Quasi-experimental study designs, often described as nonrandomized, pre-post intervention studies, are common in the medical informatics literature. Yet little has been written about the benefits and limitations of the quasi-experimental approach as applied to informatics studies. This paper outlines a relative hierarchy and nomenclature of quasi-experimental study designs that is applicable to medical informatics intervention studies. In addition, the authors performed a systematic review of two medical informatics journals, the Journal of the American Medical Informatics Association (JAMIA) and the International Journal of Medical Informatics (IJMI), to determine the number of quasi-experimental studies published and how the studies are classified on the above-mentioned relative hierarchy. They hope that future medical informatics studies will implement higher level quasi-experimental study designs that yield more convincing evidence for causal links between medical informatics interventions and outcomes.

Current shortages in COVID-19 vaccine production and distribution have led some experts to suggest untested regimens. 1 Persons who have had COVID-19 are thought to have protective immunity and memory responses 2 for at least 6 months; however, neither recall responses nor ideal vaccine dosing regimens have been studied in those previously infected with SARS-CoV-2. We assessed whether health care workers with previous COVID-19 infection could mount recall responses to a single dose of an mRNA-based COVID-19 vaccine. Methods | Health care workers who had previously enrolled in a hospital-wide serosurvey study, 3 conducted from July to August 2020 at the University of Maryland Medical Center, were randomly contacted based on stratification into 3 groups: SARS-CoV-2 IgG-antibody negative (Ab-negative); IgG-positive asymptomatic COVID-19 (asymptomatic); and IgG-positive with history of symptomatic COVID-19 (symptomatic). Participants were vaccinated with either the Pfizer-BioNTech or Moderna vaccine, depending on personal preference and availability. Blood was drawn at days 0 (baseline), 7, and 14 postvaccination in December 2020 and January 2021 (draws could be within 1 day from assigned day). Plasma was tested using enzyme-linked immunosorbent assay (ELISA) for IgG to spike trimer, which was modified from an assay 4 to give a readout of half-maximal binding titers. The reciprocal half-maximal binding titers represent

Acinetobacter infections have increased and gained attention because of the organism’s prolonged environmental survival and propensity to develop antimicrobial drug resistance. The effect of multidrug-resistant (MDR) Acinetobacter infection on clinical outcomes has not been reported. A retrospective, matched cohort investigation was performed at 2 Baltimore hospitals to examine outcomes of patients with MDR Acinetobacter infection compared with patients with susceptible Acinetobacter infections and patients without Acinetobacter infections. Multivariable analysis controlling for severity of illness and underlying disease identified an independent association between patients with MDR Acinetobacter infection (n = 96) and increased hospital and intensive care unit length of stay compared with 91 patients with susceptible Acinetobacter infection (odds ratio [OR] 2.5, 95% confidence interval [CI] 1.2–5.2 and OR 2.1, 95% CI 1.0–4.3] respectively) and 89 uninfected patients (OR 2.5, 95% CI 1.2–5.4 and OR 4.2, 95% CI 1.5–11.6] respectively). Increased hospitalization associated with MDR Acinetobacter infection emphasizes the need for infection control strategies to prevent cross-transmission in healthcare settings.

Antibiotic use is known to promote the development of antibiotic resistance, but substantial controversy exists about the impact of agricultural antibiotic use (AAU) on the subsequent emergence of antibiotic-resistant bacteria among humans. AAU for animal growth promotion or for treatment or control of animal diseases generates reservoirs of antibiotic-resistant (AR) bacteria that contaminate animal food products. Mathematical models are an important tool for understanding the potential medical consequences of this increased exposure. We have developed a mathematical model to evaluate factors affecting the prevalence of human commensal AR bacteria that cause opportunistic infections (e.g., enterococci). Our analysis suggests that AAU hastens the appearance of AR bacteria in humans. Our model indicates that the greatest impact occurs very early in the emergence of resistance, when AR bacteria are rare, possibly below the detection limits of current surveillance methods.T he development of antibiotic resistance (AR) among pathogenic bacteria has emerged as a major public health concern. The appearance of AR has been directly linked with the use and overuse of antibiotics (1-4). It was reported that as much as 80% of total antibiotic production in the United States is used in agriculture, with a substantial portion of this used for the nontherapeutic purpose of growth promotion (4, 5). AR bacteria have been found in farm animals where antibiotics are heavily used (6-8), in associated food products (9, 10), in environments contaminated by animal waste (11,12), and in farm workers (13)(14)(15). Drugs that are used therapeutically in animals also may generate a reservoir of AR bacteria (16,17). AR bacteria in food animals threaten the efficacy of human drugs if AR bacteria or AR genes become incorporated into bacteria populations colonizing humans. To provide a basis for public policy discussions about agricultural antibiotic use (AAU), we have developed a mathematical model to quantify the medical consequences.AAU may cause AR bacterial infections in humans by two different processes. First, AAU increases the frequency of AR in zoonotic pathogens such as Campylobacter or Salmonella. These pathogens are typically acquired through exposure to contaminated animal food products. Human-to-human transmission of zoonotic pathogens is rare, although it may occur in settings where humans are immuno-compromised or where the gut community has been disturbed by heavy medical antibiotic use (MAU; ref. 18). Therefore, the incidence of AR in zoonotic infections of humans is directly related to the prevalence of AR bacteria in food animals. A risk-assessment model examining resistance in a zoonotic pathogen was recently proposed by FDA (see http:͞͞www.fda.gov͞cvm͞antimicrobial͞Risk asses.htm).Second, AR bacteria from food animals may facilitate the development of AR in human commensal bacteria which ordinarily colonize humans without causing infection. Commensal bacteria typically have long persistence times, frequent humanto-human ...

Background Patient-to-patient transmission of nosocomial pathogens has been linked to transient colonization of health care workers, and studies have suggested that contamination of health care workers' clothing, including white coats, may be a vector for this transmission. Methods We performed a cross-sectional study involving attendees of medical and surgical grand rounds at a large teaching hospital to investigate the prevalence of contamination of white coats with important nosocomial pathogens, such as methicillin-sensitive Stapylococcus aureus, methicillin-resistant S aureus (MRSA), and vancomycin-resistant enterococci (VRE). Each participant completed a brief survey and cultured his or her white coat using a moistened culture swab on lapels, pockets, and cuffs. Results Among the 149 grand rounds attendees' white coats, 34 (23%) were contaminated with S aureus, of which 6 (18%) were MRSA. None of the coats was contaminated with VRE. S aureus contamination was more prevalent in residents, those working in inpatient settings, and those who saw an inpatient that day. Conclusion This study suggests that a large proportion of health care workers' white coats may be contaminated with S aureus, including MRSA. White coats may be an important vector for patient-to-patient transmission of S aureus.

Our findings suggest that CP-CRE may be more virulent than non-CP-CRE and are associated with poorer outcomes. This underscores the added importance of delineating underlying resistance mechanisms of CRE to direct antibiotic treatment decisions.

PTZ appears inferior to carbapenems for the treatment of ESBL bacteremia. For patients at high risk of invasive ESBL infections, early carbapenem therapy should be considered. Our findings should not be extended to β-lactam/β-lactamase inhibitor combinations in development, as limited clinical data are available for these agents.

Case-control studies that analyze the risk factors for antibiotic-resistant organisms have varied epidemiological methodologies, which may lead to biased estimates of antibiotic risk factors. A systematic review of case-control studies that analyzed risk factors for antibiotic-resistant organisms addressed 3 methodological principles: method of control group selection, adjustment for time at risk, and adjustment for comorbid illness. A total of 406 abstracts were reviewed. Thirty-seven studies met the inclusion and exclusion criteria and were reviewed and evaluated for the 3 methodological principles. Thirteen (35%) of 37 studies chose the preferred control group. Eleven adjusted for time at risk. Twenty-seven adjusted for comorbid illness. Future studies need to consider more closely the optimization of control group selection, adjusting for confounding caused by time at risk, and adjusting for confounding caused by comorbid illness.