Characterisation and carriage ratio of Clostridium difficile strains isolated from a community-dwelling elderly population in the United Kingdom

Background

Community-associated Clostridium difficile infection (CDI) appears to be an increasing problem. Reported carriage rates by C.difficile are debatable with suggestions that primary asymptomatic carriage is associated with decreased risk of subsequent diarrhoea. However, knowledge of potential reservoirs and intestinal carriage rates in the community, particularly in the elderly, the most susceptible group, is limited. We have determined the presence of C.difficile in the faeces of a healthy elderly cohort living outside of long-term care facilities (LCFs) in the United Kingdom.

Methods

Faecal samples from 149 community-based healthy elderly volunteers (median age 81 years) were screened for C.difficile using direct (Brazier''s CCEY) and enrichment (Cooked Meat broth) culture methods and a glutamate dehydrogenase (GDH) immunoassay. Isolates were PCR-ribotyped and analysed for toxin production and the presence of toxin genes.

Results

Of 149 faecal samples submitted, six (4%) were found to contain C.difficile. One particular sample was positive by both the GDH immunoassay and direct culture, and concurrently produced two distinct strain types: one toxigenic and the other non-toxigenic. The other five samples were only positive by enrichment culture method. Overall, four C.difficile isolates were non-toxigenic (PCR-ribotypes 009, 026 (n = 2) and 039), while three were toxigenic (PCR-ribotypes 003, 005 and 106). All individuals who had a positive culture were symptom-free and none of them had a history of CDI and/or antibiotics use in the 3 month period preceding recruitment.

Conclusions

To our knowledge, this is the first study of the presence of C.difficile in healthy elderly community-dwelling individuals residing outside of LCFs. The observed carriage rate is lower than that reported for individuals in LCFs and interestingly no individual carried the common epidemic strain PCR-ribotype 027 (NAP1/BI). Further follow-up of asymptomatic carriers in the community, is required to evaluate host susceptibility to CDI and identify dynamic changes in the host and microbial environment that are associated with pathogenicity.     

Lethal and pre-lethal effects of a fungal biopesticide contribute to substantial and rapid control of malaria vectors

Rapidly emerging insecticide resistance is creating an urgent need for new active ingredients to control the adult mosquitoes that vector malaria. Biopesticides based on the spores of entomopathogenic fungi have shown considerable promise by causing very substantial mortality within 7-14 days of exposure. This mortality will generate excellent malaria control if there is a high likelihood that mosquitoes contact fungi early in their adult lives. However, where contact rates are lower, as might result from poor pesticide coverage, some mosquitoes will contact fungi one or more feeding cycles after they acquire malaria, and so risk transmitting malaria before the fungus kills them. Critics have argued that 'slow acting' fungal biopesticides are, therefore, incapable of delivering malaria control in real-world contexts. Here, utilizing standard WHO laboratory protocols, we demonstrate effective action of a biopesticide much faster than previously reported. Specifically, we show that transient exposure to clay tiles sprayed with a candidate biopesticide comprising spores of a natural isolate of Beauveria bassiana, could reduce malaria transmission potential to zero within a feeding cycle. The effect resulted from a combination of high mortality and rapid fungal-induced reduction in feeding and flight capacity. Additionally, multiple insecticide-resistant lines from three key African malaria vector species were completely susceptible to fungus. Thus, fungal biopesticides can block transmission on a par with chemical insecticides, and can achieve this where chemical insecticides have little impact. These results support broadening the current vector control paradigm beyond fast-acting chemical toxins.     

Short-term learning and the searching accuracy of egg-laying butterflies

Searching constraints influence foraging patterns in three species of Colias butterflies. The activity of egg-laying females is partitioned into periods of searching for oviposition plants and periods of visiting flowers for nectar. Eggs are laid most frequently upon legume host-plants, although females frequently land upon non-legume species, particularly those bearing a superficial resemblance to suitable hosts. The average frequency of these landing ‘errors’ decreases over the course of an egglaying flight, implying thet females learn to identify host-plants more accurately on the basis of recent experience. Landing accuracy is low after periods of nectar-feeding, which suggests a trade-off between the two searching modalities. Within oviposition sequences, females that visit a narrow range of host specis make fewer landing errors than females visiting a broader host-plant set. Two interpretations of these data are presented: (1) that partitioning searching time into discrete modes may enhance overaccuracy in invertebrates, as has been demonstrated previously for vertebrates. Searching dynamics of this type may explain some discrepancies between the predictions made by simple optimal diet models and the occurrence of ‘switching’ behaviours in foragers.     

PSGL-1 derived from human neutrophils is a high-efficiency ligand for endothelium-expressed E-selectin under flow

P-selectin glycoprotein ligand-1 (PSGL-1) has been proposed as an important tethering ligand for E-selectin and is expressed at a modest level on human leukocytes. Sialyl Lewis x (sLe^x)-like glycans bind to E-selectin and are expressed at a relatively high level on circulating leukocytes. It is unclear whether PSGL-1 has unique biochemical attributes that contribute to its role as an E-selectin ligand. To probe this issue, we conjugated microspheres with either sLe^x or PSGL-1 purified from myeloid cells (neutrophils and HL-60) and compared their adhesion to endothelial expressed E-selectin under defined shear conditions. We found that both sLe^x and PSGL-1 microspheres adhere to 4 h of IL-1-activated human umbilical vein endothelial cells predominantly through E-selectin. Analysis of the adhesion revealed that the rate of initial tethering of the PSGL-1 microspheres to E-selectin was significantly greater than the rate of initial tethering of the sLe^x microspheres despite the fact that the sLe^x microspheres tested had higher ligand densities than the PSGL-1 microspheres. We also found that pretreatment of the PSGL-1 or sLe^x microspheres with HECA-452 had no significant effect on initial tethering to E-selectin. These results support the hypotheses that 1) PSGL-1 is a high-efficiency tethering ligand for E-selectin, 2) ligand biochemistry can significantly influence initial tethering to E-selectin, and 3) PSGL-1 tethering to E-selectin can occur via non-HECA-452 reactive epitopes. adhesion; leukocyte; inflammation     

Doubling the cloak of (in)competence in client/therapist interactions

Cultural competence is used (often implicitly) to make decisions in human service settings. When therapists make decisions about whether or not a particular service will be offered, they place themselves in a position where their own competence can be judged. Using narrative data on independence and the elderly, we apply Edgerton's idea of the cloak of competence to demonstrate this doubling effect.     

Declining fertility in the lethal yellow mouse is related to progressive hyperleptinemia and leptin resistance

Mice possessing the lethal yellow mutation (C57BL/6J A(y)/a) become obese and develop hyperleptinemia and leptin resistance as they age. To determine the relationship between altered leptin physiology and reproductive function in these mice, we compared body weight (BW), serum leptin concentration, ovulation rate, and in vitro blastocyst development among 120- and 180-d-old lethal yellow and black non-mutant (a/a) mice. Estrous female yellow and black mice were mated with fertile black males. Oviducts were flushed approximately 36 h after mating and the recovered embryos were cultured for 96 h. BW, serum leptin levels, and the leptin:BW ratio differed among groups as follows: 180-d yellow > 120-d yellow > 180-d black = 120-d black. Ovulation rate was similar among 120-d yellow and black, and 180-d black mice. Among 180-d yellow mice, five of twelve mice failed to ovulate, but the other seven mice ovulated a similar number of oocytes as their black counterparts (8.4 +/- 0.9 versus 8.0 +/- 1.3). Non-ovulators had higher (P < 0.05) leptin levels (56.6 +/- 1.8 ng x mL(-1)) than ovulators (46.2 +/- 3.5), but BW did not differ significantly. Fewer embryos from 180-d yellow mice reached the blastocyst stage in culture than did the embryos from black mice (55% versus 83%, P < 0.05). Moreover, blastocyst development in 180-d old yellow mice negatively correlated with leptin levels (r = -0.797, P = 0.032) and leptin:BW ratio (r = -0.847, P = 0.016), but not with BW. Declining reproductive function in lethal yellow mice appears to be related to increasing levels of leptin and progression of leptin resistance.     

An integrated genetic and physical map for the malaria vector Anopheles funestus

We have constructed a genetic map of the major African malaria vector, Anopheles funestus, using genetic markers segregating in F(2) progeny from crosses between two strains colonized from different field sites. Genotyping was performed on 174 progeny from three families using 33 microsatellite markers, a single RFLP, and 15 single nucleotide polymorphism (SNP) loci. Four linkage groups were resolved and these were anchored to chromosomes X and 2 and chromosomal arms 3R and 3L by comparison with a physical map of this species. Five markers were linked to the X chromosome, 16 markers to chromosome 2, and 10 and 11 markers to chromosomal arms 3R and 3L, respectively. This significantly increases the number of chromosomally defined genetic markers for this species and will facilitate the identification of genes controlling epidemiologically important traits such as resistance to insecticides or vector competence.     

Essential role for neutrophil recruitment to the liver in concanavalin A-induced hepatitis

Leukocyte infiltration into the liver is paramount to the development of liver injury in hepatitis. Hepatitis occurring after the administration of Con A in mice is felt to be a T lymphocyte-mediated disease. In this study, we report that neutrophils are the key initiators of lymphocyte recruitment and liver injury caused by Con A. The objectives of this study were to investigate the involvement of neutrophils in Con A-induced hepatitis in vivo via intravital microscopy. After Con A administration, we observed a significant increase in leukocyte rolling flux, a decrease in rolling velocity, and an increase in leukocyte adhesion to the hepatic microvasculature. Fluorescence microscopy identified that within 4 h of Con A administration only a minority of the recruited leukocytes were T lymphocytes. Furthermore, immunohistochemistry showed a significant increase in neutrophils recruited to the liver post-Con A treatment in association with liver cell damage, as reflected by elevated serum alanine aminotransferase levels. Using flow cytometry, we observed that Con A could bind directly to neutrophils, which resulted in a shedding of L-selectin, an increase in beta(2)-integrin expression, and the production of reactive oxidants. Following neutrophil depletion, a significant inhibition of Con A-induced CD4+ T lymphocyte recruitment to the liver resulted and complete reduction in hepatic injury, as assessed by serum alanine aminotransferase levels. In summary, the present data support the concept that neutrophils play an important and previously unrecognized role in governing Con A-induced CD4+ T cell recruitment to the liver and the subsequent development of hepatitis.