Avidity measurements and anti-LPS antibodies induced during salmonella infections in pigs

Traditional serological tests provide only a semiquantitative measure of antibodies present but not their binding strength to the test antigen. We have established an enzyme immunoassay (ELISA) for avidity (functional affinity) measurements, based on the ability of urea to dissociate low avidity antibody-antigen complexes. In the avidity ELISA LPS-coated microliter plates are incubated with pig sera and afterwards treated with urea. In parallel the same sera are incubated without subsequent urea treatment. The ratio between the OD-values from incubations with and without urea treatment gives the avidity index (Hedman et al. 1989, Kallio-Kokko et al. 1992, Lappalainen et al. 1992). Antibodies of low avidity are dissociated easily and give an low index, whereas antibodies of high avidity are unaffected by the treatment resulting in high indices (Hedman et al. 1989). We have applied this method to investigate the development of avidity for IgG and IgM antibodies during experimental Salmonella Typhimurium infection in pigs. Avidity assays are of special interest in follow-up studies on herd level, where information is needed regarding the onset of infection or regarding the presence of chronically infected animals

Reactivities towards enterobacterial LPS in pig sera from herds in a Salmonella non-endemic region

In Sweden legislation concerning extensive restrictions in herds found Salmonella positive has been in operation for four decades. All findings of Salmonella isolates among animals are compulsory notifiable and reports of Salmonella findings have been published continuously, first time 1957 (I) and last time 1998 (2). Bacteriological prevalence in herds, slaughter-houses and cutting plants has been documented during the last four years and the overall prevalence has been proven to be less than 0.1 %, 95% confidence interval, (2-5). In addition to the national programme Sweden has as well participated in the European project SALINPORK investigating the prevalence and developing strategies to control and reduce Salmonella (6). In this connection sera (3050 in total) from 61 Swedish pig herds were tested in the Dartish surveillance system which is based on serological testing rather than bacteriology as in Sweden. A significant part of these sera had moderate responses (20-70 OD% ). When applying I 0 OD% as cut-off value, 59% of the herds had more than one sera-reactor, and at 40 OD% as cut-off value 7% of the herds had more than one sera-reactor. The mean OD% for all individual pigs in the 61 herds was 4.4, with the standard deviation of 6.7

a pilot study, 2013

Introduction After recognition of European outbreaks of Clostridium difficile infections (CDIs) associated with the emergence of PCR ribotype 027/NAP1 in 2005, CDI surveillance at country level was encouraged by the European Centre for Disease Prevention and Control (ECDC) [1]. In 2008, an ECDC-supported European CDI survey (ECDIS) identified large intercountry variations in incidence rates and distribution of prevalent PCR ribotypes, with the outbreak-related PCR ribotype 027 being detected in 5% (range: 0–26) of the characterised isolates [2]. The surveillance period was limited to one month and the representation of European hospitals was incomplete; however, this has been the only European (comprising European Union (EU)/European Economic Area (EEA) and EU candidate countries) CDI surveillance study. The authors highlighted the need for national and European surveillance to control CDI. Yet, European countries were found to have limited capacity for diagnostic testing, particularly in terms of standard use of optimal methods and absence of surveillance protocols and a fully validated, standardised and exchangeable typing system for surveillance and/or outbreak investigation. As of 2011, 14 European countries had implemented national CDI surveillance, with various methodologies [3]. National surveillance systems have since reported a decrease in CDI incidence rate and/or prevalence of PCR ribotype 027 in some European countries [4-8]. However, CDI generally remains poorly controlled in Europe [9], and PCR ribotype 027 continues to spread in eastern Europe [10-12] and globally [13]. In 2010, ECDC launched a new project, the European C. difficile Infection Surveillance Network (ECDIS-Net), to enhance surveillance of CDI and laboratory capacity to test for CDI in Europe. The goal of ECDIS- Net was to establish a standardised CDI surveillance protocol suitable for application all over Europe in order to: (i) estimate the incidence rate and total infection rate of CDI (including recurrent CDI cases) in European acute care hospitals; (ii) provide participating hospitals with a standardised tool to measure and compare their own incidence rates with those observed in other participating hospitals; (iii) assess adverse outcomes of CDI such as complications and death; and (iv) describe the epidemiology of CDI concerning antibiotic susceptibility, PCR ribotypes, presence of tcdA, tcdB and binary toxins and detect new emerging types at local, national and European level. The primary objectives of the present study were to: (i) test the pilot protocol for the surveillance of CDI in European acute care hospitals developed by ECDIS-Net (methodology, variables and indicators); (ii) assess the feasibility and workload of collecting the required hospital data, case- based epidemiological and microbiological data; and (iii) evaluate the quality of data collected, whether in the presence or absence of existing national CDI surveillance activities. A secondary aim was to assess the relationship between patient and microbiological characteristics and in-hospital outcome of CDI to confirm the added value of collecting detailed epidemiological and microbiological data on CDI at European level

Standardised surveillance of Clostridium Difficile Infection in European acute care hospitals: A pilot study, 2013

Clostridium difficile infection (CDI) remains poorly controlled in many European countries, of which several have not yet implemented national CDI surveillance. In 2013, experts from the European CDI Surveillance Network project and from the European Centre for Disease Prevention and Control developed a protocol with three options of CDI surveillance for acute care hospitals: a ‘minimal’ option (aggregated hospital data), a ‘light’ option (including patient data for CDI cases) and an ‘enhanced’ option (including microbiological data on the first 10 CDI episodes per hospital). A total of 37 hospitals in 14 European countries tested these options for a three-month period (between 13 May and 1 November 2013). All 37 hospitals successfully completed the minimal surveillance option (for 1,152 patients). Clinical data were submitted for 94% (1,078/1,152) of the patients in the light option; information on CDI origin and outcome was complete for 94% (1,016/1,078) and 98% (294/300) of the patients in the light and enhanced options, respectively. The workload of the options was 1.1, 2.0 and 3.0 person-days per 10,000 hospital discharges, respectively. Enhanced surveillance was tested and was successful in 32 of the hospitals, showing that C. difficile PCR ribotype 027 was predominant (30% (79/267)). This study showed that standardised multicountry surveillance, with the option of integrating clinical and molecular data, is a feasible strategy for monitoring CDI in Europe

Phenotypic Variation and Bistable Switching in Bacteria

Microbial research generally focuses on clonal populations. However, bacterial cells with identical genotypes frequently display different phenotypes under identical conditions. This microbial cell individuality is receiving increasing attention in the literature because of its impact on cellular differentiation, survival under selective conditions, and the interaction of pathogens with their hosts. It is becoming clear that stochasticity in gene expression in conjunction with the architecture of the gene network that underlies the cellular processes can generate phenotypic variation. An important regulatory mechanism is the so-called positive feedback, in which a system reinforces its own response, for instance by stimulating the production of an activator. Bistability is an interesting and relevant phenomenon, in which two distinct subpopulations of cells showing discrete levels of gene expression coexist in a single culture. In this chapter, we address techniques and approaches used to establish phenotypic variation, and relate three well-characterized examples of bistability to the molecular mechanisms that govern these processes, with a focus on positive feedback.

Nonheritable Cellular Variability Accelerates the Evolutionary Processes of Cancer

Heritable genetic or epigenetic changes in cells are thought to drive tumor development, metastasis, and drug resistance. This essay discusses the possibility that nonheritable phenotypic variability contributes to the evolution of cancer, suggesting new approaches to treatment

Is Bacterial Persistence a Social Trait?

The ability of bacteria to evolve resistance to antibiotics has been much reported in recent years. It is less well-known that within populations of bacteria there are cells which are resistant due to a non-inherited phenotypic switch to a slow-growing state. Although such ‘persister’ cells are receiving increasing attention, the evolutionary forces involved have been relatively ignored. Persistence has a direct benefit to cells because it allows survival during catastrophes–a form of bet-hedging. However, persistence can also provide an indirect benefit to other individuals, because the reduced growth rate can reduce competition for limiting resources. This raises the possibility that persistence is a social trait, which can be influenced by kin selection. We develop a theoretical model to investigate the social consequences of persistence. We predict that selection for persistence is increased when: (a) cells are related (e.g. a single, clonal lineage); and (b) resources are scarce. Our model allows us to predict how the level of persistence should vary with time, across populations, in response to intervention strategies and the level of competition. More generally, our results clarify the links between persistence and other bet-hedging or social behaviours

The Neglected Intrinsic Resistome of Bacterial Pathogens

Bacteria with intrinsic resistance to antibiotics are a worrisome health problem. It is widely believed that intrinsic antibiotic resistance of bacterial pathogens is mainly the consequence of cellular impermeability and activity of efflux pumps. However, the analysis of transposon-tagged Pseudomonas aeruginosa mutants presented in this article shows that this phenotype emerges from the action of numerous proteins from all functional categories. Mutations in some genes make P. aeruginosa more susceptible to antibiotics and thereby represent new targets. Mutations in other genes make P. aeruginosa more resistant and therefore define novel mechanisms for mutation-driven acquisition of antibiotic resistance, opening a new research field based in the prediction of resistance before it emerges in clinical environments. Antibiotics are not just weapons against bacterial competitors, but also natural signalling molecules. Our results demonstrate that antibiotic resistance genes are not merely protective shields and offer a more comprehensive view of the role of antibiotic resistance genes in the clinic and in nature

Ciprofloxacin Causes Persister Formation by Inducing the TisB toxin in Escherichia coli

Persisters are specialized survivor cells that arise in populations of E. coli after antibiotic-mediated DNA damage induces the production of a small membrane-acting peptide TisB, which causes reversible dormancy. The TisB-dependent persisters are tolerant to multiple antibiotics