scholarly journals Classical Microbiological Diagnostics of Bacteremia: Are the Negative Results Really Negative? What is the Laboratory Result Telling Us About the “Gold Standard”?

2020 ◽  
Vol 8 (3) ◽  
pp. 346
Author(s):  
Tomasz Źródłowski ◽  
Joanna Sobońska ◽  
Dominika Salamon ◽  
Isabel M. McFarlane ◽  
Mirosław Ziętkiewicz ◽  
...  
Keyword(s):  
Blood Culture ◽  
Healthy Volunteers ◽  
Culture Method ◽  
Blood Cultures ◽  
Gram Stain ◽  
Blood Samples ◽  
Negative Results ◽  
Gram Staining ◽  
Study Results

Standard blood cultures require at least 24–120 h to be reported as preliminary positive. The objective of this study was to compare the reliability of Gram staining and fluorescent in-situ hybridization (FISH) for detecting bacteria in otherwise negative blood culture bottles. Ninety-six sets were taken from patients with a diagnosis of sepsis. Six incomplete blood culture sets and eight blood cultures sets demonstrating positive growth were excluded. We performed Gram stain and FISH on 82 sets taken from post-operative septic patients: 82 negative aerobic blood cultures, 82 anaerobic blood cultures, and 82 blood samples, as well as 57 blood samples taken from healthy volunteers. From the eighty-two blood sets analyzed from the septic patients, Gram stain visualized bacteria in 62.2% of blood samples, 35.4% of the negative aerobic bottles, and in 31.7% of the negative anaerobic bottles. Utilizing FISH, we detected bacteria in 75.6%, 56.1%, and 64.6% respectively. Among the blood samples from healthy volunteers, FISH detected bacteria in 64.9%, while Gram stain detected bacteria in only 38.6%. The time needed to obtain the study results using Gram stain was 1 h, for FISH 4 h, and for the culture method, considering the duration of growth, 5 days. Gram stain and FISH allow quick detection of bacteria in the blood taken directly from a patient. Finding phagocytosed bacteria, which were also detected among healthy individuals, confirms the hypothesis that blood microbiome exists.

scholarly journals Scanning Electron Microscope: A New Potential Tool to Replace Gram Staining for Microbe Identification in Blood Cultures

2021 ◽  
Vol 9 (6) ◽  
pp. 1170
Author(s):  
Gabriel Haddad ◽  
Sara Bellali ◽  
Tatsuki Takakura ◽  
Anthony Fontanini ◽  
Yusuke Ominami ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Blood Culture ◽  
Scanning Electron Microscope ◽  
Sample Preparation ◽  
Bloodstream Infections ◽  
Blood Cultures ◽  
Preliminary Identification ◽  
Gram Staining ◽  
Micro Organisms ◽  
Scanning Electron

Blood culture is currently the most commonly used method for diagnosing sepsis and bloodstream infections. However, the long turn-around-time to achieve microbe identification remains a major concern for clinical microbiology laboratories. Gram staining for preliminary identification remains the gold standard. We developed a new rapid strategy using a tabletop scanning electron microscope (SEM) and compared its performance with Gram staining for the detection of micro-organisms and preliminary identification directly from blood cultures. We first optimised the sample preparation for twelve samples simultaneously, saving time on imaging. In this work, SEM proved its ability to identify bacteria and yeasts in morphotypes up to the genus level in some cases. We blindly tested 1075 blood cultures and compared our results to the Gram staining preliminary identification, with MALDI-TOF/MS as a reference. This method presents major advantages such as a fast microbe identification, within an hour of the blood culture being detected positive, low preparation costs, and data traceability. This SEM identification strategy can be developed into an automated assay from the sample preparation, micrograph acquisition, and identification process. This strategy could revolutionise urgent microbiological diagnosis of infectious diseases.

Reducing the Contamination Rate and the Unnecessary Requesting of Blood Culture Test through Quality Improvement Project

2021 ◽  
Vol 30 (1) ◽  
pp. 87-91
Author(s):  
Tamer Mohamed ◽  
Ashraf A Askar ◽  
Jamila Chahed
Keyword(s):  
Quality Improvement ◽  
Blood Culture ◽  
Armed Forces ◽  
Blood Cultures ◽  
Quality Improvement Project ◽  
Contamination Rate ◽  
Improvement Project ◽  
Culture Test ◽  
Negative Results ◽  
Before And After

Background: Blood stream infections are major leading causes of morbidity and mortality in hospitalized patients. Increasing the awareness of the clinicians and nurses about the proper protocol of blood culture test is very important in reducing the contamination rate and the unnecessary requesting of blood culture. Objectives: to reduce the contamination rate and the unnecessary requesting of blood culture from different departments through implementation of hospital wide Quality Improvement Project (QIP). Methodology: Blood cultures were tested in the Microbiology Laboratory of Najran Armed Forces hospital, Saudi Arabia, in the period from June 2019 to July 2020 and their results were compared before and after the implementation of the QIP. Results: The comparison between the blood cultures results before and after QIP implementation showed statistically significant (19.6%) reduction in the contamination rate, (14%) reduction in the total number of blood culture requests and (11.6%) reduction in the negative results rate. Conclusion: The reduction in the total number, negative results and contamination rate of blood culture test after QIP implementation were considered as performance indicators that the recommendations of QIP were effective and implemented strictly.

scholarly journals Rapid Diagnosis of Bacteremia in Adults Using Acridine Orange Stained Buffy Coat Smears

1990 ◽  
Vol 1 (1) ◽  
pp. 7-10
Author(s):  
Mark Miller ◽  
Jack Mendelson
Keyword(s):  
Blood Culture ◽  
Acridine Orange ◽  
Buffy Coat ◽  
Blood Cultures ◽  
Rapid Screening ◽  
Blood Culture System ◽  
Blood Samples ◽  
Significant Difference ◽  
Rapid Screening Test ◽  
Low Sensitivity

The use of acridine orange stained buffy coat smears was assessed as a rapid screening test for bacteremia in adults. A total of 356 consecutive blood cultures were submitted with simultaneous anticoagulated blood samples, from which a buffy coat smear was prepared and stained with acridine orange (100 mg/L; pH 3.0). Forty-one of 356 blood samples (12%) yielded organisms in the blood culture system. Compared to blood culture, the overall sensitivity of acridine orange stained buffy coat smears was 16%, specificity 88%, and positive predictive value 13%. There was no statistically significant difference in performance of the test among patients who had fever greater than 39°C and/or shock. The low sensitivity and specificity of the test makes it unsuitable as a means of rapid screening for adults with suspected bacteremia.

scholarly journals “A Four-Leaf Clover” Sign for Rapid Identification of Coagulase-Negative Staphylococci by Gram Staining From Positive Blood Culture: A Cross-Sectional Study

2020 ◽  
Author(s):  
Takahiro Matsuo ◽  
Kuniyoshi Hayashi ◽  
Aki Sakurai ◽  
Masumi Suzuki Shimizu ◽  
Masaya Morimoto ◽  
...  
Keyword(s):  
Logistic Regression ◽  
Regression Analysis ◽  
Blood Culture ◽  
Positive Predictive Value ◽  
Positive Blood Culture ◽  
Predictive Value ◽  
Blood Cultures ◽  
Coagulase Negative Staphylococci ◽  
Gram Staining ◽  
Sensitivity Specificity

Abstract Background: Coagulase-negative staphylococci (CoNS) are one of the most common contaminant microorganisms isolated from blood cultures. Few studies exploring the use of Gram staining to distinguish between Staphylococcus aureus (SA) and CoNS have been reported. Here, this study aimed to explore whether morphological features of Gram staining could identify SA or CoNS.Methods: This study was conducted at St. Luke’s International Hospital from November 2016 to September 2017. The positive blood cultures for which the Gram staining showed gram-positive cocci (GPC) in clusters were included in our study. The direct smear of Gram staining obtained from positive blood culture bottles were examined within 24 hours of positivity. We have identified and characterized the following two signs: “four-leaf clover (FLC)” if 4 GPC gathered like a planar four-leaf clover and “grapes” if the GPC gathered like grapes in a three-dimensional form. The number of fields with FLC and grapes signs in 10 fields per slide with ×1,000 power was counted, and the results in a total of 20 fields with ×1,000 power were combined. We performed a logistic regression analysis to assess whether these signs could serve as factors distinguishing between SA and CoNS. The predictive ability of these signs was evaluated based on the sensitivity, specificity, positive predictive value, and negative predictive value for CoNS via receiver operating curve analysis.Results: In total, 106 blood cultures for which Gram staining showed GPC in clusters were examined; 46 (43%) were SA, and 60 (57%) were CoNS samples. The result of multivariate logistic regression analysis showed that the FLC sign was a statistically significant marker of CoNS with an odds ratio of 1.31 (95 % confidential interval (CI): 1.07–1.61, p<0.05). In aerobic bottles, sensitivity, specificity, positive predictive value, and negative predictive value for CoNS were 0.67, 0.91, 0.92, and 0.65, respectively, and the value of area under the curve was 0.79 (95% CI: 0.67–0.91).Conclusions: To our knowledge, this is the first study to show that the FLC could be a rapid and useful indicator to identify CoNS in aerobic bottles. Thus, the presence of FLC sings could help clinicians to suspect the possibility of CoNS before the final identification by cultures.

scholarly journals Detection of Acinetobacter spp. in Blood Cultures by an Improved Fluorescent in Situ Hybridization Assay

2018 ◽  
Vol 67 (1) ◽  
pp. 3-10 ◽  
Author(s):  
Hanieh Asaadi ◽  
Behrouz Naeimi ◽  
Somayyeh Gharibi ◽  
Abdalnaser Khosravi ◽  
Sina Dobaradaran ◽  
...  
Keyword(s):  
In Situ Hybridization ◽  
Blood Culture ◽  
Signal Intensity ◽  
Fluorescent In Situ Hybridization ◽  
Accurate Method ◽  
Blood Cultures ◽  
Simultaneous Application ◽  
Fluorescent Signal ◽  
Acinetobacter Spp

Fluorescent in situ hybridization (FISH) allows rapid detection of microorganisms. We aimed (i) to evaluate the sensitivity and specificity of FISH for the detection of Acinetobacter spp. in blood culture specimens and (ii) to test the simultaneous application of two genus-specific probes labeled with the same fluorochrome to increase the fluorescent signal intensity and improve the detection of Acinetobacter spp. Three hundred and twenty blood culture specimens were tested via both the conventional laboratory methods and FISH to detect Acinetobacter spp. The specimens were examined separately with each genus-specific probe Aci and ACA, and also using a mixture of the both probes Aci and ACA. In all examinations, probe EUB338 was used accompanied by Aci and ACA. The specificity of FISH was 100% (97.5% confidence interval [CI] = 98.7% – 100%). The sensitivity of FISH by the use of probe Aci was 96.4% (95% CI = 81.7% – 99.9%), whereas, the sensitivity of this technique by the use of probe ACA as well as by the combination of both probes Aci and ACA was 100% (97.5% CI = 87.7% – 100%). Moreover, simultaneous hybridization by probes Aci and ACA increased the fluorescent signal of Acinetobacter spp. cells to 3+ in 13 specimens. In conclusion, FISH, particularly using a combination of Aci and ACA, is a highly accurate method for the detection of Acinetobacter spp. in blood cultures. Furthermore, simultaneous hybridization by the both probes Aci and ACA can increase the fluorescent signal intensity of Acinetobacter spp. cells in some blood culture specimens and facilitate the detection of these microorganisms.

scholarly journals THE DETECTION OF BACTEREMIA USING GRAM STAINING AND FLUORESCENT IN SITU HYBRIDIZATION IN SEPTIC PATIENTS WITH NEGATIVE BLOOD CULTURES

CHEST Journal ◽  
2021 ◽  
Vol 160 (4) ◽  
pp. A1044
Author(s):  
Tomasz ZRODLOWSKI ◽  
Joanna Sobonska ◽  
Isabel McFarlane ◽  
Dominika Salamon ◽  
Miroslaw Ziętkiewicz ◽  
...  
Keyword(s):  
In Situ Hybridization ◽  
Fluorescent In Situ Hybridization ◽  
Blood Cultures ◽  
Gram Staining

scholarly journals Misinterpretation of Gram Stain from the Stationary Growth Phase of Positive Blood Cultures for Brucella and Acinetobacter Species

2017 ◽  
Vol 11 (1) ◽  
pp. 126-131 ◽  
Author(s):  
Ali M. Bazzi ◽  
Jaffar A. Al-Tawfiq ◽  
Ali A. Rabaan
Keyword(s):  
Real Time Pcr ◽  
Blood Cultures ◽  
Blood Agar ◽  
Gram Stain ◽  
Gram Positive ◽  
Gram Negative ◽  
Gram Staining ◽  
Urease Test ◽  
Oxidase Test ◽  
Vitek 2

Introduction:Acinetobacter baumanniiandBrucellaspecies are Gram-negative organisms that are vulnerable to misinterpretation as Gram-positive or Gram-variable in blood cultures.Objective:We assess the random errors in gram stain interpretation to reduce the likelihood of such errors and therefore patient harm.Methodology:Aerobic and anaerobic blood cultures from two patients in an acute care facility in Saudi Arabia were subjected to preliminary Gram-staining. In case 1, VITEK-2 Anaerobe Identification, repeat Gram staining from a blood agar plate, Remel BactiDrop™ Oxidase test, Urea Agar urease test and real-time PCR were used to confirm presence ofBrucellaand absence ofCoryneformspecies. In case 2, repeat Gram- staining from the plate and the vials, VITEK-2 Gram-Negative Identification, real-time PCR and subculture on to Columbia agar, blood agar, and MacConkey agar were carried out to identifyA. baumannii.Results:In case 1, initially pleomorphic Gram-positive bacteria were identified.Coryneformspecies were suspected. Tiny growth was observed after 24 h on blood agar plates, and good growth by 48 h. Presence ofBrucellaspecies was ultimately confirmed. In case 2, preliminary Gram-stain results suggested giant Gram-positive oval cocci. Further testing over 18-24 h identifiedA. baumannii.Conclusions:Oxidase test from the plate and urease test from the culture vial is recommended after apparent identification of pleomorphic Gram-positive bacilli from blood culture, once tiny growth is observed, to distinguishBrucellafromCorynebacteriumspecies. If giant Gram-positive oval cocci are indicated by preliminary Gram-staining, it is recommended that the Gram stain be repeated from the plate after 4-6 h, or culture should be tested in Triple Sugar Iron (TSI) medium and the Gram stain repeated after 2-4 h incubation.

scholarly journals Lack of Utility of the Lysis-Centrifugation Blood Culture Method for Detection of Fungemia in Immunocompromised Cancer Patients

1998 ◽  
Vol 36 (1) ◽  
pp. 290-293 ◽  
Author(s):  
Richard J. Creger ◽  
Kisa E. Weeman ◽  
Michael R. Jacobs ◽  
Anne Morrissey ◽  
Pamela Parker ◽  
...  
Keyword(s):  
Blood Culture ◽  
Cancer Patients ◽  
Fungal Infections ◽  
Neutropenic Patient ◽  
False Negative ◽  
Culture Method ◽  
Blood Cultures ◽  
Fungal Isolation ◽  
Clinical Criteria ◽  
Febrile Neutropenic Patient

We retrospectively compared the utility of a fungal isolation device (Isolator) versus conventional techniques for recovering fungal organisms from blood cultures obtained from neutropenic cancer patients. Positive cultures were deemed true pathogens, possible pathogens, or contaminants according to laboratory and clinical criteria. Fifty-three patients had 66 positive blood cultures for fungi, nine on multiple occasions. In 20 episodes true pathogens were recovered, 6 from broth medium alone, 4 from the Isolator system alone, and 10 from both systems. False-negative cultures were noted in 4 of 20 (20%) cases in which broth medium was used and in 6 of 20 (30%) cases in which the Isolator system was used. Possible pathogens were detected in 4 of 66 blood culture-positive cases. Forty-two positive cultures were considered contaminants, 1 collected from standard medium and 41 of 42 (98%) which grew only in Isolators. Eleven of 18 patients with true fungal infections expired as a result of infection, while 4 of 33 patients with a contaminant expired, none from a fungal cause. We do not advocate the routine use of Isolator tubes in the evaluation of the febrile, neutropenic patient due to the high rates of false positives and of contamination.

What are the critical steps in processing blood cultures? A prospective audit evaluating current practice of reporting blood cultures in a centralised laboratory serving secondary care hospitals

2016 ◽  
Vol 70 (4) ◽  
pp. 361-366 ◽  
Author(s):  
Manjula Meda ◽  
James Clayton ◽  
Reela Varghese ◽  
Jayakeerthi Rangaiah ◽  
Clive Grundy ◽  
...  
Keyword(s):  
Blood Culture ◽  
Secondary Care ◽  
Rapid Identification ◽  
Antimicrobial Treatment ◽  
Blood Cultures ◽  
National Standards ◽  
Gram Stain ◽  
Gram Positive ◽  
Gram Negative ◽  
Common Intervention

AimsTo assess current procedures of processing positive blood cultures against national standards with an aim to evaluate its clinical impact and to determine the utility of currently available rapid identification and susceptibility tests in processing of blood cultures.MethodsBlood cultures from three secondary care hospitals, processed at a centralised laboratory, were prospectively audited. Data regarding processing times, communication with prescribers, changes to patient management and mortality within 30 days of a significant blood culture were collected in a preplanned pro forma for a 4-week period.ResultsOf 2206 blood cultures, 211 positive blood cultures flagged positive. Sixty-nine (3.1%) of all cultures were considered to be contaminated. Fifty per cent of blood cultures that flagged positive had a Gram stain reported within 2 hours. Two (0.99%) patients with a significant bacteraemia had escalation of antimicrobial treatment at the point of reporting the Gram stain that was subsequently deemed necessary once sensitivity results were known. Most common intervention was de-escalation of therapy for Gram-positive organisms at the point of availability of pathogen identification (25.6% in Gram positive vs 10% in Gram negative; p=0.012). For Gram-negative organisms, the most common intervention was de-escalation of therapy at the point of availability of sensitivity results (43% in Gram negatives vs 17.9% in Gram positive; p=0.0097). Overall mortality within 30 days of a positive blood culture was 10.9% (23/211). Antibiotic resistance may have contributed to mortality in four of these patients (three Gram negative and one Gram positive).ConclusionGram stain result had the least impact on antibiotic treatment interventions (escalation or de-escalation). Tests that improve identification time for Gram-positive pathogens and sensitivity time for Gram-negative pathogens had the greatest impact in making significant changes to antimicrobial treatment.

Timeliness and Accuracy of Reporting Preliminary Blood Culture Results: A College of American Pathologists Q-Probes Study of 65 Institutions

2015 ◽  
Vol 139 (5) ◽  
pp. 621-626 ◽  
Author(s):  
Ron B. Schifman ◽  
Frederick A. Meier ◽  
Rhona J. Souers
Keyword(s):  
Blood Culture ◽  
Median Time ◽  
Patient Outcomes ◽  
Turnaround Time ◽  
Blood Cultures ◽  
Initial Growth ◽  
Gram Stain ◽  
Quality Performance ◽  
Speed And Accuracy ◽  
Growth Detection

Context The speed and accuracy of preliminary blood culture reports impacts patient management and outcomes. Objective To evaluate the accuracy and timeliness of preliminary blood culture results among multiple laboratories. Design Q-Probes participants collected turnaround time (TAT) data on preliminary Gram stains, compared accuracy of up to 100 preliminary to final culture Gram stain results, and described blood culture laboratory practices. Results Sixty-four laboratories and 5031 blood cultures were evaluated. All participants used continuously monitoring blood culture systems. Median TAT from initial growth detection to notification of results was 45 minutes, with the longest component being preparation of Gram stains (median time = 25 minutes). Participants (N = 40) reporting a continuous schedule for processing blood cultures had significantly lower overall TAT (medianm= 37 minutes) compared with 15 participants with intermittent processing schedules (medianm= 124 minutes),mPm= .003. Time to complete Gram stain processing was lower (median time = 21 minutes) for 39 participants using continuous processing schedule compared with 14 others (median timem= 67 minutes),mPm= .03. Goals for total TAT were used by 27 of 56 participants (48.2%). Having goals did not significantly affect TAT. A total of 4962 of 5021 Gram stain results (98.8%) agreed with final culture results. The highest discrepancy rates occurred among gram-positive bacilli (20 of 335; 6.0%) and mixed cultures (22 of 106; 20.8%). Conclusions This study provides benchmarks for assessing blood culture quality performance. Timeliness and accuracy of preliminary blood culture reports were excellent. However, nearly one-third of laboratories did not process blood cultures continuously. This significantly prolonged reporting results, which could affect patient outcomes.

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