Mary T. Bessesen

The human nasal microbiota and Staphylococcus aureus carriage.

Background Colonization of humans with Staphylococcus aureus is a critical prerequisite of subsequent clinical infection of the skin, blood, lung, heart and other deep tissues. S. aureus persistently or intermittently colonizes the nares of ∼50% of healthy adults, whereas ∼50% of the general population is rarely or never colonized by this pathogen. Because microbial consortia within the nasal cavity may be an important determinant of S. aureus colonization we determined the composition and dynamics of the nasal microbiota and correlated specific microorganisms with S. aureus colonization. Methodology/Principal Findings Nasal specimens were collected longitudinally from five healthy adults and a cross-section of hospitalized patients (26 S. aureus carriers and 16 non-carriers). Culture-independent analysis of 16S rRNA sequences revealed that the nasal microbiota of healthy subjects consists primarily of members of the phylum Actinobacteria (e.g., Propionibacterium spp. and Corynebacterium spp.), with proportionally less representation of other phyla, including Firmicutes (e.g., Staphylococcus spp.) and Proteobacteria (e.g. Enterobacter spp). In contrast, inpatient nasal microbiotas were enriched in S. aureus or Staphylococcus epidermidis and diminished in several actinobacterial groups, most notably Propionibacterium acnes. Moreover, within the inpatient population S. aureus colonization was negatively correlated with the abundances of several microbial groups, including S. epidermidis (p = 0.004). Conclusions/Significance The nares environment is colonized by a temporally stable microbiota that is distinct from other regions of the integument. Negative association between S. aureus, S. epidermidis, and other groups suggests microbial competition during colonization of the nares, a finding that could be exploited to limit S. aureus colonization.

Reduction in central line-associated bloodstream infections by implementation of a postinsertion care bundle

BACKGROUND Central line-associated bloodstream infections (CLABSIs) cause substantial morbidity and incur excess costs. The use of a central line insertion bundle has been shown to reduce the incidence of CLABSI. Postinsertion care has been included in some studies of CLABSI, but this has not been studied independently of other interventions. METHODS Surveillance for CLABSI was conducted by trained infection preventionists using National Health Safety Network case definitions and device-day measurement methods. During the intervention period, nursing staff used a postinsertion care bundle consisting of daily inspection of the insertion site; site care if the dressing was wet, soiled, or had not been changed for 7 days; documentation of ongoing need for the catheter; proper application of a chlorohexidine gluconate-impregnated sponge at the insertion site; performance of hand hygiene before handling the intravenous system; and application of an alcohol scrub to the infusion hub for 15 seconds before each entry. RESULTS During the preintervention period, there were 4415 documented catheter-days and 25 CLABSIs, for an incidence density of 5.7 CLABSIs per 1000 catheter-days. After implementation of the interventions, there were 2825 catheter-days and 3 CLABSIs, for an incidence density of 1.1 per 1000 catheter-days. The relative risk for a CLABSI occurring during the postintervention period compared with the preintervention period was 0.19 (95% confidence interval, 0.06-0.63; P = .004). CONCLUSION This study demonstrates that implementation of a central venous catheter postinsertion care bundle was associated with a significant reduction in CLABSI in a setting where compliance with the central line insertion bundle was already high.

Epidemiology of Healthcare‐Associated Bloodstream Infection Caused by USA300 Strains of Methicillin‐Resistant Staphylococcus aureus in 3 Affiliated Hospitals

OBJECTIVE To describe the epidemiology of bloodstream infection caused by USA300 strains of methicillin-resistant Staphylococcus aureus (MRSA), which are traditionally associated with cases of community-acquired infection, in the healthcare setting. DESIGN Retrospective cohort study. SETTING Three academically affiliated hospitals in Denver, Colorado. METHODS Review of cases of S. aureus bloodstream infection during the period from 2003 through 2007. Polymerase chain reaction was used to identify MRSA USA300 isolates. RESULTS A total of 330 cases of MRSA bloodstream infection occurred during the study period, of which 286 (87%) were healthcare-associated. The rates of methicillin resistance among the S. aureus isolates recovered did not vary during the study period and were similar among the 3 hospitals. However, the percentages of cases of healthcare-associated MRSA bloodstream infection due to USA300 strains varied substantially among the 3 hospitals: 62%, 19%, and 36% (P<.001) for community-onset cases and 33%, 3%, and 33% (P=.005) for hospital-onset cases, in hospitals A, B, and C, respectively. In addition, the number of cases of healthcare-associated MRSA bloodstream infection caused by USA300 strains increased during the study period at 2 of the 3 hospitals. At each hospital, USA300 strains were most common among cases of community-associated infection and were least common among cases of hospital-onset infection. Admission to hospital A (a safety-net hospital), injection drug use, and human immunodeficiency virus infection were independent risk factors for healthcare-associated MRSA bloodstream infection due to USA300 strains. CONCLUSIONS The prevalence of USA300 strains among cases of healthcare-associated MRSA bloodstream infection varied dramatically among geographically clustered hospitals. USA300 strains are replacing traditional healthcare-related strains of MRSA in some healthcare settings. Our data suggest that the prevalence of USA300 strains in the community is the dominant factor affecting the prevalence of this strain type in the healthcare setting.

Using human factors engineering to improve the effectiveness of infection prevention and control.

Human factors engineering is a discipline that studies the capabilities and limitations of humans and the design of devices and systems for improved performance. The principles of human factors engineering can be applied to infection prevention and control to study the interaction between the healthcare worker and the system that he or she is working with, including the use of devices, the built environment, and the demands and complexities of patient care. Some key challenges in infection prevention, such as delayed feedback to healthcare workers, high cognitive workload, and poor ergonomic design, are explained, as is how human factors engineering can be used for improvement and increased compliance with practices to prevent hospital-acquired infections.

MRSA colonization and the nasal microbiome in adults at high risk of colonization and infection.

OBJECTIVE The objective of this study was to define the nasal microbiome of hospital inpatients who are persistently colonized with methicillin-resistant Staphylococcus aureus (MRSA) compared with matched, non-colonized controls. METHODS Twenty-six persistently MRSA-colonized subjects and 26 matched non-colonized controls were selected from the screening records of the infection control program at the Department of the Veteran Affairs Eastern Colorado Health Care System (VA-ECHCS). The nasal microbiotas were analyzed with PCR amplification and sequencing of the 16S ribosomal RNA (rRNA) gene. Comparison of all variables across the groups was performed using stratified logistic regression to account for the one-to-one matching. Canonical discriminant analysis was performed to assess differences in bacterial community across the two groups. Competing organisms were cocultured with MRSA in vitro. RESULTS There was a negative association between MRSA colonization and colonization with Streptococcus spp. At the species level, multivariate analysis demonstrated a statistically significant negative association between colonization with Streptococcus mitis or Lactobacillus gasseri and MRSA. Coculture experiments revealed in vitro competition between S. mitis and all of the 22 MRSA strains isolated from subjects. Competition was blocked by addition of catalase to the media. Persistently colonized subjects had lesser microbial diversity than the non-colonized controls. CONCLUSION In a high-risk inpatient setting, bacterial competition in the nasal niche protects some patients from MRSA colonization.

HIV Infection and Osteoporosis: Pathophysiology, Diagnosis, and Treatment Options

As the population with HIV continues to age, specialists in HIV care are increasingly encountering chronic health conditions, which now include osteoporosis, osteopenia, and fragility fractures. The pathophysiology of the bone effects of HIV infection is complex and includes traditional risk factors for bone loss as well as specific effects due to the virus itself, chronic inflammation, and HAART. Examining risk factors for low bone density and screening of certain patients is suggested, and consideration should be given to treatment for those considered high risk for fracture.

Comparison of control strategies for methicillin-resistant Staphylococcus aureus.

BACKGROUND Screening patients for methicillin-resistant Staphylococcus aureus (MRSA) colonization and contact precautions for colonized patients has been recommended when other control measures have been ineffective. METHODS We compared MRSA transmission rates following implementation of a bundle of control measures that included institutional culture change, surveillance for MRSA infection and transmission, and active screening for colonization in 2 similar Veterans Health Administration hospitals. One hospital employed contact precautions as defined by the Centers for Disease Control and Prevention, and the other hospital modified contact precautions, requiring only the use of gloves. RESULTS During the 4-year study period, there were 1.58 MRSA transmissions per 1,000 patient-days at hospital A and 1.56 MRSA transmissions per 1,000 patient-days at hospital B (P = .98). Both hospitals experienced significant reductions in MRSA health care-associated infections (HAI). There was no difference between hospital A and hospital B in incidence of MRSA HAIs or MRSA surgical site infections. Annual acquisition costs for cover gowns were

Antimicrobial Stewardship Programs: Comparison of a Program with Infectious Diseases Pharmacist Support to a Program with a Geographic Pharmacist Staffing Model

183,609 at hospital A and

The Respiratory Protection Effectiveness Clinical Trial (ResPECT): a cluster-randomized comparison of respirator and medical mask effectiveness against respiratory infections in healthcare personnel

25,812 at hospital B. CONCLUSION Significant reductions in MRSA HAI were associated with implementation of the MRSA control bundle. The bundle that included full contact precautions for colonized patients was no more effective in prevention of MRSA transmissions than a similar bundle that omitted the use of cover gowns.

Risk and outcomes of methicillin-resistant Staphylococcus aureus (MRSA) bacteremia among patients admitted with and without MRSA nares colonization

Background Stewardship of antimicrobial agents is an essential function of hospital pharmacies. The ideal pharmacist staffing model for antimicrobial stewardship programs is not known. Objective To inform staffing decisions for antimicrobial stewardship teams, we aimed to compare an antimicrobial stewardship program with a dedicated Infectious Diseases (ID) pharmacist (Dedicated ID Pharmacist Hospital) to a program relying on ward pharmacists for stewardship activities (Geographic Model Hospital). Methods We reviewed a randomly selected sample of 290 cases of inpatient parenteral antibiotic use. The electronic medical record was reviewed for compliance with indicators of appropriate antimicrobial stewardship. Results At the hospital staffed by a dedicated ID pharmacist, 96.8% of patients received initial antimicrobial therapy that adhered to local treatment guidelines compared to 87% of patients at the hospital that assigned antimicrobial stewardship duties to ward pharmacists (P < .002). Therapy was modified within 24 hours of availability of laboratory data in 86.7% of cases at the Dedicated ID Pharmacist Hospital versus 72.6% of cases at the Geographic Model Hospital (P < .03). When a patients illness was determined not to be caused by a bacterial infection, antibiotics were discontinued in 78.0% of cases at the Dedicated ID Pharmacist Hospital and in 33.3% of cases at the Geographic Model Hospital (P < .0002). Conclusion An antimicrobial stewardship program with a dedicated ID pharmacist was associated with greater adherence to recommended antimicrobial therapy practices when compared to a stewardship program that relied on ward pharmacists.