Improving positive blood culture removal time significantly decreases total processing time.

CONTEXT: Timely processing of blood cultures with positive results, including Gram staining and notification of clinicians, is a critical function of the clinical microbiology laboratory. Analysis of processing time in our laboratory revealed opportunities to enhance workflow efficiency. We found that the average time from positive blood culture result to removal of the bottle for processing (positive-to-removal [PR] time) was inadequate for our rapid pathogen identification program. OBJECTIVE: To determine whether increased vigilance about PR time and prioritization of laboratory resources would decrease PR time and total processing time. DESIGN: We performed a retrospective analysis of blood culture PR time 7 months before and 7 months after an in-service meeting during which the importance of PR time was emphasized, and corrective measures were implemented. RESULTS: Before the in-service meeting, the average PR time for 5057 samples was 38 minutes, with an aggregate time of 192,251 minutes. Unexpectedly, we discovered that only 51.8% (2617 of 5057) of the positive blood cultures were removed in less than 10 minutes. After the in-service meeting, for 5293 samples, the average PR time improved to 8 minutes, the aggregate time improved to 44,630 minutes, and 84.5% (4470 of 5293) of the positive blood cultures were removed in less than 10 minutes. These improvements reduced the time to telephone notification of the Gram stain results to a caregiver by 46.7% (from 105 minutes to 56 minutes). CONCLUSIONS: Increased awareness of barriers to rapid pathogen identification and interventions for improving performance time significantly enhanced care of patients with bloodstream infections.

Intermediate-term graft loss after renal transplantation is associated with both donor-specific antibody and acute rejection.

BACKGROUND: Renal transplant recipients with de novo DSA (dDSA) experience higher rates of rejection and worse graft survival than dDSA-free recipients. This study presents a single-center review of dDSA monitoring in a large, multi-ethnic cohort of renal transplant recipients. METHODS: The authors performed a nested case-control study of adult kidney and kidney-pancreas recipients from July 2007 through July 2011. Cases were defined as dDSA-positive whereas controls were all DSA-negative transplant recipients. DSA were determined at 1, 3, 6, 9, and 12 months posttransplant, and every 6 months thereafter. RESULTS: Of 503 recipients in the analysis, 24% developed a dDSA, of whom 73% had dDSA against DQ antigen. Median time to dDSA was 6.1 months (range 0.2-44.6 months). After multivariate analysis, African American race, kidney-pancreas recipient, and increasing numbers of human leukocyte antigen mismatches were independent risk factors for dDSA. Recipients with dDSA were more likely to suffer an acute rejection (AR) (35% vs. 10%, P<0.001), an antibody-mediated AR (16% vs. 0.3%, P<0.001), an AR ascribed to noncompliance (8% vs. 2%, P=0.001), and a recurrent AR (6% vs. 1%, P=0.002) than dDSA-negative recipients. At a median follow-up of 31 months, the death-censored actuarial graft survival of dDSA recipients was worse than the DSA-free cohort (P=0.002). Yet, for AR-free recipients, there was no difference in graft survival between cohorts (P=0.66). CONCLUSIONS: Development of dDSA was associated with an increased incidence of graft loss, yet the detrimental effect of dDSA was limited in the intermediate term to recipients with AR.

The presence of anti-HLA donor-specific antibodies in lung allograft recipients does not correlate with C4d immunofluorescence in transbronchial biopsy specimens.

CONTEXT: C4d immunofluorescence (IF) is a surrogate for development of donor-specific antibodies (DSAs) against human leukocyte antigen (HLA) class I and II antigens in kidney and heart biopsy specimens for monitoring of antibody-mediated (humoral) allograft rejection (AMR). Use of C4d IF in monitoring of lung allografts has shown conflicting results. OBJECTIVE: To determine if C4d IF can be used as a reliable marker for AMR and if it correlates with the presence of DSAs and histologic findings on biopsy. DESIGN: All transbronchial biopsies in lung allograft recipients, performed at our institution in a 3-year period, were reviewed. A cohort of 92 patients with 110 corresponding biopsies met the inclusion criteria of (1) having a resulted DSA within 2 weeks of biopsy and (2) having C4d immunofluorescence studies performed and confirmed. RESULTS: Twenty-nine patients (31.5%) were positive for DSAs and 63 patients (68.5%) did not develop DSAs. Positive C4d capillary IF was seen in 18 of 110 total biopsy specimens (16.4%). Eight of these biopsy samples were from patients positive for DSAs and 10 were from patients negative for DSAs. The correlation coefficient between the presence of DSAs and C4d IF was 0.1628 (P = .09). CONCLUSIONS: A significant proportion of DSA-positive patients had negative C4d IF results and frequently have no histologic changes on biopsy specimens. DSA-negative patients can be positive for C4d and may show the same histologic changes as reported for DSA-positive patients. Diagnosis of AMR in lung may require a collaborative approach combining clinical data, DSA status, and histology.

Integrating rapid pathogen identification and antimicrobial stewardship significantly decreases hospital costs.

CONTEXT: Early diagnosis of gram-negative bloodstream infections, prompt identification of the infecting organism, and appropriate antibiotic therapy improve patient care outcomes and decrease health care expenditures. In an era of increasing antimicrobial resistance, methods to acquire and rapidly translate critical results into timely therapies for gram-negative bloodstream infections are needed. OBJECTIVE: To determine whether mass spectrometry technology coupled with antimicrobial stewardship provides a substantially improved alternative to conventional laboratory methods. DESIGN: An evidence-based intervention that integrated matrix-assisted laser desorption and ionization time-of-flight mass spectrometry, rapid antimicrobial susceptibility testing, and near-real-time antimicrobial stewardship practices was implemented. Outcomes in patients hospitalized prior to initiation of the study intervention were compared to those in patients treated after implementation. Differences in length of hospitalization and hospital costs were assessed in survivors. RESULTS: The mean hospital length of stay in the preintervention group survivors (n = 100) was 11.9 versus 9.3 days in the intervention group (n = 101; P = .01). After multivariate analysis, factors independently associated with decreased length of hospitalization included the intervention (hazard ratio, 1.38; 95% confidence interval, 1.01-1.88) and active therapy at 48 hours (hazard ratio, 2.9; confidence interval, 1.15-7.33). Mean hospital costs per patient were $45 709 in the preintervention group and $26 162 in the intervention group (P = .009). CONCLUSIONS: Integration of rapid identification and susceptibility techniques with antimicrobial stewardship significantly improved time to optimal therapy, and it decreased hospital length of stay and total costs. This innovative strategy has ramifications for other areas of patient care.

Donor-specific HLA-DQ antibodies may contribute to poor graft outcome after renal transplantation.

Increasing evidence suggests a detrimental effect of donor-specific antibodies directed against the human leukocyte antigen (HLA)-A, -B, and -DR loci on renal allograft outcomes. Limited data exist on the impact of de novo HLA-DQ antibodies. Over a 3-year period, we prospectively monitored 347 renal transplant recipients without pre-transplant donor-specific antibodies for their development de novo. After 26 months of follow-up, 62 patients developed donor-specific antibodies, of which 48 had a HLA-DQ antibody either alone (33 patients) or in combination with an HLA-A, -B, or -DR antibody (15 patients). Only 14 patients developed a donor-specific HLA-A, -B, or -DR antibody without a HLA-DQ antibody present. Acute rejection occurred in 21% of the HLA-DQ-only patients, insignificant when compared with 11% of patients without donor-specific antibodies. At the last follow-up, the mean serum creatinine and the fraction of patients with proteinuria were significantly higher in those that developed only HLA-DQ than those without antibodies. The 3-year graft survival was significantly worse when HLA-DQ antibodies were combined with non-DQ antibodies (52%) compared with HLA-DQ alone, non-DQ antibodies alone, or no antibodies (92-94%). Thus, our prospective monitoring study found that donor-specific HLA-DQ antibodies were the most common type detected and these antibodies may contribute to inferior graft outcomes. Ongoing surveillance is necessary to determine the long-term outcome of patients developing HLA-DQ donor-specific antibodies.

Strategy for rapid identification and antibiotic susceptibility testing of gram-negative bacteria directly recovered from positive blood cultures using the Bruker MALDI Biotyper and the BD Phoenix system.

Decreasing the time to species identification and antibiotic susceptibility determination of strains recovered from patients with bacteremia significantly decreases morbidity and mortality. Herein, we validated a method to identify Gram-negative bacteria directly from positive blood culture medium using the Bruker MALDI Biotyper and to rapidly perform susceptibility testing using the BD Phoenix.

Validation of the MycoAlign system for Mycobacterium spp. identification.

Validation of the MycoAlign assay, a newly developed Mycobacterium spp. identification system based on internal transcribed spacer-1 sequencing, was performed using 50 acid-fast bacilli (AFB)-positive clinical laboratory specimens. Forty-three (86%) diagnostic-level results were obtained, including 38 Mycobacterium spp. and 5 other AFB-positive genera. Three isolates (6%) had suboptimal identity scores with high probability (81-87% identity score). Four (8%) mixed-pattern results were obtained. Forty-five (90%) observations were concordant with the species identification by standard methods, including all controls.

Immunoglobulin therapy for plasma cell-rich rejection in the renal allograft.

Plasma cell-rich acute rejection (PCAR) is associated with poor allograft outcome in renal transplantation. Previous studies report a graft half-life of six months after a single PCAR episode. However, the management of this condition is unclear. Intravenous immunoglobulin (IVIG) therapy, by virtue of its immunomodulating properties, and its influence on B-cell maturation into plasma cells, may be a good candidate for reversing this type of rejection. We report four episodes of PCAR in two patients who responded well to IVIG with improvement in renal function.

Mycobacterial synovitis caused by slow-growing nonchromogenic species: eighteen cases and a review of the literature.

CONTEXT: Slow-growing nonchromogenic mycobacterial species are an infrequent cause of soft tissue infection. Because these organisms are rare, they are not often initially considered in the differential diagnosis of synovitis. OBJECTIVE: To evaluate the clinical and pathologic characteristics of patients with synovitis resulting from slow-growing nonchromogenic mycobacterial species. DESIGN: A 20-year retrospective review of records from The Methodist Hospital Microbiology Laboratory identified 18 culture-positive cases of synovitis that resulted from slow-growing nonchromogenic mycobacteria, including 14 caused by Mycobacterium avium complex, 1 caused by Mycobacterium malmoense, 1 caused by Mycobacterium haemophilum, and 2 caused by Mycobacterium nonchromogenicum isolates. In addition, a comprehensive literature search revealed an additional 48 cases of synovitis caused by slow-growing nonchromogenic mycobacteria. RESULTS: The historic literature described the majority of the 48 patients as previously healthy, elderly individuals with a several-month history of monoarticular pain and swelling in the small joints of the upper extremity. In contrast, the current series demonstrated the probable role of multiple chronic coexisting medical conditions in promoting disease susceptibility. These patients were also unique in their significantly younger age distribution and diversity of infection sites. Histologic examination and direct acid-fast bacteria stains generally did not aid the diagnosis. Amputation was performed in 2 patients because of delayed identification of disease. CONCLUSIONS: The current series demonstrates that difficult identification and infrequent occurrence cause these organisms to be overlooked by physicians and laboratory personnel. A heightened clinical suspicion for slow-growing nonchromogenic mycobacterial species is necessary when routine culture and histopathologic findings do not readily isolate an organism, or when the patient does not respond to antibiotic and anti-inflammatory treatment.

Impact of left ventricular assist device (LVAD)-mediated humoral sensitization on post-transplant outcomes.

BACKGROUND: Humoral sensitization, defined as a panel-reactive antibody (PRA) screen of >10%, places heart transplant recipients at a greater risk of acute rejection and mortality. Previous studies have suggested an increased sensitization in left ventricular assist device (LVAD) recipients, although neither the impact of device selection nor the clinical importance of elevated PRA in these patients has been completely described. METHODS: Using the registry of the International Society for Heart and Lung Transplantation (ISHLT), we compared PRA levels in 7,686 heart transplant recipients to determine the impact of LVAD therapy on humoral sensitization, acute rejection and mortality. To determine the impact of device selection on sensitization, we compared data from the ISHLT registry as well as from our own institution. RESULTS: Elevated PRA levels were found in 16.6% of LVAD recipients, compared with 7.6% of non-LVAD controls (p < 0.0001). Sensitization differed by device type, being present in 21.9% of Thoratec recipients, 14.4% of HeartMate recipients, and 15.5% of Novacor recipients (p = 0.01). Despite these findings, LVAD use had no impact on rejection rates. LVAD use was associated with a small increase (4.4% and 4.3%, respectively) in 1- and 2-year mortality. CONCLUSIONS: These findings support the concept that mechanical circulatory support increases the rate of humoral sensitization. However, these differences in sensitization do not translate to substantial differences in the clinical outcomes of rejection and mortality.

Characteristics of T-cell receptor repertoire and myelin-reactive T cells reconstituted from autologous haematopoietic stem-cell grafts in multiple sclerosis.

Multiple sclerosis is thought to involve aberrant immune responses to myelin autoantigens. Haematopoietic stem-cell transplantation (HSCT) is in clinical trials for progressive multiple sclerosis based on the rationale that it destroys aberrant immune system, while recapitulation of lymphocyte ontogeny might alter the immune system and slow down disease progression. This study was undertaken to analyse characteristics of the T-cell receptor (TCR) repertoire, serum cytokine profile and the T-cell responses to myelin basic protein (MBP) in the reconstituted immune system in progressive multiple sclerosis. The study revealed that, following autologous HSCT, the T-cell immunity recovered in two distinctive phases. The first phase was characterized by limited T-cell immunity as a result of selective expansion of pre-existing T cells commonly expressing the TCR beta chain variable region (TCR BV) 20 and increased serum cytokine production during the first several months. The second phase of T-cell reconstitution coincided with increased thymic T-cell output 9-12 months after HSCT. T cells reconstituted from stem-cell grafts had the distinctive properties of comprehensive T-cell immunity and a broad TCR repertoire. T cells recognizing MBP were initially depleted by immunoablation and rapidly expanded from the reconstituted T-cell repertoire in 12 months. The reconstituted MBP-reactive T cells exhibited a broader epitope recognition repertoire while maintaining the same skewed reactivity pattern compared with that seen at baseline. The findings have important implications in the understanding of the role of HSCT as a potential treatment for multiple sclerosis.