Characteristics and Antibiotic Use Associated With Short-Term Risk of Clostridium difficile Infection Among Hospitalized Patients.

OBJECTIVES: Polymerase chain reaction (PCR) has been shown to have an excellent sensitivity and specificity for the detection of Clostridium difficile infection (CDI). Little is known about risk factors for CDI within 14 days of an initial negative test. We sought to determine the characteristics among hospitalized patients associated with risk of short-term acquisition of CDI. METHODS: A case-control study was conducted. Cases were patients who converted from PCR negative to positive within 14 days. Each case was matched with three controls. Conditional logistic regression was used to estimate the association between patient characteristics and CDI. RESULTS: Of the 30 patients in our study who had a positive PCR within 14 days of a first negative PCR (cases), 15 (50%) occurred within 7 days of the initial test. Cases had a higher proportion of intravenous vancomycin use in the previous 8 weeks (odds ratio [OR], 3.38; 95% confidence interval [CI], 1.34-8.49) and were less likely to have recent antiviral agent use (OR, 0.30; 95% CI, 0.11-0.83) compared with controls. CONCLUSIONS: In hospitalized patients, treatment with intravenous vancomycin within the prior 8 weeks of a first negative PCR test for C difficile is a risk factor for short-term risk for hospital-acquired CDI. Repeat testing guidelines for C difficile PCR should take into consideration patients who may be at high risk for short-term acquisition of CDI.

Detection of respiratory viruses with a multiplex polymerase chain reaction assay (MultiCode-PLx Respiratory Virus Panel) in patients with hematologic malignancies.

Respiratory viral pathogens are a common cause of morbidity in patients with hematologic malignancies. Sensitive molecular assays have increased the detection of common respiratory viruses and expanded the panel of detectable viruses. Both a rapid viral culture with direct fluorescence antibody (DFA) staining and a PCR-based assay (MultiCode-PLx Respiratory Virus Panel) were performed on patients with hematologic malignancies, who underwent collection of a nasopharyngeal swab or bronchoalveolar lavage from October 2006 to April 2007. Eighty-two samples from 70 patients were obtained; all patients had upper respiratory tract symptoms. Respiratory viruses were detected in 10 samples (12%) by conventional virological methods and in 31 samples (38%) by the MultiCode-PLx assay. This increased diagnostic yield resulted from better sensitivity for those viruses detectable by both methods and detection of viruses not covered by the antigen detection/rapid culture method (human metapneumovirus, coronaviruses and rhinoviruses). The MultiCode-PLx assay frequently identified respiratory viral infections which are not detected by rapid viral culture/DFA; 40% of these patients had pneumonia in addition to the upper respiratory tract symptoms. Improved diagnostics for respiratory viruses may lead to more effective management and better outcomes in this patient population.

MultiCode-PLx system for multiplexed detection of seventeen respiratory viruses.

The MultiCode-PLx system (EraGen Biosciences, Inc., Madison, WI) for the detection of respiratory viruses uses an expanded genetic alphabet, multiplex PCR chemistry, and microsphere flow cytometry to rapidly detect and specifically identify 17 different respiratory viruses directly in clinical specimens. The MultiCode-PLx system was tested in parallel with direct fluorescent-antibody (DFA) staining and rapid shell vial culture (R-mix cells; Diagnostic Hybrids, Inc. Athens, OH) with 354 respiratory specimens from adult patients that were submitted to the clinical virology laboratory at the Emory University Hospital. Single-target PCRs were performed with retained samples to confirm the positive results obtained with the MultiCode-PLx system for viruses not covered by DFA and R-mix culture (metapneumovirus, coronaviruses [CoV], parainfluenza viruses 4a and 4b, and rhinoviruses) and to resolve any discrepancies between the DFA and R-mix culture and the MultiCode-PLx results for viruses common to both systems. Respiratory viruses were detected in 77 (21.8%) and 116 (32.7%) specimens by DFA and R-mix culture and with the MultiCode-PLx system, respectively. Among the viruses common to both systems, the MultiCode-PLx system detected significantly more influenza A viruses (P = 0.0026). An additional increased diagnostic yield with the MultiCode-PLx system resulted from the detection of human metapneumovirus (HMPV) in 9 specimens, human CoV (HCoV) in 3 specimens, and human rhinovirus (HRV) in 16 specimens. Also, two mixed viral infections were detected by the MultiCode-PLx system (HCoV OC43 and HRV infections and HMPV and HRV infections), but none were detected by DFA and R-mix culture. Single-target PCRs verified the results obtained with the MultiCode-PLx system for 73 of 81 (90.1%) specimens that had discordant results or that were not covered by DFA and R-mix culture. The MultiCode-PLx system provides clinical laboratories with a practical, rapid, and sensitive means for the massively multiplexed molecular detection of common respiratory viruses.