showing the presence of Candida in the tissues. Moreover, isolating Candida from places which are normally sterile confirms deep-seated candidiasis. However, the presence of Candida in urine, bronchi, or drainage fluids is only the witness of saprophytism. This underlines the usefulness of immunological tests, which should soon benefit from the availability of new kits for the detection of cytoplasmic antigens. Indeed, the search for antibodies or circulating metabolites do not provide, at present, significantly different results in patients who have only been colonised and in those who have a systemic candidiasis. Interesting results are only obtained by showing the presence of mannans, in research laboratories. For treatment, amphotericin B remains the standard antifungal agent, and the association of amphotericin B with flucytosine the recommended association. However, drugs such as the new triazoles, among which fluconazole is particularly well tolerated and efficient, may considerably alter the principles of treatment. Finally, combining a fungal decontamination of the gut should help reduce the very high death rate of systemic candidiasis.

Secular trends in nosocomial primary bloodstream infections in the United States, 1980-1989. National Nosocomial Infections Surveillance System

More than 25,000 primary bloodstream infections (BSIs) were identified by 124 National Nosocomial Infections Surveillance System hospitals performing hospital-wide surveillance during the 10-year period 1980-1989. These hospitals reported 6,729 hospital-months of data, during which time approximately 9 million patients were discharged. BSI rates by hospital stratum (based on bed size and teaching affiliation) and pathogen groups were calculated. In 1989, the overall BSI rates for small (less than 200 beds) nonteaching, large nonteaching, small (less than 500 beds) teaching, and large teaching hospitals were 1.3, 2.5, 3.8, and 6.5 BSIs per 1,000 discharges, respectively. Over the period 1980-1989, significant increases (p less than 0.0001) were observed within each hospital stratum, in the overall BSI rate and the BSI rate due to each of the following pathogen groups: coagulase-negative staphylococci, Staphylococcus aureus, enterococci, and Candida species. In contrast, the BSI rate due to gram-negative bacilli remained stable over the decade, in all strata. Except for small nonteaching hospitals, the greatest increase in BSI rates was observed in coagulase-negative staphylococci (the percentage increase ranged between 424% and 754%), followed by Candida species (219-487%). In small nonteaching hospitals, the greatest increase was for S. aureus (283%), followed by enterococci (169%) and coagulase-negative staphylococci (161%). Our analysis documents the emergence over the last decade of coagulase-negative staphylococci as one of the most frequently occurring pathogens in BSI.

The continuing importance of staphylococci as major hospital pathogens

Rates of hospital-acquired staphylococcal infection have risen substantially in the United States over the last decade. Moreover, it has been shown that bloodstream infections caused by these organisms account for significant morbidity and mortality. It is likely that the changes in medical practice and in types of patient account for these changes, and current antibiotic therapy has helped select more resistant organisms. The increasing use of implantable and temporary medical devices and the increased use of immunosuppressive therapies correlate strongly with the rising incidence of these organisms. Likewise, more patients are predisposed to these infections because of poor immune status and factors favouring colonization. Intrinsic microbiological factors such as glycocalyx production and the presence of bacterial surface proteins allow these organisms to adhere to protein coated foreign bodies and basement membranes thus enabling them to initiate infection and cause disease. Moreover, virulence factors such as encapsulation, slime production and elaboration of extracellular enzymes aid their resistance to host defences. As a group, staphylococci are a leading cause of hospital-acquired infection, and species identification is required for both treatment and control.

Laboratory diagnosis of invasive candidiasis

Severe infections due to Candida species have become more frequent during the past two decades because of the increasing numbers of immunosuppressed patients being treated in our hospitals. Distinguishing colonization from invasive disease requires knowledge of the pathogenetic mechanisms leading to invasion. To assist the clinician in therapeutic decisions, clinical microbiologists should identify to species Candida organisms isolated from immunosuppressed patients. Quantitative or semiquantitative cultures of urine, burn tissues, intravascular catheter tips, and bronchoalveolar lavage specimens may provide useful information. Immunofluorescent staining of certain specimens can enhance diagnostic yield. The lysis-centrifugation blood culture technique offers some advantages over traditional broth techniques in detecting Candida fungemia. Antibody testing is of limited diagnostic value in highly immunosuppressed patients. Developing simple and reliable tests for detecting antigens or metabolites of Candida spp. in the sera of infected patients has proven difficult. Methods for typing Candida albicans are evolving. Typing should prove useful for studying the epidemiology of candidiasis in hospitalized patients.

Nosocomial outbreak of systemic candidosis associated with parenteral nutrition

Eight patients in two surgical units developed systemic candidosis during a 40-day period from June 5 to July 13, 1987 (in five cases Candida albicans was identified). Three of them died. All cases belonged to a group of 27 patients receiving parenteral nutrition (PN), while among the 108 patients who did not receive PN, no cases were observed (p = .000001). Candida was cultured from two PN bags administered to the cases. A specialized nutrition nurse was responsible for the PN compounding and for maintaining administration sets in the two wards involved. An epidemiological investigation, in which 19 uninfected patients who had had PN were used as controls, showed no significant difference between cases and controls except that lipids were more frequently added to bags administered to cases (p = .0005). Furthermore, the bags administered to cases contained a higher average number of multidose constituents (p = .0008) when the comparison was focused on the two days before the onset of symptoms. Given the favorable medium provided by lipids, even a low level contamination of PN solutions during compounding and/or administration could have been responsible for the exposure of cases to multidose vials suggests, although not conclusively, that an extrinsic contamination occurred during compounding. Six isolates of C albicans were available from four cases. C albicans was cultured from the pharyngeal swabs of two physicians and three nurses, including the specialized nutrition nurse.

Clinical significance of Candida isolated from peritoneum in surgical patients

Over a 2-year period, all surgical patients from whom Candida was isolated from intra-abdominal specimens were evaluated. All but 1 of the 49 evaluable patients had either a spontaneous perforation (57%) or a surgical opening of the gastrointestinal tract (41%). Candida caused infection in 19 patients (39%), of whom 7 had an intra-abdominal abscess and 12 peritonitis. In the other 30 patients (61%), there were no signs of infection and specific surgical or medical treatment was not required. Candida was more likely to cause infection when isolated in patients having surgery for acute pancreatitis than in those with either gastrointestinal perforations or other surgical conditions. The development of a clinical infection was significantly associated with a high initial or increasing amount of Candida in the semiquantitative culture. Surgery alone failed in 16 of 19 patients (84%), of whom 7 died and 9 recovered after combined antifungal and surgical treatment. The overall mortality and the mortality related to infections were significantly higher in the patients with intraabdominal candidal infections than in those without such infections.

Clinical implications of positive blood cultures

Positive blood cultures can be classified according to their veracity (true-positive or false-positive culture), clinical severity (inconsequential or life threatening), place of origin (community acquired or nosocomial), source (primary or secondary), duration (transient, intermittent, or continuous), pattern of occurrence (single episode, persistent, or recurrent), or intensity (high or low grade). In general, however, positive blood cultures identify a patient population at high risk of death. In my studies, patients with positive blood cultures were 12 times more likely to die during hospitalization than patients without positive blood cultures. Many bacteremias and fungemias occur in complicated clinical settings, and it appears that only about one-half of the deaths among affected patients are due directly to infection. Hence, it is appropriate to speak of "crude mortality" and "attributable mortality." Among hospitalized patients, recent trends include rising incidences of Staphylococcus aureus and coagulase-negative staphylococcal and enterococcal bacteremias and a dramatic increase in the incidence of fungemias. The diagnostic and therapeutic implications of blood cultures positive for specific microorganisms continue to evolve and are the subject of a large and growing medical literature.

Modifications of a Candida albicans biotyping system

Methods of preparing and plating inocula onto media for the Odds and Abbott Candida albicans biotyping system (F. C. Odds and A. B. Abbott, Sabouraudia 18:301-317, 1980; Odds and Abbott, Sabouraudia 21:79-81, 1983) were altered to utilize inexpensive and commercially available supplies and equipment. The modified system correlates well with the reference system.

Characterization of Candida isolates from pediatric burn patients

To provide more detailed information about Candida epidemiology and pathogenesis in pediatric burn patients, Candida isolates from 113 patients collected over 3 years were identified at the species level and the serotypes and biotypes of the C. albicans isolates were determined. A total of 85% of the patients were colonized or infected by C. albicans, 18% by C. tropicalis, and 11% by C. parapsilosis. Although colonization or infection often was found at multiple sites and times, 87% of the patients were colonized or infected by only one Candida species or strain; the other 13% showed multiple colonizations or infections, some of which occurred simultaneously at the same site. C. albicans biotyping determined the tolerance of the isolates to pH (pH 1.4) and salt; flucytosine, borate, and safranine resistance; and ability to produce proteinase and assimilate urea, sorbose, and citrate; results are expressed as three-digit numbers. For isolates from three different anatomical sites, the distribution of the nine biotype characteristics was similar in all cases but one. Significantly more fecal than wound or throat isolates were resistant to safranine. Sixty-four different serotype-biotype combinations were found in the 96 patients with C. albicans infections or colonizations. Twenty-nine percent of all C. albicans isolates had the partial biotype -57, while 20 of the 96 patients had specifically serotype B, biotype 557 colonizations or infections. Eleven patients had the B557 infection when admitted; nine patients acquired the yeast in-house. Thirty percent of the C. albicans isolated from 23 adult patients at a nearby hospital also showed the -57 biotype pattern, suggesting that C. albicans isolates expressing this biotype are either extremely prevalent in nature or are more virulent than other C. albicans isolates.

Laboratory, clinical, and epidemiological aspects of coagulase-negative staphylococci

Coagulase-negative staphylococci, particularly Staphylococcus epidermidis, are increasingly important causes of nosocomial infection. Microbiologists and clinicians no longer can afford to disregard clinical isolates of coagulase-negative staphylococci as contaminants. Accurate species identification and antimicrobial susceptibility testing, in a clinically relevant time frame, are important aids in the diagnosis and management of serious coagulase-negative staphylococcal infections. Emphasis in the clinical laboratory should be placed on the routine identification of S. epidermidis and Staphylococcus saprophyticus, with identification of other species of coagulase-negative staphylococci as clinically indicated. The application of newer techniques, such as plasmid analysis and tests for slime production and adherence, contribute to our understanding of the epidemiology and pathogenesis of coagulase-negative staphylococci and may also be helpful in establishing the diagnosis of infection.

Vascular-access infections in hospitalized patients

Vascular catheters are a common source of nosocomial infections, although many of these infections are potentially preventable. A long duration of catheterization, multiple catheter manipulations, the inexperience of some inserters, use of transparent plastic dressings, violations of aseptic technique, the use of multilumen catheters, and inadequate sterilization of reusable pressure transducers all increase the risk of these infections. The only interventions that have been proved to reduce the risk are standardized insertion and maintenance technique by an intravenous-therapy team, preinsertion skin preparation with chlorhexidine gluconate, and the use of topical antibiotics at the insertion site. The goal of the physician should be to prevent catheter infection, because the treatment of established infection can be difficult and costly. Treatment must be individualized for each patient on the basis of the clinical presentation and the causative organism.