Treatment effectiveness of antibiotic therapy in Veterans with multidrug-resistant Acinetobacter spp. bacteremia

Objective

To describe antimicrobial therapy used for multidrug-resistant (MDR) Acinetobacter spp. bacteremia in Veterans and impacts on mortality.

Methods

This was a retrospective cohort study of hospitalized Veterans Affairs patients from 2012 to 2018 with a positive MDR Acinetobacter spp. blood culture who received antimicrobial treatment 2 days prior to through 5 days after the culture date. Only the first culture per patient was used. The association between treatment and patient characteristics was assessed using bivariate analyses. Multivariable logistic regression models examined the relationship between antibiotic regimen and in-hospital, 30-day, and 1-year mortality. Generalized linear models were used to assess cost outcomes.

Results

MDR Acinetobacter spp. was identified in 184 patients. Most cultures identified were Acinetobacter baumannii (90%), 3% were Acinetobacter lwoffii, and 7% were other Acinetobacter species. Penicillins-β-lactamase inhibitor combinations (51.1%) and carbapenems (51.6%)-were the most prescribed antibiotics. In unadjusted analysis, extended spectrum cephalosporins and penicillins-β-lactamase inhibitor combinations-were associated with a decreased odds of 30-day mortality but were insignificant after adjustment (adjusted odds ratio (aOR) = 0.47, 95% CI, 0.21-1.05, aOR = 0.75, 95% CI, 0.37-1.53). There was no association between combination therapy vs monotherapy and 30-day mortality (aOR = 1.55, 95% CI, 0.72-3.32).

Conclusion

In hospitalized Veterans with MDR Acinetobacter spp., none of the treatments were shown to be associated with in-hospital, 30-day, and 1-year mortality. Combination therapy was not associated with decreased mortality for MDR Acinetobacter spp. bacteremia.

Antimicrobial stewardship strategy implementation and impact in acute care spinal cord injury and disorder units

CONTEXT

Antimicrobial Stewardship Programs (ASPs) are crucial to optimizing antibiotic use. ASPs are implemented in the Veterans Health Administration (VAs), but they do not target the needs of populations at high risk for resistant infections, such as spinal cord injury and disorder (SCI/D).

OBJECTIVE

The goal of this study was to assess key ASP leader and SCI/D clinicians' perceived level of implementation and impact of 33 Antimicrobial Stewardship (AS) strategies.

METHOD

SCI/D clinicians and ASP leaders across 24 VA facilities with SCI/D units were surveyed. Participants rated their perceived level of impact ("high", "mild", "low") and perceived level of implementation ("not", "partially", "fully") for 33 AS strategies in SCI/D units in VAs. Strategies were grouped into core elements which they support. We conducted a Fisher's exact test to assess differences between respondent perceptions based on role (SCI/D clinicians versus ASP leaders).

RESULTS

AS strategy implementation varied across VA facilities. Of the AS strategies, pre-authorization was perceived to be highly impactful (78%) and fully implemented (82%). SCI/D clinicians and ASP leaders rated AS strategies differently such that SCI/D clinicians were less aware of implementation of AS strategies related to reporting requirements; further, SCI/D clinicians rated strategies which guide treatment duration and which limit C. difficile antibiotic exposure as more impactful than ASP leaders. Ratings for facility-wide and SCI/D unit ratings did not significantly differ for impact or implementation.

CONCLUSION

Implementation practices varied across VA facilities. Future work should implement highly impactful AS strategies according to facility and unit needs.

A qualitative exploration of dentists' opioid prescribing decisions within U.S. veterans affairs facilities

ABSTRACT

The U.S. Department of Veterans Affairs (VA) is the largest integrated healthcare system in the United States and provides dental care to approximately one-half million veterans annually. In response to the opioid crisis, the VA released several opioid risk mitigation strategies. Although opioid prescribing by VA dentists has decreased on the whole, the implementation experiences at the level of dentists remains unclear. Our objective was to explore the barriers and facilitators that affect opioid decision making for management of acute dental pain among VA dentists. Dentists practicing in the VA facilities with the highest and lowest volume of opioid prescriptions were recruited. Standardized qualitative interviews by telephone followed a semistructured guide designed around the Capability (C), Opportunity (O), Motivation (M), and Behaviour (B) model. Audio recordings were transcribed and independently double-coded using NVivo to identify potential targets for future guideline-based opioid interventions. Of 395 eligible general and specialty dentists, 90 (24.8%) completed an interview representing 33 VA facilities. Opportunities for prescribing opioids included 1) completion of dental procedures associated with acute dental pain, 2) caring for patients who presented with existing dental pain, and 3) responding to patient opioid requests. Capabilities included using resources (eg, electronic medical records), clinical judgement (eg, evaluation of medical history including medication use), communication skills, and ability to screen for opioid misuse. Motivation themes focused on alleviating patients' acute dental pain. Barriers and facilitators of opioid prescribing varied across facilities. The results can offer intervention targets for continued opioid risk mitigation efforts.

Infectious Disease Consults of Pseudomonas aeruginosa Bloodstream Infection and Impact on Health Outcomes

Background

Infectious diseases (ID) consultation improves health outcomes for certain infections but has not been well described for Pseudomonas aeruginosa (PA) blood stream infection (BSI). Therefore, the goal of this study was to examine ID consultation of inpatients with PA BSI and factors impacting outcomes.

Methods

This was a retrospective cohort study from January 1, 2012 - December 31, 2018 of adult hospitalized Veterans with PA BSI and antibiotic treatment 2 days before through 5 days after the culture date. Multidrug resistant (MDR) cultures were defined as resistance to at least 1 agent in ≥ 3 antimicrobial categories tested. Multivariable logistic regression models were fit to assess the impact of ID consults and adequate treatment on mortality.

Results

3,256 patients had PA BSI, of which 367 (11.3%) were multi-drug resistant (MDR). Most were male (97.5%), over 65 years old (71.2%), and white (70.9%). Nearly one-fourth (n = 784, 23.3%) died during hospitalization and 870 (25.8%) died within 30-days of their culture. Adjusted models showed ID consultation was associated with decreased in-hospital (odds ratio (OR) = 0.47, 95% CI: 0.39-0.56) and 30-day mortality (OR = 0.51, 95% CI: 0.42-0.62).

Conclusions

Consultation with ID physicians improves clinical outcomes such as in-hospital and 30-day mortality for patients with PA BSI. ID consultation provides value and should be considered for patients with PA BSI.

Opioid Prescribing by Dentists in the Veterans Health Administration

INTRODUCTION

Nonopioid analgesics are more effective for most oral pain, but data suggest that dental prescribing of opioids is excessive. This study evaluates the extent to which opioids exceed recommendations and the characteristics associated with opioid overprescribing by Veterans Health Administration dentists.

METHODS

This was a national cross-sectional study of Veterans' dental visits from 2015 to 2018. Overprescribing was defined per national guidelines as >120 morphine milligram equivalents (primary outcome). The association of dental visit and patient demographic and medical characteristics was modeled with overprescribing (defined as >120 morphine milligram equivalents) using Poisson regression with clustering by facility and patient. A secondary analysis assessed opioid prescriptions >3 days' supply. The dates of analysis were January 2020‒May 2021.

RESULTS

Of the 196,595 visits, 28.7% exceeded 120 morphine milligram equivalents. Friday visits and people with chronic oral pain or substance misuse were associated with a higher prevalence of overprescribing. Women, older Veterans, and Black and Latinx Veterans were less likely to be overprescribed than men, younger Veterans, and White Veterans, respectively. Routine dental visits had a higher prevalence of opioid overprescribing than invasive visits. Opioid overprescribing decreased over time. White Veterans were more likely to receive oxycodone and hydrocodone, whereas people of Black race and Latinx ethnicity were more likely to receive codeine and tramadol. In the secondary analysis, 68.5% of opioid prescriptions exceeded a 3-day supply.

CONCLUSIONS

Nearly 1 in 3 opioids prescribed by Veterans Health Administration dentists exceed guidelines. Prescribing higher potency and quantities of opioids, especially on Fridays and to certain demographic groups, should be addressed as part of dental opioid stewardship programs.

A qualitative approach to examining antimicrobial prescribing in the outpatient dental setting

OBJECTIVE

To understand barriers and facilitators to evidence-based prescribing of antibiotics in the outpatient dental setting.

DESIGN

Semistructured interviews.

SETTING

Outpatient dental setting.

PARTICIPANTS

Dentists from 40 Veterans' Health Administration (VA) facilities across the United States.

METHODS

Dentists were identified based on their prescribing patterns and were recruited to participate in a semistructured interview on perceptions toward prescribing. All interviews were recorded, transcribed, and double-coded for analysis, with high reliability between coders. We identified general trends using the theoretical domains framework and mapped overarching themes onto the behavior change wheel to identify prospective interventions that improve evidence-based prescribing.

RESULTS

In total, 90 dentists participated in our study. The following barriers and facilitators to evidence-based prescribing emerged as impacts on a dentist's decision making on prescribing an antibiotic: access to resources, social influence of peers and other care providers, clinical judgment, beliefs about consequences, local features of the clinic setting, and beliefs about capabilities.

CONCLUSIONS

Findings from this work reveal the need to increase awareness of up-to-date antibiotic prescribing behaviors in dentistry and may inform the best antimicrobial stewardship interventions to support dentists' ongoing professional development and improve evidence-based prescribing.

Epidemiology and outcomes associated with carbapenem-resistant Acinetobacter baumannii and carbapenem-resistant Pseudomonas aeruginosa: a retrospective cohort study

Background

Carbapenem-resistant Acinetobacter baumannii (CRAB) and carbapenem-resistant Pseudomonas aeruginosa (CRPA) are a growing threat. The objective of this study was to describe CRAB and CRPA epidemiology and identify factors associated with mortality and length of stay (LOS) post-culture.

Methods

This was a national retrospective cohort study of Veterans with CRAB or CRPA positive cultures from 2013 to 2018, conducted at Hines Veterans Affairs Hospital. Carbapenem resistance was defined as non-susceptibility to imipenem, meropenem and/or doripenem. Multivariable cluster adjusted regression models were fit to assess the association of post-culture LOS among inpatient and long-term care (LTC) and to identify factors associated with 90-day and 365-day mortality after positive CRAB and CRPA cultures.

Results

CRAB and CRPA were identified in 1,048 and 8,204 unique patients respectively, with 90-day mortality rates of 30.3% and 24.5% and inpatient post-LOS of 26 and 27 days. Positive blood cultures were associated with an increased odds of 90-day mortality compared to urine cultures in patients with CRAB (OR 6.98, 95% CI 3.55–13.73) and CRPA (OR 2.82, 95% CI 2.04–3.90). In patients with CRAB and CRPA blood cultures, higher Charlson score was associated with increased odds of 90-day mortality. In CRAB and CRPA, among patients from inpatient care settings, blood cultures were associated with a decreased LOS compared to urine cultures.

Conclusions

Positive blood cultures and more comorbidities were associated with higher odds for mortality in patients with CRAB and CRPA. Recognizing these factors would encourage clinicians to treat these patients in a timely manner to improve outcomes of patients infected with these organisms.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07436-w.

Opportunities for penicillin allergy evaluation in dental clinics

OBJECTIVE

To evaluate opportunities for assessing penicillin allergies among patients presenting to dental clinics.

DESIGN

Retrospective cross-sectional study.

SETTING

VA dental clinics.

PATIENTS

Adult patients with a documented penicillin allergy who received an antibiotic from a dentist between January 1, 2015, and December 31, 2018, were included.

METHODS

Chart reviews were completed on random samples of 100 patients who received a noncephalosporin antibiotic and 200 patients who received a cephalosporin. Each allergy was categorized by severity. These categories were used to determine patient eligibility for 3 testing groups based on peer-reviewed algorithms: (1) no testing, (2) skin testing, and (3) oral test-dose challenge. Descriptive and bivariate statistics were used to compare facility and patient demographics first between true penicillin allergy, pseudo penicillin allergy, and missing allergy documentation, and between those who received a cephalosporin and those who did not at the dental visit.

RESULTS

Overall, 19% lacked documentation of the nature of allergic reaction, 53% were eligible for skin testing, 27% were eligible for an oral test-dose challenge, and 1% were contraindicated from testing. Male patients and African American patients were less likely to receive a cephalosporin.

CONCLUSIONS

Most penicillin-allergic patients in the VA receiving an antibiotic from a dentist are eligible for penicillin skin testing or an oral penicillin challenge. Further research is needed to understand the role of dentists and dental clinics in assessing penicillin allergies.

Treatment of extensively-drug resistant (XDR) Acinetobacter and impact on clinical outcomes in U.S. veterans affairs (VA) medical centers

BACKGROUND

Guidelines for treatment of resistant Acinetobacter baumannii (AB) are limited, leaving a knowledge gap in best practices for treatment. This study described treatments and outcomes of extensively-drug resistant (XDR) AB.

METHODS

Retrospective cohort study including patients with XDRAB (non-susceptible to at least 1 agent in all but 2 or fewer classes) and antibiotic treatment between 2012 and 2018 at Veterans Affairs Medical Centers. Descriptive statistics summarized antibiotics; propensity score adjusted regression models were fit to compare outcomes.

RESULTS

Two hundred and seventy-six patients with 439 XDRAB cultures and Gram-negative targeted antibiotic treatment were included. One hundred and eighteen (43%) patients received monotherapy while 158 (57%) received combination therapy, most commonly including a carbapenem (n = 106, 67%) and polymyxin (n = 66, 42%). One hundred and eighty-four (67%) patients received inadequate treatment. In adjusted models, combination therapy did not decrease the odds of in-hospital (aOR 1.24, 95%CI 0.60-2.59) or 30-day (aOR 1.43, 95%CI 0.86-2.38) mortality, or median postculture length of stay (aIRR 1.11, 95%CI 0.86-1.43). Likewise, receipt of inadequate treatment was not associated with poorer outcomes.

CONCLUSIONS

In this national cohort of patients with XDRAB, neither combination therapy nor receipt of adequate treatment improved outcomes. Further research is needed on optimal management of this difficult-to-treat pathogen with few effective antibiotic options.

Evaluation of carbapenem-resistant Enterobacteriaceae (CRE) guideline implementation in the Veterans Affairs Medical Centers using the consolidated framework for implementation research

Background

Infections caused by carbapenem-resistant Enterobacteriaceae (CRE) and carbapenemase-producing (CP) CRE are difficult to treat, resulting in high mortality in healthcare settings every year. The Veterans Health Administration (VHA) disseminated guidelines in 2015 and an updated directive in 2017 for control of CRE focused on laboratory testing, prevention, and management. The Consolidated Framework for Implementation Research (CFIR) framework was used to analyze qualitative interview data to identify contextual factors and best practices influencing implementation of the 2015 guidelines/2017 directive in VA Medical Centers (VAMCs). The overall goals were to determine CFIR constructs to target to improve CRE guideline/directive implementation and understand how CFIR, as a multi-level conceptual model, can be used to inform guideline implementation.

Methods

Semi-structured interviews were conducted at 29 VAMCs with staff involved in implementing CRE guidelines at their facility. Survey and VHA administrative data were used to identify geographically representative large and small VAMCs with varying levels of CRE incidence. Interviews addressed perceptions of guideline dissemination, laboratory testing, staff attitudes and training, patient education, and technology support. Participant responses were coded using a consensus-based mixed deductive-inductive approach guided by CFIR. A quantitative analysis comparing qualitative CFIR constructs and emergent codes to sites actively screening for CRE (vs. non-screening) and any (vs. no) CRE-positive cultures was conducted using Fisher’s exact test.

Results

Forty-three semi-structured interviews were conducted between October 2017 and August 2018 with laboratory staff (47%), Multi-Drug-Resistant Organism Program Coordinators (MPCs, 35%), infection preventionists (12%), and physicians (6%). Participants requested more standardized tools to promote effective communication (e.g., electronic screening). Participants also indicated that CRE-specific educational materials were needed for staff, patient, and family members. Quantitative analysis identified CRE screening or presence of CRE as being significantly associated with the following qualitative CFIR constructs: leadership engagement, relative priority, available resources, team communication, and access to knowledge and information.

Conclusions

Effective CRE identification, prevention, and treatment require ongoing collaboration between clinical, microbiology, infection prevention, antimicrobial stewardship, and infectious diseases specialists. Our results emphasize the importance of leadership’s role in promoting positive facility culture, including access to resources, improving communication, and facilitating successful implementation of the CRE guidelines.

Supplementary Information

The online version contains supplementary material available at 10.1186/s43058-021-00170-5.

516. Social Network Analysis to Study MDRO Transmission in VA Community Living Centers and Spinal Cord Injury Units

Background

Residents of VA Community Living Centers (CLC) and Spinal Cord Injury units (SCI) are commonly colonized or infected with multidrug-resistant organisms (MDROs). The mechanisms by which MDROs are spread between residents in CLC/SCI settings remain poorly understood. Our objective was to develop methods to better understand how MDROs are spread in VA CLCs/SCIs.

Methods

Preliminary data from two of the four VA medical centers participating in an ongoing study are included in these analyses. A structured sociometric survey was employed to collect data on interactions between residents, staff and environmental surfaces in study units. UCINET was used to construct a sociogram and calculate network characteristics (density, centrality) using responses to the surveys administered in one of the participating facilities.

Results

A total of 136 surveys were completed by 49 staff and 45 residents at the two VA sites. Staff reported more interactions with residents than with other staff. Residents reported more interactions with staff than with other residents, the latter tending to only occur during group activities. Sociograms generated from preliminary surveys collected at one site suggest a four-core-person social network pattern connecting two staff with two specific residents and showed that the dining room was the group setting most frequently visited by residents. Mobile computers, blood pressure cuffs/thermometers and glucometers were the equipment used most heavily during resident care activities (figure). Challenges in identifying contact patterns include recall bias and inability of some residents to identify names of individuals with whom they interacted. Residents were still able to reliably identify staff roles.

Conclusion

This preliminary work shows heterogeneous contact patterns between persons and surfaces in VA CLCs/SCIs. Characterizing this heterogeneity and its influence on MDRO spread via this type of social network analysis is feasible in the VA CLC/SCI setting, albeit with some limitations. Next steps in our studies include adding data from two additional sites and using observation techniques supplemented with microbiological sampling of targeted environmental surfaces to further understand potential transmission patterns.

Disclosures

All authors: No reported disclosures.

525. Evaluation of Implementation of Guidelines for Carbapenem-resistant Enterobacteriaceae (CRE) Prevention Using the Consolidated Framework for Implementation Research (CFIR)

Background

Infections caused by carbapenem-resistant Enterobacteriaceae (CRE) and carbapenemase-producing (CP) CRE are difficult to treat, resulting in a high mortality annually. In 2017, VA released guidelines for CRE/CP-CRE laboratory testing, prevention, and management. We used the Consolidated Framework for Implementation Research (CFIR) to understand factors influencing implementation of the CRE guideline at VA Medical Centers (VAMCs).

Methods

Between 9/17–8/18, 43 semi-structured interviews were conducted with Multi-Drug Resistant Organism Program Coordinators, laboratorians, physicians and infection preventionists from 29 geographically representative VAMCs of varying size and CP-CRE burden. Interviews addressed perceptions of guideline dissemination, laboratory testing, training, patient education, and IT support (e.g., CRE/CP-CRE flag, lab report and template). We analyzed transcripts using a consensus-based mixed deductive-inductive coding approach to identify CFIR constructs, best practices, recommendations/feedback and implementation challenges.

Results

95% of interviewees reported using VA CRE/CP-CRE guidelines, most (79%) with high confidence. Respondent comments (n = 798) were coded using CFIR constructs [Inner Setting (e.g., resources), (48%); Process (e.g., planning), (23%); Intervention Characteristics (e.g., VA guidelines) (17%); Outer Setting (e.g., patient needs) (6%); Characteristics of Individuals (e.g., self-efficacy) (6%)]. Interviewees also described Best Practices (15%) and Feedback/Recommendations (12%) including the need for improved lab testing/reporting, communication, contact isolation, staff training, patient education and cost.

Conclusion

Our results suggest sustained improvement in multiple areas to facilitate guideline implementation to identify, prevent, and manage CRE/CP-CRE are needed. This is critical because CRE/CP-CRE incidence and mortality rates are projected to increase.

Disclosures

All authors: No reported disclosures.

Stitching techniques for measuring X-ray synchrotron mirror topography

Optical metrology and polishing techniques are continuously evolving to satisfy the increasingly stringent specifications required for X-ray optical components for synchrotron and free-electron laser light source beamlines. For both spherical and aspherical geometries, the most demanding applications may have target residual figure errors close to 1 nm. To achieve such specifications and maintain them in the optomechanical mount, it is critical to develop methods capable of measuring the topography of the optical surface over the clear aperture of the mirror. The European Synchrotron Radiation Facility optical metrology laboratory has developed a stitching tool initially aimed at measuring long flat mirrors up to 1 m long with a Fizeau interferometer. The system is routinely used providing 2D maps of the optical surface. The instrument capabilities have been extended to characterize moderately curved optics using a transmission flat element, and results obtained on a high quality spherical mirror with 120 m of radius of curvature are presented. As a novel approach of stitching application, the technique has been used to improve the measurement accuracy of the Fizeau interferometer when measuring short plane mirrors. Acquisition of 2D topographies on a short plane mirror by micro-stitching interferometry is also presented and discussed.

Managing severe obesity: understanding and improving treatment adherence in bariatric surgery

Severe obesity (body mass index ≥40 kg/m²) is a chronic disease that is associated with significantly increased risk of serious and chronic health problems as well as impaired quality of life. For those with severe obesity, bariatric surgery is the most effective treatment for significant and long-term weight loss and resolution of comorbid medical conditions, particularly diabetes. Long-term success is thought to depend to some degree on the patient's ability to adhere to a complex set of behaviors, including regular attendance at follow up appointments and following stringent dietary, exercise, and vitamin recommendations. Here, we summarize the current research on behavioral adherence in patients with severe obesity presenting for bariatric surgery and we highlight challenges and make recommendations for improved self-management before and after surgery.

What do we know about mobile applications for diabetes self-management? A review of reviews

Diabetes is a chronic illness with significant health consequences, especially for those who are unable to adhere to the complex treatment regimen. Self-management tasks such as regular medication and insulin use, frequent blood sugar checks, strict diet management, and consistent exercise can be quite challenging. Mobile technologies, specifically mobile applications (apps), present a unique opportunity to help patients improve adherence to these behaviors. The availability of commercial diabetes self-management apps is increasing rapidly, making it difficult for patients and providers to stay informed about app options. A number of reviews have described commercial app technology and use for patients with diabetes. The aims of this article are to summarize the results and themes of those reviews, to review outcomes of apps described in the research literature, and to identify areas for further consideration in the use of mobile apps for diabetes self-management.

Stitching methods at the European Synchrotron Radiation Facility (ESRF)

X-ray mirror quality has continuously improved over the past 20 years and manufacturers are now able to provide long mirrors with slope errors below 0.2 μrad. Nevertheless, these mirrors are mounted on holders or even mechanical benders to adjust their curvature and their intrinsic quality must be preserved from any parasitic deformation such as twist. The most direct method of detecting these deformations is to measure the 3D topography of the optical surface. At the ESRF metrology laboratory, three different stitching systems are under development based on Fizeau sub-aperture measurements. The first one consists of measuring long flat mirrors, the second based on the relative angle determinable stitching interferometry (RADSI) method developed at SPring-8 is aimed primarily at the measurement of short mirrors with strong curvature down to a few meters, and the last, also based on the RADSI method, is dedicated to characterize longer mirrors with intermediate curvature. For each method we will describe the measurement setup and discuss first results obtained. Micro-stitching interferometry is also currently used at the ESRF metrology laboratory. The technique is suitable for measuring deeply curved aspherical profiles and will be illustrated with results from a Kirkpatrick-Baez mirror system for nano-focusing.

Hepatitis E virus sequences in swine related to sequences in humans, The Netherlands

Hepatitis E virus (HEV), a major cause of viral hepatitis in much of the developing world, has recently been detected in swine in North America and Asia, raising concern about potential for zoonotic transmission. To investigate if HEV is commonly present in swine in the Netherlands, pooled stool samples from 115 swine farms and nine individual pigs with diarrhea were assayed by reverse transcription-polymerase chain reaction (RT-PCR) amplification. HEV RNA was detected by RT-PCR and hybridization in 25 (22%) of the pooled specimens, but in none of the individual samples. RT-PCR amplification products of open reading frames 1 and 2 were sequenced, and the results were compared with published sequences of HEV genotypes from humans and swine. HEV strains from swine in the Netherlands were clustered in at least two groups, together with European and American isolates from swine and humans. Our data show that HEV in swine in the Netherlands are genetically closely related to HEV isolates from humans. Although zoonotic transmission has not been proven, these findings suggest that swine may be reservoir hosts of HEV.

Influenza virus matrix protein is the major driving force in virus budding

To get insights into the role played by each of the influenza A virus polypeptides in morphogenesis and virus particle assembly, the generation of virus-like particles (VLPs) has been examined in COS-1 cell cultures expressing, from recombinant plasmids, different combinations of the viral structural proteins. The presence of VLPs was examined biochemically, following centrifugation of the supernatants collected from transfected cells through sucrose cushions and immunoblotting, and by electron-microscopic analysis. It is demonstrated that the matrix (M1) protein is the only viral component which is essential for VLP formation and that the viral ribonucleoproteins are not required for virus particle formation. It is also shown that the M1 protein, when expressed alone, assembles into virus-like budding particles, which are released in the culture medium, and that the recombinant M1 protein accumulates intracellularly, forming tubular structures. All these results are discussed with regard to the roles played by the virus polypeptides during virus assembly.

[Outbreak of gastroenteritis at a home for the aged in Albacete]

BACKGROUND

We describe the investigation of an acute gastroenteritis outbreak with an explosive beginning, probably waterborne, that occurred in an nursing home in Albacete, in November 1999 and affected 104 inmates and 35 employees. The dominant symptoms were diarrhea and vomiting.

METHODS

A case-control study was designed. We carried out a descriptive analysis of facts and crossing of variables with the help of simple tables. A multivariant analysis, by models of logistic regression, was conducted both for the explosive phase and for that of transmission person-to-person.

RESULTS

The attack rate for inmates was 45.8% and for employees, 33.7%. An association was found between the use of the main dining-room of the nursing home and the explosive beginning of the outbreak and between the previous presence of a case-patient in the shared bedrooms and the person-to-person transmission. Norwalk-like virus was isolated from faeces samples of four cases.

CONCLUSIONS

The analysis of the clinical and epidemiological findings as well as the laboratory results proved the implication of a Norwalk-like virus in this outbreak.

Norwalk-like calicivirus genes in farm animals

Viruses closely related to Norwalk-like viruses (NLVs) were recently found in stored stool samples from two calves (United Kingdom and Germany) and four pigs (Japan), sparking discussions about the potential for zoonotic transmission. To investigate if NLVs are commonly present in farm animals, pooled stool samples from 100 pig farms, 48 chicken farms, 43 dairy cow herds, and 75 veal calf farms from the Netherlands were assayed by reverse transcription- polymerase chain reaction amplification, using primers specific for the detection of NLVs from humans. NLV RNA was detected in 33 (44%) of the specimens from veal calf farms and two (2%) specimens from pig farms. Our data show that NLV infections until recently thought to be restricted to humans occur often in calves and sometimes in pigs. While zoonotic transmission has not been proven, these findings suggest that calves and pigs may be reservoir hosts of NLVs.

Efficient formation of influenza virus-like particles: dependence on the expression levels of viral proteins

It has previously been demonstrated in this laboratory that an influenza virus-like chloramphenicol acetyltransferase (CAT) RNA could be expressed in COS-1 cells that synthesized all ten influenza A virus-encoded proteins from recombinant plasmids. It was also shown that supernatant fluids harvested from these cultures contained virus-like particles (VLPs) that could deliver an enclosed CAT RNA to MDCK cells. Here, it is shown that the levels of expression of the reporter gene in the COS-1 and/or MDCK cells can be altered drastically by modifying the concentrations of the recombinant plasmids transfected in the COS-1 cells. Thus, it was observed that overexpression of NS2 reduced CAT expression in COS-1 cells, whereas overexpression of M2 and NS1 proteins dramatically decreased transmission of the CAT RNA to the MDCK cultures. These results are discussed with reference to the roles of these proteins during virus replication. From these experiments, a ratio of transfected plasmids was found that increased the efficiency of the previously described system by 50-100-fold. Under these optimized conditions, it was demonstrated that VLPs can be formed in the absence of neuraminidase expression and that these VLPs remained aggregated to each other and to cell membranes. Moreover, it is shown that CAT RNA transmission was dependent on specific interactions of the ribonucleoprotein complex with other viral structural polypeptides. These data demonstrate the usefulness of this encapsidation-packaging system for the study of different aspects of the influenza virus life-cycle.

Rescue of a synthetic chloramphenicol acetyltransferase RNA into influenza virus-like particles obtained from recombinant plasmids

We have shown previously that COS-1 cells infected with a vaccinia virus recombinant (vTF7-3) which expresses the T7 RNA polymerase gene and then transfected with four pGEM-derived plasmids encoding the influenza A virus core proteins (nucleoprotein, PB1, PB2, and PA polypeptides) can express a synthetic influenza virus-like chloramphenicol [correction of chloramphenical] acetyltransferase (CAT) RNA (I. Mena, S. de la Luna, C. Albo, J. Martín, A. Nieto, J. Ortín, and A. Portela, J. Gen. Virol. 75:2109-2114, 1994). Here we demonstrate that by supplying the vTF7-3-infected cells with plasmids containing cDNAs of all 10 influenza virus-encoded proteins, the transfected CAT RNA can be expressed and rescued into particles that are budded into the supernatant fluids. The released particles can transfer the enclosed CAT RNA to MDCK cultures and resemble true influenza virions in that they require trypsin treatment to deliver the RNA to fresh cells and are neutralized by a monoclonal antibody specific for the influenza A virus hemagglutinin. Moreover, analysis by electron microscopy showed that the culture medium harvested from the transfected cells contained vesicles that could be labeled with an anti-HA monoclonal antibody and that were similar in size and morphology to authentic influenza virus particles. It is also shown that detection of recombinant particles capable of transmitting the CAT RNA does not require expression of the influenza virus nonstructural protein NS1. All of these data indicate that influenza virus-like particles enclosing a synthetic virus-like RNA can be assembled in cells expressing all viral structural components from recombinant plasmids.

Cytoplasmic inclusions of respiratory syncytial virus-infected cells: formation of inclusion bodies in transfected cells that coexpress the nucleoprotein, the phosphoprotein, and the 22K protein

Immunofluorescence staining and immunoelectron microscopy of respiratory syncytial (RS) virus-infected cells revealed the presence of cytoplasmic inclusions that were specifically labeled with monoclonal antibodies directed against the nucleoprotein (NP), the phosphoprotein (P), or the 22K protein. Transient expression of these three proteins with the vaccinia-T7 system, either individually or in different combinations, demonstrated that coexpression of NP and P was sufficient to induce the formation of cytoplasmic inclusions similar to those found in RS virus-infected cells. In addition, the 22K protein was also incorporated to the inclusions when coexpressed with both NP and P proteins. Immunobinding assays revealed the presence of NP-P and NP-22K complexes in extracts of RS virus-infected cells. These complexes were also detected in extracts of transfected cells that coexpressed the corresponding proteins. The implications of these results for the RS virus replicative cycle are discussed.

Leghemoglobin in Lupin Plants (Lupinus albus cv Multolupa)

Leghemoglobin was localized by immunogold techniques in nodules of Lupinus albus cv Multolupa inoculated with Bradyrhizobium sp. (Lupinus) strain ISLU 16. The protein localization was performed in nodules embedded in Spurr's and Araldite epoxy resins and Lowycryl K4M. A very good preservation of both the ultrastructure and antigenicity was obtained with the tissues embedded in Araldite following glutaraldehyde fixation and unpostfixed in osmium tetroxide. Lupin leghemoglobin is a stable and abundant protein which allows a conventional method to be safely used for localization of leghemoglobin. Labeling of leghemoglobin was specifically confined to the cytosol matrix and nuclei. Gold particles were never observed in the peribacteroidal spaces nor in the cytoplasmic organelles of the infected cells. Decrease of leghemoglobin was observed when the plants were grown with 10.7 micromolar and 21.4 micromolar of nitrate.