Do Different Methods for Modeling Age-Graded Trajectories Yield Consistent and Valid Results?

Data on age-sequenced trajectories of individuals' attributes are used for a growing number of research purposes. However, there is no consensus about which method to use to identify the number of discrete trajectories in a population or to assign individuals to a specific trajectory group. We modeled real and simulated trajectory data using "naïve" methods, optimal matching, grade of membership models, and three types of finite mixture models. We found that these methods produced inferences about the number of trajectories that frequently differ (1) from one another and (2) from the truth as represented by simulation parameters. We also found that they differed in the assignment of individuals to trajectory groups. In light of these findings, we argue that researchers should interpret results based on these methods cautiously, neither reifying point estimates about the number of trajectories nor treating individuals' trajectory group assignments as certain.

Precarious employment, bad jobs, labor unions, and early retirement.

OBJECTIVES: We examined the extent to which involuntary job loss, exposure to "bad jobs," and labor union membership across the life course are associated with the risk of early retirement. METHODS: Using data from the Wisconsin Longitudinal Study, a large (N=8,609) sample of men and women who graduated from high school in 1957, we estimated discrete-time event history models for the transition to first retirement through age 65. We estimated models separately for men and women. RESULTS: We found that experience of involuntary job loss and exposure to bad jobs are associated with a lower risk of retiring before age 65, whereas labor union membership is associated with a higher likelihood of early retirement. These relationships are stronger for men than for women and are mediated to some extent by pre-retirement differences in pension eligibility, wealth, job characteristics, and health. DISCUSSION: Results provide some support for hypotheses derived from theories of cumulative stratification, suggesting that earlier employment experiences should influence retirement outcomes indirectly through later-life characteristics. However, midlife employment experiences remain associated with earlier retirement, net of more temporally proximate correlates, highlighting the need for further theorization and empirical evaluation of the mechanisms through which increasingly common employment experiences influence the age at which older Americans retire.

Later-life Employment Preferences and Outcomes: The Role of Mid-life Work Experiences.

In this paper, we evaluate relationships between mid-life work experiences and the realization of preferences for full-time employment, part-time employment, and complete retirement at age 63-64. Using rich data from the Wisconsin Longitudinal Study, we demonstrate that the likelihood of achieving one's preferred employment status is related to earlier work experiences including employment stability in mid-life and self-employment, part-time employment, and private pension coverage across the life course. Despite large gender differences in work experiences across the life course, relationships between earlier work experiences and the likelihood of realizing later-life employment preferences are generally similar for men and women. We also find that these relationships are only partially mediated by economic and employment circumstances in late mid-life, suggesting the need for further evaluation of the cumulative pathways linking mid-life work experiences to the realization of later-life employment preferences.

Contamination of examination gloves in patient rooms and implications for transmission of antimicrobial-resistant microorganisms .

An assessment of bacterial contamination on examination gloves indicated that contaminated gloves may be a mechanism of indirect bacterial transmission from the hands of healthcare workers to patients. This mechanism is indicated by the recovery of identical Acinetobacter baumannii isolates from gloves and from the clinical cultures of a patient with invasive infection.

In vitro activities of various antimicrobials alone and in combination with tigecycline against carbapenem-intermediate or -resistant Acinetobacter baumannii.

The activities of tigecycline alone and in combination with other antimicrobials are not well defined for carbapenem-intermediate or -resistant Acinetobacter baumannii (CIRA). Pharmacodynamic activity is even less well defined when clinically achievable serum concentrations are considered. Antimicrobial susceptibility testing of clinical CIRA isolates from 2001 to 2005 was performed by broth or agar dilution, as appropriate. Tigecycline concentrations were serially increased in time-kill studies with a representative of the most prevalent carbapenem-resistant clone (strain AA557; imipenem MIC, 64 mg/liter). The in vitro susceptibility of the strain was tested by time-kill studies in duplicate against the average free serum steady-state concentrations of tigecycline alone and in combination with various antimicrobials. Ninety-three CIRA isolates were tested and were found to have the following antimicrobial susceptibility profiles: tigecycline, MIC(50) of 1 mg/liter and MIC(90) of 2 mg/liter; minocycline, MIC(50) of 0.5 mg/liter and MIC(90) of 8 mg/liter; doxycycline, MIC(50) of 2 mg/liter and MIC(90) of > or =32 mg/liter; ampicillin-sulbactam, MIC(50) of 48 mg/liter and MIC(90) of 96 mg/liter; ciprofloxacin, MIC(50) of > or =16 mg/liter and MIC(90) of > or =16 mg/liter; rifampin, MIC(50) of 4 mg/liter and MIC(90) of 8 mg/liter; polymyxin B, MIC(50) of 1 mg/liter and MIC(90) of 1 mg/liter; amikacin, MIC(50) of 32 mg/liter and MIC(90) of > or =32 mg/liter; meropenem, MIC(50) of 16 mg/liter and MIC(90) of > or =128 mg/liter; and imipenem, MIC(50) of 4 mg/liter and MIC(90) of 64 mg/liter. Among the tetracyclines, the isolates were more susceptible to tigecycline than minocycline and doxycycline, according to FDA breakpoints (95%, 88%, and 71% of the isolates were susceptible to tigecycline, minocycline, and doxycycline, respectively). Concentration escalation studies with tigecycline revealed a maximal killing effect near the MIC, with no additional extent or rate of killing at concentrations 2x to 4x the MIC for tigecycline. Time-kill studies demonstrated indifference for tigecycline in combination with the antimicrobials tested. Polymyxin B, minocycline, and tigecycline are the most active antimicrobials in vitro against CIRA. Concentration escalation studies demonstrate that tigecycline may need to approach concentrations higher than those currently achieved in the bloodstream to adequately treat CIRA bloodstream infections. Future studies should evaluate these findings in vivo.

The clinical impact of linezolid susceptibility reporting in patients with vancomycin-resistant enterococci.

Linezolid remains a mainstay of therapy for vancomycin-resistant enterococci (VREs), but resistance has emerged. We describe a cohort of 20 patients with linezolid-intermediate or resistant VRE (LIRVRE) reported by Etest and disk diffusion testing, 18 of whom demonstrated linezolid susceptibility by agar dilution on further investigation. Patients with reported LIRVRE were matched based on culture site and enterococcal species to patients with linezolid-susceptible VRE (LSVRE) in a 1:3 ratio. Patients with reported LIRVRE developed more nosocomial infections (P = .04), had more central lines placed (P = .04), and underwent more computed tomography scans related to VRE infection (P = .02). Multivariate analysis revealed increased surgical procedures related to VRE infections (P = .008), increased linezolid use during hospital stay (P = .03), and delayed culture and susceptibility results compared with those with LSVRE (P = .006). Therefore, inaccurate detection and reporting of LIRVRE by disk diffusion and Etest is associated with increased patient morbidity and resource use.

Assessment of materials commonly utilized in health care: implications for bacterial survival and transmission.

BACKGROUND: Contaminated environmental surfaces, equipment, and health care workers' hands have been linked to outbreaks of infection or colonization because of vancomycin-resistant enterococci (VRE) and Pseudomonas aeruginosa (PSAE). Upholstery, walls, and flooring may enhance bacterial survival, providing infectious reservoirs. OBJECTIVES: Investigate recovery of VRE and PSAE, determine efficacy of disinfection, and evaluate VRE transmission from surfaces. METHODS: Upholstery, flooring, and wall coverings were inoculated with VRE and PSAE and assessed for recovery at 24 hours, 72 hours, and 7 days. Inoculated surfaces were cleaned utilizing manufacturers' recommendations of natural, commercial, or hospital-approved products and methods, and samples were obtained. To assess potential for transmission, volunteers touched VRE-inoculated surfaces and imprinted palms onto contact-impression plates. RESULTS: Twenty-four hours following inoculation, all surfaces had recovery of VRE; 13 (92.9%) of 14 surfaces had persistent PSAE. After cleaning, VRE was recovered from 7 (50%) surfaces, PSAE from 5 (35.7%) surfaces. After inoculation followed by palmar contact, VRE was recovered from all surfaces touched. CONCLUSION: Bacteria commonly encountered in hospitals are capable of prolonged survival and may promote cross transmission. Selection of surfaces for health care environments should include product application and complexity of manufacturers' recommendations for disinfection. Recovery of organisms on surfaces and hands emphasizes importance of hand hygiene compliance prior to patient contact.

Comparison of testing methods for detection of decreased linezolid susceptibility due to G2576T mutation of the 23S rRNA gene in Enterococcus faecium and Enterococcus faecalis.

E-test, Vitek 2, MicroScan, agar dilution, and disk diffusion were compared for detection of decreased linezolid susceptibility due to 23S rRNA gene G2576T mutation among 32 clinical Enterococcus strains initially reported as intermediate or resistant by E-test alone or Vitek 2 confirmed by E-test. Agar and broth dilution methods were in concordance with PCR detection of the mutation, and disk diffusion was somewhat less sensitive but equally specific.

Fatal case of endocarditis due to Weissella confusa.

This is the first reported case of endocarditis due to the Lactobacillus-like vancomycin-resistant gram-positive bacillus Weissella confusa. Full identification and susceptibility testing of Lactobacillus-like organisms recovered in blood culture should be performed for patients with clinical presentations that suggest endocarditis.