PloS one 2013
Authors: Ridgway JP, Peterson LR, Brown EC, Du H, Hebert C, Thomson RB,
Methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization among inpatients is a well-established risk factor for MRSA infection during the same hospitalization, but the long-term risk of MRSA infection is uncertain. We performed a retrospective cohort study to determine the one-year risk of MRSA infection among inpatients with MRSA-positive nasal polymerase chain reaction (PCR) tests confirmed by positive nasal culture (Group 1), patients with positive nasal PCR but negative nasal culture (Group 2), and patients with negative nasal PCR (Group 3).
Subjects were adults admitted to a four-hospital system between November 1, 2006 and March 31, 2011, comprising 195,255 admissions. Patients underwent nasal swab for MRSA PCR upon admission; if positive, nasal culture for MRSA was performed; if recovered, MRSA was tested for Panton-Valentine Leukocidin (PVL). Outcomes included MRSA-positive clinical culture and skin and soft tissue infection (SSTI). Group 1 patients had a one-year risk of MRSA-positive clinical culture of 8.0% compared with 3.0% for Group 2 patients, and 0.6% for Group 3 patients (p<0.001). In a multivariable model, the hazard ratios for future MRSA-positive clinical culture were 6.52 (95% CI, 5.57 to 7.64) for Group 1 and 3.40 (95% CI, 2.70 to 4.27) for Group 2, compared with Group 3 (p<0.0001). History of MRSA and concurrent MRSA-positive clinical culture were significant risk factors for future MRSA-positive clinical culture. Group 1 patients colonized with PVL-positive MRSA had a one-year risk of MRSA-positive clinical culture of 10.1%, and a one-year risk of MRSA-positive clinical culture or SSTI diagnosis of 21.7%, compared with risks of 7.1% and 12.5%, respectively, for patients colonized with PVL-negative MRSA (p = 0.04, p = 0.005, respectively).
MRSA nasal colonization is a significant risk factor for future MRSA infection; more so if detected by culture than PCR. Colonization with PVL-positive MRSA is associated with greater risk than PVL-negative MRSA.
PMID: 24278161 [PubMed - as supplied by publisher]
Antimicrobial agents and chemotherapy 2013 Dec
Authors: Banerjee R, Robicsek A, Kuskowski MA, Porter S, Johnston BD, Sokurenko E, Tchesnokova V, Price LB, Johnson JR,
We assessed Escherichia coli ST131 and its H30 and H30-Rx subclones for virulence genes, antimicrobial resistance, and extended-spectrum beta-lactamase (ESBL) type. Although both subclones were associated with ESBL production, H30-Rx isolates had higher resistance scores and were associated specifically with CTX-M-15. Three virulence genes (iha, sat, and iutA) were more prevalent among H30 than non-H30 ST131 isolates. Thus, the H30 and H30-Rx subclones are more antimicrobial resistant and have virulence profiles that are distinct from those of non-H30 ST131 isolates.
PMID: 24080662 [PubMed - as supplied by publisher]
CMAJ : Canadian Medical Association journal = journal de l'Association medicale canadienne 2013 Oct 15
Authors: MacFadden DR, Elligsen M, Robicsek A, Ricciuto DR, Daneman N,
Screening for methicillin-resistant Staphylococcus aureus (MRSA) is intended to reduce nosocomial spread by identifying patients colonized by MRSA. Given the widespread use of this screening, we evaluated its potential clinical utility in predicting the resistance of clinical isolates of S. aureus.
We conducted a 2-year retrospective cohort study that included patients with documented clinical infection with S. aureus and prior screening for MRSA. We determined test characteristics, including sensitivity and specificity, of screening for predicting the resistance of subsequent S. aureus isolates.
Of 510 patients included in the study, 53 (10%) had positive results from MRSA screening, and 79 (15%) of infecting isolates were resistant to methicillin. Screening for MRSA predicted methicillin resistance of the infecting isolate with 99% (95% confidence interval [CI] 98%-100%) specificity and 63% (95% CI 52%-74%) sensitivity. When screening swabs were obtained within 48 hours before isolate collection, sensitivity increased to 91% (95% CI 71%-99%) and specificity was 100% (95% CI 97%-100%), yielding a negative likelihood ratio of 0.09 (95% CI 0.01-0.3) and a negative predictive value of 98% (95% CI 95%-100%). The time between swab and isolate collection was a significant predictor of concordance of methicillin resistance in swabs and isolates (odds ratio 6.6, 95% CI 1.6-28.2).
A positive result from MRSA screening predicted methicillin resistance in a culture-positive clinical infection with S. aureus. Negative results on MRSA screening were most useful for excluding methicillin resistance of a subsequent infection with S. aureus when the screening swab was obtained within 48 hours before collection of the clinical isolate.
PMID: 24016794 [PubMed - as supplied by publisher]
Infection control and hospital epidemiology : the official journal of the Society of Hospital Epidemiologists of America 2013 Sep
Authors: Banerjee R, Strahilevitz J, Johnson JR, Nagwekar PP, Schora DM, Shevrin I, Du H, Peterson LR, Robicsek A,
To identify predictors of community-onset extended-spectrum β-lactamase (ESBL)-producing Escherichia coli infection.
Prospective case-control study.
Acute care hospitals and ambulatory clinics in the Chicago, Illinois, region.
Adults with E. coli clinical isolates cultured in ambulatory settings or within 48 hours of hospital admission.
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.
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).
Providers should be aware of the increased risk of ESBL-producing E. coli infection among returned travelers, especially those from India.
PMID: 23917909 [PubMed - as supplied by publisher]
Infection control and hospital epidemiology : the official journal of the Society of Hospital Epidemiologists of America 2013 Apr
Authors: Hebert C, Du H, Peterson LR, Robicsek A,
A major challenge in treating Clostridium difficile infection (CDI) is relapse. Many new therapies are being developed to help prevent this outcome. We sought to establish risk factors for relapse and determine whether fields available in an electronic health record (EHR) could be used to identify high-risk patients for targeted relapse prevention strategies.
Retrospective cohort study.
Large clinical data warehouse at a 4-hospital healthcare organization.
Data were gathered from January 2006 through October 2010. Subjects were all inpatient episodes of a positive C. difficile test where patients were available for 56 days of follow-up.
Relapse was defined as another positive test between 15 and 56 days after the initial test. Multivariable regression was performed to identify factors independently associated with CDI relapse.
Eight hundred twenty-nine episodes met eligibility criteria, and 198 resulted in relapse (23.9%). In the final multivariable analysis, risk of relapse was associated with age (odds ratio [OR], 1.02 per year [95% confidence interval (CI), 1.01-1.03]), fluoroquinolone exposure in the 90 days before diagnosis (OR, 1.58 [95% CI, 1.11-2.26]), intensive care unit stay in the 30 days before diagnosis (OR, 0.47 [95% CI, 0.30-0.75]), cephalosporin (OR, 1.80 [95% CI, 1.19-2.71]), proton pump inhibitor (PPI; OR, 1.55 [95% CI, 1.05-2.29]), and metronidazole exposure after diagnosis (OR, 2.74 [95% CI, 1.64-4.60]). A prediction model tuned to ensure a 50% probability of relapse would flag 14.6% of CDI episodes.
Data from a comprehensive EHR can be used to identify patients at high risk for CDI relapse. Major risk factors include antibiotic and PPI exposure.
PMID: 23466915 [PubMed - as supplied by publisher]
The Journal of infectious diseases 2013 Mar 15
Authors: Johnson JR, Tchesnokova V, Johnston B, Clabots C, Roberts PL, Billig M, Riddell K, Rogers P, Qin X, Butler-Wu S, Price LB, Aziz M, Nicolas-Chanoine MH, Debroy C, Robicsek A, Hansen G, Urban C, Platell J, Trott DJ, Zhanel G, Weissman SJ, Cookson BT, Fang FC, Limaye AP, Scholes D, Chattopadhyay S, Hooper DC, Sokurenko EV,
Fluoroquinolone-resistant Escherichia coli are increasingly prevalent. Their clonal origins--potentially critical for control efforts--remain undefined.
Antimicrobial resistance profiles and fine clonal structure were determined for 236 diverse-source historical (1967-2009) E. coli isolates representing sequence type ST131 and 853 recent (2010-2011) consecutive E. coli isolates from 5 clinical laboratories in Seattle, Washington, and Minneapolis, Minnesota. Clonal structure was resolved based on fimH sequence (fimbrial adhesin gene: H subclone assignments), multilocus sequence typing, gyrA and parC sequence (fluoroquinolone resistance-determining loci), and pulsed-field gel electrophoresis.
Of the recent fluoroquinolone-resistant clinical isolates, 52% represented a single ST131 subclonal lineage, H30, which expanded abruptly after 2000. This subclone had a unique and conserved gyrA/parC allele combination, supporting its tight clonality. Unlike other ST131 subclones, H30 was significantly associated with fluoroquinolone resistance and was the most prevalent subclone among current E. coli clinical isolates, overall (10.4%) and within every resistance category (11%-52%).
Most current fluoroquinolone-resistant E. coli clinical isolates, and the largest share of multidrug-resistant isolates, represent a highly clonal subgroup that likely originated from a single rapidly expanded and disseminated ST131 strain. Focused attention to this strain will be required to control the fluoroquinolone and multidrug-resistant E. coli epidemic.
PMID: 23288927 [PubMed - as supplied by publisher]
Surgical infections 2012 Dec
Authors: Huttner B, Robicsek AA, Gervaz P, Perencevich EN, Schiffer E, Schrenzel J, Harbarth S,
Surgical site infections (SSIs) after colorectal surgery usually are caused by commensal intestinal bacteria. Methicillin-resistant Staphylococcus aureus (MRSA) may be responsible for additional SSI-related morbidity. The aim of this retrospective cohort study was to describe the epidemiology of SSIs caused by MRSA after colorectal surgery in two tertiary-care centers, one in Geneva, Switzerland (G), and the other in Chicago, Illinois (C).
Adult patients undergoing colorectal resections during periods of universal screening for MRSA on admission were identified retrospectively. Demographic characteristics, surgery-related factors, and occurrence of MRSA SSI were compared in patients with and without MRSA carriage before surgery.
There were 1,069 patients (G=194, C=875) with a median age of 67 years fulfilling the inclusion criteria. Of these, 45 patients (4.2%) had a positive MRSA screening result within 30 days before surgery (G=18, C=27; p<0.001). Ten patients (0.9%; G=6, C=4) developed MRSA SSI, detected a median of 17.5 days after surgery, but only two of them were MRSA-positive before surgery. Nine of the 45 MRSA carriers identified by screening received pre-operative prophylaxis with vancomycin (G 6/18, C 3/27), and 17 of these patients (37.8%; G 7/18, C 10/27) were started on MRSA decolonization therapy before surgery. Pre-operative administration of either decolonization or vancomycin was not protective against MRSA SSI (p=0.49).
Methicillin-resistant S. aureus seems to be an infrequent cause of SSI after colorectal resections, even in MRSA carriers. Systematic universal screening for MRSA carriage prior to colorectal surgery may not be beneficial for the individual patient. Post-operative factors seem to be important in MRSA infections, as the majority of MRSA SSIs occurred in patients negative for MRSA carriage.
PMID: 23240722 [PubMed - as supplied by publisher]
American journal of infection control 2013 Jan
Authors: Wright MO, Tropp J, Schora DM, Dillon-Grant M, Peterson K, Boehm S, Robicsek A, Peterson LR,
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.
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.
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).
Disinfecting caps reduce line contamination, organism density, and CLABSIs.
PMID: 23084024 [PubMed - as supplied by publisher]
Critical care medicine 2012 Dec
Authors: Klompas M, Magill S, Robicsek A, Strymish JM, Kleinman K, Evans RS, Lloyd JF, Khan Y, Yokoe DS, Stevenson K, Samore M, Platt R, CDC Prevention Epicenters Program,
The subjectivity and complexity of surveillance definitions for ventilator-associated pneumonia preclude meaningful internal or external benchmarking and therefore hamper quality improvement initiatives for ventilated patients. We explored the feasibility of creating objective surveillance definitions for ventilator-associated pneumonia.
We identified clinical signs suitable for inclusion in objective definitions, proposed candidate definitions incorporating these objective signs, and then applied these definitions to retrospective clinical data to measure their frequencies and associations with adverse outcomes using multivariate regression models for cases and matched controls.
Medical and surgical intensive care units in eight U.S. hospitals (four tertiary centers, three community hospitals, and one Veterans Affairs institution).
Eight thousand seven hundred thirty-five consecutive episodes of mechanical ventilation for adult patients.
We evaluated 32 different candidate definitions composed of different combinations of the following signs: three thresholds for respiratory deterioration defined by sustained increases in daily minimum positive end-expiratory pressure or FIO2 after either 2 or 3 days of stable or decreasing ventilator settings, abnormal temperature, abnormal white blood cell count, purulent pulmonary secretions defined by neutrophils on Gram stain, and positive cultures for pathogenic organisms.
Ventilator-associated pneumonia incidence, attributable ventilator days, hospital days, and hospital mortality. All candidate definitions were significantly associated with increased ventilator days and hospital days, but only definitions requiring objective evidence of respiratory deterioration were significantly associated with increased hospital mortality. Significant odds ratios for hospital mortality ranged from 1.9 (95% confidence interval 1.2-2.9) to 6.1 (95% confidence interval 2.2-17). Requiring additional clinical signs beyond respiratory deterioration alone decreased event rates, had little impact on attributable lengths of stay, and diminished sensitivity and positive predictive values for hospital mortality.
Objective surveillance definitions that include quantitative evidence of respiratory deterioration after a period of stability strongly predict increased length of stay and hospital mortality. These definitions merit further evaluation of their utility for hospital quality and safety improvement programs.
PMID: 22990454 [PubMed - as supplied by publisher]
Annals of internal medicine 2012 Aug 7
Authors: Hebert C, Beaumont J, Schwartz G, Robicsek A,
Little is known about the influence of contextual factors on a physician's likelihood to prescribe antimicrobials for febrile respiratory illness (FRI). Context includes epidemiologic context (for example, a pandemic period) and personal context (for example, recent exposure to other patients with FRI).
To examine the association between contextual factors and antimicrobial prescribing for FRI.
5.5-year retrospective cohort study.
A network of Midwestern primary care providers.
All patients presenting with FRI during influenza seasons between 2006 and 2011.
Antimicrobial prescribing for FRI during pandemic and seasonal influenza periods.
28 301 unique patient encounters for FRI with 69 physicians in 26 practices were included. An antibiotic was prescribed in 12 795 (45.2%) cases. The range of prescribing among physicians was 17.9% to 83.7%. Antibiotics were prescribed in 47.5% of encounters during the seasonal period and 39.2% during the pandemic period (P < 0.001). After multivariable adjustment for patient and physician characteristics, antibiotic prescribing was lower in the pandemic period (odds ratio [OR], 0.72 [95% CI, 0.68 to 0.77]) than in the seasonal period. The likelihood of prescribing an antibiotic decreased as the number of FRI cases that a physician had seen in the previous week increased (OR, 0.93 [CI, 0.86 to 1.01] for 2 to 3 patients with FRI seen in the previous week; OR, 0.84 [CI, 0.77 to 0.91] for 4 to 6 patients; OR, 0.71 [CI, 0.64 to 0.78] for 7 to 11 patients; and OR, 0.57 [CI, 0.51 to 0.63] for ≥12 patients compared with the reference range of 0 to 1 patients). Pandemic season and recent personal context were also associated with antiviral prescribing.
Retrospective study in a single geographic area.
Epidemiologic context and the number of cases of FRI that a physician had recently seen were associated with his or her likelihood to prescribe antimicrobials for FRI. Interventions that enhance a physician's contextual awareness may improve antimicrobial use.
NorthShore University HealthSystem.
PMID: 22868833 [PubMed - as supplied by publisher]