Staphylococcus aureus is a common cause of healthcare-associated infections in neonates.

To examine the impact of methicillin-susceptible S. aureus (MSSA) decolonization on the incidence of MSSA infection and to measure the prevalence of mupirocin resistance.

We retrospectively identified neonates admitted to a tertiary care neonatal intensive care unit (NICU) from April 1, 2011, through September 30, 2014. We compared rates of MSSA-positive cultures and infections before and after implementation of an active surveillance culture and decolonization intervention for MSSA-colonized neonates. We used 2 measurements to identify the primary outcome, NICU-attributable MSSA: (1) any culture sent during routine clinical care that grew MSSA and (2) any culture that grew MSSA and met criteria of the National Healthcare Safety Network’s healthcare-associated infection surveillance definitions. S. aureus isolates were tested for mupirocin susceptibility. We estimated incidence rate ratios using interrupted time-series models.

Before and after the intervention, 1,523 neonates (29,220 patient-days) and 1,195 neonates (22,045 patient-days) were admitted to the NICU, respectively. There was an immediate reduction in the mean quarterly incidence rate of NICU-attributable MSSA-positive clinical cultures of 64% (incidence rate ratio, 0.36 [95% CI, 0.19–0.70]) after implementation of the intervention, and MSSA-positive culture rates continued to decrease by 21% per quarter (incidence rate ratio, 0.79 [95% CI, 0.74–0.84]). MSSA infections also decreased by 73% immediately following the intervention implementation (incidence rate ratio, 0.27 [95% CI, 0.10–0.79]). No mupirocin resistance was detected.

Active surveillance cultures and decolonization may be effective in decreasing S. aureus infections in NICUs.

Infect. Control Hosp. Epidemiol. 2016;37(4):381–387

Bloodstream infection (BSI) due to methicillin-resistant Staphylococcus aureus (MRSA) is associated with considerable morbidity and mortality.

To determine the incidence of MRSA BSI in Canadian hospitals and to identify variables associated with increased mortality.

Prospective surveillance for MRSA BSI conducted in 53 Canadian hospitals from January 1, 2008, through December 31, 2012. Thirty-day all-cause mortality was determined, and logistic regression analysis was used to identify variables associated with mortality.

A total of 1,753 patients with MRSA BSI were identified (incidence, 0.45 per 1,000 admissions). The most common sites presumed to be the source of infection were skin/soft tissue (26.6%) and an intravascular catheter (22.0%). The most common spa types causing MRSA BSI were t002 (USA100/800; 55%) and t008 (USA300; 29%). Thirty-day all-cause mortality was 23.8%. Mortality was associated with increasing age (odds ratio, 1.03 per year [95% CI, 1.02–1.04]), the presence of pleuropulmonary infection (2.3 [1.4–3.7]), transfer to an intensive care unit (3.2 [2.1–5.0]), and failure to receive appropriate antimicrobial therapy within 24 hours of MRSA identification (3.2 [2.1–5.0]); a skin/soft-tissue source of BSI was associated with decreased mortality (0.5 [0.3–0.9]). MRSA genotype and reduced susceptibility to vancomycin were not associated with risk of death.

This study provides additional insight into the relative impact of various host and microbial factors associated with mortality in patients with MRSA BSI. The results emphasize the importance of ensuring timely receipt of appropriate antimicrobial agents to reduce the risk of an adverse outcome.

Infect. Control Hosp. Epidemiol. 2016;37(4):390–397

To study the effect of discontinuation of systematic surveillance for vancomycin-resistant Enterococcus (VRE) and contact isolation of colonized patients on the incidence of VRE bacteremia

A hematology-oncology unit with high prevalence of VRE colonization characterized by predominantly sporadic molecular epidemiology

Inpatients with hematologic malignancies and recipients of hematopoietic stem cell transplantation

The incidence of VRE bacteremia was measured prospectively during 2 different 3-year time periods; the first during active VRE surveillance and contact precautions and the second after discontinuation of these policies. We assessed the collateral impact of this policy change on the incidence of bacteremia due to methicillin-resistant Staphylococcus aureus (MRSA) and Clostridium difficile infection even though we maintained contact precautions for these organisms. Incidence of infectious events was measured as number of events per 1,000 patients days per month. Time series analysis was used to evaluate trends.

The incidence of VRE bacteremia remained stable after discontinuation of VRE surveillance and contact precautions. The incidence of MRSA bacteremia and Clostridium difficile infection for which we continued contact precautions also remained stable. Aggregated antibiotic utilization and nursing hours per patient days were similar between the 2 study periods.

Active surveillance and contact precautions for VRE colonization did not appear to prevent VRE bacteremia in patients with hematologic malignancies and recipients of hematopoietic stem cell transplantation with high prevalence of VRE characterized by predominantly sporadic molecular epidemiology.

Infect. Control Hosp. Epidemiol. 2016;37(4):398–403

Inpatient length of stay (LOS) has been used as a measure of hospital quality and efficiency. Patients with Clostridium difficile infections (CDI) have longer LOS.

To describe the relationship between hospital CDI incidence and the LOS of patients without CDI.

Retrospective cohort analysis.

We predicted average LOS for patients without CDI at both the hospital and patient level using hospital CDI incidence. We also controlled for hospital characteristics (eg, bed size) and patient characteristics (eg, comorbidities, age).

Healthcare Cost and Utilization Project Nationwide Inpatient Sample, 2009–2011.

The Nationwide Inpatient Sample includes patients from a 20% sample of all nonfederal US hospitals.

Inpatient LOS was significantly longer (P<.001) at hospitals with greater CDI incidence at both the hospital and individual level. At a hospital level, a percentage point increase in the CDI incidence rate was associated with more than an additional day’s stay (between 1.19 and 1.61 days). At the individual level, controlling for all observable variables, a percentage point increase in the CDI incidence rate at their hospital was also associated with longer LOS (between 0.6 and 1.05 additional days). Hospital CDI incidence had a larger impact on LOS than many other commonly used predictors of LOS.

CDI rates are a predictor of LOS in patients without CDI at an individual and institutional level. CDI rates are easy to measure and report and thus may provide an important marker for hospital efficiency and/or quality.

Infect. Control Hosp. Epidemiol. 2016;37(4):404–410

Hospital-acquired infections (HAIs) develop rapidly after brief and transient exposures, and ecological exposures are central to their etiology. However, many studies of HAIs risk do not correctly account for the timing of outcomes relative to exposures, and they ignore ecological factors. We aimed to describe statistical practice in the most cited HAI literature as it relates to these issues, and to demonstrate how to implement models that can be used to account for them.

We conducted a literature search to identify 8 frequently cited articles having primary outcomes that were incident HAIs, were based on individual-level data, and used multivariate statistical methods. Next, using an inpatient cohort of incident Clostridium difficile infection (CDI), we compared 3 valid strategies for assessing risk factors for incident infection: a cohort study with time-fixed exposures, a cohort study with time-varying exposures, and a case-control study with time-varying exposures.

Of the 8 studies identified in the literature scan, 3 did not adjust for time-at-risk, 6 did not assess the timing of exposures in a time-window prior to outcome ascertainment, 6 did not include ecological covariates, and 6 did not account for the clustering of outcomes in time and space. Our 3 modeling strategies yielded similar risk-factor estimates for CDI risk.

Several common statistical methods can be used to augment standard regression methods to improve the identification of HAI risk factors.

Infect. Control Hosp. Epidemiol. 2016;37(4):411–419

To identify the frequency of and risk factors associated with complications necessitating removal of the peripherally inserted central catheters (PICCs) in patients receiving outpatient parenteral antibiotic therapy (OPAT) and to determine the appropriateness of OPAT in children with OPAT-related complications.

A retrospective cohort of children who had a PICC inserted at the Johns Hopkins Children’s Center between January 1, 2003, and December 31, 2013, and were discharged from the hospital on OPAT was assembled.

A total of 1,465 PICCs were used to provide antibiotic therapy for 955 children after hospital discharge. Among these, 117 PICCs (8%) required removal due to a complication (4.6 of 1,000 catheter days). Children discharged to a long-term care facility were at increased risk of adverse PICC events (incidence risk ratio [IRR], 3.32; 95% confidence interval [CI], 1.79–6.17). For children receiving OPAT, age of the child (adjusted IRR [aIRR], 0.95; 95% CI, 0.92–0.98), noncentral PICC tip location (aIRR, 2.82; 95% CI, 1.66–4.82), and public insurance (aIRR, 1.63; 95% CI, 1.10–2.40) were associated with adverse PICC events. In addition, 34 patients (32%) with adverse events may not have required intravenous antibiotics at the time of hospital discharge.

Of children discharged with PICCs on OPAT during the study period, 8% developed a complication necessitating PICC removal. Children discharged to a long-term care facility had an increased rate of complication compared with children who were discharged home. With improved education regarding appropriate duration of antibiotic therapy and situations in which early conversion to enteral therapy should be considered, PICC-related complications may have been avoided in 32% of children.

Infect. Control Hosp. Epidemiol. 2016;37(4):420–424

To assess the impact of Matrix-Assisted Laser Desorption/Ionization Time-of-Flight (MALDI-TOF) mass spectrometry for rapid pathogen identification directly from early-positive blood cultures coupled with an antimicrobial stewardship program (ASP) in two community hospitals. Process measures and outcomes prior and after implementation of MALDI-TOF/ASP were evaluated.

Multicenter retrospective study.

Two community hospitals in a system setting, Houston Methodist (HM) Sugar Land Hospital (235 beds) or HM Willowbrook Hospital (241 beds).

Patients ≥18 years of age with culture-proven Gram-negative bacteremia.

Blood cultures from both hospitals were sent to and processed at our central microbiology laboratory. Clinical pharmacists at respective hospitals were notified of pathogen ID and susceptibility results.

We evaluated 572 patients for possible inclusion. After pre-defined exclusion criteria, 151 patients were included in the pre-intervention group and 242 were included in the intervention group. After MALDI-TOF/ASP implementation, the mean identification time after culture positivity was significantly reduced from 32 hours (±16 hours) to 6.5 hours (±5.4 hours) (P<.001); mean time to susceptibility results was significantly reduced from 48 (±22) hours to 23 (±14) hours (P<.001); and time to therapy adjustment was significantly reduced from 75 (±59) hours to 30 (±30) hours (P<.001). Mean hospital costs per patient were $3,411 less in the intervention group compared with the pre-intervention group ($18,645 vs $15,234; P=.04).

This study is the first to analyze the impact of MALDI-TOF coupled with an ASP in a community hospital setting. Time to results significantly differed with the use of MALDI-TOF, and time to appropriate therapy was significantly improved with the addition of ASP.

Infect. Control Hosp. Epidemiol. 2016;37(4):425–432

To offer antimicrobial stewardship to a long-term acute care hospital using telemedicine.

We conducted an uninterrupted time-series analysis to measure the impact of antimicrobial stewardship on hospital-acquired Clostridium difficile infection (CDI) rates and antimicrobial use. Simple linear regression was used to analyze changes in antimicrobial use; Poisson regression was used to estimate the incidence rate ratio in CDI rates. The preimplementation period was April 1, 2010–March 31, 2011; the postimplementation period was April 1, 2011–March 31, 2014.

During the preimplementation period, total antimicrobial usage was 266 defined daily doses (DDD)/1,000 patient-days (PD); it rose 4.54 (95% CI, −0.19 to 9.28) per month then significantly decreased from preimplementation to postimplementation (−6.58 DDD/1,000 PD [95% CI, −11.48 to −1.67]; P=.01). The same trend was observed for antibiotics against methicillin-resistant Staphylococcus aureus (−2.97 DDD/1,000 PD per month [95% CI, −5.65 to −0.30]; P=.03). There was a decrease in usage of anti-CDI antibiotics by 50.4 DDD/1,000 PD per month (95% CI, −71.4 to −29.2; P<.001) at program implementation that was maintained afterwards. Anti-Pseudomonas antibiotics increased after implementation (30.6 DDD/1,000 PD per month [95% CI, 4.9–56.3]; P=.02) but with ongoing education this trend reversed. Intervention was associated with a decrease in hospital-acquired CDI (incidence rate ratio, 0.57 [95% CI, 0.35–0.92]; P=.02).

Antimicrobial stewardship using an electronic medical record via remote access led to a significant decrease in antibacterial usage and a decrease in CDI rates.

Infect. Control Hosp. Epidemiol. 2016;37(4):433–439

Rates of multidrug-resistant gram-negative organisms are surpassing those of methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci in nursing homes (NHs).

To characterize the incidence and duration of carriage of ciprofloxacin-resistant Escherichia coli (CipREc) in NHs and identify those in the O25b-ST131 lineage.

We collected 227 CipREc isolates obtained by routine and regular surveillance of high-risk NH residents with indwelling devices. Repetitive element palindromic (REP)–polymerase chain reaction assay and multiplex polymerase chain reaction amplification for O25b-ST131 E. coli detection were performed using (GTG)5-primers and O25pabBspe and trpA2 primer pairs, respectively.

We found a high period prevalence of CipREc colonization (21.5%), high rates of recolonization with the same strain following clearing (0.46 recolonizations/ person/ year), and an acquisition incidence of 1.05 cases/1,000 person-days. Almost three-quarters of colonized residents carried strains in the O25b-ST131 E. coli lineage. Compared with isolates not in the lineage, O25b-ST131 isolates were carried significantly longer (10 vs 3 months). We identified 18 different REP-types; 2 occurred in 55% of the residents colonized with CipREc, and in more than 1 NH. Duration of CipREc carriage varied by REP-type and averaged 6 months.

CipREc occurred frequently in NH residents and is carried for long durations, and reacquisition following clearance is common

Trial registration. ClinicalTrials.gov identifier: NCT01062841.

Infect. Control Hosp. Epidemiol. 2016;37(4):440–447

To assess antimicrobial utilization before and after a change in urine culture ordering practice in adult intensive care units (ICUs) whereby urine cultures were only performed when pyuria was detected.

Quasi-experimental study

A 700-bed academic medical center

Patients admitted to any adult ICU

Aggregate data for all adult ICUs were obtained for population-level antimicrobial use (days of therapy [DOT]), urine cultures performed, and bacteriuria, all measured per 1,000 patient days before the intervention (January–December 2012) and after the intervention (January–December 2013). These data were compared using interrupted time series negative binomial regression. Randomly selected patient charts from the population of adult ICU patients with orders for urine culture in the presence of indwelling or recently removed urinary catheters were reviewed for demographic, clinical, and antimicrobial use characteristics, and pre- and post-intervention data were compared.

Statistically significant reductions were observed in aggregate monthly rates of urine cultures performed and bacteriuria detected but not in DOT. At the patient level, compared with the pre-intervention group (n=250), in the post-intervention group (n=250), fewer patients started a new antimicrobial therapy based on urine culture results (23% vs 41%, P=.002), but no difference in the mean total DOT was observed.

A change in urine-culture ordering practice was associated with a decrease in the percentage of patients starting a new antimicrobial therapy based on the index urine-culture order but not in total duration of antimicrobial use in adult ICUs. Other drivers of antimicrobial use in ICU patients need to be evaluated by antimicrobial stewardship teams.

Infect. Control Hosp. Epidemiol. 2016;37(4):448–454

Surgical site infections (SSIs) are common hospital-acquired infections. Tracking SSIs is important to monitor their incidence, and this process requires primary data collection. In this study, we derived and validated a method using health administrative data to predict the probability that a person who had surgery would develop an SSI within 30 days.

All patients enrolled in the National Surgical Quality Improvement Program (NSQIP) from 2 sites were linked to population-based administrative datasets in Ontario, Canada. We derived a multivariate model, stratified by surgical specialty, to determine the independent association of SSI status with patient and hospitalization covariates as well as physician claim codes. This SSI risk model was validated in 2 cohorts.

The derivation cohort included 5,359 patients with a 30-day SSI incidence of 6.0% (n=118). The SSI risk model predicted the probability that a person had an SSI based on 7 covariates: index hospitalization diagnostic score; physician claims score; emergency visit diagnostic score; operation duration; surgical service; and potential SSI codes. More than 90% of patients had predicted SSI risks lower than 10%. In the derivation group, model discrimination and calibration was excellent (C statistic, 0.912; Hosmer-Lemeshow [H-L] statistic, P=.47). In the 2 validation groups, performance decreased slightly (C statistics, 0.853 and 0.812; H-L statistics, 26.4 [P=.0009] and 8.0 [P=.42]), but low-risk patients were accurately identified.

Health administrative data can effectively identify postoperative patients with a very low risk of surgical site infection within 30 days of their procedure. Records of higher-risk patients can be reviewed to confirm SSI status.

Infect. Control Hosp. Epidemiol. 2016;37(4):455–465