Class of 2009 Abstract / OBJECTIVES: The purpose of the study was to determine the rate of Clostridium difficile infections (CDI) in hospitalized patients and the various factors that were associated with the risk of developing CDI by examining patient discharge data for hospitals in 37 states in the United States using Healthcare Cost and Utilization Project (HCUP). METHODS: Patient discharge information for all patients obtained using HCUP census for the years 2002-2005, either for primary or secondary (all-listed) occurrences of CDI using the ICD-9-CM code (008.45) specific for intestinal infections due to C. difficile, were included in the study. Regression analysis, either Generalized Linear Model log-link or power-link, or a logistic regression was employed to control for the multiple independent variables. RESULTS: The incidence rate for CDI was 9.4% for the years 2002-2005. Among the concomitant diagnoses and procedures, essential hypertension, volume depletion, congestive heart failure, urinary tract infection and venous catheterization were the top 5. The length of stay (LOS) for CDI was associated with being Black, Hispanic or Other race category, number of diagnoses and procedures, primary expected payer of Medicaid, private insurance and other (including worker’s compensation, CHAMPUS,CHAMPVA etc), and all groups classified based on median household income category for patient’s zip code. Predictors of CDI related to inpatient total hospital charges were being female, race (other than black), number of diagnoses and procedures, Death, LOS, patient location and with self-pay and no charge categories as primary expected payer. Predictors of higher CDI related inpatient hospital deaths were age, female sex, Hispanic race, number of diagnoses and procedures, LOS and having Medicaid, self-pay or other as primary expected payer. CONCLUSIONS: LOS, inpatient total hospital charges, and inpatient mortality were dependent on several patient and other characteristics.

Background: Accurate diagnostic methods for Clostridium difficile infection (CDI) are required for optimal patient management, appropriate implementation of infection control measures and surveillance. An assay that also provides rapid results, is easy to implement in a routine diagnostic lab and is cost-effective would be ideal. Laboratory testing for Clostridium difficile infection is rapidly evolving. Recently published literature has shown that immunoassays for toxin detection, whilst being cheap and easy to implement, lack sensitivity. Molecular diagnostics that are sensitive and provide rapid results are now available. However, the high cost of these assays is of concern. As reflected in the literature the optimal test or testing algorithm for Clostridium difficile infection diagnosis is not clear. Objectives: This study aimed to compare the performance of a real-time PCR assay and two immunoassays, and to establish the optimal testing strategy for Charlotte Maxeke Johannesburg Academic Hospital (CMJAH). Methods: Using toxigenic culture as the gold standard, the Roche PCR assay for the detection of the tcdC gene, the Immuno Card Toxins A & B immunoassay and the C. Diff Quik Chek Complete immunoassay were evaluated as stand alone assays and as part of testing algorithms. Results: The sensitivity, specificity, positive predictive value and negative predictive value of the various assays and algorithms ranged from 38% to 81%, 98% to 100%, 92% to 100% and 85% to 95%, respectively. The charge per sample tested varied widely depending on the assay and algorithm used. The maximum turnaround time ranged between four and twenty four hours. Conclusion: The algorithm combining glutamate dehydrogenase and toxin immunoassay testing of all samples followed by PCR testing of only a subset of samples, performed the best, providing accurate results rapidly and cost-effectively.

Les infections digestives à Clostridium difficile nécessitent une première étape de colonisation de l’écosystème intestinal. Avant l’âge de deux ans, la colonisation par C. difficile est fréquente mais paradoxalement le plus souvent asymptomatique. Nous avons montré que plus d’un tiers des enfants de 0-3 ans, et plus de 70% de ceux de 7 à 9 mois (15% pour les souches toxinogènes), étaient porteurs sains de C. difficile à l’hôpital et dans la communauté. Deux périodes d’acquisition de C. difficile ont été identifiées : néonatale ou 3-6 mois. Les souches infantiles de C. difficile étaient identiques aux souches isolées chez l’adulte, faisant du jeune enfant un réservoir potentiel de souches infectieuses. Nous avons également montré par méthode moléculaire que des changements en espèces dominantes du microbiote étaient associés à la colonisation par C. difficile. Bifidobacterium longum caractérisait le microbiote des enfants non colonisés, et pourrait participer à la résistance à la colonisation par C. difficile. / Gastrointestinal infections with Clostridium difficile require a first step of colonization of the intestinal ecosystem. Under the age of two years, C. difficile colonization is frequent but paradoxically most often asymptomatic. We have shown that more than a third of children 0-3 years and more than 70% of those from 7 to 9 months (15% for toxigenic strains) were healthy carriers of C. difficile in the hospital and in the community. Two C. difficile-acquisition periods were identified: neonatal or 3-6 months. The C. difficile strains from infants were identical to strains isolated from adults, making infants a potential reservoir of infectious strains. We also showed by molecular method that changes in dominant species of the microbiota were associated with colonization by C. difficile. Bifidobacterium longum characterized the microbiota of children not colonized by C. difficile, and could be involved in the colonization resistance process.

Clostridium difficile is a frequent cause of healthcare-associated infections (HAI) and is associated with increased risk of morbidity and mortality. Studies suggest environmental and host characteristics increase patient's susceptibility to C. difficile infection (CDI). However, few studies have examined the risk of CDI among those with diabetes or patients in the acute rehabilitation (AR) setting. A case-control study, using secondary data (n = 473), evaluated the relationship between CDI and diabetes and identified modifiable environmental exposures. An ecosocial framework was used to examine the relationship between these two complex diseases among hospitalized patients in an AR setting. Results of the multiple logistic regression showed that patients with diabetes experienced 2.5 times the risk for CDI (p = 0.03) compared to non-diabetic patients. Multiple logistic regression was also used to assess for modifiable exposures among AR patients with diabetes only. Findings from this sub-analysis found the significant exposures in this population were antibiotics (OR = 3.9; p = 0.01) and insulin use (OR = 2.6; p = 0.015), suggesting an effect on the intestinal microbiome. Understanding the relationship between CDI and diabetes among the AR population promotes positive social change through the reduction of CDI associated morbidity and mortality among diabetic patients. Findings from this study support antibiotic stewardship efforts across the spectrum of healthcare delivery and the development of new strategies to decrease the economic burden associated with CDI for individuals, healthcare facilities, and at the national level.

Healthcare-associated infections occur commonly in hospitals and have a major impact on patient well-being. The occurrence of the healthcare-associated infection, Clostridium difficile, has been occurring more frequently among hospitalized patients due to an epidemic strain, and is an important cause of antibiotic-associated diarrhea and colitis. This study examined the impact of several organizational factors on the occurrence of C. difficile infection (CDI) in hospitals using an institutional theory perspective. Administrative claims were utilized from University HealthSystem Consortium hospitals to obtain hospital-level data for the calendar year 2011. Data were available for 89 hospitals. Hospital-level analyses, negative binomial regression models, were conducted to test eight developed hypotheses and the associations between organizational factors and the incidence of CDI in hospitals. Cases of CDI were risk-adjusted for known factors associated with CDI. After controlling for factors known to be associated with CDI, the results of the analyses showed that one study hypothesis was supported. That is, hospitals with higher Leapfrog Group Safety Scores had CDI rates that were no different than hospitals with lower Safety Scores. Further, it was found that U.S. News and World Report Best Hospital Honor Roll member hospitals had significantly higher occurrence of CDI as compared to non-Honor Roll member hospitals, though it was predicted that there would be no difference in CDI rates. The organizational factors state-led CDI prevention collaboratives, state mandatory CDI reporting, Magnet status, the rate of central line-associated bloodstream infections and catheter-associated urinary tract infections, and CDI physician champions, were not significantly associated with CDI occurrence.

Abstract not available

Clostridium difficile is a leading cause of nosocomial infection in North America and a considerable challenge to healthcare professionals in hospitals and nursing homes. The Gram-positive bacterium produces two exotoxins, toxin A (TcdA) and toxin B (TcdB), which are the major virulence factors responsible for C. difficile-associated disease (CDAD) and are targets for CDAD therapy. In this work, recombinant single-domain antibody fragments (VHHs) which target the cell receptor binding domains of TcdA or TcdB were isolated from an immune, llama phage display library and characterized. Four VHHs (A4.2, A5.1, A20.1, and A26.8) were potent neutralizers of the cytopathic effects of TcdA in an in vitro assay and the neutralizing potency was enhanced when VHHs were administered in combinations. Epitope mapping experiments revealed that some synergistic combinations consisted of VHHs recognizing overlapping epitopes, an indication that factors other than mere epitope blocking are responsible for the increased neutralization. Binding assays revealed TcdA-specific VHHs neutralized TcdA by binding to sites other than the carbohydrate binding pocket of the toxin. The TcdB-specific VHHs failed to neutralize TcdB, as did a panel of human VL antibodies isolated from a synthetic library. To enhance the stability of the C. difficile TcdA-specific VHHs for oral therapeutic applications, the VHHs were expressed with an additional disulfide bond by introducing Ala/Gly54Cys and Ile78Cys mutations. The mutant VHHs were found to be well expressed, were non-aggregating monomers, retained low nM affinity for TcdA, and were capable of in vitro TcdA neutralization. Digestion of the VHHs with the major gastrointestinal proteases, at biologically relevant concentrations, revealed a significant increase in pepsin resistance for all mutants and an increase in chymotrypsin resistance for the majority of mutants without compromising inherent VHH trypsin resistance. Collectively, the second disulfide not only increased VHH thermal stability at neutral pH, as previously shown, but also represents a generic strategy to increase VHH stability at low pH and impart protease resistance. These are all desirable characteristics for the design of protein-based oral therapeutics. In conclusion, llama VHHs represent a class of novel, non-antibiotic inhibitors of infectious disease virulence factors such as C. difficile toxins.

Clostridium difficile is a leading cause of nosocomial infection in North America and a considerable challenge to healthcare professionals in hospitals and nursing homes. The Gram-positive bacterium produces two exotoxins, toxin A (TcdA) and toxin B (TcdB), which are the major virulence factors responsible for C. difficile-associated disease (CDAD) and are targets for CDAD therapy. In this work, recombinant single-domain antibody fragments (VHHs) which target the cell receptor binding domains of TcdA or TcdB were isolated from an immune, llama phage display library and characterized. Four VHHs (A4.2, A5.1, A20.1, and A26.8) were potent neutralizers of the cytopathic effects of TcdA in an in vitro assay and the neutralizing potency was enhanced when VHHs were administered in combinations. Epitope mapping experiments revealed that some synergistic combinations consisted of VHHs recognizing overlapping epitopes, an indication that factors other than mere epitope blocking are responsible for the increased neutralization. Binding assays revealed TcdA-specific VHHs neutralized TcdA by binding to sites other than the carbohydrate binding pocket of the toxin. The TcdB-specific VHHs failed to neutralize TcdB, as did a panel of human VL antibodies isolated from a synthetic library. To enhance the stability of the C. difficile TcdA-specific VHHs for oral therapeutic applications, the VHHs were expressed with an additional disulfide bond by introducing Ala/Gly54Cys and Ile78Cys mutations. The mutant VHHs were found to be well expressed, were non-aggregating monomers, retained low nM affinity for TcdA, and were capable of in vitro TcdA neutralization. Digestion of the VHHs with the major gastrointestinal proteases, at biologically relevant concentrations, revealed a significant increase in pepsin resistance for all mutants and an increase in chymotrypsin resistance for the majority of mutants without compromising inherent VHH trypsin resistance. Collectively, the second disulfide not only increased VHH thermal stability at neutral pH, as previously shown, but also represents a generic strategy to increase VHH stability at low pH and impart protease resistance. These are all desirable characteristics for the design of protein-based oral therapeutics. In conclusion, llama VHHs represent a class of novel, non-antibiotic inhibitors of infectious disease virulence factors such as C. difficile toxins.

Clostridium difficile has been recognized as one of the leading causes of nosocomial diarrhea and pseudomembranous colitis in human hospitals and nursing homes since the 1970s; however, recent occurrences of community-acquired cases have led researchers to search for additional sources of these infections. Some of the possible sources being investigated include food animals and retail meat. The objective of this study was to compare the prevalence and genotypic characteristics of C. difficile isolated from a closed population in Texas consisting of both humans and swine. Implicit in this objective, we seek to investigate the possible food safety and occupational risks associated with swine and C. difficile. Isolation of C. difficile was performed utilizing an enrichment technique and restrictive media. Polymerase chain reaction (PCR) was used to test for the presence of the toxin A and B genes, the tcdC gene deletion, and the binary toxin gene. Genotypic characteristics were compared using PCR toxinotyping and pulsed-field gel electrophoresis (PFGE). Antimicrobial susceptibility was tested using commercially available tests (ETest®) for 11 different antibiotics. Statistical comparisons (both parametric and non-parametric, and appropriate to the data) were performed both between and among host species. We tested 2,292 aggregated human wastewater samples and 2,936 swine fecal samples from 2004 to 2006 and found 271 (11.8 percent) and 252 (8.6 percent) to be positive for C. difficile, respectively. The prevalence of C. difficile among swine production groups differed significantly (p<0.05); however, prevalence in the human occupational group cohorts (swine workers and non-workers) did not differ (p=0.81). The majority of the human and swine isolates were a PFGE NAP7 (a variant pattern with 90.5 percent similarity) toxinotype V strain. Antimicrobial resistance levels and multi-resistance patterns were generally similar between host species; however, there was decreased susceptibility (p<0.05) to ampicillin, clindamycin, and imipenem observed in swine isolates, whereas there was decreased susceptibility (p<0.05) to ciprofloxacin in the human isolates. The similarity in C. difficile prevalence between swine workers and non-workers suggests a low occupational hazard of working with swine as it relates to C. difficile source. We also found that there is a decreased prevalence of C. difficile in late production groups in swine suggesting a lowered risk of food-borne exposure. However, the majority of the isolates derived from the human wastewater and swine appeared to be of very similar strain types, suggesting that a common environmental point source predominates for both hosts.

Clostridium difficile is the most common infectious cause of nosocomial diarrhea, affecting thousands of patients annually and exacting enormous costs on the U.S. health care system. Early diagnosis is critical to prevent transmission and reduce morbidity and mortality, yet sensitive and specific diagnostic tests with a quick turnaround time are lacking. The objective of this study was to determine if a new commercially available real time polymerase chain reaction (PCR) test would prove more rapid, sensitive and specific than standard methods for the diagnosis of C. difficile infection (CDI). BD GeneOhm Cdiff assay, a real-time PCR assay for detection of C. difficile toxin B (tcdB) gene, was compared with Tox A/B II ELISA and a two-step algorithm which includes C. Diff Chek-60 Glutamate Dehydrogenase (GDH)-antigen assay followed by cytotoxin neutralization. Four-hundred liquid or semisolid stools submitted for diagnostic C. difficile testing were selected: 200 GDH antigen-positive and 200 GDH antigen-negative. All samples were tested by the C. Diff Chek-60 GDH antigen, cytotoxin neutralization, Toxin A/B II ELISA, and BD GeneOhm Cdiff assay. Discrepant specimens were tested by toxigenic culture as an independent gold standard. Chart review was performed on patients with discrepant specimens. As BD GeneOhm Cdiff assay was not FDA-cleared at the time of study, PCR results were not clinically reported. Of 200 GDH-positive samples, 71 were positive by Tox A/B II, 88 were positive by the two-step method, 93 were positive by PCR, and 96 were positive by GDH-antigen only. Of 200 GDH-negative samples, 3 were positive by PCR only. Toxigenic culture was performed on 41 samples with discrepant results and 39 were culture-positive. After culture resolution of discrepants, Tox A/B II detected 70 (66.7%), the two-step method detected 87 (82.9%), and PCR detected 96 (91.4%) of 105 true positives. The BD Gene-Ohm Cdiff assay was more sensitive in detecting toxigenic C. difficile than Tox A/B II (p <0.0001); however, the difference between PCR and the two-step method was not significant (p=0.1237). The BD GeneOhm Cdiff assay took a similar amount of time to perform as the Tox A/B II and was more rapid than the two-step method. Chart review revealed that 18 patients with cytotoxin-negative, PCR-positive discrepant samples were given 1-2 days of therapy (n=8), or no treatment at all (n=10). Yet symptoms resolved and no further C. difficile testing was requested for 13 of 18 patients for 6-8 months after hospital discharge. Only one patient had a subsequent cytotoxin positive stool submitted 22 days after the study sample was tested. Enhanced sensitivity and rapid turnaround time make the BD GeneOhm Cdiff assay an important advance in the diagnosis of toxigenic C. difficile infection. The BD GeneOhm Cdiff assay is significantly more sensitive than a commonly-used ELISA toxin assay and has a sensitivity and specificity comparable to the two-step method. Its turnaround time is similar to ELISA toxin assays and more rapid than the two-step method. Disadvantages to implementation of BD GeneOhm Cdiff assay include increased cost and potential treatment of asymptomatic carriers and mild, self-resolving disease.