The timely detection of Methicillin-resistant Staphylococcus aureus (MRSA) is crucial for antimicrobial therapy and a key factor to limit the hospital spread of MRSA. Currently available commercial MRSA detection assays target the 3' end of the orfX gene and the right extremity of Staphylococcal Cassette Chromosome mec (SCCmec). These assays suffer from both false positive due to SCC-like elements that lack mecA and false negative results due to the inability to detect new or variant SCCmec cassettes with the existing primers. We developed a novel MRSA detection scheme, designed to circumvent issues present in the existing commercial assays. Our assay demonstrated specificity and accuracy, capable of detecting prototypic strains of SCCmec types I-XIII [C(t) values ranged 8.58-26.29]. Previous false positive isolates (N = 19) by Xpert MRSA nasal assay were accurately classified with our assay. Further validation with 218 randomly selected clinical isolates (73 MRSA, 75 MSSA, 43 MR-CoNS, and 27 MS-CoNS) confirmed its feasibility and practicality. Testing assay performance with 88 direct clinical swabs from 33 patients showed that the assay was 96.6% in agreement with clinical culture results. Our novel MRSA detection assay targets both the S. aureus specific sequence and the mecA/mecC genes simultaneously to overcome the false positive and false negative deficits of currently available commercial assays. The results validate our assay and confirmed its feasibility and practicality. The assay is not affected by SCCmec types and only needs modification if new mec homologs emerge and establishes a new platform for other emerging SCCmec types.
KEY POINTSA 50-year-old man presented to the emergency department with 3 days of acute severe chest pain that radiated to his back, subjective fever and decreased oral intake. He had a history of diabetes, hypertension and dyslipidemia, for which he was on metformin–sitagliptin, gliclazide,
Rabbit-anti-human T cell globulin (ATG) has the potential to decrease the likelihood of graft-vs-host disease (GVHD) or graft failure and to increase the likelihood of relapse or infections. After a given ATG dose, serum ATG levels are variable, presumably due to variable clearance. We determined ATG levels on day 7 and 28 in 160 recipients of allogeneic marrow or blood stem cells, whose conditioning included 4.5 mg/kg ATG (Thymoglobulin, Genzyme). Median follow up was 419 days (range, 14-1519). Patients with grade 2-4 acute GVHD as well as patients with extensive chronic GVHD had lower and patients with post-transplant lymphoproliferative disorder (PTLD) had higher median ATG levels on day 7 as well as day 28. In multivariate analysis, patients with day 7 ATG levels above 1.109 μg/ml had 0.38-fold risk of developing grade 2-4 acute GVHD compared to patients with lower ATG levels (p=0.02), patients with day 7 levels above 0.673 μg/ml had 0.44-fold risk of developing extensive chronic GVHD (p=0.009), and patients with day 7 ATG levels above 1.436 μg/ml had 8.30-fold risk of developing PTLD (p=.001). There was no association of either day 7 or day 28 ATG levels with relapse, non-PTLD infections or death. Association with graft failure could not be evaluated due to only 4 graft failures in the cohort. Patients with slow clearance of ATG have a low risk of acute and chronic GVHD but a high risk of PTLD.
Hematopoietic cell transplant (HCT) recipients are immunocompromised and thus predisposed to infections. We set out to determine the deficiency of which immune cell subset(s) may predispose to postengraftment infections. We determined day 28, 56, 84, and 180 blood counts of multiple immune cell subsets in 219 allogeneic transplant recipients conditioned with busulfan, fludarabine, and Thymoglobulin. Deficiency of a subset was considered to be associated with infections if the low subset count was significantly associated with subsequent high infection rate per multivariate analysis in both discovery and validation cohorts. Low counts of monocytes (total and inflammatory) and basophils, and low IgA levels were associated with viral infections. Low plasmacytoid dendritic cell (PDC) counts were associated with bacterial infections. Low inflammatory monocyte counts were associated with fungal infections. Low counts of total and naive B cells, total and CD56high natural killer (NK) cells, total and inflammatory monocytes, myeloid dendritic cells (MDCs), PDCs, basophils and eosinophils, and low levels of IgA were associated with any infections (due to any pathogen or presumed). In conclusion, deficiencies of B cells, NK cells, monocytes, MDCs, PDCs, basophils, eosinophils, and/or IgA plasma cells appear to predispose to postengraftment infections.
T cell expression of PD-1, a marker of functional exhaustion manifested by inability to produce cytokines upon stimulation, is upregulated in patients with acute graft-vs-host disease (GHVD). This is thought to explain at least in part why patients with acute GVHD have frequent infections. Here we wished to evaluate whether this is true also for chronic GVHD.
