Judith Strymish

Objective surveillance definitions for ventilator-associated pneumonia.

Objectives: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. Design: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. Setting:Medical and surgical intensive care units in eight U.S. hospitals (four tertiary centers, three community hospitals, and one Veterans Affairs institution). Patients:Eight thousand seven hundred thirty-five consecutive episodes of mechanical ventilation for adult patients. Interventions: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. Measurements and Main Results: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. Conclusions: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.

Preoperative Nasal Methicillin-Resistant Staphylococcus aureus Status, Surgical Prophylaxis, and Risk-Adjusted Postoperative Outcomes in Veterans

OBJECTIVES To determine whether preoperative nasal methicillin-resistant Staphylococcus aureus (MRSA) carriage is a significant predictor of postoperative infections, after accounting for surgical infection risk and surgical prophylaxis. DESIGN Retrospective cohort study. PATIENTS Veterans Affairs (VA) Boston patients who had nasal MRSA polymerase chain reaction screening performed in the 31 days before clean or clean contaminated surgery in 2008-2009. METHODS Postoperative MRSA clinical cultures and infections, total surgical site infections (SSIs), and surgical prophylaxis data were abstracted from administrative databases. MRSA infections were confirmed via chart review. Multivariate analysis of risk factors for each outcome was conducted using Poisson regression. SSI risk index was calculated for a subset of 1,551 patients assessed by the VA National Surgical Quality Improvement Program. RESULTS Among 4,238 eligible patients, 279 (6.6%) were positive for preoperative nasal MRSA. Postoperative MRSA clinical cultures and infections, including MRSA SSIs, were each significantly increased in patients with preoperative nasal MRSA. After adjustment for surgery type, vancomycin prophylaxis, chlorhexidine/alcohol surgical skin preparation, and SSI risk index, preoperative nasal MRSA remained significantly associated with postoperative MRSA cultures (relative risk [RR], 8.81; 95% confidence interval [CI], 3.01-25.82) and infections (RR, 8.46; 95% CI, 1.70-42.04). Vancomycin prophylaxis was associated with an increased risk of total SSI in those negative for nasal MRSA (RR, 4.34; 95% CI, 2.19-8.57) but not in patients positive for nasal MRSA. CONCLUSIONS In our population, preoperative nasal MRSA colonization was independently associated with MRSA clinical cultures and infections in the postoperative period. Vancomycin prophylaxis increased the risk of total SSI in nasal MRSA-negative patients.

Extranasal Methicillin-Resistant Staphylococcus aureus Colonization at Admission to an Acute Care Veterans Affairs Hospital

OBJECTIVE To evaluate the prevalence of and risk factors for extranasal methicillin-resistant Staphylococcus aureus (MRSA) colonization and its relationship to nasal colonization among veterans hospitalized for acute care. DESIGN Prospective observational study. SETTING Veterans Affairs (VA) acute care hospital in Boston, Massachusetts. PATIENTS Convenience sample of 150 patients hospitalized within the previous 36 hours and screened for nasal MRSA who were not known to have an active MRSA infection or MRSA isolates recovered from a wound during the past 12 months. METHODS Potential risk factors for MRSA colonization were assessed, and oropharynx, axilla, hand, perirectal, wound, and catheter insertion site samples were obtained for culture. MRSA was identified in chromogenic agar and confirmed by use of routine culture techniques. Nasal MRSA colonization was detected by means of polymerase chain reaction (PCR). RESULTS Nasal swab samples analyzed by use of PCR yielded results positive for MRSA in 16 (11%) of 150 patients. Extranasal cultures yielded positive results for 3 (2%) of 134 patients who tested negative for nasal MRSA colonization and for 9 (56%) of 16 patients who tested positive for nasal MRSA colonization (odds ratio [OR], 56.1 [95% confidence interval {CI}, 12.4-254.6]; p < .001). The oropharynx was the most commonly colonized extranasal site (10 patients [7%]). Independent risk factors for extranasal MRSA colonization included nasal MRSA colonization (OR, 66.9 [95% CI, 11.8-379.7]; P < .001) and end-stage hepatic disease (OR, 98.5 [95% CI, 3.1-3,112.4]; P = .01). CONCLUSIONS Extranasal MRSA colonization is infrequent among veterans admitted for acute care to VA Boston Healthcare System. Extranasal MRSA colonization was strongly associated with nasal MRSA colonization, which suggests that the VA MRSA Prevention Initiative is not missing a large number of MRSA-colonized patients by focusing on nasal-only screening.

Simplified surveillance for nosocomial bloodstream infections

OBJECTIVE To compare a surveillance definition of noso comial bloodstream infections requiring only microbiology data to the Centers for Disease Control and Preventions (CDC) current definition. SETTING Six teaching hospitals. METHODS We classified a representative sample of 73 positive blood cultures from six hospitals growing common skin contaminant isolates using a definition for bacteremia requiring only microbiology data and the CDC definition for primary bloodstream infection (National Nosocomial Infections Surveillance [NNIS] System review method). The classifications assigned during routine prospective surveillance also were noted, and the time required to classify isolates by the two methods was compared. RESULTS Among 65 blood cultures growing common skin contaminant isolates obtained from adults, the agreement rate between the microbiology data method and the NNIS review method was 91%. Agreement was significantly poorer for the eight blood cultures growing common skin contaminant isolates obtained from pediatric patients. The microbiology data method requires approximately 20 minutes less time per isolate than does routine surveillance. CONCLUSIONS A definition based on microbiology data alone yields the same result as the CDCs definition in the large majority of instances. It is more resource-efficient than the CDCs current definition.

Electronic Memorandum Decreases Unnecessary Antimicrobial Use for Asymptomatic Bacteriuria and Culture-Negative Pyuria

OBJECTIVES Asymptomatic bacteriuria/candidiuria (ASB) and culture-negative pyuria (CNP) are common and often result in inappropriate antibiotic use. We aimed to evaluate whether a standardized educational memorandum could reduce antimicrobial utilization for ASB/CNP. DESIGN, SETTING, AND PATIENTS Quasi-experimental study with a control group, from a convenience sample of inpatients with abnormal urinalysis or urine culture results in a Veterans Affairs hospital. INTERVENTION An educational memorandum outlining guidelines for diagnosis and treatment of ASB was placed in the chart of patients with ASB/CNP who were receiving antimicrobials. METHODS The records of patients meeting inclusion criteria were abstracted for demographics, comorbidities, antimicrobials, and symptoms suggestive of possible urinary tract infection (UTI). Patients were categorized as having ASB, CNP, or UTI. The number of antimicrobial-days attributed to ASB/CNP was compared between the control group and the intervention group. RESULTS Charts of 301 patients with abnormal urine results were reviewed. Thirty of 117 (26%) patients in the control group received antimicrobials for ASB/CNP for an average of 6.3 days. In the intervention group, 24 of 92 (26%) patients received antimicrobials for ASB/CNP for an average of 2.2 days (t-test: P < .001). Adverse events from antimicrobials for ASB/CNP occurred in 3 of the 30 (10%) patients in the control group. There were no adverse events from untreated ASB/CNP in the intervention group. CONCLUSIONS ASB and CNP resulted in antimicrobial exposure in more than one-quarter of our study patients. Placing a standardized memorandum in the electronic record was associated with a 65% relative reduction in antimicrobial-days for ASB and CNP.

Medicine's uncomfortable relationship with math: calculating positive predictive value.

In 1978, Casscells et al1 published a small but important study showing that the majority of physicians, house officers, and students overestimated the positive predictive value (PPV) of a laboratory test result using prevalence and false positive rate. Today, interpretation of diagnostic tests is even more critical with the increasing use of medical technology in health care. Accordingly, we replicated the study by Casscells et al1 by asking a convenience sample of physicians, house officers, and students the same question: “If a test to detect a disease whose prevalence is 1/1000 has a false positive rate of 5%, what is the chance that a person found to have a positive result actually has the disease, assuming you know nothing about the person’s symptoms or signs?”

MRSA Nasal Carriage Patterns and the Subsequent Risk of Conversion between Patterns, Infection, and Death

Background Patterns of methicillin-resistant S. aureus (MRSA) nasal carriage over time and across the continuum of care settings are poorly characterized. Knowledge of prevalence rates and outcomes associated with MRSA nasal carriage patterns could help direct infection prevention strategies. The VA integrated health-care system and active surveillance program provides an opportunity to delineate nasal carriage patterns and associated outcomes of death, infection, and conversion in carriage. Methods/Findings We conducted a retrospective cohort study including all patients admitted to 5 acute care VA hospitals between 2008–2010 who had nasal MRSA PCR testing within 48 hours of admission and repeat testing within 30 days. The PCR results were used to define a baseline nasal carriage pattern of never, intermittently, or always colonized at 30 days from admission. Follow-up was up to two years and included acute, long-term, and outpatient care visits. Among 18,038 patients, 91.1%, 4.4%, and 4.6% were never, intermittently, or always colonized at the 30-day baseline. Compared to non-colonized patients, those who were persistently colonized had an increased risk of death (HR 2.58; 95% CI 2.18;3.05) and MRSA infection (HR 10.89; 95% CI 8.6;13.7). Being in the non-colonized group at 30 days had a predictive value of 87% for being non-colonized at 1 year. Conversion to MRSA colonized at 6 months occurred in 11.8% of initially non-colonized patients. Age >70 years, long-term care, antibiotic exposure, and diabetes identified >95% of converters. Conclusions The vast majority of patients are not nasally colonized with MRSA at 30 days from acute hospital admission. Conversion from non-carriage is infrequent and can be risk-stratified. A positive carriage pattern is strongly associated with infection and death. Active surveillance programs in the year following carriage pattern designation could be tailored to focus on non-colonized patients who are at high risk for conversion, reducing universal screening burden.

Activity of Fosfomycin against Extended-Spectrum-β-Lactamase-Producing Uropathogens in Patients in the Community and Hospitalized Patients

ABSTRACT Few oral antibiotics exist for the empirical treatment of extended-spectrum β-lactamase (ESBL) urinary tract infections (UTI). In this study, we sought to determine the activity of fosfomycin against ESBL-producing uropathogens from patients at 3 Veterans Affairs (VA) facilities between 2010 and 2013. Among the ESBL uropathogens, 19.9% were fosfomycin resistant. Klebsiella species were more likely than Escherichia coli to be resistant (46% versus 4%; P < 0.001). Fosfomycin remains active against a majority of the ESBL uropathogens, although resistance among Klebsiella spp. was higher than that in previous reports.

Do pneumonia readmissions flagged as potentially preventable by the 3M PPR software have more process of care problems? A cross-sectional observational study

Background In the USA, administrative data-based readmission rates such as the Centers for Medicare and Medicaid Services’ all-cause readmission measures are used for public reporting and hospital payment penalties. To improve this measure and identify better quality improvement targets, 3M developed the Potentially Preventable Readmissions (PPRs) measure. It matches clinically related index admission and readmission diagnoses that may indicate readmissions resulting from admission- or post-discharge-related quality problems. Objective To examine whether PPR software-flagged pneumonia readmissions are associated with poorer quality of care. Methods Using a retrospective observational study design and Veterans Health Administration (VA) data, we identified pneumonia discharges associated with 30-day readmissions, and then flagged cases as PPR–yes or PPR–no using the PPR software. To assess quality of care, we abstracted electronic medical records of 100 random readmissions using a tool containing explicit care processes organised into admission work-up, in-hospital evaluation/treatment, discharge readiness and post-discharge period. We derived quality scores, scaled to a maximum of 25 per section (maximum total score=100) and compared cases by total and section-specific mean scores using t tests and effect size (ES) to characterise the clinical significance of findings. Results Our abstraction sample was selected from 11 278 pneumonia readmissions (readmission rate=16.5%) during 1 October 2005–30 September 2010; 77% were flagged as PPR–yes. Contrary to expectations, total and section mean quality scores were slightly higher, although non-significantly, among PPR–yes (N=77) versus PPR–no (N=23) cases (respective total scores, 71.2±8.7 vs 65.8±11.5, p=0.14); differences demonstrated ES >0.30 overall and for admission work-up and post-discharge period sections. Conclusions Among VA pneumonia readmissions, PPR categorisation did not produce the expected quality of care findings. Either PPR–yes cases are not more preventable, or preventability assessment requires other data collection methods to capture poorly documented processes (eg, direct observation).

Risk of surgical site infection, acute kidney injury, and Clostridium difficile infection following antibiotic prophylaxis with vancomycin plus a beta-lactam versus either drug alone: A national propensity-score-adjusted retrospective cohort study

Background The optimal regimen for perioperative antimicrobial prophylaxis is controversial. Use of combination prophylaxis with a beta-lactam plus vancomycin is increasing; however, the relative risks and benefits associated with this strategy are unknown. Thus, we sought to compare postoperative outcomes following administration of 2 antimicrobials versus a single agent for the prevention of surgical site infections (SSIs). Potential harms associated with combination regimens, including acute kidney injury (AKI) and Clostridium difficile infection (CDI), were also considered. Methods and findings Using a multicenter, national Veterans Affairs (VA) cohort, all patients who underwent cardiac, orthopedic joint replacement, vascular, colorectal, and hysterectomy procedures during the period from 1 October 2008 to 30 September 2013 and who received planned manual review of perioperative antimicrobial prophylaxis regimen and manual review for the 30-day incidence of SSI were included. Using a propensity-adjusted log-binomial regression model stratified by type of surgical procedure, the association between receipt of 2 antimicrobials (vancomycin plus a beta-lactam) versus either single agent alone (vancomycin or a beta-lactam) and SSI was evaluated. Measures of association were adjusted for age, diabetes, smoking, American Society of Anesthesiologists score, preoperative methicillin-resistant Staphylococcus aureus (MRSA) status, and receipt of mupirocin. The 7-day incidence of postoperative AKI and 90-day incidence of CDI were also measured. In all, 70,101 procedures (52,504 beta-lactam only, 5,089 vancomycin only, and 12,508 combination) with 2,466 (3.5%) SSIs from 109 medical centers were included. Among cardiac surgery patients, combination prophylaxis was associated with a lower incidence of SSI (66/6,953, 0.95%) than single-agent prophylaxis (190/12,834, 1.48%; crude risk ratio [RR] 0.64, 95% CI 0.49, 0.85; adjusted RR 0.61, 95% CI 0.46, 0.83). After adjusting for SSI risk, no association between receipt of combination prophylaxis and SSI was found for the other types of surgeries evaluated, including orthopedic joint replacement procedures. In MRSA-colonized patients undergoing cardiac surgery, SSI occurred in 8/346 (2.3%) patients who received combination prophylaxis versus 4/100 (4.0%) patients who received vancomycin alone (crude RR 0.58, 95% CI 0.18, 1.88). Among MRSA-negative and -unknown cardiac surgery patients, SSIs occurred in 58/6,607 (0.9%) patients receiving combination prophylaxis versus 146/10,215 (1.4%) patients who received a beta-lactam alone (crude RR 0.61, 95% CI 0.45, 0.83). Based on these associations, the number needed to treat to prevent 1 SSI in MRSA-colonized patients is estimated to be 53, compared to 176 in non-MRSA patients. CDI incidence was similar in both exposure groups. Across all types of surgical procedures, risk of AKI was increased in the combination antimicrobial prophylaxis group (2,971/12,508 [23.8%] receiving combination versus 1,058/5,089 [20.8%] receiving vancomycin alone versus 7,314/52,504 [13.9%] receiving beta-lactam alone). We found a significant association between absolute risk of AKI and receipt of combination regimens across all types of procedures. If the observed association is causal, the number needed to harm for severe AKI following cardiac surgery would be 167. The major limitation of our investigation is that it is an observational study in a predominantly male population, which may limit generalizability and lead to unmeasured confounding. Conclusions There are benefits but also unintended consequences of antimicrobial and infection prevention strategies aimed at “getting to zero” healthcare-associated infections. In our study, combination prophylaxis was associated with both benefits (reduction in SSIs following cardiac surgical procedures) and harms (increase in postoperative AKI). In cardiac surgery patients, the difference in risk–benefit profile by MRSA status suggests that MRSA-screening-directed prophylaxis may optimize benefits while minimizing harms in this selected population. More information about long-term outcomes and patient and societal preferences regarding risk of SSI versus risk of AKI is needed to improve clinical decision-making.