POS1348 PATIENTS WITH VEXAS DIAGNOSED IN A DANISH TERTIARY RHEUMATOLOGY SETTING HAVE HIGHLY ELEVATED INFLAMMATORY MARKERS, MACROCYTIC ANEMIA, AND NEGATIVE AUTOIMMUNE BIOMARKERS

Background

VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome was described in 2020 with overlapping features of rheumatology and hematology. VEXAS is an autoinflammatory condition caused by somatic mutations in the UBA1 gene at methionine-41.

As patients present with highly variable clinical symptoms [1], their path in the clinical system is often complicated, and characterized by many strenuous examinations and biopsies. It is pivotal, that we familiarize with the VEXAS phenotype and advance identification of patients with VEXAS.

Objectives

We aimed to characterize patients diagnosed with VEXAS in a tertiary rheumatology referral center since December 2020 when the syndrome was described [2].

Methods

All patients were identified and diagnosed at the department of Rheumatology, Aarhus University Hospital (AUH), Denmark. Patients underwent testing for the UBA1 somatic mutations using sanger sequencing at the department of Clinical Immunology, AUH. Sequencing analyzed for somatic variants in/at exon 3 (NM_003334.4: c.118-1G>C, c.121A>C/G, c.122T>C og c.167C>T). Clinical and biochemical data were retrieved from the hospital electronic patient chart.

Continuous variables are presented as median with interquartile range (IQR) and categorical variables as percentages.

Results

A total of 11 male patients with clinical suspicion of VEXAS underwent sequencing. Five men were identified in the period December 2020 to December 2021 with UBA1 somatic mutations. Median age at diagnosis was 84 (75-87). Symptoms debuted on average 22 months (IQR 20-40) before diagnosis. All patients had significantly elevated markers of inflammation: median CRP 297 (196-386), IL-2-receptor, and ferritin and presented with macrocytic anemia. None of the patients were positive for autoimmune biomarkers like ANA, ACPA, MPO-, or PR3-ANCA.

Conclusion

This is, to the best of our knowledge, the first report of Danish patients with the VEXAS syndrome. Patients are males with persistent inflammation, constitutional symptoms, and heterogeneous clinical presentations.

Common features for all patients in this study were highly elevated inflammatory markers, macrocytic anemia, and negative autoimmune biomarkers.

References

[1]Georgin-Lavialle et al. Br J Dermaol. 2021 Oct 1. Online ahead of print

[2]Beck et al. N Engl J Med. 2020 Dec 31;383(27):2628-2638.

Table 1.

Clinical, biochemical characteristics at diagnosis and treatment of Danish VEXAS patients.

Patient 1Patient 2Patient 3Patient 4Patient 5Total n(%) or median (IQR)Clinical characteristicsAge at diagnosis738977848584 (75-87)Time from symptom onset till diagnosis (months)182147302222 (20-40)UBA1 variantc.122 T>C p.Met41Thrc.122 T>Cp.Met41Thrc.122 T>Cp.Met41Thrc.121 A>Cp.Met41Leuc.118-1 G>Cp.(splice)Macrocytic anemia+++++5 (100%)CRP(max, mg/ml)+(335)+(436)+(220)+(172)+ (297)5 (100%) (297 (196-386))Constitutional symptoms*+++++5 (100%)Vasculitis+++-+4 (80%)Chondritis--+-+2 (40%)Ocular inflammation--+--1 (20%)Arthritis+-++-3 (60%)Lung involvement-++++4 (80%)Proteinuria-++-+3 (60%)Thrombosis+--+-2 (40%)BM vacuoles-++NA-2/4 (50%)Biochemical characteristicsANA-----0 (0%)ACPANA---NA0 (0%)PR3 or MPO-ANCA-----0 (0%)

IQR: inter quartile range, BM: bone marrow, ANA: anti-nuclear antibodies, ACPA: anti-citrullinated protein antibody, PR3-ANCA: proteinase-3 anti-cytoplasmatic antibody, MPO: myeloperoxidase, NR: within normal range, NA: not available.*Constitutional symptoms (fever, night sweats, weight loss).

Disclosure of Interests

Mads Nyhuus Bendix Rasch Speakers bureau: Speakers fee in context of alignment meeting in autoinflammatory diseases by Sobi, Fruzsina Szabados: None declared, Jens Magnus Bernth Jensen: None declared, Kirstine Overgaard Nielsen: None declared, Ellen-Margrethe Hauge Speakers bureau: Has received fees for speaking and/or consulting from AbbVie, Sanofi, Sobi, MSD, UCB, Consultant of: Has received fees for speaking and/or consulting from AbbVie, Sanofi, Sobi, MSD, UCB, Grant/research support from: Research funding to Aarhus University Hospital from Novo Nordic Foundation, Danish Rheumatism Association, Danish Regions Medicine Grants, Roche, Novartis;, Anne Troldborg: None declared

POS0263 RE-VACCINATION COMPARED TO BOOSTER COVID-19 mRNA VACCINATION SIGNIFICANTLY INCREASES THE SEROLOGICAL RESPONSE IN RITUXIMAB-TREATED PATIENTS WITH INFLAMMATORY RHEUMATIC DISEASES WITHOUT A PRIMARY DETECTABLE SEROLOGICAL COVID-19 VACCINE RESPONSE

Background

Reports of an impaired humoral response after COVID-19 vaccination in patients treated with rituximab (RTX) have raised particular concern for patients with inflammatory rheumatic diseases (IRD) receiving RTX (1). This calls for strategies to enhance a humoral response in RTX-treated patients. At present, there is no data on whether it is best to increase the humoral response with a third vaccine dose (a booster) or with a third and fourth dose (re-vaccination).

Objectives

In IRD patients treated with RTX, without a detectable humoral response after the first vaccination course (two shots), we aimed to investigate the difference of either a booster vaccine (dose 3) or a new re-vaccination course (dose 3 + 4) on the serological response of the COVID-19 mRNA vaccines.

Methods

We included 84 patients with IRD treated with RTX, all without measurable total SARS-CoV-2 antibodies after a full primary COVID-19 vaccination course (2 doses three weeks apart). All patients were offered a new re-vaccination course with the mRNA vaccine not used primarily (Pfizer/Biontec or Moderna). A small number of patients declined the revaccination, and recieved a booster with the mRNA vaccine used initially. Serum total antibodies were measured before and six weeks after the last dose against recombinant SARS-CoV-2 spike S1 protein (VITROS). In addition, CD19+ B-cells were measured at inclussion.

Results

Patient characteristics are in Table 1. The median age was 64 years; 68% were female with a disease duration of 5 years. Sixty-nine out of 84 were re-vaccinated (3 + 4 dose). Details previous exposure to RTX are given in Table 1. CD19+ B-cells were measurable in 12/81 at inclusion.

Table 1.

Patient Characteristics

Booster, n=15Revaccination, n=69Age, years median (IQR)60 (45 - 69)65 (54 - 70)Female47%72%Disease duration, years (IQR)5 (2-8)6(2 - 13) ANCA-vasculitis47 %45 % Rheumatoid Arthritis47 %17 % Poly- Dermatomyositis6 %19 % SLE, Scleroderma, other diagnoses-19 %No DMARD treatment27 %35 %Prednisone33 %46 %Methotrexate40 %16 %Azathioprine7 %12 %Mycophenolate7 %7 %Other20 %9 %Rituximab treatment, (IQR) Months from last RTX to vaccination3.9 (1.3 - 9.3)5.4 (4.2 - 7.3) Number of infusions6 (4 - 8)7 (5 - 12) Cummulativ total dose, gram4 (2.5 - 7.5)6 (3.5 - 10) Total treatment time with RTX, months15 (9 - 54)27 (13 - 63)Patients with measurable CD19+ B-cells in peripheral blood at the time of booster or re-vaccination (positive/total)3/149/67

We found a combined seroconversion rate of 33% six weeks after the last shot. There was no statistical difference between the booster (38,5%) and the re-vaccination group (32,3%), p=0.67 (Pearson’s chi-squared). IRD patients with a humoral response in the re-vaccination group had significantly higher levels of total SARS-CoV-2 antibodies (median(IQR) 306(49-464) AU/ml) compared to the booster group (14(4-15) AU/ml) p=0.02, Figure 1A. In multiple logistic regression model, we found that levels of CD19+ B-cells were the only variable able to predict a humoral response, Figure 1B. However, only 39% of the patients with a humoral response to vaccination had measurable CD19+ B-cells before vaccination. We found no effect of age, sex, diagnosis, treatment, and RTX exposure on the chance of seroconversion in multiple logistic regression models when corrected for CD19+ B-cells.

Figure 1.

Conclusion

We found that re-vaccination (dose 3 + 4) with COVID-19 mRNA vaccines favored a high humoral response in patients with IRD treated with RTX, who did not have a detectable humoral response after the first two vaccine doses, compared to a booster shot (dose 3). A detectable humoral response after re-vaccination was seen in more than half of the patients with no measurable CD19+ B-cells before vaccination. Presence of circulating CD19+ B-cells are a significant predictor of humoral response to mRNA COVID-19 vaccination.

References

[1]Ammitzbøll et al. ACR Open Rheum. 2021 Sep;3(9):622-628. doi: 10.1002/acr2.11299.

Acknowledgements

The Danish Rheumatism Association - Gigtforeningen for funding the study.

Disclosure of Interests

None declared

Effects of a Cognitive Training With and Without Additional Physical Activity in Healthy Older Adults: A Follow-Up 1 Year After a Randomized Controlled Trial

Background: Combining cognitive training (CT) with physical activity (CPT) has been suggested to be most effective in maintaining cognition in healthy older adults, but data are scarce and inconsistent regarding long-term effects (follow-up; FU) and predictors of success.

Objective: To investigate the 1-year FU effects of CPT versus CT and CPT plus counseling (CPT+C), and to identify predictors for CPT success at FU.

Setting and Participants: We included 55 healthy older participants in the data analyses; 18 participants (CPT group) were used for the predictor analysis.

Interventions: In a randomized controlled trial, participants conducted a CT, CPT, or CPT+C for 7 weeks.

Outcome Measures: Overall cognition, verbal, figural, and working memory, verbal fluency, attention, planning, and visuo-construction.

Results: While within-group comparisons showed cognitive improvements for all types of training, only one significant interaction Group × Time favoring CPT in comparison to CPT+C was found for overall cognition and verbal long-term memory. The most consistent predictor for CPT success (in verbal short-term memory, verbal fluency, attention) was an initial low baseline performance. Lower education predicted working memory gains. Higher levels of insulin-like growth factor 1 (IGF-1) and lower levels of brain-derived neurotrophic factor at baseline (BDNF) predicted alternating letter verbal fluency gains.

Discussion: Within-group comparisons indicate that all used training types are helpful to maintain cognition. The fact that cognitive and sociodemographic data as well as nerve growth factors predict long-term benefits of CPT contributes to the understanding of the mechanisms underlying training success and may ultimately help to adapt training to individual profiles.

Clinical Trial Registration: WHO ICTRP (http://apps.who.int/trialsearch/), identifier DRKS00005194.

Identification of the flotillin-1/2 heterocomplex as a target of autoantibodies in bona fide multiple sclerosis

BACKGROUND

Autoantibodies, in particular those against aquaporin-4 and myelin-oligodendrocyte glycoprotein (MOG), aid as biomarkers in the differential diagnosis of demyelination. Here, we report on discovery of autoantibodies against flotillin in patients with multiple sclerosis (MS).

METHODS

The target antigen was identified by histo-immunoprecipitation using the patients' sera and cryosections of rat or pig cerebellum combined with mass spectrometrical analysis. Correct identification was ascertained by indirect immunofluorescence and neutralization tests using the target antigens recombinantly expressed in HEK293 cells.

RESULTS

Serum and CSF of the index patient produced a fine-granular IgG indirect immunofluorescence staining of the hippocampal and cerebellar molecular layers. Flotillin-1 and flotillin-2 were identified as target autoantigens. They also reacted with recombinant human flotillin-1/2 co-expressed in HEK293 cells, but not with the individual flotillins in fixed- and live-cell assays. Moreover, neutralization using flotillin-1/2, but not the single flotillins, abolished the tissue reactivity of patient serum. Screening of 521 patients, for whom anti-aquaporin-4 testing was requested and negative, revealed 8 additional patients with anti-flotillin-1/2 autoantibodies. All eight were negative for anti-MOG. Six patients ex post fulfilled the revised McDonald criteria for MS. Vice versa, screening of 538 MS sera revealed anti-flotillin-1/2 autoantibodies in eight patients. The autoantibodies were not found in a cohort of 67 patients with other neural autoantibody-associated syndromes and in 444 healthy blood donors.

CONCLUSIONS

Autoantibodies against the flotillin-1/2 heterocomplex, a peripheral membrane protein that is involved in axon outgrowth and regeneration of the optic nerve, are present in 1-2% of patients with bona fide MS.

Cognitive training with and without additional physical activity in healthy older adults: cognitive effects, neurobiological mechanisms, and prediction of training success

Data is inconsistent concerning the question whether cognitive-physical training (CPT) yields stronger cognitive gains than cognitive training (CT). Effects of additional counseling, neurobiological mechanisms, and predictors have scarcely been studied. Healthy older adults were trained with CT (n = 20), CPT (n = 25), or CPT with counseling (CPT+C; n = 23). Cognition, physical fitness, BDNF, IGF-1, and VEGF were assessed at pre- and post-test. No interaction effects were found except for one effect showing that CPT+C led to stronger gains in verbal fluency than CPT (p = 0.03). However, this superiority could not be assigned to additional physical training gains. Low baseline cognitive performance and BDNF, not carrying apoE4, gains in physical fitness and the moderation of gains in physical fitness × gains in BDNF predicted training success. Although all types of interventions seem successful to enhance cognition, our data do not support the hypotheses that CPT shows superior CT gains compared to CT or that CPT+C adds merit to CPT. However, as CPT leads to additional gains in physical fitness which in turn is known to have positive impact on cognition in the long-term, CPT seems more beneficial. Training success can partly be predicted by neuropsychological, neurobiological, and genetic parameters. Unique Identifier: WHO ICTRP (http://www.who.int/ictrp); ID: DRKS00005194.

Multiresistant strains are as susceptible to photodynamic inactivation as their naïve counterparts: protoporphyrin IX-mediated photoinactivation reveals differences between methicillin-resistant and methicillin-sensitive Staphylococcus aureus strains

OBJECTIVE

The current study was aimed at the investigation of differences in response to photoinactivation between methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) isolates. Moreover, we aimed to elucidate if the observed variation resulted from antimicrobial resistance mechanisms and strains' susceptibility to antibiotic therapy.

BACKGROUND DATA

Because of the emergence of multidrug resistance, the development of alternative antimicrobial strategies seems to be required. The concept of photodynamic inactivation (PDI) involves cell exposure to appropriate wavelength light that leads to the excitation of photosensitizer molecules, resulting in the production of reactive oxygen species responsible for cell inactivation and death. Recently, we have demonstrated a strain-dependent response of S. aureus to photoinactivation, and observed elevated resistance to PDI among MRSA strains. Nevertheless, the mechanism underlying this phenomenon remains unexplained.

METHODS

S. aureus response to protoporphyrin IX (PPIX)-mediated photoinactivation was studied for 424 MRSA/MSSA isolates. VITEK 2 Advanced Expert System was used to detect antimicrobial resistance mechanisms and strains' susceptibility to antibiotictherapy.

RESULTS

Data obtained demonstrated that MRSA are significantly more resistant to photoinactivation than MSSA strains; however, the difference observed did not result from antimicrobial susceptibility or resistance mechanisms. Furthermore, regardless of the strains' origin, a similar effectiveness of PDI could be achieved. Moreover, it was determined that the ability to form biofilms in vitro, and the presence of mec element, does not explain the observed differences between MRSA and MSSA strains.

CONCLUSIONS

PDI could be highly effective against multidrug resistant pathogens as well as their naïve counterparts. Nevertheless, regardless of the antimicrobial resistance mechanism, the difference in response to PDI between MRSA and MSSA exists.

The major autolysin of Staphylococcus lugdunensis, AtlL, is involved in cell separation, stress-induced autolysis and contributes to bacterial pathogenesis

Staphylococcus lugdunensis is a human skin commensal organism, but it is considered as a virulent Staphylococcus species. In a previous study, we described the first S. lugdunensis autolysin, AtlL. This enzyme displays two enzymatic domains and generates two peptidoglycan hydrolases, an N-acetylmuramoyl-l-alanine amidase and an N-acetylglucosaminidase. In this study, to further investigate the functions of this autolysin, a ΔatlL mutant was constructed. The microscopic examination of the mutant showed cell aggregates and revealed a rough outer cell surface demonstrating, respectively, the roles of AtlL in cell separation and peptidoglycan turnover. This ΔatlL mutant exhibited a lower susceptibility to Triton X-100-induced autolysis assays and appears to be more resistant to cell wall antibiotic-induced lysis and death compared with its parental strain. The atlL mutation affected the biofilm formation capacity of S. lugdunensis. Furthermore, the ΔatlL mutant showed trends toward reduced virulence using the Caenorhabditis elegans model. Overall, AtlL appears as a major cell wall autolysin of S. lugdunensis implicated in cell separation, in stress-induced autolysis and in bacterial pathogenesis.

Staphylococcus saprophyticus surface-associated protein (Ssp) is associated with lifespan reduction in Caenorhabditis elegans

Staphylococcal lipases have been proposed as pathogenicity factors. In Staphylococcus saprophyticus the surface-associated protein (Ssp) has been previously characterized as a cell wall-associated true lipase. A S. saprophyticus Δssp::ermB mutant has been described as less virulent in an in vivo model of urinary tract infection compared with its wild-type. This is the first report showing that S. saprophyticus induced a lifespan reduction in Caenorhabditis elegans similar to that of S. aureus RN4220. In two S. saprophyticus Δssp::ermB mutants lifespan reduction in C. elegans was partly abolished. In order to attribute virulence to the lipase activity itself and distinguish this phenomenon from the presence of the Ssp-protein, the conserved active site of the lipase was modified by site-directed ligase-independent mutagenesis and lipase activity-deficient mutants were constructed. These results indicate that the Ssp is associated with pathogenicity in C. elegans and one could speculate that the lipase activity itself is responsible for this virulence.

First description of Escherichia coli producing CTX-M-15- extended spectrum beta lactamase (ESBL) in out-patients from south eastern Nigeria

We studied the presence of extended spectrum beta lactamases (ESBLs) in 44 clinical isolates of Escherichia coli collected from out-patients in two university teaching hospitals in South-Eastern Nigeria. Species identification was performed by standard microbiology methods and re-confirmed by MALDI-TOF technology. Phenotypic characterization of ESBL enzymes was done by double disc synergy test and presence of ESBL genes was determined by specific PCR followed by sequencing. Transfer of plasmid DNA was carried out by transformation using E. coli DH5 as recipient strain. Phenotypic characterization identified all isolates to be ESBL positive. 77% of strains were from urine, 13.6% from vaginal swabs and 9.0% from wound swabs. 63.6% were from female patients, 68% were from outpatients and 95.5% from patients younger than 30 years. All ESBL producers were positive in a PCR for bla_CTX-M-1 cluster, in exemplary strains bla_CTX-M-15 was found by sequencing. In all strains ISEcp1 was found upstream and ORF477 downstream of bla_CTX-M. PCR for bla_TEM and bla_OXA-1 was positive in 93.1% of strains, whereas bla_SHV was not detected, aac(6′)-Ib-cr was found in 97.7% of strains. RAPD analysis revealed seven different clonal groups named A through G with the majority of the strains (65.9%) belonging to clone A. Transfer of an ESBL plasmid with co-resistance to gentamicin, kanamycin, tobramycin, doxycycline and trimethropim-sulfamethoxazole was successful in 19 (43.2%) strains. This study showed a high rate of CTX-M-1 cluster - ESBLs in South-Eastern Nigeria and further confirms the worldwide spread of CTX-M ESBL in clinical isolates.

Construction and characterization of three knockout mutants of the fbl gene in Staphylococcus lugdunensis

Staphylococcus lugdunensis is an important human pathogen that causes infectious diseases similar to those caused by Staphylococcus aureus. In contrast to S. aureus, only a very few pathogenicity factors of S. lugdunensis have been characterized. Notably, a genetic manipulation of S. lugdunensis has not yet been described. Ours is the first report where transformation of three different plasmids (pBT2, pRB473, and pT181) into S. lugdunensis and a directed genetic manipulation of S. lugdunensis are described. We constructed fbl knockout mutants from three different strains of S. lugdunensis to show that at least in these strains, the fibrinogen binding is exclusively mediated by Fbl.

The sensitivity of direct identification from positive BacT/ALERT™ (bioMérieux) blood culture bottles by matrix-assisted laser desorption ionization time-of-flight mass spectrometry is low

Recently, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been presented as a novel method for the direct identification of bacteria from positive blood culture bottles. The rate of the MALDI TOF MS-based identification in the present study from positive BacT/ALERT (bioMérieux, Marcy l'Etoile, France) blood culture bottles was 30%, which is far below the previously reported sensitivities using the BACTEC (Becton Dickinson, Franklin Lakes, NJ, USA) system. We also found evidence that the Biotyper algorithm did not identify a second pathogen in cases of positive BacT/ALERT blood culture bottles containing two different species.

Occurrence of genes of putative fibrinogen binding proteins and hemolysins, as well as of their phenotypic correlates in isolates of S. lugdunensis of different origins

Background

Staphylococcus lugdunensis is an important human pathogen that causes potentially fatal endocarditis, osteomyelitis and skin and soft tissue infections similar to diseases caused by Staphylococcus aureus. Nevertheless, in contrast to S. aureus, data on pathogenicity factors of S. lugdunensis is scarce. Two adhesins, a fibrinogen and a von Willebrand factor binding protein, and a S. lugdunensis synergistic hemolysin (SLUSH) have been previously described. Moreover, the newly sequenced genome of S. lugdunensis revealed genes of other putative fibrinogen binding adhesins and hemolysins. The aim of this study was to gain more insight into the occurrence of genes likely coding for fibrinogen binding adhesins and hemolysins using clinical strains of S. lugdunensis.

Findings

Most of the putative adhesin genes and hemolysin genes investigated in this study were highly prevalent, except for the SLUSH gene cluster. In contrast to previous reports, binding to fibrinogen was detected in 29.3% of the S. lugdunensis strains. In most strains, hemolysis on blood agar plates was weak after 24 h and distinct after 48 h of incubation. The fibrinogen binding and hemolysis phenotypes were also independent of the type of clinical specimen, from which the isolates were obtained.

Conclusion

In this study we described a pyrrolidonyl arylamidase negative S. lugdunensis isolate. Our data indicate that a matrix-assisted laser desorption ionisation time-of-flight MS-based identification of S. lugdunensis or species-specific PCR's should be performed in favour of pyrrolidonyl arylamidase testing. In contrast to the high occurrence of putative fibrinogen binding protein genes, 29.3% of the S. lugdunensis strains bound to fibrinogen. Putative hemolysin genes were also prevalent in most of the S. lugdunensis strains, irrespective of their hemolysis activity on Columbia blood agar plates. Similar to a previous report, hemolysis after 48 h of incubation is also indicative for S. lugdunensis. The SLUSH gene cluster was detected in an estimated 50% of the strains, indicating that this locus is different or non-prevalent in many strains.

Vancomycin MIC creep in MRSA blood culture isolates from Germany: a regional problem?

The aim of this study was to assess the vancomycin MIC distribution for MRSA blood culture isolates over a period of six years in Germany. The study examined 287 MRSA isolates from blood cultures collected at several hospitals in two German cities between 2004 and 2009. The vancomycin MIC was determined by Etest. Genotypic features of the MRSA strains with vancomycin MIC ≥ 1 mg/L were determined by semiautomated repetitive-sequence-based polymerase chain reaction. The range of vancomycin MIC as determined by Etest was 0.25 to 2.0 mg/L. The geometric mean MIC increased by 1.34-fold in city A over the study period (p < 0.05), but there was no meaningful change in city B (a 1.09-fold increase, p > 0.05). Furthermore, in city A a shift in vancomycin MICs occurred as an increase in the percentage of isolates with MIC ≥ 1 mg/L from period one (2004-2006) to period two (2007-2009) (p < 0.0001). Typing results showed that in city A a single clone was predominant (55% of the creep isolates). In this study, the creep phenomenon seems to be a regional problem. We suggest that all hospitals should monitor their local status of elevated vancomycin MICs in invasive MRSA isolates.

False-negative test results in the Slidex Staph Plus (bioMérieux) agglutination test are mainly caused by spa-type t001 and t001-related strains

The relative sensitivity of commercial agglutination kits for fast identification of S. aureus is usually given to be about 98%. This reported sensitivity has sometimes been questioned. In this study, three collections of molecularly defined, single-copy strains of S. aureus were used to compare the sensitivities of agglutination-based identification and the MALDI-TOF mass spectrometry-based identification using the Biotyper 2.0 database to a molecularly defined reference method. Clinical isolates (n = 363) of methicillin-susceptible S. aureus (MSSA) and 240 clinical isolates of methicillin-resistant S. aureus (MRSA) were included. In order to rule out a predominance of local MRSA-strains, a collection of 104 pulsed-field-gel electrophoresis divergent MRSA strains were also tested. MALDI-TOF MS using Biotyper database (Bruker) identified all isolates, whereas the Slidex Staph Plus (bioMérieux) detected only 98.0% of the MSSA, 94.5% of the MRSA and only 70.1% of the MRSA of the molecularly divergent strain collection. Interestingly, strains with a false-negative test result in the agglutination methods were mostly spa-type t001 and t001 related. The MALDI-TOF MS based identification can thus be used as an alternative identification method for suspected false-negative results from the agglutination tests, especially if the local prevalence of t001 and t001 related strains is high.

The matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS)-based protein peaks of 4448 and 5302 Da are not associated with the presence of Panton-Valentine leukocidin

The Panton-Valentine leukocidin (PVL) of Staphylococcus aureus plays an important role in the pathogenesis of necrotizing pneumonia and recurrent skin and soft tissue infections. The gene encoding for PVL, lukS/F-PV, is distributed by prophages and can thus spread between isolates. Molecular methods have normally been used to identify lukS/F-PV-positive strains. Recently, however, a matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS)-based method has been described to identify PVL-positive S. aureus strains. The aim of this study was thus to investigate the association of distinct MALDI-TOF MS peaks to the toxin profile in molecularly characterized methicillin-susceptible (MSSA) and methicillin-resistant S. aureus (MRSA) strains harbouring lukS/F-PV. In contrast to the previous results, the MALDI-TOF MS peaks were detected in all 104 recently described molecularly divergent MRSA irrespective of the presence of PVL. Our result indicates that these described peaks seem to be independent of the presence of PVL.

Identification of molecularly defined Staphylococcus aureus strains using matrix-assisted laser desorption/ionization time of flight mass spectrometry and the Biotyper 2.0 database

Matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) has recently been introduced for bacterial identification. To our knowledge, this is the first study where the Biotyper 2.0 database (Bruker Daltonics) has been applied for bacterial identification in a local strain collection of molecularly defined Staphylococcus aureus. We showed that the accuracy of the Biotyper 2.0-based identification for 602 molecularly defined strains of S. aureus, irrespective of meticillin resistance, was equivalent to that of the molecularly defined reference even at a score cut-off value of 2. Also, 412 isolates of 20 different species of non-S. aureus staphylococci were all correctly identified to species level compared to the molecularly defined reference. Moreover, the MALDI-TOF MS-based S. aureus identification approach was clearly faster than more time-consuming methods such as a molecular identification approach.

Comparison of phenotypic methods for penicillinase detection in Staphylococcus aureus

Penicillinase testing is required for Staphylococcus aureus isolates with a penicillin MIC of </=0.12 mg/L. This study compared five phenotypic assays with a PCR for blaZ when testing 197 S. aureus isolates. The starch-iodine plate method and nitrocefin tests had low sensitivities of 42.9% and 35.7%, respectively. The cloverleaf assay and the penicillin zone-edge determination method had sensitivities of 67.8% and 71.4%, respectively, and these methods might be appropriate in many circumstances, but were not as sensitive as blaZ PCR.

Influence of cardiac resynchronisation therapy on different types of sleep disordered breathing

AIMS

This study investigates the influence of cardiac resynchronisation therapy (CRT) on sleep disordered breathing (SDB) in patients with severe heart failure (HF).

METHODS AND RESULTS

Seventy-seven patients with HF (19 females; 62.6+/-10 years) eligible for CRT were screened for presence, type, and severity of SDB before and after CRT initiation (5.3+/-3 months) using cardiorespiratory polygraphy. NYHA class, frequency of nycturia, cardiopulmonary exercise, 6-minute walking test results, and echocardiography parameters were obtained at baseline and follow-up. Central sleep apnoea (CSA) was documented in 36 (47%), obstructive sleep apnoea (OSA) in 26 (34%), and no SDB in 15 (19%) patients. CRT improved clinical and haemodynamic parameters. SDB parameters improved in CSA patients only (apnoea hypopnoea index: 31.2+/-15.5 to 17.3+/-13.7/h, p<0.001; SaO2min: 81.8+/-6.6 to 84.8+/-3.3%, p=0.02, desaturation: 6.5+/-2.3 to 5.5+/-0.8%, p=0.004). Daytime capillary pCO2 was significantly lower in CSA patients compared to those without SDB with a trend towards increase with CRT (35.5+/-4.2 to 37.9+/-5.7 mm Hg, ns). After classifying short term clinical and haemodynamic CRT effects, improved SDB parameters in CSA occurred in responders only.

CONCLUSIONS

In patients with severe HF eligible for CRT, CSA is common and can be influenced by CRT, this improvement depends on good clinical and haemodynamic response to CRT.

Clinical outcome of heart transplant recipients receiving tacrolimus with or without mycophenolate mofetil

Tacrolimus (TAC) is a calcineurin inhibitor that is used for cardiac allograft rejection. Efficacy and safety data of a combined TAC/mycophenolate mofetil (MMF) therapy in comparison with a TAC/cortisone therapy in heart recipients are lacking. We analysed the clinical outcome of 41 patients who received TAC in combination with MMF (TMF group) and of 41 patients who received TAC in combination with cortisone (TCO group). Outcomes were serum creatinine levels, cardiac rejections, cytomegalovirus infections, graft vasculopathy, malignancy rates and two-yr survival. Baseline characteristics were comparable in the two study groups. During follow-up, serum creatinine levels decreased slightly in the TMF group (p=0.039) but not in the TCO group. Compared with the TMF group, more clinically proven cardiac rejections which needed a cortisone bolus and more severe rejections that needed lymphoablative therapy with OKT occurred in the TCO group (p=0.001 and 0.04, respectively). In contrast, significantly more cytomegalovirus (CMV) infections occurred in the TMF group compared with the TCO group (p=0.01). The number of patients with graft vasculopathy as well as malignancy rates and overall survival did not differ significantly between the two study groups. The introduction of MMF was associated with an improvement of renal function and a more efficient immunosuppressive therapy. However, this treatment strategy also had led to a higher CMV infection rate compared with cortisone. Consequently, no general recommendation can be given at present whether TAC should be combined with MMF or with cortisone in heart transplant recipients.

Tropheryma whipplei Infection of an acellular porcine heart valve bioprosthesis in a patient who did not have intestinal Whipple's disease

Rare cases of culture-negative infective endocarditis are caused by Tropheryma whipplei, the uncommon bacterium of Whipple's disease. We evaluated an 80-year-old woman with valvular heart disease but without intestinal Whipple's disease. The diagnosis of aortic valve xenograft culture-negative infection with T. whipplei was established by multiple molecular assays and by electron microscopy. First, a PCR with broad-range primers identified the complete 16S ribosomal DNA of T. whipplei in bioprosthesis tissue. Novel real-time reverse transcription-PCR assays were developed to detect mRNAs encoding recently identified proteins determined from the T. whipplei genome, specifically Whipplei surface protein (TW113) and a DNA polymerase III subunit (TW727). The positive detection of mRNAs indicated the presence of metabolically active bacteria and suggested the viability of T. whipplei. The quantification of T. whipplei genome equivalents by real-time PCR indicated a high-density bacterial colonization of the valve tissue. Additionally, an ultrastructural examination revealed numerous rod-shaped bacteria consistent in size with T. whipplei in the extracellular collagen matrix of the bioprosthesis. We conclude that extracellular growth of T. whipplei can occur in the microenvironment of biological prosthetic valve tissue and that T. whipplei endocarditis can occur in the absence of intestinal Whipple's disease.