Michelle M. Nerandzic

Evaluation of an automated ultraviolet radiation device for decontamination of Clostridium difficile and other healthcare-associated pathogens in hospital rooms

BackgroundEnvironmental surfaces play an important role in transmission of healthcare-associated pathogens. There is a need for new disinfection methods that are effective against Clostridium difficile spores, but also safe, rapid, and automated.MethodsThe Tru-D™ Rapid Room Disinfection device is a mobile, fully-automated room decontamination technology that utilizes ultraviolet-C irradiation to kill pathogens. We examined the efficacy of environmental disinfection using the Tru-D device in the laboratory and in rooms of hospitalized patients. Cultures for C. difficile, methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin-resistant Enterococcus (VRE) were collected from commonly touched surfaces before and after use of Tru-D.ResultsOn inoculated surfaces, application of Tru-D at a reflected dose of 22,000 μWs/cm2 for ~45 minutes consistently reduced recovery of C. difficile spores and MRSA by >2-3 log10 colony forming units (CFU)/cm2 and of VRE by >3-4 log10 CFU/cm2. Similar killing of MRSA and VRE was achieved in ~20 minutes at a reflected dose of 12,000 μWs/cm2, but killing of C. difficile spores was reduced. Disinfection of hospital rooms with Tru-D reduced the frequency of positive MRSA and VRE cultures by 93% and of C. difficile cultures by 80%. After routine hospital cleaning of the rooms of MRSA carriers, 18% of sites under the edges of bedside tables (i.e., a frequently touched site not easily amenable to manual application of disinfectant) were contaminated with MRSA, versus 0% after Tru-D (P < 0.001). The system required <5 minutes to set up and did not require continuous monitoring.ConclusionsThe Tru-D Rapid Room Disinfection device is a novel, automated, and efficient environmental disinfection technology that significantly reduces C. difficile, VRE and MRSA contamination on commonly touched hospital surfaces.

Comparison of Clinical and Microbiological Response to Treatment of Clostridium difficile–Associated Disease with Metronidazole and Vancomycin

BACKGROUND There have been recent reports of frequent treatment failure associated with the use of metronidazole for treatment of Clostridium difficile-associated disease. We tested the hypothesis that treatment failure with metronidazole is associated with a suboptimal microbiological response in comparison with that of vancomycin. METHODS We conducted a 9-month prospective observational study of patients with C. difficile-associated disease. Cox proportional hazards models were used to compare metronidazole-treated and vancomycin-treated patients in terms of time to resolution of diarrhea and time to reduction of C. difficile in stool to an undetectable level. RESULTS Of 52 study patients with C. difficile-associated disease, 34 (65%) received initial therapy with oral metronidazole, and 18 (35%) received initial therapy with oral vancomycin. Diarrhea resolved in >90% of patients who completed 10 days of treatment with either agent. However, vancomycin-treated patients were more likely to develop undetectable levels of C. difficile (adjusted hazard ratio, 3.99; 95% confidence interval, 1.41-11.3;P = .009) and to have resolution of diarrhea (adjusted hazard ratio, 4.17; 95% confidence interval, 1.53-11.40;P = .005) during the first 5 days of therapy. Ten metronidazole-treated patients (29%) had their treatment changed to oral vancomycin because of persistent symptoms. Seven (70%) of these 10 patients had <1 log reduction in C.difficile concentration; however, only 4 had completed > or = 6 days of metronidazole treatment at the time of the treatment change. CONCLUSION In an observational study with a limited number of subjects, a majority of patients with C. difficile-associated disease responded to therapy with metronidazole or vancomycin. Failure with metronidazole treatment may be attributable to a slower and less consistent microbiological response than that with oral vancomycin treatment.

Risk factors and outcomes associated with severe Clostridium difficile infection in children

Background: The incidence and severity of Clostridium difficile infection (CDI) is increasing among adults; however, little is known about the epidemiology of CDI among children. Methods: We conducted a nested case-control study to identify the risk factors for and a prospective cohort study to determine the outcomes associated with severe CDI at 2 childrens hospitals. Severe CDI was defined as CDI and at least 1 complication or ≥2 laboratory or clinical indicators consistent with severe disease. Studied outcomes included relapse, treatment failure, and CDI-related complications. Isolates were tested to determine North American pulsed-field gel electrophoresis type 1 lineage. Results: We analyzed 82 patients with CDI, of whom 48 had severe disease. Median age in years was 5.93 (1.78–12.16) and 1.83 (0.67–8.1) in subjects with severe and nonsevere CDI, respectively (P = 0.012). All patients with malignancy and CDI had severe disease. Nine subjects (11%) had North American pulsed-field gel electrophoresis type 1 isolates. Risk factors for severe disease included age (adjusted odds ratio [95% confidence interval]: 1.12 [1.02, 1.24]) and receipt of 3 antibiotic classes in the 30 days before infection (3.95 [1.19, 13.11]). If infants less than 1 year of age were excluded, only receipt of 3 antibiotic classes remained significantly associated with severe disease. Neither the rate of relapse nor treatment failure differed significantly between patients with severe and nonsevere CDI. There was 1 death. Conclusions: Increasing age and exposure to multiple antibiotic classes were risk factors for severe CDI. Although most patients studied had severe disease, complications were infrequent. Relapse rates were similar to those reported in adults.

What is on that keyboard? Detecting hidden environmental reservoirs of Clostridium difficile during an outbreak associated with North American pulsed-field gel electrophoresis type 1 strains

BACKGROUND Numerous studies have demonstrated that environmental surfaces in the rooms of patients with Clostridium difficile infection (CDI) are often contaminated with spores. However, less information is available regarding the frequency of contamination of environmental surfaces outside of CDI isolation rooms. METHODS We performed a point-prevalence culture survey for C difficile in rooms of patients not in isolation for CDI, in physician and nurse work areas, and on portable equipment, including pulse oximetry devices, electrocardiogram machines, mobile computers, and medication distribution carts. Isolates were characterized by assessment of toxin production, polymerase chain reaction (PCR) ribotyping, and PCR for binary toxin genes. RESULTS Of 105 nonisolation rooms, 17 (16%) were contaminated with toxin-producing C difficile, with the highest rate of contamination on the spinal cord injury unit (32%). Of 87 surfaces cultured outside of patient rooms, 20 (23%) were contaminated, including 9 of 29 (31%) in physician work areas, 1 of 10 (10%) in nurse work areas, and 9 of 43 (21%) portable pieces of equipment, including a pulse oximetry finger probe, medication carts, and bar code scanners on medication carts. Of 26 isolates subjected to typing, 19 (73%) matched ribotype patterns detected in stool samples from CDI patients and 13 (50%) were epidemic, binary toxin-positive strains. CONCLUSION In the context of a CDI outbreak, we found that environmental contamination was common in nonisolation rooms, in physician and nurse work areas, and on portable equipment. Further research is needed to determine whether contamination in these areas plays a significant role in transmission.

Effective and Reduced-Cost Modified Selective Medium for Isolation of Clostridium difficile

ABSTRACT Both for epidemiologic studies and for diagnostic testing, there is a need for effective, economical, and readily available selective media for the culture of Clostridium difficile. We have developed a reduced-cost substitute for cycloserine-cefoxitin-fructose agar (CCFA), which is an effective but expensive selective medium for C. difficile. The modified medium, called C. difficile brucella agar (CDBA), includes an enriched brucella base as a substitute for proteose peptone no. 2, and the concentration of sodium taurocholate has been reduced from 0.1% to 0.05%. To compare the sensitivities and selectivities of CDBA and CCFA, cultures for C. difficile were performed using stool samples from patients with C. difficile-associated disease. CDBA was as sensitive as CCFA for the recovery of C. difficile, with a similar frequency of breakthrough growth of stool microflora (25% versus 31%, respectively). A liquid formulation of the modified medium, termed C. difficile brucella broth (CDBB), stimulated rapid germination and outgrowth of C. difficile spores, at a rate comparable to that in cycloserine-cefoxitin-fructose broth. Our results suggest that CDBA and CDBB are sensitive, selective, and reduced-cost media for the recovery of C. difficile from stool samples.

Reduced Acquisition and Overgrowth of Vancomycin-Resistant Enterococci and Candida Species in Patients Treated With Fidaxomicin Versus Vancomycin for Clostridium difficile Infection

Fidaxomicin causes less disruption of anaerobic microbiota during treatment of Clostridium difficile infection (CDI) than vancomycin and has activity against many vancomycin-resistant enterococci (VRE). In conjunction with a multicenter randomized trial of fidaxomicin versus vancomycin for CDI treatment, we tested the hypothesis that fidaxomicin promotes VRE and Candida species colonization less than vancomycin. Stool was cultured for VRE and Candida species before and after therapy. For patients with negative pretreatment cultures, the incidence of VRE and Candida species acquisition was compared. For those with preexisting VRE, the change in concentration during treatment was compared. The susceptibility of VRE isolates to fidaxomicin was assessed. Of 301 patients, 247 (82%) had negative VRE cultures and 252 (84%) had negative Candida species cultures before treatment. In comparison with vancomycin-treated patients, fidaxomicin-treated patients had reduced acquisition of VRE (7% vs 31%, respectively; P < .001) and Candida species (19% vs 29%, respectively; P = .03). For patients with preexisting VRE, the mean concentration decreased significantly in the fidaxomicin group (5.9 vs 3.8 log10 VRE/g stool; P = .01) but not the vancomycin group (5.3 vs 4.2 log10 VRE/g stool; P = .20). Most VRE isolates recovered after fidaxomicin treatment had elevated fidaxomicin minimum inhibitory concentrations (MICs; MIC90, 256 µg/mL), and subpopulations of VRE with elevated fidaxomicin MICs were common before therapy. Fidaxomicin was less likely than vancomycin to promote acquisition of VRE and Candida species during CDI treatment. However, selection of preexisting subpopulations of VRE with elevated fidaxomicin MICs was common during fidaxomicin therapy. Clinical Trials Registration. NCT00314951.

Triggering Germination Represents a Novel Strategy to Enhance Killing of Clostridium difficile Spores

Background Clostridium difficile is an anaerobic, spore-forming bacterium that is the most common cause of healthcare-associated diarrhea in developed countries. Control of C. difficile is challenging because the spores are resistant to killing by alcohol-based hand hygiene products, antimicrobial soaps, and most disinfectants. Although initiation of germination has been shown to increase susceptibility of spores of other bacterial species to radiation and heat, it was not known if triggering of germination could be a useful strategy to increase susceptibility of C. difficile spores to radiation or other stressors. Principal Findings Here, we demonstrated that exposure of dormant C. difficile spores to a germination solution containing amino acids, minerals, and taurocholic acid resulted in initiation of germination in room air. Germination of spores in room air resulted in significantly enhanced killing by ultraviolet-C (UV-C) radiation and heat. On surfaces in hospital rooms, application of germination solution resulted in enhanced eradication of spores by UV-C administered by an automated room decontamination device. Initiation of germination under anaerobic, but not aerobic, conditions resulted in increased susceptibility to killing by ethanol, suggesting that exposure to oxygen might prevent spores from progressing fully to outgrowth. Stimulation of germination also resulted in reduced survival of spores on surfaces in room air, possibly due to increased susceptibility to stressors such as oxygen and desiccation. Conclusions Taken together, these data demonstrate that stimulation of germination could represent a novel method to enhance killing of spores by UV-C, and suggest the possible application of this strategy as a means to enhance killing by other agents.

Evaluation of a Pulsed Xenon Ultraviolet Disinfection System for Reduction of Healthcare-Associated Pathogens in Hospital Rooms

OBJECTIVE To determine the effectiveness of a pulsed xenon ultraviolet (PX-UV) disinfection device for reduction in recovery of healthcare-associated pathogens. SETTING Two acute-care hospitals. METHODS We examined the effectiveness of PX-UV for killing of Clostridium difficile spores, methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin-resistant Enterococcus (VRE) on glass carriers and evaluated the impact of pathogen concentration, distance from the device, organic load, and shading from the direct field of radiation on killing efficacy. We compared the effectiveness of PX-UV and ultraviolet-C (UV-C) irradiation, each delivered for 10 minutes at 4 feet. In hospital rooms, the frequency of native pathogen contamination on high-touch surfaces was assessed before and after 10 minutes of PX-UV irradiation. RESULTS On carriers, irradiation delivered for 10 minutes at 4 feet from the PX-UV device reduced recovery of C. difficile spores, MRSA, and VRE by 0.55±0.34, 1.85±0.49, and 0.6±0.25 log10 colony-forming units (CFU)/cm2, respectively. Increasing distance from the PX-UV device dramatically reduced killing efficacy, whereas pathogen concentration, organic load, and shading did not. Continuous UV-C achieved significantly greater log10CFU reductions than PX-UV irradiation on glass carriers. On frequently touched surfaces, PX-UV significantly reduced the frequency of positive C. difficile, VRE, and MRSA culture results. CONCLUSIONS The PX-UV device reduced recovery of MRSA, C. difficile, and VRE on glass carriers and on frequently touched surfaces in hospital rooms with a 10-minute UV exposure time. PX-UV was not more effective than continuous UV-C in reducing pathogen recovery on glass slides, suggesting that both forms of UV have some effectiveness at relatively short exposure times.

Examination of Potential Mechanisms To Explain the Association between Proton Pump Inhibitors and Clostridium difficile Infection

ABSTRACT Proton pump inhibitors (PPIs) have been associated with Clostridium difficile infection (CDI) in several recent studies. However, other studies have not shown this association, and the mechanism by which PPIs might promote CDI has not been elucidated. We hypothesized two possible mechanisms of causation: first, by raising pH, PPIs may prevent gastric contents from killing C. difficile spores; second, gastric contents of PPI-treated patients may promote germination and outgrowth of C. difficile spores. Survival rates of spores from six different strains of C. difficile in acidic gastric contents were assessed using quantitative cultures on selective media. Germination and outgrowth of spores were assessed by heat shock at 80°C, phase-contrast microscopy, and ethanol shock after incubation for 24 h in the gastric contents of patients and in the gastric, small intestinal, and cecal contents of mice. C. difficile spores survived and remained dormant in nonbilious gastric contents with acidic pH. Germination did not occur in unmodified gastric contents of patients but did occur with the addition of taurocholic acid and amino acids. In mice, germination did not occur in gastric contents but did occur in small intestinal and cecal contents. In summary, C. difficile spores survived in acidic gastric contents and did not undergo germination and outgrowth in gastric contents, probably due to lack of essential germinants, such as taurocholic acid. Our results suggest that the effects of PPIs in the stomach do not contribute to the pathogenesis of CDI.

Clinical and Infection Control Implications of Clostridium difficile Infection With Negative Enzyme Immunoassay for Toxin

In a prospective study of 132 patients with a diagnosis of Clostridium difficile infection (CDI) by polymerase chain reaction, 43 (32%) had enzyme immunoassay (EIA) results negative for toxin. EIA-negative patients with CDI did not differ in clinical presentation from EIA-positive patients and presented a similar risk for transmission of spores.