Usefulness of gram staining of blood collected from total parenteral nutrition catheter for rapid diagnosis of catheter-related sepsis

High positive predictive value of Gram stain on catheter-drawn blood samples for the diagnosis of catheter-related bloodstream infection in intensive care neonates

Catheter-related bloodstream infections (CRBSIs) remain a leading cause of healthcare-associated infections in preterm infants. Rapid and accurate methods for the diagnosis of CRBSIs are needed in order to implement timely and appropriate treatment. A retrospective study was conducted during a 7-year period (2005-2012) in the neonatal intensive care unit of the University Hospital Erasme to assess the value of Gram stain on catheter-drawn blood samples (CDBS) to predict CRBSIs. Both peripheral samples and CDBS were obtained from neonates with clinically suspected CRBSI. Gram stain, automated culture and quantitative cultures on blood agar plates were performed for each sample. The paired quantitative blood culture was used as the standard to define CRBSI. Out of 397 episodes of suspected CRBSIs, 35 were confirmed by a positive ratio of quantitative culture (>5) or a colony count of CDBS culture >100 colony-forming units (CFU)/mL. All but two of the 30 patients who had a CDBS with a positive Gram stain were confirmed as having a CRBSI. Seven patients who had a CDBS with a negative Gram stain were diagnosed as CRBSI. The sensitivity, specificity, positive predictive value and negative predictive value of Gram stain on CDBS were 80, 99.4, 93.3 and 98.1 %, respectively. Gram staining on CDBS is a viable method for rapidly (<1 h) detecting CRBSI without catheter withdrawal.

Central venous catheter-related bloodstream infections in the intensive care unit

CONTEXT

Central venous catheter-related bloodstream infection (CRBSI) is associated with high rates of morbidity and mortality in critically ill patients.

AIMS

This study was conducted to determine the incidence of central venous catheter-related infections (CRIs) and to identify the factors influencing it. So far, there are very few studies that have been conducted on CRBSI in the intensive care unit in India.

SETTINGS AND DESIGN

This was a prospective, observational study carried out in the medical intensive care unit (MICU) over a period of 1 year from January to December 2004.

MATERIALS AND METHODS

A total of 54 patients with indwelling central venous catheters of age group between 20 and 75 years were included. The catheters were cultured using the standard semiquantitative culture (SQC) method. Statistical analysis used SPSS-10 version statistical software.

RESULTS

A total of 54 CVC catheters with 319 catheter days were included in this study. Of 54 patients with CVCs studied for bacteriology, 39 (72.22%) catheters showed negative SQCs and also negative blood cultures. A total of 15 (27.77%) catheters were positive on SQC, of which 10 (18.52%) were with catheter-associated infection and four (7.41%) were with catheter-associated bacteremia; the remaining one was a probable catheter-associated bacteremia. CRIs were high among catheters that were kept in situ for more than 3 days and emergency procedures where two or more attempts were required for catheterization (P < 0.05). In multivariate analysis of covariance duration of catheter in situ for >3 days, inexperienced venupucturist, more number of attempts and emergency CVC were associated with more incidence of CVCBSIs, with P <0.02. The duration of catheter in situ was negatively correlated (-0.53) and number of attempts required to put CVC was positively correlated (+0.39) with incidence of CVCBSIs. Sixty-five percent of the isolates belonged to the CONS group (13/20). Staphylococcus epidermidis showed maximum susceptibility to amikacin, doxycycline and amoxycillin with clavulanic acid and was susceptible to vancomycin (100%). Klebsiella pneumoniae was 100% susceptible to amikacin and ciprofloxacin. Escherichia coli was susceptible to amikacin and cefotaxime.

CONCLUSIONS

The overall incidence of CRI was 27.77% (15/54). Catheter-associated BSIs were 47.31 per 1000 catheter-days. CRI was low in the catheters inserted by the experienced venipuncturists, elective procedure and CVC kept in situ for ≤3 days. S. epidermidis was the most common isolate.

Infectious Complications of Cancer Therapy

Advances in the management of cancer, particularly the development of new chemotherapeutic agents, have greatly improved the survival and outcome of patients with hematologic malignancies and solid tumors; overall 5-year survival rates in cancer patients have improved from 39% in the 1960s to 60% in the 1990s.1 However, infection, caused by both the underlying malignancy and cancer chemotherapy, particularly myelosuppressive chemotherapy, remains a persistent challenge.

Identification of central venous catheter-related infections in infants and children

OBJECTIVE

To define central venous catheter-related infections in infants and children for the purpose of enrolling children in sepsis studies, for epidemiology and surveillance studies, and for clinical management.

METHODS

Review of the literature and consensus of experts.

RESULTS

No changes were made to the current Centers for Disease Control and Prevention criteria for defining local catheter infection. Because catheter tips are not available as often in children as in adults, smaller blood volumes are drawn per culture decreasing sensitivity, and antibiotics are rarely withheld, slight modifications to the existing adult Centers for Disease Control and Prevention criteria were made to increase practical use. Catheter-related bloodstream infection was categorized as definite, probable, and possible based on culture results and clinical symptoms.

CONCLUSIONS

For the purposes of enrolling patients with sepsis in clinical trials, only patients who meet criteria for definite catheter-related bloodstream infection should be categorized as having the catheter as the infection source. Because many patients suspected of having catheter-related bloodstream infection do not have positive blood culture results, which makes the confirmation of infection difficult, we recommend that these patients not be enrolled in sepsis trials. Because catheter tips are often not obtained for culture in children, the epidemiology of catheter-associated bloodstream infection (bloodstream infection in a patient who has a central venous catheter and no other obvious source of infection) is better understood than the epidemiology of confirmed catheter-related bloodstream infection in infants and children. Definitions for catheter-related bloodstream infection that compare the through-catheter and peripheral culture for time to positivity or for quantitative growth are unlikely to be falsely positive, but sensitivity requires further validation.

Current laboratory techniques in the diagnosis of catheter-related infections

The unspecificity of the clinical manifestations of catheter-related infections (CRIs) makes laboratory confirmation necessary, and many diagnostic techniques have been developed. Semiquantitative culture of catheter tips has been accepted by most laboratories for its simplicity and is currently the reference technique. It discriminates between catheters producing infection (when > or = 15 colony forming units grow on the culture) and insignificant colonization. Nonquantitative methods improve the sensitivity of diagnosis of CRI but are less specific. Quantitative methods improve the specificity and can identify and quantify colonization of both the internal and external surfaces of the catheter; however, these are time-consuming techniques. The high rate of unnecessary catheter removal has promoted interest in in situ staining methods such as gram staining of the skin entry site and hub. These methods are simple to perform and have shown a high negative predictive value. Quantitative blood culture methods allow the diagnosis of CRI, but their sensitivity decreases in the absence of associated bacteremia. Finally, the introduction of molecular techniques has helped to explain the pathogenesis of CRI and could help to improve the management of nosocomial CRI.

Diagnosis of triple-lumen catheter infection: comparison of roll plate, sonication, and flushing methodologies

In a recent clinical trial, 248 triple-lumen catheters were removed from patients in an intensive care unit, and their tip and subcutaneous segments were cultured by both the sonication and roll plate methods; for 191 of these catheters, flush cultures of all three catheter lumens were also performed. Previously published quantitative endpoints were used to define significant catheter colonization. By using a composite index as a definition of colonization (any of the seven types of cultures meeting quantitative criteria), sonication of the subcutaneous segment was the most sensitive at detecting colonization (58%), followed by sonication of the catheter tip (53%). Sonication of both the subcutaneous and tip segments was 20% more sensitive than sonication of an adjacent catheter segment by the roll plate method (P < 0.05). The greater sensitivity of the sonication method could be attributed to its greater ability than the roll plate method to detect catheter lumen colonization (82 versus 57%, respectively; P = 0.01). A greater number of positive catheter segment cultures were found for colonized catheters from patients with associated bacteremia than for colonized catheters from patients without bacteremia (57 versus 37%; P = 0.004), making any culture method more likely to identify them. For catheters with significant colonization of only one site, the localization was as follows: 36.7% subcutaneous segment, 36.7% catheter lumen, and 26.6% tip segment. These findings suggest that the current practice of culturing a single segment of a central vascular catheter is inadequate and needs to be reexamined. They further suggest that initial colonization of the catheter lumen and tip segments may be more important than previously thought and may require a change in thinking of strategies designed to prevent catheter infection.

Catheter-related complications of cancer therapy

Although the management of CVC-related infection appears complex and at times the literature seems to be contradictory, simple guidelines can direct the clinician in a stepwise fashion. Knowledge of the pathogenesis of each organism and the immune status of the host is crucial to decide whether catheter removal or retention is indicated. For example, in general, GNB bacteremia does not immediately prompt catheter removal in a neutropenic patient but does in a nonneutropenic host because of the gastrointestinal source of the former and a primary catheter source in the latter. In summary, as more CVCs are inserted in patients undergoing chemotherapeutic, antimicrobial, transfusional, and nutritional supportive care, novel approaches to prevention and treatment of the associated infectious complications inherent with such devices are needed. A multifaceted approach from impregnated catheters to local catheter-site antisepsis was reviewed. We may find, however, that as simple handwashing between patients is crucial to infection control, so too is a trained catheter-care team using total barrier precautions and ensuring proper local catheter maintenance critical to preventing CVC-related infections.

Catheter-related sepsis during home parenteral nutrition

Catheter-related sepsis (CRS) in patients receiving home parenteral nutrition (HPN) is the most frequent complication, with an annual incidence rate of 0.30-0.50 in investigative/approved centres. CRS is responsible for patient deaths in 2.5% of cases which represent 50% of HPN-related deaths. A detailed and strictly applied protocol is the basis of prevention; therefore a low rate of CRS can be used as a marker of quality of care. Skin and hub cultures are used to rule out CRS since their predictive negative value assessed against (semi) quantitative cultures of cannulae were reported to be almost 100%. In the absence of catheter removal, clinical assessment plus quantitative blood cultures with a threshold ratio of 4:1 in central and peripheral blood is a reasonable basis of established CRS. Removal of the infected external cannula is necessary and immediate in cases of tunnel infection, virulent bacteria (e.g. Candida, Staph aureus or pseudomonas species) and for all occurrences of CRS on implantable chambers since conventional treatment fails to sterilise such devices. Thus standard antibiotic treatment may be effective in the absence of tunnel sepsis in the majority of CRS cases due to non-virulent bacteria (mainly Staph coagulase negative species). In these cases of CRS, our experience suggests that the antibiotic-lock technique offers definite advantages over conventional systemic antibiotic treatment, since external catheters were sterilised without recurrent sepsis in more than 85% of cases.