Utility of blood cultures in community-acquired pneumonia requiring hospitalization: influence of antibiotic treatment before admission

Effect of prior receipt of antibiotics on the pathogen distribution: a retrospective observational cohort study on 27,792 patients

Background

There have been no systematic studies of microbiological differences before and after antibiotics treatment. The aim of this study was to evaluate the effect of prior receipt of antibiotics on the microorganism distribution.

Methods

A retrospective, observational cohort study was conducted in a 3200-bed tertiary, referral, teaching hospital in eastern China. During a 2-year period, all hospitalized patients treated with antimicrobial agents were enrolled in this study. Among 48,692 patients evaluated, the 27,792 (57.1%) who were sampled within 2 days before or after administration of the first dose of antimicrobial agents were included. Distribution of clinical specimens and the microorganism were compared between before and after antibiotic drug treatment groups.

Results

Compared to specimens taken after antibiotics exposure, specimens taken before antibiotics exposure had a higher proportion of blood and urine specimens and a higher culture positive rate (all P < 0.001). Higher percentages of Staphylococcus aureus (9.9% vs. 8.5%, P = 0.041), non-fermenting bacteria (27.7% vs. 19.9%, P < 0.001), and fungi (8.4% vs. 4.0%, P < 0.001) were isolated from the group after antibiotics exposure, while the percentages of Streptococcus spp. (4.8% vs. 2.7%, P < 0.001), Haemophilus influenzae (2.3% vs. 0.8%, P < 0.001), and Moraxella catarrhalis (0.7% vs. 0.1%, P < 0.001) were higher in the group before antibiotics exposure. Further analysis found significant differences of microbes derived from respiratory secretions, blood or urine samples. We found, after antibiotics exposure, the separation rate of non-fermenting bacteria was significantly increased (all P < 0.05), and the separation rate of Candida spp. was higher, with statistical significance in airway secretion and urine samples (both P < 0.05), but the separation rate of Staphylococcus aureus among the three groups was not affected by antibiotics. In addition, the isolation rate of Streptococcus spp. in blood and urine samples decreased significantly (both P < 0.05) after antibiotics exposure. Interestingly, no statistical difference was found for microbes isolated from body fluid specimens between the two groups.

Conclusions

The outcome revealed that antibiotic-insensitive organisms such as non-fermentative bacteria and fungi were more frequently isolated after antibiotics exposure. However, this trend might be specimen dependent and was not obvious in body fluid specimens.

Risk Factors for Myocardial Infarction and Stroke Among Sepsis Survivors: A Competing Risks Analysis

Objectives:

Predictors for post-sepsis myocardial infarction (MI) and stroke are yet to be identified due to the competing risk of death.

Methods:

This study included all hospitalized patients with sepsis from National Health Insurance Research Database of Taiwan between 2000 and 2011. The primary outcome was the first occurrence of MI and stroke requiring hospitalization within 180 days following hospital discharge from the index sepsis episode. The association between predictors and post-sepsis MI and stroke were analyzed using cumulative incidence competing risk model that controlled for the competing risk of death.

Results:

Among 42 316 patients with sepsis, 1012 (2.4%) patients developed MI and stroke within 180 days of hospital discharge. The leading 5 predictors for post-sepsis MI and stroke are prior cerebrovascular diseases (hazard ratio [HR]: 2.02, 95% confidence interval [CI]: 1.74-2.32), intra-abdominal infection (HR: 1.94, 95% CI: 1.71-2.20), previous MI (HR: 1.81, 95% CI: 1.53-2.15), lower respiratory tract infection (HR: 1.62, 95% CI: 1.43-1.85), and septic encephalopathy (HR: 1.61, 95% CI: 1.26-2.06).

Conclusions:

Baseline comorbidities and sources of infection were associated with an increased risk of post-sepsis MI and stroke. The identified risk factors may help physicians select a group of patients with sepsis who may benefit from preventive measures, antiplatelet treatment, and other preventive measures for post-sepsis MI and stroke.

Susceptible period for cardiovascular complications in patients recovering from sepsis

BACKGROUND

Patients are at increased risk of cardiovascular complications while recovering from sepsis. We aimed to study the temporal change and susceptible periods for cardiovascular complications in patients recovering from sepsis by using a national database.

METHODS

In this retrospective population-based cohort study, patients with sepsis were identified from the National Health Insurance Research Database in Taiwan. We estimated the risk of myocardial infarction (MI) and stroke following sepsis by comparing a sepsis cohort to a matched population and hospital control cohort. The primary outcome was first occurrence of MI or stroke requiring admission to hospital during the 180-day period following discharge from hospital after sepsis. To delineate the risk profile over time, we plotted the weekly risk of MI and stroke against time using the Cox proportional hazards model. We determined the susceptible period by fitting the 2 phases of time-dependent risk curves with free-knot splines, which highlights the turning point of the risk of MI and stroke after discharge from the hospital.

RESULTS

We included 42 316 patients with sepsis; stroke developed in 831 of these patients and MI developed in 184 within 180 days of discharge from hospital. Compared with population controls, patients recovering from sepsis had the highest risk for MI or stroke in the first week after discharge (hazard ratio [HR] 4.78, 95% confidence interval [CI] 3.19 to 7.17; risk difference 0.0028, 95% CI 0.0021 to 0.0034), with the risk decreasing rapidly until the 28th day (HR 2.38, 95% CI 1.94 to 2.92; risk difference 0.0045, 95% CI 0.0035 to 0.0056) when the risk stabilized. In a repeated analysis comparing the sepsis cohort with the nonsepsis hospital control cohort, we found an attenuated but still marked elevated risk before day 36 after discharge (HR 1.32, 95% CI 1.15 to 1.52; risk difference 0.0026, 95% CI 0.0013 to 0.0039). The risk of MI or stroke was found to interact with age, with younger patients being associated with a higher risk than older patients (interaction p = 0.0004).

INTERPRETATION

Compared with the general population with similar characteristics, patients recovering from sepsis had a markedly elevated risk of MI or stroke in the first 4 weeks after discharge from hospital. More close monitoring and pharmacologic prevention may be required for these patients at the specified time.

Nationwide Trend of Sepsis: A Comparison Among Octogenarians, Elderly, and Young Adults

OBJECTIVE

We aimed to compare the sepsis incidence, mortality rates, and primary sites of infection among adult, elderly, and octogenarian patients with sepsis.

DESIGN

Population-based cohort study.

SETTING

The entire health insurance claims data of Taiwan, which enrolled 99.8% of the 23 million Taiwanese population.

PATIENTS

Sepsis patients were identified by International Classification of Diseases, 9th Edition, Clinical Modification codes for both infection and organ dysfunction from January 1, 2002, to December 31, 2012. Patients were categorized into three age groups: 1) adults (18-64 yr); 2) elderly (65-84 yr); and 3) oldest old (≥ 85 yr). The 30-day all-cause mortality was verified by a linked national death certificate database.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

From 2002 to 2012, we identified 1,259,578 patients with sepsis, of which 417,328 (33.1%) were adults, 652,618 (51.8%) were elderly, and 189,632 (15.1%) were oldest old. We determined that the incidence of sepsis in the oldest old was 9,414 cases per 100,000 population on 2012, which was 31-fold greater than the adult incidence (303 cases per 100,000 population) and three-fold greater than the elderly incidence (2,908 cases per 100,000 population). Despite the increasing trend in incidence, the mortality decreased by 34% for adults, 24% for elderly, and 22% for oldest old. However, systemic fungal infection was disproportionately increased in oldest old patients (1.76% annual increase) and the elderly patients (1.00% annual increase).

CONCLUSION

The incidence of sepsis is disproportionately increased in elderly and oldest old patients. Despite the increasing trend in incidence, the mortality rate in geriatric patients with sepsis has decreased. However, the increased incidence of fungal infections in the geriatric population warrants further attention.

Recent advances in the microbiological diagnosis of bloodstream infections

Rapid identification (ID) and antimicrobial susceptibility testing (AST) of the causative agent(s) of bloodstream infections (BSIs) are essential for the prompt administration of an effective antimicrobial therapy, which can result in clinical and financial benefits. Immediately after blood sampling, empirical antimicrobial therapy, chosen on clinical and epidemiological data, is administered. When ID and AST results are available, the clinician decides whether to continue or streamline the antimicrobial therapy, based on the results of the in vitro antimicrobial susceptibility profile of the pathogen. The aim of the present study is to review and discuss the experimental data, advantages, and drawbacks of recently developed technological advances of culture-based and molecular methods for the diagnosis of BSI (including mass spectrometry, magnetic resonance, PCR-based methods, direct inoculation methods, and peptide nucleic acid fluorescence in situ hybridization), the understanding of which could provide new perspectives to improve and fasten the diagnosis and treatment of septic patients. Although blood culture remains the gold standard to diagnose BSIs, newly developed methods can significantly shorten the turnaround time of reliable microbial ID and AST, thus substantially improving the diagnostic yield.

A Population-Based Cohort Study on the Drug-Specific Effect of Statins on Sepsis Outcome

BACKGROUND

Whether statin treatment, proved by recent experimental studies to have an antimicrobial activity, exerts a drug- or a class-specific effect in sepsis remains unknown.

METHODS

Short-term mortality in patients with sepsis was analyzed using data from the National Health Insurance Research Database. Use of statins was defined as the cumulative use of a specific statin (atorvastatin, simvastatin, or rosuvastatin) for > 30 days prior to the index sepsis admission. We determined the association between statin and sepsis outcome by multivariate-adjusted Cox models and propensity score (PS)-matched analysis, using a 1:1:1 PS matching technique.

RESULTS

A total of 52,737 patients with sepsis fulfilled the inclusion criteria, of which 1,855 were prescribed atorvastatin, 916 were prescribed simvastatin, and 732 were prescribed rosuvastatin. Compared with nonusers, simvastatin (hazard ratio [HR], 0.72; 95% CI, 0.58-0.90) and atorvastatin (HR, 0.78; 95% CI, 0.68-0.90) were associated with an improved 30-day survival, whereas rosuvastatin was not (HR, 0.87; 95% CI, 0.73-1.04). Using rosuvastatin as the reference, atorvastatin (HR, 0.79; 95% CI, 0.64-0.99) and simvastatin (HR, 0.77; 95% CI, 0.59-0.99) had superior effectiveness in preventing mortality.

CONCLUSIONS

Compatible with in vitro experimental findings, our results suggest that the drug-specific effect of statins on sepsis is not correlated to their lipid-lowering potency.

Adult sepsis - A nationwide study of trends and outcomes in a population of 23 million people

OBJECTIVES

To determine the trend of incidence and outcome of sepsis based on a nationwide administrative database.

METHODS

We analyzed the incidence and mortality of both emergency department treated and hospital treated sepsis from 2002 through 2012 using the entire health insurance claims data of Taiwan. The national health insurance covers 99% of residents in Taiwan. Sepsis patients were identified using a set of validated ICD-9CM codes conforming to the sepsis-3 definition. The 30-day all-cause mortality was verified by linked death certificate database.

RESULTS

During the 11-year study period, a total of 1,259,578 episodes of sepsis was identified. The mean incidence rate was 639 per 100,000 person-years, increasing from 637.8/100,000 persons in 2002 to 772.1/100,000 persons in 2012 (annual increase: 1.9%). The mortality rate, however, has decreased from 27.8% in 2002 to 22.8% in 2012 (annual decrease: 0.45%). The trend of incidence and mortality did not change after standardization by age and gender using 2002 as the reference standard.

CONCLUSION

We showed that the incidence of sepsis has increased while the mortality has decreased in Taiwan. Despite the decreasing trend in sepsis mortality, the total number of sepsis mortality remains increasing due to the rapid increase in sepsis incidence.

Evaluation of a Commercial Multiplex PCR Assay for Detection of Pathogen DNA in Blood from Patients with Suspected Sepsis

The Magicplex Sepsis Real-time Test (MST) is a commercial multiplex PCR that can detect more than 90 different pathogens in blood, with an analysis time of six hours. The aim of the present study was to evaluate this method for the detection of bloodstream infection (BSI). An EDTA whole blood sample for MST was collected together with blood cultures (BC) from patients with suspected sepsis at the Emergency Department of a university hospital. Among 696 study patients, 322 (46%) patients were positive with at least one method; 128 (18%) were BC positive and 268 (38%) were MST positive. Considering BC to be the gold standard, MST had an overall sensitivity of 47%, specificity of 66%, positive predictive value (PPV) of 23%, and a negative predictive value of 87%. Among the MST positive samples with a negative BC, coagulase-negative staphylococci (CoNS) and species that rarely cause community-acquired BSI were frequently noted. However, the quantification cycle (Cq) values of the MST+/BC- results were often high. We thus hypothesized that the performance of the MST test could be improved if the Cq cut-off level was adjusted downwards. With a lower Cq cut-off value, i.e. 6.0 for Staphylococcus species and 9.0 for all other species, the number of MST positive cases decreased to 83 (12%) and the overall sensitivity decreased to 38%. However, the PPV increased to 59% and the specificity increased to 96%, as many MST positive results for CoNS and bacteria that rarely cause community-acquired BSI turned MST negative. In conclusion, our study shows that with a lower Cq cut-off value, the MST will detect less contaminants and findings with unclear relevance, but to the cost of a lower sensitivity. Consequently, we consider that a positive MST results with a Cq value above the adjusted cut-off should be interpreted with caution, as the result might be clinically irrelevant. In a correspondent way, quantitative results could probably be useful in the interpretation of positive results from other molecular assays for the detection of BSI.

Predictive factors of true bacteremia and the clinical utility of blood cultures as a prognostic tool in patients with community-onset pneumonia

Although blood cultures (BCs) are an important component of diagnostic practice for antibiotic management in patients with pneumonia, several studies have questioned whether they should be performed. The objective of this study was to evaluate the predictive factors of bacteremia and the role of BCs in patients with community-onset pneumonia (community-acquired pneumonia and healthcare-associated pneumonia).This study was retrospectively conducted in patients with community-onset pneumonia who were hospitalized at Jeju National University Hospital between January 2012 and December 2014. A true bacteremia (TB) group and a contaminants or negative bacteremia (CNB) group were classified according to the bacterial growth on the BC media and were investigated for the clinical relevance of the BCs.We enrolled 785 patients; the TB group and the CNB group contained 36 patients (4.5%) and 749 (95.4%) patients, respectively. Only 10 patients (1.2%) required a change in antibiotic therapy based on the BC results (3 patients with an escalation, 7 with a de-escalation). There was no significant difference between the community-acquired pneumonia and the healthcare-associated pneumonia groups with regard to the rate of antibiotic change due to the BC results (1.1% vs 1.4%; P = 0.751). Chronic liver disease (odds ratio [OR] 2.973, 95% confidence interval [CI] 1.099-8.037), a confusion, urea, respiratory rate, blood pressure, age ≥65 (CURB-65) score of 4 to 5 points (OR 3.484, 95% CI 1.304-9.307), and Pneumonia Severity Index (PSI) class V (OR 2.405, 95% CI 1.007-5.743) were independently associated with TB. In patients with PSI class V and a CURB-65 score of 4 to 5 points, the TB group tended to show a higher inhospital mortality rate than the CNB group (50.0% vs 29.4%; P = 0.060, 60.0% vs 42.5%; P = 0.480). The areas under the curve for PSI score and CURB-65 score for predicting TB revealed an increased tendency compared with that of C-reactive protein (0.72, 95% CI 0.630-0.809; and 0.72, 95% CI 0.622-0.819 vs 0.629, 95% CI 0.522-0.735, respectively).It seemed reasonable to selectively conduct BC in patients hospitalized with severe community-onset pneumonia based upon its low overall positive rate, its effects on antimicrobial modification, and the associations of TB with the severity indices of pneumonia.

A prospective multicenter evaluation of direct molecular detection of blood stream infection from a clinical perspective

BACKGROUND

Rapid diagnosis and appropriate antimicrobial therapy are of major importance to decrease morbidity and mortality in patients with blood stream infections (BSI). Blood culture, the current gold standard for detecting bacteria in blood, requires at least 24-48 hours and has limited sensitivity if obtained during antibiotic treatment of the patient. The aim of this prospective multicenter study was to clinically evaluate the application of a commercial universal 16S/18S rDNA PCR, SepsiTest™ (PCR-ST), directly on whole blood.

METHODS

In total 236 samples from 166 patients with suspected sepsis were included in the study. PCR-ST results were compared to blood culture, the current gold standard for detecting BSI. Because blood cultures can give false-negative results, we performed an additional analysis to interpret the likelihood of bloodstream infection by using an evaluation based on clinical diagnosis, other diagnostic tests and laboratory parameters.

RESULTS

Clinical interpretation of results defined the detected organism to be contaminants in 22 of 43 positive blood cultures (51.2 %) and 21 of 47 positive PCR-ST results (44.7 %). Excluding these contaminants resulted in an overall sensitivity and specificity of the PCR-ST of 66.7 and 94.4 % respectively. Of the 36 clinically relevant samples, 11 BSI were detected with both techniques, 15 BSI were detected with PCR-ST only and 10 with blood culture only. Therefore, in this study, SepsiTest™ detected an additional 71 % BSI compared to blood culture alone.

CONCLUSIONS

More clinically relevant BSI were diagnosed by molecular detection, which might influence patient treatment. An improved SepsiTest™ assay suited for routine use can have additional value to blood culture in diagnosing bacteremia in septic patients.

Melting Temperature Mapping Method: A Novel Method for Rapid Identification of Unknown Pathogenic Microorganisms within Three Hours of Sample Collection

Acquiring the earliest possible identification of pathogenic microorganisms is critical for selecting the appropriate antimicrobial therapy in infected patients. We herein report the novel “melting temperature (Tm) mapping method” for rapidly identifying the dominant bacteria in a clinical sample from sterile sites. Employing only seven primer sets, more than 100 bacterial species can be identified. In particular, using the Difference Value, it is possible to identify samples suitable for Tm mapping identification. Moreover, this method can be used to rapidly diagnose the absence of bacteria in clinical samples. We tested the Tm mapping method using 200 whole blood samples obtained from patients with suspected sepsis, 85% (171/200) of which matched the culture results based on the detection level. A total of 130 samples were negative according to the Tm mapping method, 98% (128/130) of which were also negative based on the culture method. Meanwhile, 70 samples were positive according to the Tm mapping method, and of the 59 suitable for identification, 100% (59/59) exhibited a “match” or “broad match” with the culture or sequencing results. These findings were obtained within three hours of whole blood collection. The Tm mapping method is therefore useful for identifying infectious diseases requiring prompt treatment.

When practice and policy conflict: blood cultures in community-acquired pneumonia

Optimal evidence-based management of patients with uncomplicated community-acquired pneumonia in the emergency department (ED) setting remains a topic of discussion. This discussion was recently revitalized by a 2014 study published in JAMA Internal Medicine by Makam et al showing an increase in the use of blood cultures for patients with community-acquired pneumonia during ED visits from 29.4% of patients in 2002 to 51.1% in 2010. As the authors acknowledge, one of the most likely explanations could be the former pneumonia core measures required by the Centers for Medicaid & Medicare Services and the Joint Commission, potentially encouraging both ED and inpatient providers to reflexively order cultures. As these measures were the subject of fierce debate in the emergency medicine literature almost a decade ago, with recent policy changes affecting practicing clinicians, we aimed to briefly revisit the developments and concerning guidelines and discuss some important potentials for research in this setting.

Added value of multi-pathogen probe-based real-time PCR SeptiFast in the rapid diagnosis of bloodstream infections in patients with bacteraemia

The commercial multi-pathogen probe-based real-time PCR SeptiFast (SF) was evaluated as a rapid and complementing tool for the microbiological diagnosis of bloodstream infections (BSIs) in a series of 138 matched blood samples from 65 patients with bacteraemia, hospitalized in an intensive care unit, when antibiotics had already been administered. SF was positive in 32.6 % of the samples, whereas blood culture (BC) was positive in 21.7 % (P < 0.05). SF identified more pathogens (11 versus 5; specificity, 90.7 %) and reduced the time of aetiological diagnosis, with a mean of 16.3 versus 55.4 h needed for BC (P < 0.05). SF enabled appropriate pathogen-oriented therapy in 72 % (36/50) of the BSI group of patients on the basis of epidemiological data. According to our data, the use of SF provided important added value to BC, in terms of earlier aetiological diagnosis of BSIs, enabling pathogen-oriented therapy in patients receiving empirical antibiotic treatment.

Can we predict which patients with community-acquired pneumonia are likely to have positive blood cultures?

BACKGROUND

Blood cultures (BC) are commonly ordered during the initial assessment of patients with community-acquired pneumonia (CAP), yet their yield remains low. Selective use of BC would allow the opportunity to save healthcare resources and avoid patient discomfort. The study was to determine what demographic and clinical factors predict a greater likelihood of a positive blood culture result in patients diagnosed with CAP.

METHODS

A structured retrospective systematic chart audit was performed to compare relevant demographic and clinical details of patients admitted with CAP, in whom blood culture results were positive, with those of age, sex, and date-matched control patients in whom blood culture results were negative.

RESULTS

On univariate analysis, eight variables were associated with a positive BC result. After logistic regression analysis, however, the only variables statistically significantly associated with a positive BC were WBC less than 4.5 × 10(9)/L [likelihood ratio (LR): 7.75, 95% CI=2.89-30.39], creatinine >106 μmol/L (LR: 3.15, 95%CI=1.71-5.80), serum glucose<6.1 mmol/L (LR: 2.46, 95%CI=1.14-5.32), and temperature > 38 °C (LR: 2.25, 95% CI =1.21-4.20). A patient with all of these variables had a LR of having a positive BC of 135.53 (95% CI=25.28-726.8) compared to patients with none of these variables.

CONCLUSIONS

Certain clinical variables in patients with CAP admitted to hospitals do appear to be associated with a higher probability of a positive yield of BC, with combinations of these variables increasing this likelihood. We have identified a subgroup of CAP patients in whom blood cultures are more likely to be useful.

Developments for improved diagnosis of bacterial bloodstream infections

Bloodstream infections (BSIs) are associated with high mortality and increased healthcare costs. Optimal management of BSI depends on several factors including recognition of the disease, laboratory tests and treatment. Rapid and accurate identification of the etiologic agent is crucial to be able to initiate pathogen specific antibiotic therapy and decrease mortality rates. Furthermore, appropriate treatment might slow down the emergence of antibiotic resistant strains. Culture-based methods are still considered to be the "gold standard" for the detection and identification of pathogens causing BSI. Positive blood cultures are used for Gram-staining. Subsequently, positive blood culture material is subcultured on solid media, and (semi-automated) biochemical testing is performed for species identification. Finally, a complete antibiotic susceptibility profile can be provided based on cultured colonies, which allows the start of pathogen-tailored antibiotic therapy. This conventional workflow is extremely time-consuming and can take up to several days. Furthermore, fastidious and slow-growing microorganisms, as well as antibiotic pre-treated samples can lead to false-negative results. The main aim of this review is to present different strategies to improve the conventional laboratory diagnostic steps for BSI. These approaches include protein-based (MALDI-TOF mass spectrometry) and nucleic acid-based (polymerase chain reaction [PCR]) identification from subculture, blood cultures, and whole blood to decrease time to results. Pathogen enrichment and DNA isolation methods, to enable optimal pathogen DNA recovery from whole blood, are described. In addition, the use of biomarkers as patient pre-selection tools for molecular assays are discussed.

Monitoring infection: from blood culture to polymerase chain reaction (PCR)

In patients with sepsis, diagnosis of blood stream infection (BSI) is a key concern to the therapist. Direct verification of pathogens in the blood stream executed by blood cultures (BC) still is regarded as the gold standard up to date. The quickest possible initiation of an appropriate antimicrobial therapy is a cornerstone of an effective therapy. Moreover, in this view BC can also serve to identify antimicrobial agents to target the pathogen. However, when employing BC the time needed until microbiological results are available ranges from 24 up to 72 h. Moreover, infections caused by multiple pathogens often remain undetected and concurrent antibiotic therapy may lower the overall sensitivity. Alternative pathogen characterization can be performed by polymerase chain reaction (PCR) based amplification methods. Results using PCR can be obtained within 6-8 h. Therefore, the time delay until an appropriate therapy can be reduced enormously. Moreover, these methods have the potential to enhance the sensitivity in the diagnosis of blood stream infections. Therefore, PCR based methods might be a valuable adjunct to present procedures of diagnosing bacteraemia.

Quantitative data from the SeptiFast real-time PCR is associated with disease severity in patients with sepsis

Background

The commercial test, SeptiFast, is designed to detect DNA from bacterial and fungal pathogens in whole blood. The method has been found to be specific with a high rule-in value for the early detection of septic patients. The software automatically provides information about the identified pathogen, without quantification of the pathogen. However, it is possible to manually derive Crossing point (Cp) values, i.e. the PCR cycle at which DNA is significantly amplified. The aim of this study was to find out whether Cp values correlate to disease severity.

Methods

We used a study cohort of patients with positive results from SeptiFast tests for bacteria from a recent study which included patients with suspected sepsis in the Emergency department. Cp values were compared with disease severity, classified as severe sepsis/septic shock or non-severe sepsis, according to the criteria of the American College of Chest Physicians/Society of Critical Care Medicine.

Results

Ninety-four patients were included. The prevalence of severe sepsis/septic shock in the study was 29%. SeptiFast positive tests from patients with severe sepsis/septic shock had significantly lower Cp values compared with those from patients with non-severe sepsis, median 16.9 (range: 7.3 - 24.3) versus 20.9 (range: 8.5 - 25.0), p < 0.001. Positive predictive values from the SeptiFast test for identifying severe sepsis/septic shock were 34% at Cp cut-off <25.0, 35% at Cp cut-off <22.5, 50% at Cp cut-off <20.0, and 73% at Cp cut-off <17.5. Patients with a positive Septifast test with a Cp value <17.5 had significantly more severe sepsis/septic shock (73% versus 15%, p < 0.001), were more often admitted to the Intensive Care Unit (23% versus 4%, p = 0.016), had positive blood culture (BC) more frequently (100% versus 32%, p < 0.001) and had longer hospital stays (median 19.5 [range: 4 - 78] days versus 5 [range: 0 - 75] days, p < 0.001) compared with those with a Cp value >17.5.

Conclusions

Our results suggest that introducing quantitative data to the SeptiFast test could be of value in assessing sepsis severity. Moreover, such data might also be useful in predicting a positive BC result.

Pre-analytical sample treatment and DNA extraction protocols for the detection of bacterial pathogens from whole blood

Molecular diagnostics is an increasing popular approach for the direct detection and identification of pathogenic bacteria in clinical samples. Conventional culture techniques are time-consuming and therefore causing a delay in the diagnosis of the patient. Alternative techniques based on nucleic acid amplification offer a shorter turn-around-time and the ability to identify fastidious and non-cultivable organisms. However, molecular detection of bacteria in blood, by for example PCR, RT-PCR, or sequencing of the 16S rDNA genes is often complicated by the presence of PCR-inhibitory compounds. Here we describe several different methods for the extraction of bacterial DNA from whole blood samples. The methods differ regarding costs, hands-on time as well as regarding sensitivity. In combination with a model PCR the detection limits that can be reached using the different methods range from 1,000 to 50 cfu/ml.

Diagnostic performance of a multiple real-time PCR assay in patients with suspected sepsis hospitalized in an internal medicine ward

Early identification of causative pathogen in sepsis patients is pivotal to improve clinical outcome. SeptiFast (SF), a commercially available system for molecular diagnosis of sepsis based on PCR, has been mostly used in patients hospitalized in hematology and intensive care units. We evaluated the diagnostic accuracy and clinical usefulness of SF, compared to blood culture (BC), in 391 patients with suspected sepsis, hospitalized in a department of internal medicine. A causative pathogen was identified in 85 patients (22%). Sixty pathogens were detected by SF and 57 by BC. No significant differences were found between the two methods in the rates of pathogen detection (P = 0.74), even after excluding 9 pathogens which were isolated by BC and were not included in the SF master list (P = 0.096). The combination of SF and BC significantly improved the diagnostic yield in comparison to BC alone (P < 0.001). Compared to BC, SF showed a significantly lower contamination rate (0 versus 19 cases; P < 0.001) with a higher specificity for pathogen identification (1.00, 95% confidence interval [CI] of 0.99 to 1.00, versus 0.94, 95% CI of 0.90 to 0.96; P = 0.005) and a higher positive predictive value (1.00, 95% CI of 1.00 to 0.92%, versus 0.75, 95% CI of 0.63 to 0.83; P = 0.005). In the subgroup of patients (n = 191) who had been receiving antibiotic treatment for ≥24 h, SF identified more pathogens (16 versus 6; P = 0.049) compared to BC. These results suggest that, in patients with suspected sepsis, hospitalized in an internal medicine ward, SF could be a highly valuable adjunct to conventional BC, particularly in patients under antibiotic treatment.

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.

Conventional and molecular techniques for the early diagnosis of bacteraemia

Bloodstream infections account for 30-40% of all cases of severe sepsis and septic shock, and are major causes of morbidity and mortality. Diagnosis of bloodstream infections must be performed promptly so that adequate antimicrobial therapy can be started and patient outcome improved. An ideal diagnostic technology would identify the infecting organism(s) and their determinants of antibiotic resistance, in a timely manner, so that appropriate pathogen-driven therapy could begin promptly. Unfortunately, despite the essential information it provides, blood culture, the gold standard, largely fails in this purpose because time is lost waiting for bacterial or fungal growth. Several efforts have been made to optimise the performance of blood culture, such as the development of technologies to obtain rapid detection of microorganism(s) directly in blood samples or in a positive blood culture. The ideal molecular method would analyse a patient's blood sample and provide all the information needed to immediately direct optimal antimicrobial therapy for bacterial or fungal infections. Furthermore, it would provide data to assess the effectiveness of the therapy by measuring the clearance of microbial nucleic acids from the blood over time. None of the currently available molecular methods is sufficiently rapid, accurate or informative to achieve this. This review examines the principal advantages and limitations of some traditional and molecular methods commercially available to help the microbiologist and the clinician in the management of bloodstream infections.

High and increasing Oxa-51 DNA load predict mortality in Acinetobacter baumannii bacteremia: implication for pathogenesis and evaluation of therapy

Background

While quantification of viral loads has been successfully employed in clinical medicine and has provided valuable insights and useful markers for several viral diseases, the potential of measuring bacterial DNA load to predict outcome or monitor therapeutic responses remains largely unexplored. We tested this possibility by investigating bacterial loads in Acinetobacter baumannii bacteremia, a rapidly increasing nosocomial infection characterized by high mortality, drug resistance, multiple and complicated risk factors, all of which urged the need of good markers to evaluate therapeutics.

Methods and Findings

We established a quantitative real-time PCR assay based on an A. baumannii-specific gene, Oxa-51, and conducted a prospective study to examine A. baumannii loads in 318 sequential blood samples from 51 adults patients (17 survivors, 34 nonsurvivors) with culture-proven A. baumannii bacteremia in the intensive care units. Oxa-51 DNA loads were significantly higher in the nonsurvivors than survivors on day 1, 2 and 3 (P = 0.03, 0.001 and 0.006, respectively). Compared with survivors, nonsurvivors had higher maximum Oxa-51 DNA load and a trend of increase from day 0 to day 3 (P<0.001), which together with Pitt bacteremia score were independent predictors for mortality by multivariate analysis (P = 0.014 and 0.016, for maximum Oxa-51 DNA and change of Oxa-51 DNA, respectively). Kaplan-Meier analysis revealed significantly different survival curves in patients with different maximum Oxa-51 DNA and change of Oxa-51 DNA from day 0 to day 3.

Conclusions

High Oxa-51 DNA load and its initial increase could predict mortality. Moreover, monitoring Oxa-51 DNA load in blood may provide direct parameters for evaluating new regimens against A. baumannii in future clinical studies.

Study of human metapneumovirus-associated lower respiratory tract infections in Egyptian adults

There is a deficiency in the data concerning the role of hMPV in lower respiratory tract infections in adults, and until now there has been no data available regarding the prevalence of hMPV in adults in our region. In the present study the association of hMPV with varieties of lower respiratory tract disorders in immunocompetent adult patients, either alone or with bacterial pathogens, has been highlighted. Eighty-eight patients were included in the study. They included 46 males and 42 females with an age range of 38-65 years. Patients presented with lower respiratory tract infections associated with acute exacerbation of asthma (67%), pneumonia (17%), and acute exacerbation of chronic obstructive lung diseases. Sputum and nasopharyngeal samples were obtained from the patients and subjected to a full microbiological study. In addition, detection of hMPV was performed by nested reverse transcriptase polymerase chain reaction. The pathogens isolated were Streptococcus pneumoniae 46.6%, Staphylococci aureus 35.2%, and human metapneumovirus 13.6%. Influenza virus and rhinovirus were each isolated from 4.5% of patients. Human metapneumovirus was associated with S. pneumoniae in 4.5% in studied patients, while in 9.1% it was the only pathogen found in those patients. The commonest clinical condition with significant association with human metapneumovirus was pneumonia. The clinical and laboratory studies demonstrated an association between lower respiratory tract infections in adults and hMPV either as sole pathogen or in association with Streptococcus pneumoniae. It was a common pathogen in community-acquired pneumonia.

Procalcitonin levels predict bacteremia in patients with community-acquired pneumonia: a prospective cohort trial

BACKGROUND

Guidelines recommend blood culture sampling from hospitalized patients with suspected community-acquired pneumonia (CAP). However, the yield of true-positive results is low. We investigated the benefit of procalcitonin (PCT) on hospital admission to predict blood culture positivity in CAP.

METHODS

This was a prospective cohort study with a derivation and validation set including 925 patients with CAP who underwent blood culture sampling on hospital admission.

RESULTS

A total of 73 (7.9%) patients had true bacteremia (43 of 463 in the derivation cohort, 30 of 462 in the validation cohort). The area under the receiver operating characteristics curve of PCT in the derivation and validation cohorts was similar (derivation cohort, 0.83; 95% CI, 0.78-0.89; validation cohort, 0.79; 95% CI, 0.72-0.88). Overall, PCT was a significantly better predictor for blood culture positivity than WBC count, C-reactive protein, and other clinical parameters. In multivariate regression analysis, only antibiotic pretreatment (adjusted odds ratio, 0.25; P < .05) and PCT serum levels (adjusted odds ratio, 3.72; P < .001) were independent predictors. Overall, a PCT cutoff of 0.1 microg/L would enable reduction of the total number of blood cultures by 12.6% and still identify 99% of the positive blood cultures. Similarly, 0.25 microg/L and 0.5 microg/L cutoffs would enable reduction of blood cultures by 37% and 52%, respectively, and still identify 96% and 88%, respectively, of positive blood cultures.

CONCLUSIONS

Initial PCT level accurately predicted blood culture positivity in patients with CAP. PCT measurement has the potential to reduce the number of drawn blood cultures in the emergency department and to implement a more targeted allocation of limited health-care resources.

Clinical policy: critical issues in the management of adult patients presenting to the emergency department with community-acquired pneumonia

This clinical policy from the American College of Emergency Physicians focuses on critical issues concerning the management of adult patients presenting to the emergency department (ED)with community-acquired pneumonia. It is an update of the 2001 clinical policy for the management and risk stratification of adult patients presenting to the ED with community-acquired pneumonia. A subcommittee reviewed the current literature to derive evidence-based recommendations to help answer the following questions: (1) Are routine blood cultures indicated in patients admitted with community-acquired pneumonia? (2) In adult patients with community-acquired pneumonia without severe sepsis, is there a benefit in mortality or morbidity from the administration of antibiotics within aspecific time course? The evidence was graded and recommendations were given based on the strength of evidence.

Bench-to-bedside review: the promise of rapid infection diagnosis during sepsis using polymerase chain reaction-based pathogen detection

Early infection diagnosis as the cause of a patient's systemic inflammatory syndrome is an important facet of sepsis care bundles aimed at saving lives. Microbiological culture provides the main route for infection diagnosis but by its nature cannot provide time-critical results that can impact on early management. Consequently, broad-spectrum and high-potency antibiotics are essential during the immediate management of suspected sepsis in critical care but are associated with the development of drug-resistant organisms and superinfections. Established molecular laboratory techniques based on polymerase chain reaction (PCR) technology can detect pathogen DNA rapidly and have been developed for translation into a clinical diagnostic setting. In the setting of sepsis in critical care, emerging commercial systems are now available for the analysis of whole blood within hours, with the presumed aim of adoption into the current care bundles. In this review, we consider the importance of early infection diagnosis in sepsis, how this is limited by culture approaches and how the emerging PCR methods are showing promise in early clinical observational studies. The strengths and weaknesses of culture and PCR pathogen detection in whole-blood samples will be highlighted and recommendations made for urgent appropriately powered diagnostic validation studies in advance of clinical effectiveness trials before these emerging PCR pathogen detection techniques can be considered for adoption in clinical practice.

Bench-to-bedside review: the promise of rapid infection diagnosis during sepsis using polymerase chain reaction-based pathogen detection

Early infection diagnosis as the cause of a patient's systemic inflammatory syndrome is an important facet of sepsis care bundles aimed at saving lives. Microbiological culture provides the main route for infection diagnosis but by its nature cannot provide time-critical results that can impact on early management. Consequently, broad-spectrum and high-potency antibiotics are essential during the immediate management of suspected sepsis in critical care but are associated with the development of drug-resistant organisms and superinfections. Established molecular laboratory techniques based on polymerase chain reaction (PCR) technology can detect pathogen DNA rapidly and have been developed for translation into a clinical diagnostic setting. In the setting of sepsis in critical care, emerging commercial systems are now available for the analysis of whole blood within hours, with the presumed aim of adoption into the current care bundles. In this review, we consider the importance of early infection diagnosis in sepsis, how this is limited by culture approaches and how the emerging PCR methods are showing promise in early clinical observational studies. The strengths and weaknesses of culture and PCR pathogen detection in whole-blood samples will be highlighted and recommendations made for urgent appropriately powered diagnostic validation studies in advance of clinical effectiveness trials before these emerging PCR pathogen detection techniques can be considered for adoption in clinical practice.

High levels of mecA DNA detected by a quantitative real-time PCR assay are associated with mortality in patients with methicillin-resistant Staphylococcus aureus bacteremia

Persistent methicillin-resistant Staphylococcus aureus (MRSA) bacteremia is known to be a poor prognostic factor. While several PCR assays for the detection of MRSA in various clinical samples were recently reported, the possibility that a quantitative PCR assay could be used to quantify and monitor MRSA bacteremia has not been explored. In this study, we established a quantitative real-time PCR assay for the mecA gene using known copy numbers of a plasmid containing mecA DNA as a standard and the previously described mecA-specific primers and probe (P. Francois et al., J. Clin. Microbiol. 41:254-260, 2003). We employed this assay to examine 250 sequential whole-blood samples from 20 adult patients, including 13 survivors and 7 nonsurvivors, with culture-proven MRSA bacteremia at the intensive care units of National Taiwan University Hospital between 1 July 2006 and 31 January 2007. The levels of mecA DNA in the nonsurvivors were significantly higher than those in the survivors during the three periods of bacteremia examined (days 0 to 2, 3 to 5, and 6 to 8) (P = 0.003 by two-tailed Mann-Whitney U test). Moreover, the nonsurvivors had higher mecA DNA levels than the survivors after 3 days and 7 days of anti-MRSA therapy (medians for nonsurvivors and survivors at 3 days, 5.86 and 4.30 log copies/ml, respectively; medians for nonsurvivors and survivors at 7 days, 5.21 and 4.36 log copies/ml, respectively; P = 0.02 and P = 0.04, respectively, by two-tailed Mann-Whitney U test). Together, these findings suggest that the level of mecA DNA in blood could potentially be used to monitor MRSA bacteremia and evaluate responses to therapy.

Blood cultures for community-acquired pneumonia: are they worthy of two quality measures? A systematic review

BACKGROUND

Obtaining blood cultures (BCs) for patients hospitalized with community-acquired-pneumonia (CAP) has been recommended by experts and used as a measure of quality of care. However, BCs are infrequently positive in these patients and their effect on clinical management has been questioned.

PURPOSE

We performed a systematic review of the literature to determine the impact of BCs on clinical management in CAP requiring hospitalization and thus its appropriateness as a quality measure.

DATA SOURCES

We searched MEDLINE, MEDLINE In-Process, and the Cochrane databases for English-language studies that reported the effect of BCs on management of adults hospitalized with CAP. We also searched the reference lists of included studies and background articles and asked experts to review our list for completeness.

STUDY SELECTION

Studies were chosen if they included adults admitted to the hospital with CAP, BCs were obtained at admission, and BC-directed management changes were reported.

DATA EXTRACTION

We abstracted study design, BC positivity, and frequency of BC-directed management changes.

DATA SYNTHESIS

Fifteen studies, all with observational cohort design, were identified and reviewed. Two included only patients with BCs positive for pneumococcus, yielding 13 studies for the primary analysis. BCs were true-positive in 0% to 14% of cases. They led to antibiotic narrowing in 0% to 3% of patients and to antibiotic broadening ultimately associated with a resistant organism in 0% to 1% of patients.

CONCLUSIONS

BCs have very limited utility in immunocompetent patients hospitalized with CAP. Pneumonia quality measures that include BCs should be reassessed.

Selective use of blood cultures in emergency department pneumonia patients

Our objectives were to identify factors associated with positive blood cultures and to evaluate blood culture use in the management of hospitalized pneumonia patients to limit their use. A retrospective chart review was conducted at a community teaching hospital. Emergency Department patients with an admission diagnosis of pneumonia during calendar years 2001-2002 were included. Patients younger than age 18 years and those with a non-pneumonia discharge diagnosis were excluded. Of 684 eligible patients, 23 (3.4%) had true positive blood cultures. All organisms were sensitive to empiric antibiotics. Three risk factors were associated with positive blood cultures: oxygen saturation < 90%, serum sodium < 130 and respiratory rate > 30 breaths/min. No patient had antibiotic coverage broadened based on blood culture results. Positive blood culture rates were low and did not affect the clinical management of pneumonia patients. We recommend eliminating blood cultures in community-acquired pneumonia (CAP) patients, but obtaining blood cultures in patients at risk for multi-drug resistant pathogens, such as health-care-associated pneumonia (HCAP) patients.

100 years of respiratory medicine: pneumonia

In this review, we aim to lead the readers through the historical highlights of pathophysiological concepts and treatment of pneumonia. Understanding the aetiology, the risk factors and the pathophysiology influenced our management approaches to pneumonia. Pneumonia is still associated with significant morbidity and mortality, presents in a variety of healthcare settings and imposes a considerable cost to healthcare services. Guidelines have been issued by international and national scientific societies in order to spread the scientific knowledge on this important disease and to improve its management.

Prospective evaluation of the treatment and outcome of community-acquired pneumonia according to the Pneumonia Severity Index in VHA hospitals

The objective of the study were to determine if nationally recognized community-acquired pneumonia (CAP) guidelines (specific to antibiotic therapy) were being followed and to identify outcomes of treatment in hospitals that are VHA members. This was a prospective study using a medication use evaluation in an inpatient setting conducted in 46 institutions in the United States during the 1998-1999 CAP season. The subjects were 875 adult patients (> or =18 years of age) admitted from the emergency department or ambulatory care setting with a chest X-ray-confirmed diagnosis of CAP. Treatment pathways were in place in 58.7% (27/46) of institutions, with 18.3% of patients treated according to pathways. Twenty-seven percent of patients were PSI class I or II. A pathogen (blood or sputum) was identified in <10% of patients. The first dose of antibiotic was administered to patients 65% of the time in the emergency department. Antibiotic therapy in 592 of the 694 admitted to a general medical unit (mortality rate, 3%) complied with 1998 Infectious Diseases Society of America (IDSA) guidelines compared with 26 of the 65 admitted to the intensive care unit (ICU) (mortality rate, 4.6%). In patients admitted to other nongeneral medical, non-ICU areas, IDSA guidelines were followed in 95% of the patients. Mean length of stay and mortality for PSI classes I-V were 4.5, 4.6, 6.9, 6.2, and 7.1 days, respectively, and 0%, 0.7%, 1.1%, 2.5%, and 10.5%, respectively. Antibiotic therapy was modified in 733 of 875 patients. Approximately 90% of patients were eligible for conversion to oral (per os) therapy before discontinuation of parenteral (intravenous) antibiotics (mean time to eligibility, 1.8 days of parenteral antibiotics), with conversion in 65% (mean time to conversion to oral therapy, 4.6 days). Resolution of CAP occurred in 92% of patients; deterioration was more common in PSI class IV and V patients. In conclusion, inhospital mortality rates for all PSI classes were similar to those found in other recently conducted studies despite limited adherence to pathways. Greater use of treatment guidelines for patients admitted to the ICU and awareness of the intravenous to per os antibiotic conversion process are suggested.

Blood cultures in ambulatory outpatients

Background

Blood cultures are a gold standard specific test for diagnosing many infections. However, the low yield may limit their usefulness, particularly in low-risk populations. This study was conducted to assess the utility of blood cultures drawn from ambulatory outpatients.

Methods

Blood cultures drawn at community-based collection sites in the Calgary Health Region (population 1 million) in 2001 and 2002 were included in this study. These patients were analyzed by linkages to acute care health care databases for utilization of acute care facilities within 2 weeks of blood culture draw.

Results

3102 sets of cultures were drawn from 1732 ambulatory outpatients (annual rate = 89.4 per 100,000 population). Significant isolates were identified from 73 (2.4%) sets of cultures from 51 patients, including Escherichia coli in 18 (35%) and seven (14%) each of Staphylococcus aureus and Streptococcus pneumoniae. Compared to patients with negative cultures, those with positive cultures were older (mean 49.6 vs. 40.1 years, p < 0.01), and more likely to subsequently receive care at a regional emergency department, outpatient antibiotic clinic, or hospital (35/51 vs. 296/1681, p < 0.0001). Of the 331 (19%) patients who received acute care treatment, those with positive cultures presented sooner after community culture draw (median 2 vs. 3 days, p < 0.01) and had longer median treatment duration (6 vs. 2 days, p < 0.01).

Conclusion

Blood cultures drawn in outpatient settings are uncommonly positive, but may define patients for increased intensity of therapy. Strategies to reduce utilization without excluding patients with positive cultures need to be developed for this patient population.

New developments in the diagnosis of bloodstream infections

New techniques have emerged for the detection of bacteria in blood, because the blood culture as gold standard is slow and insufficiently sensitive when the patient has previously received antibiotics or in the presence of fastidious organisms. DNA-based techniques, hybridisation probes, and PCR-based detection or protein-based detection by mass spectroscopy are aimed at rapid identification of bacteria and provide results within 2 h after the first signal of growth in conventional blood cultures. Also, detection of microorganisms directly in blood by pathogen-specific or broad-range PCR assays (eubacterial or panfungal) shows promising results. Interpretation is complex, however, because of detection of DNA rather than living pathogens, the risk of interfering contamination, the presence of background DNA in blood, and the lack of a gold standard. As these techniques are emerging, clinical value and cost-effectiveness have to be assessed. Nevertheless, molecular assays are expected eventually to replace the current conventional microbiological techniques for detection of bloodstream infections.

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.

Community-acquired pneumonia

This seminar reviews important features and management issues of community-acquired pneumonia (CAP) that are especially relevant to immunocompetent adults in light of new information about cause, clinical course, diagnostic testing, treatment, and prevention. Streptococcus pneumoniae remains the most important pathogen; however, emerging resistance of this organism to antimicrobial agents has affected empirical treatment of CAP. Atypical pathogens have been quite commonly identified in several prospective studies. The clinical significance of these pathogens (with the exception of Legionella spp) is not clear, partly because of the lack of rapid, standardised tests. Diagnostic evaluation of CAP is important for appropriate assessment of severity of illness and for establishment of the causative agent in the disease. Until better rapid diagnostic methods are developed, most patients will be treated empirically. Antimicrobials continue to be the mainstay of treatment, and decisions about specific agents are guided by several considerations that include spectrum of activity, and pharmacokinetic and pharmacodynamic principles. Several factors have been shown to be associated with a beneficial clinical outcome in patients with CAP. These factors include administration of antimicrobials in a timely manner, choice of antibiotic therapy, and the use of a critical pneumonia pathway. The appropriate use of vaccines against pneumococcal disease and influenza should be encouraged. Several guidelines for management of CAP have recently been published, the recommendations of which are reviewed.

Viral lower respiratory tract infection in the elderly: a prospective in-hospital study

The objective of this prospective study was to evaluate the clinical and laboratory parameters distinguishing viral from nonviral lower respiratory tract infection in elderly patients and to determine the yield of virological diagnostics in elderly patients with lower respiratory tract infection. The study was conducted in a 184-bed geriatric department in a university hospital during 4 winter months. All consecutive elderly persons admitted with a lower respiratory tract infection were included in the study. Clinical and laboratory parameters, a nasopharyngeal swab, and serological results for respiratory viruses were obtained for all participants. Available blood and sputum cultures were analysed. A total of 165 elderly persons (mean age, 82+/-6.8 years) were hospitalised with a lower respiratory tract infection. Familial flu-like illness (OR, 4.25; 95%CI, 1.4-13), better functionality (OR, 4; 95%CI, 1.3-14.15), and leucocyte count <10(10)/l (OR, 3; 95%CI, 1.3-7.1) were predictive for viral lower respiratory tract infection. Sixty (36.5%) definite diagnoses (positive blood culture, viral culture, or serological test) and seven (4.2%) probable diagnoses (positive sputum culture) were obtained. An early diagnosis (within 72 h) was possible in 38 (23%) and a late diagnosis in 29 (17.6%) participants. A nasopharyngeal swab contributed in 60.5% of the cases to an early diagnosis. Viral culture identified half (22/43) of the lower respiratory tract infections caused by influenza but only one of six lower respiratory tract infections caused by respiratory syncytial virus. In conclusion, a history of flu-like illness in family members and a total leucocyte count within normal limits makes a viral cause more likely in elderly people hospitalised with a lower respiratory tract infection during winter. Viral culture and rapid antigen detection are insensitive in elderly patients hospitalised with a lower respiratory tract infection.

The contribution of blood cultures to the clinical management of adult patients admitted to the hospital with community-acquired pneumonia: a prospective observational study

STUDY OBJECTIVE

To assess the clinical usefulness of blood cultures (BCs) in the management of patients hospitalized with community-acquired pneumonia (CAP).

DESIGN

A prospective, observational study to investigate the contribution of BCs to the management and outcomes of adult patients presenting with CAP.

SETTING

Nineteen Canadian hospitals.

PATIENTS

Adults admitted to the hospital with CAP between January 1, 1998, and July 31, 1998.

INTERVENTIONS

The courses of therapy in patients for whom BC results yielded organisms considered to be clinically significant were analyzed to determine whether the BCs had contributed to management or outcome.

MEASUREMENTS AND RESULTS

Forty-three of 760 patients had significantly positive BC results. Patients with CAP who had BCs performed had a 1.97% chance (15 of 760 patients) of having a change of therapy directed by BC results. Patients in whom BCs yielded positive results had a 34.8% chance (15 of 43 patients) of having a change in therapy determined by BC results, and had a 58.1% chance (25 of 43 patients) of having a course of therapy contraindicated by BC results. Severity of illness, as measured by the pneumonia severity index, correlated poorly with the yield of BCs. BC results were positive in 8.0% of patients in risk classes I and II, 6.2% of patients in risk class III, 4.6% of patients in risk class IV, and 5.2% of patients in risk class V.

CONCLUSION

BCs have limited usefulness in the routine management of patients admitted to the hospital with uncomplicated CAP.