Surface-layer protein A (SlpA) is a major contributor to host-cell adherence of Clostridium difficile.

Clostridium difficile is a leading cause of antibiotic-associated diarrhea, and a significant etiologic agent of healthcare-associated infections. The mechanisms of attachment and host colonization of C. difficile are not well defined. We hypothesize that non-toxin bacterial factors, especially those facilitating the interaction of C. difficile with the host gut, contribute to the initiation of C. difficile infection. In this work, we optimized a completely anaerobic, quantitative, epithelial-cell adherence assay for vegetative C. difficile cells, determined adherence proficiency under multiple conditions, and investigated C. difficile surface protein variation via immunological and DNA sequencing approaches focused on Surface-Layer Protein A (SlpA). In total, thirty-six epidemic-associated and non-epidemic associated C. difficile clinical isolates were tested in this study, and displayed intra- and inter-clade differences in attachment that were unrelated to toxin production. SlpA was a major contributor to bacterial adherence, and individual subunits of the protein (varying in sequence between strains) mediated host-cell attachment to different extents. Pre-treatment of host cells with crude or purified SlpA subunits, or incubation of vegetative bacteria with anti-SlpA antisera significantly reduced C. difficile attachment. SlpA-mediated adherence-interference correlated with the attachment efficiency of the strain from which the protein was derived, with maximal blockage observed when SlpA was derived from highly adherent strains. In addition, SlpA-containing preparations from a non-toxigenic strain effectively blocked adherence of a phylogenetically distant, epidemic-associated strain, and vice-versa. Taken together, these results suggest that SlpA plays a major role in C. difficile infection, and that it may represent an attractive target for interventions aimed at abrogating gut colonization by this pathogen.

Assessment of 30-day all-cause mortality in metronidazole-treated patients with Clostridium difficile infection.

The Society for Healthcare Epidemiology (SHEA) and the Infectious Diseases Society of America (IDSA) clinical practice guidelines for Clostridium difficile infection (CDI) help to define and make recommendations for the treatment of mild to moderate disease with metronidazole and severe disease with vancomycin. We retrospectively evaluated 285 patients who were initially treated with metronidazole and stratified them by severity of illness using the guideline criteria. We compared the outcomes in the 2 groups including the need to change therapy, recurrences, and 30-day all-cause mortality. There were no differences in recurrence rates based on severity of disease. From the multivariate analysis, severe CDI was predictive of 30-day all-cause mortality (odds ratio (OR) 1.98, 95% confidence interval (CI) 1.07-3.67, p = 0.03), after controlling for ICU stay prior to diagnosis (OR 2.94, 95% CI 1.60-5.41. p = 0.001), age (OR 1.02, 95% CI 1.004-1.05, p = 0.02), and the modified Charlson score (OR 1.31, 95% CI 1.14-1.49, p < 0.0001).

Decreasing incidence of Staphylococcus aureus bacteremia over 9 years: greatest decline in community-associated methicillin-susceptible and hospital-acquired methicillin-resistant isolates.

BACKGROUND: The impact of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) emergence on the epidemiology of S aureus bacteremia (SAB) is not well documented. METHODS: This was an observational study of adult (aged ≥18 years) inpatients with SAB in a single 808-bed teaching hospital during 2002-2003, 2005-2006, 2008-2009, and 2010 with period-stratified SAB rate, onset mode, patient characteristics, and outcome. RESULTS: We encountered a total of 1,098 cases over the entire study period. The rate decreased steadily over time (from 6.64/10(3) discharges in 2002-2003 to 6.49/10(3) in 2005-2006, 5.24/10(3) in 2008-2009, and 5.00/10(3) in 2010; P = .0001), with a greater decline in community-associated cases (0.99/10(3), 0.77/10(3), 0.58/10(3), and 0.40/10(3), respectively; P = .0005) compared with health care-associated cases (5.65/10(3), 5.72/10(3), 4.66/10(3), and 4.60/10(3), respectively; P = .005). The decline was principally in MSSA (3.11/10(3), 2.21/10(3), 2.24/10(3), and 1.75/10(3), respectively; P = .00006), including both community-associated (P = .0002) and health care-associated cases (P = .006). Although overall rate changes in MRSA were not significant (P = .09), hospital-onset MRSA decreased markedly (P < .00001), whereas CA-MRSA increased (P = .03). The all-cause 100-day mortality rate did not change significantly (25.6% for 2002-2003, 25.2% for 2005-2006, 28.1% for 2008-2009, and 32.2% for 2010; P = .10). Differences in MSSA/MRSA-associated mortality decreased (20.1% vs 30.6%, P = .03 for 2002-2003; 18.1% vs 28.9%, P = .05 for 2005-2006; 21.7% vs 32.9%, P = .05 for 2008-2009; and 29.3% vs 34.9, P = .5 for 2010). CONCLUSIONS: SAB incidence is decreasing, with the greatest decline in community-associated MSSA and hospital-onset MRSA cases. Most health care-associated cases currently are community-onset. MRSA/MSSA-related mortality is comparable. These changes are likely related to the emergence of CA-MRSA and the inpatient-to-outpatient shift in health care.

Gemcitabine-associated "pseudocellulitis" and "pseudosepsis": a case report and review of the literature.

Chemotherapeutic agents have been associated with sepsis and a variety of opportunistic and nonopportunistic infections. This was attributed to their immunosuppressive effects. Like all other chemotherapeutic agents, the use of gemcitabine has been associated with different infectious processes, yet many conditions that mimic infections have also been linked to its use. Pseudosepsis is a condition that should be added to these previously described conditions, such as gemcitabine-induced pseudocellulitis. We describe a patient who suffered from 2 different gemcitabine-induced adverse events including pseudocellulitis that was not related to prior lymphedema or radiation recall phenomenon and pseudosepsis wherein antibiotics have no role in the treatment, and the discontinuation of the offending agent resulted in the resolution of the patient's symptoms.

Current state of Clostridium difficile treatment options.

Recent reports of reduced response to standard therapies for Clostridium difficile infection (CDI) and the risk for recurrent CDI that is common with all currently available treatment agents have posed a significant challenge to clinicians. Current recommendations include metronidazole for treatment of mild to moderate CDI and vancomycin for severe CDI. Results from small clinical trials suggest that nitazoxanide and teicoplanin may be alternative options to standard therapies, whereas rifaximin has demonstrated success in uncontrolled trials for the management of multiple recurrences. Anecdotal reports have also suggested that tigecycline might be useful as an adjunctive agent for the treatment of severe complicated CDI. Reports of resistance will likely limit the clinical use of fusidic acid and bacitracin and, possibly, rifaximin if resistance to this agent becomes widespread. Treatment of patients with multiple CDI recurrences and those with severe complicated CDI is based on limited clinical evidence, and new treatments or strategies are needed.

Risk and prognostic factors among patients with bacteremia due to Eggerthella lenta.

Eggerthella lenta is a Gram-positive non-spore forming anaerobic commensal bacilli that can cause bacteremia due to abdominal or soft tissue sources. Patients are frequently bedridden and infection is associated with a high mortality rate. Absence of fever at presentation and need for ICU stay are risk factors for 30-day mortality.

Fidaxomicin: a novel macrocyclic antibiotic approved for treatment of Clostridium difficile infection.

Fidaxomicin, a nonabsorbed macrocyclic compound, is the first antimicrobial agent approved by the FDA for the treatment of Clostridium difficile infection (CDI) in adults over the last 25 years. It is bactericidal, and its mechanism of action relates to inhibition of a RNA polymerase at a site distinct from where rifamycins interact. Fidaxomicin, 200 milligrams by mouth twice daily, is not inferior to vancomycin, 125 milligrams by mouth 4 times daily, for treatment of CDI as determined by clinical response after 10 days of treatment and is superior to vancomycin for sustained response without recurrence 25 days after treatment completion. These results are a significant advance in the treatment of CDI and herald the development of narrow-spectrum anti-C. difficile agents that relatively spare the indigenous fecal microbiota. Continued vigilance for the development of resistance and unanticipated side affects will be important as the drug is introduced into clinical practice.

Lack of association of outcomes with treatment duration and microbiologic susceptibility data in Clostridium difficile infections in a non-NAP1/BI/027 setting.

BACKGROUND: Concerns regarding the poor response of severe Clostridium difficile infection (CDI) treated with metronidazole have arisen over the last 5 y. METHODS: We conducted a prospective, non-interventional study of CDI cases at our institution to evaluate the role of drug resistance, co-morbidities, and the emergence of hypervirulent strains on patient outcomes. A total of 118 adult inpatients with diarrhea and a positive stool for C. difficile toxin immunoassay had positive stool cultures and were included in the study. All 118 isolates had vancomycin and metronidazole susceptibility testing via the E-test method; rep-PCR was performed on 47 isolates. Of the 118 study patients, 107 were treated with either metronidazole or vancomycin. RESULTS: Initial therapy was metronidazole in 98.1% (n = 105) and vancomycin in 1.9% (n = 2) patients. Evaluable clinical response within 5 days of treatment was noted in 52.5% (52/99) of cases. The mean duration of treatment was 11.7 ± 7.2 days. The 30-day all-cause mortality rate was 24.6% (29/118). Recurrence occurred in 23.6% (21/89). A recent stay in the intensive care unit was associated with increased 30-day mortality (odds ratio 3.58, p = 0.012). There were no isolates resistant to metronidazole or vancomycin. Only 1 isolate was possibly related to the NAP1/BI/027 reference strain. No strain-related differences in deaths or recurrence were noted. CONCLUSIONS: Deaths related to CDI in our study appear to be related to multiple factors and did not appear to be independently related to antibiotic susceptibility, strain type, or treatment duration.

Clostridium difficile infection rates and spectrum of disease among peripartum women at one hospital from 2003 to 2007 with molecular typing analysis of recovered Clostridium difficile isolates.

BACKGROUND: Peripartum women are at risk for Clostridium difficile infection (CDI), but the risk magnitude and clinical disease spectrum are unknown. We determined the incidence and clinical features of CDI in peripartum women in the Loyola University Medical Center system and describe typing of C difficile isolates by restriction endonuclease analysis (REA). METHODS: A retrospective chart review of peripartum CDI from 2003 to 2007 was performed after identifying patients from the clinical laboratory log of positive C difficile toxin assays. Available stool samples were cultured and isolates typed using REA. RESULTS: We found 12 CDI cases over 5 years for an incidence of 0.7 cases/1,000 obstetrics ward admissions. Prior antibiotic use was documented in 11 (92%) cases, and 8 (67%) were health care facility associated. The rate of CDI following cesarean section was 2.2 per 1,000 live births compared with 0.2 per 1,000 following vaginal delivery (relative risk, 11.6; 95% confidence interval: 1.39-96.23). Typing revealed 4 different REA strain groups; 6 of the 7 REA types were toxin variants. CONCLUSION: CDI in peripartum women is similar to CDI in other groups except for age. CDI was caused by multiple REA types. Cesarean section may be a particular risk for CDI that develops in the postpartum period.

Human hypervirulent Clostridium difficile strains exhibit increased sporulation as well as robust toxin production.

Toxigenic Clostridium difficile strains produce two toxins (TcdA and TcdB) during the stationary phase of growth and are the leading cause of antibiotic-associated diarrhea. C. difficile isolates of the molecular type NAP1/027/BI have been associated with severe disease and hospital outbreaks worldwide. It has been suggested that these "hypervirulent" strains produce larger amounts of toxin and that a mutation in a putative negative regulator (TcdC) allows toxin production at all growth phases. To rigorously explore this possibility, we conducted a quantitative examination of the toxin production of multiple hypervirulent and nonhypervirulent C. difficile strains. Toxin gene (tcdA and tcdB) and toxin gene regulator (tcdR and tcdC) expression was also monitored. To obtain additional correlates for the hypervirulence phenotype, sporulation kinetics and efficiency were measured. In the exponential phase, low basal levels of tcdA, tcdB, and tcdR expression were evident in both hypervirulent and nonhypervirulent strains, but contrary to previous assumptions, toxin levels were below the detectable thresholds. While hypervirulent strains displayed robust toxin production during the stationary phase of growth, the amounts were not significantly different from those of the nonhypervirulent strains tested; further, total toxin amounts were directly proportional to tcdA, tcdB, and tcdR gene expression. Interestingly, tcdC expression did not diminish in stationary phase, suggesting that TcdC may have a modulatory rather than a strictly repressive role. Comparative genomic analyses of the closely related nonhypervirulent strains VPI 10463 (the highest toxin producer) and 630 (the lowest toxin producer) revealed polymorphisms in the tcdR ribosome binding site and the tcdR-tcdB intergenic region, suggesting that a mechanistic basis for increased toxin production in VPI 10463 could be increased TcdR translation and read-through transcription of the tcdA and tcdB genes. Hypervirulent isolates produced significantly more spores, and did so earlier, than all other isolates. Increased sporulation, potentially in synergy with robust toxin production, may therefore contribute to the widespread disease now associated with hypervirulent C. difficile strains.

Emergence of community-associated methicillin-resistant Staphylococcus aureus infection among patients with end-stage renal disease.

OBJECTIVE: To evaluate the frequency of infections due to community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strains among our patients with end-stage renal disease. DESIGN: Prospective observational clinical and laboratory study of patients in 2005. Molecular features of isolates recovered from these patients were compared with those of isolates recovered in 2000 from patients with end-stage renal disease. SETTING: A 600-bed urban academic medical center. PATIENTS: Thirty-two patients with end-stage renal disease and MRSA infection at the time of hospitalization from 2005 were evaluated. For comparison, laboratory analysis was performed for 17 MRSA isolates recovered from patients with end-stage renal disease in 2000. RESULTS: The patients from 2005 were more likely than the patients from 2000 to have infection with strains that carried the staphylococcal cassette chromosome (SCC) mec type IV complex (50% vs 11.8%; relative risk, 4.25 [95% confidence interval, 1.17-25.98]; P = .012) and the Panton-Valentine leukocidin toxin genes (25% vs 0%; P = .038). Eight patients from 2005 were infected with a strain that is identical to MRSA clone USA300 in terms of molecular type and presence of SCCmec type IV and Panton-Valentine leukocidin genes. Among the patients from 2005, those infected with SCCmec type IV strains (ie, CA-MRSA strains) and those infected with SCCmec type II strains (ie, healthcare-associated MRSA [HA-MRSA] strains) were similar with respect to demographic characteristics, risk factors, and outcomes. CONCLUSIONS: We documented an increased proportion of infections with CA-MRSA strains, including clone USA300, among our population of patients undergoing dialysis. Patients infected with CA-MRSA strains and HA-MRSA strains were similar with respect to presenting illness and outcomes.