Clinical utility of blood cultures drawn from central vein catheters and peripheral venipuncture in critically ill medical patients

STUDY OBJECTIVE: To determine the sensitivity, specificity, and positive and negative predictive values of blood cultures obtained through a central vein catheter compared with peripheral venipuncture. DESIGN: Prospective cohort study. SETTING: A medical ICU (19 beds) from a university-affiliated urban teaching hospital. PATIENTS: Between February 2001 and October 2001, 300 paired blood culture specimens were obtained from 119 patients (2.52 paired cultures per patient). INTERVENTION: Prospective patient surveillance and data collection. Measurements and main results: Thirty-four paired culture results (11.3%; 95% confidence interval, 7.8 to 14.8%) were accepted as true-positives representing a true bacteremia. The sensitivity of catheter-drawn and peripheral venipuncture samples was 82.4% and 64.7%, respectively, and specificity was 92.5% and 95.9%. The positive predictive value was 58.3% for catheter-drawn samples and 66.7% for peripheral venipuncture samples, and the respective negative predictive values were 97.6% and 95.5%. CONCLUSIONS: In critically ill medical patients, the negative predictive value of blood samples obtained by catheter draw or peripheral venipuncture for suspected bloodstream infection is good. However, the sensitivity of blood samples obtained by either catheter draw or peripheral venipuncture alone is not adequate to recommend the elimination of blood samples obtained from the other site. Clinicians should also be aware that additional blood samples may be necessary when interpreting positive blood culture results for common skin or central vein catheter contaminants.     

Clinical utility of blood cultures drawn from indwelling central venous catheters in hospitalized patients with cancer

BACKGROUND: Because of concern about low specificity, the American College of Physicians guidelines and expert opinion discourage the use of a central venous catheter when obtaining blood for culture for bacteremia or fungemia. However, data on the reliability of cultures done with blood obtained from a central venous catheter are conflicting. OBJECTIVE: To determine the sensitivity, specificity, and positive and negative predictive values of cultures done with blood obtained through a central venous catheter compared with peripheral venipuncture. DESIGN: Retrospective cohort study of hospitalized patients with cancer in whom samples for paired cultures were drawn through a central venous catheter and peripheral venipuncture. SETTING: Tertiary care, university-affiliated medical center. PATIENTS: 185 patients hospitalized on a hematology-oncology ward between August 1994 and June 1996. MEASUREMENTS: Blinded assessments of culture results done by infectious disease experts were used as the gold standard. Sensitivity, specificity, and positive and negative predictive values were compared for culture of blood from central catheters and culture of blood from peripheral venipuncture. RESULTS: Of 551 paired cultures, 469 (85%) were catheter-negative/venipuncture-negative, 32 (6%) were catheter-positive/venipuncture-positive, 17 (3%) were catheter-negative/venipuncture-positive, and 33 (6%) were catheter-positive/venipuncture-negative pairs. For the 82 paired cultures with at least one positive result, blinded determination of true bacteremia or fungemia was made by two infectious disease specialists. For catheter draw compared with peripheral venipuncture, sensitivity was 89% (95% CI, 79% to 98%) and 78% (CI, 65% to 90%) (difference, 11 percentage points [CI, -6 to 28 percentage points]), specificity was 95% (CI, 93% to 97%) and 97% (CI, 96% to 99%) (difference, -2 percentage points [CI, -5 to 0.2 percentage points]), positive predictive value was 63% (CI, 50% to 75%) and 73% (CI, 60% to 86%) (difference, -10 percentage points [CI, -26 to 5 percentage points]), and negative predictive value was 99% [CI, 97% to 100%]) and 98% (CI, 96% to 100%) (difference, 1 percentage point [CI, -0.5 to 3 percentage points]). CONCLUSIONS: In hospitalized hematology-oncology patients, culture of blood drawn through either the central catheter or peripheral vein shows excellent negative predictive value. Culture of blood drawn through an indwelling central venous catheter has low positive predictive value, apparently less than from a peripheral venipuncture. Therefore, a positive result from a catheter needs clinical interpretation and may require confirmation. However, the use of a catheter to obtain blood for culture may be an acceptable method for ruling out bloodstream infections.     

Incidence of bacteremia in transesophageal echocardiography: a prospective study of 140 consecutive patients

The incidence of bacteremia related to transesophageal echocardiography was studied in 140 consecutive patients (71 women and 69 men with a mean age of 53.7 +/- 15 years). Thirty-four patients had one or more prosthetic heart valves. Blood cultures were obtained from each patient through separate venipuncture sites immediately before and after transesophageal echocardiography. An additional late blood culture was obtained in 114 patients 1 h later. The skin was cleaned with povidone-iodine and venipunctures were performed with separate butterfly needles with use of sterile gloves and drapes. Blood samples were drawn into separate syringes, transferred to aerobic and anaerobic culture bottles and processed with use of a semiautomated system. The overall incidence of blood cultures positive for bacteremia was 2% (8 of 394 bottles) and all positive cultures grew in a single blood culture bottle. Positive cultures occurred in 4 (1.4%) of 280 bottles before the procedure, in 2 (0.7%) of 280 bottles immediately after the procedure and in 2 (0.9%) of 228 late (1-h) blood culture bottles. Bacterial isolates were coagulase-negative staphylococci (n = 5), Propionibacterium (n = 2) and Moraxella (n = 1). All were considered contaminants. Mean endoscopic time in these patients was not significantly different from that in the other patients. Follow-up of patients with a blood culture positive for bacteremia revealed no clinical evidence of systemic infection. It is concluded that 1) the incidence of bacteremia related to transesophageal echocardiography is very low, and 2) the incidence of blood cultures positive for bacteremia after transesophageal echocardiography is indistinguishable from the anticipated contamination rate.     

Difficulty in predicting bacteremia in elderly emergency patients.

STUDY OBJECTIVES: To characterize the clinical presentation and identify factors predictive of bacteremia in elderly patients. DESIGN: Retrospective review of emergency department charts, hospital records, and microbiology reports. SETTING: Community teaching hospital with annual ED census of 65,000 adults. PARTICIPANTS: Seven hundred fifty elderly patients (aged 65 to 99 years) who were evaluated by the emergency physician, had blood cultures obtained in the ED, and were hospitalized with a suspected infectious process during a 12-month period. MEASUREMENTS: Records were analyzed for demographic information, underlying diseases, clinical presentation, laboratory findings, sources of infection, and causative organisms. Using contingency tables, 79 patients with positive blood cultures were compared with a random sample of 136 patients with sterile blood cultures to identify clinical variables significantly (P less than .05) associated with bacteremia. Logistic regression analysis was performed with significant factors to develop a model to predict bacteremia. Sensitivity, specificity, and predictive values were calculated for the model. MAIN RESULTS: The prevalence of bacteremia was 10.6%. Escherichia coli was the most commonly isolated pathogen (29% of cases), and the urinary tract was the most common source of infection (44.3% of cases). Logistic regression analysis showed that altered mental status (odds ratio, 2.88; 95% confidence interval [Cl], 1.52 to 5.50), vomiting (odds ratio, 2.63; 95% Cl, 1.16 to 6.15), and WBC band forms of more than 6% (0.06) (odds ratio, 3.50; 95% Cl, 1.58 to 5.27) were independent predictors of bacteremia. The presence of at least one of these three factors had a sensitivity of 0.85 (95% Cl, 0.75 to 0.92) and a specificity of 0.46 (95% Cl, 0.38 to 0.55) for predicting bacteremia in the study group. The positive predictive value was 0.16 (95% Cl, 0.12 to 0.19) and the negative predictive value was 0.96 (95% Cl, 0.94 to 0.98) for the ED patient group that met inclusion criteria. CONCLUSION: Elderly patients fail to manifest identifiable clinical features indicative of bloodstream infection. The sensitivity and specificity of the best statistical model for identifying bacteremic elderly patients suggest that clinical indicators alone are unreliable predictors of bacteremia in the geriatric ED population studied.     

Vascular catheter-associated fungemia in patients with cancer: analysis of 155 episodes.

We reviewed all 155 episodes of central venous catheter-associated fungemia among inpatients at the National Cancer Institute during a 10-year period. Candida species accounted for 98% of episodes. Fungemia was documented by culture of blood drawn through catheters in 50% of cases and by culture of both catheter-drawn and peripheral blood in 39%; mortality and the rate of dissemination were similar for these two groups. Four management strategies were used: catheter removal, antifungal therapy (with amphotericin B), both, or neither; indications for the use of both modes of treatment included fever, neutropenia, long-term indwelling catheterization, positive cultures of both catheter-drawn and peripheral blood, isolation of Candida tropicalis, and fungal isolation from two or more blood cultures. Disseminated fungal infection was documented in 82% of cases with these features but also in 35% of the less severe cases treated only with catheter removal. In addition, nine (82%) of 11 cases managed only with antifungal therapy had a negative outcome (either death from disseminated infection or the recurrence of fevers and/or fungemia), a finding suggesting that intravascular catheters should be removed in fungemia. Virtually all cases of catheter-associated fungemia in patients with cancer are clinically significant and require prompt therapy with amphotericin B.     

Predictors of bacteremia and gram-negative bacteremia in patients with sepsis. The Veterans Affairs Systemic Sepsis Cooperative Study Group.

BACKGROUND--We analyzed data from the Department of Veterans Affairs trial of steroid therapy for systemic sepsis to identify predictors of bacteremia and gram-negative bacteremia. METHODS--Of the 2568 patients screened for entry in the trial, 465 met the following criteria: presence of four of seven clinical signs of sepsis; blood cultures at the time of screening; and complete data on nine clinical parameters. The multivariate logistic regression model was used to identify predictors of bacteremia and gram-negative bacteremia. Predicted probabilities of having these types of infections were calculated using the identified predictors. Patients were then classified into groups with and without bacteremia (and gram-negative bacteremia) based on the predicted probability. Misclassification error rates were calculated for each method of categorization by comparing the true with the predicted grouping of patients. RESULTS--Three factors were independently predictive of bacteremia and gram-negative bacteremia: elevated temperature, low systolic blood pressure, and low platelet count. Using these three factors, classification methods were identified that predicted blood infection better than chance, but misclassification was also high. For predicting bacteremia, the maximum predicted positive rate was 83%, with a specificity of nearly 100% and a sensitivity of only 5%. For predicting gram-negative bacteremia, the maximum predicted positive accuracy was 100%, with a specificity also of 100% and a sensitivity of almost 0%. CONCLUSIONS--Using simple clinical parameters, we could not predict either bacteremia or gram-negative bacteremia with sufficient accuracy to be clinically meaningful; however, our approach represents a step in the direction of forecasting the bacterial organism responsible for sepsis in advance of culture results.     

Diagnostic Value of Procalcitonin for Bacterial Infection in Elderly Patients in the Emergency Department

OBJECTIVES: To evaluate the diagnostic performance of procalcitonin (PCT) in elderly patients with bacterial infection in the emergency department (ED). DESIGN: Prospective. SETTING: ED of a tertiary care hospital. PARTICIPANTS: Elderly patients with systemic inflammatory response syndrome (SIRS) enrolled from September 2004 through August 2005. MEASUREMENTS: A serum sample for the measurement of PCT, two sets of blood cultures, and other cultures of relevant specimens from infection sites were collected in the ED. Two independent experts blinded to the PCT results classified the patients into bacterial infection and nonbacterial infection groups. RESULTS: Of the 262 patients with SIRS enrolled, 204 were classified as having bacterial infection and 48 as having bacteremia. PCT levels were significantly higher in patients with bacteremia than in those without. The area under the receiver operating characteristic curve for identification of bacteremia according to PCT was 0.817 for the old‐old group (≥75), significantly higher than 0.639 for the young‐old group (65–74); P=.02). The diagnostic sensitivity, specificity, positive predictive value, and negative predictive value of PCT for bacteremia in patients aged 75 and older were 96.0%, 68.3%, 33.8%, and 98.8%, respectively, with a PCT cutoff value of 0.38 ng/mL. CONCLUSION: PCT is sensitive for diagnosing bacteremia in elderly patients with SIRS at ED admission but is helpful in excluding bacteremia only in those aged 75 and older. PCT is not an independent predictor of local infections in these patients.     

Febrile inpatients

The so-called “fever work-up” is time-consuming and costly. The authors examined the practices of medical house officers in obtaining blood cultures, an important part of this evaluation, as well as the ability of these physicians to predict bacteremia in febrile patients. They studied all 344 medical inpatients who experienced episodes of fever during two 30-day periods, as well as all 50 cases of bacteremia detected during these and two additional 30-day periods. House officers drew blood for culture within one day after the onset of fever in 52% of fever episodes. In 20% of these episodes only one set of cultures (representing one venipuncture) was obtained. House officers estimated the likelihood of bacteremia to be 20% or less in 15 of 40 bacteremic patients. They failed to obtain blood cultures promptly in 10% of bacteremic episodes and in 27% of episodes where the cause of fever was a nonbacteremic bacterial infection. They obtained prompt blood cultures in only a bare majority of febrile episodes, frequently underestimated the likelihood of bacteremia, and inadequately sampled blood for bacteremia. In this study, clinical judgment was not an adequate substitute for routinely obtaining blood cultures for febrile medical inpatients. Received from the Divisions of General Medicine and Primary Care, Consolidated Department of Medicine, Beth Israel Hospital and Brigham and Women’s Hospital; The Charles A. Dana Research Institute and the Harvard — Thorndike Laboratory, Beth Israel Hospital; The Henry J. Kaiser Fellowship Program; Harvard Medical School, Boston, Massachusetts; The Department of Medicine, Cambridge Hospital, Cambridge, Massachusetts; and the Department of Medicine, Montefiore Hospital, New York, New York. Supported in part by grants from the National Center for Health Services Research (HS 02063 and HS 04066), and by a grant from the Henry J. Kaiser Family Foundation.     

Incidence of bacteremia in cirrhotic patients undergoing upper endoscopic ultrasonography

Background

The incidence of bacteremia after endoscopic ultrasonography (EUS) or EUS-guided fine-needle aspiration (EUS-FNA) is between 0% and 4%, but there are no data on this topic in cirrhotic patients.

Aim

To prospectively assess the incidence of bacteremia in cirrhotic patients undergoing EUS and EUS-FNA.

Patients and methods

We enrolled 41 cirrhotic patients. Of these, 16 (39%) also underwent EUS-FNA. Blood cultures were obtained before and at 5 and 30 min after the procedure. When EUS-FNA was used, an extra blood culture was obtained after the conclusion of radial EUS and before the introduction of the sectorial echoendoscope. All patients were clinically followed up for 7 days for signs of infection.

Results

Blood cultures were positive in 16 patients. In 10 patients, blood cultures grew coagulase-negative Staphylococcus, Corynebacterium species, Propionibacterium species or Acinetobacterium Lwoffii, which were considered contaminants (contamination rate 9.8%, 95% CI: 5.7–16%). The remaining 6 patients had true positive blood cultures and were considered to have had true bacteremia (15%, 95% CI: 4–26%). Blood cultures were positive after diagnostic EUS in five patients but were positive after EUS-FNA in only one patient. Thus, the frequency of bacteremia after EUS and EUS-FNA was 12% and 6%, respectively (95% CI: 2–22% and 0.2–30%, respectively). Only one of the patients who developed bacteremia after EUS had a self-limiting fever with no other signs of infection.

Conclusion

Asymptomatic Gram-positive bacteremia developed in cirrhotic patients after EUS and EUS-FNA at a rate higher than in non-cirrhotic patients. However, this finding was not associated with any clinically significant infections.     

Mycobacterium tuberculosis bacteremia in a university hospital.

SETTING: Patients with blood cultures positive for Mycobacterium tuberculosis between 1988 and 1999. OBJECTIVE: To study the clinical and microbiological characteristics of patients with tuberculous bacteremia, including data about evolution and management. DESIGN: Retrospective review of the clinical charts and microbiological records of patients with culture-proven tuberculous bacteremia between 1988-1999. RESULTS: During the study period, 19 patients with culture-proven M. tuberculosis bacteremia were detected (1.42 isolates/patient, 4.7% of all patients with blood cultures for mycobacteria). Four patients were non-infected with the human immunodeficiency virus and 15 were HIV-infected. In four patients blood was the only positive sample. Five patients were diagnosed simultaneously with tuberculosis and HIV infection. Only 13 had a temperature higher than 37.5 degrees C. Most patients had symptoms or signs of respiratory tract involvement, and 11 patients died (10 from tuberculosis). The average time for detection of positive blood cultures was 33.25 days for lysis-centrifugation cultures and 26.46 days for BACTEC cultures. The incidence of M. tuberculosis bacteremia remained stable during the study period. CONCLUSIONS: Although blood cultures are useful for definitive diagnosis of disseminated tuberculosis, the long incubation times made them of limited usefulness in the clinical management of patients. Mortality remains high in these patients.     

Bacteremia associated with lower gastrointestinal endoscopy: Fact or fiction?

In an effort to elucidate whether bacteremia occurs during endoscopic examination of the lower gastrointestinal tract, two prospective spective studies were undertaken involving patients undergoing colonoscopy and proctosigmoidoscopy. The former group has been presented earlier, and the second study, which includes the proctosigmoidoscopy group, is the basis for this study. Fiftyseven patients undergoing proctosigmoidoscopy were studied. Excluded from the study were patients with fever, diarrhea, inflammatory bowel disease, valvular heart disease, vascular prosthesis, chemotherapy, and immunosuppression. Aerobic and anaerobic blood cultures were taken before, during, and after proctosigmoidoscopy. Additional cultures were taken after a biopsy or polypectomy. Skin cultures were taken from the venipuncture site prior to venipuncture. No bacteremia was demonstrated. Three blood cultures were positive, but all were considered contaminants on the basis of the nature of organisms. No correlates could be drawn as to the depth of insertion, length of time, or position of patient during the procedure. It is concluded that no significant bacteremia occurs during proctosigmoidoscopy. Further studies are warranted in the excluded high-risk group.     

Blood cultures in ambulatory patients who are discharged from emergency with community-acquired pneumonia.

OBJECTIVES: To determine the factors that predict whether or not ambulatory patients with community-acquired pneumonia (CAP) treated in an emergency room (ER) setting will have blood cultures drawn and the factors that predict a positive blood culture. METHODS: Prospective observational study of all patients with a diagnosis of CAP, as made by an ER physician, who presented to any of seven Edmonton-area ERs over a two-year period. RESULTS: Seven hundred ninety-three (19.2%) of 4124 patients with CAP had blood cultures drawn. The site-specific blood culture rates ranged from 7.8% to 25% (P<0.001); 41 of 793 (5.1%) were positive. Streptococcus pneumoniae accounted for 58.5% of the isolates while Staphylococcus aureus and Escherichia coli each accounted for 14.6%, or six patients each. Only two of the 24 patients with S pneumoniae bacteremia were subsequently admitted to hospital while all six of the patients with S aureus were admitted. Only one of the six patients with E coli bacteremia was treated at home. No factors were predictive of positive blood cultures on multivariate analysis. CONCLUSIONS: Physicians are selective in ordering blood cultures on patients with ambulatory pneumonia who present to an ER, and the positivity rate of 5.1% is quite high. No factors are predictive of positive blood cultures on multivariate analysis, thus clinical judgment has to prevail in the decision to perform blood cultures. Breakthrough bacteremia can occur with microorganisms susceptible to the antibiotics that the patient is receiving.     

Frequency and characteristics of hyperbilirubinemia associated with bacteremia

One hundred consecutive patients with blood cultures positive for microbial growth were prospectively surveyed for the presence of hepatic abnormalities and clinical evidence of infection. Complete data for 82 patients were available for analysis. Fifty-four percent had elevated bilirubin levels, and 34% had total bilirubin values of greater than or equal to 2.0 mg/dl. The levels of total bilirubin were disproportionately elevated compared with those of aspartate aminotransferase, alkaline phosphatase, and cholesterol. Nine of the 23 patients with elevated bilirubin levels had an increase in serum bilirubin one to nine days before their initial positive blood culture. Disproportionate elevations of direct and total serum bilirubin values compared with values for other liver-function tests appear to be associated with bacteremia in adults more frequently than previously recognized and may have some predictive value in such patients.     

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.     

Validación del modelo predictivo de bacteriemia (5MPB-Toledo) en los pacientes atendidos en el servicio de urgencias por infección

ObjectiveTo validate a simple risk score to predict bacteremia (MPB5-Toledo) in patients seen in the emergency departments (ED) due to infections.MethodsProspective and multicenter observational cohort study of the blood cultures (BC) ordered in 74 Spanish ED for adults (aged 18 or older) seen from from October 1, 2019, to February 29, 2020.The predictive ability of the model was analyzed with the area under the Receiver Operating Characteristic curve (AUC-ROC). The prognostic performance for true bacteremia was calculated with the cut-off values chosen for getting the sensitivity, specificity, positive predictive value and negative predictive value.ResultsA total of 3.843 blood samples wered cultured. True cases of bacteremia were confirmed in 839 (21.83%). The remaining 3.004 cultures (78.17%) were negative. Among the negative, 172 (4.47%) were judged to be contaminated. Low risk for bacteremia was indicated by a score of 0 to 2 points, intermediate risk by 3 to 5 points, and high risk by 6 to 8 points. Bacteremia in these 3 risk groups was predicted for 1.5%, 16.8%, and 81.6%, respectively. The model's area under the receiver operating characteristic curve was 0.930 (95% CI, 0.916-0.948). The prognostic performance with a model's cut-off value of ≥ 5 points achieved 94.76% (95% CI: 92.97-96.12) sensitivity, 81.56% (95% CI: 80.11-82.92) specificity, and negative predictive value of 98.24% (95% CI: 97.62-98.70).ConclusionThe 5MPB-Toledo score is useful for predicting bacteremia in patients attended in hospital emergency departments for infection.     

Bioelectrical impedance analysis predicts outcome in patients with suspected bacteremia

Summary  Fluid shifts from intracellular to extracellular water (ICW to ECW) are a feature of sepsis, caused by increased vascular permeability and cell catabolism. Changes in ECW and total body water (TBW) were assessed in a prospective observational study of patients with bacteremia by a bedside technique, and its prognostic impact determined. In 78 hospital patients with fever, the resistance ratio (Rinf/RO) and estimated ECW/TBW ratio from multifrequency bioelectrical impedance analysis, and serum albumin concentration were measured. Rinf/RO and ECW/TBW ratios decreased from day 0 to 2 in patients with significant bacteremia (n=31), but not in patients with doubtful or negative blood cultures (n=22 and 25). Increased Rinf/RO at baseline, and further increase of ECW/TBW from day 0 to 2, were associated with lower rate of recovery after 1 week and with higher mortality. Baseline Rinf/RO above the media (0.75) had positive and negative predictive values of 0.31 and 0.95 for death. This prognostic effect was independent of underlying disease and blood culture result in a multivariate model. Hypoalbuminemia at baseline was predictive of outcome, but changes in albumin from day 0 to 2 were unrelated to blood culture results or outcome. In patients with bacteremia, fluid shifts from intracellular to extracellular water occur early, are rapidly reversible by antibiotic treatment but are associated with adverse prognosis. Bioelectrical impedance deserves further study as a tool for bedside monitoring of patients with bacteremia.     

Use of blood cultures in the emergency department

While the use of blood cultures to detect septicemia is a time-honored and valuable laboratory technique, guidelines for obtaining such cultures are vague. Several controversies exist regarding the utilization of blood cultures in the ambulatory setting, including when and on whom cultures should be obtained, how many cultures should be obtained, and how much blood should be obtained with each venipuncture. The guidelines have become slightly more confusing with the recognition of an entity known as occult bacteremia. A number of studies that bear relevance to these issues are reviewed. The utility of obtaining blood cultures in the ambulatory setting is examined, and guidelines are offered for obtaining blood cultures in adult and pediatric populations. Areas in which further research may be appropriate also are noted.     

Bacteremic disease due to Haemophilus influenzae capsular type f in adults: report of five cases and review

Five cases of bacteremic infections due to Haemophilus influenzae type f in adults are described, and previous reports of type f disease in nonpediatric patients are reviewed. Respiratory tract infections were most common in our series (two cases of pneumonia, one of epiglottitis, and one of nosocomial septicemia probably resulting from aspiration pneumonitis). All of these patients had factors predisposing them to respiratory tract infections, e.g., neurologic disease, congestive heart failure, or cigarette smoking. A fifth patient, who was bacteremic without an apparent primary focus, had dysgammaglobulinemia. Six episodes of bacteremia occurred in five patients; 11 of 13 cultures of blood obtained before parenteral antibiotic therapy were positive. All isolates were biotype I and susceptible to ampicillin. Antibiotic therapy was curative in cases of proved respiratory tract infection but failed in the setting of nosocomial septicemia, perhaps because of delayed initiation. The brevity of antibiotic treatment of the cryptogenic bacteremia permitted infection of a prosthetic vascular graft and recurrent bacteremia. Graft removal and repeated antibiotic therapy were curative.     

161例肝病患者败血症菌群分布及药敏分析

目的 了解我院肝病患者败血症的菌群分布及对常用抗生素的敏感性。方法 对4年来血培养阳性的肝病患者进行分析。结果 161例败血症患者共检出细菌175株。革兰阴性菌128株，占73．7％，其中大肠杆菌占28．6％；革兰阳性菌44株，占25．1％；真菌3株，占1．7％。结论 我院肝病患者败血症的主要病原菌为革兰阴性菌，治疗宜首选第3代头孢菌素，广谱β-内酰胺酶菌株应首选泰能。治疗革兰阳性菌的最佳抗生素为万古霉素。     

Routine use of anaerobic blood cultures: are they still indicated?

PURPOSE: To determine the number of patients with bacteremia and fungemia and to evaluate the utility of routine anaerobic blood cultures as part of the work-up for suspected bacteremia. SUBJECTS AND METHODS: Retrospective review of microbiology data followed by selective chart review at a university-affiliated Veterans Affairs Medical Center. We determined the number of bacterial blood cultures drawn from January 1, 1994, to December 31, 1996, and the number of anaerobic, aerobic, and fungal isolates. Chart reviews were then performed on all patients with a positive anaerobic result.RESULTS: There were 6,891 sets of blood cultures processed through the laboratory, yielding 1,626 patients with positive results. Anaerobic isolates were recovered from 36 patients (2.2%) in 48 bottles. Aerobic isolates were recovered from 1550 patients (95.3%), and fungal isolates were recovered from 40 patients (2.5%). Seven patients (0.4%) had true anaerobic bacteremia. All seven patients had an obvious source of anaerobic infection that was known or suspected before the cultures were drawn. Antibiotic changes were made in four of these patients after the positive anaerobic results were known. Antibiotic changes led to clinical improvement in one patient. CONCLUSIONS: Routine use of anaerobic blood cultures rarely results in clinically important diagnostic or therapeutic benefits, based on the low incidence of anaerobic bacteremia in patients who are not at increased risk. Anaerobic blood cultures should be selectively ordered in patients at risk for anaerobic infections.