Evaluation of the usefulness of a quantitative blood culture in the diagnosis of catheter-related bloodstream infection: Comparative analysis of two periods (2002 and 2012).

INTRODUCTION: A retrospective study was conducted to investigate the usefulness of systematic quantitative blood culture (QBC) in the diagnosis of catheter-related bloodstream infection (CRBSI) during two 1-year periods (2002 and 2012). METHODS: The study included all QBC requests sent to the microbiology laboratory for suspected CRBSI in adults (≥18 years) with any type of intravascular catheter (IVC). Based on a ratio of ≥4:1CFU/mL of the same microorganism between IVC blood culture from any lumen and peripheral blood culture, 5 diagnostic groups were defined: confirmed or probable CRBSI, primary BSI, other focus of infection, and colonization. RESULTS: In total, 4521 QBCs were evaluated; 24% positive in 2002 and 16% in 2012 (P<0.0001). There were 243 episodes of suspected CRBSI (101 in 2002 and 142 in 2012). Confirmed CRBSI episodes were higher in 2002 than 2012 (56% vs 34%) (P<0.0001), whereas colonization episodes were lower (18% vs 38%) (P=0.0006). Gram-positive cocci decrease in 2012 relative to 2002 (56% vs 79.7%) (P=0.022). Almost one-third (32%) of confirmed CRBSI would have been missed if blood from all catheter lumens had not been cultured. CONCLUSIONS: QBC is a useful method for diagnosing CRBSI. Blood samples from all catheter lumens must be cultured to avoid missing around one-third of CRBSI diagnoses.

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

BACKGROUND: 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). METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.