Cornelis Vink

Anti-Staphylococcal Humoral Immune Response in Persistent Nasal Carriers and Noncarriers of Staphylococcus aureus

BACKGROUNDnPersistent carriers have a higher risk of Staphylococcus aureus infections than noncarriers but a lower risk of bacteremia-related death. Here, the role played by anti-staphylococcal antibodies was studied.nnnMETHODSnSerum samples from 15 persistent carriers and 19 noncarriers were analyzed for immunoglobulin (Ig) G, IgA, and IgM binding to 19 S. aureus antigens, by means of Luminex technology. Nasal secretions and serum samples obtained after 6 months were also analyzed.nnnRESULTSnMedian serum IgG levels were significantly higher in persistent carriers than in noncarriers for toxic shock syndrome toxin (TSST)-1 (median fluorescence intensity [MFI] value, 11,554 vs. 4291; P < .001) and staphylococcal enterotoxin (SE) A (742 vs. 218; P < .05); median IgA levels were higher for TSST-1 (P < .01), SEA, and clumping factor (Clf) A and B (P < .05). The in vitro neutralizing capacity of anti-TSST-1 antibodies was correlated with the MFI value (R(2) = 0.93) and was higher in persistent carriers (90.6% vs. 70.6%; P < .05). Antibody levels were stable over time and correlated with levels in nasal secretions (for IgG, R(2) = 0.87; for IgA, R(2) = 0.77).nnnCONCLUSIONSnAntibodies to TSST-1 have a neutralizing capacity, and median levels of antibodies to TSST-1, SEA, ClfA, and ClfB are higher in persistent carriers than in noncarriers. These antibodies might be associated with the differences in the risk and outcome of S. aureus infections between nasal carriers and noncarriers.

Carriage of Mycoplasma pneumoniae in the Upper Respiratory Tract of Symptomatic and Asymptomatic Children: An Observational Study

In order to determine the possible asymptomatic carriage of Mycoplasma pneumoniae in the upper respiratory tracts of children, Emiel Spuesens and colleagues investigate the prevalence of M. pneumoniae in symptomatic and asymptomatic children at a hospital in The Netherlands. Please see later in the article for the Editors Summary

Microbial antigenic variation mediated by homologous DNA recombination.

Pathogenic microorganisms employ numerous molecular strategies in order to delay or circumvent recognition by the immune system of their host. One of the most widely used strategies of immune evasion is antigenic variation, in which immunogenic molecules expressed on the surface of a microorganism are continuously modified. As a consequence, the host is forced to constantly adapt its humoral immune response against this pathogen. An antigenic change thus provides the microorganism with an opportunity to persist and/or replicate within the host (population) for an extended period of time or to effectively infect a previously infected host. In most cases, antigenic variation is caused by genetic processes that lead to the modification of the amino acid sequence of a particular antigen or to alterations in the expression of biosynthesis genes that induce changes in the expression of a variant antigen. Here, we will review antigenic variation systems that rely on homologous DNA recombination and that are found in a wide range of cellular, human pathogens, including bacteria (such as Neisseria spp., Borrelia spp., Treponema pallidum, and Mycoplasma spp.), fungi (such as Pneumocystis carinii) and parasites (such as the African trypanosome Trypanosoma brucei). Specifically, the various DNA recombination-based antigenic variation systems will be discussed with a focus on the employed mechanisms of recombination, the DNA substrates, and the enzymatic machinery involved.

Chemokines and Chemokine Receptors Encoded by Cytomegaloviruses

CMVs carry several genes that are homologous to genes of the host organism. These include genes homologous to those encoding chemokines (CKs) and G protein-coupled receptors (GPCRs). It is generally assumed that these CMV genes were hijacked from the host genome during the long co-evolution of virus and host. In light of the important function of the CK and GPCR families in the normal physiology of the host, it has previously been hypothesized that the CMV homologs of these proteins, CMV vCKs and vGPCRs, may also have a significant impact on this physiology, such that lifelong maintenance and/or replication of the virus within the infected host is guaranteed. In addition, several of these homologs were reported to have a major impact in the pathogenesis of infection. In this review, the current state of knowledge on the CMV vCKs and vGPCRs will be discussed.

Raman spectroscopic typing reveals the presence of carotenoids in Mycoplasma pneumoniae.

Raman spectroscopy has previously been demonstrated to be a highly useful methodology for the identification and/or typing of micro-organisms. In this study, we set out to evaluate whether this technology could also be applied as a tool to discriminate between isolates of Mycoplasma pneumoniae, which is generally considered to be a genetically highly uniform species. In this evaluation, a total of 104 strains of M. pneumoniae were analysed, including two reference strains (strains M129 and FH), and 102 clinical isolates, which were isolated between 1973 and 2005 and originated from various countries. By Raman spectral analysis (Raman typing) of this strain collection, we were able to reproducibly distinguish six different clusters of strains. An unequivocal correlation between Raman typing and P1 genotyping, which is based on sequence differences in the P1 (or MPN141) gene of M. pneumoniae, was not observed. In the two major Raman clusters that we identified (clusters 3 and 6, which together harboured 81 % of the strains), the different P1 subtypes were similarly distributed, and approximately 76 % isolates were of subtype 1, approximately 20 % of subtype 2 and approximately 5 % of variant 2a. Nevertheless, a relatively high prevalence of P1 subtype 2 strains was found in clusters 2 and 5 (100 %), as well as in cluster 1 (75 %) and cluster 4 (71 %); these clusters, however, harboured a small number of strains. Only two of the strains (2 %) could not be typed correctly. Interestingly, analysis of the Raman spectra revealed the presence of carotenoids in M. pneumoniae. This finding is in line with the identification of M. pneumoniae genes that have similarity with genes involved in a biochemical pathway leading to carotenoid synthesis, i.e. the 2-C-methyl-d-erythritol 4-phosphate (MEP) pathway. Therefore, we hypothesize that M. pneumoniae hosts an MEP-like pathway for carotenoid synthesis. We conclude that Raman spectroscopy is a convenient tool for discriminating between M. pneumoniae strains, and that it presents a promising supplement to the current methods for typing of this bacterium.

Mycoplasma pneumoniae in children: Carriage, pathogenesis, and antibiotic resistance

Purpose of review Both the diagnosis and treatment of Mycoplasma pneumoniae infections in children are currently facing two main challenges: a relatively high carriage in asymptomatic children, and a worldwide increase in macrolide-resistant M. pneumoniae (MRMP). This review focuses on the scientific and clinical implications of these crucial issues. Recent findings Recent studies have indicated that the prevalence of M. pneumoniae in the upper respiratory tract is similar among asymptomatic, healthy children and children with a symptomatic respiratory tract infection, and that current diagnostic procedures for M. pneumoniae are unable to differentiate between bacterial carriage and infection. It is therefore possible that the burden of M. pneumoniae-associated disease is overestimated. Another phenomenon that has an important impact on the treatment of M. pneumoniae infections is the rapid worldwide emergence of MRMP isolates. Summary The current diagnostic procedures for M. pneumoniae cannot discern between bacterial carriage and infection in a clinically relevant time frame. It is therefore imperative that these procedures be modified such as to unambiguously detect symptomatic M. pneumoniae infections. Moreover, the emergence of MRMP necessitates the application of methods to detect macrolide resistance as well as the implementation of restrictive policies regarding the use of macrolides.

Mycoplasma pneumoniae infections – Does treatment help?

Mycoplasma pneumoniae is a common cause of respiratory tract infections (RTIs), especially in children. While severe M. pneumoniae infections are generally treated with antibiotics, the diagnosis as well as treatment of these infections should be reconsidered in the light of recent clinical findings. First, M. pneumoniae was found to be carried in the upper respiratory tract of a relatively high percentage of healthy, asymptomatic children. Clearly, this complicates the diagnosis of a suspected M. pneumoniae RTI and, thus, the decision when to initiate treatment. A complication in the treatment of these infections is that data on the efficacy of antibiotic treatment of M. pneumoniae RTIs are sparse and derived exclusively from comparative studies. A recent Cochrane review concluded that there is insufficient evidence about the efficacy of antibiotics for M. pneumoniae lower respiratory tract infections (LRTI) in children. Due to side effects associated with the use of tetracyclines and quinolones in children, only macrolides can be used to treat M. pneumoniae infections in young patients. The general applicability of macrolides, however, is currently threatened by the worldwide increase in macrolide-resistant M. pneumoniae strains. Finally, limited evidence is available that corticosteroids might have an additional benefit in the treatment of M. pneumoniae infections. In this review, the current issues related to the diagnosis and treatment of M. pneumoniae infections will be discussed.

The Mycoplasma pneumoniae MPN229 gene encodes a protein that selectively binds single-stranded DNA and stimulates Recombinase A-mediated DNA strand exchange

BackgroundMycoplasma pneumoniae has previously been characterized as a micro-organism that is genetically highly stable. In spite of this genetic stability, homologous DNA recombination has been hypothesized to lie at the basis of antigenic variation of the major surface protein, P1, of M. pneumoniae. In order to identify the proteins that may be involved in homologous DNA recombination in M. pneumoniae, we set out to characterize the MPN229 open reading frame (ORF), which bears sequence similarity to the gene encoding the single-stranded DNA-binding (SSB) protein of other micro-organisms.ResultsThe MPN229 ORF has the capacity to encode a 166-amino acid protein with a calculated molecular mass of 18.4 kDa. The amino acid sequence of this protein (Mpn SSB) is most closely related to that of the protein predicted to be encoded by the MG091 gene from Mycoplasma genitalium (61% identity). The MPN229 ORF was cloned, and different versions of Mpn SSB were expressed in E. coli and purified to > 95% homogeneity. The purified protein was found to exist primarily as a homo-tetramer in solution, and to strongly and selectively bind single-stranded DNA (ssDNA) in a divalent cation- and DNA substrate sequence-independent manner. Mpn SSB was found to bind with a higher affinity to ssDNA substrates larger than 20 nucleotides than to smaller substrates. In addition, the protein strongly stimulated E. coli Recombinase A (RecA)-promoted DNA strand exchange, which indicated that Mpn SSB may play an important role in DNA recombination processes in M. pneumoniae.ConclusionThe M. pneumoniae MPN229 gene encodes a protein, Mpn SSB, which selectively and efficiently binds ssDNA, and stimulates E. coli RecA-promoted homologous DNA recombination. Consequently, the Mpn SSB protein may play a crucial role in DNA recombinatorial pathways in M. pneumoniae. The results from this study will pave the way for unraveling these pathways and assess their role in antigenic variation of M. pneumoniae.

Infection with and Carriage of Mycoplasma pneumoniae in Children.

“Atypical” pneumonia was described as a distinct and mild form of community-acquired pneumonia (CAP) already before Mycoplasma pneumoniae had been discovered and recognized as its cause. M. pneumoniae is detected in CAP patients most frequently among school-aged children from 5 to 15 years of age, with a decline after adolescence and tapering off in adulthood. Detection rates by polymerase chain reaction (PCR) or serology in children with CAP admitted to the hospital amount 4–39%. Although the infection is generally mild and self-limiting, patients of every age can develop severe or extrapulmonary disease. Recent studies indicate that high rates of healthy children carry M. pneumoniae in the upper respiratory tract and that current diagnostic PCR or serology cannot discriminate between M. pneumoniae infection and carriage. Further, symptoms and radiologic features are not specific for M. pneumoniae infection. Thus, patients may be unnecessarily treated with antimicrobials against M. pneumoniae. Macrolides are the first-line antibiotics for this entity in children younger than 8 years of age. Overall macrolides are extensively used worldwide, and this has led to the emergence of macrolide-resistant M. pneumoniae, which may be associated with severe clinical features and more extrapulmonary complications. This review focuses on the characteristics of M. pneumoniae infections in children, and exemplifies that simple clinical decision rules may help identifying children at high risk for CAP due to M. pneumoniae. This may aid physicians in prescribing appropriate first-line antibiotics, since current diagnostic tests for M. pneumoniae infection are not reliably predictive.

The Mycoplasma pneumoniae MPN490 and Mycoplasma genitalium MG339 Genes Encode RecA Homologs That Promote Homologous DNA Strand Exchange

ABSTRACT The P1, P40, and P90 proteins of Mycoplasma pneumoniae and the MgPa and P110 proteins of Mycoplasma genitalium are immunogenic adhesion proteins that display sequence variation. Consequently, these proteins are thought to play eminent roles in immune evasive strategies. For each of the five proteins, a similar underlying molecular mechanism for sequence variation was hypothesized, i.e., modification of the DNA sequences of their respective genes. This modification is thought to result from homologous recombination of parts of these genes with repeat elements (RepMp and MgPar elements in M. pneumoniae and M. genitalium, respectively) that are dispersed throughout the bacterial genome. Proteins that are potentially involved in homologous DNA recombination have been suggested to be implicated in recombination between these repeat elements and thereby in antigenic variation. To investigate this notion, we set out to study the function of the RecA homologs that are encoded by the M. pneumoniae MPN490 and M. genitalium MG339 genes. Both proteins, which are 79% identical on the amino acid level, were found to promote recombination between homologous DNA substrates in an ATP-dependent fashion. The recombinational activities of both proteins were Mg2+ and pH dependent and were strongly supported by the presence of single-stranded DNA binding protein, either from M. pneumoniae or from Escherichia coli. We conclude that the MPN490- and MG339-encoded proteins are RecA homologs that have the capacity to recombine homologous DNA substrates. Thus, they may play a central role in recombination between repetitive elements in both M. pneumoniae and M. genitalium.