Bjorn L. Herpers

Complement activity is associated with disease severity in multifocal motor neuropathy

Objective: To investigate whether high innate activity of the classical and lectin pathways of complement is associated with multifocal motor neuropathy (MMN) and whether levels of innate complement activity or the potential of anti-GM1 antibodies to activate the complement system correlate with disease severity. Methods: We performed a case-control study including 79 patients with MMN and 79 matched healthy controls. Muscle weakness was documented with Medical Research Council scale sum score and axonal loss with nerve conduction studies. Activity of the classical and lectin pathways of complement was assessed by ELISA. We also determined serum mannose-binding lectin (MBL) concentrations and polymorphisms in the MBL gene (MBL2) and quantified complement-activating properties of anti-GM1 IgM antibodies by ELISA. Results: Activity of the classical and lectin pathways, MBL2 genotypes, and serum MBL concentrations did not differ between patients and controls. Complement activation by anti-GM1 IgM antibodies was exclusively mediated through the classical pathway and correlated with antibody titers (p < 0.001). Logistic regression analysis showed that both high innate activity of the classical pathway of complement and high complement-activating capacity of anti-GM1 IgM antibodies were significantly associated with more severe muscle weakness and axonal loss. Conclusion: High innate activity of the classical pathway of complement and efficient complement-activating properties of anti-GM1 IgM antibodies are determinants of disease severity in patients with MMN. These findings underline the importance of anti-GM1 antibody–mediated complement activation in the pathogenesis and clinical course of MMN.

Mannose-binding lectin (MBL2) and ficolin-2 (FCN2) polymorphisms in patients on peritoneal dialysis with staphylococcal peritonitis

BACKGROUND Mannose-binding lectin (MBL) and ficolin-2 (FCN) are activators of the lectin pathway of complement and act as primary defences against infection. Single-nucleotide polymorphisms (SNPs) in the MBL2 and FCN2 genes influence the functionality of the proteins. Both proteins are capable of binding staphylococci, which are pathogens that frequently cause peritonitis in patients on continuous ambulatory peritoneal dialysis (CAPD). We studied the role of polymorphisms in the MBL2 and FCN2 genes as a risk factor for developing CAPD peritonitis caused by staphylococci. METHODS We analysed SNPs in the MBL2 and FCN2 genes in 40 CAPD patients with staphylococcal peritonitis and in 65 CAPD patients without any history of peritonitis. Additionally, we analysed the prevalence of exit site infections and nasal Staphylococcus aureus carriage in both groups. RESULTS The + 6359C > T SNP leading to the Thr236Met amino acid alteration in the FCN2 gene, associated with decreased substrate binding, was significantly more prevalent in CAPD patients with a history of staphylococcal peritonitis compared with patients on CAPD without a history of peritonitis (P = 0.037). No difference was found in MBL2 genotypes between the two groups. In CAPD patients with a history of staphylococcal peritonitis, exit site infection with S. aureus was also more prevalent (P < 0.01), while S. aureus carriage was not (P = 0.073). CONCLUSIONS In addition to known risk factors such as exit site infection, the + 6359C > T SNP in the FCN2 gene might be a risk factor for staphylococcal peritonitis in CAPD patients due to decreased binding of FCN to staphylococci.

Hemolytic assay for the measurement of functional human mannose-binding lectin: A modification to avoid interference from classical pathway activation

Diagnostic assays for measurement of functional mannose-binding lectin (MBL) in serum are widely performed as part of immune status assessment. Classical pathway mediated complement activity can interfere in these functional MBL assays. Here we describe classical pathway interference incidentally occurring in a previously described hemolytic MBL assay and the modification of this assay to prevent this artifact by addition of anti-C1q antibodies. Classical pathway interference in functional MBL assays can and should be inhibited to prevent that MBL deficiency is overlooked and patients are misdiagnosed.

Costs and Benefits Associated with the MRSA Search and Destroy Policy in a Hospital in the Region Kennemerland, The Netherlands

Objective The objective of this study was to analyze the costs and benefits of the MRSA Search and Destroy (S&D) policy between 2008 and 2013 in the Kennemer Gasthuis, a 400 bed teaching hospital in the region Kennemerland, the Netherlands. Methods A patient registration database was used to retrospectively calculate costs, including screening, isolation, follow-up, contact tracing, cleaning, treatment, deployment of extra healthcare workers, salary for an infection control practitioner (ICP) and service of isolation rooms. The estimated benefits (costs and lives when no MRSA S&D was applied) were based on a varying MRSA prevalence rate (up to 50%). Results When no MRSA S&D policy was applied, the additional costs and deaths due to MRSA bacteraemia were estimated to be € 1,388,907 and 33 respectively (at a MRSA prevalence rate of 50%). Currently, the total costs were estimated to be € 290,672 (€ 48,445 annually) and a MRSA prevalence rate of 17.3% was considered as break-even point. Between 2008 and 2013, a total of 576 high risk patients were screened for MRSA carriage, of whom 19 (3.3%) were found to be MRSA positive. Forty-nine patients (72.1%) were found unexpectedly. Conclusions Application of the MRSA S&D policy saves lives and money, although the high rate of unexpected MRSA cases is alarming.

Rapid antigen test for pandemic (H1N1) 2009 virus.

To the Editor: Drexler et al. recently compared the sensitivity of the BinaxNOW Influenza A & B Rapid Test (BinaxNOW; Inverness Medical, Cologne, Germany) with that of a real-time reverse transcription–PCR (RT-PCR) assay specific for influenza A pandemic (H1N1) 2009 virus (1). Of 1,838 clinical specimens tested, 221 were confirmed as positive for pandemic (H1N1) 2009 by RT-PCR. When 144 of these 221 specimens were evaluated by using the BinaxNOW, results were positive for only 16 (11%). At onset of the pandemic, we evaluated the first 135 nasopharyngeal aspirates submitted to the Regional Laboratory of Public Health Haarlem, the Netherlands. We compared the performance of the BinaxNOW for diagnosing influenza A (H1N1) virus by using molecular detection of influenza virus as the reference standard. Samples were analyzed with a general influenza A assay targeting the matrix gene (the RespiFinder assay) (PathoFinder B.V., Maastricht, the Netherlands [2]) and a pandemic (H1N1) 2009–specific RT-PCR assay targeting the neuraminidase gene (3). We tested 135 patient samples (76 from male patients); mean age of patients was 32 years (range 0–81 years). Samples from 38 (28%) patients had positive results in both RT-PCRs, and samples from 97 (72%) patients had negative results in the matrix gene RT-PCR and neuraminidase RT-PCR assays. Sensitivity and specificity were estimated to be 47% (18/38, 95% confidence interval [CI] 32%–62%) and 95% (92/97, 95% CI 88%–98%), respectively, for the BinaxNOW antigen test. Patients’ ages did not significantly differ between rapid test–positive and –negative results. Our results largely agree with those of Vasoo et al. (4) and the Centers for Disease Control and Prevention (5). Those studies determined that the sensitivity of the BinaxNOW compared with nucleic acid amplification tests is ≈40%. The lower sensitivity observed by Drexler et al. (1) might be because of differences in study type (retrospective evaluation compared with a prospective cohort in our study), sample size, technical factors (with regard to specimen collection, specimen transport, and specimen storage), differences in the test kit, and differences between individual patients (multiple categories of age and stages of illness, differences in virus shedding). Many clinicians are not aware of the performance of specific test devices and rely on test results to make clinical decisions. Because negative results cannot rule out influenza, this test is of little use in a clinical setting without appreciation of the limitations of the test. However, because the BinaxNOW has reasonable specificity, it might prove useful in clinical or epidemiologic situations in which test sensitivity is not critical, e.g., in facility outbreaks in which multiple specimens are collected to rapidly identify the causative organism.

Deficient mannose-binding lectin-mediated complement activation despite mannose-binding lectin–sufficient genotypes in an outbreak of Legionella pneumophila pneumonia

Polymorphisms leading to deficiency of mannose-binding lectin (MBL) are associated with predisposition to infection. However, MBL deficiency can be protective against intracellular pathogens that use MBL to enter host cells. The role of MBL genotype and activity in infection with the intracellular pathogen Legionella pneumophila was studied in a large outbreak of legionellosis at a Dutch flower show. A total of 141 patients, 65 exposed asymptomatic exhibition staff members and 670 unexposed blood bank donors were included for the study of MBL2 genotypes and MBL-mediated complement activation. Genotypic MBL deficiency was equally prevalent in patients and controls. Deficient MBL-mediated complement activation was more prevalent in patients. Even in patients with genotypes that confer MBL sufficiency, 20.6% lacked MBL-mediated complement activation. In most patients with MBL-sufficient genotypes who lacked MBL-mediated activation at the acute phase of disease, lectin pathway functionality was restored at convalescence. In conclusion, genotypic MBL deficiency was not a risk factor for legionellosis. However, patients with legionellosis displayed deficient MBL-mediated complement activation even with MBL-sufficient genotypes. Together, these genotypical and functional data suggest that the observed deficiency of lectin pathway activation is an effect of legionellosis rather than a risk factor for acquiring it.

Clinical sensitivity and specificity of the Check-Points Check-Direct ESBL Screen for BD MAX, a real-time PCR for direct ESBL detection from rectal swabs

Objectives: To determine the diagnostic accuracy of the Check‐Direct ESBL Screen for BD MAX (ESBL qPCR) and an ESBL culture method to identify ESBLs directly from rectal swabs. Methods: Rectal swabs were obtained from clinical patients by performing cross‐sectional (point)prevalence measurements in three regional hospitals. Rectal swabs were analysed by direct culture (ChromID ESBL agar) and with the ESBL qPCR. Suspected ESBL‐producing isolates were confirmed with the combination disc method and analysed by WGS. Results: Out of 354 rectal swabs and 351 patients, 21 rectal swabs and 20 patients were positive for ESBL‐producing isolates, resulting in a regional ESBL colonization prevalence of 5.7%. One rectal swab was false negative with the ESBL qPCR (blaTEM‐12) and not covered by the ESBL qPCR. Eight ESBL qPCR‐positive rectal swabs could not be confirmed by culture and were classified as false ESBL qPCR positive. The sensitivity and specificity of the ESBL qPCR were 95.2% (n = 20) and 97.6% (n = 323), respectively. When an optimal cycle threshold cut‐off value of 37 was used, the ESBL qPCR displayed a sensitivity and specificity of 95.2% (n = 20) and 98.8% (n = 327), respectively (AUC = 0.975, 95% CI = 0.922–1). Conclusions: This ESBL qPCR offers rapid direct detection of the most prevalent ESBL types (blaCTX‐M group and blaSHV group) from rectal swabs. The relatively high false‐positive rate renders this test the most suitable as a screening test in high‐prevalence regions or in an outbreak setting where a fast result is essential.

Classical and lectin complement pathway activity in polyneuropathy associated with IgM monoclonal gammopathy

Polyneuropathy associated with IgM monoclonal gammopathy (IgM-PNP) is a slowly progressive, sensorimotor neuropathy. It is assumed that complement activation contributes to IgM-PNP pathogenesis. We investigated whether innate differences in complement activity of the classical and mannose binding lectin (MBL) pathways are associated with IgM-PNP or its severity. We measured complement activity using ELISA and determined MBL serumc oncentrations and MBL gene polymorphisms in 83 patients and 83 healthy controls. We did not observe differences between IgM-PNP patients and healthy controls nor associations with different disease severities. Differences in innate complement activity are not likely to explain susceptibility to or severity of IgM-PNP.