Emma L. Best

The Potential for Airborne Dispersal of Clostridium difficile from Symptomatic Patients

BACKGROUND. The high transmissibility and widespread environmental contamination by Clostridium difficile suggests the possibility of airborne dissemination of spores. We measured airborne and environmental C. difficile adjacent to patients with symptomatic C. difficile infection (CDI). METHODS. We conducted air sampling adjacent to 63 patients with CDI for 180 h in total and for 101 h in control settings. Environmental samples were obtained from surfaces adjacent to the patient and from communal areas of the ward. C. difficile isolates were characterized by ribotyping and multilocus variable-number tandem-repeat analysis to determine relatedness. RESULTS. Of the first 50 patients examined (each for 1 h), only 12% had positive air samples, most frequently those with active symptoms of CDI (10%, vs 2% for those with no symptoms). We intensively sampled the air around 10 patients with CDI symptoms, each for 10 h over 2 days, as well as a total of 346 surface sites. C. difficile was isolated from the air in the majority of these cases (7 of 10 patients tested) and from the surfaces around 9 of the patients; 60% of patients had both air and surface environments that were positive for C. difficile. Molecular characterization confirmed an epidemiological link between airborne dispersal, environmental contamination, and CDI cases. CONCLUSIONS. Aerosolization of C. difficile occurs commonly but sporadically in patients with symptomatic CDI. This may explain the widespread dissemination of epidemic strains. Our results emphasize the importance of single-room isolation as soon as possible after the onset of diarrhea to limit the dissemination of C. difficile.

Models for the study of Clostridium difficile infection

Models of Clostridium difficile infection (C. difficile) have been used extensively for Clostridium difficile (C. difficile) research. The hamster model of C. difficile infection has been most extensively employed for the study of C. difficile and this has been used in many different areas of research, including the induction of C. difficile, the testing of new treatments, population dynamics and characterization of virulence. Investigations using in vitro models for C. difficile introduced the concept of colonization resistance, evaluated the role of antibiotics in C. difficile development, explored population dynamics and have been useful in the evaluation of C. difficile treatments. Experiments using models have major advantages over clinical studies and have been indispensible in furthering C. difficile research. It is important for future study programs to carefully consider the approach to use and therefore be better placed to inform the design and interpretation of clinical studies.

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

ABSTRACT 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.

Susceptibility of Clostridium difficile isolates from a Phase 2 clinical trial of cadazolid and vancomycin in C. difficile infection

Objectives The aim of this study was to evaluate the susceptibilities of Clostridium difficile isolates to cadazolid, a novel antibiotic for the treatment of C. difficile infection. Methods Ribotyping and susceptibilities were determined for C. difficile isolates from a multicentre, double-blind, Phase 2 study of oral cadazolid in patients with C. difficile infection (NCT01222702, ClinicalTrials.gov; EudraCT 2010-020941-29, European Clinical Trials Database). Patients were randomized to receive 250, 500 or 1000 mg of cadazolid twice daily or 125 mg of vancomycin four times daily, for 10 days. MICs of cadazolid, vancomycin, fidaxomicin, linezolid and moxifloxacin were determined at baseline for all patients and post-baseline for patients with clinical failure or recurrence, using the agar dilution method. Results Seventy-eight of 84 patients had an evaluable toxigenic C. difficile isolate at baseline. The most frequent PCR ribotype was 027 (15.4%). Cadazolid MICs for baseline isolates (including epidemic strain 027) ranged from 0.06 to 0.25 mg/L. Baseline cadazolid MICs were similar to those of fidaxomicin and lower than those of vancomycin, linezolid and moxifloxacin. For each clinical outcome group (clinical cure, clinical failure, sustained clinical response and clinical failure or recurrence), the baseline cadazolid MIC range was 0.06–0.25 mg/L. Mean (min–max) cadazolid faecal concentration (μg/g) on day 5 was 884 (101–2710), 1706 (204–4230) and 3226 (1481–12 600) for the doses 250, 500 and 1000 mg, respectively. Conclusions For all cadazolid doses, the faecal concentration was in excess of several thousand-fold the MIC90 for C. difficile. The MIC of cadazolid for all C. difficile isolates, including epidemic strains, was low and in the same narrow range regardless of treatment outcome.

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.

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.

Molecular, microbiological and clinical characterization of Clostridium difficile isolates from tertiary care hospitals in Colombia

In Colombia, the epidemiology and circulating genotypes of Clostridium difficile have not yet been described. Therefore, we molecularly characterized clinical isolates of C.difficile from patients with suspicion of C.difficile infection (CDI) in three tertiary care hospitals. C.difficile was isolated from stool samples by culture, the presence of A/B toxins were detected by enzyme immunoassay, cytotoxicity was tested by cell culture and the antimicrobial susceptibility determined. After DNA extraction, tcdA, tcdB and binary toxin (CDTa/CDTb) genes were detected by PCR, and PCR-ribotyping performed. From a total of 913 stool samples collected during 2013–2014, 775 were included in the study. The frequency of A/B toxins-positive samples was 9.7% (75/775). A total of 143 isolates of C.difficile were recovered from culture, 110 (76.9%) produced cytotoxic effect in cell culture, 100 (69.9%) were tcdA+/tcdB+, 11 (7.7%) tcdA-/tcdB+, 32 (22.4%) tcdA-/tcdB- and 25 (17.5%) CDTa+/CDTb+. From 37 ribotypes identified, ribotypes 591 (20%), 106 (9%) and 002 (7.9%) were the most prevalent; only one isolate corresponded to ribotype 027, four to ribotype 078 and four were new ribotypes (794,795, 804,805). All isolates were susceptible to vancomycin and metronidazole, while 85% and 7.7% were resistant to clindamycin and moxifloxacin, respectively. By multivariate analysis, significant risk factors associated to CDI were, staying in orthopedic service, exposure to third-generation cephalosporins and staying in an ICU before CDI symptoms; moreover, steroids showed to be a protector factor. These results revealed new C. difficile ribotypes and a high diversity profile circulating in Colombia different from those reported in America and European countries.

Role of surface energy and nano-roughness in the removal efficiency of bacterial contamination by nonwoven wipes from frequently touched surfaces

Abstract Healthcare associated infections (HCAIs) are responsible for substantial patient morbidity, mortality and economic cost. Infection control strategies for reducing rates of transmission include the use of nonwoven wipes to remove pathogenic bacteria from frequently touched surfaces. Wiping is a dynamic process that involves physicochemical mechanisms to detach and transfer bacteria to fibre surfaces within the wipe. The purpose of this study was to determine the extent to which systematic changes in fibre surface energy and nano-roughness influence removal of bacteria from an abiotic polymer surface in dry wiping conditions, without liquid detergents or disinfectants. Nonwoven wipe substrates composed of two commonly used fibre types, lyocell (cellulosic) and polypropylene, with different surface energies and nano-roughnesses, were manufactured using pilot-scale nonwoven facilities to produce samples of comparable structure and dimensional properties. The surface energy and nano-roughness of some lyocell substrates were further adjusted by either oxygen (O2) or hexafluoroethane (C2F6) gas plasma treatment. Static adpression wiping of an inoculated surface under dry conditions produced removal efficiencies of between 9.4% and 15.7%, with no significant difference (p < 0.05) in the relative removal efficiencies of Escherichia coli, Staphylococcus aureus or Enterococcus faecalis. However, dynamic wiping markedly increased peak wiping efficiencies to over 50%, with a minimum increase in removal efficiency of 12.5% and a maximum increase in removal efficiency of 37.9% (all significant at p < 0.05) compared with static wiping, depending on fibre type and bacterium. In dry, dynamic wiping conditions, nonwoven wipe substrates with a surface energy closest to that of the contaminated surface produced the highest E. coli removal efficiency, while the associated increase in fibre nano-roughness abrogated this trend with S. aureus and E. faecalis. Plasma modification of the nano-roughness and surface energy of fibres in nonwoven wipes was found to influence the relative removal efficiencies of common bacterial pathogens from model healthcare surfaces under dynamic wiping conditions.

Pilot study to determine whether microbial contamination levels in hospital washrooms are associated with hand-drying method

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Factors affecting removal of bacterial pathogens from healthcare surfaces during dynamic wiping

Wiping of surfaces contaminated with pathogenic bacteria is a key strategy for combating the transmission of healthcare associated infections. It is essential to understand the extent to which removal of bacteria is modulated by fiber properties, biocidal liquid impregnation and applied hand pressure. The influence of intrinsic and extrinsic factors on the removal efficiencies of pathogenic bacteria was studied. Nonwoven wipes made of either hydrophobic (polypropylene) or hygroscopic (lyocell) fibers were manufactured and dynamic removal efficiency of bacteria studied. The single most important parameter affecting bacterial removal efficiency was impregnation with biocidal liquid (p < 0.05). For inherently hygroscopic 100% regenerated cellulose (lyocell) wipes impregnated with biocidal liquid, removal of E. coli, S. aureus and E. faecalis improved by increasing the fabric surface density and wiping pressure to their maximal values – 150 g.m–2 and 13.80 kN.m–2, respectively. For inherently hydrophobic 100% polypropylene nonwoven wipes, the same conditions maximized the removal efficiency of S. aureus, but for E. coli and E. faecalis a reduction in the wiping pressure to 4.68 kN.m–2 was required. Best practice involves the use of higher surface density wipes (150 g.m–2) containing regenerated cellulose fibers loaded with liquid biocide, and applied with the greatest possible wiping pressure.