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Biomedical subjects

Anthony D Harris

Publications and source records attributed to Anthony D Harris.

35 records · Page 2Linked to original sources
PubMed2004

Persistent colonization and the spread of antibiotic resistance in nosocomial pathogens: resistance is a regional problem.

Infections with antibiotic-resistant bacteria (ARB) in hospitalized patients are becoming increasingly frequent despite extensive infection-control efforts. Infections with ARB are most common in the intensive care units of tertiary-care hospitals, but the underlying cause of the increases may be a steady increase in the number of asymptomatic carriers entering hospitals. Carriers may shed ARB for years but remain undetected, transmitting ARB to others as they move among hospitals, long-term care facilities, and the community. We apply structured population models to explore the dynamics of ARB, addressing the following questions: (i) What is the relationship between the proportion of carriers admitted to a hospital, transmission, and the risk of infection with ARB? (ii) How do frequently hospitalized patients contribute to epidemics of ARB? (iii) How do transmission in the community, long-term care facilities, and hospitals interact to determine the proportion of the population that is carrying ARB? We offer an explanation for why ARB epidemics have fast and slow phases and why resistance may continue to increase despite infection-control efforts. To successfully manage ARB at tertiary-care hospitals, regional coordination of infection control may be necessary, including tracking asymptomatic carriers through health-care systems.

Bacterial Infections↗
PubMed2004

Acceptable rates of treatment failure in osteomyelitis involving the diabetic foot: a survey of infectious diseases consultants.

Shortening the duration of antibiotic therapy is an attractive strategy for delaying the emergence of antimicrobial resistance. The paucity of data about optimal treatment durations hinders adoption of this approach. This study used contingent valuation analysis to identify failure rates for treatment of diabetic foot osteomyelitis acceptable to infectious diseases consultants (IDCs). The Infectious Diseases Society of America's Emerging Infections Network (EIN) provided members with the case scenario and 1 of 10 failure rates; members were asked, assuming delivery of standard therapy, if they would accept or reject the given failure rate. The relationship between specific failure rates and the willingness of IDCs to accept them was analyzed. The median acceptable failure rate for EIN members was 18.1%; 75% of IDCs found a failure rate of 7.8% to be acceptable, and 25% found a rate of 28.4% to be acceptable. The methodology used in this study may prove useful in delineating acceptable treatment failure thresholds, an initial step in shortening durations of antimicrobial therapy.

Adult↗
PubMed2004

Prediction rules to identify patients with methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci upon hospital admission.

BACKGROUND: In 2003, the Society of Healthcare Epidemiology of America (SHEA) recommended surveillance cultures upon hospital admission for patients at high risk for carriage of vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA). The aim of this study was to assess the validity of factors from past medical history in defining patients at high risk for subsequent positive cultures with VRE or MRSA upon hospital admission. METHODS: Subjects were adult inpatients admitted to nonintensive care wards of the index hospital during 2001-2002. Cases had MRSA or VRE positive clinical cultures within 48 hours of hospital admission. Patients with previous history of MRSA or VRE were excluded. RESULTS: Nineteen thousand three hundred ninety-nine patients were included, with 273 cases of VRE or MRSA. Previous admission within 1 year of current admission had a sensitivity of 56.8% and a specificity of 88.4% for predicting a case of MRSA or VRE. Individually, the sensitivity and specificity for admission within the past year were 50.5% and 88.4%, respectively, for MRSA and 76.9% and 88.4%, respectively, for VRE. CONCLUSIONS: Patients with a previous hospital admission represent a high-risk population for positive culture for VRE and MRSA and may be a group of which active surveillance is indicated.

Adult↗
PubMed2004

Co-carriage rates of vancomycin-resistant Enterococcus and extended-spectrum beta-lactamase-producing bacteria among a cohort of intensive care unit patients: implications for an active surveillance program.

OBJECTIVE: To assess the co-colonization rates of extended-spectrum beta-lactamase (ESBL)-producing bacteria and vancomycin-resistant Enterococcus (VRE) obtained on active surveillance cultures. DESIGN: Prospective cohort study. SETTING: Medical and surgical intensive care units (ICUs) of a tertiary-care hospital. PATIENTS: Patients admitted between September 2001 and November 2002 to the medical and surgical ICUs at the University of Maryland Medical System had active surveillance perirectal cultures performed. Samples were concurrently processed for VRE and ESBL-producing bacteria. RESULTS: Of 1,362 patients who had active surveillance cultures on admission, 136 (10%) were colonized with VRE. Among these, 15 (positive predictive value, 11%) were co-colonized with ESBL. Among the 1,226 who were VRE negative, 1,209 were also ESBL negative (negative predictive value, 99%). Among the 1,362 who had active surveillance cultures on admission, 32 (2%) were colonized with ESBL. Among these, 15 (47%) were co-colonized with VRE. Of the 32 patients colonized with ESBL, 10 (31%) had positive clinical cultures for ESBL on the same hospital admission. For these 10 patients, the surveillance cultures were positive an average of 2.7 days earlier than the clinical cultures. CONCLUSIONS: Patients who are colonized with VRE can also be co-colonized with other antibiotic-resistant bacteria such as ESBL-producing bacteria. Our study is the first to measure co-colonization rates of VRE and ESBL-producing bacteria. Isolating VRE-colonized patients would isolate 47% of the ESBL-colonized patients without the need for further testing. Hence, active surveillance for VRE should also theoretically diminish the amount of patient-to-patient transmission of ESBL-producing bacteria.

Carrier State↗
PubMed2004

Aggressive control measures for resistant Acinetobacter baumannii and the impact on acquisition of methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus in a medical intensive care unit.

The medical ICU implemented aggressive control measures following an outbreak of multidrug-resistant, clonal Acinetobacter baumannii. Multivariable regression analyses comparing acquisition (6 months preceding to 6 months during or following the outbreak) revealed decreased VRE and MRSA acquisition. Aggressive control measures can reduce VRE, and perhaps MRSA, transmission.

Acinetobacter↗
PubMed2004

Preliminary assessment of an automated surveillance system for infection control.

BACKGROUND AND OBJECTIVE: Rapid identification and investigation of potential outbreaks is key to limiting transmission in the healthcare setting. Manual review of laboratory results remains a cumbersome, time-consuming task for infection control practitioners (ICPs). Computer-automated techniques have shown promise for improving the efficiency and accuracy of surveillance. We examined the use of automated control charts, provided by an automated surveillance system, for detection of potential outbreaks. SETTING: A 656-bed academic medical center. METHODS: We retrospectively reviewed 13 months (November 2001 through November 2002) of laboratory-patient data, comparing an automated surveillance application with standard infection control practices. We evaluated positive predictive value, sensitivity, and time required to investigate the alerts. An ICP created 75 control charts. A standardized case investigation form was developed to evaluate each alert for the likelihood of nosocomial transmission based on temporal and spatial overlap and culture results. RESULTS: The 75 control charts were created in 75 minutes and 18 alerts fired above the 3-sigma level. These were independently reviewed by an ICP and associate hospital epidemiologist. The review process required an average of 20 minutes per alert and the kappa score between the reviewers was 0.82. Eleven of the 18 alerts were determined to be potential outbreaks, yielding a positive predictive value of 0.61. Routine surveillance identified 5 of these 11 alerts during this time period. CONCLUSION: Automated surveillance with user-definable control charts for cluster identification was more sensitive than routine methods and is capable of operating with high specificity and positive predictive value in a time-efficient manner.

Cross Infection↗
PubMed2003

Rates of hand disinfection associated with glove use, patient isolation, and changes between exposure to various body sites.

BACKGROUND: Handwashing is the most effective and economic intervention shown to reduce nosocomial infection rates. However, studies have consistently documented low hand disinfection compliance. Literature regarding the roles that concomitant glove use and isolation precautions play in health care worker compliance with hand disinfection is limited. It is unclear whether workers change gloves and disinfect hands adequately between exposures to different body sites/secretions while caring for a patient. METHODS: This was an observational study in which hand disinfection compliance and glove use among workers was evaluated in 2 intensive care units at a tertiary care hospital. RESULTS: Five hundred eighty-nine opportunities for hand disinfection were recorded in 40 hours of observation. Overall compliance was 22.1%. We found a statistically significant, positive association between glove use and subsequent hand disinfection (relative risk [RR], 3.9 [95% CI, 2.5-6.0]; P <.0001). Isolation precautions did not significantly increase disinfection compliance. Only 4.8% (3/63) of workers appropriately complied with disinfection when hands were exposed to multiple body sites/secretions while caring for a patient. CONCLUSIONS: Glove use increases compliance with hand disinfection. Isolation precautions do not increase compliance. Workers do not appropriately comply with disinfection guidelines when attending to multiple body sites/secretions on the same patient. Compliance with hand disinfection remains low.

Attitude of Health Personnel↗
PubMed2003

Epidemiological risk factors for isolation of ceftriaxone-resistant versus -susceptible citrobacter freundii in hospitalized patients.

Antimicrobial resistance is an emerging problem among nosocomial bacteria. Risk factors for the recovery of ceftriaxone-resistant (CRCF) or -susceptible (CSCF) Citrobacter freundii in clinical cultures from hospitalized patients were determined by using a case-case-control study design. CRCF was isolated from 43 patients (case group 1) and CSCF was isolated from 87 patients (case group 2) over a 3-year period. Risk factors for CRCF were exposure to imipenem (odds ratio [OR], 7.5; 95% confidence interval [CI], 1.2 to 45.4), broad-spectrum cephalosporins (OR, 6.9; 95% CI, 1.8 to 26.7), vancomycin (OR, 3.0; 95% CI, 1.2 to 7.4), or piperacillin-tazobactam (OR, 2.6; 95% CI, 1.1 to 6.2), as well as hospital length of stay >or=1 week (OR, 3.6; 95% CI, 1.3 to 10.2) and intensive care unit (ICU) stay (OR, 2.6; 95% CI, 1.1 to 6.2). Risk factors for CSCF were peripheral vascular disease (OR, 23.2; 95% CI, 4.3 to 124.6), AIDS (OR, 9.5; 95% CI, 1.6 to 55.5), cerebrovascular disease (OR, 4.2; 95% CI, 1.6 to 10.8), and ICU stay (OR, 3.1; 95% CI, 1.8 to 5.4).

Case-Control Studies↗
PubMed2003

Fluoroquinolone use and Clostridium difficile-associated diarrhea.

We performed a case-control study to evaluate the association between antibiotic use and Clostridium difficile-associated diarrhea (CDAD), matching for admission unit and time at risk for CDAD. A multivariable regression model showed that treatment with fluoroquinolones (odds ratio 12.7; 95% confidence interval 2.6 to 61.6) was the strongest risk factor for CDAD.

Aged↗
PubMed2002

Control-group selection importance in studies of antimicrobial resistance: examples applied to Pseudomonas aeruginosa, Enterococci, and Escherichia coli.

We aimed to illustrate the importance of control-group selection on the results of risk factor analysis for (1) imipenem-resistant Pseudomonas aeruginosa, (2) vancomycin-resistant enterococci (VRE), and (3) ampicillin-sulbactam-resistant Escherichia coli. Case patients were compared with 2 different control groups: patients with the susceptible form of the organism (type 1), and control patients among whom the case patients arose during the same period as the case patients (type 2). Comparison of case patients who had imipenem-resistant P. aeruginosa with type-1 control patients identified use of imipenem (odds ratio [OR], 27.1) and quinolones (OR, 3.25) as a risk factor for selection of antimicrobial resistance, and comparison of the same case patients with type-2 control patients identified imipenem (OR, 6.34). When case patients with VRE were compared with type-1 and with type-2 control patients, use of vancomycin was identified as a risk factor (OR, 4.38 and 2.77, respectively). Comparison of case patients who had ampicillin-sulbactam-resistant E. coli compared with type-1 control patients identified ampicillin-sulbactam (OR, 2.71) and quinolones (OR, 2.72), and comparison with type-2 control patients identified ampicillin-sulbactam (OR, 1.68). The selection of control patients from the potentially suboptimal control type 1 can falsely identify certain antibiotics and overestimate the OR of the resistance-defining antibiotic.

Anti-Bacterial Agents↗
PubMed2002

Animal antibiotic use has an early but important impact on the emergence of antibiotic resistance in human commensal bacteria.

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.

Agriculture↗
PubMed2002

The effect of active surveillance for vancomycin-resistant enterococci in high-risk units on vancomycin-resistant enterococci incidence hospital-wide.

BACKGROUND: Vancomycin-resistant enterococci (VRE) have become a major cause of nosocomial infections and are now endemic in many geographic areas. The aim of this study was to describe the effect of active surveillance for patients with VRE in high-risk units on the VRE incidence rate hospital-wide. METHODS: We determined 4 time periods based on the intervention of active surveillance: preactive surveillance (period 1), active surveillance (period 2), no active surveillance (period 3), and reinstutition of active surveillance (period 4). VRE incidence rates based on first clinical culture for VRE per 10,000 patient days for each of these periods and incidence rate ratios were then calculated. RESULTS: Active surveillance in high-risk units was associated with a significant reduction in VRE incidence hospital-wide in 2 of the 3 comparisons made. The incidence rate ratio when comparing the first period of active surveillance (period 2) to the preactive surveillance period (period 1) was 0.63 (95% CI, 0.38-1.1); it was 0.36 (95% CI, 0.23-0.55) when comparing the first period of active surveillance (period 2) to the subsequent period (period 3) and 0.68 (95% CI, 0.54-0.85) when comparing the second period of active surveillance (period 4) to the prior period without active surveillance periods. CONCLUSIONS: Active surveillance culturing for VRE in the high risk-units prevented further VRE transmission, as evidenced by a significant increase in hospital-wide incidence rates when active surveillance was discontinued and a significant decrease in incidence rates when it was restarted.

Baltimore↗
PubMed2002

Willingness to pay to avoid sharps-related injuries: a study in injured health care workers.

BACKGROUND: Injuries caused by sharp medical devices are common among health care workers and may result in the transmission of human immunodeficiency virus and hepatitis C virus. OBJECTIVE: The direct medical costs associated with treating these injuries are well characterized but fail to capture the costs of such intangible factors as worker anxiety and distress. The objective of this study was to estimate these intangible costs. SUBJECTS: Subjects included health care workers reporting sharps-related injuries to 2 hospital occupational health services. METHOD: A contingent valuation approach was used to assess willingness to pay to avoid sharps-related injuries among recently injured health care workers. Workers were presented with the option of paying out of pocket for a hypothetical injury-prevention device. The median amount of money subjects were willing to pay was estimated with logistic regression, and multivariable regression was performed to assess confounding by worker characteristics and circumstances surrounding injuries. RESULTS: Study interviews were conducted for 116 subjects; median time from injury to interview was 3 days (range, 0-15). Most subjects were women (73%), and most were nurses (44%) or trainees (32%). The crude median amount subjects were willing to pay to avert injury was $850 (US); when adjusted for patient risk status (human immunodeficiency virus and hepatitis C virus status), and working with an uncooperative patient at the time of injury, median amount increased to $1270. CONCLUSION: The high median amount subjects were willing to pay to avoid a sharps-related injury suggests that the costs of "intangible" aspects of worker injury, such as anxiety and distress, may equal costs associated with the medical evaluation of these injuries. These costs should be incorporated in economic analyses of sharps-injury prevention.

Adult↗
PubMed2002

Risk factors for piperacillin-tazobactam-resistant Pseudomonas aeruginosa among hospitalized patients.

Antimicrobial resistance is an emerging problem with Pseudomonas aeruginosa. This study determined risk factors for the recovery of piperacillin-tazobactam-resistant P. aeruginosa from clinical cultures from hospitalized patients. A case-control study design was used to compare two groups of case patients with control patients. The first group of case patients was defined by nosocomial isolation of piperacillin-tazobactam-resistant P. aeruginosa, and the second group of cases yielded piperacillin-tazobactam-susceptible P. aeruginosa. Controls were selected in a 6:1 ratio from the same medical or surgical services among which piperacillin-tazobactam-resistant P. aeruginosa arose in patients. Risk factors analyzed included antimicrobial drug exposure, comorbid conditions, and demographics. Bivariate and multivariable analyses were performed. Piperacillin-tazobactam-resistant P. aeruginosa was isolated from 179 patients, and piperacillin-tazobactam-susceptible P. aeruginosa was isolated from 624 patients over a 2.5-year period. Piperacillin-tazobactam (odds ratio [OR] = 6.82; 95% confidence interval [CI], 4.56 to 10.21), imipenem (OR = 2.42; 95% CI, 1.19 to 4.94), aminoglycosides (OR = 2.18; 95% CI, 1.44 to 3.28), vancomycin (OR = 1.87; 95% CI, 1.21 to 2.89), and broad-spectrum cephalosporins (OR = 2.38; 95% CI, 1.45 to 3.88) were the antibiotics associated with the isolation of piperacillin-tazobactam-resistant P. aeruginosa. Exposure to vancomycin (OR = 1.53; 95% CI, 1.13 to 2.06) or ampicillin-sulbactam (OR = 2.28; 95% CI, 1.62 to 3.21) was associated with recovery of piperacillin-tazobactam-susceptible P. aeruginosa. In this study, antibiotics associated with piperacillin-tazobactam-susceptible P. aeruginosa were different from antibiotics associated with piperacillin-tazobactam-resistant P. aeruginosa. Piperacillin-tazobactam was a strong risk factor for piperacillin-tazobactam-resistant P. aeruginosa. Our results suggest that the nosocomial isolation of piperacillin-tazobactam-resistant P. aeruginosa may be affected by multiple antibiotics.

Adult↗
PubMed2001

Risk factors for imipenem-resistant Pseudomonas aeruginosa among hospitalized patients.

Risk factors for the nosocomial recovery of imipenem-resistant Pseudomonas aeruginosa (IRPA) were determined. A case-control study design was used for the comparison of 2 groups of case patients with control patients. The first group of case patients had nosocomial isolation of IRPA, and the second group had imipenem-susceptible P. aeruginosa (ISPA). Control patients were selected from the same medical or surgical services from which case patients were receiving care when isolation of IRPA occurred. Risk factors analyzed included antimicrobials used, comorbid conditions, and demographic variables. IRPA was recovered from 120 patients, and ISPA from 662 patients. Imipenem (odds ratio [OR], 4.96), piperacillin-tazobactam (OR, 2.39), vancomycin (OR, 1.80), and aminoglycosides (OR, 2.19) were associated with isolation of IRPA. Vancomycin (OR, 1.64), ampicillin-sulbactam (OR, 2.00), and second-generation cephalosporins (OR, 2.00) were associated with isolation of ISPA. Antibiotics associated with ISPA are different from antibiotics associated with IRPA. The OR for imipenem as a risk factor for IRPA is less than that reported from studies in which control group selection was suboptimal.

Anti-Bacterial Agents↗