Validation of Active Surveillance Testing for Clostridium difficile Colonization Using the cobas Cdiff Test.

Clostridium difficile infection (CDI) is not declining in the United States. Nucleic acid amplification tests (NAAT) are used as part of active surveillance testing programs to prevent health care-associated infection. The objective of this study was to validate the cobas Cdiff Test on the cobas 4800 System (cobas) within a four-hospital system using prospectively collected perirectal swabs from asymptomatic patients at admission and during monthly intensive care unit (ICU) screening in an infection control CDI reduction program. Performance of the cobas was compared to that of toxigenic culture. Each positive cobas sample and the next following negative patient swab were cultured. The study design gave 273 samples processed by both cobas (137 positive and 136 negative) and culture (one negative swab was not cultured). Discrepant analysis was performed using a second NAAT, the Xpert C. difficile Epi test (Xpert). This strategy was compared to a medical record review for antibiotic receipt that would inhibit growth of C. difficile in colonic stool. None of the cobas-negative samples were culture positive. The cobas positive predictive value was 75.2% (95% confidence interval [CI], 66.9% to 82%) and positive percent agreement was 100% (95% CI, 96.0% to 100%). Overall agreement between cobas and direct toxigenic culture was 87.6% (95% CI, 83.1% to 91%). For the cobas-positive/culture-negative (discrepant) samples, 7 Xpert-positive samples were from patients receiving inhibitory antimicrobials; only 4 of 23 Xpert-negative samples received these agents (P = 0.00006). Our results support use of the cobas as a reliable assay for an active surveillance testing program to detect asymptomatic carriers of toxigenic C. difficile.

Nonimpact of Decolonization as an Adjunctive Measure to Contact Precautions for the Control of Methicillin-Resistant Staphylococcus aureus Transmission in Acute Care.

This was an observational study comparing methicillin-resistant Staphylococcus aureus (MRSA) transmission with no decolonization of medical patients to required decolonization of all MRSA carriers during two consecutive periods: baseline with no decolonization of medical patients (16 months) and universal MRSA carrier decolonization (13 months). The setting was a one-hospital, 156-bed facility with 9,200 annual admissions. Regression models were used to compare rates of MRSA acquisition. The chi-square test was used to compare event frequencies. We used rates of MRSA clinical disease as an outcome monitor of the program. Analysis was done on 15,666 patients who had admission and discharge tests; 27.9% of inpatient days were occupied by a MRSA-positive patient (colonized patient-days) who received decolonization while hospitalized during the baseline period (this 27.9% represented those who had planned surgery) compared to 76.0% during the intervention period (P < 0.0001). The rate of MRSA transmission was 97 events (1.0%) for 9,415 admissions (2.0 transmission events/1,000 patient-days) during baseline and was 87 (1.4%) for 6,251 admissions (2.7 transmission events/1,000 patient-days) during intervention (P = 0.06; rate ratio, 0.74; 95% confidence interval [CI], 0.55 to 1.00). The MRSA nosocomial clinical disease rate was 5.9 infections/10,000 patient-days in the baseline period and was 7.2 infections/10,000 patient-days for the intervention period (rate ratio, 0.82; 95% CI, 0.46 to 1.45; P = 0.49). Decolonization of MRSA patients does not add benefit when contact precautions are used for patients colonized with MRSA in acute (hospital) care.

Methicillin-Resistant Staphylococcus aureus Control in the 21st Century: Laboratory Involvement Affecting Disease Impact and Economic Benefit from Large Population Studies.

Methicillin-resistant Staphylococcus aureus (MRSA) infection is a global health care problem. Large studies (e.g., >25,000 patients) show that active surveillance testing (AST) followed by contact precautions for positive patients is an effective approach for MRSA disease control. With this approach, the clinical laboratory will be asked to select what AST method(s) to use and to provide data monitoring outcomes of the infection prevention interventions. This minireview summarizes evidence for MRSA disease control, reviews the involvement of the laboratory, and provides examples of how to undertake a program cost analysis. Health care organizations with total MRSA clinical infections of >0.3/1,000 patient days or bloodstream infections of >0.03/1,000 patient days should implement a MRSA control plan.

Sensitivity of surveillance testing for multidrug-resistant Gram-negative bacteria in the intensive care unit.

We tested intensive care unit patients for colonization with multidrug-resistant Gram-negative bacilli (MDR GNB) and compared the results with those of concurrent clinical cultures. The sensitivity of the surveillance test for detecting MDR GNB was 58.8% (95% confidence interval, 48.6 to 68.5%). Among 133 patients with positive surveillance tests, 61% had no prior clinical culture with MDR GNB.

Nasal Carriage of Epidemic Methicillin-Resistant Staphylococcus aureus 15 (EMRSA-15) Clone Observed in Three Chicago-Area Long-Term Care Facilities.

The spread of pandemic methicillin-resistant Staphylococcus aureus (MRSA) clones such as USA300 and EMRSA-15 is a global health concern. As a part of a surveillance study of three long-term care facilities in the Greater Chicago area, phenotypic and molecular characterization of nasal MRSA isolates was performed. We report a cluster of pandemic EMRSA-15, an MRSA clone rarely reported from the United States, detected during this study.

Multiple broad-spectrum Beta-lactamase targets for comprehensive surveillance.

Real-time PCR testing for blaKPC, blaNDM, blaVIM, blaIMP, and blaCTX-M was performed on rectal swabs obtained from residents of two long-term acute-care facilities. While blaKPC was detected in 69/102 swabs (67.6%), testing for four other targets increased the positivity rate for a broad-spectrum ß-lactamase to 73.5% (McNemar's P = 0.03).

Rectal screening for Klebsiella pneumoniae carbapenemases: comparison of real-time PCR and culture using two selective screening agar plates.

Klebsiella pneumoniae carbapenemases (KPCs) have recently been described in Chicago, IL, especially among residents of long-term acute care hospitals (LTACHs). These patients are frequently transferred to local Chicago hospitals for higher acuity of medical care, and rapid detection and isolation of KPC-colonized LTACH residents may interrupt the introduction of KPCs into acute care hospitals. We evaluated the performance of a real-time PCR for bla(KPC) from enrichment broth versus direct plating of rectal surveillance swabs on two selective culture media, CHROMagar extended-spectrum-ß-lactamase (ESBL) and vancomycin, amphotericin B, ceftazidime, and clindamycin (VACC) plates. Rectal surveillance swabs were collected as part of a point prevalence study of KPC carriage rates among 95 residents of two Chicago area LTACHs. Discrepant results between PCR and culture were resolved by subculturing the enrichment broth. Overall, 66 of 95 patients (69.5%) were colonized with KPCs, using the cumulative results of culture as a reference standard. Real-time PCR from enrichment broth was positive in 64 of 66 (97%) colonized patients, including nine surveillance swabs that were missed by both selective culture media. PCR demonstrated higher sensitivity, 97.0%, than culture using either CHROMagar or VACC plates (both with sensitivity of 77.3%). In addition, turnaround time was significantly shorter for the PCR-based method than for culture, with a mean of 24 h versus 64 to 72 h for CHROMagar and VACC plates (P < 0.0001). Overall, PCR for bla(KPC) represents the best screening test for KPCs with significantly higher sensitivity and with less hands-on time, resulting in a shorter time to results.

Cytoskeletal Tropomyosin as a Biomarker in Clostridium difficile Infection.

BACKGROUND: Current diagnostics of Clostridium difficile infection (CDI) heavily relies on detection of the disease-causing organism. The objective of this study was to investigate a cytoskeletal protein, tropomyosin (Tpm), as a CDI biomarker. METHODS: Fecal Tpm was tested by monoclonal antibodies (mAbs) in a 12-month prospective study. Remnant diarrheal clinical specimens and relevant clinical data were collected. The CDI positive (CDI+, n = 230) and CDI negative (CDI-, n = 228) groups were composed of samples testing positive or negative by polymerase chain reaction (PCR) (Xpert® C. difficile/Epi, Cepheid), respectively. The other enteric pathogen (OEP) group (n = 52) was composed of specimens tested for the presence of other enteric pathogens or parasites by routine testing methods. Extracted fecal Tpm was detected by Western blot and the results were correlated with CDI based on clinical and microbiology laboratory data. RESULTS: A total of 510 stool specimens were tested. Tpm is not stable in stool, suggesting the utility of fresh specimens. In the CDI+ group, specificity and sensitivity of Tpm detection in correlation with a CDI were 93.2% and 53.7%, respectively, when only "true CDI" and "not CDI" were analyzed (110 samples). For CDI+ samples, 23% did not satisfy CDI clinical signs. Tpm positives in the CDI- group (8.3%) had inflammatory bowel diseases. CONCLUSION: Tpm has a potential role as a CDI biomarker in combination with C. difficile PCR and an appropriate clinical evaluation. However, non-muscle Tpm, as a biomarker for CDI, suffers from a low sensitivity in our study. Therefore further investigation using larger cohorts is needed.

Immunological Stability of Clostridium difficile Toxins in Clinical Specimens.

OBJECTIVE The impact of storage on stability and detection of Clostridium difficile toxins in feces is poorly understood. The objective of this study was to investigate the immunological stability of C. difficile toxins in clinical stool specimens under different storage conditions by evaluating this stability using toxin detection by enzyme immunoassay (EIA). METHODS Stool specimens positive for C. difficile infection (CDI) by quantitative polymerase chain reaction (qPCR) were used for EIA testing with the C. difficile Tox A/B II kit. The EIA-positive specimens were stored aerobically under refrigerated (4-10°C) and frozen (-30°C and -80°C) conditions. Measurement of toxin quantity was conducting using optical density (OD) on days 0, 14, 30, 60, 90, and 120 of storage. RESULTS Clostridium difficile toxins demonstrated good detection in undiluted stool specimens by EIA up to 120 days of storage. Good detection of the toxins was observed in diluted samples at refrigerated and -80°C temperatures. Dilution detrimentally affected toxin detection at -30°C. CONCLUSION Storage of undiluted clinical stool specimens at refrigerated, -30°C, and -80°C temperatures for up to 120 days has no discernible effect on the immunological stability of C. difficile cytotoxins. However, storage at -30°C has a detrimental effect on C. difficile toxin stability in diluted specimens. Infect Control Hosp Epidemiol 2018;39:434-438.

Reduction of methicillin-resistant Staphylococcus aureus infection in long-term care is possible while maintaining patient socialization: A prospective randomized clinical trial.

BACKGROUND: Antibiotic resistance is a challenge in long-term care facilities (LTCFs). The objective of this study was to demonstrate that a novel, minimally invasive program not interfering with activities of daily living or socialization could lower methicillin-resistant Staphylococcus aureus (MRSA) disease. METHODS: This was a prospective, cluster-randomized, nonblinded trial initiated at 3 LTCFs. During year 1, units were stratified by type of care and randomized to intervention or control. In year 2, all units were converted to intervention consisting of universal decolonization using intranasal mupirocin and a chlorhexidine bath performed twice (2 decolonization-bathing cycles 1 month apart) at the start of the intervention period. Subsequently, after initial decolonization, all admissions were screened on site using real-time polymerase chain reaction, and those MRSA positive were decolonized, but not isolated. Units received annual instruction on hand hygiene. Enhanced bleach wipe cleaning of flat surfaces was done every 4 months. RESULTS: There were 16,773 tests performed. The MRSA infection rate decreased 65% between baseline (44 infections during 365,809 patient days) and year 2 (12 infections during 287,847 patient days; P <.001); a significant reduction was observed at each of the LTCFs (P <.03). CONCLUSIONS: On-site MRSA surveillance with targeted decolonization resulted in a significant decrease in clinical MRSA infection among LTCF residents.

Evaluation of multiple real-time PCR tests on nasal samples in a large MRSA surveillance program.

OBJECTIVES: We evaluated the LightCycler MRSA Advanced Test (Roche Molecular Diagnostics, Pleasanton, CA), the BD MAX MRSA assay (Becton Dickinson, Franklin Lakes, NJ), and the Xpert MRSA assay (Cepheid, Sunnyvale, CA) on nasal samples using the same population. METHODS: Admission and discharge nasal swabs were collected from inpatients using a double-headed swab. One swab was plated onto CHROMagar MRSA (CMA; Becton Dickinson, Sparks, MD) and then broken off into tryptic soy broth (TSB) for enrichment. TSB was incubated for 24 hours and then plated to CMA. The molecular tests were performed on the second swab. We analyzed the cost benefit of testing to evaluate what parameters affect hospital resources. RESULTS: A total of 27,647 specimens were enrolled. The sensitivity/specificity was 98.3%/98.9% for the LightCycler MRSA Advanced Test and 95.7%/98.8% for the Xpert MRSA assay, but the difference was not significant. The positive predictive value was 86.7% for the LightCycler MRSA Advanced Test, 82.7% for the Xpert MRSA assay (P > .1), and 72.2% and for the BD MAX MRSA test (P < .001 compared with the LightCycler MRSA Advanced Test). All three assays were cost-effective, with the LightCycler MRSA Advanced Test having the highest economic return. CONCLUSIONS: Our results suggest that the performance of the three commercial assays is similar. When assessing economic cost benefit of methicillin-resistant Staphylococcus aureus screening, the two measures with the most impact are the cost of the test and the specificity of the assay results.

Performance of the Cepheid Xpert® SA Nasal Complete PCR assay compared to culture for detection of methicillin-sensitive and methicillin-resistant Staphylococcus aureus colonization.

Sensitivity, specificity, positive predictive value, and negative predictive value for the Cepheid Xpert® SA Nasal Complete detection (N = 971) of methicillin-sensitive Staphylococcus aureus was 86.5%, 98.5%, 94.6%, and 96.1%; detection of methicillin-resistant S. aureus was 89.3%, 97.9%, 79.8%, and 99.0%, respectively. Our results show that testing on long-term care facility patients had lower sensitivity and specificity compared to acute care patient results.

Impact of Detection, Education, Research and Decolonization without Isolation in Long-term care (DERAIL) on methicillin-resistant Staphylococcus aureus colonization and transmission at 3 long-term care facilities.

We tested infection prevention strategies to limit exposure of long-term care facility residents to drug-resistant pathogens in a prospective, cluster randomized 2-year trial involving 3 long-term care facilities (LTCFs) using methicillin-resistant Staphylococcus aureus (MRSA) as a model. We hypothesized that nasal MRSA surveillance using rapid quantitative polymerase chain reaction and decolonization of carriers would successfully lower overall MRSA colonization. In year 1, randomly assigned intervention units received decolonization with nasal mupirocin and chlorhexidine bathing and enhanced environmental cleaning with bleach every 4 months. Newly admitted MRSA nares-positive residents were decolonized on admission. Control units were screened but not decolonized. All units received periodic bleach environmental cleaning and instruction on hand hygiene. In year 2, all units followed intervention protocol caused by failure of the cluster randomized approach to sufficiently segregate patients. MRSA colonization was monitored using point prevalence testing every 4-6 months. Colonization status at admission and discharge was performed 1 quarter per year to determine acquisition. Fisher exact test was used for statistical analysis. Baseline MRSA colonization rate was 16.64%. In year 1, the colonization rate of intervention units was 11.61% (P = .028) and 17.85% in control units (P = .613) compared with baseline. Intervention unit rate difference compared with the controls was significant (P = .001). In year 2, the colonization rate was 10.55% (P < .001) compared with baseline. The transmission rates were 1.66% and 3.52% in years 1 and 2, respectively (P = .034). The planned interventions of screening and decolonization were successful at lowering MRSA colonization.

Continuous passive disinfection of catheter hubs prevents contamination and bloodstream infection.

BACKGROUND: Catheter hub decontamination requires a thorough scrub and compliance varies. This study evaluates the effectiveness of a disinfection cap with 70% alcohol in preventing contamination/infection. METHODS: A 3-phased, multifacility, quasi-experimental study of adult patients with central lines divided into P1 (baseline), when the standard scrub was used; P2, when the cap was used on all central lines; and P3, when standard disinfection was reinstituted. House-wide central-line associated bloodstream infection (CLABSI) rates are reported with catheter-associated urinary tract infections (CAUTI) as a control measure. Adults with peripherally inserted central catheters inserted during hospitalization having 5+ consecutive line-days gave consent and were enrolled, and 1.5 mL of blood was withdrawn from each lumen not in use and quantitatively cultured. RESULTS: Contamination was 12.7% (32/252) during P1; 5.5% (20/364) in P2 (P = .002), and 12.0% (22/183; P = 0.88 vs P1 and P = .01 vs P2) in P3 (P = .001 vs P2). The median colony-forming units per milliliter was 4 for P1, 1 for P2 (P = .009), and 2 for P3 (P = .05 vs P2). CLABSI rates declined from 1.43 per 1,000 line-days (16/11,154) to 0.69 (13/18,972) in P2 (P = .04) and increased to 1.31 (7/5,354) in P3. CAUTI rates remained stable between P1 and P2 (1.42 and 1.41, respectively, P = .90) but declined in P3 (1.04, P = .03 vs P1 and P2). CONCLUSION: Disinfecting caps reduce line contamination, organism density, and CLABSIs.

Predictors and molecular epidemiology of community-onset extended-spectrum ß-lactamase-producing Escherichia coli infection in a Midwestern community.

OBJECTIVE: To identify predictors of community-onset extended-spectrum ß-lactamase (ESBL)-producing Escherichia coli infection. DESIGN: Prospective case-control study. SETTING: Acute care hospitals and ambulatory clinics in the Chicago, Illinois, region. PATIENTS: Adults with E. coli clinical isolates cultured in ambulatory settings or within 48 hours of hospital admission. METHODS: Cases were patients with ESBL-producing E. coli clinical isolates cultured in ambulatory settings or within 48 hours of admission, and controls were patients with non-ESBL-producing E. coli isolates, matched to cases by specimen, location, and date. Clinical variables were ascertained through interviews and medical record review. Molecular methods were used to identify ESBL types, sequence type ST131, and aac(6')-Ib-cr. RESULTS: We enrolled 94 cases and 158 controls. Multivariate risk factors for ESBL-producing E. coli infection included travel to India in the past year (odds ratio [OR], 14.40 [95% confidence interval (CI), 2.92-70.95]), ciprofloxacin use (OR, 3.92 [95% CI, 1.90-8.1]), and age (OR, 1.04 [95% CI, 1.02-1.06]). Case isolates exhibited high prevalence of CTX-M-15 (78%), ST131 (50%), and aac(6')-Ib-cr (66% of isolates with CTX-M-15). CONCLUSIONS: Providers should be aware of the increased risk of ESBL-producing E. coli infection among returned travelers, especially those from India.