Molecular typing of coagulase-negative staphylococci from blood cultures does not correlate with clinical criteria for true bacteremia

PURPOSE: Determining whether a blood culture that contains coagulase-negative staphylococci represents bacteremia or contamination is a clinical dilemma. We compared molecular-typing results of coagulase-negative staphylococcal blood culture isolates with clinical criteria for true bacteremia. SUBJECTS AND METHODS: Pulsed-field gel electrophoresis and arbitrary primed polymerase chain reaction (PCR) were used to determine whether patients with two or more blood cultures with coagulase-negative staphylococcal isolates had the same strain of organism in each culture (same strain bacteremia). We evaluated three different clinical criteria for bacteremia: whether the patient received more than 4 days of antibiotics, whether there was an explicit note in the medical chart in which the physician diagnosed a true bacteremia, and the Centers for Disease Control surveillance criteria for primary bloodstream infection. Agreement between same-strain bacteremia and each definition was examined, based on the assumption that most true infections should be the result of a single strain. RESULTS: The study sample consisted of 42 patients and 106 isolates. Nineteen of the 42 bacteremias (45%) were the same strain. Classification of bacteremias as same-strain correlated poorly with all three clinical assessments (range of percent agreement, 50% to 57%; range of kappa statistic, 0.01 to 0.15). There were both false-positive and false-negative errors. Patients with three or more positive blood cultures were more likely to have same-strain bacteremia than those with only two positive cultures [11 of 15 (73%) vs 8 of 27 (30%), P = 0.006]. Pulsed-field gel electrophoresis was more discriminating than arbitrary primed PCR (percent agreement, 83%; kappa, 0.67). CONCLUSION: Molecular typing correlated poorly with clinical criteria for true bacteremia, suggesting either that true bacteremias are frequently the result of multiple strains or that the commonly used clinical criteria are not accurate for distinguishing contamination from true bacteremia. Vancomycin treatment of clinically defined coagulase-negative staphylococcal bacteremia may frequently be unnecessary.     

Blood stream infections throught the entire course of acute lymphoblastic leukemia treatment

The incidence, type and mortality of bacteremias were evaluated in a pediatric patient cohort, during the entire course of treatment for acute lymphoblastic leukemia (ALL). Eighty-six patients with newly diagnosed ALL were studied. A bacteremic episode was defined as blood isolation of a pathogen in the presence of clinical symptomatology of septicaemia. Bacteremias were analyzed according to the treatment element being delivered and the degree of neutropenia. A central venous catheter (CVC) was inserted at diagnosis in all patients. Fifty-two episodes of bacteremias were encountered in 38/86 (44%) patients, while 48/86 patients had no positive blood culture. Three out of the 38 patients had bacteremia and CVC area infection, simultaneously. Most blood stream infections (29/52, 56%) were documented during the induction phase. Isolated Gram-positive organisms were 48%, Gram-negative 50% and 2% of the positive blood cultures represented fungaemias. The most common Gram-positive isolates were Staphylococcus species (N=22) and the commonest Gram-negative isolated pathogens were Escherichia coli and Pseudomonas aeruginosa. The majority of bacteremias (75%) occurred during neutropenia. The initial antibiotic treatment was ceftazidime or piperacillin/tazobactam and amikacin or tobramycin. CVC was not removed in the majority of bacteremias (94%). No infection related fatality was recorded. Bacteremias constituted a severe and common complication in our patient cohort. However, infection-related fatality rate was negligible, most probably due to the prompt initiation of broad coverage antimicrobial therapy.     

Endemic nosocomial Acinetobacter calcoaceticus bacteremia. Clinical significance, treatment, and prognosis

The medical records of 27 patients with blood cultures positive for Acinetobacter calcoaceticus over a recent five-year period (0.7% of all positive blood cultures) were reviewed retrospectively to determine the epidemiologic and clinical significance of these isolates. Eighteen isolates represented true bacteremias, 16 of which were hospital acquired. Patients most frequently were located in an intensive care unit or on a surgical ward. A seasonal July-to-September peak incidence was noted. The most common site of primary infection was the respiratory tract. Aminoglycosides, alone or in combination with a second agent, were used to treat all but one infection. Bacteriologic cure was achieved in 15 cases (88%); six patients had polymicrobial sepsis that carried a higher mortality than pure A calcoaceticus bacteremia (50% vs 0%). Acinetobacter, a low-virulence opportunistic pathogen, may be an infrequent but potentially serious endemic agent of nosocomial bacteremia in some institutions. The prognosis of bacteremia, when appropriately treated, appears to be good.     

Effect of fluconazole prophylaxis on fungal blood cultures: an autopsy-based study involving 720 patients with haematological malignancy

To investigate the utility of blood culture of invasive fungal infections in patients with haematological malignancies, an autopsy survey was conducted in 720 patients who were treated between 1980 and 1999. We identified 252 patients with invasive mycosis. These included Candida (n = 94), Aspergillus (n = 91), Zygomycetes (n = 34), Cryptococcus (n = 7), Trichosporon (n = 11), Fusarium (n = 1), and unknown fungi (n = 20). Of the 94 patients with invasive candidiasis, 20 had positive blood cultures. Of the 11 patients with invasive trichosporonosis, seven had positive blood cultures. The sensitivities of blood cultures were 1.1%, 0% and 14% for detecting invasive aspergillosis, zygomycosis and cryptococcosis respectively. Multiple regression analysis showed a significant correlation between results of Candida blood cultures and some variables, including prophylactic use of absorbable antifungals (P = 0.0181) and infection by Candida albicans (P = 0.0086). The sensitivity of blood cultures decreased when patients received antifungal chemoprophylaxis. Unless these agents are inactivated in culture bottles, conventional blood cultures might produce false-negative results.     

Epidemiology of bacteriuria caused by vancomycin-resistant enterococci--a retrospective study

BACKGROUND: The epidemiology of vancomycin-resistant enterococcal (VRE) bacteriuria has not been previously described. Our objectives are to describe the frequency of VRE bacteriuria, to use strict definitions to distinguish symptomatic urinary tract infection (UTI) versus urine colonization without pyuria versus asymptomatic bacteriuria with pyuria, and to describe the outcomes of each group. METHODS: We used a retrospective analysis of patients with VRE bacteriuria in an academic medical center. RESULTS: During the 18-month study period, 98 of the 107 patients (92%) with urine cultures positive for VRE (23/10,000 admissions), had charts that were available for review. In 94 of 98 patients, the organism was Enterococcus faecium, and in only 4 was Enterococcus faecalis recovered. Thirty-seven patients were colonized with VRE; 21 patients had asymptomatic bacteriuria, and the status of 27 patients was not ascertainable. Thirteen patients had VRE UTIs with two associated bacteremias and one death. Patients with UTI versus patients without UTI were more likely to have an underlying malignancy (39% vs 9%, P =.014). CONCLUSION: The majority of urine cultures yielding VRE do not represent true infection, rather colonization or asymptomatic bacteriuria.     

Bacteremia due to gram-positive cocci in patients with neoplastic disease.

Fifty-seven bacteremias caused by gram-positive cocci were observed over a four and a half year period in patients with a wide variety of malignant diseases. All patients had two or more positive antemortem blood cultures with the same microorganism. The number of bacteremic episodes were divided between Streptococcus pneumoniae (14), other streptococci (17) and Staphylococcus aureus (26). Seventy per cent, including 50 per cent of the pneumococcal bacteremias, were nosocomial. An identifiable portal of bacterial entry in the skin or the gastrointestinal or respiratory tract mucosa was present in 95 per cent, fever in 81 per cent and a prebacteremic performance status of less than 2 in 53 per cent. Granulocytopenia was present in only 18 per cent of the cases at the onset of the bacteremia. These bacteremias appeared to be responsive to antimicrobial therapy with an over-all immediate mortality rate of 23 per cent; 16 per cent in adequately treated patients. Poor outcome was associated with a prebacteremic performance status of 3 or 4, other than optimal antimicrobial therapy, a neutrophil count of less than 1,000/mm³ at the onset of the infection, and bacteremia due to Strep, pneumoniae. Hospitalized cancer patients, especially those with a poor performance status, should be monitored closely for breaks in the mucocutaneous host defense barriers and, if these are present in the face of suspected systemic infection, initial antimicrobial therapy should include drugs appropriate for the treatment of gram-positive coccal microorganisms.     

Difference in time to positivity is useful for the diagnosis of catheter-related bloodstream infection in hematopoietic stem cell transplant recipients

Catheter-related bloodstream infections are associated with recognized morbidity and mortality. Accurate diagnosis of such infections results in proper management of patients and in reducing unnecessary removal of catheters. We carried out a prospective study in a bone marrow transplant unit to assess the validity of a test based on the earlier positivity of central venous blood cultures in comparison with peripheral blood cultures for predicting catheter-related bacteremia. Between May 2002 and June 2004, 38 bloodstream infections with positive simultaneous central venous catheter and peripheral vein blood cultures were included. A total of 22 patients had catheter-related bacteremias and 16 had noncatheter-related bacteremias, using the catheter-tip culture/clinical criteria as the criterion standard to define catheter-related bacteremia. Differential time to positivity of 120 min or more was associated with 86% sensitivity and 87% specificity. In conclusion, differential time to positivity of 120 min or more is sensitive and specific for catheter-related bacteremia in hematopoietic stem cell transplant recipients who have nontunnelled short-term catheters.     

Clinical and epidemiologic significance of coagulase-negative staphylococci bacteremia in a tertiary care university Israeli hospital

OBJECTIVES: To characterize the clinical significance of coagulase-negative staphylococci (CNS) bacteremia. DESIGN: Prospective cohort study. SETTING: A 900-bed hospital in Haifa, Israel, from November 1996 to March 1997. RESULTS: Of 137 episodes of positive blood cultures for CNS, 41 (30%) were considered as true infection. Twenty-seven of 119 episodes associated with only 1 blood culture positive for CNS (23%) met the definition of infection as compared with 14 of 18 episodes (78%) associated with 2 or more blood cultures positive for CNS (P <.001). Methicillin resistance was significantly more frequent among Staphylococcus epidermidis isolates of episodes of true bacteremia than of episodes of contamination (15 of 22 [68%] vs. 11 of 33 [33%], respectively; P =.02). S hominis was isolated only in episodes considered as contamination (P =.01). It was estimated that CNS represents 24% of all nosocomial bloodstream pathogens. When CNS were isolated in the first 48 hours of hospitalization, an intravascular device was more frequently associated with episodes of true bacteremia than in those considered as contamination (7 of 7 [100%] vs. 10 of 57 [18%], respectively; P <.001). The mortality rate among patients with true CNS bacteremia was 16%. CONCLUSION: Some laboratory parameters may help identify episodes of true CNS bacteremia, which appears to be more common than previously considered.     

Staphylococcus aureus in a single positive blood culture: causes and outcome

Single positive culture was encountered in 61/235 patients (26%) with Staphylococcus aureus in blood culture over a 2-y period. It represented either true bacteremia (n = 52 cases; 85.2%) or contamination (n = 9; 14.8%). In comparison to cases with < or = 2 positive cultures, these patients did not have less severe disease or a lower incidence of complications.     

Predicting bacteremia in hospitalized patients. A prospectively validated model

OBJECTIVE: To develop and validate a model for the prediction of bacteremia in hospitalized patients, and to identify subgroups of patients with a very low likelihood of bacteremia in whom a positive blood culture has a low positive predictive value. DESIGN: Prospective cohort study with clinical data on 1516 episodes collected from a random sample of all patients who had blood cultures done at one institution. SETTING: Urban, tertiary care hospital. PATIENTS: Derivation set: 1007 blood culture episodes sampled from all blood cultures done on patients at Brigham and Women's Hospital between October 1988 and February 1989. Validation set: 509 episodes, May 1989 to June 1989. The unit of evaluation was the episode, defined as a 48-hour period beginning after a blood culture was drawn. MEASUREMENTS AND MAIN RESULTS: True- and false-positive rates of blood cultures in the derivation set as assessed by independent reviewers were 7% (74 of 1007) and 8% (81 of 1007), respectively. Independent multivariate predictors of true bacteremia were temperature of 38.3 degrees C or higher, presence of a rapidly (less than 1 month) or ultimately (less than 5 years) fatal disease; shaking chills; intravenous drug abuse; acute abdomen on examination; and major comorbidity. In the low-risk group, defined by absence of these predictors, the misclassification rate of the model in the derivation set was 1% (4 of 303), and a positive blood culture had a positive predictive value of only 14% for true bacteremia. The model also identified a high-risk subset in which 16% (41 of 264) of episodes represented true bacteremia. The model was prospectively validated in 509 additional episodes, and the misclassification rate in the low-risk group was 2% (3 of 155). INTERVENTIONS: None. CONCLUSION: These findings provide a means of stratifying hospitalized patients according to their risk for bacteremia. If prospectively validated in other settings, this model may be helpful when deciding whether or not to do blood cultures or start antibiotic therapy and, when evaluating a positive blood culture, to determine whether or not it is a true-positive.     

The relevance of cultures of catheter-drawn blood and heparin-lock fluid to diagnose infection in hematologic patients

Summary The results of bacteriologic cultures of blood and heparin-lock fluid, both drawn from the central venous catheters of 54 consecutive oncohematologic patients, have been used to determine their value for the diagnosis of systemic and catheter-associated infection. In 30 patients with clinical signs of infection (bacteremia or septicemia), 74 of 1000 (7.4%) heparin-lock fluid cultures, 114 of 542 (21%) catheter-drawn blood cultures, and 36 of 134 (26%) venipuncture blood cultures became positive, whereas in 24 patients without clinical signs of infection the respective values were 5 of 700 (0.7%), one of 220 (0.4%), and none of ten cultures. Comparison of the results of cultures sampled on the same day reveals that the positive and negative predictive values for catheter-drawn blood cultures, with the venipuncture blood cultures taken as the standard for bacteremia, are 82% and 95% respectively. The results of heparin-lock fluid are indicative for clinically relevant colonization of the catheter. Three or more positive heparin-lock fluid cultures, sampled on subsequent days, were correlated with the occurrence of bacteremia or septicemia with a positive predictive value of 100%. The conclusions are supported by the results of scanning electron microscopy.     

Blood culture isolates in hemodialysis vascular catheter-related bacteremia

Hemodialysis requires reliable and recurrent access to the central circulation and arteriovenous fistulas or grafts are the preferred modes of vascular access. However, in many patients the use of external tunneled vascular catheters may be necessary. The major complication of tunneled catheters is infection. Understanding local epidemiologic patterns of dialysis catheter-related bacteremia may help in the management of these patients. To address this issue, we reviewed the 5-year microbiologic culture results from all bacteremic hemodialysis patients with tunneled catheters at our institution. During this period, there were 203 organisms isolated from 153 positive blood cultures. Gram-positive, Gram-negative, and fungal species represented 55.7%, 43.3%, and 1% of isolates, respectively. Positive blood cultures classified according to the presence of a single Gram-positive or single Gram-negative organism, single fungus, or polymicrobial organisms, accounted for 41.8%, 29.4%, 0.6% and 28.1% of infectious events. From 2000-2004, there was a numerical trend toward a decrease in Gram-positive infection (64.3% versus 34.8% respectively, P = 0.12) and a numerical trend toward an increase in Gram-negative and polymicrobial bacteremias (17.9 versus 21.7, P = 0.07 and 17.9 versus 43.5, P = 0.09, respectively). These data indicate that bacteremic events in hemodialysis patients with vascular catheters are commonly due to a single Gram-positive organism, but the incidence of Gram-negative and polymicrobial bacteremia may be increasing. If confirmed in a prospective trial, adjustment of empiric antibiotic regimens for suspected catheter-associated bacteremia may be indicated.     

Impact of echocardiography in the short- and long-term prognosis of patients with infective endocarditis and negative blood cultures

BACKGROUND AND AIM OF THE STUDY: Higher morbidity and mortality have been attributed to patients suffering endocarditis but with negative blood cultures. The study aim was to determine whether, in the present era of routine echocardiography, patients with negative-culture endocarditis had a worse short- and long-term outcome, and whether outcomes in patients with true negative and aborted positive blood cultures were different. METHODS: When endocarditis was clinically suspected, an early (<24 h) echocardiographic examination was performed in all patients, regardless of blood culture results. In total, 151 patients diagnosed with infective endocarditis (IE) comprised the study group. Among these patients, 40 (26%) had negative blood cultures, and 28 of this subgroup (70%) had received previous antibiotic therapy. Short- and long-term features and prognosis were compared between both groups. The combined main end-point was death or need for surgical repair. RESULTS: Similar anatomic and clinical characteristics were present among those patients with positive and negative cultures. In addition, mortality and need for surgery with regard to short- and long-term follow up of both groups was similar. There were no significant differences between patients with true- or aborted-negative cultures in terms of short- and long-term prognosis. CONCLUSION: No differences in short- and long-term prognosis were seen among patients with IE and positive versus negative blood cultures. The prognosis was also similar between those with true negative culture versus aborted negative cultures. Early echocardiography in patients with clinically suspected IE may have changed the outcome in patients with negative cultures.     

Bacteremia caused by digestive system endoscopy.

AIM: to evaluate bacteremias caused during endoscopic examination of the digestive tract. PATIENTS AND METHODS: prospective study of randomly selected patients who underwent digestive system endoscopic examination. Emergency endoscopic examinations were excluded. RESULTS: a total of 102 patients were analyzed. Of 44 patients who underwent gastroscopy, 11 (25%) subsequently had positive blood culture, and Staphylococcus spp and Streptococcus spp were isolated. Of 30 patients who underwent colonoscopy, 3 (10%) had positive blood cultures, and Staphylococcus spp were isolated. Of 28 patients who underwent endoscopic retrograde cholangiopancreatography, 11 (39.2%) had positive blood cultures, and Escherichia coli, Morganella morganii, Staphylococcus spp and Streptococcus spp were isolated. No deaths, endocarditis or other septic phenomena were attributed to bacteremia. CONCLUSIONS: the incidence of bacteremia ranged from 10% to 39% depending on the type of endoscopy. The microorganisms that were isolated most frequently were Staphylococcus spp and Streptococcus spp. Gram-negative bacilli and enterobacteria were isolated in patients who had undergone endoscopic retrograde cholangiopancreatography.     

Survey of blood cultures from five community hospitals in south-western Sydney, Australia, 1993–1994

Background : Blood culture results have profound implications for patients. Comprehensive overviews of blood cultures have been uncommon, and focused on tertiary referral hospitals.
Aim : To present a review of blood culture results from a laboratory servicing community hospitals in Sydney, Australia.
Methods : Retrospective chart review of patients with positive blood cultures from 1 June 1993 to 31 May 1994.
Results : During the survey period there were 107,382 hospital admissions; 12,109 blood culture sets from 9292 patients were processed. Of these 1197 sets were positive, representing 974 febrile episodes in 923 patients. There were 476 episodes of contamination. Of the episodes of true bacteraemia, Escherichia coli was isolated in 139, Staphylococcus aureus in 91 (22 methicillin-resistant), other enterobacteriaceae in 60, and Streptococcus pneumoniae in 51. The diagnoses attributable to bacteraemia included intravenous catheter-related sepsis (122 episodes), urinary tract infection (88), bacteraemia from unknown source (79), intra-abdominal and biliary sepsis (91), pneumonia (35), and meningitis (21). Sixty-eight patients died directly due to bacteraemia. Multivariate analysis showed underlying disease (OR 3.97) or shock (OR 28.1) predicted death. Blood cultures confirmed clinical diagnoses in 258 episodes, but made a de novo diagnosis in 205 episodes.
Conclusions : This study describes the clinical and laboratory features of bacteraemias occurring in smaller public hospitals, as distinct from tertiary referral centres. It demonstrated that intravenous catheter-related sepsis was very common in smaller hospitals. The clinical diagnosis was frequently confirmed, and a de novo diagnosis was often established by a positive blood culture. Unfortunately nearly half the positive blood cultures represented contamination.     

Defining the population-based burden of nosocomial pneumococcal bacteremia

BACKGROUND: The characteristics, risk factors, and outcome of patients with nosocomial pneumococcal bacteremia (NPB) have not been described in large, population-based studies. METHODS: All episodes of invasive pneumococcal infections reported by Finnish clinical microbiology laboratories (positive blood or cerebrospinal fluid culture) from January 1, 1995, through December 31, 2002, were linked to data in national health care registries and vital statistics to obtain information on the patient's preceding hospitalizations, comorbidities, and outcome of illness. Pneumococcal bacteremia was defined as nosocomial if the first positive blood culture was obtained more than 2 days after hospital admission, or if the patient had been hospitalized for more than 2 days within 7 days of the first positive blood culture. RESULTS: Information on hospital admission was available for 4217 of 4357 persons (96.8%) with invasive pneumococcal infections. We identified 387 NPBs (9.7%) among 3973 pneumococcal bacteremias. Patients with NPB were older (median age, 67 years vs 52 years; P < .001) and were more likely to have at least 1 high-risk condition (other than age > or = 65 years), for which 23-valent pneumococcal polysaccharide vaccine is recommended (59.2% vs 34.6%; P < .001), compared with patients who had community-associated pneumococcal bacteremias. The case fatality proportion at 28 days was higher in patients with NPB than in those with community-associated pneumococcal bacteremias (23.8% vs 10.8%; P < .001). Pneumococcal serotypes included in 23-valent polysaccharide vaccine and 7-valent conjugate vaccine caused 71.5% and 46.1% of NPBs, respectively. CONCLUSIONS: A substantial proportion of pneumococcal bacteremias are health care associated. The high prevalence of conditions for which pneumococcal polysaccharide vaccine is recommended provides opportunities for strengthening prevention efforts in these patients at high risk of illness and death.     

Cross-contamination of Mycobacterium tuberculosis culture in clinical laboratories

For many years, it has been thought that positive culture of M. tuberculosis is a definitive diagnostic evidence of tuberculosis and cross-contamination of M. tuberculosis culture in clinical laboratories is rare. However recently introduced RFLP analysis has enabled us to identify a strain of M. tuberculosis, and many cases of the cross-contamination in clinical laboratories confirmed by RFLP analysis have been reported. In this report, we present the first case of the cross-contamination confirmed by RFLP in Japan. In our case, 5 patients without any personal link to each other were suspected based on clinical findings to have cross-contaminated results of M. tuberculosis culture. All their specimens were processed on the same day, and were smear negative and culture positive with only a small number of colonies (less than 8 colonies). The sputum from the suspected source of contamination processed on the same day was strongly positive for AFB smear and heavily culture positive. The RFLP patterns of these 6 patients were identical, so it was concluded that the positive cultures of the sputum from the 5 patients who were not expected to be culture positive on clinical findings were caused by the cross-contamination in our hospital laboratory. We review all the charts of patients with M. tuberculosis culture positive results in the same year of this case, but we didn't find no other cases suspected of the cross-contamination. Then we reviewed the literature of M. tuberculosis culture cross-contamination. The patterns of the cross-contamination are divided into two. One is associated with malfunction of a sampling needle in the BACTEC 460 system and the other associated with the initial processing of the specimens, mostly involving reagents such as NaOH solution. Cross-contaminated specimens are usually smear negative with only a few colonies (less than 5), and processed just after the source specimen of the contamination in most reported cases, but not in all. In almost half of them the cross-contamination results had significant influence on the clinical management. The frequency of the cross-contamination is estimated around 1% of the patients with M. tuberculosis culture positive results. For early detection of the cross-contamination, not only clinicians but also laboratory staffs have important role and close cooperation between them is mandatory. To prevent the contamination, it is advisable to process smear positive and probable culture positive specimens separately from others, and not to use a large same container of reagents for processing of different specimens.     

Time to positivity of blood culture in newborn infants

The purpose of this study was to evaluate the minimum incubation time required to detect positive blood cultures from newborn infants with sepsis. Data were collected retrospectively on seventy-five positive blood cultures from newborn infants in the neonatal intensive care unit of Songklanagarind Hospital. The BacT/Alert Microbial Detection System had been used to culture the samples. Data were obtained retrospectively from the patients' medical records for positive blood cultures. A computer algorithm in the automated blood culture system determined the time to positivity, which was then evaluated for clinically important definite bacterial pathogens, possible bacterial pathogens, fungi and contaminants. Definite bacterial pathogens accounted for 46% (34/74) of the positive blood culture results, possible bacterial pathogens accounted for 39% (29/74), fungi for 7% (5/74) and contaminants for 8% (6/74). The cultures were positive at 24, 36 and 48 hours of incubation in 70.2%, 91.8% and 95.9% respectively. At 36 hours of incubation, the sensitivity, specificity and negative predictive value were 70.3%, 100% and 93.3%, respectively. All cultures growing clinically significant definite bacterial pathogens were positive by 36 hours of incubations, 88% by 24 hours. The cultures had 100% sensitivity, specificity and negative predictive value at 36 hours of incubation. If definite and possible bacterial pathogens were considered, the time to positivity was 71% at 24 hours, 95% at 36 hours and 97% at 48 hours, respectively. The sensitivity, specificity and negative predictive values were 70.3%, 100%, and 93.3%, respectively. Of cultures growing fungi, 80% were positive by 36 hours and all by 48 hours.     

Pseudo-Outbreak of Ventriculitis in a Neurosurgical ICU

BACKGROUND: Infection is a potentially life-threatening complication of ventriculostomy placement. Placement of ventricular catheters frequently occurs outside the setting of the operating room. We typically detect <10 nosocomial central nervous system infections per year in our neurosurgical ICU. Over a 4–month period (May–August 2003), 19 positive cerebrospinal (CSF) cultures were noted in 10 patients. Organisms included coagulase-negative staphylococci (CNS, 16 cultures in 7 patients), Pseudomonas aeruginosa (4 cultures in 2 patients), and Acinetobacter lwoffi (1 culture in 1 patient).METHODS: An outbreak investigation was performed, including review of the patients' clinical course, laboratory data, ventriculostomy catheter insertion, site care, CSF specimen collection practices, and interviews with all involved staff.RESULTS: Investigation revealed ventriculostomy CSF specimens were collected by a single neurosurgical resident each month. Five (50%) of the patients were determined to have infection. CNS was found in all (10) contaminated cultures. Of 66 cultures obtained in August, 17 (26%) were culture positive, and 9 (14%) of these were contaminated. One resident obtained all cultures in August. Meetings were held between epidemiology department, neurosurgery faculty, and nursing staff. Practice changes were implemented to emphasize hand hygiene, aseptic collection techniques, and exit site care. Inservices were held for nursing staff and neurosurgery residents. Subsequent review of CSF cultures has revealed no further contamination.CONCLUSIONS: Continuing education of medical and nursing staff is required to prevent poor collection technique to prevent contamination of CSF obtained from ventriculostomy catheters. When investigating a potential outbreak, it is important to review all laboratory and clinical data to ensure that positive culture results represent true infection.     

Risk factors for Candida infections in a neonatal intensive care unit in Costa Rica.

OBJECTIVE: To identify potential risk factors associated with Candida infections and compare these risk factors between patients who both died and survived. STUDY DESIGN: A group of patients with positive Candida spp. blood cultures admitted to a neonatal intensive care unit (NICU) in Costa Rica between January 1994 and December 1998. Cases were identified through a computerized search of the microbiology laboratory's database on blood cultures. RESULTS: One hundred and ten newborns were identified. Sixty-six patients (60%) were male; 46 (62%) were preterm infants. Thirty-seven (34%) patients died. Twenty (54%) of them died within three days of the candidemia diagnosis and 17 had disseminated Candida infection on autopsy. Candida albicans and Candida tropicalis were isolated in 90% and 10% of blood cultures, respectively. Mean +/- SD (range) number of days from admission to NICU to the initial positive blood culture were 13.5 +/- 8.5 (1-30) days. Most patients had at least two positive blood cultures (range 1-8). Median (range) days for the sterilization of blood culture were four (1-25) days. Significant differences in survival were identified in patients with axillary-inguinal lesions, apnea and seizures. CONCLUSIONS: Invasive fungal infections are frequent in NICU. Future case-control prospective studies should be carried out to confirm the findings from this report.