DNA methylation is associated with codon degeneracy in a species of bumblebee.

Social insects display extreme phenotypic differences between sexes and castes even though the underlying genome can be almost identical. Epigenetic processes have been proposed as a possible mechanism for mediating these phenotypic differences. Using whole genome bisulfite sequencing of queens, males, and reproductive female workers we have characterised the sex- and caste-specific methylome of the bumblebee Bombus terrestris. We have identified a potential role for DNA methylation in histone modification processes which may influence sex and caste phenotypic differences. We also find differentially methylated genes generally show low levels of DNA methylation which may suggest a separate function for lowly methylated genes in mediating transcriptional plasticity, unlike highly methylated genes which are usually involved in housekeeping functions. We also examined the relationship between the underlying genome and the methylome using whole genome re-sequencing of the same queens and males. We find DNA methylation is enriched at zero-fold degenerate sites. We suggest DNA methylation may be acting as a targeted mutagen at these sites, providing substrate for selection via non-synonymous changes in the underlying genome. However, we did not see any relationship between DNA methylation and rates of positive selection in our samples. In order to fully assess a possible role for DNA methylation in adaptive processes a specifically designed study using natural population data is needed.

Impact of hydrogen peroxide vapor room decontamination on Clostridium difficile environmental contamination and transmission in a healthcare setting.

OBJECTIVE: To determine whether hydrogen peroxide vapor (HPV) decontamination can reduce environmental contamination with and nosocomial transmission of Clostridium difficile. DESIGN: A prospective before-after intervention study. SETTING: A hospital affected by an epidemic strain of C. difficile. INTERVENTION: Intensive HPV decontamination of 5 high-incidence wards followed by hospital-wide decontamination of rooms vacated by patients with C. difficile-associated disease (CDAD). The preintervention period was June 2004 through March 2005, and the intervention period was June 2005 through March 2006. RESULTS: Eleven (25.6%) of 43 cultures of samples collected by sponge from surfaces before HPV decontamination yielded C. difficile, compared with 0 of 37 cultures of samples obtained after HPV decontamination (P < .001). On 5 high-incidence wards, the incidence of nosocomial CDAD was significantly lower during the intervention period than during the preintervention period (1.28 vs 2.28 cases per 1,000 patient-days; P = .047). The hospital-wide CDAD incidence was lower during the intervention period than during the preintervention period (0.84 vs 1.36 cases per 1,000 patient-days; P = .26). In an analysis limited to months in which the epidemic strain was present during both the preintervention and the intervention periods, CDAD incidence was significantly lower during the intervention period than during the preintervention period (0.88 vs 1.89 cases per 1,000 patient-days; P = .047). CONCLUSIONS: HPV decontamination was efficacious in eradicating C. difficile from contaminated surfaces. Further studies of the impact of HPV decontamination on nosocomial transmission of C. difficile are warranted.

Widespread environmental contamination associated with patients with diarrhea and methicillin-resistant Staphylococcus aureus colonization of the gastrointestinal tract.

OBJECTIVE: Patients colonized with methicillin-resistant Staphylococcus aureus (MRSA) may contaminate their immediate environment with this organism. However, the extent to which gastrointestinal colonization with MRSA affects environmental contamination is not known. We investigated the frequency of environmental contamination in the rooms of patients with diarrheal stools and heavy gastrointestinal colonization with MRSA. DESIGN: Prospective observational study. SETTING: A 500-bed teaching hospital. METHODS: Stool specimens submitted for Clostridium difficile toxin assays were inoculated onto colistin-naladixic acid agar. MRSA was identified with standard methods. Samples from a standardized list of 10 environmental surfaces were cultured, from the rooms of 8 patients who had diarrhea that yielded heavy growth of MRSA (case patients) and from the rooms of 6 MRSA-positive patients with stool cultures negative for MRSA (control patients). MRSA isolates from 13 patients (8 case patients and 5 control patients) and 64 of the environmental isolates recovered from their rooms were compared by pulsed-field gel electrophoresis (PFGE). One clinical isolate from a control patient was excluded because there was no corresponding environmental MRSA isolate with which to compare it. RESULTS: Overall, MRSA were recovered from 47 (58.8%) of 80 surfaces in the rooms of case patients, compared with 14 (23.3%) of 60 surfaces in the rooms of control patients (58.8% [95% CI, 47.8-68.9] vs 23.3% [95% CI, 14.3-35.5]; P<.0001). The items most commonly contaminated were bedside rails, blood pressure cuffs, television remote controls, and toilet seats. Seventy-eight percent of the environmental isolates in patients' rooms had PFGE types that were indistinguishable or closely related to those recovered from the patients' clinical specimens. CONCLUSIONS: Patients who have diarrheal stools and heavy gastrointestinal colonization with MRSA are associated with significantly greater environmental MRSA contamination than patients without MRSA in their stool, and they are likely to be the source of that contamination.