The potential of alcohol release doorplates to reduce surface contamination during hand contact.

BACKGROUND: Optimal hand hygiene may be compromised by contact with contaminated environmental surfaces. AIM: To investigate the in-vitro efficacy of a novel alcohol-release doorplate to reduce surface contamination during hand contact. METHODS: Prototype, horizontally held, Surfaceskins, alcohol gel-impregnated and control (aluminium) doorplates were challenged (N = 72 per micro-organism) with Staphylococcus aureus-, Eschericia coli-, Enterococcus faecalis-, or Clostridium difficile-contaminated fingers. S. aureus and E. faecalis were used for challenges (90 per micro-organism) of vertical (modified design) doorplates, on days 0, 3, 4, 6, and 7. Surface contamination was measured pre and immediately post challenges using agar contact plates. FINDINGS: Horizontal test, but not control, doorplates demonstrated bacterial killing of S. aureus, E. faecalis and E. coli, but not of C. difficile; hence, only testing of S. aureus and E. faecalis was continued. Vertical Surfaceskins, but not control, doorplates demonstrated rapid killing of S. aureus over seven days. There were significant reductions (>90% up to day 6; P ≤ 0.01) of surface bacterial colony counts compared with controls immediately post challenge. There were also significant reductions in Surfaceskins doorplate enterococcal colony counts compared with controls on every day of testing (P ≤ 0.004). There was no evidence that bacterial recovery was greater from the tops of Surfaceskins doorplates (i.e. due to pooling of contents). CONCLUSION: Surfaceskins doorplates were efficient at reducing surface contamination by S. aureus, E. faecalis, and E. coli. Reducing microbial contamination of frequently touched door surfaces, and so bacterial transfer via hands, could feasibly reduce the risk of healthcare-associated and other infections.

Comparison of different hand-drying methods: the potential for airborne microbe dispersal and contamination.

Efficient washing and drying of hands is important in prevention of the transfer of micro-organisms. However, knowledge surrounding the potential for microbial contamination according to hand-drying methods is limited. This study assessed the potential for airborne microbe dispersal during hand drying by four methods (paper towels, roller towel, warm air and jet air dryer) using three different models. The jet air dryer dispersed liquid from users' hands further and over a greater range (up to 1.5m) than the other drying methods (up to 0.75 m), demonstrating the differing potential risks for airborne microbe dissemination, particularly if handwashing is suboptimal.

Microbiological comparison of hand-drying methods: the potential for contamination of the environment, user, and bystander.

BACKGROUND: The efficiency of hand drying is important in preventing pathogen spread, but knowledge surrounding which drying methods contribute least towards contamination of the environment and users is limited. AIM: To compare the propensity of three common hand-drying methods (jet air, warm air dryers, and paper towels) to contaminate the environment, users, and bystanders. METHODS: Hands were coated in lactobacilli to simulate poorly washed, contaminated hands, and dried. The investigation comprised 120 air-sampling tests (60 tests and 60 controls), divided into close and 1m proximity from the drying process. Separate tests used hands coated in paint to visualize droplet dispersal. FINDINGS: Air bacterial counts in close proximity to hand drying were 4.5-fold higher for the jet air dryer (70.7 cfu) compared with the warm air dryer (15.7 cfu) (P=0.001), and 27-fold higher compared with use of paper towels (2.6 cfu) (P<0.001). Airborne counts were also significantly different during use of towel drying versus warm air dryer (P=0.001). A similar pattern was seen for bacterial counts at 1m away. Visualization experiments demonstrated that the jet air dryer caused the most droplet dispersal. CONCLUSION: Jet air and warm air dryers result in increased bacterial aerosolization when drying hands. These results suggest that air dryers may be unsuitable for use in healthcare settings, as they may facilitate microbial cross-contamination via airborne dissemination to the environment or bathroom visitors.

Effectiveness of deep cleaning followed by hydrogen peroxide decontamination during high Clostridium difficile infection incidence.

BACKGROUND: Clostridium difficile infection (CDI) remains an infection control challenge, especially when environmental spore contamination and suboptimal cleaning may increase transmission risk. AIM: To substantiate the long-term effectiveness throughout a stroke rehabilitation unit (SRU) of deep cleaning and hydrogen peroxide decontamination (HPD), following a high incidence of CDI. METHODS: Extensive environmental sampling (342 sites on each occasion) for C. difficile using sponge wipes was performed: before and after deep cleaning with detergent/chlorine agent; immediately following HPD; and on two further occasions, 19 days and 20 weeks following HPD. C. difficile isolates underwent polymerase chain reaction ribotyping and multi-locus variable repeat analysis (MLVA). FINDINGS: C. difficile was recovered from 10.8%, 6.1%, 0.9%, 0% and 3.5% of sites at baseline, following deep cleaning, immediately after HPD, and 19 days and 20 weeks after HPD, respectively. C. difficile ribotypes recovered after deep cleaning matched those from CDI cases in the SRU during the previous 10 months. Similarly, 10/12 of the positive sites identified at 20 weeks post-HPD harboured the same C. difficile ribotype (002) and MLVA pattern as the isolate from the first post-HPD CDI case. CDI incidence [number of cases on SRU per 10 months (January-October 2011)] declined from 20 before to seven after the intervention. CONCLUSION: HPD, after deep cleaning with a detergent/chlorine agent, was highly effective for removing environmental C. difficile contamination. Long-term follow-up demonstrated that a CDI symptomatic patient can rapidly recontaminate the immediate environment. Determining a role for HPD should include long-term cost-effectiveness evaluations.

Comparison of multilocus variable-number tandem-repeat analysis and whole-genome sequencing for investigation of Clostridium difficile transmission.

No study to date has compared multilocus variable-number tandem-repeat analysis (MLVA) and whole-genome sequencing (WGS) in an investigation of the transmission of Clostridium difficile infection. Isolates from 61 adults with ongoing and/or recurrent C. difficile infections and 17 asymptomatic carriage episodes in children (201 samples), as well as from 61 suspected outbreaks affecting 2 to 41 patients in 31 hospitals in the United Kingdom (300 samples), underwent 7-locus MLVA and WGS in parallel. When the first and last samples from the same individual taken for a median (interquartile range [IQR]) of 63 days (43 to 105 days) apart were compared, the estimated rates of the evolution of single nucleotide variants (SNVs), summed tandem-repeat differences (STRDs), and locus variants (LVs) were 0.79 (95% confidence interval [CI], 0.00 to 1.75), 1.63 (95% CI, 0.00 to 3.59), and 1.21 (95% CI, 0.00 to 2.67)/called genome/year, respectively. Differences of >2 SNVs and >10 STRDs have been used to exclude direct case-to-case transmission. With the first serial sample per individual being used to assess discriminatory power, across all pairs of samples sharing a PCR ribotype, 192/283 (68%) differed by >10 STRDs and 217/283 (77%) by >2 SNVs. Among all pairs of cases from the same suspected outbreak, 1,190/1,488 (80%) pairs had concordant results using >2 SNVs and >10 STRDs to exclude transmission. For the discordant pairs, 229 (15%) had ≥2 SNVs but ≤10 STRDs, and 69 (5%) had ≤2 SNVs but ≥10 STRDs. Discordant pairs had higher numbers of LVs than concordant pairs, supporting the more diverse measure in each type of discordant pair. Conclusions on whether the potential outbreaks were confirmed were concordant in 58/61 (95%) investigations. Overall findings using MLVA and WGS were very similar despite the fact that they analyzed different parts of the bacterial genome. With improvements in WGS technology, it is likely that MLVA locus data will be available from WGS in the near future.

Potential for aerosolization of Clostridium difficile after flushing toilets: the role of toilet lids in reducing environmental contamination risk.

BACKGROUND: Toilet facilities in healthcare settings vary widely, but patient toilets are commonly shared and do not have lids. When a toilet is flushed without the lid closed, aerosol production may lead to surface contamination within the toilet environment. AIM: To substantiate the risks of airborne dissemination of C. difficile following flushing a toilet, in particular when lids are not fitted. METHODS: We performed in-situ testing, using faecal suspensions of C. difficile to simulate the bacterial burden found during disease, to measure C. difficile aerosolization. We also measured the extent of splashing occurring during flushing of two different toilet types commonly used in hospitals. FINDINGS: C. difficile was recoverable from air sampled at heights up to 25 cm above the toilet seat. The highest numbers of C. difficile were recovered from air sampled immediately following flushing, and then declined 8-fold after 60 min and a further 3-fold after 90 min. Surface contamination with C. difficile occurred within 90 min after flushing, demonstrating that relatively large droplets are released which then contaminate the immediate environment. The mean numbers of droplets emitted upon flushing by the lidless toilets in clinical areas were 15-47, depending on design. C. difficile aerosolization and surrounding environmental contamination occur when a lidless toilet is flushed. CONCLUSION: Lidless conventional toilets increase the risk of C. difficile environmental contamination, and we suggest that their use is discouraged, particularly in settings where CDI is common.

Multiple-locus variable-number tandem repeat analysis of Salmonella enterica subsp. enterica serovar Typhimurium: comparison of isolates from pigs, poultry and cases of human gastroenteritis.

AIMS: Pulsed-field gel electrophoresis (PFGE) and variable number tandem repeat (VNTR) profiles of 195 epidemiologically unrelated Salmonella Typhimurium strains isolated in 1997-2004 from pigs were analysed and the results compared to establish the discriminatory ability of each method. In order to investigate the epidemiology of S. Typhimurium from different populations, the VNTR profiles from pigs were compared with those obtained from 190 S. Typhimurium strains isolated from poultry and 186 strains isolated from human cases of gastroenteritis. METHODS AND RESULTS: A total of 195 strains of S. Typhimurium were tested by PFGE and VNTR. For PFGE, the restriction enzyme XbaI was used, and for VNTR, the number of repeats at five loci (STTR 9, 5, 6, 10pl and 3) were counted and assigned an allele number based on an established VNTR scheme. The results obtained showed improved discrimination of VNTR when compared with PFGE with 34 PFGE profiles identified compared with 96 different VNTR profiles for the pig isolates and 56 different VNTR types within the most common PFGE type. Within the three different populations, VNTR showed distinct subpopulations of VNTR type related not only to source, but also demonstrated common VNTR types within samples obtained from humans, poultry and pigs, especially in strains of phage type DT104. CONCLUSIONS: VNTR has taken the discrimination to a further level than that obtained through PFGE, and demonstrated an overlap in the genetic diversity of isolates tested across the three different populations, confirming previous suggestions that animals have an involvement in the dissemination of S. Typhimurium through the food chain. SIGNIFICANCE AND IMPACT OF THE STUDY: Salmonella Typhimurium remains an important concern as a food-borne zoonotic agent. The VNTR strategy described provides an accurate method of tracing strain dissemination, and adds a further level of discrimination to the PFGE type, providing potential benefits to epidemiological studies and the possibility of deciphering source attribution of cases.

Specific detection of Campylobacter jejuni from faeces using single nucleotide polymorphisms.

Specimens of human faeces were tested by a rapid strategy for detection of Campylobacter jejuni lineages by the presence of specific single nucleotide polymorphisms (SNPs) based on the C. jejuni multi locus sequence typing (MLST) scheme. This strategy was derived from analysis of the MLST databases to identify clonal complex specific SNPs followed by the design of real-time PCR assays to enable identification of six major C. jejuni clonal complexes associated with cases of human infection. The objective was to use the MLST SNP-based assays for the direct detection of C. jejuni by clonal complex from specimens of human faeces, and then confirm the accuracy of the clonal complex designation from the SNP-based assays by performing MLST on the cultured faecal material, this targeted at determining the validity of direct molecular specimen identification. Results showed it was possible to identify 38% of the isolates to one of the six major MLST clonal complexes using a rapid DNA extraction method directly from faeces in under 3 h. This method provides a novel strategy for the use of real-time PCR for detection and characterization beyond species level, supplying real-time epidemiological data, which is comparable with MLST results.

Real-time single-nucleotide polymorphism profiling using Taqman technology for rapid recognition of Campylobacter jejuni clonal complexes.

The rapid identification of Campylobacter jejuni isolates to strain level would significantly inform the public health investigation of C. jejuni infection. Conceptual advances provided by multilocus sequence typing (MLST) have established the clonal complex as an important epidemiological group at the strain level, enabling accurate and phylogenetically valid strain identification for C. jejuni. The development of real-time PCR assays for allelic discrimination of strain-associated single-nucleotide polymorphisms (SNPs) based upon MLST locus alleles offers one possible approach for rapid strain detection. SNPs defining key alleles diagnostic for the most prevalent clonal complexes were identified following a detailed analysis of the available MLST data. Real-time Taqman allelic discrimination assays designed to detect the SNPs specific for six major clonal complexes, ST-21, ST-45, ST-48, ST-61, ST-206 and ST-257, were developed, allowing the rapid detection of C. jejuni isolates and preliminary strain identification. This will provide an important complementary technique to sequence typing for rapid detection and strain characterization to inform in real-time the public health management and investigation of C. jejuni infections.

Identification of Campylobacter jejuni multilocus sequence type ST-21 clonal complex by single-nucleotide polymorphism analysis.

Conserved single-nucleotide polymorphisms (SNPs) which characterize the allelic profile of the major epidemiological lineage ST-21 were identified from the alleles within the current Campylobacter jejuni multilocus sequence typing (MLST) database. Allelic discrimination assays were designed for the detection of SNPs, enabling rapid strain profiling for clonal complex ST-21. This method is suitable for epidemiological investigations and is complementary to full MLST.