Asymptomatic Clostridium difficile colonization is common in hospitalized patients. Existing C. difficile assay comparisons lack data on severity of diarrhea or patient outcomes, limiting the ability to interpret their results in regard to the diagnosis of C. difficile infection (CDI). The objective of this study was to measure how including patient presentation with the C. difficile assay result impacted assay performance to diagnose CDI. Stool specimens from 150 patients that met inclusion and exclusion criteria were selected. Nine methods to detect C. difficile in stool were evaluated. All patients were interviewed prospectively to assess diarrhea severity. We then assessed how different reference standards, with and without the inclusion of patient presentation, impact the sensitivity, specificity, and positive and negative predictive values of the assays to diagnose CDI. There were minimal changes in sensitivity; however, specificity was significantly lower for the assays Tox A/B II, C. diff Chek-60, BD GeneOhm Cdiff, Xpert C. difficile, and Illumigene C. difficile and for toxigenic culture (P was <0.01 for all except Tox A/B II from fresh stool, for which the P value was 0.016) when the reference standard was recovery of toxigenic C. difficile from stool plus the presence of clinically significant diarrhea compared to when the reference standard was having at least four assays positive while ignoring diarrhea severity. There were 15 patients whose assay result was reported as negative but subsequently found to be positive by at least four assays in the comparison. None suffered from any CDI-related adverse events. In conclusion, clinical presentation is important when interpreting C. difficile diagnostic assays.

Recent antibiotic exposure is associated with increased hospital mortality in Gram-negative bacteremia complicated by severe sepsis or septic shock. Clinicians caring for patients with severe sepsis or septic shock should consider recent antibiotic exposure when formulating empiric antimicrobial regimens for suspected Gram-negative bacterial infection.

The persistently elevated number of reported cases supports the need to understand the risk factors and environmental exposures associated with Acanthamoeba keratitis. Further prevention efforts are needed to reduce the number of cases occurring among contact lens wearers.

BACKGROUND:Gram‐negative bacteria are an important cause of severe sepsis. Recent studies have demonstrated reduced susceptibility of Gram‐negative bacteria to currently available antimicrobial agents.METHODS:We performed a retrospective cohort study of patients with severe sepsis who were bacteremic with Pseudomonas aeruginosa, Acinetobacter species, or Enterobacteriaceae from 2002 to 2007. Patients were identified by the hospital informatics database and pertinent clinical data (demographics, baseline severity of illness, source of bacteremia, and therapy) were retrieved from electronic medical records. All patients were treated with antimicrobial agents within 12 hours of having blood cultures drawn that were subsequently positive for bacterial pathogens. The primary outcome was hospital mortality.RESULTS:A total of 535 patients with severe sepsis and Gram‐negative bacteremia were identified. Hospital mortality was 43.6%, and 82 (15.3%) patients were treated with an antimicrobial regimen to which the causative pathogen was resistant. Patients infected with a resistant pathogen had significantly greater risk of hospital mortality (63.4% vs 40.0%; P < 0.001). In a multivariate analysis, infection with a pathogen that was resistant to the empiric antibiotic regimen, increasing APACHE II scores, infection with Pseudomonas aeruginosa, healthcare‐associated hospital‐onset infection, mechanical ventilation, and use of vasopressors were independently associated with hospital mortality.CONCLUSIONS:In severe sepsis attributed to Gram‐negative bacteremia, initial treatment with an antibiotic regimen to which the causative pathogen is resistant was associated with increased hospital mortality. This finding suggests that rapid determination of bacterial susceptibility could influence treatment choices in patients with severe sepsis potentially improving their clinical outcomes. Journal of Hospital Medicine 2011. © 2011 Society of Hospital Medicine

The recovery of bacteria and fungi from blood cultures was compared in conventional tryptic soy broth (TSB) bottles and in TSB bottles with an agarcoated slide attachment. A total of 2,662 sets of blood cultures, including 413 that were positive (15.5%), were evaluated. Significantly more gram-positive and gram-negative bacteria were recovered in the slide culture bottles than in conventional bottles (299 versus 253 isolates). Growth of gram-positive organisms and fungi was detected in the slide culture bottles 24 to 48 h earlier than in the TSB bottles. In addition, 76% of the isolates in the slide culture system were detected on the agar slide. In comparison, only 40% of the isolates in the TSB bottles were detected initially by blind subculturing. The incidences of contamination were 2.7% (71 cultures) for the slide culture system and 1.5% (39 cultures) for the TSB bottles.