Qualitative Blood Cultures Research Articles

Diagnosis and prevention of catheter-related infections

To highlight the major advances in diagnosing and preventing catheter-related infections published in research articles published between March 2004 and May 2007. The challenge remains to make the diagnosis of catheter-related infection with good accuracy without catheter removal. The differential time to obtain positive qualitative blood culture appeared to be the most accurate available technique. Many catheter-related bloodstream infections are preventable. Simple interventions are often useful and multimodal programs are very efficacious, particularly in the intensive care setting. For long-term catheter-related bloodstream infection prevention, patient education appeared promising. Interesting evidence suggested that anticoagulant, by decreasing the biofilm formation, could decrease the risk of infection. For short-term central venous catheter-related infections research is ongoing on antiseptic dressings. Antiseptic lock appeared promising for preventing long-term central venous catheter bloodstream infections. Nowadays, multimodal programs of catheter infection prevention are efficacious. Levels of catheter-related bloodstream infection of more than one or two per 1000 catheter-days are usually only found in the intensive care unit. It is a prerequisite to evaluate the cost-effectiveness of new techniques of prevention. As catheter-related bloodstream infections become rarer, strategies limiting unnecessary removal of catheters need to be developed and tested.

Antibiotic-lock therapy for long-term intravascular catheter-related bacteraemia: results of an open, non-comparative study

Infection is one of the main problems associated with long-term central venous catheters. This study assesses the effectiveness of antibiotic-lock therapy (ALT) for treating catheter-related bacteraemia (CRB). CRB was defined as quantitative blood culture counts through any catheter lumen 5-fold greater than concurrent peripheral blood culture, and qualitative blood culture positive for the same microorganism in all samples. Systemic treatment and ALT were started simultaneously using vancomycin (2000 mg/L) for Gram-positive organisms, and ciprofloxacin or amikacin (2000 mg/L) for Gram-negative bacilli. Heparin was added to ALT. Effectiveness was assessed by clinical and microbiological criteria. Cure was defined as negative blood cultures at both sites without catheter removal at 1 month after the completion of therapy. A total of 115 episodes of CRB in 98 patients were analysed. Catheters were used for chemotherapy (50 episodes), haemodialysis (37), total parenteral nutrition (24) and combined chemotherapy and nutrition (4). Median time from catheter placement to CRB onset was 105 days (IQ range 26-210). Aetiologies included Gram-positive organisms [56 coagulase-negative staphylococci (CoNS), 20 Staphylococcus aureus and 5 other organisms] in 81 episodes (70%), Gram-negative bacilli (11 Escherichia coli, 5 Pseudomonas aeruginosa and 10 other organisms) in 26 (23%) and polymicrobial in 8 (7%). A total of 94 episodes were cured (82%). There were 21 therapeutic failures: 9 S. aureus (1 related death), 9 CoNS, 1 P. aeruginosa, 1 Proteus vulgaris and 1 polymicrobial. Median catheter follow-up in therapeutic success was 168 days (range 7-2740). ALT combined with systemic antibiotics seems to be effective for treating CRB, especially in Gram-negative and CoNS episodes. S. aureus CRB had an elevated rate of therapeutic failure.

Qualitative versus quantitative blood cultures in the diagnosis of catheter‐related bloodstream infections in children with malignancy

Paired quantitative and qualitative blood cultures have been introduced for the diagnosis of catheter-related bloodstream infections (CRBI) with the catheter in situ. The aim of the study was to compare the diagnostic performance and the prognostic value of the two methods in the evaluation of febrile episodes without an apparent source in children with cancer. During a 4-year period, in every febrile episode without an apparent focus, blood was drawn simultaneously from the catheter lumen and a peripheral vein in order to perform paired quantitative (Isolator) as well as qualitative (BacT/Alert) blood cultures. The diagnosis of a CRBI was defined as either a case of greater (at least 10 fold) or earlier (differential time to positivity >2 h) bacterial growth from the catheter compared to the peripheral blood sample, respectively. Nineteen febrile episodes manifested in 16 children (total period of observation 11,150 catheter-days) were evaluated with both methods. A concordant diagnosis of CRBI was stated with both methods in six episodes; one episode was diagnosed as CRBI only with qualitative culture criteria. Treatment failure resulted in catheter removal in five out of the seven episodes defined as CRBI with either method. Episodes where a CRBI was ruled out with both methods had a favorable outcome. In this study the two methods showed comparable results in the diagnosis of CRBI and both were of prognostic significance, regarding the outcome of the treatment. However, large scale studies are required in order to evaluate the clinical relevance and the cost effectiveness of performing routinely paired blood cultures with either method.

Hub qualitative blood culture is useful for diagnosis of catheter-related infections in critically ill patients

To assess clinical safety and accuracy of qualitative blood culture drawn through the hub for ruling out catheter-related infection (CRI). Prospective observational study in a surgical intensive care unit. All patients with sepsis of unknown origin and possibly due to a CRI. Blood culture drawn through a central venous catheter (CVC) just before the catheter was cultured. In 126 patients we investigated 135 cases of sepsis of unknown origin. Using a clinical and bacteriological approach as the reference, the performance of the CVC blood culture was evaluated by the calculation of sensitivity, specificity, and positive and negative predictive values. When CVC blood culture was positive, the time to positivity was considered. Using standard definitions, seven CRIs were diagnosed. CVC blood culture identified five CRIs including the three episodes of catheter-related bacteremia. The method missed two coagulase-negative staphylococcus CRIs without bacteremia. Thirteen false-positive results occurred, including seven bacteremias from a distant source. The CVC blood culture had a sensitivity of 71% (CI 30-95%), specificity of 90% (CI 83-94%), negative predictive value of 98% (CI 93-100%), and positive predictive value of 28% (CI 11-54%). In cases of catheter-related bacteremia the time to positivity of CVC blood culture was 24 h or less. Negative CVC blood culture at 24 h seems useful for management of CVC in selected critically ill surgical patients developing a clinical sepsis. The subsequent risk of catheter-related bacteremia cannot be excluded advocating for an uninterrupted clinical and bacteriological survey.

Diagnosis of Intra Vascular Catheter-Related Infection

The use of central vascular catheters (CVC) is associated with a substantial number of complications, amongst which infections predominate. A diagnosis of CVC-related infection usually requires catheter removal for culture. Semiquantitative (roll-plate method) and quantitative methods (flush, vortex, centrifugation or sonication methods) are the most reliable diagnostic methodologies requiring catheter removal, because of their greater specificity. The roll-plate method is the simplest and most commonly used technique. This method only samples the external surface of the catheter, and is particularly indicated for recently inserted catheters in which extraluminal colonisation is the primary mechanism of infection. Luminal culture techniques, such as the quantitative methods, may be more relevant for catheters that have been in place for a long period of time. However, in up to 85% of removed CVC the culture is negative, and other diagnostic techniques that do not require catheter removal have been proposed, including paired quantitative blood cultures, endoluminal brushing, and differential time to positivity (DTP) of paired blood cultures. DTP, that compares the time to positivity for qualitative cultures of blood samples simultaneously drawn from the CVC and a peripheral vein, appears to be the most reliable in the routine clinical practice since many hospitals use automatic devices for qualitative blood culture positivity detection. More recently catheter-sparing direct diagnostic methods, which include Gram stain and acridin-orange leucocyte cytospin (AOLC) test, appeared to be especially useful because of the rapidity of results and the ability to distinguish different microorganisms, allowing early targeted antimicrobial therapy.

Central venous blood culture: a useful test for catheter colonisation?

To evaluate the widespread practice of using qualitative culture of venous blood taken through central venous catheters (CVCs) as a means of diagnosing catheter colonisation in situ. A prospective clinical study. Three hundred fifty-one CVCs were inserted into 228 critically ill patients. Prior to CVC removal, blood was taken for qualitative culture from the CVC and a peripheral site. All catheter tips underwent semi-quantitative analysis of bacterial colony count [1]. One hundred eighteen (33.6%) CVCs were found to be colonised on removal. A positive central blood culture had a sensitivity and specificity of 50.8% and 78.9% when compared with the 'gold standard' of catheter tip culture. This gives a positive predictive value of 47.7% and a negative predictive value of 76.5%. The sensitivity and specificity of a positive peripheral blood culture were 41.5% and 77.7% with positive and negative predictive values of 48.8% and 72.9%, respectively. When only those catheters removed because of systemic sepsis (n = 139) were considered, a positive central blood culture had a sensitivity of 58.8% and a specificity of 69.3%. Our results indicate that the use of central blood culture confers a small advantage in sensitivity compared with peripheral blood culture. This advantage was further improved by only considering the catheters removed because of systemic sepsis but at the cost of a loss of specificity. Qualitative blood culture is a poor tool for the diagnosis of in-situ CVC colonisation.

Bacteremia during bronchoalveolar lavage.

We prospectively evaluated the incidence of bacteremia during fiberoptic bronchoalveolar lavage (BAL) and its relationship to postlavage symptoms in 12 volunteers. Qualitative and quantitative blood cultures were obtained before and during BAL. Three persons had qualitative blood cultures positive for organisms typical of normal skin flora. Quantitative blood cultures done simultaneously were negative. Approximately 42% of our subjects had postlavage symptoms, but no correlation was found between bacteremia and the occurrence of postlavage symptoms. Our results confirm the relative safety of BAL and the low incidence of BAL-associated bacteremia.

Comparative culture methods on 101 intravenous catheters. Routine, semiquantitative, and blood cultures

• Broth cultures and semiquantitative cultures (SQCs) were done on 101 intravenous (IV) catheters from 82 patients. Catheters were in place an average of ten days (range, one to 40 days). Twenty-eight catheters yielded 15 colonies or more on SQCs of transcutaneous catheter segments.<i>Staphylococcus epidermidis</i>was the most common microbial isolate found on 21 of the 28 catheters on SQC. Broth tip cultures, SQCs on tips and transcutaneous segments, qualitative blood cultures (QIBCs), and quantitative blood cultures (QnBCs) drawn via the catheters were significantly associated with peripheral bacteremia. The presence of systemic antimicrobials made no significant difference in SQC, QIBC, or QnBC positivity. With the exception of gross pus, local inflammation was not significantly associated with catheter infection. Local site care by a special team of nurses resulted in significantly fewer catheter infections than did care given by ward nurses. (<i>Arch Intern Med</i>1983;143:66-69)

Comparative Culture Methods on 101 Intravenous Catheters

Broth cultures and semiquantitative cultures (SQCs) were done on 101 intravenous (IV) catheters from 82 patients. Catheters were in place an average of ten days (range, one to 40 days). Twenty-eight catheters yielded 15 colonies or more to SQCs of transcutaneous catheter segments. Staphylococcus epidermidis was the most common microbial isolate found on 21 of the 28 catheters on SQC. Broth tip cultures, SQCs on tips and transcutaneous segments, qualitative blood cultures (QIBCs), and quantitative blood cultures (QnBCs) drawn via the catheters were significantly associated with peripheral bacteremia. The presence of systemic antimicrobials made no significant difference in SQC, QIBC, or QnBC positivity. With the exception of gross pus, local inflammation was not significantly associated with catheter infection. Local site care by a special team of nurses resulted in significantly fewer catheter infections than did care given by ward nurses.

Granulocyte Transfusions in Leukopenic Dogs: In Vivo and In Vitro Function of Granulocytes Obtained by Continuous-Flow Filtration Leukopheresis

Abstract The present studies were carried out to (1) evaluate a leukoadhesive technique for obtaining granulocytes for transfusion, (2) assess the granulocytes by in vitro techniques, and (3) determine the efficacy of granulocyte transfusion in preventing sepsis in leukopenic dogs. Dogs were rendered transiently leukopenic (&lt; 500 per cu mm) by intravenous cyclophosphamide, 40 mg/kg. Quantitative and qualitative blood cultures were obtained from all animals until death or hematologic recovery. Granulocytes were obtained on nylon filters by a continuous flow system and eluted with an ACD plasma saline solution. Granulocyte function was studied in vitro by chemotaxis, phagocytosis, intracellular killing, and electron microscopy. In vivo studies consisted of the measurement of granulocyte increments in transfused leukopenic dogs, T ½ of infused granulocytes, and protection of transfused dogs from septicemic episodes. Eluted granulocytes, when compared to normal controls, showed reduction in in vitro functions. These functions improved in granulocytes isolated post-transfusion from recipient dogs. An average of 3 x 1010 granulocytes could be obtained during a 1-hr leukopheresis of normal donors. Increments in recipient dogs averaged 2590 per cu mm. Five nontransfused leukopenic dogs developed septicemia and died within 7 days. Six dogs were treated with infusions of granulocytes. Three recovered completely, and three died of thrombocytopenic hemorrhage with negative blood cultures. One dog showed a transiently positive blood culture that became negative following transfusion. Septic episodes were significantly reduced in granulocyte transfused dogs (p &lt; 0.01). It was concluded that continuous-flow leukofiltration yielded granulocytes in sufficient number and with adequate functional capabilities to provide significant protection against septic death in the leukopenic host.